Specifically, EC31 reverses drug resistance in breast cancer (LCC6/MDR), leukemia (P388/ADR and K-562/P-gp) and human oral epidermal cancer (KB-A1) cells by inhibiting P-gp-mediated drug efflux and restoring intracellular drug accumulation [535, 536]. The gene discussed is PGP; the disease is breast carcinoma.