Induction of Thioredoxin-Interacting Protein by Histone Deacetylase Inhibitor, Entinostat, Is Associated with DNA Damage and Apoptosis in Esophageal Adenocarcinoma

In 2017, an estimated 17,000 individuals were diagnosed with esophageal adenocarcinoma (EAC) and less than 20% will survive 5 years. PET-avidity is indicative of high glucose utilization and is nearly universal in EAC. TXNIP blocks glucose uptake and exhibits pro-apoptotic functions. Higher expression in EAC has been associated with improved disease-specific survival, lack of lymph node involvement, reduced perineural invasion, and increased tumor differentiation. We hypothesized that TXNIP may act as a tumor suppressor that sensitizes EAC cells to standard chemotherapeutics. EAC cell lines and a Barrett's epithelial cell line were used. qRT-PCR, immunoblot, and immunofluorescence techniques evaluated gene expression. TXNIP was stably over-expressed or knocked down using lentiviral RNA transduction techniques. Murine xenograft methods examined growth following over-expression of TXNIP. Apoptosis and DNA damage were measured by Annexin V and H2AX assays. Activation of the intrinsic apoptosis was quantitated with green fluorescence protein-caspase 3 reporter assay. In cultured cells and an esophageal tissue array, TXNIP expression was higher in Barrett's epithelia and normal tissue compared to EAC. Constitutive over-expression of TXNIP decreased proliferation, clonogenicity, and tumor xenograft growth. TXNIP overexpression increased whereas knockdown abrogated DNA damage and apoptosis following cisplatin treatment. An HDAC-inhibitor, entinostat (currently in clinical trials), upregulated TXNIP and synergistically increased cisplatin-mediated DNA damage and apoptosis. TXNIP is a tumor suppressor that is down-regulated in EACC. Its re-expression dramatically sensitizes these cells to cisplatin. Our findings support phase I/II evaluation of 'priming' strategies to enhance the efficacy of conventional chemotherapeutics in EAC.

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