Breast cancer cells that successfully metastasize to the liver express high levels of pyruvate dehydrogenase kinase 1 (PDK1) (Figure 2B), which is activated by hypoxia-inducible factor (HIF)-1α and inhibits the function of pyruvate dehydrogenase (PDH), which is a key rate-limiting enzyme that is involved in pyruvate conversion to acetyl-CoA and entry into the tricarboxylic acid (TCA) cycle [32]. This evidence concerns the gene PDK1 and breast cancer.