Claudin18.2-positive gastric cancer-specific changes in neoadjuvant chemotherapy-driven immunosuppressive tumor microenvironment: Cellular and Molecular Biology

Background: Claudin 18 isoform 2 (CLDN18.2) is a potential therapeutic target in gastric cancer (GC). However, combining chemotherapy with anti-CLDN18.2 antibodies has shown limited efficacy in CLDN18.2-positive GC, and chemotherapy-induced changes in the tumor microenvironment (TME) remain unclear. Methods: This study analyzed 37 GC samples, including 11 CLDN18.2-positive cases, using single-cell RNA sequencing and multiplex immunofluorescence to assess chemotherapy-driven TME changes in CLDN18.2-positive GC. Results: In chemotherapy-treated CLDN18.2-positive GC, cytotoxic natural killer (NK) cells displayed antibody-dependent cytotoxicity (ADCC)-related genes at lower levels than in untreated CLDN18.2-positive GC, while regulatory T cells (Tregs) and tumor-associated macrophages (TAMs) showed TGFB1 expression at higher levels. Additionally, NK cells, Tregs, and TAMs were more abundant in chemotherapy-treated than untreated CLDN18.2-positive GC. These chemotherapy-induced changes were absent in CLDN18.2-negative GC. Cell-cell interaction analysis identified unique interactions in chemotherapy-treated CLDN18.2-positive GC, including CCL5-CCR5 signaling between cytotoxic NK cells (Sender) and effector Tregs (Receptor) and TGFB1-TGFBR signaling between effector Tregs (Sender) and TAMs (Receptor). Cytotoxic NK cells expressed CCL5 at higher levels, CCR5-positive Tregs were more prevalent, and TAMs exhibited higher TGF-β receptor signature scores in chemotherapy-treated than untreated CLDN18.2-positive GC. Conclusions: Our findings indicate that chemotherapy can drive immunosuppressive TME modifications specific to CLDN18.2-positive GC.