HIF1A and neoplasm: In the presence of oxygen, hypoxia-inducible factor-1α (HIF1α) is degraded; however, in a hypoxic microenvironment (e.g., in the context of an aggressive tumour), HIF1α binds to hypoxia-inducible factor-1β (HIF1β), leading to the transcription of target genes, including VEGF, which plays a key role in angiogenesis [14].