Fas ligand expression in colon cancer: a possible mechanism of tumor immune privilege.
OBJECTIVE
To detect the expression of Fas ligand (FasL) in colon cancer tissues and cell lines and analyze the function of FasL-expressing colon cancer cells in inducing Fas-sensitive T lymphocyte apoptosis.


METHODS
Ninety surgically resected colon cancer tissues and 15 hepatic metastasis specimens were investigated by immunohistochemical method with normal colon mucosa and colon adenoma as control. The relationship between FasL expression and pathologic features was also analyzed. FasL expression of 4 colon cancer cell lines, SW620, Lovo, LS-174T and SW1116, were detected by Western blotting assay. The function of FasL expressed on colon cancer cells was determined by coculture assay with Jurkat T lymphocytes, the apoptotic rate of which was detected by flow cytometry assay.


RESULTS
Fifty-six (62.22%) cases of all the 90 colon cancer tissues and all (100%) the liver metastasis specimens expressed FasL, significantly higher than normal colon mucosa and colonic adenoma. Higher expression of FasL was found in more advanced stage of colon cancer and in cancer tissues with lymphatic or hepatic metastasis. All the colon cancer cell lines were found to express FasL. After coculture with the SW1116 cells for 24 h with an effector: target ratio 10:1, the rate of apoptosis of Jurkat cells rose from 1.9% to 21.0%.


CONCLUSIONS
The expression of FasL is upregulated in colon cancer and the functionally expressed FasL can induce apoptosis of Fas-expressing T lymphocytes.
Zhang
Wei
W
Department of General Surgery, Changzheng Hospital, Second Military Medical University, Shanghai 20003, China. zhangwei412@yahoo.com.cn
Ding
Er-Xun
EX
Wang
Qiang
Q
Zhu
Da-Qiao
DQ
He
Jin
J
Li
Yu-Li
YL
Wang
Yuan-He
YH
D017209:Apoptosis / Q000276:immunology; D045744:Cell Line, Tumor; D003110:Colonic Neoplasms / Q000276:immunology* / Q000473:pathology; D053222:Fas Ligand Protein; D006801:Humans; D007150:Immunohistochemistry; D007413:Intestinal Mucosa / Q000276:immunology / Q000473:pathology; D019169:Jurkat Cells; D008562:Membrane Glycoproteins / Q000378:metabolism*; D013601:T-Lymphocytes / Q000166:cytology / Q000276:immunology / Q000473:pathology
C505661:FASLG protein, human; D053222:Fas Ligand Protein; D008562:Membrane Glycoproteins