Shikonin inhibited glycolysis by inhibiting PKM2 in drug-sensitive and resistant cancer cells (MCF-7, MCF-7/Adr, MCF-7/Bcl-xL, MCF-7/Bcl-2 and A549), but had no effect on the expression of PKM1 and PKL (Chen et al., 2011). This evidence concerns the gene PKM and cancer.