title: Defective autophagy in multidrug resistant cells may lead to growth inhibition by BH3-mimetic gossypol.
abstract: The clinical efficacy of many chemotherapeutic agents has been reduced due to the development of drug resistance. In this article, we aimed to validate gossypol, a natural BH3 mimetic found in cottonseeds, as a potential therapeutic to overcome multidrug resistance (MDR). Gossypol was found to retain its efficacy in v-Ha-ras-transformed NIH 3T3 cells that overexpressed P-glycoprotein (Ras-NIH 3T3/Mdr), which was similar to the efficacy observed in their parental counterparts (Ras-NIH 3T3). A rhodamine assay revealed that the alteration of MDR activity did not contribute to the cytotoxic effect of gossypol. Gossypol caused a G2 /M arrest by the induction of p21(Cip1) and the down-regulation of p27(Kip1) expression in Ras-NIH 3T3 cells, whereas no significant G2 /M arrest was exhibited in Ras-NIH 3T3/Mdr cells. Surprisingly, a 48-h treatment with gossypol induced apoptotic cell death in Ras-NIH 3T3 cells; however, gossypol induced both apoptosis and necrosis in Ras-NIH 3T3/Mdr cells, as determined with flow cytometry analysis. More notably, gossypol preferentially induced autophagy in Ras-NIH 3T3 cells but not in Ras-NIH 3T3/Mdr cells. Coimmunoprecipitation and flow cytometric analysis revealed that gossypol-induced autophagy is independent of the dissociation of Beclin 1 from Bcl-2 in Ras-NIH 3T3 cells. Taken together, these results suggest that the antiproliferative activity of gossypol appears to be due to cell-cycle arrest at the G2 /M phase, with the induction of apoptosis in Ras-NIH 3T3 cells. In addition, defective autophagy might contribute to apoptotic and necrotic cell death in response to gossypol in Ras-NIH 3T3/Mdr cells.
authors.affiliation: Division of Life Sciences, College of Life Sciences and Bioengineering, University of Incheon, Incheon, Republic of Korea.
authors.forename: Jun-Ho
authors.initials: JH
authors.lastname: Ahn
authors.forename: Gun-Hee
authors.initials: GH
authors.lastname: Jang
authors.forename: Michael
authors.initials: M
authors.lastname: Lee
mesh_terms: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000378:metabolism; D000818:Animals; D051017:Apoptosis Regulatory Proteins / Q000378:metabolism; D001343:Autophagy / Q000187:drug effects / Q000235:genetics / Q000502:physiology*; D000071186:Beclin-1; D040761:Biomimetic Materials / Q000494:pharmacology; D002461:Cell Line, Transformed; D049109:Cell Proliferation / Q000187:drug effects; D018432:Drug Resistance, Multiple / Q000235:genetics / Q000502:physiology*; D019008:Drug Resistance, Neoplasm / Q000235:genetics / Q000502:physiology*; D059565:G2 Phase Cell Cycle Checkpoints / Q000187:drug effects; D019450:Genes, MDR; D019254:Genes, bcl-2; D011905:Genes, ras; D006072:Gossypol / Q000494:pharmacology*; D051379:Mice; D008938:Mitosis / Q000187:drug effects; D041681:NIH 3T3 Cells; D009369:Neoplasms / Q000188:drug therapy / Q000378:metabolism / Q000473:pathology
chemical_list: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D051017:Apoptosis Regulatory Proteins; D000071186:Beclin-1; C115010:Becn1 protein, mouse; D006072:Gossypol