Correlation between bromodeoxyuridine labelling and ornithine decarboxylase levels in normal rectal mucosa of patients with colorectal adenoma

Effect of dietary apigenin on colonic ornithine decarboxylase activity, aberrant crypt foci formation, and tumorigenesis in different experimental models

The efficacy of dietary apigenin, a dietary flavonoid, in colon cancer prevention was investigated by evaluating the inhibition of the ornithine decarboxylase (ODC) activity and the formation of aberrant crypt foci (ACF) and by studying the ability of apigenin to block colon carcinogenesis in two mouse models. First, the activity of ODC was measured in colon cancer cells (Caco-2) and in the colon epithelium of CF-1 mice. Apigenin at 10 and 30 muM significantly inhibited the ODC activity of Caco-2 cells by 26% and 57%, respectively. Colonic ODC activity in CF-1 mice was reduced with 0.1% dietary apigenin by 42% compared with the control, but this difference was not statistically significant. Second, ACF formation was evaluated in azoxymethane (AOM)-induced CF-1 mice. Female CF-1 mice at 6 wk of age were i.p. injected with 5 mg/kg body weight (BW) AOM once to induce ACF. ACF formation in CF-1 mice was reduced by 50% (P < 0.05) with 0.1% dietary apigenin fed for 6 wk when compared with the control. Dietary apigenin inhibited ACF only in the distal region of the CF-1 mouse colon. Finally, tumorigenesis studies were conducted using two different mouse models: AOM-induced CF-1 mice and Min mice with mutant adenomatous polyposis coli (APC) gene. Female CF-1 mice at 6 wk of age were i.p. injected with 10 mg/kg BW AOM weekly for 6 (AOM Study I) or 4 (AOM Study II) wk to induce tumors. CF-1 mice were fed diets containing 0.025% or 0.1% apigenin for 23-25 wk. Female Min mice were fed diets for 10 wk beginning at 5 wk of age. In two AOM-treated mouse colon tumor studies 0.025% and 0.1% dietary apigenin modestly reduced tumors in the group fed 0.025% apigenin (25% incidence in comparison with 65% in the controls) in a non-dose response manner. Apigenin failed to inhibit adenoma formation in the Min mouse study. These results suggest that dietary apigenin showed promise in cancer prevention by reducing the ODC activity and ACF formation, however, clear evidence of cancer prevention was not obtained in mouse tumor studies. Further investigation of the potential chemopreventive effect of apigenin in carcinogenesis is warranted.

Effects of a 3-mo consumption of short-chain fructo-oligosaccharides on parameters of colorectal carcinogenesis in patients with or without small or large colorectal adenomas

Intervention studies of colorectal adenoma recurrence have demonstrated the need for surrogate markers of the cancer risk. Short-chain fructo-oligosaccharides (sc-FOS) have protective actions on colon carcinogenesis in animal models. We investigated differences in biological markers between adenoma and adenoma-free subjects, before and after 3 mo of daily intake of 10 g sc-FOS, within a multicenter study. After a full colonoscopy, 3 groups were studied at baseline and after 3 mo: 26 subjects with small colorectal adenoma(s), 18 with large adenoma(s), and 30 with no adenoma. At baseline, the mean fecal butyrate concentration was significantly lower in the adenoma groups than in the adenoma-free group (12.01 +/- 5.08 vs. 17.28 +/- 7.34 mmol/g dry weight) but was significantly increased in that group after 3-mo ingestion of sc-FOS (15.7 +/- 8.0 mmol/g; P = 0.02). In subjects without adenoma, sc-FOS ingestion was associated with a decrease in fecal lithocholic acid (P = 0.02) and an increase in cholic acid (P = 0.02), chenodeoxycholic acid (P = 0.04), total primary bile acids (P = 0.03), and ursodeoxycholic acid (P = 0.05). Fecal pH, blood parameters, and crypt cell proliferation were not significantly modified by sc-FOS ingestion in either group. In subjects with and without adenoma, sc-FOS affects some aspects of the colonic environment, which may be involved in prevention of colorectal neoplasia.

