Structure and Function of a Prostate Cancer Dissemination-Permissive Extracellular Matrix

Purpose: The poor prognosis of metastatic prostate cancer continues to present a major challenge in prostate cancer treatment. The tumor extracellular matrix (ECM) plays an important role in facilitating metastasis. Here, we investigated the structure and function of an ECM that facilitates prostate cancer metastasis by comparing orthotopic tumors that frequently metastasize to poorly metastatic subcutaneous tumors.

Experimental Design: Both tumors were derived from a human prostate cancer PC3 cell line engineered to fluoresce under hypoxia. Second harmonic generation (SHG) microscopy was used to characterize collagen 1 (Col1) fiber patterns in the xenografts as well as in human samples. MRI was used to determine albumin-Gd-diethylenetriaminepenta-acetate (alb-GdDTPA) transport through the ECM using a saturation recovery MR method combined with fast T₁ SNAPSHOT-FLASH imaging. Cancer-associated fibroblasts (CAF) were also quantified in these tumors.

Results: Significant structural and functional differences were identified in the prometastatic orthotopic tumor ECM compared to the less metastatic subcutaneous tumor ECM. The significantly higher number of CAFs in orthotopic tumors may explain the higher Col1 fiber volumes in these tumors. In vivo, alb-GdDTPA pooling was significantly elevated in metastatic orthotopic tumors, consistent with the increased Col1 fibers.

Conclusions: Developing noninvasive MRI indices of macromolecular transport, together with characterization of Col1 fiber patterns and CAFs can assist in stratifying prostate cancers for aggressive treatments or active surveillance. These results highlight the role of CAFs in supporting or creating aggressive cancers, and the importance of depleting CAFs to prevent metastatic dissemination in prostate cancer. Clin Cancer Res; 23(9); 2245–54. ©2016 AACR.

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Dysregulation of Rab37-Mediated Cross-talk between Cancer Cells and Endothelial Cells via Thrombospondin-1 Promotes Tumor Neovasculature and Metastasis

Purpose: Accumulating evidence indicates that factors secreted by cancer epithelial cells shape the tumor microenvironment to promote cancer invasion and metastasis. Recent studies also shed light on alterations of Rab small GTPase–mediated exocytosis in tumorigenesis. However, the mechanisms for Rab-mediated exocytosis in tumor microenvironment remain elusive. We aimed to investigate the interplay between Rab37-mediated exocytosis and tumor microenvironment, focusing on endothelial cell motility and angiogenesis.

Experimental Design: We performed fluorescence IHC for Rab37, thrombospondin-1 (TSP1, an antiangiogenesis factor), and angiogenesis marker CD31 in 183 surgically resected esophageal squamous cell carcinoma (ESCC) patient samples. Cell migration, invasion, angiogenesis, and tumor metastasis were measured.

Results: ESCC patients with low expression of Rab37 or TSP1 significantly correlated with high CD31 expression and were associated with worse progression-free survival. The multivariate Cox regression analysis showed that concordant low expression of both Rab37 and TSP1 was an independent prognostic factor of ESCC patients. Rab37-mediated exocytosis of TSP1 led to the inhibition of neovasculature in vitro and in vivo. Secreted TSP1 from cancer cells with Rab37 exocytic function inhibited the p-FAK/p-paxillin/p-ERK migration signaling in both cancer epithelial cells and their surrounding endothelial cells. Dysfunction of Rab37 or loss of TSP1 abrogated the suppressive effects on angiogenesis and metastasis.

Conclusions: Our findings suggest that Rab37-mediated TSP1 secretion in cancer cells suppresses metastasis and angiogenesis via a cross-talk with endothelial cells and reveal a novel component of the vesicular exocytic machinery in tumor microenvironment and tumor progression. Dysregulation of Rab37/TSP1 axis has clinical implications for prognosis prediction. Clin Cancer Res; 23(9); 2335–45. ©2016 AACR.

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Osimertinib for the Treatment of Metastatic EGFR T790M Mutation-Positive Non-Small Cell Lung Cancer

On November 13, 2015, the FDA granted accelerated approval to osimertinib (TAGRISSO; AstraZeneca), a breakthrough therapy-designated drug for the treatment of patients with metastatic EGFR T790M mutation–positive non–small cell lung cancer, as detected by an FDA-approved test, with progression on or after EGFR tyrosine kinase inhibitor therapy. Approval was based on durable tumor response rates in two single-arm, multicenter trials: the dose extension cohort of a first-in-human trial (FIH; AURA extension; n = 201) and a fixed-dose, activity-estimating trial (AURA2; n = 210). Osimertinib was administered at 80 mg orally once daily. The objective response rates (ORR) per blinded independent committee review were 57% [95% confidence interval (CI), 50–64) in AURA extension and 61% (95% CI, 54–68) in AURA2. Median duration of response (DOR) could not be estimated. Supportive efficacy data from 63 patients in the dose-finding part of the FIH trial demonstrated an ORR of 51% (95% CI, 38–64), with a median DOR of 12.4 months. Common adverse events (AE) evaluated in 411 patients included diarrhea (42%), rash (41%), dry skin (31%), and nail toxicity (25%). Grade 3 to 4 AEs occurred in 28% of patients, and 5.6% discontinued treatment due to AEs. Clin Cancer Res; 23(9); 2131–5. ©2016 AACR.

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Axl Blockade by BGB324 Inhibits BCR-ABL Tyrosine Kinase Inhibitor-Sensitive and -Resistant Chronic Myeloid Leukemia

Purpose: BCR-ABL kinase inhibitors are employed successfully for chronic myeloid leukemia (CML) treatment. However, resistant disease and persistence of BCR-ABL1–independent leukemia stem and progenitor cells (LSPC) remain clinical challenges. The receptor tyrosine kinase Axl can mediate survival and therapy resistance of different cancer cells. We investigated the therapeutic potential of Axl inhibition in CML.

Experimental Design: We used primary cells from patients with CML and TKI-sensitive and -resistant BCR-ABL1⁺ CML cell lines and a novel ponatinib-resistant cell line KCL-22 PonR. We analyzed the effects of genetic and pharmacologic Axl blockade by the small-molecule Axl inhibitor BGB324 in vitro and in vivo. In BCR-ABL1–unmutated cells, we also investigated BGB324 in combination with imatinib.

Results: We demonstrate overexpression of Axl receptor tyrosine kinase in primary cells of patients with CML compared with healthy individuals and a further increase of Axl expression in BCR-ABL TKI-resistant patients. We show that Axl blockage decreased growth of BCR-ABL TKI-sensitive CML cells including CD34⁺ cells and exerts additive effects with imatinib via inhibition of Stat5 activation. BGB324 also inhibits BCR-ABL TKI-resistant cells, including T315I-mutated and ponatinib-resistant primary cells. BGB324 exerted therapeutic effects in BCR-ABL1 T315I-mutated and ponatinib-resistant preclinical mouse models. Notably, BGB324 does not inhibit BCR-ABL1 and consequently inhibits CML independent of BCR-ABL1 mutational status.

Conclusions: Our data show that Axl inhibition has therapeutic potential in BCR-ABL TKI-sensitive as well as -resistant CML and support the need for clinical trials. Clin Cancer Res; 23(9); 2289–300. ©2016 AACR.

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Molecular Pathways: Targeting Protein Tyrosine Phosphatases in Cancer

The aberrant activation of oncogenic signaling pathways is a universal phenomenon in cancer and drives tumorigenesis and malignant transformation. This abnormal activation of signaling pathways in cancer is due to the altered expression of protein kinases and phosphatases. In response to extracellular signals, protein kinases activate downstream signaling pathways through a series of protein phosphorylation events, ultimately producing a signal response. Protein tyrosine phosphatases (PTP) are a family of enzymes that hydrolytically remove phosphate groups from proteins. Initially, PTPs were shown to act as tumor suppressor genes by terminating signal responses through the dephosphorylation of oncogenic kinases. More recently, it has become clear that several PTPs overexpressed in human cancers do not suppress tumor growth; instead, they positively regulate signaling pathways and promote tumor development and progression. In this review, we discuss both types of PTPs: those that have tumor suppressor activities as well as those that act as oncogenes. We also discuss the potential of PTP inhibitors for cancer therapy. Clin Cancer Res; 23(9); 2136–42. ©2017 AACR.

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Highlights of This Issue

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Musashi RNA-Binding Proteins as Cancer Drivers and Novel Therapeutic Targets

Aberrant gene expression that drives human cancer can arise from epigenetic dysregulation. Although much attention has focused on altered activity of transcription factors and chromatin-modulating proteins, proteins that act posttranscriptionally can potently affect expression of oncogenic signaling proteins. The RNA-binding proteins (RBP) Musashi-1 (MSI1) and Musashi-2 (MSI2) are emerging as regulators of multiple critical biological processes relevant to cancer initiation, progression, and drug resistance. Following identification of Musashi as a regulator of progenitor cell identity in Drosophila, the human Musashi proteins were initially linked to control of maintenance of hematopoietic stem cells, then stem cell compartments for additional cell types. More recently, the Musashi proteins were found to be overexpressed and prognostic of outcome in numerous cancer types, including colorectal, lung, and pancreatic cancers; glioblastoma; and several leukemias. MSI1 and MSI2 bind and regulate the mRNA stability and translation of proteins operating in essential oncogenic signaling pathways, including NUMB/Notch, PTEN/mTOR, TGFβ/SMAD3, MYC, cMET, and others. On the basis of these activities, MSI proteins maintain cancer stem cell populations and regulate cancer invasion, metastasis, and development of more aggressive cancer phenotypes, including drug resistance. Although RBPs are viewed as difficult therapeutic targets, initial efforts to develop MSI-specific inhibitors are promising, and RNA interference–based approaches to inhibiting these proteins have had promising outcomes in preclinical studies. In the interim, understanding the function of these translational regulators may yield insight into the relationship between mRNA expression and protein expression in tumors, guiding tumor-profiling analysis. This review provides a current overview of Musashi as a cancer driver and novel therapeutic target. Clin Cancer Res; 23(9); 2143–53. ©2017 AACR.

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Preclinical Evaluation of Chimeric Antigen Receptors Targeting CD70-Expressing Cancers

Purpose: CD70 expression in normal tissues is restricted to activated lymphoid tissues. Targeting CD70 on CD70-expressing tumors could mediate "on-target, off-tumor" toxicity. This study was to evaluate the feasibility and safety of using anti-human CD70 CARs to treat cancer patients whose tumors express CD70.

Experimental Design: Seven anti-human CD70 CARs with binding moieties from human CD27 combined with CD3-zeta and different costimulatory domains from CD28 and/or 41BB were constructed. In vitro functionality of these receptors was compared and in vivo treatment efficacy was evaluated in a xenograft mouse model. A homologous, all murine anti-CD70 CAR model was also used to assess treatment-related toxicities.

Results: The CAR consisting of the extracellular binding portion of CD27 fused with 41BB and CD3-zeta (trCD27-41BB-zeta) conferred the highest IFN production against CD70-expressing tumors in vitro, and NSG mice bearing established CD70-expressing human tumors could be cured by human lymphocytes transduced with this CAR. In the murine CD27-CD3-zeta CAR model, significant reduction of established tumors and prolonged survival were achieved using CAR-transduced splenocytes in a dose-dependent manner. Host preirradiation enhanced treatment efficacy but increased treatment-related toxicities such as transient weight loss and hematopoetic suppression. The treatment did not appear to block adaptive host immune responses.

Conclusions: Preclinical testing supports the safety and efficacy of a CD27-containing CAR targeting CD70-expressing tumors. Clin Cancer Res; 23(9); 2267–76. ©2016 AACR.

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Long-term Follow-up of Treatment with Ibrutinib and Rituximab in Patients with High-Risk Chronic Lymphocytic Leukemia

Background: Ibrutinib is an active therapy with an acceptable safety profile for patients with chronic lymphocytic leukemia (CLL), including high-risk patients with del17p or with TP53 mutations. Ibrutinib is broadly indicated for the treatment of patients with CLL and specifically including those with 17p deletion. The optimal use of ibrutinib in combination with other agents remains controversial.

