When human cells meet bacteria: precision medicine for cancers using the microbiota

Abstract

The human microbiota interacts with the host immune system in multiple ways to influence the development of diseases, including cancers; however, a detailed understanding of their relationship is unavailable. Accumulating evidence has only revealed an association rather than a causal link between microbial alterations and carcinogenesis. The regulatory loops among the microbiome, human cells and the immune system are far more complicated and require further studies to be revealed. In this review, we discuss the impact of the microbiota on cancer initiation, development and progression in different types of human cells, mainly focusing on the clinical translation from microbiome research to an accurate diagnosis, subtype classification and precision medicine.

Keywords: Microbiota; cancer; gut; microbiome; precision medicine.

Figure 1

Microbiome-mediated tumorigenesis in different types of human cells. Microbiome alterations in gut and extra-gut systems are associated with cancer initiation and progression. The remote regulation of many axes, including oral-lung/pancreas (green dashed lines), bile acid-esophagus (purple dashed line) and gut-liver axes (black dashed line) as well as dual-directional regulation of the gut-lung (blue dashed lines) and liver-bile acid (purple dashed lines) axes are illustrated.

Figure 2

Translational use of the microbiota in human cancer. Global alterations in bacterial communities have the potential to serve as a biomarker in human cancer for an accurate diagnosis, molecular subtype classification and risk stratification. Microbiota-mediated cancer initiation and development are targeted by different mechanisms, including the amelioration of chronic inflammation by antibiotics, the administration of probiotics and fecal microbiota transplantation to rebalance dysbiosis, and the administration of anti-toxin drugs to alleviate defective barrier-induced toxicity. Additional “good” bacteria should be identified and used to prevent chemotherapy resistance.