ZA interrupts Ras/Erk1/2 downstream signaling pathways, and then reduces the activity of hypoxia inducible factor-1 alpha (HIF-1α), a key element in allowing cells to adapt and survive, which increases the energy metabolism and ATP synthesis in cancer cells [110], and then, suppresses the drug efflux transporter P-glycoprotein (P-gp), decreases the glycolysis and the mitochondrial respiratory chain, and finally induce a cytochrome c/caspase-dependent apoptosis in multidrug resistant cancer cells [75, 108, 109, 111]. Here, PGP is linked to cancer.