Furthermore, other key enzymes and proteins mediating the Warburg effect, such as monocarboxylate transporter 1 and 4 [16], hexokinase 2 (HK2), lactate dehydrogenase A (LDHA), and pyruvate dehydrogenase kinase 1 (PDK1), have also been reported to be overexpressed in different cancers [14,17]. Here, HK2 is linked to cancer.