Experimental Design: We report the long-term outcome [median follow-up of 47 months (range, 36–51 months)] of 40 patients with high-risk CLL, treated on the first ibrutinib combination trial with rituximab (IR). The majority of patients (36/40) were previously treated.

Results: Median age was 65 years, and 21 patients (52%) had 17p deletion. Median duration on treatment was 41 months (range, 2–51 months), and median number of treatment cycles was 42 (range, 2–49). Overall response rate was 95%, and 9 patients (23%) attained a complete remission. Twenty-one patients discontinued treatment, 10 due to disease progression, 9 for other causes, and 2 due to stem cell transplantation; the remaining 19 patients continue on ibrutinib. Median progression-free survival for all patients was 45 months, which was significantly shorter in the subgroup of patients with del17p (n = 21, 32.3 months, P = 0.02). Fourteen patients (35%) died, five from progressive disease, five from infections, and four from other causes. Median overall survival has not been reached.

Conclusions: IR combination therapy leads to durable remissions in high-risk CLL; the possible benefit from the addition of rituximab is currently explored in a randomized trial. Clin Cancer Res; 23(9); 2154–8. ©2016 AACR.

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The Dual Syk/JAK Inhibitor Cerdulatinib Antagonizes B-cell Receptor and Microenvironmental Signaling in Chronic Lymphocytic Leukemia

Purpose: B-cell receptor (BCR)–associated kinase inhibitors, such as ibrutinib, have revolutionized the treatment of chronic lymphocytic leukemia (CLL). However, these agents are not curative, and resistance is already emerging in a proportion of patients. IL4, expressed in CLL lymph nodes, can augment BCR signaling and reduce the effectiveness of BCR kinase inhibitors. Therefore, simultaneous targeting of the IL4- and BCR signaling pathways by cerdulatinib, a novel dual Syk/JAK inhibitor currently in clinical trials (NCT01994382), may improve treatment responses in patients.

Experimental Design: PBMCs from patients with CLL were treated in vitro with cerdulatinib alone or in combination with venetoclax. Cell death, chemokine, and cell signaling assay were performed and analyzed by flow cytometry, immunoblotting, q-PCR, and ELISA as indicated.

Results: At concentrations achievable in patients, cerdulatinib inhibited BCR- and IL4-induced downstream signaling in CLL cells using multiple readouts and prevented anti-IgM- and nurse-like cell (NLC)–mediated CCL3/CCL4 production. Cerdulatinib induced apoptosis of CLL cells, in a time- and concentration-dependent manner, and particularly in IGHV-unmutated samples with greater BCR signaling capacity and response to IL4, or samples expressing higher levels of sIgM, CD49d⁺, or ZAP70⁺. Cerdulatinib overcame anti-IgM, IL4/CD40L, or NLC-mediated protection by preventing upregulation of MCL-1 and BCL-X_L; however, BCL-2 expression was unaffected. Furthermore, in samples treated with IL4/CD40L, cerdulatinib synergized with venetoclax in vitro to induce greater apoptosis than either drug alone.

Conclusions: Cerdulatinib is a promising therapeutic for the treatment of CLL either alone or in combination with venetoclax, with the potential to target critical survival pathways in this currently incurable disease. Clin Cancer Res; 23(9); 2313–24. ©2016 AACR.

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FCGR Polymorphisms Influence Response to IL2 in Metastatic Renal Cell Carcinoma

Purpose: Fc-gamma receptors (FCGRs) are expressed on immune cells, bind to antibodies, and trigger antibody-induced cell-mediated antitumor responses when tumor-reactive antibodies are present. The affinity of the FCGR/antibody interaction is variable and dependent upon FCGR polymorphisms. Prior studies of patients with cancer treated with immunotherapy indicate that FCGR polymorphisms can influence antitumor response for certain immunotherapies that act via therapeutically administered mAbs or via endogenous tumor-reactive antibodies induced from tumor antigen vaccines. The previously published "SELECT" trial of high-dose aldesleukin (HD-IL2) for metastatic renal cell carcinoma resulted in an objective response rate of 25%. We evaluated the patients in this SELECT trial to determine whether higher-affinity FCGR polymorphisms are associated with outcome.

Experimental Design: SNPs in FCGR2A, FCGR3A, and FCGR2C were analyzed, individually and in combination, for associations between genotype and clinical outcome.

Results: When higher-affinity genotypes for FCGR2A, FCGR3A, and FCGR2C were considered together, they were associated with significantly increased tumor shrinkage and prolonged survival in response to HD-IL2.

Conclusions: Although associations of higher-affinity FCGR genotype with clinical outcome have been demonstrated with mAb therapy and with idiotype vaccines, to our knowledge, this is the first study to show associations of FCGR genotypes with outcome following HD-IL2 treatment. We hypothesize that endogenous antitumor antibodies may engage immune cells through their FCGRs, and HD-IL2 may enhance antibody-induced tumor destruction, or antibody-enhanced tumor antigen presentation, via augmented activation of innate or adaptive immune responses; this FCGR-mediated immune activity would be augmented through immunologically favorable FCGRs. Clin Cancer Res; 23(9); 2159–68. ©2016 AACR.

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lncRNAs as Novel Indicators of Patients' Prognosis in Stage I Epithelial Ovarian Cancer: A Retrospective and Multicentric Study

Purpose: Stage I epithelial ovarian cancer (EOC) represents about 10% of all EOCs and is characterized by good prognosis with fewer than 20% of patients relapsing. As it occurs less frequently than advanced-stage EOC, its molecular features have not been thoroughly investigated. We have demonstrated that in stage I EOC miR-200c-3p can predict patients' outcome. In the present study, we analyzed the expression of long non-coding RNAs (lncRNA) to enable potential definition of a non-coding transcriptional signature with prognostic relevance for stage I EOC.

Experimental Design: 202 snap-frozen stage I EOC tumor biopsies, 47 of which relapsed, were gathered together from three independent tumor tissue collections and subdivided into a training set (n = 73) and a validation set (n = 129). Median follow up was 9 years. LncRNAs' expression profiles were correlated in univariate and multivariate analysis with overall survival (OS) and progression-free survival (PFS).

Results: The expression of lnc-SERTAD2-3, lnc-SOX4-1, lnc-HRCT1-1, and PVT1 was associated in univariate and multivariate analyses with relapse and poor outcome in both training and validation sets (P < 0.001). Using the expression profiles of PVT1, lnc-SERTAD2-3, and miR-200c-3p simultaneously, it was possible to stratify patients into high and low risk. The OS for high- and low-risk individuals are 36 and 123 months, respectively (OR, 15.55; 95% confidence interval, 3.81–63.36).

Conclusions: We have identified a non-coding transcriptional signature predictor of survival and biomarker of relapse for stage I EOC. Clin Cancer Res; 23(9); 2356–66. ©2016 AACR.

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Neoadjuvant Enzalutamide Prior to Prostatectomy

Purpose: Prostate cancer is dependent on androgen receptor (AR) activation. Optimal AR antagonism may effectively cytoreduce local disease and suppress or eliminate micrometastases. We evaluated neoadjuvant therapy prior to prostatectomy with the potent AR antagonist enzalutamide (enza) either alone or in combination with dutasteride (dut) and leuprolide (enza/dut/luteinizing hormone-releasing hormone analogues [LHRHa]).

Experimental Design: Forty-eight of 52 men with intermediate or high-risk localized prostate cancer proceeded to prostatectomy after neoadjuvant enzalutamide or enza/dut/LHRHa for 6 months. We assessed pathologic complete response (pCR), minimal residual disease (MRD; ≤3 mm maximum diameter of residual disease), residual cancer burden (RCB), and expression of PSA and serum and tissue androgen concentrations. We compared the proportion of patients with pCR in each treatment arm with a historical control rate of 5%, based on previous reports of flutamide with LHRHa.

Results: In the enzalutamide arm, none of the 25 patients achieved pCR or MRD. In the enza/dut/LHRHa arm, one of 23 patients (4.3%) achieved pCR and 3 of 23 (13.0%) achieved MRD. Median RCB was higher in the enzalutamide arm than in the enza/dut/LHRHa arm (0.41 cm³ vs. 0.06 cm³, respectively). Tissue testosterone and dihydrotestosterone levels correlated with RCB. No adverse events leading to study drug discontinuation were reported.

Conclusions: Combination therapy with enza/dut/LHRHa resulted in pCR and MRD rates comparable with historical controls. Evidence of continued AR activity in residual tumor suggests that AR signaling may contribute to survival. Strategies to more effectively ablate AR activity are warranted to determine whether more substantial antitumor effects are observed. Clin Cancer Res; 23(9); 2169–76. ©2016 AACR.

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Biological and Clinical Relevance of Associated Genomic Alterations in MYD88 L265P and non-L265P-Mutated Diffuse Large B-Cell Lymphoma: Analysis of 361 Cases

Purpose: MYD88 mutations, notably the recurrent gain-of-function L265P variant, are a distinguishing feature of activated B-cell like (ABC) diffuse large B-cell lymphoma (DLBCL), leading to constitutive NFB pathway activation. The aim of this study was to examine the distinct genomic profiles of MYD88-mutant DLBCL, notably according to the presence of the L265P or other non-L265P MYD88 variants.

Experimental Design: A cohort of 361 DLBCL cases (94 MYD88 mutant and 267 MYD88 wild-type) was submitted to next-generation sequencing (NGS) focusing on 34 genes to analyze associated mutations and copy number variations, as well as gene expression profiling, and clinical and prognostic analyses.

Results: Importantly, we highlighted different genomic profiles for MYD88 L265P and MYD88 non-L265P–mutant DLBCL, shedding light on their divergent backgrounds. Clustering analysis also segregated subgroups according to associated genetic alterations among patients with the same MYD88 mutation. We showed that associated CD79B and MYD88 L265P mutations act synergistically to increase NFB pathway activation, although the majority of MYD88 L265P–mutant cases harbors downstream NFB alterations, which can predict BTK inhibitor resistance. Finally, although the MYD88 L265P variant was not an independent prognostic factor in ABC DLBCL, associated CD79B mutations significantly improved the survival of MYD88 L265P–mutant ABC DLBCL in our cohort.

Conclusions: This study highlights the relative heterogeneity of MYD88-mutant DLBCL, adding to the field's knowledge of the theranostic importance of MYD88 mutations, but also of associated alterations, emphasizing the usefulness of genomic profiling to best stratify patients for targeted therapy. Clin Cancer Res; 23(9); 2232–44. ©2016 AACR.

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The Landscape of Viral Expression Reveals Clinically Relevant Viruses with Potential Capability of Promoting Malignancy in Lower-Grade Glioma

Purpose: RNA sequencing (RNA-seq) has recently proved to be effective for revealing novel virus–tumor associations. To get a thorough investigation of virus–glioma associations, we screened viruses in gliomas with RNA-seq data from the Chinese Glioma Genome Atlas project.

Experimental Design: In total, 325 samples were enrolled into this study. Reads that failed to map to the human genome were aligned to viral genomes and screened for potential virus-derived transcripts. For quantification, VPKM was calculated according to mapped reads weighted by genome sizes and sequencing depth.

Results: We observed that viruses tended to concertedly express in a certain subgroup of patients. Survival analysis revealed that individuals who were infected with Simian virus 40 (SV40) or woolly monkey sarcoma virus (WMSV) had a significantly shorter overall survival than those uninfected. A multivariate Cox proportional hazards model, taking clinical and molecular factors into account, was applied to assess the prognostic value of SV40 and WMSV. Both SV40 and WMSV were independent prognostic factors for predicting patient's survival in lower-grade gliomas. Subsequent gene analysis demonstrated that SV40 was correlated with regulation of transcription, whereas WMSV was correlated with cell-cycle phase, which indicated frequent proliferation of tumor cells.

