Abstract B40: Chemoprevention potential of grape seed extract in azoxymethane-induced colon tumorigenesis in the A/J mouse model

Abstract

Abstract Colorectal cancer (CRC) is the second leading cause of cancer-related deaths. Overall, CRC is the third most diagnosed cancer in the United States with 150,000 new cases per year. Traditional CRC therapies are associated with severe toxicity, and therefore, natural products are appealing alternatives. Grape seed extract (GSE) is a natural supplement, rich in proanthocyanidins; which attributes to its cancer chemopreventive and anti-cancer efficacy in both in-vitro and in-vivo models. Chemoprevention utilizes an agent, natural or synthetic, to delay or stop cancer progression. Most (∼75%) of CRC develops sporadically, and diet, lifestyle, and/or environmental factors could further contribute to CRC progression. Taken together the above discussion, the present study was designed to assess GSE efficacy as a chemoprevention agent against chemical carcinogen (azoxymethane, AOM)-induced colon tumorigenesis in the A/J mouse model. As a carcinogen, AOM is utilized to mimic sporadic CRC development in humans. AOM is metabolized to its active form and results in the development of neoplastic aberrant crypt foci (ACF), which progress to adenoma, then to malignant adenocarcinoma. AOM-induced tumors form primarily in the colon, with greater tumor burden in the distal region. In our study, 6-week old A/J mice were divided into 5 groups: Group 1 received control diet (CD), Group 2 received 0.5% GSE in diet, and the other 3 groups received i.p. injections of AOM (5mg/kg) weekly, for six weeks. Two weeks post AOM injections, one group continued on CD and the other two groups were supplemented with 0.25% and 0.5% GSE (w/w) in diet. Animals were sacrificed at 32 and 42 weeks of age, or 20 and 30 weeks after AOM injections. GSE feeding did not exhibit toxic side effects with long-term treatment, as indicated by diet consumption and body weight-gain profile. GSE treatment resulted in a 48% decrease in colon tumor multiplicity at 32 weeks, and a 55% decrease at 42 weeks with 0.5% GSE. This effect was dose-dependent, with 0.5% GSE exhibiting maximum efficacy. Also, the efficacy was regionally specific, where tumor burden dramatically reduced in the distal region of the colon. Furthermore, GSE treatment reduced overall tumor size; tumor burden ranging from 2–3mm was decrease 85% in AOM-GSE-fed animals (only 5 tumors) compared to AOM-CD group (41 tumors) and no tumors over 3mm were observed with GSE-fed groups. GSE treatment also resulted in a 50% decrease in tumor burden in small intestine. Next we analyzed colon tissue from control and GSE groups to study the mechanism of GSE effects in vivo, towards apoptotic cell death, proliferation, and inflammation. Compared to controls, colon mucosal tissue from GSE-treated mice showed a 2-fold increase in TUNEL positive apoptotic cells, 30% decrease in PCNA positive proliferative cells, and ∼50% decrease in COX2 and iNOS levels in IHC analysis. In addition, cytokine array of colon mucosal tissue revealed that compared to controls, GSE treatment upregulates IFN-γ, IP-10, TNF-α, IL-17, IL-1α, IL-1β and TIMP-1, and down regulates M-CSF and MCP-1. These results are consistence with our IHC observations, specifically IFN-γ and TNF-α have been shown to induce apoptotic death, and MCP-1 expression is associated with colon cancer staging; the lower the levels of MCP-1, the better the prognosis. In conclusion, our results indicated that GSE, a non-toxic agent already consumed by humans, exerts strong chemopreventive effect against sporadic colorectal cancer development, through modulation of apoptosis, proliferation, and inflammation pathways. Citation Information: Cancer Prev Res 2011;4(10 Suppl):B40.