基质硬度引起的肿瘤相关巨噬细胞脂代谢重塑促进胃癌生长的机制研究

The extracellular matrix stiffness has been attracting attention for its role in tumor progression. However, the effects of matrix stiffness on tumor-associated macrophages (TAMs) phenotype activation and metabolic adaptation still remain unclear. In addition, how the lipid metabolism of TAMs affects its biological function has yet to be elucidated. Through literature review and preliminary experimental results, we infer that higher matrix stiffness may elicit the immunosuppressive form of TAMs activation, enhance the lipolysis and phospholipid metabolism, as well as promote release of free fatty acid and prostaglandin E2. The lipid metabolism orchestration of TAMs not only contributes to the activation and maintenance of its immunosuppressive phenotype, but also affects the regulation of TAMs on the biological behavior of gastric cancer cells. This project aims to clarify the molecular mechanism under TAMs promoting gastric cancer growth via their lipid metabolism reprogramming caused by matrix stiffness, through in vitro production of polyacrylamide hydrogel substrates to model the extracellular matrix, as well as by conducting cell function experiments, molecular biological experiments and constructing animal models. Finally, this project would provide a brand new molecular basis for the tumor promoting role of TAMs in terms of mechanical environment and cellular energy metabolism.

细胞外基质的硬度在肿瘤恶性进程中的作用渐受重视。然而，尚无研究涉及基质硬度对肿瘤相关巨噬细胞（TAMs）表型与代谢模式的影响。另外，TAMs的脂代谢对其发挥生物学功能的作用亦有待阐明。通过文献检索与前期预实验结果，我们推测基质硬度的增加可促使TAMs表型向免疫抑制型激活，并增强其脂解代谢与磷脂代谢，促进游离脂肪酸与前列腺素PGE2的释放。而TAMs的脂代谢重塑既有助于其免疫抑制表型的激活与维持，也影响着TAMs对胃癌细胞生物学行为的调控。因此，本项目旨在探讨基质硬度引起的TAMs脂代谢重塑促进胃癌生长的机制，通过体外制备不同硬度的聚丙烯酰胺水凝胶基底模拟细胞外基质，观察不同梯度基质硬度对TAMs的表型、代谢模式及其促胃癌生长作用的影响，阐明具体的信号通路，并在动物模型中予以验证，以期从力学微环境与细胞代谢角度为TAMs促癌的机制提供新的分子生物学依据与潜在的治疗靶点。

贝伐单抗在晚期肠癌的综合治疗中有重要地位，然而患者对贝伐单抗治疗产生抵抗的机制尚未阐明。本项目中，我们从肿瘤基质硬度这一物理特性入手，通过临床、动物与细胞模型进行系列研究发现：1）肠癌患者肿瘤基质硬度签名表达升高预示不良预后，且5-FU辅助化疗无法为这类高基质硬度签名表达患者带来生存获益。接受化疗联合贝伐单抗治疗的肠癌肝转移队列中，治疗非应答的患者其肝转移灶基线基质硬度分布、基质硬度基因签名及脂肪酸代谢激活均较应答者明显升高。然而，仅有在肝星状细胞高度浸润前提下，基质硬度基因签名与脂肪酸氧化代谢激活程度呈显著正相关。2）体外通过聚丙烯酰胺水凝胶模拟不同硬度的基质发现，肠癌细胞单独培养时其脂肪酸氧化激活水平不受基质硬度影响，仅有将肠癌细胞与星状细胞共培养时前者的脂肪酸代谢水平会在高硬度基底培养条件下升高，提示基质硬度对肠癌细胞脂肪酸氧化代谢的激活需要肝星状细胞作为中介。3）高基质硬度通过FAK-YAP通路激活肝星状细胞的脂解代谢，后者的分泌游离脂肪酸一方面可直接激活肠癌细胞脂肪酸氧化代谢，亦可作为代谢底物被肠癌细胞吸收使用。4）动物模型显示，贝伐单抗可呈剂量依赖性重构肠癌肝转移灶的基质。大剂量贝伐单抗处理组而非低剂量贝伐单抗以及单用化疗组小鼠肠癌肝转移灶中的胶原纤维浸润明显增多，同时，脂肪酸氧化关键酶表达水平也明显上调，且该上调可被联合透明质酸酶所抑制。此外，贝伐单抗对病灶基质的重构及脂肪酸氧化代谢的调节作用仅于肠癌细胞与肝星状细胞混合后所成的皮下瘤存在，进一步证实体外模型的研究结论。综上，本项目我们从肿瘤物理微环境这一视角首次解析了贝伐单抗治疗抵抗的触发原因与具体分子机制，为开发可逆转耐药的干预靶点及策略提供新思路。