Epigenetic Treatment of Urothelial Carcinoma Cells Sensitizes to Cisplatin Chemotherapy and PARP Inhibitor Treatment

Muscle-invasive urothelial carcinoma (UC) is treated with cisplatin-based chemotherapy, which is only moderately efficient, mostly due to development of resistance. New therapy approaches are therefore urgently needed. Epigenetic alterations due to frequent mutations in epigenetic regulators contribute to development of the disease and to treatment resistance, and provide targets for novel drug combination therapies. Here, we determined the cytotoxic impact of the second-generation bromodomain protein inhibitor (BETi) PLX51107 on UC cell lines (UCC) and normal HBLAK control cells. PLX51107 inhibited proliferation, induced apoptosis, and acted synergistically with the histone deacetylase inhibitor romidepsin. While PLX51107 caused significant DNA damage, DNA damage signaling and DNA repair were impeded, a state defined as BRCAness. Accordingly, the drug strongly synergized with cisplatin more efficiently than romidepsin, and with the PARP inhibitor talazoparib to inhibit proliferation and induce cell death in UCC. Thus, a BETi can be used to "episensitize" UC cells to cytotoxic chemotherapy and inhibitors of DNA repair by inducing BRCAness in non BRCA1/2 mutated cancers. In clinical applications, the synergy between PLX51107 and other drugs should permit significant dosage reductions to minimize effects on normal tissues.

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Cat.No. Product Name Information Publications Customer Product Validation
S8739 PLX51107 PLX51107 is as a novel BET inhibitor with modest preference for bromodomain-1 (BD1) versus bromodomain-2 (BD2) within each BET protein (Kd = 1.6, 2.1, 1.7, and 5 nM for BD1 and 5.9, 6.2, 6.1 and 120 nM for BD2 of BRD2, BRD3, BRD4, and BRDT, respectively. Among non-BET proteins, PLX51107 shows significant interactions only with the bromodomains of CBP and EP300 (p300) (Kd in the 100 nM range). (4)

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