A study examined how changes in gut bacteria and related metabolites contribute to the development of colorectal cancer (CRC). Researchers analyzed intestinal tissue samples from 110 patients across four stages: normal control, low-grade precancerous lesions, high-grade precancerous lesions, and confirmed tumors.
As disease severity increased, bacterial diversity steadily declined. Beneficial bacteria that produce butyrate—such as Lachnospiraceae, Faecalibacterium, and Blautia—became less abundant. In contrast, potentially harmful bacteria increased. Tumor samples were dominated by Enterococcus and Moryella, while high-grade precancerous tissue showed high levels of Fusobacterium.
Metabolic changes were also observed. Certain bile acids increased in advanced stages and were linked to the presence of Enterococcus. At the same time, protective short-chain fatty acids (such as acetate and butyrate) decreased, reflecting the loss of beneficial bacteria. The study suggests that combining microbial and bile acid markers may help improve colorectal cancer diagnosis in the future.