Apoptosis and Fas-ligand expression correlate to the histopathological grade of gastric smooth muscle tumors

Background. Apoptosis is associated with the tumor grade in various types o f carcinomas or lymphomas, but less is understood about the association of apoptosis in mesenchymal tumors. In the prior studies, expression of apopto tic regulatory proteins, Bcl-2, Fas and its ligand, Fas-ligand, has been re lated to apoptotic index (AI) and histopathological grade of tumors. Our st udy investigated the incidence of apoptosis in gastric smooth muscle tumor and the correlation of the apoptotic index (AI) with the histopathological grade of the tumors. We evaluated the relationship of apoptotic regulatory proteins to the AI and tumor grade. Methods and Materials. Using immunohistochemistry and the terminal deoxynuc leotidyl transferase (TdT)-mediated digoxigenin-dUTP nick end-labeling (TUN EL) assay, we analyzed the expression of Bcl-2, Fas, Fas-ligand, and Al in 26 cases of gastric smooth muscle tumors. Results. The incidence of greater than 10 apoptotic cells per 10 high-power fields (HPFs) was 73% (19/26 cases). The AI was significantly associated w ith malignant tumors (P = 0.006) and mitotic counts (P = 0.006) but not wit h tumor size. Bcl-2, Fas, and Fas-ligand were detected in 13 (50%), 14 (53. 8%), and 19 (73%) cases, respectively. Interestingly, Fas-ligand was signif icantly correlated to malignancy (P = 0.006), mitotic counts (P = 0.006), a nd AI (P = 0.035) but not to tumor size. Fas expression was significantly a ssociated with high levels of AI (P = 0.014). In contrast, Bcl-2 expression was inversely associated with AI (P = 0.004). Expression of Bcl-2 and Fas did not show a statistically significant correlation with tumor grade, mito tic counts, or tumor size. Conclusion. Apoptosis and Fas-ligand expression are statistically correlate d to the histopathological grade of gastric smooth muscle tumors. This sugg ests that detection of apoptotic cells and Fas-ligand expression using the TUNEL assay or immunohistochemistry are useful for the evaluation of the ma lignant potential of gastric smooth muscle tumors. (C) 2001 Academic Press.