TY - JOUR
T1 - Down-regulation of Rap1GAP via promoter hypermethylation promotes melanoma cell proliferation, survival, and migration
AU - Zheng, Hong
AU - Gao, Ling
AU - Feng, Yunfeng
AU - Yuan, Liya
AU - Zhao, Haibo
AU - Cornelius, Lynn A.
PY - 2009/1/15
Y1 - 2009/1/15
N2 - 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 downregulation of Rap1GAP via promoter hypermethylation promotes melanoma cell proliferation, survival, and migration.
AB - 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 downregulation of Rap1GAP via promoter hypermethylation promotes melanoma cell proliferation, survival, and migration.
UR - http://www.scopus.com/inward/record.url?scp=58349118949&partnerID=8YFLogxK
U2 - 10.1158/0008-5472.CAN-08-2399
DO - 10.1158/0008-5472.CAN-08-2399
M3 - Article
C2 - 19147557
AN - SCOPUS:58349118949
SN - 0008-5472
VL - 69
SP - 449
EP - 457
JO - Cancer research
JF - Cancer research
IS - 2
ER -