Cancer cells are capable of developing multiple MDR mechanisms, such as increased xenobiotic metabolism by phase I and II drug-metabolizing enzymes (e.g., cytochromes and glutathione-S-transferase), elevated drug efflux (e.g., ATP-binding cassette proteins such as P-glycoprotein (P-gp)), gene mutations (e.g., very common are tumor suppressor gene TP53 and BCR-ABL gene mutations), elevated production of growth factors (e.g., interleukins, protein kinases, extracellular matrix proteins), and enhanced DNA repair capacity [11]. The gene discussed is PGP; the disease is cancer.