As it is well-known that drug transporters play a crucial role in cancer drug resistance [27], we examined the expression levels of several drug transporters, including ABCB1 (MDR1), ABCC1 (MRP1), ABCG2/BCRP, and LRP/MVP, in MDA-MB-231Tx cells by RT-PCR. The gene discussed is ABCG2; the disease is cancer.