BCL-xL dependency in chromophobe renal cell carcinoma

Abstract

Chromophobe renal cell carcinoma (ChRCC) is the third most common subtype of kidney cancer, with limited therapeutic options. Using BH3 profiling to screen ChRCC-derived cell lines, we discovered that BH3 peptides targeting BCL-xL promote apoptosis in ChRCC. Downregulation of BCL2L1 is sufficient to induce apoptosis in ChRCC-derived cells, consistent with our screening results. BCL2L1, encoding BCL-xL, is fourfold upregulated in ChRCC compared to normal kidney and has the second highest expression in The Cancer Genome Atlas. BCL2L1 downregulation enhances MCL-1 expression, suggesting a possible compensatory role for MCL-1. Based on these results, we evaluated two BH3 mimetics, A-1331852 (targeting BCL-xL) and S63845 (targeting MCL-1). Their combination resulted in 80% cell death. DT2216, a proteolysis-targeting chimera (PROTAC) that targets BCL-xL for degradation, induced cleaved PARP and caspase 3, indicators of apoptosis. ChRCC cells are known to be highly sensitive to ferroptosis. We combined A-1331852 and S63845 with IKE or RSL3 (ferroptosis-inducing drugs). BCL-xL and MCL-1 inhibition enhanced the susceptibility to ferroptosis, suggesting a link between apoptosis and ferroptosis in ChRCC. These data indicate that BCL-xL maintains ChRCC cell survival by suppressing apoptosis. The BCL-xL-specific PROTAC DT2216, currently in clinical trials, may provide an opportunity for ChRCC therapy.