HIF1A and neoplasm: Intermittent hypoxia is experienced by almost every carcinoma cell and contributes to the stabilization of the heterodimeric transcription factor hypoxia-inducible factor 1 (HIF-1), which represents a key regulatory factor for the phenotypic expression of tumour cell proliferation, elevated fermentation of glucose, suppression of apoptosis, and angiogenesis (reviewed in Semenza, 2003, see Fig. 2).