Conclusions: RNA-seq was sufficient to identify virus infection in glioma samples. SV40 and WMSV were identified to be prognostic markers for patients with lower-grade gliomas and showed potential values for targeting therapy. Clin Cancer Res; 23(9); 2177–85. ©2016 AACR.

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Multiplex Genome Editing to Generate Universal CAR T Cells Resistant to PD1 Inhibition

Purpose: Using gene-disrupted allogeneic T cells as universal effector cells provides an alternative and potentially improves current chimeric antigen receptor (CAR) T-cell therapy against cancers and infectious diseases.

Experimental Design: The CRISPR/Cas9 system has recently emerged as a simple and efficient way for multiplex genome engineering. By combining lentiviral delivery of CAR and electro-transfer of Cas9 mRNA and gRNAs targeting endogenous TCR, β-2 microglobulin (B2M) and PD1 simultaneously, to generate gene-disrupted allogeneic CAR T cells deficient of TCR, HLA class I molecule and PD1.

Results: The CRISPR gene–edited CAR T cells showed potent antitumor activities, both in vitro and in animal models and were as potent as non-gene–edited CAR T cells. In addition, the TCR and HLA class I double deficient T cells had reduced alloreactivity and did not cause graft-versus-host disease. Finally, simultaneous triple genome editing by adding the disruption of PD1 led to enhanced in vivo antitumor activity of the gene-disrupted CAR T cells.

Conclusions: Gene-disrupted allogeneic CAR and TCR T cells could provide an alternative as a universal donor to autologous T cells, which carry difficulties and high production costs. Gene-disrupted CAR and TCR T cells with disabled checkpoint molecules may be potent effector cells against cancers and infectious diseases. Clin Cancer Res; 23(9); 2255–66. ©2016 AACR.

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Biomarker and Tumor Responses of Oral Cavity Squamous Cell Carcinoma to Trametinib: A Phase II Neoadjuvant Window-of-Opportunity Clinical Trial

Purpose: Ras/MEK/ERK pathway activation is common in oral cavity squamous cell carcinoma (OCSCC). We performed a neoadjuvant (preoperative) trial to determine the biomarker and tumor response of OCSCC to MEK inhibition with trametinib.

Experimental Design: Patients with stage II–IV OCSCC received trametinib (2 mg/day, minimum 7 days) prior to surgery. Primary tumor specimens were obtained before and after trametinib to evaluate immunohistochemical staining for p-ERK1/2 and CD44, the primary endpoint. Secondary endpoints included changes in clinical tumor measurements and metabolic activity [maximum standardized uptake values (SUV_max) by F-18 fluorodeoxyglucose positron emission tomography/CT), and in tumor downstaging. Drug-related adverse events (AE) and surgical/wound complications were evaluated.

Results: Of 20 enrolled patients, 17 (85%) completed the study. Three patients withdrew because of either trametinib-related (n = 2: nausea, duodenal perforation) or unrelated (n = 1: constipation) AEs. The most common AE was rash (9/20 patients, 45%). Seventeen patients underwent surgery. No unexpected surgical/wound complications occurred. Evaluable matched pre- and posttrametinib specimens were available in 15 (88%) of these patients. Reduction in p-ERK1/2 and CD44 expression occurred in 5 (33%) and 2 (13%) patients, respectively. Clinical tumor response by modified World Health Organization criteria was observed in 11 of 17 (65%) evaluable patients (median 46% decrease, range 14%–74%). Partial metabolic response (≥25% reduction in SUV_max) was observed in 6 of 13 (46%) evaluable patients (median 25% decrease, range 6%–52%). Clinical-to-pathologic tumor downstaging occurred in 9 of 17 (53%) evaluable patients.

Conclusions: Trametinib resulted in significant reduction in Ras/MEK/ERK pathway activation and in clinical and metabolic tumor responses in patients with OCSCC. Clin Cancer Res; 23(9); 2186–94. ©2016 AACR.

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Cytokine-Induced Killer Cells Kill Chemo-surviving Melanoma Cancer Stem Cells

Purpose: The MHC-unrestricted activity of cytokine-induced killer (CIK) cells against chemo-surviving melanoma cancer stem cells (mCSC) was explored, as CSCs are considered responsible for chemoresistance and relapses.

Experimental Design: Putative mCSCs were visualized by engineering patient-derived melanoma cells (MC) with a lentiviral vector encoding eGFP under expression control by stemness gene promoter oct4. Their stemness potential was confirmed in vivo by limiting dilution assays. We explored the sensitivity of eGFP⁺ mCSCs to chemotherapy (CHT), BRAF inhibitor (BRAFi) or CIK cells, as single agents or in sequence, in vitro. First, we treated MCs in vitro with fotemustine or dabrafenib (BRAF-mutated cases); then, surviving MCs, enriched in mCSCs, were challenged with autologous CIK cells. CIK cell activity against chemoresistant mCSCs was confirmed in vivo in two distinct immunodeficient murine models.

Results: We visualized eGFP⁺ mCSCs (14% ± 2.1%) in 11 MCs. The tumorigenic precursor rate in vivo was higher within eGFP⁺ MCs (1/42) compared with the eGFP^– counterpart (1/4,870). In vitro mCSCs were relatively resistant to CHT and BRAFi, but killed by CIK cells (n = 11, 8/11 autologous), with specific lysis ranging from 95% [effector:tumor ratio (E:T), 40:1] to 20% (E:T 1:3). In vivo infusion of autologous CIK cells into mice bearing xenografts from three distinct melanomas demonstrated significant tumor responses involving CHT-spared eGFP⁺ mCSCs (P = 0.001). Sequential CHT–immunotherapy treatment retained antitumor activity (n = 12, P = 0.001) reducing mCSC rates (P = 0.01).

Conclusions: These findings are the first demonstration that immunotherapy with CIK cells is active against autologous mCSCs surviving CHT or BRAFi. An experimental platform for mCSC study and rationale for CIK cells in melanoma clinical study is provided. Clin Cancer Res; 23(9); 2277–88. ©2016 AACR.

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Impact of TP53 Mutations on Outcome in EGFR-Mutated Patients Treated with First-Line Tyrosine Kinase Inhibitors

Purpose: To analyze the impact of TP53 mutations on response to first-line tyrosine kinase inhibitors (TKI) in patients with EGFR-mutated non–small cell lung cancer (NSCLC).

Experimental Design: 136 EGFR-mutated NSCLC patients receiving first-line TKIs were analyzed. TP53 mutations were evaluated in 123 patients in relation to disease control rate (DCR), objective response rate (ORR), progression-free survival (PFS), and overall survival (OS).

Results: TP53 mutations were observed in 37 (30.1%), 10 (27.0%), 6 (16.2%), 9 (24.3%), and 12 (32.4%) patients in exons 5, 6, 7, and 8, respectively. DCR was 70% in TP53-mutated patients compared with 88% in TP53-wild type (wt) patients [relative risk, RR, of disease progression: 3.17 (95% CI, 1.21–8.48), P = 0.019]. In particular, a 42% DCR was observed in patients with TP53 exon 8 mutation versus 87% in exon 8 wt patients [RR of disease progression 9.6 (2.71–36.63), P < 0.001]. Shorter median PFS and OS were observed in patients with TP53 exon 8 mutations compared with others (4.2 vs. 12.5, P = 0.058, and 16.2 vs. 32.3, P = 0.114, respectively); these differences became significant in the subgroup with EGFR exon 19 deletion (4.2 vs. 16.8, P < 0.001, and 7.6 vs. not reached, P = 0.006, respectively), HR 6.99 (95% CI, 2.34–20.87, P < 0.001) and HR 4.75 (95% CI, 1.38–16.29, P = 0.013), respectively.

Conclusions: TP53 mutations, especially exon 8 mutations, reduce responsiveness to TKIs and worsen prognosis in EGFR-mutated NSCLC patients, mainly those carrying exon 19 deletions. Clin Cancer Res; 23(9); 2195–202. ©2016 AACR.

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Characterization of an Abiraterone Ultraresponsive Phenotype in Castration-Resistant Prostate Cancer Patient-Derived Xenografts

Purpose: To identify the molecular signature associated with abiraterone acetate (AA) response and mechanisms underlying AA resistance in castration-resistant prostate cancer patient-derived xenografts (PDXs).

Experimental Design: SCID mice bearing LuCaP 136CR, 77CR, 96CR, and 35CR PDXs were treated with AA. Tumor volume and prostate-specific antigen were monitored, and tumors were harvested 7 days after treatment or at end of study for gene expression and immunohistochemical studies.

Results: Three phenotypic groups were observed based on AA response. An ultraresponsive phenotype was identified in LuCaP 136CR with significant inhibition of tumor progression and increased survival, intermediate responders LuCaP 77CR and LuCaP 96CR with a modest tumor inhibition and survival benefit, and LuCaP 35CR with minimal tumor inhibition and no survival benefit upon AA treatment. We identified a molecular signature of secreted proteins associated with the AA ultraresponsive phenotype. Upon resistance, AA ultraresponder LuCaP 136CR displayed reduced androgen receptor (AR) signaling and sustainably low nuclear glucocorticoid receptor (nGR) localization, accompanied by steroid metabolism alteration and epithelial–mesenchymal transition phenotype enrichment with increased expression of NF-B–regulated genes; intermediate and minimal responders maintained sustained AR signaling and increased tumoral nGR localization.

Conclusions: We identified a molecular signature of secreted proteins associated with AA ultraresponsiveness and sustained AR/GR signaling upon AA resistance in intermediate or minimal responders. These data will inform development of noninvasive biomarkers predicting AA response and suggest that further inhibition along the AR/GR signaling axis may be effective only in AA-resistant patients who are intermediate or minimal responders. These findings require verification in prospective clinical trials. Clin Cancer Res; 23(9); 2301–12. ©2016 AACR.

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Structure and Function of a Prostate Cancer Dissemination-Permissive Extracellular Matrix

Purpose: The poor prognosis of metastatic prostate cancer continues to present a major challenge in prostate cancer treatment. The tumor extracellular matrix (ECM) plays an important role in facilitating metastasis. Here, we investigated the structure and function of an ECM that facilitates prostate cancer metastasis by comparing orthotopic tumors that frequently metastasize to poorly metastatic subcutaneous tumors.

Experimental Design: Both tumors were derived from a human prostate cancer PC3 cell line engineered to fluoresce under hypoxia. Second harmonic generation (SHG) microscopy was used to characterize collagen 1 (Col1) fiber patterns in the xenografts as well as in human samples. MRI was used to determine albumin-Gd-diethylenetriaminepenta-acetate (alb-GdDTPA) transport through the ECM using a saturation recovery MR method combined with fast T₁ SNAPSHOT-FLASH imaging. Cancer-associated fibroblasts (CAF) were also quantified in these tumors.

Results: Significant structural and functional differences were identified in the prometastatic orthotopic tumor ECM compared to the less metastatic subcutaneous tumor ECM. The significantly higher number of CAFs in orthotopic tumors may explain the higher Col1 fiber volumes in these tumors. In vivo, alb-GdDTPA pooling was significantly elevated in metastatic orthotopic tumors, consistent with the increased Col1 fibers.

Conclusions: Developing noninvasive MRI indices of macromolecular transport, together with characterization of Col1 fiber patterns and CAFs can assist in stratifying prostate cancers for aggressive treatments or active surveillance. These results highlight the role of CAFs in supporting or creating aggressive cancers, and the importance of depleting CAFs to prevent metastatic dissemination in prostate cancer. Clin Cancer Res; 23(9); 2245–54. ©2016 AACR.

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Dysregulation of Rab37-Mediated Cross-talk between Cancer Cells and Endothelial Cells via Thrombospondin-1 Promotes Tumor Neovasculature and Metastasis

Purpose: Accumulating evidence indicates that factors secreted by cancer epithelial cells shape the tumor microenvironment to promote cancer invasion and metastasis. Recent studies also shed light on alterations of Rab small GTPase–mediated exocytosis in tumorigenesis. However, the mechanisms for Rab-mediated exocytosis in tumor microenvironment remain elusive. We aimed to investigate the interplay between Rab37-mediated exocytosis and tumor microenvironment, focusing on endothelial cell motility and angiogenesis.

