DataSheet_5_A combined analysis of bulk and single-cell sequencing data reveals that depleted extracellular matrix and enhanced immune processes co-contribute to fluorouracil beneficial responses in gastric cancer.xlsx

Fluorouracil, also known as 5-FU, is one of the most commonly used chemotherapy drugs in the treatment of advanced gastric cancer (GC). Whereas, the presence of innate or acquired resistance largely limits its survival benefit in GC patients. Although accumulated studies have demonstrated the involvement of tumor microenvironments (TMEs) in chemo-resistance induction, so far little is known about the relevance of GC TMEs in 5-FU resistance. To this end, in this study, we investigated the relationship between TME features and 5-FU responses in GC patients using a combined analysis involving both bulk sequencing data from the TCGA database and single-cell RNA sequencing data from the GEO database. We found that depleted extracellular matrix (ECM) components such as capillary/stroma cells and enhanced immune processes such as increased number of M1 polarized macrophages/Memory T cells/Natural Killer T cells/B cells and decreased number of regulatory T cells are two important features relating to 5-FU beneficial responses in GC patients, especially in diffuse-type patients. We further validated these two features in the tumor tissues of 5-FU-benefit GC patients using immunofluorescence staining experiments. Based on this finding, we also established a Pro (63 genes) and Con (199 genes) gene cohort that could predict 5-FU responses in GC with an AUC (area under curve) score of 0.90 in diffuse-type GC patients, and further proved the partial applicability of this gene panel pan-cancer-wide. Moreover, we identified possible communications mediated by heparanase and galectin-1 which could regulate ECM remodeling and tumor immune microenvironment (TIME) reshaping. Altogether, these findings deciphered the relationship between GC TMEs and 5-FU resistance for the first time, as well as provided potential therapeutic targets and predicting rationale to overcome this chemo-resistance, which could shed some light on developing novel precision treatment strategies in clinical practice.

氟尿嘧啶（Fluorouracil，俗称5-FU）是临床治疗晚期胃癌（gastric cancer, GC）最常用的化疗药物之一。然而，先天或获得性耐药的存在极大限制了胃癌患者从该治疗中获得的生存获益。既往大量研究已证实肿瘤微环境（tumor microenvironments, TMEs）参与化疗耐药的诱导，但截至目前，关于胃癌肿瘤微环境与5-FU耐药之间的相关性仍鲜有报道。为此，本研究通过联合分析TCGA（The Cancer Genome Atlas）数据库的批量测序数据与GEO（Gene Expression Omnibus）数据库的单细胞RNA测序数据，探讨了胃癌患者肿瘤微环境特征与5-FU治疗应答之间的关联。研究结果显示，细胞外基质（extracellular matrix, ECM）成分耗竭（如毛细血管/基质细胞减少）以及免疫进程增强（如M1型极化巨噬细胞、记忆T细胞、自然杀伤T细胞、B细胞数量增多，调节性T细胞数量减少）这两大特征，与胃癌患者（尤其是弥漫型胃癌患者）对5-FU的良好治疗应答密切相关。本研究进一步通过免疫荧光染色实验，在5-FU治疗获益的胃癌患者肿瘤组织中验证了这两大特征。基于上述发现，本研究构建了包含63个有利基因与199个不利基因的基因集，该基因集可预测胃癌患者的5-FU治疗应答，在弥漫型胃癌患者中的受试者工作特征曲线下面积（area under curve, AUC）达0.90，并证实该基因集在泛癌范围内具有部分适用性。此外，本研究还鉴定出可能由乙酰肝素酶（heparanase）与半乳糖凝集素-1（galectin-1）介导的细胞通讯，二者可调控细胞外基质重塑与肿瘤免疫微环境（tumor immune microenvironment, TIME）重塑。综上，本研究首次阐明了胃癌肿瘤微环境与5-FU耐药之间的关联，并为克服化疗耐药提供了潜在治疗靶点与预测依据，可为临床开发新型精准治疗策略提供新思路。