title: Colorectal tumors frequently express phosphorylated mitogen-activated protein kinase.
abstract: Mounting evidence suggests that activation of the mitogen-activated protein (MAP) kinase pathway plays an important role in tumorigenesis. MAP kinase/ERK kinase (MEK), a crucial constituent of this pathway, is activated by phosphorylation, and the phosphorylated MEK (pMEK) in turn activates ERK kinase. The expression of pMEK has been described in some human malignancies, but not in primary human colon tumors. In this study, we analyzed the expression of pMEK in 123 colorectal tumors by immunohistochemistry. pMEK was detected either in the cytoplasm (63 cases) or nucleus (40 cases) in 93 of the 123 tumors (76%). Tubular adenomas and villous adenomas also expressed pMEK in 30% and 40% of the tumors, respectively. By contrast, the epithelial cells in the normal colonic mucosa showed no or only weak expression of pMEK in the cytoplasm. Taken together, these results indicate that MEK is frequently phosphorylated in colorectal tumors, and suggest that phosphorylation of MEK may play a role in the development of colorectal tumors.
authors.affiliation: Department of Pathology, College of Medicine, The Catholic University of Korea, Banpo-dong, Socho-gu, Seoul.
authors.forename: Sug Hyung
authors.initials: SH
authors.lastname: Lee
authors.forename: Jong Woo
authors.initials: JW
authors.lastname: Lee
authors.forename: Young Hwa
authors.initials: YH
authors.lastname: Soung
authors.forename: Su Young
authors.initials: SY
authors.lastname: Kim
authors.forename: Suk Woo
authors.initials: SW
authors.lastname: Nam
authors.forename: Won Sang
authors.initials: WS
authors.lastname: Park
authors.forename: Sang Ho
authors.initials: SH
authors.lastname: Kim
authors.forename: Nam Jin
authors.initials: NJ
authors.lastname: Yoo
authors.forename: Jung Young
authors.initials: JY
authors.lastname: Lee
mesh_terms: D000230:Adenocarcinoma / Q000201:enzymology / Q000235:genetics / Q000473:pathology; D000236:Adenoma / Q000201:enzymology / Q000235:genetics / Q000473:pathology; D003110:Colonic Neoplasms / Q000201:enzymology* / Q000235:genetics / Q000473:pathology; D015179:Colorectal Neoplasms / Q000201:enzymology* / Q000235:genetics / Q000473:pathology; D006801:Humans; D007150:Immunohistochemistry; D020928:Mitogen-Activated Protein Kinases / Q000235:genetics*; D020411:Oligonucleotide Array Sequence Analysis; D010766:Phosphorylation
chemical_list: D020928:Mitogen-Activated Protein Kinases