PKM and cancer: Key enzymes in glycolysis such as glucose transporter 1 (GLUT1), hexokinase 2 (HK2), phosphoglycerate kinase 1 (PGK1), pyruvate kinase M2 (PKM2), lactate dehydrogenase A (LDHA), and monocarboxylate transporter 4 (MCT4) have been observed to be highly expressed in cancer tissues [7].