Rspo1/Slit2诱导体内肠干细胞保护机体免受放射线、化学物伤害的机制和应用研究

How to protect essential organs during radiological and chemical emergencies or oncologic chemoradiotherapy remains clinically challenging. Wnt/beta-catenin signaling maintains intestinal stem cells (ISCs) and functions as a main driving force for intestinal homeostasis. The Slit family of guidance cues interacts with the Roundabout (Robo) family of single-span transmembrane receptors for modulation of cell migration. We recently reported that Slit2 acted co-operatively with R-spondin 1 (Rspo1; a Wnt agonist) to promote proliferation of Robo1+ ISC-derived enteroids and to enhance gut injury repair. Parenteral administration of recombinant Rspo1 plus Slit2 (rRspo1/rSlit2) induced Robo1+ ISCs, mitigated gut impairment and protected animals from death, without concomitantly decreasing tumor sensitivity to lethal doses of chemoradiotherapy. To extend the rates of in vivo serum half-life to ~5 days, we generated recombinant human Rspo1 and Slit2 fused with the Fc segment of human IgG4 (rRspo1-Fc and rSlit2-Fc). Most excitingly, systemic administration of rRspo1-Fc/rSlit2-Fc protected mice from death in a Robo1-dependent manner, even when given 24 hours after lethal doses of radiation. In combination with chemoradiotherapy, the regimen of rRspo1-Fc/rSlit2-Fc also improved overall survival in mice bearing Robo1- metastatic triple-negative breast cancer. We thus hypothesized that by promoting gut injury repair, rRspo1-Fc/rSlit2-Fc not only counteract chemoradiation-induced mortality and organ failure, but also enhances host tolerance to aggressive chemoradiotherapy for ‘subtractive’ targeting of Robo1- metastatic triple-negative breast cancer. In this proposal, we will examine the biologic significance of Lrp5/6 in ISCs for Rspo1/Slit2-mediated repair of chemoradiation-induced gut injury. We will also examine how to optimally protect Robo1+ ISCs, but not Robo1- metastatic triple-negative breast cancer cells, by Rspo1/Slit2 during chemoradiotherapy.

如何有效保护放射线、化学物泄漏事故或肿瘤放化疗所引起的人体重要器官损伤，在临床应用上目前仍然是一个严峻的挑战。我们最近发现Slit2与Rspo1 协同作用，共同促进Robo1阳性的肠干细胞增殖和肠绒毛发育并促进肠的损伤修复，并能够使小鼠在受到致死剂量放化疗处理下仍能够存活，同时该蛋白注射并不影响肿瘤对放化疗的敏感性。我们依此提出科学设想：Rspo1/Slit2蛋白与放化疗联合治疗肿瘤，Rspo1/Slit2通过促进肠的损伤修复，减低放化疗副作用，增强病人对更高剂量放化疗的耐受，从而使肿瘤得到更有效的治疗。在本课题里，我们将利用乳腺癌肿瘤转移模型进一步研究如何将Rspo1/Slit2与放化疗有效结合，使Rspo1/Slit2更好的保护Robo1阳性的肠干细胞而不保护转移了的Robo1阴性的乳腺癌细胞，延长小鼠生存率并使肿瘤治疗达到更好的效果。

本项目主要探讨诱导内源组织干细胞促进组织损伤修复的应用和调控机制。在前期研究基础上，本项目深入研究了Rspo1/Slit2/Robo1信号通路调控肠组织干细胞活性促进肠道损伤修复的下游机制，进一步发现Rspo1/Slit2/Robo1信号通路可调控造血干细胞及皮肤干细胞再生能力，并将其应用于联合放化疗治疗肿瘤及应对射线或有害物质对机体造成的损伤，为组织干细胞在组织损伤修复相关疾病的应用提供了理论依据和相关靶点。鉴于组织干细胞与肿瘤干细胞的共性存在，本项目同时研究了结直肠癌、胃癌的发生发展调控机制，为区分组织干细胞与肿瘤干细胞提供了理论依据，为肿瘤治疗提供了新靶点。这些研究的部分研究结果发表于Theranostics（2018）、JECCR（2018）、BBRC（2019）等优秀学术期刊。本项目的一大研究特色是在对肝组织干细胞及肝纤维化的研究过程中创新性地发现诱导内源肝组织干细胞治疗肝纤维化(Nature Commun， 2017)，拓展了成体干细胞的应用范围和应用方法，为肝纤维化治疗提供了新策略，成功地进入肝纤维化研究领域;在对肝纤维化的深入研究中首次提出汇管区血管新生和肝血窦毛细血管化在肝纤维化发生中发挥不同作用的新观念，鉴定出孤儿受体 Tie1 的功能配体 LECT2，揭示了肝纤维化和血管新生的新机制，为肝纤维化肝硬化提供了新的血液诊断分子标志物和治疗靶点(Cell， 2019)。. 在本项目资助下，项目负责人作为通讯作者（含共同通讯）在Cell、Nature Communications、Theranostics、JECCR、BBRC等国际学术期刊发表5篇SCI论文；作为第一发明人申请国内专利4件，国际PCT专利1件。