The overexpression of P-glycoprotein and MDR1 is a major cause of chemotherapy resistance in tumor cells., P-gp-mediated drug efflux inhibition causes MDR cancer cells to become resensitized to chemotherapeutic agent treatment, which may enable chemotherapy to be successfully administered to patients with MDR tumors (Zheng et al., 2008). The gene discussed is PGP; the disease is neoplasm.