Figure 2.

As tumour growth continues, fuelled with nutrients and oxygen from the neovasculature, it begins to outstrip its blood supply and oxygen levels fall. The ensuing cellular hypoxia causes a cascade of events including the production of the transcription factor, hypoxia inducible factor 1 alpha (HIF-1α) [19]. This, in turn, upregulates vascular endothelial growth factor (VEGF), promoting angiogenesis and perpetuating the vicious cycle of hypoxia, tumour growth and angiogenesis (reproduced from [6] with permission).