Seventh-Day Adventist vegetarians have a quiescent proliferative activity in colonic mucosa

Secondary Bile Acids and Short Chain Fatty Acids in the Colon: A Focus on Colonic Microbiome, Cell Proliferation, Inflammation, and Cancer

Secondary bile acids (BAs) and short chain fatty acids (SCFAs), two major types of bacterial metabolites in the colon, cause opposing effects on colonic inflammation at chronically high physiological levels. Primary BAs play critical roles in cholesterol metabolism, lipid digestion, and host–microbe interaction. Although BAs are reabsorbed via enterohepatic circulation, primary BAs serve as substrates for bacterial biotransformation to secondary BAs in the colon. High-fat diets increase secondary BAs, such as deoxycholic acid (DCA) and lithocholic acid (LCA), which are risk factors for colonic inflammation and cancer. In contrast, increased dietary fiber intake is associated with anti-inflammatory and anticancer effects. These effects may be due to the increased production of the SCFAs acetate, propionate, and butyrate during dietary fiber fermentation in the colon. Elucidation of the molecular events by which secondary BAs and SCFAs regulate colonic cell proliferation and inflammation will lead to a better understanding of the anticancer potential of dietary fiber in the context of high-fat diet-related colon cancer. This article reviews the current knowledge concerning the effects of secondary BAs and SCFAs on the proliferation of colon epithelial cells, inflammation, cancer, and the associated microbiome.

Effects of ginger supplementation on cell-cycle biomarkers in the normal-appearing colonic mucosa of patients at increased risk for colorectal cancer: results from a pilot, randomized, and controlled trial

To estimate the effects of ginger on apoptosis, proliferation, and differentiation in the normal-appearing colonic mucosa, we randomized 20 people at increased risk for colorectal cancer to 2.0 g of ginger or placebo daily for 28 days in a pilot trial. Overall expression and distributions of Bax, Bcl-2, p21, hTERT, and MIB-1 (Ki-67) in colorectal crypts in rectal mucosa biopsies were measured using automated immunohistochemistry and quantitative image analysis. Relative to placebo, Bax expression in the ginger group decreased 15.6% (P = 0.78) in the whole crypts, 6.6% (P = 0.95) in the upper 40% (differentiation zone) of crypts, and 21.7% (P = 0.67) in the lower 60% (proliferative zone) of crypts; however, there was a 19% increase (P = 0.14) in Bax expression in the upper 40% relative to the whole crypt. While p21 and Bcl-2 expression remained relatively unchanged, hTERT expression in the whole crypts decreased by 41.2% (P = 0.05); the estimated treatment effect on hTERT expression was larger in the upper 40% of crypts (-47.9%; P = 0.04). In the ginger group, MIB-1 expression decreased in the whole crypts, upper 40% of crypts, and lower 60% of crypts by 16.9% (P = 0.39), 46.8% (P = 0.39), and 15.3% (P = 0.41), respectively. These pilot study results suggest that ginger may reduce proliferation in the normal-appearing colorectal epithelium and increase apoptosis and differentiation relative to proliferation--especially in the differentiation zone of the crypts and support a larger study to further investigate these results.

Health Implications of a Vegetarian Diet

There is now a significant amount of research that demonstrates the health benefits of vegetarian and plant-based diets, which have been associated with a reduced risk of obesity, diabetes, heart disease, and some types of cancer as well as increased longevity. Vegetarian diets are typically lower in fat, particularly saturated fat, and higher in dietary fiber. They are also likely to include more whole grains, legumes, nuts, and soy protein, and together with the absence of red meat, this type of eating plan may provide many benefits for the prevention and treatment of obesity and chronic health problems, including diabetes and cardiovascular disease. Although a well-planned vegetarian or vegan diet can meet all the nutritional needs of an individual, it may be necessary to pay particular attention to some nutrients to ensure an adequate intake, particularly if the person is on a vegan diet. This article will review the evidence for the health benefits of a vegetarian diet and also discuss strategies for meeting the nutritional needs of those following a vegetarian or plant-based eating pattern.

