Cancer-promoting effects of microbial dysbiosis

Abstract

Humans depend on our commensal bacteria for nutritive, immune-modulating, and metabolic contributions to maintenance of health. However, this commensal community exists in careful balance that, if disrupted, enters dysbiosis; this has been shown to contribute to the pathogenesis of colon, gastric, esophageal, pancreatic, laryngeal, breast, and gallbladder carcinomas. This development is closely tied to host inflammation, which causes and is aggravated by microbial dysbiosis and increases vulnerability to pathogens. Advances in sequencing technology have increased our ability to catalog microbial species associated with various cancer types across the body. However, defining microbial biomarkers as cancer predictors presents multiple challenges, and existing studies identifying cancer-associated bacteria have reported inconsistent outcomes. Combining metabolites and microbiome analyses can help elucidate interactions between gut microbiota, metabolism, and the host. Ultimately, understanding how gut dysbiosis impacts host response and inflammation will be critical to creating an accurate picture of the role of the microbiome in cancer.

Figure 1

The progression of the gut microbial community from a state of balance (eubiosis) to imbalance (dysbiosis) is associated with physiologic, metabolic and cellular responses in the host that modulate cancer risk.