We discovered a stem cell factor (SCF)-triggered, MEK1-independent, and P13K-dependent MAPK activation pathway in the Kit-expressing ovarian cancer cell line HEY. When we knocked down MEK1 with RNA interference (RNAi) to Study the function of MEK1 on the proliferation and Survival of ovarian cancer cells, we found that impaired cell growth still occurred after MEK1 expression had been Suppressed, although MAPK activation remained intact. This Suggests that there is MEK-independent activation of MAPK in the SCF-induced ovarian cancer cell growth process, and that MEK1 still plays a Crucial role in maintaining the malignant properties of ovarian cancer cells even when it fails to activate MAPK as expected. (C) 2009 Elsevier Inc. All rights reserved.