Induction of erythroid differentiation by inhibition of Ras/ERK pathway ina Friend murine leukemia cell line

The role of Ras and MAP kinases (MAPKs) in the regulation of erythroid diff erentiation was studied using a cell line (SKT6) derived from Friend virus (Anemic strain)-induced murine erythroleukemia. This cell line undergoes di fferentiation in vitro in response to erythropoietin (EPO) or other chemica l inducers such as dimethylsulfoxide (DMSO), When a constitutively active r as mutant (ras12V) was expressed in SKT6 cells, EPO-induced differentiation was inhibited. Conversely, a dominant negative I au mutant (ras17N) induce d differentiation even in the absence of EPO, suggesting that the basal Ras activity is essential for the maintenance of the undifferentiated phenotyp e and proliferative potential in this cell line. Rapid inactivation of ERK was observed after expression of ras17N. Slow but significant inactivation of ERR was also observed during EPO-induced differentiation. Furthermore, o verexpression of a constitutively active mutant of ERK-activating kinase (M APKK) was found to suppress erythroid differentiation, while pharmacologica l inhibition of MAPKK induced differentiation. These findings suggest that down-regulation of Ras/ERK signaling pathway may be an essential event in E PO-induced erythroid differentiation in this system.