title: Localization of active, dually phosphorylated extracellular signal-regulated kinase 1 and 2 in colorectal cancer with or without activating BRAF and KRAS mutations.
abstract: Colorectal cancers (CRC) often show activating mutations of the KRAS or BRAF genes, which stimulate the extracellular signal-regulated kinase (ERK) pathway, thus increasing cell proliferation and inhibiting apoptosis. However, immunohistochemical results on ERK activation in such tumors differ greatly. Recently, using a highly optimized immunohistochemical method, we obtained evidence that high levels of ERK activation in rectal adenocarcinomas were associated with resistance to radiochemotherapy. In order to determine whether KRAS and/or BRAF mutations correlate to immunohistochemically detectable increases in phosphorylation of ERK (pERK), we stained biopsies from 36 CRC patients with activating mutations in the BRAF gene (BRAFV600E: BRAF(m)), the KRAS gene (KRAS(m)) or in neither (BRAF/KRAS(n)) with this optimized method. Staining was scored in blind-coded specimens by two observers. Staining of stromal cells was used as a positive control. BRAF(m) or KRAS(m) tumors did not show higher staining scores than BRAF/KRAS(n) tumors. Although BRAFV600E staining occurred in over 90% of cancer cells in all 9 BRAF(m) tumors, 3 only showed staining for pERK in less than 10% of cancer cell nuclei. The same applied to 4 of the 14 KRAS(m) tumors. A phophorylation-insensitive antibody demonstrated that lack of pERK staining did not reflect defect expression of ERK1/2 protein. Thus, increased staining for pERK does not correlate to BRAF or KRAS mutations even with a highly optimized procedure. Further studies are required to determine whether this reflects differences in expression of counterregulatory molecules, including ERK phosphatases.
authors.affiliation: Department of Pathology, Copenhagen University Hospital, DK -2650, Hvidovre, Denmark.
authors.forename: Susanne
authors.initials: S
authors.lastname: Holck
authors.affiliation: Department of Pathology, Copenhagen University Hospital, DK -2650, Hvidovre, Denmark; Clinical Research Centre, Copenhagen University Hospital, DK -2650, Hvidovre, Denmark.
authors.forename: Jesper
authors.initials: J
authors.lastname: Bonde
authors.affiliation: Department of Pathology, Copenhagen University Hospital, DK -2650, Hvidovre, Denmark.
authors.forename: Helle
authors.initials: H
authors.lastname: Pedersen
authors.affiliation: Department of Pathology, Copenhagen University Hospital, DK -2650, Hvidovre, Denmark; Clinical Research Centre, Copenhagen University Hospital, DK -2650, Hvidovre, Denmark.
authors.forename: Anja Alex
authors.initials: AA
authors.lastname: Petersen
authors.affiliation: Department of Pathology, Copenhagen University Hospital, DK -2650, Hvidovre, Denmark.
authors.forename: Amita
authors.initials: A
authors.lastname: Chaube
authors.affiliation: Department of Surgical Gastroenterology, Copenhagen University Hospital, DK -2650, Hvidovre, Denmark.
authors.forename: Hans Jørgen
authors.initials: HJ
authors.lastname: Nielsen
authors.affiliation: Department of Pathology, Copenhagen University Hospital, DK -2650, Hvidovre, Denmark; Clinical Research Centre, Copenhagen University Hospital, DK -2650, Hvidovre, Denmark. Electronic address: lars.inge.larsson@regionh.dk.
authors.forename: Lars-Inge
authors.initials: LI
authors.lastname: Larsson
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D014408:Biomarkers, Tumor / Q000032:analysis* / Q000235:genetics*; D001706:Biopsy; D018938:Caco-2 Cells; D015179:Colorectal Neoplasms / Q000201:enzymology* / Q000235:genetics / Q000473:pathology; D004252:DNA Mutational Analysis; D004789:Enzyme Activation; D005260:Female; D020022:Genetic Predisposition to Disease; D006801:Humans; D007150:Immunohistochemistry; D008297:Male; D008875:Middle Aged; D019950:Mitogen-Activated Protein Kinase 1 / Q000032:analysis*; D048052:Mitogen-Activated Protein Kinase 3 / Q000032:analysis*; D009154:Mutation; D010641:Phenotype; D010766:Phosphorylation; D011237:Predictive Value of Tests; D048493:Proto-Oncogene Proteins B-raf / Q000235:genetics*; D016283:Proto-Oncogene Proteins p21(ras) / Q000235:genetics*
chemical_list: D014408:Biomarkers, Tumor; C117307:KRAS protein, human; C482119:BRAF protein, human; D048493:Proto-Oncogene Proteins B-raf; C535150:MAPK1 protein, human; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D016283:Proto-Oncogene Proteins p21(ras)
keywords: BRAF; Colorectal carcinoma; ERK; Immunohistochemistry; KRAS; Mutations