Protection of Dietary Polyphenols against Oral Cancer

Oral cancer represents a health burden worldwide with approximate 275,000 new cases diagnosed annually. Its poor prognosis is due to local tumor invasion and frequent lymph node metastasis. Better understanding and development of novel treatments and chemo-preventive approaches for the preventive and therapeutic intervention of this type of cancer are necessary. Recent development of dietary polyphenols as cancer preventives and therapeutic agents is of great interest due to their antioxidant and anti-carcinogenic activities. Polyphenols may inhibit carcinogenesis in the stage of initiation, promotion, or progression. In particular, dietary polyphenols decrease incidence of carcinomas and exert protection against oral cancer by induction of cell death and inhibition of tumor growth, invasion, and metastasis.

This review summarizes the preventive and possible therapeutic properties of dietary polyphenols against oral cancer in vitro, in vivo, and in clinical studies. Oral cancer is one of the most important medical problems. Chemopreventive strategies represent a promising approach to reduce the incidence and mortality of this disease. Most studies have demonstrated that dietary polyphenols could regulate numerous molecular pathways involved in cancer promotion and progression, suggesting chemopreventive and therapeutic capacity of dietary polyphenols against oral cancers. Among all polyphenols investigated, tea polyphenols have been shown to have obvious anti-carcinogenic effects. Limited investigations of other dietary polyphenols have been conducted in spite of their diversity and rich sources. Scientific evidences on other dietary polyphenols should be demonstrated to clarify the potentials of these molecules on prevention of oral cancer. Compared to a large amount of in vitro and animal studies, only a few clinical trials have been performed. Additional randomized clinical trials and cohort studies should be conducted to obtain direct evidence of dietary polyphenols against oral cancers.