Down-regulation of Rap1GAP via promoter hypermethylation promotes melanoma cell proliferation, survival, and migration.
Melanoma is the most serious, highly aggressive form of skin cancer with recent dramatic increases in incidence. Current therapies are relatively ineffective, highlighting the need for a better understanding of the molecular mechanisms contributing to the disease. We have previously shown that activation of Rap1 promotes melanoma cell proliferation and migration through the mitogen-activated protein kinase pathway and integrin activation. In the present study, we show that expression of Rap1GAP, a specific negative regulator of Rap1, is decreased in human melanoma tumors and cell lines. Overexpression of Rap1GAP in melanoma cells blocks Rap1 activation and extracellular signal-regulated kinase (ERK) phosphorylation and inhibits melanoma cell proliferation and survival. In addition, overexpression of Rap1GAP also inhibits focal adhesion formation and decreases melanoma cell migration. Rap1GAP down-regulation is due to its promoter methylation, a mechanism of gene silencing in tumors. Furthermore, treatment of melanoma cells with the demethylating agent 5-aza-2'-deoxycytidine reinduces Rap1GAP expression, followed by decreased Rap1 activity, ERK phosphorylation, and cell proliferation and survival-changes that are significantly blunted in cells transfected by small interfering RNA-mediated Rap1GAP knockdown. Taken together, our findings indicate that down-regulation of Rap1GAP via promoter hypermethylation promotes melanoma cell proliferation, survival, and migration.
Zheng
Hong
H
Department of Internal Medicine, Division of Dermatology and Hematology, Washington University School of Medicine, St Louis, Missouri 63110, USA.
Gao
Ling
L
Feng
Yunfeng
Y
Yuan
Liya
L
Zhao
Haibo
H
Cornelius
Lynn A
LA
D000964:Antimetabolites, Antineoplastic / Q000494:pharmacology; D001374:Azacitidine / Q000031:analogs & derivatives / Q000494:pharmacology; D048708:Cell Growth Processes / Q000235:genetics; D045744:Cell Line, Tumor; D002465:Cell Movement / Q000235:genetics; D002470:Cell Survival / Q000235:genetics; D019175:DNA Methylation; D000077209:Decitabine; D015536:Down-Regulation; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D022001:Focal Adhesions / Q000235:genetics / Q000378:metabolism; D020690:GTPase-Activating Proteins / Q000096:biosynthesis* / Q000235:genetics; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D008545:Melanoma / Q000188:drug therapy / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D010766:Phosphorylation; D011401:Promoter Regions, Genetic; D014162:Transfection; D020827:rap1 GTP-Binding Proteins / Q000378:metabolism
D000964:Antimetabolites, Antineoplastic; D020690:GTPase-Activating Proteins; C484658:RAP1GAP protein, human; D000077209:Decitabine; D048049:Extracellular Signal-Regulated MAP Kinases; D020827:rap1 GTP-Binding Proteins; D001374:Azacitidine