HLA-G Expression in Gastric Cancer

Background: Ectopic HLA-G expression in tumor cells may indicate immune escape from the host immune defense via the inhibitory receptor on natural killer (NK) cells. However, there is little information on HLA-G expression in gastric cancer. Patients and Methods: HLA-G expression was immunohistochemically analyzed in 115 gastric cancer patients and the clinical implications of its expression in gastric cancer were assessed. Moreover, NK cell infiltration into the primary tumor was evaluated using anti-CD57 antibodies. Results: The HLA-G-positive group had a more differentiated histology, less nodal invasion and earlier clinical stage than the HLA-G-negative group and these differences were significant. The 5-year survival rate in the HLA-G-positive group was 78%, which was significantly higher than that in the HLA-G- negative group (51%). NK cell infiltration into the tumor tended to be negatively correlated with HLA-G expression. Conclusion: Our results suggest a high frequency of HLA-G expression in early gastric cancer. However, this may not be directly related to aggressive tumor behavior via escape from the host antitumor immune defense. Further investigation is required. HLA-G is classified as a non-classic HLA-class I, which is also termed a class Ib structure (1). HLA-G is expressed in trophoblasts and helps to maintain pregnancy as part of the fatal protection system (2).