Despite the availability of oxygen, tumor cells favor glycolysis over oxidative phosphorylation, converting large amounts of glucose into lactate rather than fully oxidizing it to CO2 and H2O. This metabolic shift is driven by the overexpression of key glycolytic enzymes, such as hexokinase-2 (HK2), pyruvate kinase (PKM), and lactate dehydrogenase (LDHA), which enable the rapid conversion of pyruvate to lactate. The gene discussed is HK2; the disease is neoplasm.