ERK/MAPK activation involves hypoxia-induced MGr1-Ag/37LRP expression and contributes to apoptosis resistance in gastric cancer.
We previously demonstrated that hypoxia increased the hypoxia-inducible factor (HIF-1)-dependent MGr1-Ag/37LRP expression, which enhanced adhesion of gastric cancer cells to laminin, inhibited drug-induced apoptosis and caused cell adhesion-mediated drug resistance (CAM-DR). Here, we investigated the role of extracellular-regulated kinase (ERK) 1/2 in the signaling mechanisms underlying these events. We found that hypoxia activated ERK activity in vitro and in vivo. Overexpression of mitogen-activated protein kinase (MAPK) kinase (MEK), which preferentially activated ERK, mimics, in a nonadditive way, hypoxia-induced activity of MGr1-Ag/37LRP promoter and expression of MGr1-Ag/37LRP. Furthermore, U0126, the MEK inhibitor, inhibited hypoxia- and MEK-induced MGr1-Ag/37LRP promoter activity in a dose-dependent manner. MEK inhibition also reversed hypoxia- and MEK-induced HIF-1 protein and its activity in a dose-dependent manner. We also investigated reactive oxygen species signaling this response. Exogenous addition of H(2)O(2) was sufficient to activate ERK in a dose-dependent profile. Reactive oxygen species scavengers of H(2)O(2) significantly inhibited hypoxia-induced ERK or HIF-1 activation and sequential expression of MGr1-Ag/37LRP. We also investigated the signaling in hypoxia-induced cell adhesion and apoptosis induced by vincristine. Hypoxia significantly enhanced adhesion of SGC7901 cells to laminin in a time-dependent manner, which might be inhibited by the MEK inhibitor U0126 and MGr1-Ag/37LRP siRNA. Consistent with results of adhesion assay, hypoxia-resistant apoptosis might be reversed by U0126 in a dose-dependent manner. Our results suggest that hypoxia-elicited MGr1-Ag/37LRP expression activated by HIF-1 depends on ERK activation. These events are dependent of reactive oxygen intermediates.
Liu
Lili
L
Department of Pathology and Pathophysiology, Fourth Military Medical University, Xi'an, China.
Zhang
Hongbo
H
Sun
Li
L
Gao
Yuqi
Y
Jin
Haifeng
H
Liang
Shuhui
S
Wang
Yanxia
Y
Dong
Mingqing
M
Shi
Yongquan
Y
Li
Zhichao
Z
Fan
Daiming
D
D000818:Animals; D000951:Antigens, Neoplasm / Q000235:genetics* / Q000378:metabolism; D017209:Apoptosis; D015153:Blotting, Western; D002070:Butadienes / Q000494:pharmacology; D002448:Cell Adhesion; D002465:Cell Movement; D004305:Dose-Response Relationship, Drug; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004797:Enzyme-Linked Immunosorbent Assay; D006801:Humans; D006861:Hydrogen Peroxide / Q000494:pharmacology; D000860:Hypoxia / Q000378:metabolism*; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000037:antagonists & inhibitors / Q000378:metabolism; D051379:Mice; D019950:Mitogen-Activated Protein Kinase 1 / Q000037:antagonists & inhibitors / Q000502:physiology*; D048052:Mitogen-Activated Protein Kinase 3 / Q000037:antagonists & inhibitors / Q000502:physiology*; D009570:Nitriles / Q000494:pharmacology; D016877:Oxidants / Q000494:pharmacology; D010766:Phosphorylation; D011401:Promoter Regions, Genetic / Q000235:genetics; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D034741:RNA, Small Interfering / Q000494:pharmacology; D017382:Reactive Oxygen Species / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction; D013274:Stomach Neoplasms / Q000378:metabolism / Q000473:pathology*; D014407:Tumor Cells, Cultured
D000951:Antigens, Neoplasm; D002070:Butadienes; D004791:Enzyme Inhibitors; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; C470229:MGr1-antigen, human; D009570:Nitriles; D016877:Oxidants; D012333:RNA, Messenger; D034741:RNA, Small Interfering; D017382:Reactive Oxygen Species; C113580:U 0126; D006861:Hydrogen Peroxide; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3