HIF1A and neoplasm: To test whether Notch regulates HIF2α mRNA expression, we expressed an activated form of Notch (Notch1 ICD) (Supplementary Figure 1A) in nine different human tumor cell lines derived from a range of tumors (renal, breast, lung, brain, and blood cancer cells), and monitored HIF1α and HIF2α mRNA levels in normoxia (21% oxygen).