HIF1A and cancer: For example, in human lung microvascular endothelial cells and A549 cancer cells, HIF1A mRNA level dramatically diminished from 4–12 h of prolonged hypoxia when cells were exposed to CoCl2 (250 μM), despite a marked induction of HIF1A protein expression over the same time course [8]; this was mainly related to a reduction in HIF1A mRNA stability and an increase in natural antisense HIF1A.