Oral environment and cancer

Abstract

Cancer is now the leading cause of death in Japan. A rapid increase in cancer mortality is expected as Japan is facing a super-aged society. Many causes of cancer are known to be closely linked to life style factors, such as smoking, drinking, and diet. The oral environment is known to be involved in the pathogenesis and development of various diseases such as bronchitis, pneumonia, diabetes, heart disease, and dementia. Because the oral cavity acts as the bodily entrance for air and food, it is constantly exposed to foreign substances, including bacteria and viruses. A large number of bacteria are endemic to the oral cavity, and indigenous oral flora act to prevent the settlement of foreign bacteria. The oral environment is influenced by local factors, including dental plaque, tartar, teeth alignment, occlusion, an incompatible prosthesis, and bad lifestyle habits, and systemic factors, including smoking, consumption of alcohol, irregular lifestyle and eating habits, obesity, stress, hormones, and heredity. It has recently been revealed that the oral environment is associated with cancer. In particular, commensal bacteria in the oral cavity are involved in the development of cancer. Moreover, Candida, human papilloma virus and Epstein-Barr virus as well as commensal bacteria have been reported to be associated with the pathogenesis of cancer. In this review, we introduce recent findings of the correlation between the oral environment and cancer.

Keywords: Bacteria; Cancer; Candida; Epstein-Barr virus; Human papilloma virus; Oral environment.

Fig. 1

Influence of Oral Environment on Systemic Disease. The oral environment is influenced by local factors, including dental plaque, tartar, teeth alignment, occlusion, an incompatible prosthesis, and bad lifestyle habits, and systemic factors, including smoking, consumption of alcohol, an irregular lifestyle, eating habits, obesity, stress, hormones, and heredity factors. The oral environment is involved in systematic diseases, such as diabetes, preterm birth and low birth weight, cancer, respiratory disease, cardiovascular disease and cerebrovascular disease

Fig. 2

Involvement of F. nucleatum in colon cancer development. Figure shows the mechanisms of F. nucleatum in the involvement of colon cancer. F. nucleatum promotes E-cadherin/ß-catenin signaling via FadA adhesin and protects from immune attack by engaging its bacterial protein Fap2 with the inhibitory immunoreceptor TIGIT on NK and T cells. Moreover, F. nucleatum generate a proinflammatory microenvironment through the recruitment of tumor-infiltrating immune cells