Nucleoside diphosphate kinase A is an enzyme that in humans is encoded by the NME1 gene. It is thought to be a metastasis suppressor.This gene (NME1) was identified because of its reduced mRNA transcript levels in highly metastatic cells. Nucleoside diphosphate kinase (NDK) exists as a hexamer composed of 'A' (encoded by this gene) and 'B' (encoded by NME2) isoforms. Mutations in this gene have been identified in aggressive neuroblastomas. Two transcript variants encoding different isoforms have been found for this gene. Co-transcription of this gene and the neighboring downstream gene (NME2) generates naturally occurring transcripts (NME1-NME2), which encodes a fusion protein consisting of sequence sharing identity with each individual gene product.