title: A natural BH3 mimetic induces autophagy in apoptosis-resistant prostate cancer via modulating Bcl-2-Beclin1 interaction at endoplasmic reticulum.
abstract: A natural BH3-mimetic, small-molecule inhibitor of Bcl-2, (-)-gossypol, shows promise in ongoing phase II and III clinical trials for human prostate cancer. In this study we show that (-)-gossypol preferentially induces autophagy in androgen-independent (AI) prostate cancer cells that have high levels of Bcl-2 and are resistant to apoptosis, both in vitro and in vivo, but not in androgen-dependent (AD) cells with low Bcl-2 and sensitive to apoptosis. The Bcl-2 inhibitor induces autophagy through blocking Bcl-2-Beclin1 interaction, together with downregulating Bcl-2, upregulating Beclin1, and activating the autophagic pathway. The (-)-gossypol-induced autophagy is dependent on Beclin1 and Atg5. Our results show for the first time that (-)-gossypol can also interrupt the interactions between Beclin1 and Bcl-2/Bcl-xL at endoplasmic reticulum, thus releasing the BH3-only pro-autophagic protein Beclin1, which in turn triggers the autophagic cascade. Oral administration of (-)-gossypol significantly inhibited the growth of AI prostate cancer xenografts, representing a promising new regimen for the treatment of human hormone-refractory prostate cancer with Bcl-2 overexpression. Our data provide new insights into the mode of cell death induced by Bcl-2 inhibitors, which will facilitate the rational design of clinical trials by selecting patients who are most likely to benefit from the Bcl-2-targeted molecular therapy.
authors.affiliation: Division of Radiation and Cancer Biology, Department of Radiation Oncology, University of Michigan Medical School, Ann Arbor, MI 48109, USA.
authors.forename: J
authors.initials: J
authors.lastname: Lian
authors.forename: X
authors.initials: X
authors.lastname: Wu
authors.forename: F
authors.initials: F
authors.lastname: He
authors.forename: D
authors.initials: D
authors.lastname: Karnak
authors.forename: W
authors.initials: W
authors.lastname: Tang
authors.forename: Y
authors.initials: Y
authors.lastname: Meng
authors.forename: D
authors.initials: D
authors.lastname: Xiang
authors.forename: M
authors.initials: M
authors.lastname: Ji
authors.forename: T S
authors.initials: TS
authors.lastname: Lawrence
authors.forename: L
authors.initials: L
authors.lastname: Xu
mesh_terms: D000284:Administration, Oral; D000728:Androgens / Q000378:metabolism; D000818:Animals; D000970:Antineoplastic Agents / Q000627:therapeutic use*; D017209:Apoptosis; D051017:Apoptosis Regulatory Proteins / Q000235:genetics / Q000378:metabolism*; D001343:Autophagy; D000071187:Autophagy-Related Protein 5; D000071186:Beclin-1; D045744:Cell Line, Tumor; D004721:Endoplasmic Reticulum / Q000378:metabolism*; D005260:Female; D006072:Gossypol / Q000627:therapeutic use*; D006801:Humans; D008297:Male; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D008819:Mice, Nude; D008869:Microtubule-Associated Proteins / Q000235:genetics / Q000378:metabolism; D011471:Prostatic Neoplasms / Q000188:drug therapy*; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D034622:RNA Interference; D034741:RNA, Small Interfering / Q000378:metabolism; D014183:Transplantation, Heterologous; D051020:bcl-X Protein / Q000378:metabolism
chemical_list: C502778:ATG5 protein, human; D000728:Androgens; D000970:Antineoplastic Agents; D051017:Apoptosis Regulatory Proteins; D000071187:Autophagy-Related Protein 5; C491997:BECN1 protein, human; D000071186:Beclin-1; D008565:Membrane Proteins; D008869:Microtubule-Associated Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D034741:RNA, Small Interfering; D051020:bcl-X Protein; D006072:Gossypol