The FACT inhibitor CBL0137 synergizes with cisplatin in small cell lung cancer by increasing NOTCH1 expression and targeting tumor-initiating cells

Traditional treatments of small cell lung cancer (SCLC) with cisplatin, a standard of care therapy, spare the tumor-initiating cells (TIC) that mediate drug resistance. Here we report a novel therapeutic strategy that preferentially targets TIC in SCLC in which cisplatin is combined with CBL0137, an inhibitor of the histone chaperone facilitates chromatin transcription (FACT), which is highly expressed in TIC. Combination of cisplatin and CBL0137 killed patient-derived and murine SCLC cell lines synergistically. In response to CBL0137 alone, TIC were more sensitive than non-TIC, in part because CBL0137 increased expression of the tumor suppressor NOTCH1 by abrogating the binding of negative regulator SP3 to the NOTCH1 promoter, and in part because treatment decreased the high expression of stem cell transcription factors. The combination of cisplatin and CBL0137 greatly reduced the growth of a patient-derived xenograft in mice and also the growth of a syngeneic mouse SCLC tumor. Thus, CBL0137 can be a highly effective drug against SCLC, especially in combination with cisplatin.

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