Chemopreventive Effects of Frondanol A5, a Cucumaria frondosa Extract, against Rat Colon Carcinogenesis and Inhibition of Human Colon Cancer Cell Growth

Abstract

Sea cucumber extracts have been widely used to treat individuals with inflammatory conditions in East Asia. The present study has been designed to test potential colon cancer-preventive properties of Frondanol A5, a glycolipid extract from the sea cucumber, Cucumaria frondosa, using in vivo and in vitro models of colon cancer. Chemopreventive efficacy of Frondanol A5 was evaluated on azoxymethane-induced rat colon carcinogenesis using colonic aberrant crypt foci (ACF) as efficacy marker. At 7 weeks of age, groups of rats (12 per group) were fed the AIN-76A diet, and ACFs were induced by azoxymethane (15 mg/kg body weight). Three days after azoxymethane treatment, rats were fed with the diets containing 0, 150, and 450 ppm of Frondanol A5 and continued on the diets for 8 weeks, at which time ACFs were evaluated. Expression levels of proliferating cell nuclear antigen and p21(WAF1/CIP1) were determined in ACFs. Further, Frondanol A5 (10-120 microg/mL) was studied for its growth-inhibitory and apoptotic effects in the HCT-116 cell line. Dietary administration of 150 and 450 ppm of Frondanol A5 significantly suppressed azoxymethane-induced total colonic ACF formation, approximately 34% to 55% (P < 0.01 to P < 0.0001), and multicrypt aberrant foci (48-68.5%, P < 0.0001) in a dose-dependent manner. ACFs in rats treated with Frondanol A5 showed significant upregulation of p21(WAF1/CIP1) and downregulation of proliferating cell nuclear antigen compared with control group. Frondanol A5 showed growth inhibition at S and G(2)-M phase with a decrease in Cdc25c and an increase in p21(WAF1/CIP) with significant apoptosis associated with H2AX phosphorylation and caspase-2 cleavage in HCT116 cells. Overall, Frondanol A5 exhibits potential chemopreventive properties for colon carcinogenesis, which suggests further development of this sea cucumber extract.