HIF1A and neoplasm: This was attributed to the fact that in a lactate-rich environment (such as the tumour microenvironment), NAMPT-dependent replenishment of NAD + maintains oxidation of lactate to pyruvate, which promoted stabilisation of the transcription factor, hypoxia-inducible factor-1 alpha (HIF-1α), contributing to differentiation of an M2-like immunosuppressive macrophage phenotype [25].