PCNA and cancer: PKM2 has three functions in cancer cells: (1) cytoplasmic PKM2 is a tetramer with high enzyme activity, and takes part in glycolysis to provide increased metabolic intermediates for cancer cell biosynthesis, (2) the dimeric isoform of PKM2 can translocate to nucleus and act as a transcriptional co-activator, thereby facilitating the transcription of genes beneficial to growth, such as GLUTs, HIF-1α, VEGF-A, Bax, Bcl-2, and PCNA.