Background/Objectives: In gastric cancer, only a subset of patients benefit clinically from neoadjuvant chemoimmunotherapy, underscoring the need for robust biomarkers that can predict treatment responses and guide personalized immunotherapy. This study aimed to characterize the immune microenvironment of gastric tumors and identify predictive markers associated with therapeutic efficacy. Methods: We prospectively enrolled 16 patients with histologically confirmed, PD-L1–positive (CPS ≥ 1) gastric adenocarcinoma (T2–4N0–1M0). All patients received eight cycles of FLOT chemotherapy combined with pembrolizumab. Treatment response was assessed by Mandard tumor regression grading. Spatial transcriptomic profiling (10x Genomics Visium) and multiplex immunofluorescence were used to evaluate tumor-infiltrating immune cell subsets and PD-1 expression at baseline and after treatment. Results: Transcriptomic analysis differentiated the immune landscapes of responders from non-responders. Responders exhibited elevated expression ofIL1B,CXCL5,HMGB1, andIFNGR2, indicative of an inflamed tumor microenvironment and type I/II interferon signaling. In contrast, non-responders demonstrated upregulation of immunosuppressive genes such asLGALS3,IDO1, andCD55, along with enrichment in oxidative phosphorylation and antigen presentation pathways. Multiplex immunofluorescence confirmed a higher density of FoxP3+regulatory T cells in non-responders (median 5.36% vs. 2.41%;p= 0.0032). Notably, PD-1+CD8+T cell and PD-1+FoxP3+Treg frequencies were significantly elevated in non-responders, suggesting that PD-1 expression within cytotoxic and regulatory compartments may contribute to immune evasion. No substantial differences were observed in PD-L1 CPS or PD-1+B cells and PD-1+macrophages. Conclusions: Our findings identify PD-1+CD8+T cells and PD-1+FoxP3+Tregs as potential biomarkers of resistance to neoadjuvant chemoimmunotherapy in gastric cancer. Transcriptional programs centered on IL1B/CXCL5 and LGALS3/IDO1 define distinct immune phenotypes that may guide future combination strategies targeting both effector and suppressive arms of the tumor immune response.
背景/目的：在胃癌治疗中，仅部分患者能从新辅助化疗免疫治疗中临床获益，这凸显了需要可靠的生物标志物来预测治疗反应并指导个体化免疫治疗。本研究旨在描述胃癌肿瘤免疫微环境特征，并识别与治疗效果相关的预测性标志物。方法：我们前瞻性入组了16例经组织学确诊、PD-L1阳性（CPS≥1）的胃腺癌患者（T2-4N0-1M0）。所有患者均接受八个周期的FLOT化疗联合帕博利珠单抗治疗。治疗反应通过Mandard肿瘤退缩分级进行评估。采用空间转录组分析（10x Genomics Visium）和多重免疫荧光技术，评估治疗前和治疗后肿瘤浸润免疫细胞亚群及PD-1表达情况。结果：转录组分析区分了应答者与非应答者的免疫景观。应答者表现出IL1B、CXCL5、HMGB1和IFNGR2表达升高，提示存在炎症性肿瘤微环境和I/II型干扰素信号通路激活。相比之下，非应答者则表现出免疫抑制基因（如LGALS3、IDO1和CD55）的上调，以及氧化磷酸化和抗原呈递通路的富集。多重免疫荧光证实，非应答者中FoxP3+调节性T细胞密度更高（中位数5.36% vs. 2.41%；p=0.0032）。值得注意的是，非应答者中PD-1+CD8+T细胞和PD-1+FoxP3+Treg的频率显著升高，表明细胞毒性和调节性免疫区室内的PD-1表达可能促进免疫逃逸。在PD-L1 CPS或PD-1+B细胞和PD-1+巨噬细胞方面未观察到显著差异。结论：我们的研究结果确定PD-1+CD8+T细胞和PD-1+FoxP3+Treg是胃癌新辅助化疗免疫治疗耐药的潜在生物标志物。以IL1B/CXCL5和LGALS3/IDO1为核心的转录程序定义了不同的免疫表型，这可能为未来靶向肿瘤免疫反应效应和抑制环节的联合策略提供指导。
肿瘤(癌症)患者之家