Experimental Design: We performed fluorescence IHC for Rab37, thrombospondin-1 (TSP1, an antiangiogenesis factor), and angiogenesis marker CD31 in 183 surgically resected esophageal squamous cell carcinoma (ESCC) patient samples. Cell migration, invasion, angiogenesis, and tumor metastasis were measured.

Results: ESCC patients with low expression of Rab37 or TSP1 significantly correlated with high CD31 expression and were associated with worse progression-free survival. The multivariate Cox regression analysis showed that concordant low expression of both Rab37 and TSP1 was an independent prognostic factor of ESCC patients. Rab37-mediated exocytosis of TSP1 led to the inhibition of neovasculature in vitro and in vivo. Secreted TSP1 from cancer cells with Rab37 exocytic function inhibited the p-FAK/p-paxillin/p-ERK migration signaling in both cancer epithelial cells and their surrounding endothelial cells. Dysfunction of Rab37 or loss of TSP1 abrogated the suppressive effects on angiogenesis and metastasis.

Conclusions: Our findings suggest that Rab37-mediated TSP1 secretion in cancer cells suppresses metastasis and angiogenesis via a cross-talk with endothelial cells and reveal a novel component of the vesicular exocytic machinery in tumor microenvironment and tumor progression. Dysregulation of Rab37/TSP1 axis has clinical implications for prognosis prediction. Clin Cancer Res; 23(9); 2335–45. ©2016 AACR.

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Osimertinib for the Treatment of Metastatic EGFR T790M Mutation-Positive Non-Small Cell Lung Cancer

On November 13, 2015, the FDA granted accelerated approval to osimertinib (TAGRISSO; AstraZeneca), a breakthrough therapy-designated drug for the treatment of patients with metastatic EGFR T790M mutation–positive non–small cell lung cancer, as detected by an FDA-approved test, with progression on or after EGFR tyrosine kinase inhibitor therapy. Approval was based on durable tumor response rates in two single-arm, multicenter trials: the dose extension cohort of a first-in-human trial (FIH; AURA extension; n = 201) and a fixed-dose, activity-estimating trial (AURA2; n = 210). Osimertinib was administered at 80 mg orally once daily. The objective response rates (ORR) per blinded independent committee review were 57% [95% confidence interval (CI), 50–64) in AURA extension and 61% (95% CI, 54–68) in AURA2. Median duration of response (DOR) could not be estimated. Supportive efficacy data from 63 patients in the dose-finding part of the FIH trial demonstrated an ORR of 51% (95% CI, 38–64), with a median DOR of 12.4 months. Common adverse events (AE) evaluated in 411 patients included diarrhea (42%), rash (41%), dry skin (31%), and nail toxicity (25%). Grade 3 to 4 AEs occurred in 28% of patients, and 5.6% discontinued treatment due to AEs. Clin Cancer Res; 23(9); 2131–5. ©2016 AACR.

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Axl Blockade by BGB324 Inhibits BCR-ABL Tyrosine Kinase Inhibitor-Sensitive and -Resistant Chronic Myeloid Leukemia

Purpose: BCR-ABL kinase inhibitors are employed successfully for chronic myeloid leukemia (CML) treatment. However, resistant disease and persistence of BCR-ABL1–independent leukemia stem and progenitor cells (LSPC) remain clinical challenges. The receptor tyrosine kinase Axl can mediate survival and therapy resistance of different cancer cells. We investigated the therapeutic potential of Axl inhibition in CML.

Experimental Design: We used primary cells from patients with CML and TKI-sensitive and -resistant BCR-ABL1⁺ CML cell lines and a novel ponatinib-resistant cell line KCL-22 PonR. We analyzed the effects of genetic and pharmacologic Axl blockade by the small-molecule Axl inhibitor BGB324 in vitro and in vivo. In BCR-ABL1–unmutated cells, we also investigated BGB324 in combination with imatinib.

Results: We demonstrate overexpression of Axl receptor tyrosine kinase in primary cells of patients with CML compared with healthy individuals and a further increase of Axl expression in BCR-ABL TKI-resistant patients. We show that Axl blockage decreased growth of BCR-ABL TKI-sensitive CML cells including CD34⁺ cells and exerts additive effects with imatinib via inhibition of Stat5 activation. BGB324 also inhibits BCR-ABL TKI-resistant cells, including T315I-mutated and ponatinib-resistant primary cells. BGB324 exerted therapeutic effects in BCR-ABL1 T315I-mutated and ponatinib-resistant preclinical mouse models. Notably, BGB324 does not inhibit BCR-ABL1 and consequently inhibits CML independent of BCR-ABL1 mutational status.

Conclusions: Our data show that Axl inhibition has therapeutic potential in BCR-ABL TKI-sensitive as well as -resistant CML and support the need for clinical trials. Clin Cancer Res; 23(9); 2289–300. ©2016 AACR.

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Molecular Pathways: Targeting Protein Tyrosine Phosphatases in Cancer

The aberrant activation of oncogenic signaling pathways is a universal phenomenon in cancer and drives tumorigenesis and malignant transformation. This abnormal activation of signaling pathways in cancer is due to the altered expression of protein kinases and phosphatases. In response to extracellular signals, protein kinases activate downstream signaling pathways through a series of protein phosphorylation events, ultimately producing a signal response. Protein tyrosine phosphatases (PTP) are a family of enzymes that hydrolytically remove phosphate groups from proteins. Initially, PTPs were shown to act as tumor suppressor genes by terminating signal responses through the dephosphorylation of oncogenic kinases. More recently, it has become clear that several PTPs overexpressed in human cancers do not suppress tumor growth; instead, they positively regulate signaling pathways and promote tumor development and progression. In this review, we discuss both types of PTPs: those that have tumor suppressor activities as well as those that act as oncogenes. We also discuss the potential of PTP inhibitors for cancer therapy. Clin Cancer Res; 23(9); 2136–42. ©2017 AACR.

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Highlights of This Issue

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Musashi RNA-Binding Proteins as Cancer Drivers and Novel Therapeutic Targets

Aberrant gene expression that drives human cancer can arise from epigenetic dysregulation. Although much attention has focused on altered activity of transcription factors and chromatin-modulating proteins, proteins that act posttranscriptionally can potently affect expression of oncogenic signaling proteins. The RNA-binding proteins (RBP) Musashi-1 (MSI1) and Musashi-2 (MSI2) are emerging as regulators of multiple critical biological processes relevant to cancer initiation, progression, and drug resistance. Following identification of Musashi as a regulator of progenitor cell identity in Drosophila, the human Musashi proteins were initially linked to control of maintenance of hematopoietic stem cells, then stem cell compartments for additional cell types. More recently, the Musashi proteins were found to be overexpressed and prognostic of outcome in numerous cancer types, including colorectal, lung, and pancreatic cancers; glioblastoma; and several leukemias. MSI1 and MSI2 bind and regulate the mRNA stability and translation of proteins operating in essential oncogenic signaling pathways, including NUMB/Notch, PTEN/mTOR, TGFβ/SMAD3, MYC, cMET, and others. On the basis of these activities, MSI proteins maintain cancer stem cell populations and regulate cancer invasion, metastasis, and development of more aggressive cancer phenotypes, including drug resistance. Although RBPs are viewed as difficult therapeutic targets, initial efforts to develop MSI-specific inhibitors are promising, and RNA interference–based approaches to inhibiting these proteins have had promising outcomes in preclinical studies. In the interim, understanding the function of these translational regulators may yield insight into the relationship between mRNA expression and protein expression in tumors, guiding tumor-profiling analysis. This review provides a current overview of Musashi as a cancer driver and novel therapeutic target. Clin Cancer Res; 23(9); 2143–53. ©2017 AACR.

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Preclinical Evaluation of Chimeric Antigen Receptors Targeting CD70-Expressing Cancers

Purpose: CD70 expression in normal tissues is restricted to activated lymphoid tissues. Targeting CD70 on CD70-expressing tumors could mediate "on-target, off-tumor" toxicity. This study was to evaluate the feasibility and safety of using anti-human CD70 CARs to treat cancer patients whose tumors express CD70.

Experimental Design: Seven anti-human CD70 CARs with binding moieties from human CD27 combined with CD3-zeta and different costimulatory domains from CD28 and/or 41BB were constructed. In vitro functionality of these receptors was compared and in vivo treatment efficacy was evaluated in a xenograft mouse model. A homologous, all murine anti-CD70 CAR model was also used to assess treatment-related toxicities.

Results: The CAR consisting of the extracellular binding portion of CD27 fused with 41BB and CD3-zeta (trCD27-41BB-zeta) conferred the highest IFN production against CD70-expressing tumors in vitro, and NSG mice bearing established CD70-expressing human tumors could be cured by human lymphocytes transduced with this CAR. In the murine CD27-CD3-zeta CAR model, significant reduction of established tumors and prolonged survival were achieved using CAR-transduced splenocytes in a dose-dependent manner. Host preirradiation enhanced treatment efficacy but increased treatment-related toxicities such as transient weight loss and hematopoetic suppression. The treatment did not appear to block adaptive host immune responses.

Conclusions: Preclinical testing supports the safety and efficacy of a CD27-containing CAR targeting CD70-expressing tumors. Clin Cancer Res; 23(9); 2267–76. ©2016 AACR.

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Long-term Follow-up of Treatment with Ibrutinib and Rituximab in Patients with High-Risk Chronic Lymphocytic Leukemia

Background: Ibrutinib is an active therapy with an acceptable safety profile for patients with chronic lymphocytic leukemia (CLL), including high-risk patients with del17p or with TP53 mutations. Ibrutinib is broadly indicated for the treatment of patients with CLL and specifically including those with 17p deletion. The optimal use of ibrutinib in combination with other agents remains controversial.

Experimental Design: We report the long-term outcome [median follow-up of 47 months (range, 36–51 months)] of 40 patients with high-risk CLL, treated on the first ibrutinib combination trial with rituximab (IR). The majority of patients (36/40) were previously treated.

Results: Median age was 65 years, and 21 patients (52%) had 17p deletion. Median duration on treatment was 41 months (range, 2–51 months), and median number of treatment cycles was 42 (range, 2–49). Overall response rate was 95%, and 9 patients (23%) attained a complete remission. Twenty-one patients discontinued treatment, 10 due to disease progression, 9 for other causes, and 2 due to stem cell transplantation; the remaining 19 patients continue on ibrutinib. Median progression-free survival for all patients was 45 months, which was significantly shorter in the subgroup of patients with del17p (n = 21, 32.3 months, P = 0.02). Fourteen patients (35%) died, five from progressive disease, five from infections, and four from other causes. Median overall survival has not been reached.

Conclusions: IR combination therapy leads to durable remissions in high-risk CLL; the possible benefit from the addition of rituximab is currently explored in a randomized trial. Clin Cancer Res; 23(9); 2154–8. ©2016 AACR.

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The Dual Syk/JAK Inhibitor Cerdulatinib Antagonizes B-cell Receptor and Microenvironmental Signaling in Chronic Lymphocytic Leukemia

Purpose: B-cell receptor (BCR)–associated kinase inhibitors, such as ibrutinib, have revolutionized the treatment of chronic lymphocytic leukemia (CLL). However, these agents are not curative, and resistance is already emerging in a proportion of patients. IL4, expressed in CLL lymph nodes, can augment BCR signaling and reduce the effectiveness of BCR kinase inhibitors. Therefore, simultaneous targeting of the IL4- and BCR signaling pathways by cerdulatinib, a novel dual Syk/JAK inhibitor currently in clinical trials (NCT01994382), may improve treatment responses in patients.

Experimental Design: PBMCs from patients with CLL were treated in vitro with cerdulatinib alone or in combination with venetoclax. Cell death, chemokine, and cell signaling assay were performed and analyzed by flow cytometry, immunoblotting, q-PCR, and ELISA as indicated.

