Expression of Fas ligand and Caspase-3 contributes to formation of immune escape in gastric cancer

AIM: To study the role of Fas ligand (FasL) and Caspase-3expression in carcinogenesis and progression of gastric cancer and molecular mechanisms of relevant immune escape.METHODS: FasL and Caspase-3 expression was studied in adjacent epithelial cells, cancer cells and lymphocytes of primary foci, and cancer cells of metastatic foci from 113 cases of gastric cancer by streptavidin-biotin-peroxidase (S-P) immunohistochemistry. Expression of both proteins in cancer cells of primary foci was compared with clinicopathological features of gastric cancer. The relationship between FasL expression in cancer cells and Caspase-3expression in cancer cells or infiltrating lymphocytes of primary foci was investigated.RESULTS: Cancer cells of primary foci expressed FasL in 53.98 % (61/113) of gastric cancers, more than their adjacent epithelial cells (34.51%, 39/113) (P=0.003, X2=8.681), while the expression of Caspase-3 in cancer cells of primary foci was detected in 32.74 % (37/113) of gastric cancers, less than in the adjacent epithelial cells (50.44 %, 57/113)(P=0.007, X2=7.286). Infiltrating lymphocytes of the primary foci showed positive immunoreactivity to Caspase-3 in 70.80 % (80/113) of gastric cancers, more than their corresponding adjacent epithelial cells (P=0.001, X2=10.635)or cancer cells of primary foci (P=0.000, X2=32.767). FasL was less expressed in cancer cells of metastases (51.16 %,22/43) than in those of the corresponding primary foci (81.58 %, 31/38) (P=0.003, X2=9.907). Conversely,Caspase-3 was more expressed in cancer cells of metastases (58.14 %, 25/43) than in those of the corresponding primary foci (34.21%, 13/38) (P=0.031, X2=4.638). FasL expression was significantly correlated with tumor size (P=0.035,rs=0.276), invasive depth (P=0.039, rs=0.195), metastasis (P=0.039, rs=0.195), differentiation (P=0.015, rs=0.228)and Lauren′s classification (P=0.038, rs=0.196), but not with age or gender of patients, growth pattern or TNM staging of gastric cancer (P＞0.05). In contrast, Caspase-3 expression show