Expression characteristics of peripheral lymphocyte programmed death 1 and FoxP3⁺ Tregs in gastric cancer during surgery and chemotherapy

Background: Programmed death 1 (PD-1) and CD4(+)CD25(+)FoxP3(+) expression in peripheral blood T-cells has been previously reported in various types of cancer. However, the specific variation tendency during surgery and chemotherapy, as well as their relationship in gastric cancer patients, still remain unclear. Understanding this aspect may provide some novel insights for future studies on tumor recurrence and tumor immune escape, and also serve as a reference for determining the optimal timing and dose of clinical anti-PD-1 antibodies.Aim: To observe and analyze the expression characteristics of peripheral lymphocyte PD-1 and FoxP3(+) regulatory T cells (FoxP3(+) Tregs) before and after surgery or chemotherapy in gastric cancer patients.Methods: Twenty-nine stomach cancer patients undergoing chemotherapy after a D2 gastrectomy provided 10 mL peripheral blood samples at each phase of the perioperative period and during chemotherapy. This study also included 29 age-matched healthy donors as a control group. PD-1 expression was detected on lymphocytes, including CD4(+)CD8(+)CD45RO(+), CD4(+)CD45RO(+), and CD8(+)CD45RO(+) lymphocytes as well as regulatory T cells.Results: We observed a significant increase of PD-1 expression on immune subsets and a larger number of FoxP3(+) Tregs in gastric cancer patients (P < 0.05). Following D2 gastrectomy, peripheral lymphocytes PD-1 expression and the number of FoxP3(+) Tregs notably decrease (P < 0.05). However, during postoperative chemotherapy, we only observed a decrease in PD-1 expression on lymphocytes in the CD8(+)CD45RO(+) and CD8(+)CD45RO(+) populations. Additionally, linear correlation analysis indicated a positive correlation between PD-1 expression and the number of CD4(+)CD45RO(+)FoxP3(high) activated Tregs (aTregs) on the total peripheral lymphocytes (r = 0.5622, P < 0.0001).Conclusion: The observed alterations in PD-1 expression and the activation of regulatory T cells during gastric cancer treatment may offer novel insights for future investigations into tumor immune evasion and the clinical application of anti-PD-1 antibodies in gastric cancer.