Results: At concentrations achievable in patients, cerdulatinib inhibited BCR- and IL4-induced downstream signaling in CLL cells using multiple readouts and prevented anti-IgM- and nurse-like cell (NLC)–mediated CCL3/CCL4 production. Cerdulatinib induced apoptosis of CLL cells, in a time- and concentration-dependent manner, and particularly in IGHV-unmutated samples with greater BCR signaling capacity and response to IL4, or samples expressing higher levels of sIgM, CD49d⁺, or ZAP70⁺. Cerdulatinib overcame anti-IgM, IL4/CD40L, or NLC-mediated protection by preventing upregulation of MCL-1 and BCL-X_L; however, BCL-2 expression was unaffected. Furthermore, in samples treated with IL4/CD40L, cerdulatinib synergized with venetoclax in vitro to induce greater apoptosis than either drug alone.

Conclusions: Cerdulatinib is a promising therapeutic for the treatment of CLL either alone or in combination with venetoclax, with the potential to target critical survival pathways in this currently incurable disease. Clin Cancer Res; 23(9); 2313–24. ©2016 AACR.

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FCGR Polymorphisms Influence Response to IL2 in Metastatic Renal Cell Carcinoma

Purpose: Fc-gamma receptors (FCGRs) are expressed on immune cells, bind to antibodies, and trigger antibody-induced cell-mediated antitumor responses when tumor-reactive antibodies are present. The affinity of the FCGR/antibody interaction is variable and dependent upon FCGR polymorphisms. Prior studies of patients with cancer treated with immunotherapy indicate that FCGR polymorphisms can influence antitumor response for certain immunotherapies that act via therapeutically administered mAbs or via endogenous tumor-reactive antibodies induced from tumor antigen vaccines. The previously published "SELECT" trial of high-dose aldesleukin (HD-IL2) for metastatic renal cell carcinoma resulted in an objective response rate of 25%. We evaluated the patients in this SELECT trial to determine whether higher-affinity FCGR polymorphisms are associated with outcome.

Experimental Design: SNPs in FCGR2A, FCGR3A, and FCGR2C were analyzed, individually and in combination, for associations between genotype and clinical outcome.

Results: When higher-affinity genotypes for FCGR2A, FCGR3A, and FCGR2C were considered together, they were associated with significantly increased tumor shrinkage and prolonged survival in response to HD-IL2.

Conclusions: Although associations of higher-affinity FCGR genotype with clinical outcome have been demonstrated with mAb therapy and with idiotype vaccines, to our knowledge, this is the first study to show associations of FCGR genotypes with outcome following HD-IL2 treatment. We hypothesize that endogenous antitumor antibodies may engage immune cells through their FCGRs, and HD-IL2 may enhance antibody-induced tumor destruction, or antibody-enhanced tumor antigen presentation, via augmented activation of innate or adaptive immune responses; this FCGR-mediated immune activity would be augmented through immunologically favorable FCGRs. Clin Cancer Res; 23(9); 2159–68. ©2016 AACR.

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lncRNAs as Novel Indicators of Patients' Prognosis in Stage I Epithelial Ovarian Cancer: A Retrospective and Multicentric Study

Purpose: Stage I epithelial ovarian cancer (EOC) represents about 10% of all EOCs and is characterized by good prognosis with fewer than 20% of patients relapsing. As it occurs less frequently than advanced-stage EOC, its molecular features have not been thoroughly investigated. We have demonstrated that in stage I EOC miR-200c-3p can predict patients' outcome. In the present study, we analyzed the expression of long non-coding RNAs (lncRNA) to enable potential definition of a non-coding transcriptional signature with prognostic relevance for stage I EOC.

Experimental Design: 202 snap-frozen stage I EOC tumor biopsies, 47 of which relapsed, were gathered together from three independent tumor tissue collections and subdivided into a training set (n = 73) and a validation set (n = 129). Median follow up was 9 years. LncRNAs' expression profiles were correlated in univariate and multivariate analysis with overall survival (OS) and progression-free survival (PFS).

Results: The expression of lnc-SERTAD2-3, lnc-SOX4-1, lnc-HRCT1-1, and PVT1 was associated in univariate and multivariate analyses with relapse and poor outcome in both training and validation sets (P < 0.001). Using the expression profiles of PVT1, lnc-SERTAD2-3, and miR-200c-3p simultaneously, it was possible to stratify patients into high and low risk. The OS for high- and low-risk individuals are 36 and 123 months, respectively (OR, 15.55; 95% confidence interval, 3.81–63.36).

Conclusions: We have identified a non-coding transcriptional signature predictor of survival and biomarker of relapse for stage I EOC. Clin Cancer Res; 23(9); 2356–66. ©2016 AACR.

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Neoadjuvant Enzalutamide Prior to Prostatectomy

Purpose: Prostate cancer is dependent on androgen receptor (AR) activation. Optimal AR antagonism may effectively cytoreduce local disease and suppress or eliminate micrometastases. We evaluated neoadjuvant therapy prior to prostatectomy with the potent AR antagonist enzalutamide (enza) either alone or in combination with dutasteride (dut) and leuprolide (enza/dut/luteinizing hormone-releasing hormone analogues [LHRHa]).

Experimental Design: Forty-eight of 52 men with intermediate or high-risk localized prostate cancer proceeded to prostatectomy after neoadjuvant enzalutamide or enza/dut/LHRHa for 6 months. We assessed pathologic complete response (pCR), minimal residual disease (MRD; ≤3 mm maximum diameter of residual disease), residual cancer burden (RCB), and expression of PSA and serum and tissue androgen concentrations. We compared the proportion of patients with pCR in each treatment arm with a historical control rate of 5%, based on previous reports of flutamide with LHRHa.

Results: In the enzalutamide arm, none of the 25 patients achieved pCR or MRD. In the enza/dut/LHRHa arm, one of 23 patients (4.3%) achieved pCR and 3 of 23 (13.0%) achieved MRD. Median RCB was higher in the enzalutamide arm than in the enza/dut/LHRHa arm (0.41 cm³ vs. 0.06 cm³, respectively). Tissue testosterone and dihydrotestosterone levels correlated with RCB. No adverse events leading to study drug discontinuation were reported.

Conclusions: Combination therapy with enza/dut/LHRHa resulted in pCR and MRD rates comparable with historical controls. Evidence of continued AR activity in residual tumor suggests that AR signaling may contribute to survival. Strategies to more effectively ablate AR activity are warranted to determine whether more substantial antitumor effects are observed. Clin Cancer Res; 23(9); 2169–76. ©2016 AACR.

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Biological and Clinical Relevance of Associated Genomic Alterations in MYD88 L265P and non-L265P-Mutated Diffuse Large B-Cell Lymphoma: Analysis of 361 Cases

Purpose: MYD88 mutations, notably the recurrent gain-of-function L265P variant, are a distinguishing feature of activated B-cell like (ABC) diffuse large B-cell lymphoma (DLBCL), leading to constitutive NFB pathway activation. The aim of this study was to examine the distinct genomic profiles of MYD88-mutant DLBCL, notably according to the presence of the L265P or other non-L265P MYD88 variants.

Experimental Design: A cohort of 361 DLBCL cases (94 MYD88 mutant and 267 MYD88 wild-type) was submitted to next-generation sequencing (NGS) focusing on 34 genes to analyze associated mutations and copy number variations, as well as gene expression profiling, and clinical and prognostic analyses.

Results: Importantly, we highlighted different genomic profiles for MYD88 L265P and MYD88 non-L265P–mutant DLBCL, shedding light on their divergent backgrounds. Clustering analysis also segregated subgroups according to associated genetic alterations among patients with the same MYD88 mutation. We showed that associated CD79B and MYD88 L265P mutations act synergistically to increase NFB pathway activation, although the majority of MYD88 L265P–mutant cases harbors downstream NFB alterations, which can predict BTK inhibitor resistance. Finally, although the MYD88 L265P variant was not an independent prognostic factor in ABC DLBCL, associated CD79B mutations significantly improved the survival of MYD88 L265P–mutant ABC DLBCL in our cohort.

Conclusions: This study highlights the relative heterogeneity of MYD88-mutant DLBCL, adding to the field's knowledge of the theranostic importance of MYD88 mutations, but also of associated alterations, emphasizing the usefulness of genomic profiling to best stratify patients for targeted therapy. Clin Cancer Res; 23(9); 2232–44. ©2016 AACR.

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The Landscape of Viral Expression Reveals Clinically Relevant Viruses with Potential Capability of Promoting Malignancy in Lower-Grade Glioma

Purpose: RNA sequencing (RNA-seq) has recently proved to be effective for revealing novel virus–tumor associations. To get a thorough investigation of virus–glioma associations, we screened viruses in gliomas with RNA-seq data from the Chinese Glioma Genome Atlas project.

Experimental Design: In total, 325 samples were enrolled into this study. Reads that failed to map to the human genome were aligned to viral genomes and screened for potential virus-derived transcripts. For quantification, VPKM was calculated according to mapped reads weighted by genome sizes and sequencing depth.

Results: We observed that viruses tended to concertedly express in a certain subgroup of patients. Survival analysis revealed that individuals who were infected with Simian virus 40 (SV40) or woolly monkey sarcoma virus (WMSV) had a significantly shorter overall survival than those uninfected. A multivariate Cox proportional hazards model, taking clinical and molecular factors into account, was applied to assess the prognostic value of SV40 and WMSV. Both SV40 and WMSV were independent prognostic factors for predicting patient's survival in lower-grade gliomas. Subsequent gene analysis demonstrated that SV40 was correlated with regulation of transcription, whereas WMSV was correlated with cell-cycle phase, which indicated frequent proliferation of tumor cells.

Conclusions: RNA-seq was sufficient to identify virus infection in glioma samples. SV40 and WMSV were identified to be prognostic markers for patients with lower-grade gliomas and showed potential values for targeting therapy. Clin Cancer Res; 23(9); 2177–85. ©2016 AACR.

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Multiplex Genome Editing to Generate Universal CAR T Cells Resistant to PD1 Inhibition

Purpose: Using gene-disrupted allogeneic T cells as universal effector cells provides an alternative and potentially improves current chimeric antigen receptor (CAR) T-cell therapy against cancers and infectious diseases.

Experimental Design: The CRISPR/Cas9 system has recently emerged as a simple and efficient way for multiplex genome engineering. By combining lentiviral delivery of CAR and electro-transfer of Cas9 mRNA and gRNAs targeting endogenous TCR, β-2 microglobulin (B2M) and PD1 simultaneously, to generate gene-disrupted allogeneic CAR T cells deficient of TCR, HLA class I molecule and PD1.

Results: The CRISPR gene–edited CAR T cells showed potent antitumor activities, both in vitro and in animal models and were as potent as non-gene–edited CAR T cells. In addition, the TCR and HLA class I double deficient T cells had reduced alloreactivity and did not cause graft-versus-host disease. Finally, simultaneous triple genome editing by adding the disruption of PD1 led to enhanced in vivo antitumor activity of the gene-disrupted CAR T cells.

Conclusions: Gene-disrupted allogeneic CAR and TCR T cells could provide an alternative as a universal donor to autologous T cells, which carry difficulties and high production costs. Gene-disrupted CAR and TCR T cells with disabled checkpoint molecules may be potent effector cells against cancers and infectious diseases. Clin Cancer Res; 23(9); 2255–66. ©2016 AACR.

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Biomarker and Tumor Responses of Oral Cavity Squamous Cell Carcinoma to Trametinib: A Phase II Neoadjuvant Window-of-Opportunity Clinical Trial

Purpose: Ras/MEK/ERK pathway activation is common in oral cavity squamous cell carcinoma (OCSCC). We performed a neoadjuvant (preoperative) trial to determine the biomarker and tumor response of OCSCC to MEK inhibition with trametinib.

Experimental Design: Patients with stage II–IV OCSCC received trametinib (2 mg/day, minimum 7 days) prior to surgery. Primary tumor specimens were obtained before and after trametinib to evaluate immunohistochemical staining for p-ERK1/2 and CD44, the primary endpoint. Secondary endpoints included changes in clinical tumor measurements and metabolic activity [maximum standardized uptake values (SUV_max) by F-18 fluorodeoxyglucose positron emission tomography/CT), and in tumor downstaging. Drug-related adverse events (AE) and surgical/wound complications were evaluated.

