PKM2 differs from the M1 isoform of pyruvate kinase (PKM1) in a single exon.[7] While PKM1 can only function as a constitutively active tetrameric pyruvate kinase, PKM2 can switch between tetrameric and dimeric forms to alternate between pyruvate kinase and protein kinase.[7] As a dimeric protein kinase, PKM2 can localize to the cell nucleus, activating the transcription of multiple genes, which ultimately leads to tumor progression.[8]. This evidence concerns the gene PKM and neoplasm.