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Fas ligand expressed in colon cancer is not associated with increased apoptosis of tumor cells in vivo
Author(s) -
Houston Aileen,
WaldronLynch Frank D.,
Bennett Michael W.,
Roche Desmond,
O'Sullivan Gerald C.,
Shanahan Fergus,
O'Connell Joe
Publication year - 2003
Publication title -
international journal of cancer
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.475
H-Index - 234
eISSN - 1097-0215
pISSN - 0020-7136
DOI - 10.1002/ijc.11392
Subject(s) - fas ligand , apoptosis , immune privilege , fas receptor , in vivo , biology , cancer research , immune system , tumor infiltrating lymphocytes , immunohistochemistry , pathology , immunology , programmed cell death , immunotherapy , medicine , biochemistry , microbiology and biotechnology
Expression of Fas ligand (FasL/CD95L) may help to maintain colon cancers in a state of immune privilege by inducing apoptosis of antitumor immune effector cells. Colon tumor‐derived cell lines appear to be relatively insensitive to apoptosis mediated by their own or exogenous FasL in vitro , despite expression of cell surface Fas. In our present study, we sought to investigate if FasL upregulated in human colon cancers leads to any increase in apoptosis of the tumor cells in vivo . FasL and Fas receptor (APO‐1/CD95) expression by tumor cells were detected immunohistochemically. Apoptotic tumor cell death was detected by immunohistochemistry for caspase‐cleaved cytokeratin‐18. FasL expression did not correlate with the extent of apoptosis of tumor cells. There was no significant local difference in the frequency of apoptosis of tumor cells between tumor nests that expressed FasL (mean = 2.4%) relative to those that did not (mean = 2.6%) ( p = 0.625, n = 10; Wilcoxon signed rank). FasL expressed by the tumor cells appeared to be functional, since FasL expression in tumor nests correlated with diminished infiltration of tumor‐infiltrating lymphocytes (TILs). TILs were detected using immunohistochemistry for CD45. Expression of FasL by tumor nests was associated with a mean 4‐fold fewer TILs relative to FasL‐negative nests (range 2.4–33‐fold, n = 10, p < 0.003). Together, our results indicate that colon tumors are insensitive to FasL‐mediated apoptosis in vivo . © 2003 Wiley‐Liss, Inc.