The intestinal microbiota determines immune responses against extraintestinal antigens, including tumor-associated antigens. Indeed, depletion or gross perturbation of the microbiota undermines the efficacy of cancer immunotherapy, thereby compromising the clinical outcome of cancer patients. In this review, we discuss the long-distance effects of the gut microbiota and the mechanisms governing antitumor immunity, such as the translocation of intestinal microbes into tumors, migration of leukocyte populations from the gut to the rest of the body, including tumors, as well as immunomodulatory microbial products and metabolites. The relationship between these pathways is incompletely understood, in particular the significance of the tumor microbiota with respect to the identification of host and/or microbial products that regulate the egress of bacteria and immunocytes toward tumor beds.

肠道微生物群决定针对肠外抗原（包括肿瘤相关抗原）的免疫反应。事实上，微生物群的耗竭或严重扰动会破坏癌症免疫疗法的功效，从而损害癌症患者的临床结果。在这篇综述中，我们讨论了肠道微生物群的远距离影响以及控制抗肿瘤免疫的机制，例如肠道微生物易位到肿瘤中、白细胞群从肠道迁移到身体其他部位（包括肿瘤），以及免疫调节微生物产品和代谢物。这些途径之间的关系尚不完全清楚，特别是肿瘤微生物群对于识别调节细菌和免疫细胞向肿瘤床流出的宿主和/或微生物产物的重要性。