Colorectal carcinoma is the most common gastrointestinal malignancy, affecting about 160,000 individuals/year in the U.S. Early diagnosis can result in significantly improved survival rates. Supplementation of diets with nutrients having a chemopreventive potential may be a useful strategy for cancer risk reduction in this project, we propose to use a recently developed technology that allows us to isolate viable colonic epithelial cells from human fecal samples that can be used for cellular and molecular characterization. Furthermore, rapid progress in molecular biology has led to identification of several biomarkers which are associated with neoplastic transformation in colonic mucosa. These biomarkers include: markers of cellular proliferation (Ki67), markers of neoplastic transformation such as CD44, tumor associated markers (CEA, C19-9), peanut agglutinin binding, and specific gene mutations (K-ras, p53, and DNA repair gene). The hypothesis is that the expression of tumor-associated cell surface markers and other macromolecules on colonic cells may have a predictive value as antecedents of malignancy and that certain nutrients may modulate these intermediate biomarkers. Study Design consists of three parts. l. A cross-sectional study of a cohort of patients (n=600) referred for diagnostic colonoscopy falling into the following 3 categories: (n=30 each) normal, polyps or colon cancer. 2. A prospective longitudinal study of a subset of patients from the cross-sectional study consisting of those diagnosed with sporadic adenomas (n=30), patients with familial polyposis (n=30) positive for APC gene and polyps. They will be followed for five years with stool colonocyte and biopsy sampling being carried out at intervals of 0, 2 and 4 yrs. 3. An interventional study, in which normal and colon cancer resected subjects (n=15) will receive supplements of dietary fiber at two levels (10 gm and 20 gm) or supplements of calcium at two levels (600 mg and 1200 mg) for a period of three months. Isolated colonocytes and colon tissue biopsies will be obtained at the beginning and at the end of the study to determine the effect of the nutritional factor on biomarkers of cellular proliferation and neoplastic transformation. Outcome variables are colonocyte cell-surface markers (CD44, CEA, CA 19-9, secretory component, and peanut agglutinin binding) as measured by flow cytometry, colonocyte mutations in K-ras and p53, mucosal biopsies for histology and Ki67 immunohistochemistry. Nonparametric statistical tests will be applied to determine the correlation between histological changes (degree of dysplasia, expansion of the cryptal proliferative zone as seen with Ki67) and changes in the expression of biomarkers of neoplastic transformation. These studies will help in the future development of i) new noninvasive methods of early detection of colonic neoplasia, and ii) an intermediate step to screen nutritional factors for their chemopreventive potential.
| Chung, D C; Rustgi, A K (1995) DNA mismatch repair and cancer. Gastroenterology 109:1685-99 |
