Phosphorilated ERK and eIF2alpha levels in melanoma cells.

The differentiation, proliferation and survival of melanocytes and melanoma cells are controlled at various levels. Recently, the importance of translational regulation in promoting and sustaining tumorigenesis is being increasingly recognized. The expression of certain translational factors transiently increases in normal cells in response to growth factors and is constitutively upregulated in tumor cells. The initiation factor IF2 is a central regulator of translation, and is the target of the main pathways of translational control. Activation of eIF2 kinases in response to stress or tumoral transformation has been reported; increased phosphorylation of eIF2 alpha has been correlated with a metastatic phenotype in some kinds of tumors. Phosphorylated ERK levels can be used as marker of cell growth since they are higher in the actively proliferating cells. We investigated whether phosphorylated eIF2-alpha and phosphorylated ERK levels are reliable markers of tumorigenic potential in different melanoma cell lines, and to get insight into the mechanisms whereby eIF2-alpha phosphorylation may modulate cellular transformation. In our melanoma cell lines, showed different levels of phosphorylated eIF2alpha and phosphorylated ERK, which were higher in the cell lines derived from metastatic tumours as compared to primary melanoma cell lines. We showed that after treatment with a MEK inhibitor, ERK phosphorylation was inhibited while eIF2alpha phosphorylation was enhanced in all melanoma cell lines. Moreover Western blotting and confocal analyses revealed that phosphorylated eIF2alpha was localized in the nucleus of melanoma cell lines, supporting a possible relationship between phosphorylation levels and subcellular localization of phosphorylated eIF2 alpha and cell proliferation in malignant melanoma.