Sphingolipids are conserved membrane lipids that regulate cell proliferation, apoptosis and angiogenesis. As such, they have been implicated in various aspects of carcinogenesis, tumor progression and the acquisition of drug resistance. Genes of sphingolipid metabolism are aberrantly expressed in intestinal tumors compared to normal intestinal tissue, contributing to tumor progression. In addition, dietary sphingolipids such as those found in soy products reduce the risk of colon cancer in rodents by facilitating turnover of intestinal epithelial cells. Our laboratory recently identified a family of growth-regulating sphingolipids called sphingadienes that occur naturally in the fruitfly Drosophila and are structurally similar to sphingadienes found in soy. Our preliminary studies demonstrate that these medium-chain sphingadienes are cytotoxic to colon cancer cells by virtue of their ability to inhibit the phosphoinositide 3 kinase/AKT signaling pathway, a critical signaling hub in cancer. Our preliminary findings also indicate that sphingadienes inhibit the 2-catenin/Wnt signaling pathway implicated in colon carcinogenesis. Finally, sphingadienes have the potential to inhibit sphingosine kinase, an oncoprotein that is overexpressed in colon cancer and required for intestinal tumor progression. The overall goal of this application is to test the hypothesis that dietary sphingadienes and related sphingadiene compounds are safe and effective agents to prevent and/or treat colon cancer and to elucidate the mechanisms by which they exert their influence on colonic cells. Toward that end, we have devised three Specific Aims: 1) To characterize the effects of sphingadienes on colonic epithelial and colon cancer cells;2) To determine the metabolism and toxicity profile of sphingadienes in mice;3) To establish the efficacy of sphingadiene bases in preventing intestinal tumorigenesis and regulating cell signaling pathways in vivo. These preclinical studies should elucidate the molecular mechanisms by which sphingadienes exert their cytotoxic effects on colon cancer cells, the structural requirements for sphingadiene-mediated cytotoxicity and the ability to target key signaling pathways in cancer. They will be the first to address the specific potential of medium-chain sphingadienes and related compounds to prevent and/or treat colon cancer. They will also provide information regarding efficacy, metabolism and toxicity that should facilitate eventual translation into clinical trials.
Colon cancer is the second most common cancer of men and women and the third leading cause of cancer mortality. Because of the long latency of the disease, which develops from polyps that may take years to progress to frank carcinoma, colon cancer is an ideal disease for which to employ chemopreventive strategies. Identifying chemopreventive agents and dietary constituents that facilitate the turnover of intestinal epithelial cells and block the progression of preneoplastic lesions could have a significant impact on public health. This project explores the safety, efficacy and mechanism of action of a family of natural lipids found in soy and insects that exhibit cytotoxicity against colon cancer cells and prevent tumors in a preclinical model of colon cancer.