Effect of cyclooxygenase genotype and dietary fish oil on colonic eicosanoids in mice

Dietary ω3 fatty acids can modulate substrate availability for cyclooxygenases (COXs) and lipoxygenases, thus modulating downstream eicosanoid formation. This could be an alternative approach to using nonsteroidal anti-inflammatory drugs and other COX inhibitors for limiting Prostaglandin E(2) (PGE(2)) synthesis in colon cancer prevention. The aims of this study were to evaluate to what extent COX- and lipoxygenase-derived products could be modulated by dietary fish oil in normal colonic mucosa and to evaluate the role of COX-1 and COX-2 in the formation of these products. Mice (wild-type, COX-1 null or COX-2 null) were fed a diet supplying a broad mixture of fatty acids present in European/American diets, supplemented with either olive oil (oleate control diet) or menhaden (fish) oil ad libitum for 9-11 weeks. Colonic eicosanoid levels were measured by liquid chromatography tandem mass spectroscopy (LC-MS/MS), and proliferation was assessed by Ki67 immunohistochemistry. For the dietary alteration of colonic arachidonic acid: eicosapentaenoic ratios resulted in large shifts in formation of COX and lipoxygenase metabolites. COX-1 knockout virtually abolished PGE(2) formation, but interestingly, 12-hydroxyeicosatetraenoic (12-HETE) acid and 15-HETE formation was increased. The large changes in eicosanoid profiles were accompanied by relatively small changes in colonic crypt proliferation, but such changes in eicosanoid formation might have greater biological impact upon carcinogen challenge. These results indicate that in normal colon, inhibition of COX-2 would have little effect on reducing PGE(2) levels.

Clinical trials of antioxidants as cancer prevention agents: past, present, and future

The purpose of this review is to summarize the most important human clinical trials of antioxidants as cancer prevention agents conducted to date, provide an overview of currently ongoing studies, and discuss future steps needed to advance research in this field. To date there have been several large (at least 7000 participants) trials testing the efficacy of antioxidant supplements in preventing cancer. The specific agents (diet-derived direct antioxidants and essential components of antioxidant enzymes) tested in those trials included β-carotene, vitamin E, vitamin C, selenium, retinol, zinc, riboflavin, and molybdenum. None of the completed trials produced convincing evidence to justify the use of traditional antioxidant-related vitamins or minerals for cancer prevention. Our search of ongoing trials identified six projects at various stages of completion. Five of those six trials use selenium as the intervention of interest delivered either alone or in combination with other agents. The lack of success to date can be explained by a variety of factors that need to be considered in the next generation research. These factors include lack of good biological rationale for selecting specific agents of interest; limited number of agents tested to date; use of pharmacological, rather than dietary, doses; and insufficient duration of intervention and follow-up. The latter consideration underscores the need for alternative endpoints that are associated with increased risk of neoplasia (i.e., biomarkers of risk), but are detectable prior to tumor occurrence. Although dietary antioxidants are a large and diverse group of compounds, only a small proportion of candidate agents have been tested. In summary, the strategy of focusing on large high-budget studies using cancer incidence as the endpoint and testing a relatively limited number of antioxidant agents has been largely unsuccessful. This lack of success in previous trials should not preclude us from seeking novel ways of preventing cancer by modulating oxidative balance. On the contrary, the well demonstrated mechanistic link between excessive oxidative stress and carcinogenesis underscores the need for new studies. It appears that future large-scale projects should be preceded by smaller, shorter, less expensive biomarker-based studies that can serve as a link from mechanistic and observational research to human cancer prevention trials. These relatively inexpensive studies would provide human experimental evidence for the likely efficacy, optimum dose, and long-term safety of the intervention of interest that would then guide the design of safe, more definitive large-scale trials.

Kenaf seed supercritical fluid extract reduces aberrant crypt foci formation in azoxymethane-induced rats

Kenaf (Hibiscus cannabinus) a plant of the family Malvaceae, is a valuable fiber plant native to India and Africa. Kenaf seeds contain alpha-linolenic acid, phytosterol such as β-sitosterol, vitamin E and other antioxidants with chemopreventive properties. In the present study we examined the hypothesis that kenaf seed 'supercritical fluid extract' (SFE) extract could suppress the early colon carcinogenesis in vivo by virtue of its bioactive compounds. To accomplish this goal, 60 male rats were randomly assigned to 5 groups which were (1) negative control group [not induced with azoxymethane (AOM)]; (2) positive control group (induced with AOM but received no treatment); (3) group treated with 500 mg/kg kenaf seed SFE extract; (4) group treated with 1000 mg/kg kenaf seed SFE extract; (5) group treated with 1500 mg/kg kenaf seed SFE extract. At 7 weeks of age, all rats except the negative control group received 15 mg/kg of AOM injection subcutaneously once a week for 2 weeks. Rats were euthanized at 13 weeks of the experiment. Number of ACF (mean±SD) ranged from 84.4±4.43 to 179.5±12.78 in group 2, 3, 4, 5. ACF reductions compared with the untreated group were 45.3, 51.4 and 53.1% in rats fed with 500, 1000 and 1500 mg/kg body weight, respectively. There were no significant differences in weight gain among groups. Our finding indicates that kenaf seed SFE extract reduced AOM-induced ACF in Sprague-Dawley male rats.

