A Study of Fas / Fas - Expression and Apoptosis according to the Progression of Gastric Adenocarclnoma

Lim, Sung Chul; Chang, Jeong Hwan

Abstract

PURPOSE: The purpose of this study was to determine whether Fas-L expression is associated with increased apoptotic induction of tumor-infiltrating lymphocytes (TIL) in human gastric carcinomas.
MATERIALS AND METHODS
The author analysed 38 cases of early gastric carcinoma (EGC) and 61 cases of advanced gastric carcinoma (AGC) who received gastric resection, in whom the number of diffuse type was 38 cases and the number of intestinal type was 61 cases. The author used immunohistochemical staining for Fas, Fas-L and CD45, and TUNEL in situ apoptosis detection kit. TIL were detected by CD45 and apoptosis of TIL were detected by CD45 expression and TUNEL positivity on serial histologic sections.
RESULTS
Fas-L was localized to neoplastic cells in 61% (23/38) of EGC group and 66% (40/61) of AGC group. The extent of Fas-L expression was variable, with both Fas-L positive and negative neoplastic region occuring within tumors. TIL adjacent to Fas-L expressing tumor region were decreased in number and TIL adjacent to FasL-negative tumor region were increased in number; apoptotic induction of TIL showed just the opposite pattern (p<0.05). Fas expression was found essentially homogeneously throughout the tumor mass independent of tumor stage. Fas expression showed 64% (39/61) of intestinal type and 68% (26/38) of diffuse type. Labeling indices for tumoral apoptosis in EGC and AGC were 6.72% and 7.13%, respectively and this difference was statistically insignificant. Co-expression of Fas-L and Fas, which occurred over large areas of the tumors, did not result in an enhanced rate of tumor cell apoptosis. In addition, factors such as tumor stage and other prognostic factors were not concerned in Fas and Fas-L expression, number of TIL and apoptotic induction.
CONCLUSION
These findings suggest Fas-mediated apoptotic depletion of TIL in response to Fas-L expression by stomach cancers, and provide the evidence to support the Fas counterattack as a mechanism of immune escape in gastric cancer. In addition, gastric carcinoma cells of the intestinal and diffuse type did not differ in their expression of the apoptotic receptor Fas.