Research on the relationship between gut microbiota and colorectal cancer has progressed since it was reported that Fusobacterium (F.) nucleatum may play an important role in carcinogenesis and cancer progression. The major mechanisms of carcinogenesis and cancer progression are that F. nucleatum evokes inflammation, evades the immune system, affects oncogenes and tumor suppressor genes, promotes cell proliferation, and easily adheres to cancer cells via Fap2 and Gal-GalNAc. As the stage of the cancer progresses, the abundance of F. nucleatum tends to increase. Some reports have concluded that the amount of F. nucleatum has a role in the progression of cancer, noting that the higher the abundance of F. nucleatum is, the worse the prognosis is. F. nucleatum is associated with the CIMP-high phenotype, microsatellite instability, and MLH1 hypermethylation, which may be involved in the serrated pathway. F. nucleatum is an indigenous bacterium in the oral cavity and is also known as a pathogen of periodontal disease. We previously reported that the strains in colorectal cancer and the oral cavity were identical. However, it is still unclear how F. nucleatum in the oral cavity reaches the large intestine. It is a future task to elucidate a prevention method for colorectal cancer by focusing on gut microbiota such as F. nucleatum.

Pancreatic diseases range from common diseases such as acute pancreatitis to autoimmune pancreatitis and cancer. Among them, pancreatic cancer is still a disease with a poor prognosis not only in Japan but also worldwide, and urgently is requires a remedy. In recent years, the involvement of intestinal bacteria in various gastrointestinal cancers has been reported, and the analysis of bacterial flora has also been undertaken in areas of pancreatic disease. It has been suggested that intestinal bacteria are involved in pancreatic disease regardless of whether it is benign or malignant. It is thought that studying the disease through the bacterial flora will lead to the elucidation of the canceration process.