EPAS1 and nonpapillary renal cell carcinoma: Studies using ccRCC cell lines have reported that HIF2α, rather than HIF1α, is important for ccRCC tumorigenicity (Kondo et al. 2003), whereas a recent study using genetically engineered mice has shown that Hif1α, not Hif2α, is crucial for ccRCC formation (Hoefflin et al. 2020).