In this study, knockdown of Mirk/Dyrk1B by siRNA in either ovarian cancer cells or NSCLC cells led to up-regulated activation of c-Raf-MEK-ERK1/2 pathway, accompanied by increased growth rate and cells from G0/G1 into S of cell cycle which could be blocked by U0126 in a dose-dependent manner. This evidence concerns the gene MAPK3 and ovarian cancer.