These data suggest that I-2PP2A/SET negatively regulates cell growth by inhibiting the G1/S transition and inhibiting the MEK/ERK pathway stimulated by external stimuli.     ///    "By contrast, knocking down I-2PP2A/SET by siRNA resulted in enhancement of ERK and MEK activations, suggesting that I-2PP2A/SET negatively regulates MEK/ERK. "    ///    The oncoprotein I-2PP2A/SET negatively regulates the MEK/ERK pathway and cell proliferation.. 