Cho et al. found that the sensitivity of RCC to PT2399 is highly dependent on HIF2α levels but that certain RCC cell lines (UMRC-2, 769-P, and SKRC-20) are insensitive to the drug both in culture and animal models, even though all 3 cell lines have HIF2α expression and mutant VHL [23]. The gene discussed is VHL; the disease is renal cell carcinoma.