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A. Calipel, V. Abonnet, J. Cheret, O. Nicole, F. Mascarelli, F. Mouriaux; Involvement of Reduced Expression of RASSF1A in Uveal Melanoma Cells Proliferation Through ERK1/2 Pathway. Invest. Ophthalmol. Vis. Sci. 2009;50(13):5767.
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© ARVO (1962-2015); The Authors (2016-present)
Loss of chromosome 3 is strongly associated with metastasis in uveal melanoma (UM). Localized on 3p21.3, RASSF1A is a tumor suppressor gene and is frequently hypermethylated in human cancers. The mechanisms by which RASSF1A exerts its tumor suppression activities and the involved pathways are not yet fully understood. Constitutive activation of ERK1/2 in absence of RAS or B-RAF mutation has been described in UM. However, mediators involved in the constitutive activation of ERK1/2 in remains to be determined. The aim of this study is to analyse the implication of RASSF1A in activation of ERK1/2 in UM.
DNA methylation status of RASSF1A promoter was analysed through methylation-specific PCR of 30 fresh-frozen UM samples. Loss of heterozygoty of RASSF1A gene was detected with microsatellite markers. Expression of RASSF1A was investigated through real time RT-PCR and Western Blot on normal choroidal melanocytes (NCM) and primary (OCM1, 92.1, mel 270, TP17, µ2) and metastatic (OMM1-3, µ2F, Mum2B, Mum2C) UM cell lines. The cell growth and ERK1/2 activation were observed as the ectopic overexpression and knockdown (siRNA) of RASSF1A
LOH in 3p21.3 was observed in 44% (4 of 9 samples) and methylation of RASSF1A promoter in 70% of primary UM (21 of 30 samples). Down-expression and methylation of RASSF1A promoter was observed in 66% UM cell lines including primary and metastatic. siRNA-mediated depletion of RASSF1A increased ERK1/2 activation with a positive correlation on NCM proliferation. Ectopic expression of RASSF1A in UM cell lines did not affect ERK1/2 activation and reduced weakly (15-20%) UM cell lines proliferation.
These data shown that RASSF1A may be important in control of NCM growth through regulation of ERK1/2 activation. Surexpression of RASSF1A showed that RASSF1A seem less implied in the regulation of ERK1/2 activation and consequently on UM proliferation. Expression of RASSF1A protein might be used as a prognostic factor but not a target for therapy in UM.
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