ERK Signaling in Colorectal Cancer: A Preliminary Report on the Expression of Phosphorylated ERK and the Effects of Radiation Therapy

OBJECTIVES: Phosphorylated extracellular signal-regulated kinase (ERK) activates cell survival pathways and may promote tumor cell proliferation. The purpose of this study was to determine the level of phospho-ERK staining in pretreatment specimens, and the effect of a short course of radiation therapy (RT) on the levels of phospho-ERK in specimens of colorectal cancer. METHODS: Specimens of colorectal tumors were obtained from patients beginning RT before surgery. Tumors were graded and histologically staged. Subsequently, tumor samples were reacted with antiphospho-ERK antibodies and the level of staining intensity was assessed. RESULTS: Of the 12 subjects evaluated, 7 of 12 had tumors that positively stained for phospho-ERK before and/or after RT. Most patients who were phospho-ERK positive before RT converted to ERK negativity after RT. CONCLUSIONS: The results of this pilot study indicate that phospho-ERK levels may serve as a prognostic marker in colorectal cancer, and further studies are warranted to determine how changes in phospho-ERK staining relate to clinical outcome.