Results: Of 20 enrolled patients, 17 (85%) completed the study. Three patients withdrew because of either trametinib-related (n = 2: nausea, duodenal perforation) or unrelated (n = 1: constipation) AEs. The most common AE was rash (9/20 patients, 45%). Seventeen patients underwent surgery. No unexpected surgical/wound complications occurred. Evaluable matched pre- and posttrametinib specimens were available in 15 (88%) of these patients. Reduction in p-ERK1/2 and CD44 expression occurred in 5 (33%) and 2 (13%) patients, respectively. Clinical tumor response by modified World Health Organization criteria was observed in 11 of 17 (65%) evaluable patients (median 46% decrease, range 14%–74%). Partial metabolic response (≥25% reduction in SUV_max) was observed in 6 of 13 (46%) evaluable patients (median 25% decrease, range 6%–52%). Clinical-to-pathologic tumor downstaging occurred in 9 of 17 (53%) evaluable patients.

Conclusions: Trametinib resulted in significant reduction in Ras/MEK/ERK pathway activation and in clinical and metabolic tumor responses in patients with OCSCC. Clin Cancer Res; 23(9); 2186–94. ©2016 AACR.

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Cytokine-Induced Killer Cells Kill Chemo-surviving Melanoma Cancer Stem Cells

Purpose: The MHC-unrestricted activity of cytokine-induced killer (CIK) cells against chemo-surviving melanoma cancer stem cells (mCSC) was explored, as CSCs are considered responsible for chemoresistance and relapses.

Experimental Design: Putative mCSCs were visualized by engineering patient-derived melanoma cells (MC) with a lentiviral vector encoding eGFP under expression control by stemness gene promoter oct4. Their stemness potential was confirmed in vivo by limiting dilution assays. We explored the sensitivity of eGFP⁺ mCSCs to chemotherapy (CHT), BRAF inhibitor (BRAFi) or CIK cells, as single agents or in sequence, in vitro. First, we treated MCs in vitro with fotemustine or dabrafenib (BRAF-mutated cases); then, surviving MCs, enriched in mCSCs, were challenged with autologous CIK cells. CIK cell activity against chemoresistant mCSCs was confirmed in vivo in two distinct immunodeficient murine models.

Results: We visualized eGFP⁺ mCSCs (14% ± 2.1%) in 11 MCs. The tumorigenic precursor rate in vivo was higher within eGFP⁺ MCs (1/42) compared with the eGFP^– counterpart (1/4,870). In vitro mCSCs were relatively resistant to CHT and BRAFi, but killed by CIK cells (n = 11, 8/11 autologous), with specific lysis ranging from 95% [effector:tumor ratio (E:T), 40:1] to 20% (E:T 1:3). In vivo infusion of autologous CIK cells into mice bearing xenografts from three distinct melanomas demonstrated significant tumor responses involving CHT-spared eGFP⁺ mCSCs (P = 0.001). Sequential CHT–immunotherapy treatment retained antitumor activity (n = 12, P = 0.001) reducing mCSC rates (P = 0.01).

Conclusions: These findings are the first demonstration that immunotherapy with CIK cells is active against autologous mCSCs surviving CHT or BRAFi. An experimental platform for mCSC study and rationale for CIK cells in melanoma clinical study is provided. Clin Cancer Res; 23(9); 2277–88. ©2016 AACR.

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Impact of TP53 Mutations on Outcome in EGFR-Mutated Patients Treated with First-Line Tyrosine Kinase Inhibitors

Purpose: To analyze the impact of TP53 mutations on response to first-line tyrosine kinase inhibitors (TKI) in patients with EGFR-mutated non–small cell lung cancer (NSCLC).

Experimental Design: 136 EGFR-mutated NSCLC patients receiving first-line TKIs were analyzed. TP53 mutations were evaluated in 123 patients in relation to disease control rate (DCR), objective response rate (ORR), progression-free survival (PFS), and overall survival (OS).

Results: TP53 mutations were observed in 37 (30.1%), 10 (27.0%), 6 (16.2%), 9 (24.3%), and 12 (32.4%) patients in exons 5, 6, 7, and 8, respectively. DCR was 70% in TP53-mutated patients compared with 88% in TP53-wild type (wt) patients [relative risk, RR, of disease progression: 3.17 (95% CI, 1.21–8.48), P = 0.019]. In particular, a 42% DCR was observed in patients with TP53 exon 8 mutation versus 87% in exon 8 wt patients [RR of disease progression 9.6 (2.71–36.63), P < 0.001]. Shorter median PFS and OS were observed in patients with TP53 exon 8 mutations compared with others (4.2 vs. 12.5, P = 0.058, and 16.2 vs. 32.3, P = 0.114, respectively); these differences became significant in the subgroup with EGFR exon 19 deletion (4.2 vs. 16.8, P < 0.001, and 7.6 vs. not reached, P = 0.006, respectively), HR 6.99 (95% CI, 2.34–20.87, P < 0.001) and HR 4.75 (95% CI, 1.38–16.29, P = 0.013), respectively.

Conclusions: TP53 mutations, especially exon 8 mutations, reduce responsiveness to TKIs and worsen prognosis in EGFR-mutated NSCLC patients, mainly those carrying exon 19 deletions. Clin Cancer Res; 23(9); 2195–202. ©2016 AACR.

http://ift.tt/2oWVmmK

Characterization of an Abiraterone Ultraresponsive Phenotype in Castration-Resistant Prostate Cancer Patient-Derived Xenografts

Purpose: To identify the molecular signature associated with abiraterone acetate (AA) response and mechanisms underlying AA resistance in castration-resistant prostate cancer patient-derived xenografts (PDXs).

Experimental Design: SCID mice bearing LuCaP 136CR, 77CR, 96CR, and 35CR PDXs were treated with AA. Tumor volume and prostate-specific antigen were monitored, and tumors were harvested 7 days after treatment or at end of study for gene expression and immunohistochemical studies.

Results: Three phenotypic groups were observed based on AA response. An ultraresponsive phenotype was identified in LuCaP 136CR with significant inhibition of tumor progression and increased survival, intermediate responders LuCaP 77CR and LuCaP 96CR with a modest tumor inhibition and survival benefit, and LuCaP 35CR with minimal tumor inhibition and no survival benefit upon AA treatment. We identified a molecular signature of secreted proteins associated with the AA ultraresponsive phenotype. Upon resistance, AA ultraresponder LuCaP 136CR displayed reduced androgen receptor (AR) signaling and sustainably low nuclear glucocorticoid receptor (nGR) localization, accompanied by steroid metabolism alteration and epithelial–mesenchymal transition phenotype enrichment with increased expression of NF-B–regulated genes; intermediate and minimal responders maintained sustained AR signaling and increased tumoral nGR localization.

Conclusions: We identified a molecular signature of secreted proteins associated with AA ultraresponsiveness and sustained AR/GR signaling upon AA resistance in intermediate or minimal responders. These data will inform development of noninvasive biomarkers predicting AA response and suggest that further inhibition along the AR/GR signaling axis may be effective only in AA-resistant patients who are intermediate or minimal responders. These findings require verification in prospective clinical trials. Clin Cancer Res; 23(9); 2301–12. ©2016 AACR.

http://ift.tt/2pyH8ww

An Anti-CD47 Antibody Is Effective in Pediatric Brain Tumor Models [Brain Tumors]

The anti-CD47 antibody Hu5F9-G4 selectively kills tumor cells in pediatric brain tumor PDX models.

http://ift.tt/2oZsQlz

Gut Microbes May Up PD-1 Inhibitor Response [News in Brief]

Confirming the results of animal studies, new research shows that the composition of patients' microbiome influences their response to checkpoint inhibitors. Patients with melanoma who benefit from PD-1 inhibitors carry a greater variety of species and higher numbers of microbes in the Clostridiales group. Increased abundance of certain bacteria in this group also correlated with higher numbers of CD8+ T cells in patients' tumors.

http://ift.tt/2plPJ5b

Profiling Response, Resistance to Immunotherapy [News in Brief]

In a longitudinal analysis of patients with metastatic melanoma who received sequential therapies targeting CTLA-4, then PD-1 upon disease progression, researchers have discovered that high copy-number loss in recurrent regions of the tumor genome is associated with resistance to immune checkpoint blockade.

http://ift.tt/2oZG5CM

AG-221, a First-in-Class Therapy Targeting Acute Myeloid Leukemia Harboring Oncogenic IDH2 Mutations [Research Articles]

Somatic gain-of-function mutations in isocitrate dehydrogenases (IDH) 1 and 2 are found in multiple hematologic and solid tumors, leading to accumulation of the oncometabolite (R)-2-hydroxyglutarate (2HG). 2HG competitively inhibits α-ketoglutarate–dependent dioxygenases, including histone demethylases and methylcytosine dioxygenases of the TET family, causing epigenetic dysregulation and a block in cellular differentiation. In vitro studies have provided proof of concept for mutant IDH inhibition as a therapeutic approach. We report the discovery and characterization of AG-221, an orally available, selective, potent inhibitor of the mutant IDH2 enzyme. AG-221 suppressed 2HG production and induced cellular differentiation in primary human IDH2 mutation–positive acute myeloid leukemia (AML) cells ex vivo and in xenograft mouse models. AG-221 also provided a statistically significant survival benefit in an aggressive IDH2^R140Q-mutant AML xenograft mouse model. These findings supported initiation of the ongoing clinical trials of AG-221 in patients with IDH2 mutation–positive advanced hematologic malignancies.

Significance: Mutations in IDH1/2 are identified in approximately 20% of patients with AML and contribute to leukemia via a block in hematopoietic cell differentiation. We have shown that the targeted inhibitor AG-221 suppresses the mutant IDH2 enzyme in multiple preclinical models and induces differentiation of malignant blasts, supporting its clinical development. Cancer Discov; 7(5); 478–93. ©2017 AACR.

See related commentary by Thomas and Majeti, p. 459.

See related article by Shih et al., p. 494.

This article is highlighted in the In This Issue feature, p. 443

http://ift.tt/2plOTFv

Ribociclib Approved for Advanced Breast Cancer [News in Brief]

The FDA has approved ribociclib combined with aromatase inhibitor therapy for women with metastatic HR-positive, HER2-negative breast cancer. It is the second CDK 4/6 inhibitor approved for these patients, behind palbociclib; a third is under investigation.

http://ift.tt/2oZJfpV

MK-8242 Is Active in Patients with p53 Wild-Type Advanced Solid Tumors [Clinical Trials]

The MDM2 inhibitor MK-8242 is tolerable in patients with liposarcoma and other advanced solid tumors.

http://ift.tt/2plQGu4

Monitoring Resistance, Recurrence in NSCLC [News in Brief]

Two studies indicate the importance of serial biopsies in monitoring patients with non–small cell lung cancer. In one, heterogeneous resistance mechanisms to EGFR-targeted therapy were observed, often varying between biopsies for individual patients. In another, circulating tumor cells detected recurrence 6 months earlier, on average, than conventional imaging.

http://ift.tt/2oZJd1h

PI3K Signaling Regulates ER Activity via KMT2D in ER+ Breast Cancer [Breast Cancer]

Targeting PI3Kα enhances KMT2D methyltransferase activity to promote ER-mediated transcription.

http://ift.tt/2plTyHw

Budget Cuts Would Harm Research and Patients [News in Brief]

Cancer researchers and administrators have attacked the Trump administration's proposal to cut the NIH budget by nearly 20%. Researchers say that the reduction could hamstring efforts to expand immunotherapies and other novel treatments to more patients. They also worry that the proposal could drive away biomedical scientists and shift top-notch research to other countries.

http://ift.tt/2oZEkFF

Pembrolizumab Approved for Hodgkin Lymphoma [News in Brief]

