腹膜转移（GCPM）的胃癌患者的临床轨迹迅速恶化，其特点是治疗耐药和生存率低下，特别是在发生恶性腹水后。然而，治疗过程中腹膜微环境（PME）内复杂的动态仍然很大程度上未知。来自原发肿瘤（PT）、腹膜转移瘤（PM）的匹配样本以及配对的治疗前和化疗/免疫治疗后（抗PD） -1/PD-L1) 进展恶性腹水样本，收集自 48 名患者。这些样本进行了单细胞 RNA 测序 (n = 30)、多重免疫荧光 (n = 30) 和空间转录组学 (n = 3)。此外，还对 1 期临床试验（n = 20，NCT03710265）和内部免疫治疗队列（n = 499）进行事后分析以验证研究结果。追踪上皮细胞的进化轨迹揭示了终末差异 MUC1 癌症细胞具有较高的上皮间质转化潜力，并且它们与成纤维细胞和内皮细胞在空间上接近，与不良预后相关。与 PT 和 PM 相比，在腹水中观察到巨噬细胞浸润显着扩大，表现出最高的促血管生成活性。此外，在治疗失败的病例中，较高的 C1Q 巨噬细胞浸润与显着较低的 GZMA T 淋巴细胞浸润相关，这可能是由 LGALS9-CD45 和 SPP1-CD44 配体-受体相互作用介导的。在化疗耐药组中，发现 C1Q 巨噬细胞和成纤维细胞之间通过补体激活途径密切相互作用。在表现出免疫抵抗的组中，在 MUC1 癌细胞中检测到 TGF-β 产生活性增强，并且它们倾向于通过 GDF15-TGF-βR2 轴与 C1Q 巨噬细胞相互作用。最终，事后分析表明，对于诊断时出现 GCPM 的患者，联合靶向 TGF-β 和 PDL1 通路可能比单独的抗 PD-1/PD-L1 治疗带来更好的临床益处。我们的研究结果阐明了细胞分化PME内的轨迹和关键耐药特征，有助于探索GCPM治疗的有效靶点。MUC1癌细胞具有较高的上皮间质转化潜力，并与成纤维细胞和内皮细胞表现出空间接近性，构成了胃癌腹膜转移的驱动力（GCPM）。在治疗失败的病例中，腹膜微环境中较高的 C1Q 巨噬细胞浸润与显着较低的 GZMA T 淋巴细胞浸润相关。对于诊断时出现 GCPM 的患者来说，联合靶向 TGF-β 和 PDL1 通路可能比单独的抗 PD-1/PD-L1 治疗具有更好的临床益处。© 2024 作者。约翰·威利出版的《临床与转化医学》

Gastric cancer patients with peritoneal metastasis (GCPM) experience a rapidly deteriorating clinical trajectory characterized by therapeutic resistance and dismal survival, particularly following the development of malignant ascites. However, the intricate dynamics within the peritoneal microenvironment (PME) during the treatment process remain largely unknown.Matched samples from primary tumours (PT), peritoneal metastases (PM), and paired pre-treatment and post-chemo/immunotherapy (anti-PD-1/PD-L1) progression malignant ascites samples, were collected from 48 patients. These samples were subjected to single-cell RNA sequencing (n = 30), multiplex immunofluorescence (n = 30), and spatial transcriptomics (n = 3). Furthermore, post hoc analyses of a phase 1 clinical trial (n = 20, NCT03710265) and an in-house immunotherapy cohort (n = 499) were conducted to validate the findings.Tracing the evolutionary trajectory of epithelial cells unveiled the terminally differentially MUC1+ cancer cells with a high epithelial-to-mesenchymal transition potential, and they demonstrated spatial proximity with fibroblasts and endothelial cells, correlating with poor prognosis. A significant expansion of macrophage infiltrates, which exhibited the highest proangiogenic activity, was observed in the ascites compared with PT and PM. Besides, higher C1Q+ macrophage infiltrates correlated with significantly lower GZMA+ T-lymphocyte infiltrates in therapeutic failure cases, potentially mediated by the LGALS9-CD45 and SPP1-CD44 ligand-receptor interactions. In the chemoresistant group, intimate interactions between C1Q+ macrophages and fibroblasts through the complement activation pathway were found. In the group demonstrating immunoresistance, heightened TGF-β production activity was detected in MUC1+ cancer cells, and they were skewed to interplay with C1Q+ macrophages through the GDF15-TGF-βR2 axis. Ultimately, post hoc analyses indicated that co-targeting TGF-β and PDL1 pathways may confer superior clinical benefits than sole anti-PD-1/PD-L1 therapy for patients presenting with GCPM at the time of diagnosis.Our findings elucidated the cellular differentiation trajectories and crucial drug resistance features within PME, facilitating the exploration of effective targets for GCPM treatment.MUC1+ cancer cells with a high epithelial-to-mesenchymal transition potential and exhibiting spatial proximity to fibroblasts and endothelial cells constitute the driving force of gastric cancer peritoneal metastasis (GCPM). Higher C1Q+ macrophage infiltrates correlated with significantly lower GZMA+ T-lymphocyte infiltrates within the peritoneal microenvironment in therapeutic failure cases. Co-targeting TGF-β and PDL1 pathways may confer superior clinical benefits than sole anti-PD-1/PD-L1 therapy for patients presenting with GCPM at diagnosis.© 2024 The Author(s). Clinical and Translational Medicine published by John Wiley & Sons Australia, Ltd on behalf of Shanghai Institute of Clinical Bioinformatics.