While most of the key enzymes involved in glycolysis are shared between cancer and normal cells, overexpression of pyruvate kinase M2 (PKM2) in cancer cells drives the Warburg effect.5 A growing body of evidence suggests that PKM2 supports cancer cell metabolism and growth not only through its pyruvate kinase activity in the cytosol, but also through its more recently discovered nuclear function as transcriptional coactivator. Here, PKM is linked to cancer.