PKM and cancer: While the PKLR gene only encodes a red blood cell-specific (PKR), and a liver-specific isoform (PKL, also expressed in the kidney), the PKM gene encodes PKM1 and PKM2 isoforms, found in all the other tissues, with PKM2 mainly expressed in proliferating tissues, and especially in cancer cells, where it is involved in the activation of the Warburg effect [316,317,318] but also in gene expression regulation [319,320].