Intestinal Microflora and Carcinogenesis

The recognition that environmental and dietary factors play an important role in the etiology of several types of cancer, and that the role of microflora alterations during these conditions may be crucial, has given impetus to many nutritionists , toxicologists and oncologists to investigate the relationship among the gut microflora, nutritional factors and carcinogenesis in humans and in laboratory animals . The carcinogens responsible may be formed in the environment, or may be ingested in the form of a preformed carcinogen, cocarcinogen , promoter and/or procarcinogen, and metabolized to the ultimate carcinogen in the body. Furthermore, the external factors such as diet and bacterial supplements can affect the metabolic activity of gut microflora. In this context, the role of bacteria in the production , activation and/or deactivation of carcinogenes and tumor promoters has been investigated in several laboratories. This brief review evaluates the recognizable features on the relationship between the intestinal microflora and carcinogenesis and the mechanism whereby the intestinal microflora and their metabolites modulate the carcinogenesis in humans and in laboratory animal models.