[Intestinal microflora and cancer prevention].

Based on the results of ecological studies of intestinal microflora, we have been studying from various perspectives, the relationship between health and intestinal microflora. Concerning intestinal microflora and cancer, we reported in Cancer Research (61: 2395-2398, 2001) that spontaneous colon cancers that developed in Tcr beta/p53-double knockout mice did not develop in germfree conditions. This study, catching the attention of researchers, was reviewed in the 'News Feature' column of Nature (415: 8-9, 2002), which introduces recent studies attracting significant attention. Cancers are diseases of genes. However, in this study, which Nature found to be an as intriguing transformation (development of colon cancer in this case), did not occur only by genetic changes, unless accompanied by environmental factors (intestinal flora in this case). The fact that intestinal microflora are involved in the development of colon cancer suggests, on the other hand, that cancers can be prevented by controlling intestinal microflora. Here, data will be presented to show the relationship between intestinal microflora and colon cancers, mainly from our studies, and the mechanism involved will be further discussed.