This study was designed with sixty 21-day old male Fisher 344 rats to investigate the preventive effect of the isoflavones on colon cancer. The colon cancer was induced by injections with colon carcinogen azoxymethane (15 mg AOM/kg body weight/time) at 4 and 5 weeks of age. All the rats were divided into control and experimental groups (n=15/group, isoflavones 30 ppm and 300 ppm). The rats were freely fed normal diets and isoflavones by oral feeding for 5 weeks. On 5 weeks later all the rats were sacrificed. Body weight, food consumption weight, cecum pH, aberrant crypt (AC), aberrant crypt foci (ACF) were detected. Inducible nitric oxide synthase (iNOS), matrix metalloproteinase (MMP)-2/9, nitric oxide (NO) were analyzed. Body weight, food consumption did not differ among control and experimental groups. The cecum pH and number of AC/ACF in experimental groups was significantly lower than that of in control group (p＜0.05). The expression of iNOS and MMP-2/9 in experimental groups was markedly lower than that of in control group. The concentration of NO in experimental groups was lower than that in control group. These results show that isoflavones may inhibit colon carcinogenesis through diverse mechanism. Therefore, further study should be needed to identify the mechanisms by which isoflavones may inhibit colon cancer.

Keywords: Isoflavones, Colon, Carcinogenesis, Azoxymethane