Ras-associated protein-1 regulates extracellular signal-regulated kinase activation and migration in melanoma cells: two processes important to melanoma tumorigenesis and metastasis.
Melanoma is one of the most devastating malignancies with a rising incidence and lack of effective treatments for advanced disease. Constitutive activation of the mitogen-activated protein kinase (MAPK) pathway and altered expression of alpha(v)beta(3) integrin are critical for melanoma development and progression. Ras-associated protein-1 (Rap1), a Ras family member of the small GTPases, has emerged as a key mediator in these two important processes. In this study, we have shown Rap1 activation in cells derived from two human metastatic melanomas and also in three of seven cutaneous metastatic melanoma tissues. We found increased extracellular signal-regulated kinase (ERK) activity in the tumors with detected Rap1 activity that interestingly harbored neither BRAF nor N-Ras mutation, suggesting a role for Rap1 in ERK activation in vivo. We also showed Rap1 and ERK activation by both hepatocyte growth factor (HGF) and 8CPT-2Me-cAMP (an activator of Epac, a Rap1 guanine nucleotide exchange factor) in two human melanoma cell lines. In addition, the activation of ERK by HGF was reduced, at least in part, by small interfering RNAs against Rap1 and a dominant-negative Rap1. Finally, a functional role for Rap1 activation was shown by Rap1-induced alpha(v)beta(3) integrin activation and consequent increased melanoma cell migration in vitro. Taken together, these results show that Rap1 is involved in the activation of MAPK pathway and integrin activation in human melanoma and suggest a potential role for Rap1 in melanoma tumorigenesis and metastasis.
Gao
Ling
L
Division of Dermatology, Department of Internal Medicine, Washington University School of Medicine, St. Louis, MO 63110, USA.
Feng
Yunfeng
Y
Bowers
Regina
R
Becker-Hapak
Michelle
M
Gardner
Jennifer
J
Council
Laurin
L
Linette
Gerald
G
Zhao
Haibo
H
Cornelius
Lynn A
LA
D002478:Cells, Cultured; D017931:DNA Primers; D004273:DNA, Neoplasm / Q000235:genetics; D004789:Enzyme Activation; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism*; D005434:Flow Cytometry; D006801:Humans; D039222:Integrin alpha1beta1 / Q000235:genetics; D008544:Melanocytes / Q000166:cytology / Q000502:physiology; D008545:Melanoma / Q000201:enzymology* / Q000473:pathology*; D009362:Neoplasm Metastasis; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012878:Skin Neoplasms / Q000201:enzymology / Q000473:pathology*; D025521:Tumor Suppressor Proteins / Q000235:genetics* / Q000378:metabolism
D017931:DNA Primers; D004273:DNA, Neoplasm; D039222:Integrin alpha1beta1; C411762:RASSF1 protein, human; D025521:Tumor Suppressor Proteins; D048049:Extracellular Signal-Regulated MAP Kinases