title: Biochemical mechanism of modulation of human P-glycoprotein by stemofoline.
abstract: The resistance to chemotherapeutic drugs by cancer cells is considered to be one of the major obstacles for success in the treatment of cancer. A major mechanism underlying this multidrug resistance is the overexpression of P-glycoprotein (P-gp), resulting in insufficient drug delivery to the tumor sites. A previous study has shown that stemofoline, an alkaloid isolated from Stemona burkillii, could enhance the sensitivity of chemotherapeutics in a synergistic fashion. In the present study, we have focused on the effect of stemofoline on the modulation of P-gp function in a multidrug resistant human cervical carcinoma cell line (KB-V1). The effects of stemofoline on a radiolabeled drug, [(3)H]-vinblastine, and fluorescent P-gp substrates, rhodamine 123 and calcein-AM accumulation or retention were investigated to confirm this finding. Stemofoline could increase the accumulation or retention of radiolabeled drugs or fluorescent P-gp substrates in a dose-dependent manner. For additional studies on drug-P-gp binding, P-gp ATPase activity was stimulated by stemofoline in a concentration-dependent manner. More evidence was offered that stemofoline inhibits the effect on photoaffinity labeling of P-gp with [(125)I]-iodoarylazidoprazosin in a concentration-dependent manner. These data indicate that stemofoline may interact directly with P-gp and inhibit P-gp activity, whereas stemofoline has no effect on P-gp expression. Taken together, the results exhibit that stemofoline possesses an effective MDR modulator, and may be used in combination with conventional chemotherapeutic drugs to reverse MDR in cancer cells.
authors.affiliation: Department of Biochemistry, Faculty of Medicine, Chiang Mai University, Chiang Mai, Thailand.
authors.forename: Wisinee
authors.initials: W
authors.lastname: Chanmahasathien
authors.forename: Shinobu
authors.initials: S
authors.lastname: Ohnuma
authors.forename: Suresh V
authors.initials: SV
authors.lastname: Ambudkar
authors.forename: Pornngarm
authors.initials: P
authors.lastname: Limtrakul
mesh_terms: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000737:chemistry / Q000187:drug effects*; D000251:Adenosine Triphosphatases / Q000737:chemistry; D000818:Animals; D000970:Antineoplastic Agents / Q000494:pharmacology; D001386:Azides / Q000494:pharmacology; D001665:Binding Sites; D045744:Cell Line, Tumor; D004305:Dose-Response Relationship, Drug; D018432:Drug Resistance, Multiple; D019008:Drug Resistance, Neoplasm; D005434:Flow Cytometry; D005452:Fluoresceins / Q000737:chemistry; D005456:Fluorescent Dyes / Q000737:chemistry; D006576:Heterocyclic Compounds, 4 or More Rings / Q000494:pharmacology*; D006801:Humans; D007313:Insecta / Q000737:chemistry; D008566:Membranes / Q000187:drug effects; D019920:Photoaffinity Labels / Q000737:chemistry; D018517:Plant Roots / Q000737:chemistry; D011224:Prazosin / Q000031:analogs & derivatives / Q000494:pharmacology; D011485:Protein Binding; D020112:Rhodamine 123 / Q000737:chemistry; D041901:Stemonaceae / Q000737:chemistry; D014747:Vinblastine / Q000494:pharmacology
chemical_list: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D000970:Antineoplastic Agents; D001386:Azides; D005452:Fluoresceins; D005456:Fluorescent Dyes; D006576:Heterocyclic Compounds, 4 or More Rings; D019920:Photoaffinity Labels; C085925:calcein AM; D020112:Rhodamine 123; C430220:stemofoline; D014747:Vinblastine; C041552:azidoprazosin; D000251:Adenosine Triphosphatases; D011224:Prazosin