Grem1阳性基质细胞调控结直肠癌发展和上皮间质转化及迁移的机制研究

Colorectal cancer (CRC) is one of the most common and deathly cancer types in China and across the world. The mid- and late-stage CRC with the potential to metastasize remains a very low 5-year survival. Acquiring the metastatic phenotype mandates significant crosstalk between tumor cells and their resident tissue microenvironment (TME) where cancer-associated fibroblasts (CAFs) and TGF-b /BMP signalling play an important role. Gremlin-1 (Grem1), an endogenous BMP antagonist, was recently reported labelling intestinal fibroblastic reticular cells. We further validated the lineage of these cells and found that they were truly distant from the classical intestinal fibroblast and rapidly proliferate during epithelial-mesenchymal transition. We hypothesize that these cells may participate in the formation of TME, regulate tumor cell migration and invasion, and hence are vital to the tumor progression. We will incorporate lineage tracing and the diphtheria toxin receptor-mediated conditional mouse model to disclose the fate Grem1+ stromal cells and to reveal its concomitant effect on intestinal physiology and tumor development upon targeted ablation. We will also assess the interaction dynamics of Grem1+ stromal cells and CRC cells, and investigate the underlying cellular and molecular determinants of invasion and metastasis by exploiting transplantation and organoid culture technique. This project ultimately aims to identify new CRC markers and drug target via human CRC specimen and patient-derived xenograft model, which would expectantly provide a mechanistic and pre-clinical foundation for the development of novel stroma-targeted therapies for patients with late-stage CRC.

结直肠癌是我国和全球最常见和致死的癌症之一，中晚期转移是制约生存率的主要原因。癌相关成纤维细胞和TGF-b/BMP通路等肿瘤微环境成分对癌细胞获得转移表型具有重要调控作用。最近报道BMP拮抗剂Grem1特异标记肠成纤维网状细胞，我们鉴定它是一类明显有别于典型成纤维细胞的新谱系，发现它随肠癌细胞上皮间质转化的启动而迅速增殖。我们假设此类细胞参与肿瘤微环境形成，调控肿瘤细胞迁移和侵袭，并与肿瘤进程密切相关。本项目将巧妙结合谱系追踪和白喉毒素受体条件性细胞剔除模式小鼠，既揭示Grem1+基质细胞的命运图谱，又阐明特异性清除后对正常生理和肿瘤进展的影响。我们还将利用肿瘤移植和类器官模型探索Grem1+基质细胞与肿瘤细胞相互作用调控肿瘤发生、发展的分子机制，并结合临床样本和人源肿瘤异种移植模型筛选新标记物和药靶。本项目将为以靶向转移前肿瘤基质为策略的晚期肠癌治疗提供新机理和临床前期证据。

结直肠癌（CRC）位列最常见和致死的癌症之一，中晚期转移是制约生存率的主要原因。癌相关成纤维细胞（CAF）和TGF-β通路等肿瘤微环境成分对癌细胞获得转移表型具有关键调控作用。最近报道BMP拮抗剂GREM1分子特异标记的一类基质细胞促进CRC进展，但具体机制不详。本研究首先通过免疫荧光/组化和RNA scope 等染色手段观察到，在野生型小鼠肠组织以及CRC早中期临床样本，GREM1沿上皮细胞周围分布，并只在基质细胞表达。然而，Grem1+ CAF谱系显著区别于α-SMA+ 肠肌成纤维细胞，其浸润程度随CRC进展递增。意外的是，在IV期CRC临床样本组织，我们还发现了Grem1+肿瘤细胞。由此，提出新假说，Grem1+ CAF或利用紧密的浸润优势，激活肿瘤细胞的某些信号通路，进而促进肿瘤内源性Grem1的表达。通过基因突变、免疫共沉淀、质谱分析和生物膜层干涉等技术，我们证实CAF来源的分泌蛋白GREM1是CRC细胞膜受体ACVR1C的一种新型配体。最后，通过大量动物和细胞实验，我们阐明旁分泌蛋白GREM1通过ACVR1C-Smad2/3信号通路上调CRC细胞EMT标志基因SNAI1和内源性Grem1的转录，从而促进CRC细胞干性、恶性进程和远端转移。.综上，我们揭示Grem1+ CAF逐步聚集、包围并浸润CRC细胞，最终通过Grem1/ACVR1C/SAMD信号轴促进EMT调控因子和内源GREM1分子表达的全过程，为GREM1作为潜在CRC诊断标志物和分子药靶提供了重要的数据支撑和理论依据。旁分泌和自分泌的Grem1分子叠加显著加剧肿瘤恶性进程。越来越多的证据表明GREM1不再局限于单纯的BMP拮抗剂，而可以独立行使细胞因子的功能。因此，我们正在开发阻断Grem1/ACVR1C轴的小分子先导药物，相信这将为基于靶向转移前肿瘤及其基质为策略的晚期肠癌治疗提供应用价值。