Hypothesis: oxidative stress score as a combined measure of pro-oxidant and antioxidant exposures

PURPOSE

To explore the hypothesis that a combination of several risk factors acting through the same pathway may produce an overall large increase in risk even in the presence of weak associations with each individual factor.

METHODS

Using oxidative stress pathway as an example, we propose an oxidative stress score (OSS), where high and low pro-oxidant exposures expressed as continuous variables are assigned values of 0 and 1, while high and low antioxidant exposures are assigned values of 1 and 0, respectively. Dichotomous variables for pro-oxidant and antioxidant exposures are scored in a similar fashion. All individual scores are then summed to calculate the overall OSS, where higher and lower values indicate a shift toward antioxidant and pro-oxidant exposures, respectively.

RESULTS

We illustrate this approach by using data from two previously-conducted case-control studies: a colonoscopy-based colorectal adenoma study, and a population-based prostate cancer study. In this pilot illustration we found a substantial decrease in risk associated with a high OSS for both prostate cancer and colorectal adenoma. By contrast, analyses for individual OSS components demonstrated no discernible pattern.

CONCLUSIONS

Our exploratory analyses serve as a demonstration of a method and warrant further confirmation on a larger scale.

Effect of a 12-month exercise intervention on patterns of cellular proliferation in colonic crypts: a randomized controlled trial

BACKGROUND

Colon crypt architecture and proliferation may be appropriate biomarkers for testing prevention interventions. A hypothesized mechanism for exercise-induced colon cancer risk reduction might be through alterations in colon crypt cell architecture and proliferation.

METHODS

Healthy, sedentary participants with a colonoscopy within the previous 3 years were recruited through gastroenterology practices and media. We randomly assigned 100 women and 102 men, ages 40 to 75 years, to a control group or a 12-month exercise intervention of moderate-to-vigorous aerobic exercise, 60 minutes per day, 6 days per week, and assessed change in number and relative position of Ki67-stained cells in colon mucosal crypts.

RESULTS

Exercisers did a mean 370 min/wk (men) and 295 min/wk (women) of exercise (seven dropped the intervention). In men, the mean height of Ki67-positive nuclei relative to total crypt height was related to amount of exercise, with changes from baseline of 0.0% (controls), +0.3% (exercisers <250 min/wk), -1.7% (exercisers 250-300 min/wk), and -2.4% (exercisers >300 min/wk; P(trend) = 0.03). In male exercisers whose cardiopulmonary fitness (V(O(2))max) increased >5%, the mean height of Ki67-positive nuclei decreased by 2% versus 0.9% in other exercisers, and versus no change in controls (P(trend) = 0.05). Similar trends were observed in other proliferation markers. In women, increased amount of exercise or V(O(2))max did not result in notable changes in proliferation markers.

CONCLUSIONS

A 12-month moderate-to-vigorous intensity aerobic exercise intervention resulted in significant decreases in colon crypt cell proliferation indices in men who exercised a mean of >/=250 min/wk or whose V(O(2))max increased by >/=5%.

Effects of different phytosterol analogs on colonic mucosal cell proliferation in hamsters

OBJECTIVE

The aim of this study was to investigate the effects of different phytosterols and their analogs on colonic mucosal cell proliferation in hamsters.

METHOD

Hamsters (n=70) were randomly assigned to seven groups after a 2-week acclimation and fed the experimental diet for 5 weeks. Diets included (i) the semipurified diet with no cholesterol (Con), (ii) the Con diet plus 0.25% cholesterol (Ch-con), or the Ch-con diet with (iii) 1% phytosterols (Ste), (iv) 1% phytostanols (Sta), (v) 1.76% sterol esters (esterified to fish oil, SteF), (vi) 0.71% stanol esters (esterified to ascorbic acid [disodium ascorbyl phytostanol phosphate, FM-VP4], 0.7% StaA) and (vii) 1.43% stanol esters (1.4% StaA), respectively. After 5 weeks on experimental diet, hamsters were sacrificed, and colons were collected. Colonic mucosal cell proliferation was measured by immunohistochemistry using monoclonal antibodies against antigen Ki-67.

RESULTS

Colonic mucosal cell proliferation was 21.4% (P<.01) lower in the 0.7%, but not 1.4%, StaA relative to the Ch-con group. In addition, a lower (-13.9%) cell proliferation was observed in the SteF group in comparison to the Ch-con group; however, this difference achieved only a borderline level of statistical significance (P=.069). No differences were observed between Con and Ch-con, as well as among Ste, Sta, 1.4% StaA and Ch-con treatments.

CONCLUSION

Plant stanols esterified to ascorbic acid may possess anticarcinogenic properties in the colon by suppressing colonic mucosa cell proliferation; however, this effect was not observed with free plant sterols or stanols.

