PKM and colon carcinoma: Cortes-Cros et al., demonstrated that knocking down of PKM2 in colon carcinoma cell lines led to a decrease in PKM2 activity and an increase in the pyruvate kinase substrate phosphoenol pyruvate, leading to an increased macromolecular biosynthesis required for rapid proliferation; suggesting that PKM2 influences the metabolic state of the cells and has a role in tumor maintenance and growth in vivo [42, 43].