乳腺癌已成为世界上首要的癌症，而肠道菌群可能与之密切相关。地理位置也对人类肠道菌群有重要影响。我们在中国的热带地区——海南省，进行了首项乳腺癌患者和非乳腺癌患者肠道菌群的研究。同时，首次使用Pacbio平台进行了基于第三代测序的16S全长测序，对粪便微生物DNA进行了物种多样性分析和差异物种分析，并推断其功能基因组成并进行了功能差异分析。在海南省的两组之间的α多样性方面存在显著差异。通过物种组成差异分析，在门级别上，Bacteroidales（P=0.006）和Firmicutes（P=0.002）在两组之间有差异，并且在属级别上筛选出了与乳腺癌相关的17种差异物种，如Bacteroides。根据乳腺癌患者的ER水平、PR水平、HER2状态、Ki67指数和组织学分级等五种分组方法，分别筛选出了4、1、9、6、5种差异微生物，共计25种（所有亚组的P<0.05）。功能预测和差异分析揭示了两组微生物之间的两种功能代谢存在显著差异（P<0.05）。这些结果表明，乳腺癌与肠道菌群的组成和功能变化有关。这些菌群和功能差异可能成为乳腺癌的诊断和治疗的生物标志物或新的靶点。版权所有 © 2023 Elsevier Ltd.发表。

Breast cancer has become the number one cancer in the world, and intestinal flora may be closely linked to it. Geographic location also has an important impact on human intestinal flora. We conducted the first study on the intestinal flora of breast cancer patients and non-breast cancer patients in a tropical region - Hainan Province in China. At the same time, Pacbio platform based on third-generation sequencing was used for the first time to conduct 16 S full length sequencing of fecal microorganism DNA. We completed the species diversity analysis and differential species analysis of the intestinal flora between the two groups, inferred their functional genetic composition and performed functional difference analysis. There were statistically significant differences in alpha diversity between the two groups in Hainan Province. By species composition difference analysis, at the phylum level, Bacteroidales（P = 0.006）and Firmicutes（P = 0.002） was differed between the two groups, and at the genus level, 17 breast cancer-related differential species such as Bacteroides were screened. According to the five grouping methods including ER level, PR level, HER2 status, Ki67 index and histological grade of breast cancer patients, 4, 1, 9, 6, 5 differential microbiota were screened out respectively, which were in total 25（P < 0.05 for all subgroups）. The functional prediction and difference analysis revealed two functional metabolisms with significant differences between the two groups of microbes（P < 0.05）. These results suggest that breast cancer is associated with changes in the composition and function of intestinal flora. These microflora and functional differences may become biomarkers or new targets for diagnosis and treatment of breast cancer.Copyright © 2023. Published by Elsevier Ltd.