HLA-G expression in gastric carcinoma: clinicopathological correlations and prognostic impact.

To analyze expression of human leukocyte antigen-G (HLA-G) in gastric adenocarcinoma and correlate its expression with histological and clinical variables. A continuous series of 94 unselected patients with gastric adenocarcinoma (stage I to III) were selected. All histological and clinical variables were collected including the intensity of intra- and peri-tumor lymphocytic infiltration. HLA-G expression was investigated using immunohistochemistry. All histological samples analyzed for HLA-G expression were taken from the primary gastric lesion and included non-neoplastic mucosa. Evaluation of HLA-G expression was performed on the transition zone between tumor and non-neoplastic mucosa, and the invasive front of the tumor and assessment was performed as follows: percentage of positive (strong expression vs weak) cells. A variable amount of HLA-G-positive tumor cells was found in 24 out of 94 cases (25.5%). No significant correlation was found between HLA-G expression and other clinicopathological variables (sex, age, stage, grade, histotype). The overall median survival was worse in patients with HLA-G-positive adenocarcinoma (24.3 months, CI 7.7-41.0) compared to those with HLA-G-negative tumors (66.3 months, CI 53.0-79.7; p < 0.0001). Two- and 5-year survival rates of HLA-G-negative patients were 88 and 44%, respectively, while were 42 and 11% in those HLA-G-positive. This trend was observed in all stages but was more marked in stage III. HLA-G expression is associated with poor survival in stage III gastric cancer patients and represents a possible immunoescape mechanism of cancer cells.