HIF1A and cancer: The increased expression of HIF-1α protein and known HIF-1α target genes under intermittent hypoxia is a generalized cellular response.151,184 Multiple experiments have compared HIF-1α mRNA levels in HCT116 cells, MCF7 cells, and brain (U251), prostate (PC3), and breast (MDA-MB-231) cancer cell lines after normoxic, chronic hypoxia, and IH exposure.151,184 Surprisingly, HIF-1α mRNA expression levels were decreased in chronic hypoxia and increased in IH in all cell lines compared to normoxia.151,184 The data suggest that HIF-1α expression is controlled differently in IH and chronic hypoxia.