Search

Background: Gastric cancer (GC) is the second most common cancer in Japan in terms of incidence and the third most common in terms of deaths. The onset and progression of cancer are generally suppressed by the action of immune cells, which is an inflammatory response. MDSCs are thought to promote cancer progression and invasion by suppressing the function of immune cells, making them potential therapeutic and diagnostic targets. We measured MDSCs in GC patients and observed more monocyte-derived MDSCs in peripheral blood in advanced GC than in early GC. However, granulocyte-derived MDSCs showed no difference in GC progression when markers for classical MDSCs were used. We considered that granulocyte-derived MDSCs were much more abundant than monocyte-derived MDSCs in peripheral blood and were involved in cancer progression. We hypothesized that we had a new granulocyte-derived marker for advanced GC that did not show differences in classical markers, but may have different functions, and aimed to identify a novel subset that may be a therapeutic and diagnostic target. Method: For GC patients, we used heparin blood samples provided by patients who consented to Juntendo University. We analyzed the expression of various cell surface proteins against populations of CD33high, CD66bhigh, and HLA-DRlow as classical markers of MDSCs derived from granulocytes of GC patients using FACS (Melody). MDSCs were isolated by a cell sorter and used for experiments such as RNA-Seq. Novel markers and involved cytokines were quantified in plasma components by cytometric bead array. Result: The chemokine receptors CCR2, CCR5, CXCR4, and CXCR5 were highly expressed in MDSCs of advanced GC patients. The ability to suppress T-cell activation was also found to be stronger in MDSCs with advanced GC. In addition, IL-10 produced by MDSCs was also more abundant in the plasma of patients with advanced GC, as well as chemokines according to chemokine receptors. Conclusion: The high expression of chemokine receptors on MDSCs in advanced GC may indicate that chemokines produced at the cancer site facilitate the migration of MDSCs. These novel subsets of MDSCs found in advanced GC suggest that they may be new therapeutic targets. Citation Format: Suguru Yamauchi, Takumi Iwasawa, Tomoaki Ito, Malcom V. Brock, Tetsu Fukunaga, Hajime Orita, Kazunori Kato. Analysis of MDSCs as a diagnostic and therapeutic target for gastric cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 5958.

The development and progression of cancers are frequently promoted by immunosuppressive cells, such as Treg and myeloid-derived suppressor cells (MDSCs) mediated by various immune checkpoint molecules. Recently, the immune checkpoint inhibitor anti-PD-1 neutralizing antibody has become available for the first-line treatment of gastric cancer (GC) in Japan. However, there is no correlation between PD-1 or PD-L1 expression in Treg or GC tissues and clinical responses to anti-PD-1 antibody. MDSCs are immature myeloid cells thought to suppress immune cell action, but the functional cell surface markers that define MDSCs correlated with cancer progression has not yet been clarified well. In this study, we identified a new subset of potential therapeutic and diagnostic targets for MDSCs in GC patients. Significantly higher levels of immune checkpoint molecules, PD-1 and PD-L1, were expressed on granulocytic MDSCs from advanced than early-stage of GC patients. Interestingly, we found that a subset of G-MDSCs expressed not only PD-1 but also PD-L1 and the pretreatment of G-MDSCs with anti-PD-1 antibody ameliorated T cell responses in vitro. We also found that G-MDSCs isolated from patients treated with anti-PD-1 antibody had a lower ability to suppress T cells. These data indicate that a novel subset of G-MDSCs expressing PD-1 found in advanced GC could be novel therapeutic targets. Citation Format: Takumi Iwasawa, Suguru Yamauchi, Tetsu Fukunaga, Hajime Orita, Kazunori Kato. Novel subset of granulocytic MDSCs as immunosuppressive regulators and therapeutic targets in gastric cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 2889.