Employing conditional knockout of Pkm1 or Pkm2 targeting the isoform-specific exons, previous reports emphasized the role of PKM1 and PKM2 in metabolic remodeling in tumor cells [20,21,25–27], but the survivability of Pkm1 or Pkm2 KO mice may be mainly due to elevated expression of the other isoform. The gene discussed is PKM; the disease is neoplasm.