New Horizon on Gut Microbiome and Cancers: Recent Information on Pathogenesis and Treatment

Abstract

An increasing number of studies have suggested that gut microbiota is closely related to tumor pathogenesis and their treatments. Among cancers, there have been many reports concerning gut microbiome and colon cancer (CRC), where microbial dysbiosis with depressing the population of “benign microbes” and increasing “harmful microbes” can lead to chronic enterocolitis and cancer development with progression. In addition, gut dysbiosis may change the metabolism of bile acids promoting CRC, which would offer a potential preventive therapeutic change in CRC by regulating gut microbiome and bile acid metabolism. Recently, SARS-CoV-2 impacts the gut microbiota, and the effects will have on CRC carcinogenesis. Obesity is estimated as an important factor that increases the risk of CRC. There has been accumulating evidence that the modulation of the gut microbiota composition by probiotics, prebiotics, and diets protects patients with CRC. Hepatocellular carcinoma (HCC) as the third leading cause of worldwide cancer mortality. Development of HCC in cirrhotic patients is related to changes in intestinal microbiome, including an escalation of dysbiosis and reduced bacterial richness. The species richness of fecal microbiota of hepatitis B-HCC patients was much high. The alterations of fecal microbiome may affect the process of <i>Helicobacter pylori (H. pylori)</i>-related progression of gastric lesion. Patients with gastric cancer have distinct microbiome in the stomach with lower biodiversity. Some bacteria from gastric microbiome are potentially carcinogenic as they are changed in gastric cancer. Patients with pancreas cancer and cholangiocarcinoma have also been related to gut dysbiosis. Other malignancies outside the gut like breast cancer (BC) might be related to gut microbiome as they might affect through metabolic, neural, and endocrine signal and immune function in the occurrence and progression of BC. Finally, cancer cachexia might be also associated with gut dysbiosis as it is closely related to bile acids (BA) metabolism regulation. The effects and side effects by variable cancer therapies such as chemotherapy, radiotherapy and also immunotherapy may be reconsidered from gut microbiome.