Toosendanin down-regulated ABCB1 mRNA expression level under 48 h treatment in resistant breast cancer cell MCF-7/ADM [18], whereas sipholane A 72 h treatment exhibited no influence on P-gp expression level in drug-resistant human colon cancer cell line SW620/Ad300 [19]. The gene discussed is PGP; the disease is malignant colon neoplasm.