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Modeling Colitis-Associated Cancer with Azoxymethane (AOM) and Dextran Sulfate Sodium (DSS)
Published on: September 11, 2012
Association of enhanced cyclooxygenase-2 expression with possible local immunosuppression in human colorectal
M Kojima1, T Morisaki, A Uchiyama
1Department of Surgery and Oncology, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan. kojimam@jwci.org
Background:
Prostaglandin (PG) E2 has an influence on antitumor lymphocyte reactions and causes local immunosuppression at tumor sites. The contribution of cyclooxygenase (COX), a key enzyme in PGE2 synthesis, to this effect is still unclear. We examined if cyclooxygenase (COX)-2 is involved in local immunosuppression in human colon carcinoma cell lines and in clinical tumor specimens.
Methods:
PGE2 concentrations were measured in culture media from a highly COX-2-expressing human colon carcinoma cell line (CE-1) and other cell lines. Lymphocyte proliferation in response to a mitogen was used to evaluate immunosuppression in tumor cell-lymphocyte cocultures with and without selective COX-2 inhibitor NS-398. We also evaluated expression of COX-2 mRNA in surgical specimens of colorectal carcinoma by reverse transcription polymerase chain reaction (RT-PCR) and COX-2 protein by immunohistochemistry, correlating COX-2 expression with clinicopathologic features.
Results:
CE-1 cells produced large amounts of PGE2, which was significantly inhibited by NS-398. The proliferation index of lymphocytes cocultured with CE-1 cells was significantly less than that of control lymphocytes; again, this effect was inhibited by NS-398. While human colorectal carcinoma tissue expressed more COX-2 mRNA and protein than nonneoplastic tissue, no significant correlation was found between COX-2 levels and clinicopathologic features.
Conclusions:
Overexpression of COX-2 in colon cancer may cause local immunosuppression, and COX-2 inhibitors might be therapeutically useful against these tumors.
