title: Psorospermin structural requirements for P-glycoprotein resistance reversal.
abstract: Resistance to chemotherapy reduces its effectiveness, resulting in increased mortality. Psorospermin, a natural product, is a topoisomerase II-directed DNA alkylating agent active against multidrug-resistant (MDR) cell lines, including multiple myeloma. In this study, the mechanism of the P-glycoprotein (P-gp) modulation activity of psorospermin and that of its associated pharmacophore were examined. Flow cytometry shows that doxorubicin-resistant multiple myeloma cells (8226/D40) pretreated with psorospermin enhance intracellular retention of doxorubicin compared with control (75% versus 38%). Because the overexpression of P-gp is the primary cause of drug resistance in the 8226/D40 cells, psorospermin-induced sensitization was likely due to mdr1/P-gp expressional or functional inhibition. As shown by PCR and Western blot, neither transcription of mdr1 nor translation of P-gp was down-regulated by psorospermin treatment. Therefore, the mechanism of psorospermin-induced resistance reversal is most likely through a direct interaction between psorospermin and P-gp. Furthermore, because only the (2'R,3'R) isomer of psorospermin showed any resistance reversal activity, the side chain of psorospermin is apparently a crucial moiety for resistance reversal. By understanding the mechanism of psorospermin-induced MDR modulation, psorospermin and similar compounds can be combined with other chemotherapies to treat resistant cancers.
authors.affiliation: BIO5 Collaborative Research Institute, University of Arizona, 1657 East Helen Street, Tucson, AZ 85721, USA.
authors.forename: Steven S
authors.initials: SS
authors.lastname: Carey
authors.forename: Mary
authors.initials: M
authors.lastname: Gleason-Guzman
authors.forename: Vijay
authors.initials: V
authors.lastname: Gokhale
authors.forename: Laurence H
authors.initials: LH
authors.lastname: Hurley
mesh_terms: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000378:metabolism*; D018906:Antineoplastic Agents, Alkylating / Q000737:chemistry* / Q000494:pharmacology; D045744:Cell Line, Tumor; D004305:Dose-Response Relationship, Drug; D004317:Doxorubicin / Q000494:pharmacology; D018432:Drug Resistance, Multiple; D019008:Drug Resistance, Neoplasm; D006801:Humans; D009101:Multiple Myeloma / Q000188:drug therapy / Q000378:metabolism; D014158:Transcription, Genetic; D044004:Xanthones / Q000737:chemistry* / Q000494:pharmacology
chemical_list: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D018906:Antineoplastic Agents, Alkylating; D044004:Xanthones; C025543:psorospermin; D004317:Doxorubicin