Identifying the mechanism of anti-colorectal immunity induced by mucoinvasive colonic bacteria

摘要 结直肠癌(CRC)是癌症相关死亡的主要原因，其发病率在年轻人中呈上升趋势。 人民。结直肠肿瘤通常在治疗失败的晚期被发现。免疫疗法是 对许多类型癌症的治疗带来革命性变化，但仅对极少数结直肠癌患者有效。 因此，迫切需要改进结直肠癌的治疗方法。结直肠肿瘤从肠道生长 并与结肠微生物区系相互作用。CRC一直与以下组成的变化有关 促进炎症和肿瘤生长的微生物区系。微生物群还可以塑造结肠T细胞和B细胞 免疫应答，是肿瘤免疫治疗疗效的关键调节因子。使用鼠标模型 结直肠癌(AOM/DSS)我们发现肿瘤后只有一个细菌分类群定植：肝螺杆菌 已经发展起来，导致了肿瘤负担和大小的减少。肝片吸虫的数量也增加了， 结直肠肿瘤旁三级淋巴结构的大小和组织。TLS的存在是 与结直肠癌患者的阳性结果相关，但它们如何提高抗肿瘤免疫并不是 为人所知。肝脏依赖性肿瘤的减少依赖于CD4T细胞和B细胞，而不是CD8T细胞。 大多数肝炎特异性CD4+T细胞分化为卵泡辅助性T细胞(TFH)，并定位于TLS。 重要的是，CD4cre Bcl6flx小鼠不能形成TFH细胞，也无法形成TLS或控制CRC生长， 但是，肝炎特异性的CD4+T细胞的转移完全恢复了抗肿瘤反应。我们的假设 Hhep独特的粘液定植特性导致与B细胞相互作用的抗Hhep TFH的激活 细胞诱导瘤周TLS的形成。然后，结肠TLS作为激活抗肿瘤的平台 CD4+T细胞、NK细胞和B细胞侵袭肿瘤，支持有效的抗肿瘤免疫。我们将测试 这一假设有两个目的。首先，我们将确定基因和行为(如粘液/上皮定植) 与幽门螺杆菌相关的对CRC的控制有关。接下来，我们将关联TLS、TFH和 结直肠癌患者外周血中含有特异性粘液和肿瘤残留细菌的B细胞最后，我们将使用鼠标 确定TLS是否作为更有效地激活抗肿瘤T和B细胞的平台的模型。 总之，我们的建议有可能确定应该针对的关键细菌成分 增强抗肿瘤免疫力和结肠TLS。此外，我们可以确定TLS支持反 肿瘤免疫反应，可用于制定治疗抗结直肠癌的方法。如果成功，我们将 可以确定合理修饰微生物组以提高抗肿瘤免疫力的机制。

Abstract Colorectal cancer (CRC) is a leading cause of cancer-related death and its incidence is on the rise in young people. Colorectal tumors are often detected at late stages where therapy often fails. Immunotherapy is revolutionizing the treatment of many types of cancer but is only effective for a very small subset of CRC patients. Thus, there is a critical need for improved therapies for CRC. Colorectal tumors grow from the intestinal epithelium and interact with the colonic microbiota. CRC has been associated with shifts in the composition of the microbiota that promote inflammation and tumor growth. The microbiota can also shape colonic T and B cell immune responses and is a critical modulator of the efficacy of tumor immunotherapy. Using a mouse model of CRC (AOM/DSS) we show that colonization with a single bacterial taxon: Helicobacter hepaticus, after tumors have already developed, leads to a reduction in tumor burden and size. H. hepaticus also increased the number, size and organization of Tertiary lymphoid structures (TLS) next to colorectal tumors. The presence of TLS is associated with positive outcomes in CRC patients, but how they act to increase anti-tumor immunity is not known. H. hepaticus-dependent tumor reduction depended upon CD4 T cells and B cells but not CD8 T cells. Most H. hepaticus-specific CD4+ T cells differentiated into T Follicular Helper (TFH) cells and localized in TLS. Importantly, CD4cre Bcl6flox mice, that cannot form TFH cells, also failed to either form TLS or control CRC growth, but transfer of H. hepaticus-specific CD4+ T cells completely restored the anti-tumor response. Our hypothesis is that the distinct mucus colonization properties of Hhep leads to activation of anti-Hhep TFH that interact with B cells to induce peri-tumoral TLS formation. Colonic TLS then act as platforms for the activation of anti-tumor CD4+ T cells, NK cells and B cells which invade the tumor to support effective anti-tumor immunity. We will test this hypothesis in two aims. First, we will identify the genes and behavior, (such as mucus/epithelial colonization) associated with Helicobacter-associated control over CRC. Next we will correlate the presence of TLS, TFH and B cells in human CRC patients with specific mucus and tumor resident bacteria. Finally, we will use our mouse models to identify whether TLS serve as platforms for more effective activation of anti-tumor T and B cells. Together, our proposal has the potential to identify the key bacterial components that should be targeted to augment anti-tumor immunity and colonic TLS. Further we may identify mechanisms by which TLS support anti- tumor immune responses which could be used to formulate therapeutic anti-CRC approaches. If successful we could identify mechanisms to rationally modify the microbiome to increase anti-tumor immunity.