Morphologic and cytoproliferative patterns of duodenal mucosa in two patients after long-term total parenteral nutrition: changes with oral refeeding and relation to intestinal resection

The morphologic and cytoproliferative patterns of the duodenal mucosa of two adult patients, one of whom had a short bowel, were evaluated after more than 2 months of postoperative total parenteral nutrition and 2 and 12 months after the resumption of oral alimentation. Morphometric analysis was performed on routinely processed duodenal biopsies. Cell proliferation was evaluated by means of in vitro bromodeoxyuridine uptake. The results were compared with those obtained in five healthy controls. After parenteral nutrition, patients showed significantly lower villus height and crypt depth than those of controls and a normal bromodeoxyuridine labeling index. After 2 months of refeeding, villus and crypt returned to normal, and the labeling index was increased. After 12 months of oral refeeding, labeling index, villus height, and crypt depth were similar to those of controls. The patient with the short bowel showed a number of cells per unit length of villus and crypt significantly greater than those of the controls and of the patient who underwent shorter intestinal resection. In human duodenal mucosa, (1) hypoplasia develops after long-term total parenteral nutrition; (2) mucosal recovery occurs through an increased cell proliferation after oral refeeding; and (3) extensive small bowel resection determines the development of relative hyperplasia.

Molecular genetics of colorectal carcinoma

The molecular genetics of colorectal carcinoma are among the best understood of any common human cancer. Reported molecular genetic abnormalities involve tumor-suppressor genes that undergo inactivation (e.g., apc, mcc, dcc, p53, and possibly genes on chromosomes 8p, 1p, and 22q) and dominant-acting oncogenes (e.g., ras, src, and myc). Multiple clonal genetic abnormalities accumulate during the development of colorectal carcinoma in adenomas. Altered DNA methylation is an early event, and the specific genetic alterations occur in a preferential order. However, the clinical application of molecular genetics in patients who are at risk for or have colorectal carcinoma is in its infancy. Patients with a predisposition to colorectal carcinoma caused by inheritance of familial adenomatous polyposis can be identified by genetic analysis of the apc gene on chromosome 5q21. In patients who undergo curative resection of colorectal cancer, deletion of the p53 gene on chromosome 17p, deletion of the dcc gene on 18q, and high fractional allelic loss (fraction of nonacrocentric autosomal arms with deletion) in the primary tumor appear to indicate an increased likelihood of occult disseminated disease and thus a poor prognosis. Additional studies are needed to establish the role of the molecular genetics of colorectal carcinoma in the management of patients who are at risk for or already have neoplasia of the large bowel.

Cell proliferation biomarkers in the gastrointestinal tract

Measurements of epithelial cell proliferation in the mucosa of the gastrointestinal tract pointed out the existence of cell kinetic abnormalities which can be involved in the first steps of carcinogenesis. In particular, an increase in the cell proliferation rate and an abnormal distribution of proliferating cells were found both in animals exposed to carcinogens and in human subjects at high risk of gastrointestinal cancer. In some diseases which predispose to cancer (i.e., chronic atropic gastritis, hereditary gastrointestinal cancer, sporadic colorectal neoplasia, chronic ulcerative colitis) we observed an expansion of the proliferative compartment even when the mucosa was not affected by morphological abnormalities. This proliferative feature seems to be associated with the presence of defects in cell differentiation. The abnormality is well detected by the histological examination of the proliferative pattern using microautoradiography after incorporation of tritiated thymidine, or using immunohistochemistry after bromodeoxyuridine uptake. The literature, and our own results, indicate that the search for abnormalities of epithelial cell proliferation can be useful in studying the earliest mechanisms leading to gastrointestinal cancer, in detecting subjects at high cancer risk, and for pilot chemoprevention studies using these abnormalities as intermediate biomarkers of gastrointestinal cancer risk.

Intermediate biomarkers of increased risk for colorectal cancer: comparison of different methods of analysis and modifications by chemopreventive interventions

Intermediate biomarkers of abnormal cell growth and development have recently been used in chemoprevention trials in attempts to identify the efficacy of chemopreventive agents in human subjects. Measurements carried out include those related to cell proliferation, differentiation, and gene structure and expression in the colon. Among modified patterns of cell proliferation identified by microautoradiographic or immunoperoxidase assays, a characteristic expansion in the size of the proliferative compartment has been observed in normal-appearing colorectal mucosa of human subjects with disease increasing cancer risk; the same patterns have been induced by chemical carcinogens in rodents. Moreover, this intermediate biomarker has been modulated by chemopreventive agents in both rodents and humans. Newer intermediate biomarkers being studied for application to human chemopreventive programs include normal and abnormal patterns of expression of mucins, intermediate filaments and cytoskeletal proteins, and the structure and expression of a variety of genes associated with normal and abnormal cell development. The application of these various intermediate biomarkers to chemoprevention studies is increasing the ability of investigators to analyze the effects of novel chemopreventive agents in the colon and in other organs.