HLA-G Expression in Tumor Tissues and Soluble HLA-G Plasma Levels in Patients with Gastrointestinal Cancer

Abstract

Background: Overexpression of human leukocyte antigen G (HLA-G) and increased plasma levels of soluble<br />HLA-G (sHLA-G) have been reported in different human malignancies, and are believed to be involved in tumor immune<br />evasion. Objectives: This study was designed to evaluate the expression of HLA-G in tumor tissues and the plasma<br />levels of sHLA-G in patients with gastrointestinal cancer, and to determine their associations with clinicopathological<br />factors. The link between Helicobacter pylori infection and increased HLA-G expression or sHLA-G levels was also<br />investigated in patients with gastric cancer. Methods: HLA-G expression was investigated in tumor tissues from 100<br />patients with gastric and colorectal adenocarcinoma using immunohistochemistry test, and plasma levels of sHLA-G<br />were measured in 82 patients with ELISA method. The presence of H. pylori genome was investigated in tumor<br />tissues from 25 patients with gastric cancer by PCR method. Results: HLA-G expression was observed in 43% of<br />colorectal cancers and 34.6% of gastric cancers, and was not related with any of the clinicopathological factors. There<br />was a significant correlation between increased sHLA-G level and stage I tumors. Eight of 25 (32%) gastric cancer<br />specimens were positive for H. pylori, of which 3 samples were positive for HLA-G. Soluble HLA-G levels were above<br />the cut-off value in all H. pylori-positive patients. Conclusion: Plasma levels of sHLA-G were significantly increased<br />in our patients with a sensitivity of 89% and a specificity of 62%. Soluble HLA-G level can be considered a useful<br />indicator for the early diagnosis of gastric and colorectal adenocarcinoma.