title: Mesothelin inhibits paclitaxel-induced apoptosis through the PI3K pathway.
abstract: Mesothelin, a secreted protein, is overexpressed in some cancers, but its exact function remains unclear. The aim of the present study was to evaluate the possible function of mesothelin. Real-time PCR, RT (reverse transcription)-PCR, cytotoxicity assays, proliferative assays, apoptotic assays by Hoechst staining, detection of active caspases 3 and 7 by flow cytometric analysis, and immunoprecipitation and immunoblotting were performed. Cancer tissues in paclitaxel-resistant ovarian cancer patients expressed higher levels of mesothelin as assessed using real-time PCR than paclitaxel-sensitive ovarian cancer patients (the mean crossing point value change of mesothelin was 26.9+/-0.4 in the resistant group and 34.3+/-0.7 for the sensitive group; P<0.001). Mesothelin also protected cells from paclitaxel-induced apoptosis. The protein expression of Bcl-2 family members, such as Bcl-2 and Mcl-1, was significantly increased regardless of whether cells were treated with exogenous mesothelin or were mesothelin-transfectants. Furthermore, mesothelin-treated cells revealed rapid tyrosine phosphorylation of the p85 subunit of PI3K (phosphoinositide 3-kinase) and ERK (extracellular-signal-regulated kinase) 1/2 for enhancing MAPK (mitogen-activated protein kinase) activity. The anti-apoptotic ability was suppressed and the expression of Bcl-2 family in response to mesothelin was altered by inhibiting PI3K activity, but not by inhibiting MAPK activity. Thus mesothelin can inhibit paclitaxel-induced cell death mainly by involving PI3K signalling in the regulation of Bcl-2 family expression. Mesothelin is a potential target in reducing resistance to cytotoxic drugs.
authors.affiliation: Department of Obstetrics and Gynecology, College of Medicine, National Taiwan University, Taipei, Taiwan.
authors.forename: Ming-Cheng
authors.initials: MC
authors.lastname: Chang
authors.forename: Chi-An
authors.initials: CA
authors.lastname: Chen
authors.forename: Chang-Yao
authors.initials: CY
authors.lastname: Hsieh
authors.forename: Chien-Nan
authors.initials: CN
authors.lastname: Lee
authors.forename: Yi-Ning
authors.initials: YN
authors.lastname: Su
authors.forename: Yu-Hao
authors.initials: YH
authors.lastname: Hu
authors.forename: Wen-Fang
authors.initials: WF
authors.lastname: Cheng
mesh_terms: D000818:Animals; D000972:Antineoplastic Agents, Phytogenic / Q000494:pharmacology / Q000627:therapeutic use; D017209:Apoptosis / Q000187:drug effects*; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D016895:Culture Media, Serum-Free / Q000494:pharmacology; D019008:Drug Resistance, Neoplasm; D005260:Female; D058851:GPI-Linked Proteins; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D015151:Immunoblotting; D008562:Membrane Glycoproteins / Q000235:genetics / Q000378:metabolism* / Q000494:pharmacology; D000090204:Mesothelin; D051379:Mice; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3 / Q000378:metabolism; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D010051:Ovarian Neoplasms / Q000188:drug therapy / Q000378:metabolism / Q000473:pathology; D017239:Paclitaxel / Q000494:pharmacology / Q000627:therapeutic use*; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism*; D000081082:Phosphoinositide-3 Kinase Inhibitors; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism; D034741:RNA, Small Interfering / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014162:Transfection
chemical_list: D000972:Antineoplastic Agents, Phytogenic; D016895:Culture Media, Serum-Free; D058851:GPI-Linked Proteins; D008562:Membrane Glycoproteins; D000090204:Mesothelin; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases; D017239:Paclitaxel; D019869:Phosphatidylinositol 3-Kinases; D000081082:Phosphoinositide-3 Kinase Inhibitors; D019253:Proto-Oncogene Proteins c-bcl-2; D034741:RNA, Small Interfering; C000715528:Msln protein, mouse