Typical of a housekeeping gene, DPP4 can be regulated in a cell-type-specific manner [26,27,28] by transcription factors including Stat1α and hepatocyte nuclear factor-1 (HNF-1), specific physiological stimuli (e.g., secreted cytokines) and post-translational modifications (e.g., glycosylation [29]), all of which can be affected by the hypoxic tumour microenvironment [28]. This evidence concerns the gene DPP4 and neoplasm.