Effects of ranieramycin M on p-glycoprotien funtion

Abstract

Marine natural products are an invaluable source for novel therapeutic potentials including anticancer activity. Renieramycin M (RM) is a new tetrahydroisoquinoline compound which can be isolated from Xestospongia sp., marine sponges found in the Gulf of Thailand. RM has a high potential as cytotoxic and antitumor agent. However, the effects of RM on multidrug resistance (MDR), which is a major problem for a success of chemotherapy, have not been reported. P-glycoprotein (P-gp) is one of the important mechanisms in MDR phenomenon. In this study, RM was tested for its cytotoxicity in difference cells type including, dermal fibroblast (CC2511), renal epithelial cells (LLC-PK1), buccal carcinoma (KB), lung carcinoma (H460), and an MDR1-gene transfected epithelial cell (LLC-MDR1). In addition, RM was tested for its intrinsic potential ability to modulate P-gp function. The cytotoxicity and the type of cells death were determined by MTT and LDH release assays. The effects of RM on P-gp function were measured by co-treatment of RM with either P-gp substrates (vinblastine, puromycin, rhodamine 123) or P-gp inhibitor (verapamil). Furthermore, the interaction between RM and verapamil was also tested in the study of rhodamine 123 accumulation. The results revealed that RM was more toxic and caused more necrotic death in MDR1-overexpressed cells and cancerous cell lines than in normal cells. The apparent IC50 values (ng/ml) were 0.68 (LLC-MDR1), 2.19 (KB), 2.57 (H460), 11.22 (LLC-PK1), and 20-30 (CC2511). RM neither increased VBL-induced cytotoxicity nor rhodamine 123 accumulations in LLC-PK1 and LLC-MDR1 cells. But RM enhanced puromycin-resistance in LLC-MDR1 cells. The effect of RM induced cytotoxicity was enhanced by verapamil in P-gp overexpressing cells. However, RM could not enhance the effect of verapamil on rhodamine 123 accumulations. In summary, RM has a good potential for anticancer activity with highly selective to MDR1-overexpressing and cancer cells. RM could be a substrate of P-gp, but it could not inhibit P-gp function when co-treatment with VBL and rhodamine 123. In addition, RM could decrease puromycin-induced cytotoxicity in P-gp overexpressing cells.