NME1 and neoplasm: One possible explanation is that both NME1 and NME2 as nucleoside diphosphate kinases might have similar functions at early stages of tumorigenesis to provide nucleoside triphosphates to the proliferating tumor cells but that other, differential functions of these enzymes might be important at later stages when NME1 might be the only isoform to control EMT and metastasis.