To investigate the effects and mechanisms of Mirk involving MAPK/ERK pathway in human cancer cells, the upstream or downstream signals of ERK1/2 were first determined in a representative panel of H292 and OVCAR3 cells treated with 20 nM siRNA duplexes, with Mirk siRNA #4 targeting Mirk for 72 h as reported previously [10]. This evidence concerns the gene MAPK3 and cancer.