The FDA has approved pembrolizumab for adults and children with classical Hodgkin lymphoma whose disease is refractory to or has relapsed after at least three prior therapies. The approval marks the first time that a PD-1 inhibitor has been indicated for blood cancers—and for children.

http://ift.tt/2plLzds

CRISPR Meets CAR T-cell Therapy [News in Brief]

Using CRISPR/Cas9 technology, researchers have devised a method to deliver a CAR gene to a specific locus, TRAC, in T cells. This targeted approach yielded therapeutic cells that were more potent even at low doses; in a mouse model of acute lymphoblastic leukemia, they outperformed CAR T cells created with a randomly integrating retroviral vector.

http://ift.tt/2oZJUYH

Converging on RAS [News in Depth]

Biologists at the Frederick National Laboratory for Cancer Research have teamed up with computer scientists and physicists at the Department of Energy to tackle the problem of "undruggable" RAS. The goal is to obtain a precise understanding of how RAS is activated by interactions with the plasma membrane; this will be illuminated through supercomputer simulations that build on structural and biochemical studies of RAS.

http://ift.tt/2plI6vG

A Different Path for Harnessing TRAIL [News in Brief]

Two studies show that the apoptosis-inducing protein TRAIL also induces release of cytokines that promote tumor growth. TRAIL triggers formation of a signaling complex that activates NF-B. Loss of one component of the signaling complex, the adaptor protein FADD, reduces the number of lung tumors in mice.

http://ift.tt/2pm9RUP

T-cell Bispecific Antibodies Suppress Multiple Myeloma [Multiple Myeloma]

T-cell bispecific antibodies (TCB) targeting BCMA or FcRH5 induce T cell–mediated myeloma cell death.

http://ift.tt/2oZJ3Hd

Immunotherapy Beats Chemo for Bladder Cancer [News in Brief]

Patients with advanced urothelial carcinoma live 3 months longer, on average, when given pembrolizumab as a second-line treatment instead of chemotherapy. The finding is based on data from the first phase III trial to test an immunotherapeutic in these patients, which could lead to another label indication for the PD-1 inhibitor.

http://ift.tt/2plA8CO

Peptidomimetic Inhibitors Target ERG Gene Fusions in Prostate Cancer [Prostate Cancer]

ERG inhibitory peptides promote ERG degradation and suppress the growth of TMPRSS2–ERG⁺ tumors.

http://ift.tt/2oZsCed

ALKBH5 Drives FOXM1 Expression to Promote Brain Tumor Stem Cell Growth [Brain Tumors]

The mRNA demethylase ALKBH5 promotes glioblastoma stem cell growth and tumorigenesis.

http://ift.tt/2plNw9H

Optimizing Next-Generation AML Therapy: Activity of Mutant IDH2 Inhibitor AG-221 in Preclinical Models [In the Spotlight]

Summary: AG-221 or enasidenib is a first-in-class selective inhibitor of mutated isocitrate dehydrogenase 2 (IDH2) with early demonstrated clinical efficacy in acute myeloid leukemia as a single agent, yet with persistence of mutant IDH2 clones. Two articles in this issue of Cancer Discovery provide further insight into the biological activity of AG-221 in promoting differentiation of IDH2-mutant cells and reversing aberrant DNA methylation over time, and demonstrating preclinical activity in combination with a targeted FLT3 kinase inhibitor to eliminate IDH2-mutant clones. Cancer Discov; 7(5); 459–61. ©2017 AACR.

See related article by Yen et al., p. 478.

See related article by Shih et al., p. 494.

http://ift.tt/2oZJ1z5

HER2+ Tumor Molecular Subtypes Predict Response to Dual HER2 Blockade [Clinical Trials]

Trastuzumab plus lapatinib achieves the highest response rates in HER2-enriched HER2⁺ breast tumors.

http://ift.tt/2plMaMv

BCL6 Antagonizes NOTCH2 to Maintain Survival of Human Follicular Lymphoma Cells [Research Articles]

Although the BCL6 transcriptional repressor is frequently expressed in human follicular lymphomas (FL), its biological role in this disease remains unknown. Herein, we comprehensively identify the set of gene promoters directly targeted by BCL6 in primary human FLs. We noted that BCL6 binds and represses NOTCH2 and NOTCH pathway genes. Moreover, BCL6 and NOTCH2 pathway gene expression is inversely correlated in FL. Notably, BCL6 upregulation is associated with repression of NOTCH2 and its target genes in primary human and murine germinal center (GC) cells. Repression of NOTCH2 is an essential function of BCL6 in FL and GC B cells because inducible expression of Notch2 abrogated GC formation in mice and killed FL cells. Indeed, BCL6-targeting compounds or gene silencing leads to the induction of NOTCH2 activity and compromises survival of FL cells, whereas NOTCH2 depletion or pathway antagonists rescue FL cells from such effects. Moreover, BCL6 inhibitors induced NOTCH2 expression and suppressed growth of human FL xenografts in vivo and primary human FL specimens ex vivo. These studies suggest that established FLs are thus dependent on BCL6 through its suppression of NOTCH2.

Significance: We show that human FLs are dependent on BCL6, and primary human FLs can be killed using specific BCL6 inhibitors. Integrative genomics and functional studies of BCL6 in primary FL cells point toward a novel mechanism whereby BCL6 repression of NOTCH2 drives the survival and growth of FL cells as well as GC B cells, which are the FL cell of origin. Cancer Discov; 7(5); 506–21. ©2017 AACR.

This article is highlighted in the In This Issue feature, p. 443

http://ift.tt/2oZs342

An Anti-CD47 Antibody Is Effective in Pediatric Brain Tumor Models [Brain Tumors]

The anti-CD47 antibody Hu5F9-G4 selectively kills tumor cells in pediatric brain tumor PDX models.

from Cancer via ola Kala on Inoreader http://ift.tt/2oZsQlz
via IFTTT

Gut Microbes May Up PD-1 Inhibitor Response [News in Brief]

Confirming the results of animal studies, new research shows that the composition of patients' microbiome influences their response to checkpoint inhibitors. Patients with melanoma who benefit from PD-1 inhibitors carry a greater variety of species and higher numbers of microbes in the Clostridiales group. Increased abundance of certain bacteria in this group also correlated with higher numbers of CD8+ T cells in patients' tumors.

from Cancer via ola Kala on Inoreader http://ift.tt/2plPJ5b
via IFTTT

Profiling Response, Resistance to Immunotherapy [News in Brief]

In a longitudinal analysis of patients with metastatic melanoma who received sequential therapies targeting CTLA-4, then PD-1 upon disease progression, researchers have discovered that high copy-number loss in recurrent regions of the tumor genome is associated with resistance to immune checkpoint blockade.

from Cancer via ola Kala on Inoreader http://ift.tt/2oZG5CM
via IFTTT

AG-221, a First-in-Class Therapy Targeting Acute Myeloid Leukemia Harboring Oncogenic IDH2 Mutations [Research Articles]

Somatic gain-of-function mutations in isocitrate dehydrogenases (IDH) 1 and 2 are found in multiple hematologic and solid tumors, leading to accumulation of the oncometabolite (R)-2-hydroxyglutarate (2HG). 2HG competitively inhibits α-ketoglutarate–dependent dioxygenases, including histone demethylases and methylcytosine dioxygenases of the TET family, causing epigenetic dysregulation and a block in cellular differentiation. In vitro studies have provided proof of concept for mutant IDH inhibition as a therapeutic approach. We report the discovery and characterization of AG-221, an orally available, selective, potent inhibitor of the mutant IDH2 enzyme. AG-221 suppressed 2HG production and induced cellular differentiation in primary human IDH2 mutation–positive acute myeloid leukemia (AML) cells ex vivo and in xenograft mouse models. AG-221 also provided a statistically significant survival benefit in an aggressive IDH2^R140Q-mutant AML xenograft mouse model. These findings supported initiation of the ongoing clinical trials of AG-221 in patients with IDH2 mutation–positive advanced hematologic malignancies.

Significance: Mutations in IDH1/2 are identified in approximately 20% of patients with AML and contribute to leukemia via a block in hematopoietic cell differentiation. We have shown that the targeted inhibitor AG-221 suppresses the mutant IDH2 enzyme in multiple preclinical models and induces differentiation of malignant blasts, supporting its clinical development. Cancer Discov; 7(5); 478–93. ©2017 AACR.

See related commentary by Thomas and Majeti, p. 459.

See related article by Shih et al., p. 494.

This article is highlighted in the In This Issue feature, p. 443

from Cancer via ola Kala on Inoreader http://ift.tt/2plOTFv
via IFTTT

Ribociclib Approved for Advanced Breast Cancer [News in Brief]

The FDA has approved ribociclib combined with aromatase inhibitor therapy for women with metastatic HR-positive, HER2-negative breast cancer. It is the second CDK 4/6 inhibitor approved for these patients, behind palbociclib; a third is under investigation.

from Cancer via ola Kala on Inoreader http://ift.tt/2oZJfpV
via IFTTT

MK-8242 Is Active in Patients with p53 Wild-Type Advanced Solid Tumors [Clinical Trials]

The MDM2 inhibitor MK-8242 is tolerable in patients with liposarcoma and other advanced solid tumors.

from Cancer via ola Kala on Inoreader http://ift.tt/2plQGu4
via IFTTT

Monitoring Resistance, Recurrence in NSCLC [News in Brief]

Two studies indicate the importance of serial biopsies in monitoring patients with non–small cell lung cancer. In one, heterogeneous resistance mechanisms to EGFR-targeted therapy were observed, often varying between biopsies for individual patients. In another, circulating tumor cells detected recurrence 6 months earlier, on average, than conventional imaging.

from Cancer via ola Kala on Inoreader http://ift.tt/2oZJd1h
via IFTTT

PI3K Signaling Regulates ER Activity via KMT2D in ER+ Breast Cancer [Breast Cancer]

Targeting PI3Kα enhances KMT2D methyltransferase activity to promote ER-mediated transcription.

from Cancer via ola Kala on Inoreader http://ift.tt/2plTyHw
via IFTTT

Budget Cuts Would Harm Research and Patients [News in Brief]

Cancer researchers and administrators have attacked the Trump administration's proposal to cut the NIH budget by nearly 20%. Researchers say that the reduction could hamstring efforts to expand immunotherapies and other novel treatments to more patients. They also worry that the proposal could drive away biomedical scientists and shift top-notch research to other countries.

from Cancer via ola Kala on Inoreader http://ift.tt/2oZEkFF
via IFTTT

Pembrolizumab Approved for Hodgkin Lymphoma [News in Brief]

The FDA has approved pembrolizumab for adults and children with classical Hodgkin lymphoma whose disease is refractory to or has relapsed after at least three prior therapies. The approval marks the first time that a PD-1 inhibitor has been indicated for blood cancers—and for children.

from Cancer via ola Kala on Inoreader http://ift.tt/2plLzds
via IFTTT

CRISPR Meets CAR T-cell Therapy [News in Brief]

Using CRISPR/Cas9 technology, researchers have devised a method to deliver a CAR gene to a specific locus, TRAC, in T cells. This targeted approach yielded therapeutic cells that were more potent even at low doses; in a mouse model of acute lymphoblastic leukemia, they outperformed CAR T cells created with a randomly integrating retroviral vector.

from Cancer via ola Kala on Inoreader http://ift.tt/2oZJUYH
via IFTTT

Converging on RAS [News in Depth]

Biologists at the Frederick National Laboratory for Cancer Research have teamed up with computer scientists and physicists at the Department of Energy to tackle the problem of "undruggable" RAS. The goal is to obtain a precise understanding of how RAS is activated by interactions with the plasma membrane; this will be illuminated through supercomputer simulations that build on structural and biochemical studies of RAS.

from Cancer via ola Kala on Inoreader http://ift.tt/2plI6vG
via IFTTT

A Different Path for Harnessing TRAIL [News in Brief]

Two studies show that the apoptosis-inducing protein TRAIL also induces release of cytokines that promote tumor growth. TRAIL triggers formation of a signaling complex that activates NF-B. Loss of one component of the signaling complex, the adaptor protein FADD, reduces the number of lung tumors in mice.

