title: Hsp90 inhibition by PU-H71 induces apoptosis through endoplasmic reticulum stress and mitochondrial pathway in cancer cells and overcomes the resistance conferred by Bcl-2.
abstract: Heat shock protein 90 (Hsp90) has recently emerged as an attractive therapeutic target in cancer treatment because of its role in stabilizing the active form of a wide range of client oncoproteins. This study investigated the mechanism of apoptosis induced by the purine-scaffold Hsp90 inhibitor PU-H71 in different human cancer cell lines and examined the role of Bcl-2 and Bax in this process. We demonstrated that Hsp90 inhibition by PU-H71 generated endoplasmic reticulum (ER) stress and activated the Unfolded Protein Response (UPR) as evidenced by XBP1 mRNA splicing and up-regulation of Grp94, Grp78, ATF4 and CHOP. In response to PU-H71-induced ER stress, apoptosis was triggered in melanoma, cervix, colon, liver and lung cancer cells, but not in normal human fibroblasts. Apoptosis was executed through the mitochondrial pathway as shown by down-regulation of Bcl-2, up-regulation and activation of Bax, permeabilization of mitochondrial membranes, release of cytochrome c and activation of caspases. We also found that, in contrast to the ER stressor thapsigargin, PU-H71 induced apoptosis in cells overexpressing Bcl-2 and thus overcame the resistance conferred by this anti-apoptotic protein. In addition, although Bax deficiency rendered cells resistant to PU-H71, combined treatment with the anticancer drugs cisplatin or melphalan greatly sensitized these cells to PU-H71. Taken together, these data suggest that inhibition of Hsp90 by PU-H71 is a promising strategy for cancer treatment, particularly in the case of tumors resistant to conventional chemotherapy.
authors.affiliation: INSERM UMR S-769, LabEx LERMIT, Châtenay-Malabry, France.
authors.forename: Cindy
authors.initials: C
authors.lastname: Gallerne
authors.forename: Alexandre
authors.initials: A
authors.lastname: Prola
authors.forename: Christophe
authors.initials: C
authors.lastname: Lemaire
mesh_terms: D000970:Antineoplastic Agents / Q000494:pharmacology; D018906:Antineoplastic Agents, Alkylating / Q000494:pharmacology; D000971:Antineoplastic Combined Chemotherapy Protocols; D017209:Apoptosis / Q000187:drug effects*; D052117:Benzodioxoles / Q000494:pharmacology*; D015153:Blotting, Western; D020169:Caspases / Q000378:metabolism; D049109:Cell Proliferation / Q000187:drug effects; D002945:Cisplatin / Q000494:pharmacology; D019008:Drug Resistance, Neoplasm / Q000187:drug effects*; D000091342:Endoplasmic Reticulum Chaperone BiP; D059865:Endoplasmic Reticulum Stress / Q000187:drug effects*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005434:Flow Cytometry; D005455:Fluorescent Antibody Technique; D018841:HSP90 Heat-Shock Proteins / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism; D006801:Humans; D008558:Melphalan / Q000494:pharmacology; D008928:Mitochondria / Q000187:drug effects / Q000378:metabolism; D009369:Neoplasms / Q000188:drug therapy / Q000378:metabolism / Q000473:pathology*; D010766:Phosphorylation / Q000187:drug effects; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000235:genetics / Q000378:metabolism*; D011687:Purines / Q000494:pharmacology*; D012333:RNA, Messenger / Q000235:genetics; D060888:Real-Time Polymerase Chain Reaction; D020133:Reverse Transcriptase Polymerase Chain Reaction; D019284:Thapsigargin / Q000494:pharmacology; D014407:Tumor Cells, Cultured; D056811:Unfolded Protein Response / Q000187:drug effects; D051028:bcl-2-Associated X Protein / Q000378:metabolism
chemical_list: D000970:Antineoplastic Agents; D018906:Antineoplastic Agents, Alkylating; D052117:Benzodioxoles; D000091342:Endoplasmic Reticulum Chaperone BiP; D004791:Enzyme Inhibitors; D018841:HSP90 Heat-Shock Proteins; C000717247:HSPA5 protein, human; D019253:Proto-Oncogene Proteins c-bcl-2; D011687:Purines; D012333:RNA, Messenger; D051028:bcl-2-Associated X Protein; C526550:9H-purine-9-propanamine, 6-amino-8-((6-iodo-1,3-benzodioxol-5-yl)thio)-N-(1-methylethyl)-; D019284:Thapsigargin; D020169:Caspases; D002945:Cisplatin; D008558:Melphalan