title: Apoptosis induction by MEK inhibition in human lung cancer cells is mediated by Bim.
abstract: AZD6244 (ARRY-142886) is an inhibitor of MEK1/2 and can inhibit cell proliferation or induce apoptosis in a cell-type dependent manner. The precise molecular mechanism of AZD6244-induced apoptosis is not clear. To investigate mechanisms of AZD6244 induced apoptosis in human lung cancer, we determined the molecular changes of two subgroups of human lung cancer cell lines that are either sensitive or resistant to AZD6244 treatment. We found that AZD6244 elicited a large increase of Bim proteins and a smaller increase of PUMA and NOXA proteins, and induced cell death in sensitive lung cancer cell lines, but had no effect on other Bcl-2 related proteins in those cell lines. Knockdown of Bim by siRNA greatly increased the IC(50) and reduced apoptosis for AZD6244 treated cells. We also found that levels of endogenous p-Thr32-FOXO3a and p-Ser253-FOXO3a were lower in AZD6244-sensitive cells than in AZD6244-resistant cells. In the sensitive cells, AZD6244 induced FOXO3a nuclear translocation required for Bim activation. Moreover, the silencing of FOXO3a by siRNA abrogated AZD6244-induced cell apoptosis. In addition, we found that transfection of constitutively active AKT up-regulated p-Thr32-FOXO3a and p-Ser253-FOXO3a expression and inhibited AZD6244-induced Bim expression in sensitive cells. These results show that Bim plays an important role in AZD6244-induced apoptosis in lung cancer cells and that the PI3K/AKT/FOXO3a pathway is involved in Bim regulation and susceptibility of lung cancer cells to AZD6244. These results have implications in the development of strategies to overcome resistance to MEK inhibitors.
authors.affiliation: Department of Thoracic and Cardiovascular Surgery, The University of Texas M. D. Anderson Cancer Center, Houston, Texas, United States of America. jmeng@mdanderson.org
authors.forename: Jieru
authors.initials: J
authors.lastname: Meng
authors.forename: Bingliang
authors.initials: B
authors.lastname: Fang
authors.forename: Yong
authors.initials: Y
authors.lastname: Liao
authors.forename: Christine M
authors.initials: CM
authors.lastname: Chresta
authors.forename: Paul D
authors.initials: PD
authors.lastname: Smith
authors.forename: Jack A
authors.initials: JA
authors.lastname: Roth
mesh_terms: D017209:Apoptosis / Q000187:drug effects; D051017:Apoptosis Regulatory Proteins / Q000235:genetics / Q000378:metabolism*; D000072224:Bcl-2-Like Protein 11; D001562:Benzimidazoles / Q000494:pharmacology; D045744:Cell Line, Tumor; D015536:Down-Regulation / Q000187:drug effects; D004791:Enzyme Inhibitors / Q000494:pharmacology; D000071316:Forkhead Box Protein O3; D051858:Forkhead Transcription Factors / Q000235:genetics / Q000378:metabolism; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D006801:Humans; D008175:Lung Neoplasms / Q000201:enzymology / Q000235:genetics / Q000378:metabolism* / Q000503:physiopathology*; D048369:MAP Kinase Kinase 1 / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism; D048370:MAP Kinase Kinase 2 / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D011518:Proto-Oncogene Proteins / Q000235:genetics / Q000378:metabolism*
chemical_list: C517975:AZD 6244; D051017:Apoptosis Regulatory Proteins; C000606775:BCL2L11 protein, human; D000072224:Bcl-2-Like Protein 11; D001562:Benzimidazoles; D004791:Enzyme Inhibitors; C499517:FOXO3 protein, human; D000071316:Forkhead Box Protein O3; D051858:Forkhead Transcription Factors; D008565:Membrane Proteins; D011518:Proto-Oncogene Proteins; C482128:MAP2K2 protein, human; D048369:MAP Kinase Kinase 1; D048370:MAP Kinase Kinase 2; C482125:MAP2K1 protein, human