title: Geldanamycin and its analog induce cytotoxicity in cultured human retinal pigment epithelial cells.
abstract: Geldanamycin (GA), a benzoquinone ansamycin, was originally isolated as a natural product with anti-fungal activity. GA and its analogs, including 17-allylamino-demethoxy geldanamycin (17-AAG), are also known to block the function of a molecular chaperone, heat shock protein 90 (Hsp90). In light of their anti-tumor properties through direct cytotoxicity and anti-angiogenicity, GA has been previously demonstrated to suppress hypoxia-induced VEGF production in retinal pigment epithelium (RPE) cells, implicating its applicability in treating intraocular neovascularization. This study aimed at investigating the effectiveness of Hsp90 inhibitor treatment in suppressing proliferation of cultured human RPE cells and elucidating its underlying mechanism. Cultured RPE cells were treated with GA or 17-AAG and subjected for cell proliferation assay and cell cycle analysis. Expression of apoptotic regulators and survival signaling activity were monitored by Western blotting. The results showed that both GA and 17-AAG significantly inhibited RPE cell proliferation at micromolar levels. Treatment with GA and 17-AAG led to growth arrests in G1 and S phases, increased sub-G1 hypodipoid cell population, induced apoptotic cell death, and upregulated P53 and P21 expression, although the drug-induced Bcl-2 upregulation cannot prevent cell death. Additionally, GA and 17-AAG significantly suppressed constitutive contents of phosphorylated ERK1/2 and total Akt proteins, and completely abrogated wortmannin-sensitized Akt phosphorylation. In conclusion, GA and 17-AAG inhibit RPE cell proliferation and induce cytotoxicity, possibly through downregulating Akt- and ERK1/2-mediated signaling activities. They might potentially constitute a therapeutic agent for ocular disorders with RPE over proliferation, such as proliferative vitreoretinopathy.
authors.affiliation: Department of Ophthalmology, Kaohsiung Medical University Hospital, Kaohsiung Medical University, No 100, Zihyou 1st Rd., Kaohsiung 807, Taiwan.
authors.forename: Wen-Chuan
authors.initials: WC
authors.lastname: Wu
authors.forename: Meng-Hsien
authors.initials: MH
authors.lastname: Wu
authors.forename: Yo-Chen
authors.initials: YC
authors.lastname: Chang
authors.forename: Ming-Chu
authors.initials: MC
authors.lastname: Hsieh
authors.forename: Horng-Jiun
authors.initials: HJ
authors.lastname: Wu
authors.forename: Kai-Chun
authors.initials: KC
authors.lastname: Cheng
authors.forename: Yu-Hung
authors.initials: YH
authors.lastname: Lai
authors.forename: Ying-Hsien
authors.initials: YH
authors.lastname: Kao
mesh_terms: D017304:Annexin A5 / Q000378:metabolism; D000903:Antibiotics, Antineoplastic / Q000633:toxicity*; D017209:Apoptosis / Q000187:drug effects*; D016227:Benzoquinones / Q000633:toxicity*; D015153:Blotting, Western; D002453:Cell Cycle / Q000187:drug effects; D049109:Cell Proliferation / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D002478:Cells, Cultured; D050759:Cyclin-Dependent Kinase Inhibitor p21 / Q000378:metabolism; D005434:Flow Cytometry; D016650:Fluorescein-5-isothiocyanate; D018841:HSP90 Heat-Shock Proteins / Q000037:antagonists & inhibitors*; D006801:Humans; D047029:Lactams, Macrocyclic / Q000633:toxicity*; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3 / Q000378:metabolism; D010766:Phosphorylation; D055213:Retinal Pigment Epithelium / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism; D015854:Up-Regulation
chemical_list: D017304:Annexin A5; D000903:Antibiotics, Antineoplastic; D016227:Benzoquinones; C493956:CDKN1A protein, human; D050759:Cyclin-Dependent Kinase Inhibitor p21; D018841:HSP90 Heat-Shock Proteins; D047029:Lactams, Macrocyclic; D016159:Tumor Suppressor Protein p53; C112765:tanespimycin; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D016650:Fluorescein-5-isothiocyanate; C001277:geldanamycin