from Cancer via ola Kala on Inoreader http://ift.tt/2pm9RUP
via IFTTT

T-cell Bispecific Antibodies Suppress Multiple Myeloma [Multiple Myeloma]

T-cell bispecific antibodies (TCB) targeting BCMA or FcRH5 induce T cell–mediated myeloma cell death.

from Cancer via ola Kala on Inoreader http://ift.tt/2oZJ3Hd
via IFTTT

Immunotherapy Beats Chemo for Bladder Cancer [News in Brief]

Patients with advanced urothelial carcinoma live 3 months longer, on average, when given pembrolizumab as a second-line treatment instead of chemotherapy. The finding is based on data from the first phase III trial to test an immunotherapeutic in these patients, which could lead to another label indication for the PD-1 inhibitor.

from Cancer via ola Kala on Inoreader http://ift.tt/2plA8CO
via IFTTT

Peptidomimetic Inhibitors Target ERG Gene Fusions in Prostate Cancer [Prostate Cancer]

ERG inhibitory peptides promote ERG degradation and suppress the growth of TMPRSS2–ERG⁺ tumors.

from Cancer via ola Kala on Inoreader http://ift.tt/2oZsCed
via IFTTT

ALKBH5 Drives FOXM1 Expression to Promote Brain Tumor Stem Cell Growth [Brain Tumors]

The mRNA demethylase ALKBH5 promotes glioblastoma stem cell growth and tumorigenesis.

from Cancer via ola Kala on Inoreader http://ift.tt/2plNw9H
via IFTTT

Optimizing Next-Generation AML Therapy: Activity of Mutant IDH2 Inhibitor AG-221 in Preclinical Models [In the Spotlight]

Summary: AG-221 or enasidenib is a first-in-class selective inhibitor of mutated isocitrate dehydrogenase 2 (IDH2) with early demonstrated clinical efficacy in acute myeloid leukemia as a single agent, yet with persistence of mutant IDH2 clones. Two articles in this issue of Cancer Discovery provide further insight into the biological activity of AG-221 in promoting differentiation of IDH2-mutant cells and reversing aberrant DNA methylation over time, and demonstrating preclinical activity in combination with a targeted FLT3 kinase inhibitor to eliminate IDH2-mutant clones. Cancer Discov; 7(5); 459–61. ©2017 AACR.

See related article by Yen et al., p. 478.

See related article by Shih et al., p. 494.

from Cancer via ola Kala on Inoreader http://ift.tt/2oZJ1z5
via IFTTT

HER2+ Tumor Molecular Subtypes Predict Response to Dual HER2 Blockade [Clinical Trials]

Trastuzumab plus lapatinib achieves the highest response rates in HER2-enriched HER2⁺ breast tumors.

from Cancer via ola Kala on Inoreader http://ift.tt/2plMaMv
via IFTTT

BCL6 Antagonizes NOTCH2 to Maintain Survival of Human Follicular Lymphoma Cells [Research Articles]

Although the BCL6 transcriptional repressor is frequently expressed in human follicular lymphomas (FL), its biological role in this disease remains unknown. Herein, we comprehensively identify the set of gene promoters directly targeted by BCL6 in primary human FLs. We noted that BCL6 binds and represses NOTCH2 and NOTCH pathway genes. Moreover, BCL6 and NOTCH2 pathway gene expression is inversely correlated in FL. Notably, BCL6 upregulation is associated with repression of NOTCH2 and its target genes in primary human and murine germinal center (GC) cells. Repression of NOTCH2 is an essential function of BCL6 in FL and GC B cells because inducible expression of Notch2 abrogated GC formation in mice and killed FL cells. Indeed, BCL6-targeting compounds or gene silencing leads to the induction of NOTCH2 activity and compromises survival of FL cells, whereas NOTCH2 depletion or pathway antagonists rescue FL cells from such effects. Moreover, BCL6 inhibitors induced NOTCH2 expression and suppressed growth of human FL xenografts in vivo and primary human FL specimens ex vivo. These studies suggest that established FLs are thus dependent on BCL6 through its suppression of NOTCH2.

Significance: We show that human FLs are dependent on BCL6, and primary human FLs can be killed using specific BCL6 inhibitors. Integrative genomics and functional studies of BCL6 in primary FL cells point toward a novel mechanism whereby BCL6 repression of NOTCH2 drives the survival and growth of FL cells as well as GC B cells, which are the FL cell of origin. Cancer Discov; 7(5); 506–21. ©2017 AACR.

This article is highlighted in the In This Issue feature, p. 443

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via IFTTT

Energy Balance Modulation Impacts Epigenetic Reprogramming, ER{alpha} and ER{beta} Expression, and Mammary Tumor Development in MMTV-neu Transgenic Mice

The association between obesity and breast cancer risk and prognosis is well established in estrogen receptor (ER)-positive disease but less clear in HER2-positive disease. Here, we report preclinical evidence suggesting weight maintenance through calorie restriction (CR) may limit risk of HER2-positive breast cancer. In female MMTV-HER2/neu transgenic mice, we found that ERα and ERβ expression, mammary tumorigenesis, and survival are energy balance dependent in association with epigenetic reprogramming. Mice were randomized to receive a CR, overweight-inducing, or diet-induced obesity regimen (n = 27/group). Subsets of mice (n = 4/group/time point) were euthanized after 1, 3, and 5 months to characterize diet-dependent metabolic, transcriptional, and epigenetic perturbations. Remaining mice were followed up to 22 months. Relative to the overweight and diet-induced obesity regimens, CR decreased body weight, adiposity, and serum metabolic hormones as expected and also elicited an increase in mammary ERα and ERβ expression. Increased DNA methylation accompanied this pattern, particularly at CpG dinucleotides located within binding or flanking regions for the transcriptional regulator CCCTC-binding factor of ESR1 and ESR2, consistent with sustained transcriptional activation of ERα and ERβ. Mammary expression of the DNA methylation enzyme DNMT1 was stable in CR mice but increased over time in overweight and diet-induced obesity mice, suggesting CR obviates epigenetic alterations concurrent with chronic excess energy intake. In the survival study, CR elicited a significant suppression in spontaneous mammary tumorigenesis. Overall, our findings suggest a mechanistic rationale to prevent or reverse excess body weight as a strategy to reduce HER2-positive breast cancer risk. Cancer Res; 77(9); 2500–11. ©2017 AACR.

http://ift.tt/2plIkmv

Genetic Manipulation of Helicobacter pylori Virulence Function by Host Carcinogenic Phenotypes

Helicobacter pylori is the strongest risk factor for gastric adenocarcinoma, yet only a minority of infected persons ever develop this malignancy. One cancer-linked locus is the cag type 4 secretion system (cagT4SS), which translocates an oncoprotein into host cells. A structural component of the cagT4SS is CagY, which becomes rapidly altered during in vivo adaptation in mice and rhesus monkeys, rendering the cagT4SS nonfunctional; however, these models rarely develop gastric cancer. We previously demonstrated that the H. pylori cag+ strain 7.13 rapidly induces gastric cancer in Mongolian gerbils. We now use this model, in conjunction with samples from patients with premalignant lesions, to define the effects of a carcinogenic host environment on the virulence phenotype of H. pylori to understand how only a subset of infected individuals develop cancer. H. pylori cagY sequence differences and cagT4SS function were directly related to the severity of inflammation in human gastric mucosa in either a synchronous or metachronous manner. Serial infections of Mongolian gerbils with H. pylori strain 7.13 identified an oscillating pattern of cagT4SS function. The development of dysplasia or cancer selected for attenuated virulence phenotypes, but robust cagT4SS function could be restored upon infection of new hosts. Changes in the genetic composition of cagY mirrored cagT4SS function, although the mechanisms of cagY alterations differed in human isolates (mutations) versus gerbil isolates (addition/deletion of motifs). These results indicate that host carcinogenic phenotypes modify cagT4SS function via altering cagY, allowing the bacteria to persist and induce carcinogenic consequences in the gastric niche. Cancer Res; 77(9); 2401–12. ©2017 AACR.

http://ift.tt/2oZzJmB

Genomic Instability in Cancer: Teetering on the Limit of Tolerance

Cancer genomic instability contributes to the phenomenon of intratumoral genetic heterogeneity, provides the genetic diversity required for natural selection, and enables the extensive phenotypic diversity that is frequently observed among patients. Genomic instability has previously been associated with poor prognosis. However, we have evidence that for solid tumors of epithelial origin, extreme levels of genomic instability, where more than 75% of the genome is subject to somatic copy number alterations, are associated with a potentially better prognosis compared with intermediate levels under this threshold. This has been observed in clonal subpopulations of larger size, especially when genomic instability is shared among a limited number of clones. We hypothesize that cancers with extreme levels of genomic instability may be teetering on the brink of a threshold where so much of their genome is adversely altered that cells rarely replicate successfully. Another possibility is that tumors with high levels of genomic instability are more immunogenic than other cancers with a less extensive burden of genetic aberrations. Regardless of the exact mechanism, but hinging on our ability to quantify how a tumor's burden of genetic aberrations is distributed among coexisting clones, genomic instability has important therapeutic implications. Herein, we explore the possibility that a high genomic instability could be the basis for a tumor's sensitivity to DNA-damaging therapies. We primarily focus on studies of epithelial-derived solid tumors. Cancer Res; 77(9); 2179–85. ©2017 AACR.

http://ift.tt/2plI07m

Highlights from Recent Cancer Literature

http://ift.tt/2oZpIpM

Master Transcriptional Regulators in Cancer: Discovery via Reverse Engineering Approaches and Subsequent Validation

Reverse engineering of transcriptional networks using gene expression data enables identification of genes that underpin the development and progression of different cancers. Methods to this end have been available for over a decade and, with a critical mass of transcriptomic data in the oncology arena having been reached, they are ever more applicable. Extensive and complex networks can be distilled into a small set of key master transcriptional regulators (MTR), genes that are very highly connected and have been shown to be involved in processes of known importance in disease. Interpreting and validating the results of standardized bioinformatic methods is of crucial importance in determining the inherent value of MTRs. In this review, we briefly describe how MTRs are identified and focus on providing an overview of how MTRs can and have been validated for use in clinical decision making in malignant diseases, along with serving as tractable therapeutic targets. Cancer Res; 77(9); 2186–90. ©2017 AACR.

http://ift.tt/2plRvmL

NR1D1 Recruitment to Sites of DNA Damage Inhibits Repair and Is Associated with Chemosensitivity of Breast Cancer

DNA repair capacity is critical for survival of cancer cells upon therapeutic DNA damage and thus is an important determinant of susceptibility to chemotherapy in cancer patients. In this study, we identified a novel function of nuclear receptor NR1D1 in DNA repair, which enhanced chemosensitivity in breast cancer cells. NR1D1 inhibited both nonhomologous end joining and homologous recombination double-strand breaks repair, and delayed the clearance of γH2AX DNA repair foci that formed after treatment of doxorubicin. PARylation of NR1D1 by PARP1 drove its recruitment to damaged DNA lesions. Deletion of the ligand binding domain of NR1D1 that interacted with PARP1, or treatment of 6-(5H)-phenanthridinone, an inhibitor of PARP1, suppressed the recruitment of NR1D1 to DNA damaged sites, indicating PARylation as a critical step for the NR1D1 recruitment. NR1D1 inhibited recruitment of the components of DNA damage response complex such as SIRT6, pNBS1, and BRCA1 to DNA lesions. Downregulation of NR1D1 in MCF7 cells resulted in resistance to doxorubicin, both in vitro and in vivo. Analysis of four public patient data sets indicated that NR1D1 expression correlates positively with clinical outcome in breast cancer patients who received chemotherapy. Our findings suggest that NR1D1 and its ligands provide therapeutic options that could enhance the outcomes of chemotherapy in breast cancer patients. Cancer Res; 77(9); 2453–63. ©2017 AACR.

http://ift.tt/2oZC1Cv