Nitric oxide and oral cancer: a review.

Nitric oxide (NO), a short-lived, endogenously produced gas, plays key role in various physiological as well as pathological processes. NO-inducing cell signaling events within the cell producing it and the diffusibility of it in other cells have led to the discovery of various physiological functions of NO including vasodilation, respiration, cell migration, immune response and apoptosis. On the other hand, excessive and unregulated NO synthesis has been implicated in many pathophysiological conditions including cancer. Research on NO, during the past few years is one of the growing areas in cancer biology. The high incidence of oral cancer and precancer has been linked with habits of tobacco chewing and smoking and NO has been said as the "messenger of death" in tobacco related diseases. NO seems to play a part in various stages of carcinogenesis from initiation to progression. However, there is considerable controversy and confusion in understanding its role in cancer biology. It is said to have both, tumoricidal as well as tumor promoting effects and these depend on its timing, location and concentration. Further, NO has also been shown to have antitumor, chemopreventive and therapeutic abilities. Here is an overview in which efforts are made to understand the role of this molecule in oral carcinogenesis.