MAPK cascades function downstreamof cell surface receptors and other cytoplasmic signaling proteins whose functions are deregulated in cancer and other human pathologic disorders. In light of the recent success in the clinical development of small molecule inhibitors of protein kinases, components of MAPK cascades have been the subject of intense research and drug discovery efforts. Of these, the p44 ERK1 and p42 ERK2 MAPKs have attracted intense research interest because of their critical involvement in the regulation of cell proliferation and survival. In particular, the mutational activation and/or overexpression of upstream signaling components that activate the ERK MAPKs, together with the substantial body of experimental observations demonstrating the necessity of this pathway in oncogene function, has 'validated' this pathway for drug discovery. This has stimulated intensive efforts by the research community and pharmaceutical industry to develop inhibitors of ERK（like ERK1） signaling for cancer treatment.
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