title: Quantitative cell signalling analysis reveals down-regulation of MAPK pathway activation in colorectal cancer.
abstract: Mitogen-activated protein kinases (MAPK) are considered to play significant roles in colonic carcinogenesis and kinase inhibitor therapy has been proposed as a potential tool in the treatment of this disease. Reverse-phase microarray assays using phospho-specific antibodies can directly measure levels of phosphorylated protein isoforms. In the current study, samples from 35 cases of untreated colorectal cancer colectomies were laser capture-microdissected to isolate epithelium and stroma from cancer as well as normal (i.e. uninvolved) mucosa. Lysates generated from these four tissue types were spotted onto reverse-phase protein microarrays and probed with a panel of antibodies to ERK, p-ERK, p38, p-p38, p-JNK, MEK and p-MEK. Whereas total protein levels were unchanged, or slightly elevated (p38, p = 0.0025) in cancers, activated isoforms, including p-ERK, p-p38 and p-JNK, were decreased two- to four-fold in cancers compared with uninvolved mucosa (p < 0.0023 in all cases except for p-JNK in epithelium, where decrement was non-significant). This was backed up by western blotting. Dukes' stage B and C cancers displayed lower p-ERK and p-p38 expression than Dukes' stage A cancers, although this was not statistically significant. It is concluded that MAPK activity may be down-regulated in colorectal cancer and that further exploration of inhibitory therapy in this system should be carefully evaluated if this finding is confirmed in larger series.
authors.affiliation: Department of Pathology, Beaumont Hospital, Dublin, Ireland. christiangulmann@beaumont.ie
authors.forename: Christian
authors.initials: C
authors.lastname: Gulmann
authors.forename: Katherine M
authors.initials: KM
authors.lastname: Sheehan
authors.forename: Ronán M
authors.initials: RM
authors.lastname: Conroy
authors.forename: Julia D
authors.initials: JD
authors.lastname: Wulfkuhle
authors.forename: Virginia
authors.initials: V
authors.lastname: Espina
authors.forename: Michelle J
authors.initials: MJ
authors.lastname: Mullarkey
authors.forename: Elaine W
authors.initials: EW
authors.lastname: Kay
authors.forename: Lance A
authors.initials: LA
authors.lastname: Liotta
authors.forename: Emanuel F
authors.initials: EF
authors.lastname: Petricoin
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D015153:Blotting, Western; D015179:Colorectal Neoplasms / Q000201:enzymology* / Q000235:genetics / Q000473:pathology; D053843:DNA Mismatch Repair; D015536:Down-Regulation; D004789:Enzyme Activation; D005260:Female; D020869:Gene Expression Profiling / Q000379:methods; D006801:Humans; D007150:Immunohistochemistry; D007527:Isoenzymes / Q000378:metabolism*; D048670:MAP Kinase Kinase 4 / Q000032:analysis / Q000378:metabolism; D020935:MAP Kinase Signaling System / Q000502:physiology*; D008297:Male; D008875:Middle Aged; D020928:Mitogen-Activated Protein Kinases / Q000032:analysis / Q000378:metabolism*; D009367:Neoplasm Staging; D020411:Oligonucleotide Array Sequence Analysis; D010766:Phosphorylation; D048051:p38 Mitogen-Activated Protein Kinases / Q000032:analysis / Q000378:metabolism
chemical_list: D007527:Isoenzymes; D020928:Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases; D048670:MAP Kinase Kinase 4