Many natural flavonoids, including quercetin, chrysin, baicalein, apigenin, lutein, and kaempferol, as well as their derivatives, act as inhibitors of HIF-1, regulating main glycolytic enzymes such as pyruvate kinase M2 (PKM2), lactate dehydrogenase (LDH), glucose transporters (GLUTs), hexokinase II (HKII), phosphofructokinase-1 (PFK-1), and pyruvate dehydrogenase kinase (PDK) in various cancer cells [5,305,306,307,308,309,310,311,312,313,314,315,316,317,318,319,320,321,322,323,324,325]. This evidence concerns the gene HIF1A and cancer.