Helicobacter pylori is associated with less tumor-infiltrating lymphocytes and a poor prognosis in gastric cancer.

Background: Helicobacter pylori (H. pylori) is carcinogenic and has the potential to cause progressive gastric lesions and gastric cancer (GC), which also represents one of the essential constituents of the tumor microenvironment (TME) of GC. The infiltration and functional status of tumor-infiltrating lymphocytes (TILs) in the TME affect the anti-tumor function of the body. However, the impact of H. pylori on anti-tumor immunity and prognosis of GC is still unclear.

Methods: In this study, we constructed a tissue microarray (TMA) consisting of GC tissues from patients with or without H. pylori infection. We evaluated the status of TILs and the expression of CD3, CD8 and PD-L1 by Hematoxylin-eosin (H&E) staining and immunohistochemical (IHC) staining, respectively. Correlation, Cox regression, and survival analyses were performed.

Results: We found that TIL, CD3, and CD8 were negatively correlated with H. pylori infection. In addition, TIL^high and CD8⁺TILs status were positively associated with better survival. Simultaneously, patients with H. pylori-positive status had decreased survival compared to those in the H. pylori-negative group.

Conclusions: Our study supports the hypothesis that H. pylori infection was positively correlated with less TILs and CD8⁺TILs, which may contribute to anti-tumor immune escape, thus lead to a poor prognosis of GC.