title: Role of repair protein Rad51 in regulating the response to gefitinib in human non-small cell lung cancer cells.
abstract: Gefitinib (Iressa, ZD1839) is a selective epidermal growth factor receptor tyrosine kinase inhibitor that can block growth factor-mediated cell proliferation and extracellular signal-regulated kinases 1/2 (ERK1/2) activation. High-level Rad51 expression has been reported in chemoresistant or radioresistant carcinomas. In this study, we examined the role of Rad51 in regulating the response to gefitinib among different human lung cancer cell lines. The H520 line (human squamous cell carcinoma) was less sensitive to gefitinib compared with the H1650 (human adenocarcinoma) or A549 (human bronchioloalveolar carcinoma) lines. In H1650 and A549 cells but not in H520 cells, gefitinib decreased cellular levels of phospho-ERK1/2 and Rad51 protein and message levels. Moreover, gefitinib decreased Rad51 protein levels by enhancing Rad51 protein instability through 26S proteasome-mediated degradation. Inhibition of endogenous Rad51 levels by si-Rad51 RNA transfection significantly enhanced gefitinib-induced cytotoxicity. In contrast, transfection with constitutively active MKK1 vector could restore both Rad51 protein levels and cell survival inhibited by gefitinib. The MKK1/2-ERK1/2 signaling pathway constitutes the upstream signaling for maintaining Rad51 message and protein levels. Rad51 protein can protect lung cancer cells from cytotoxic effects induced by gefitinib. Suppression of Rad51 may be a novel lung cancer therapeutic modality to overcome drug resistance to gefitinib.
authors.affiliation: Department of Biochemical Science and Technology, National Chiayi University, 300 Syuefu Road, Chiayi 600, Taiwan.
authors.forename: Jen-Chung
authors.initials: JC
authors.lastname: Ko
authors.forename: Jhao-Hao
authors.initials: JH
authors.lastname: Hong
authors.forename: Lyu-Han
authors.initials: LH
authors.lastname: Wang
authors.forename: Chau-Ming
authors.initials: CM
authors.lastname: Cheng
authors.forename: Shih-Ci
authors.initials: SC
authors.lastname: Ciou
authors.forename: Szu-Ting
authors.initials: ST
authors.lastname: Lin
authors.forename: Ming-Yan
authors.initials: MY
authors.lastname: Jheng
authors.forename: Yun-Wei
authors.initials: YW
authors.lastname: Lin
mesh_terms: D000970:Antineoplastic Agents / Q000494:pharmacology*; D002289:Carcinoma, Non-Small-Cell Lung / Q000188:drug therapy* / Q000378:metabolism; D045744:Cell Line, Tumor; D000077156:Gefitinib; D006801:Humans; D008175:Lung Neoplasms / Q000188:drug therapy* / Q000378:metabolism; D048369:MAP Kinase Kinase 1 / Q000037:antagonists & inhibitors / Q000378:metabolism; D019950:Mitogen-Activated Protein Kinase 1 / Q000037:antagonists & inhibitors / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3 / Q000037:antagonists & inhibitors / Q000378:metabolism; D010766:Phosphorylation; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism; D011799:Quinazolines / Q000494:pharmacology*; D051135:Rad51 Recombinase / Q000378:metabolism*; D015398:Signal Transduction; D014162:Transfection
chemical_list: D000970:Antineoplastic Agents; D011799:Quinazolines; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D048369:MAP Kinase Kinase 1; D051135:Rad51 Recombinase; D046988:Proteasome Endopeptidase Complex; C061553:ATP dependent 26S protease; D000077156:Gefitinib