title: Molecular mechanisms of ZD1839-induced G1-cell cycle arrest and apoptosis in human lung adenocarcinoma A549 cells.
abstract: Epithelial growth factor receptor (EGFR) has been proposed as a target for anticancer therapy. ZD1839 (Iressa) is a quinazoline derivative that selectively inhibits the EGFR tyrosine kinase activity and is under clinical use in cancer patients. However, the molecular mechanisms involved in ZD1839-mediated anticancer effects remain largely uncharacterized. In this study, exposure of human lung adenocarcinoma A549 cells to ZD1839 caused G1 arrest, and subsequently induced apoptosis. Moreover, ZD1839 increased the protein levels of p27(KIP1) and retinoblastoma-related Rb2/p130 while decreased the expression of cyclin-dependent kinase-2 (CDK2), CDK4, CDK6 and cyclin-D1, cyclin-D3. In vitro kinase assay showed that ZD1839 decreased these CDKs expression in A549 cells, leading to significantly reduce their kinase activities. In addition, ZD1839-induced death of A549 cells with characteristics of apoptosis including apoptotic morphological changes, DNA fragmentation and enhancement of TUNEL-positive cell. These events were accompanied by a marked increase of Fas protein expression, and activation of caspase-2, -3, -8. Co-treatment of cells with Fas antagonist antibody significantly blocked ZD1839-induced apoptosis. Caspase-8 and caspase-3 inhibitors, but not a caspase-9 inhibitor, were also capable of restoring cell viability. Our results indicate that downregulation of the expression and function of CDK2, CDK4, CDK6, cyclin-D1 and cyclin-D3, as well as upregulation of p27(KIP1) and pRb2/p130, are strong candidates for the cell cycle regulator that arrests ZD1839-treated A549 cells at G1 phase. Furthermore, upregulation of Fas appears to play a major role in the initiation of ZD1839-induced apoptosis, activation of caspase-8/caspase-3 cascade is involved in the execution phase of this death program.
authors.affiliation: Division of Pulmonary and Critical Care Medicine, Department of Internal Medicine, Taichung Veterans General Hospital, Taichung, Taiwan, ROC.
authors.forename: Gee-Chen
authors.initials: GC
authors.lastname: Chang
authors.forename: Shih-Lan
authors.initials: SL
authors.lastname: Hsu
authors.forename: Jia-Rong
authors.initials: JR
authors.lastname: Tsai
authors.forename: Fong-Pin
authors.initials: FP
authors.lastname: Liang
authors.forename: Sheng-Yi
authors.initials: SY
authors.lastname: Lin
authors.forename: Gwo-Tarng
authors.initials: GT
authors.lastname: Sheu
authors.forename: Chih-Yi
authors.initials: CY
authors.lastname: Chen
mesh_terms: D000230:Adenocarcinoma / Q000473:pathology; D000970:Antineoplastic Agents / Q000494:pharmacology*; D017209:Apoptosis; D042846:CDC2-CDC28 Kinases / Q000378:metabolism; D053148:Caspase 3; D053181:Caspase 8; D020169:Caspases / Q000378:metabolism; D018797:Cell Cycle Proteins / Q000378:metabolism; D002455:Cell Division / Q000187:drug effects; D051357:Cyclin-Dependent Kinase 2; D051358:Cyclin-Dependent Kinase 4; D051361:Cyclin-Dependent Kinase 6; D018844:Cyclin-Dependent Kinases / Q000378:metabolism; D004789:Enzyme Activation; D016193:G1 Phase / Q000187:drug effects*; D000077156:Gefitinib; D006801:Humans; D008175:Lung Neoplasms / Q000473:pathology; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism; D011799:Quinazolines / Q000494:pharmacology*; D015398:Signal Transduction / Q000502:physiology; D014407:Tumor Cells, Cultured; D019014:fas Receptor / Q000502:physiology
chemical_list: D000970:Antineoplastic Agents; D018797:Cell Cycle Proteins; D011518:Proto-Oncogene Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D011799:Quinazolines; D019014:fas Receptor; D042846:CDC2-CDC28 Kinases; C495894:CDK2 protein, human; C495900:CDK4 protein, human; C495911:CDK6 protein, human; D051357:Cyclin-Dependent Kinase 2; D051358:Cyclin-Dependent Kinase 4; D051361:Cyclin-Dependent Kinase 6; D018844:Cyclin-Dependent Kinases; D020928:Mitogen-Activated Protein Kinases; C505407:CASP3 protein, human; C505530:CASP8 protein, human; D053148:Caspase 3; D053181:Caspase 8; D020169:Caspases; D000077156:Gefitinib