Alterations in gut microbes contribute to metastatic niche formation, such as colonization of enterotoxic B. fragilis (ETBF) in the gut, which triggers systemic inflammation by enhancing the production of tumor-promoting and inflammatory cytokines (IL6, IL10, IL17A, IL17E, and IL27p28), establishing a pre-metastatic niche in other organs. The gene discussed is IL17A; the disease is neoplasm.