HIF1A and nonpapillary renal cell carcinoma: The mutation of PBRM1 in ccRCC 786-O cells, in which HIF1α was not fully expressed, suppressed survival and proliferation by decreasing the expression of a key pro-oncogenic factor, HIF2α, which results in the accumulation of hypoxia-inducible factors that drive dysregulated angiogenesis (27, 28).