title: Roles of MKK1/2-ERK1/2 and phosphoinositide 3-kinase-AKT signaling pathways in erlotinib-induced Rad51 suppression and cytotoxicity in human non-small cell lung cancer cells.
abstract: Erlotinib (Tarceva) is a selective epidermal growth factor receptor tyrosine kinase inhibitor in the treatment of human non-small cell lung cancer (NSCLC). In this study, we investigated the roles of ERK1/2 and AKT signaling pathways in regulating Rad51 expression and cytotoxic effects in different NSCLC cell lines treated with erlotinib. Erlotinib decreased cellular levels of phosphorylated ERK1/2, phosphorylated AKT, Rad51 protein, and mRNA in erlotinib-sensitive H1650, A549, and H1869 cells, leading to cell death via apoptosis, but these results were not seen in erlotinib-resistant H520 and H1703 cells. Erlotinib decreased Rad51 protein levels by enhancing Rad51 mRNA and protein instability. Enforced expression of constitutively active MKK1 or AKT vectors could restore Rad51 protein levels, which were inhibited by erlotinib, and decrease erlotinib-induced cytotoxicity. Knocking down endogenous Rad51 expression by si-Rad51 RNA transfection significantly enhanced erlotinib-induced cytotoxicity. In contrast, overexpression of Rad51 by transfection with Rad51 vector could protect the cells from cytotoxic effects induced by erlotinib. Blocking the activations of ERK1/2 and AKT by MKK1/2 inhibitor (U0126) and phosphoinositide 3-kinase inhibitor (wortmannin) suppressed the expression of Rad51 and enhanced the erlotinib-induced cell death in erlotinib-resistant cells. In conclusion, suppression of Rad51 may be a novel therapeutic modality in overcoming drug resistance of erlotinib in NSCLC.
authors: Department of Internal Medicine, Hsinchu Hospital, Department of Health, Executive Yuan, Taiwan.
authors: Jen-Chung
authors: JC
authors: Ko
authors: Shih-Ci
authors: SC
authors: Ciou
authors: Jhih-Yuan
authors: JY
authors: Jhan
authors: Chao-Min
authors: CM
authors: Cheng
authors: Ying-Jhen
authors: YJ
authors: Su
authors: Show-Mei
authors: SM
authors: Chuang
authors: Szu-Ting
authors: ST
authors: Lin
authors: Chia-Che
authors: CC
authors: Chang
authors: Yun-Wei
authors: YW
authors: Lin
mesh_terms: D002289:Carcinoma, Non-Small-Cell Lung / Q000201:enzymology* / Q000235:genetics / Q000473:pathology; D016923:Cell Death / Q000187:drug effects; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D019008:Drug Resistance, Neoplasm / Q000187:drug effects; D004789:Enzyme Activation / Q000187:drug effects; D000069347:Erlotinib Hydrochloride; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism*; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D055785:Gene Knockdown Techniques; D006801:Humans; D008175:Lung Neoplasms / Q000201:enzymology / Q000235:genetics / Q000473:pathology; D020929:Mitogen-Activated Protein Kinase Kinases / Q000378:metabolism*; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism*; D010766:Phosphorylation / Q000187:drug effects; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D011499:Protein Processing, Post-Translational / Q000187:drug effects; D055550:Protein Stability / Q000187:drug effects; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism*; D011799:Quinazolines / Q000494:pharmacology*; D051135:Rad51 Recombinase / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects; D014162:Transfection
chemical_list: D047428:Protein Kinase Inhibitors; D011799:Quinazolines; D000069347:Erlotinib Hydrochloride; D019869:Phosphatidylinositol 3-Kinases; D051057:Proto-Oncogene Proteins c-akt; D048049:Extracellular Signal-Regulated MAP Kinases; D020929:Mitogen-Activated Protein Kinase Kinases; D051135:Rad51 Recombinase; D046988:Proteasome Endopeptidase Complex