Quantitative cell signalling analysis reveals down-regulation of MAPK pathway activation in colorectal cancer.
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.
Gulmann
Christian
C
Department of Pathology, Beaumont Hospital, Dublin, Ireland. christiangulmann@beaumont.ie
Sheehan
Katherine M
KM
Conroy
Ronán M
RM
Wulfkuhle
Julia D
JD
Espina
Virginia
V
Mullarkey
Michelle J
MJ
Kay
Elaine W
EW
Liotta
Lance A
LA
Petricoin
Emanuel F
EF
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
D007527:Isoenzymes; D020928:Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases; D048670:MAP Kinase Kinase 4