An Untested Approach: Biomarkers for Colon Cancer

癌症研究中要求最高的领域之一是寻找早期发现癌症的生物标志物

One of the most demanding areas of cancer research is finding biomarkers for the early detection of cancer. It is known that cancer is associated with alterations in the glycosylation patterns of glycoconjugates including glycolipids and glycoproteins. Based on this observation, the objective of this project is to identify novel mucinous biomarkers for the early detection and prognostic evaluation of colon cancer. Our approach differs from conventional methods of identifying cancer-associated glycans in that we examine the level of cellular glycosylation and use this information along with our knowledge of glyean biosynthetic pathways to predict likely candidate biomarkers. The overall hypothesis of the study is that "Changes in the structures of cancer-associated glycans are driven by fundamental changes in the cellular expression of the glycosyltransferases involved in their biosynthesis. Cancer cells express different glycosyltransferases leading to disticnt glyean signatures." In support of the above concept, we performed studies to assay the activity of fucosyl-,(3-N- acetylgalactosaminyl-, sialyl- and sulfotransferases in different colon cancer cell lines, and normal and cancerous colon tissue. These studies focused on those enzymes that generate the outer ends of the oligosaccharide chains in glycans. In these studies, we consistently observed elevated levels of two distinct Gal:3-O-sulfotransferases in cancerous tisue. One of these enzymes mediated formation of SE3- Gal|31¿>3GalNAca- type structure and the other mediated formation of SE3-Gal|31¿>4GlcNAc terminal units in the mucin core 2 tetrasaccharide Gal(31,4GlcNAc(31,6(Gal(31,3)GalNAca-. These tissues also exhibited appreciable levels of a(1,3)fucoyltranferase and a(2,3)sialyltranferase. Based on these studies from cancer cell lines and tissues, we have selected uniquely expressed novel sulfated carbohydrate epitopes that are likely present on colon cancer but not normal cells. We propose that these sulfated glycans provide novel targets for treatment and detection of colon cancer. In order to confirm this possibility, we propose to synthesize selected sulfated carbohydrate antigens and link them to KLH. Monoclonal antibodies will be developed against these target structures. Finally, these antibodies will be applied to colon cell lines and clinical specimens to assess their efficacy in identifying novel colon associated antigens. Our synthetic capability also provides a series of oligosaccharides to determine the specificity of the new antibody reagents, and thus these reagents are likely to be useful not only for studies of colon cancer.but also other problems in the fields of cancer and vascular biology. Generation of monoclonal antibodies unique to sulfated glycans of colon cancer cells can lead to new diagnosis strategies. There are currently no serum markers of colon cancer, and thus our project will also study if sulfated glycans in serum are elevated during colon cancer. The successful outcome of this program will lead us to a future program on colon cancer that includes the use of glycans expressed on cancer cells as targets for cancer therapy.