PO.TB10.14 · 肿瘤生物学
肠道专性厌氧菌驱动胰腺癌转移
Obligate anaerobes in the gut drive pancreatic cancer metastasis
作者与单位 Authors & Affiliations
摘要 Abstract
中文摘要
引言：肿瘤微生物群是胃肠道癌症结局的有力预测因子。然而，我们鉴定癌症进展的细菌分子驱动因素的努力受到以下阻碍：1）缺乏高效的厌氧细菌培养系统；2）>90%的人类肠道微生物群为厌氧菌。这一困境限制了我们在肿瘤微生物群研究中开展机制研究的能力。为填补这一空白，我们试图通过利用一个经整理的、可培养的人类肠道微生物群文库，建立一个新的实验系统来繁殖转移相关的肿瘤微生物群。方法：我们通过经口灌胃向无菌C57BL/6小鼠依次施用经整理的人类肠道微生物群文库，建立了一个悉生（gnotobiotic）系统。随后，对小鼠进行同基因KPC胰腺癌细胞的胰腺内注射。对肝转移灶、原发性胰腺癌以及十二指肠及其相关细菌进行16S测序和基于直接培养的繁殖。结果：为验证我们的实验平台在预期低生物量情况下鉴定细菌物种的可行性，我们通过向野生型C57BL/6小鼠胰腺内注射KPC癌细胞系开展了概念验证实验。对肝转移灶、原发性胰腺肿瘤和十二指肠进行16S测序和直接培养。基于Bray-Curtis相异度矩阵的PCoA图揭示了荷瘤小鼠样本与相应的假手术非荷瘤样本之间的明显差异，且这种差异与采样部位无关，提示荷瘤状态具有全身性影响。梭菌属（Clostridium）物种在原发性胰腺肿瘤和肝转移样本中特别富集，提示缺氧肿瘤和缺氧肝微环境中存在有利于专性厌氧菌的生物学压力。KPC癌细胞与梭菌属物种的共注射使肝转移增加了10倍以上。此外，梭菌条件培养基也增强了肝转移，提示细菌来源的可溶性因子在调节转移中发挥关键作用。结论：所观察到的转移性胰腺癌细胞与专性厌氧菌之间的共生关系，值得在其他癌症中进一步寻找类似的被利用的细菌-癌症相互作用。我们发现的促转移细菌来源可溶性因子，为通过阻断其与宿主细胞的相互作用来开发细菌来源、但不含活微生物、可扩展的治疗方法铺平了道路。总之，我们鉴定了强力驱动癌症转移的新型细菌来源可溶性因子。
查看英文原文 English abstract
Introduction: Tumoral microbiota is a strong predictor of gastrointestinal cancer outcome. However, our efforts to identify bacterial molecular drivers of cancer progression are hindered by 1) the lack of an efficient anaerobic bacterial culturing system and 2) the fact that >90% of the human gut microbiota are anaerobes. This predicament limits our capability to conduct mechanistic studies in tumor microbiota research. To fill this gap, we sought to establish a novel experimental system to propagate metastasis-associated tumoral microbiota by leveraging a curated, culturable human gut microbiota library. Methods: We established a gnotobiotic system by sequentially administering the curated human gut microbiota library via oral gavage in germ-free C57BL/6 mice. Subsequently, the mice underwent intrapancreatic injections of syngeneic KPC pancreatic cancer cells. Liver metastatic foci, primary pancreatic cancer, and the duodenum with their associated bacteria were subject to 16s sequencing and direct culture-based propagation. Results: To validate the feasibility of our experimental platform in identifying bacterial species despite the expected low biomass, we conducted proof-of-concept experiments by intrapancreatically injecting KPC cancer cell lines in wild-type C57BL/6 mice. Liver metastatic foci, primary pancreas tumors, and the duodenum were subject to 16S sequencing and direct culture. A Bray-Curtis dissimilarity matrix-based PCoA plot revealed apparent dissimilarity between tumor-bearing mouse samples and corresponding mock-surgery non-tumor-bearing samples, in a sample-site-agnostic manner, suggesting a systemic impact of the tumor-bearing state. Clostridium species were particularly enriched in primary pancreatic tumors and liver metastatic samples, suggesting biological pressure in hypoxic tumors and the hypoxic liver microenvironment that favors obligate anaerobes. Co-injections of KPC cancer cells and Clostridium species promoted liver metastasis more than 10-fold. Moreover, Clostridium-conditioned media also enhanced liver metastasis, suggesting a critical role for bacteria-derived soluble factors in regulating metastasis. Conclusion: The observed symbiosis between metastasizing pancreatic cancer cells and obligate anaerobes warrants further searches of similar co-opted bacteria-cancer interactions in other cancers. Our discovery of pro-metastatic bacteria-derived soluble factors paves the way for developing bacteria-derived, yet live microorganism-free, scalable therapeutics by blocking their interactions with host cells. In summary, we identified novel bacteria-derived soluble factors that strongly drive cancer metastasis.
利益披露 Disclosure
N. Yamaguchi, None.