Position of the American Dietetic Association and Dietitians of Canada: vegetarian diets

It is the position of the American Dietetic Association and Dietitians of Canada that appropriately planned vegetarian diets are healthful, nutritionally adequate, and provide health benefits in the prevention and treatment of certain diseases. Approximately 2.5% of adults in the United States and 4% of adults in Canada follow vegetarian diets. A vegetarian diet is defined as one that does not include meat, fish, or fowl. Interest in vegetarianism appears to be increasing, with many restaurants and college foodservices offering vegetarian meals routinely. Substantial growth in sales of foods attractive to vegetarians has occurred and these foods appear in many supermarkets. This position paper reviews the current scientific data related to key nutrients for vegetarians including protein, iron, zinc, calcium, vitamin D, riboflavin, vitamin B-12, vitamin A, n-3 fatty acids, and iodine. A vegetarian, including vegan, diet can meet current recommendations for all of these nutrients. In some cases, use of fortified foods or supplements can be helpful in meeting recommendations for individual nutrients. Well-planned vegan and other types of vegetarian diets are appropriate for all stages of the life-cycle including during pregnancy, lactation, infancy, childhood, and adolescence. Vegetarian diets offer a number of nutritional benefits including lower levels of saturated fat, cholesterol, and animal protein as well as higher levels of carbohydrates, fibre, magnesium, potassium, folate, antioxidants such as vitamins C and E, and phytochemicals. Vegetarians have been reported to have lower body mass indices than non-vegetarians, as well as lower rates of death from ischemic heart disease, lower blood cholesterol levels, lower blood pressure, and lower rates of hypertension, type 2 diabetes, and prostate and colon cancer. While a number of federally funded and institutional feeding programs can accommodate vegetarians, few have foods suitable for vegans at this time. Because of the variability of dietary practices among vegetarians, individual assessment of dietary intakes of vegetarians is required. Dietetics professionals have a responsibility to support and encourage those who express an interest in consuming a vegetarian diet. They can play key roles in educating vegetarian clients about food sources of specific nutrients, food purchase and preparation, and any dietary modifications that may be necessary to meet individual needs. Menu planning for vegetarians can be simplified by use of a food guide that specifies food groups and serving sizes.

Position of the American Dietetic Association and Dietitians of Canada: Vegetarian diets

It is the position of the American Dietetic Association and Dietitians of Canada that appropriately planned vegetarian diets are healthful, nutritionally adequate, and provide health benefits in the prevention and treatment of certain diseases. Approximately 2.5% of adults in the United States and 4% of adults in Canada follow vegetarian diets. A vegetarian diet is defined as one that does not include meat, fish, or fowl. Interest in vegetarianism appears to be increasing, with many restaurants and college foodservices offering vegetarian meals routinely. Substantial growth in sales of foods attractive to vegetarians has occurred, and these foods appear in many supermarkets. This position paper reviews the current scientific data related to key nutrients for vegetarians, including protein, iron, zinc, calcium, vitamin D, riboflavin, vitamin B-12, vitamin A, n-3 fatty acids, and iodine. A vegetarian, including vegan, diet can meet current recommendations for all of these nutrients. In some cases, use of fortified foods or supplements can be helpful in meeting recommendations for individual nutrients. Well-planned vegan and other types of vegetarian diets are appropriate for all stages of the life cycle, including during pregnancy, lactation, infancy, childhood, and adolescence. Vegetarian diets offer a number of nutritional benefits, including lower levels of saturated fat, cholesterol, and animal protein as well as higher levels of carbohydrates, fiber, magnesium, potassium, folate, and antioxidants such as vitamins C and E and phytochemicals. Vegetarians have been reported to have lower body mass indices than nonvegetarians, as well as lower rates of death from ischemic heart disease; vegetarians also show lower blood cholesterol levels; lower blood pressure; and lower rates of hypertension, type 2 diabetes, and prostate and colon cancer. Although a number of federally funded and institutional feeding programs can accommodate vegetarians, few have foods suitable for vegans at this time. Because of the variability of dietary practices among vegetarians, individual assessment of dietary intakes of vegetarians is required. Dietetics professionals have a responsibility to support and encourage those who express an interest in consuming a vegetarian diet. They can play key roles in educating vegetarian clients about food sources of specific nutrients, food purchase and preparation, and any dietary modifications that may be necessary to meet individual needs. Menu planning for vegetarians can be simplified by use of a food guide that specifies food groups and serving sizes.

Peanuts as a source of beta-sitosterol, a sterol with anticancer properties

Work from our laboratory, as well as others, suggests a protective role of phytosterols (PS), especially beta-sitosterol, from colon, prostate, and breast cancer. Asians and vegetarians consume higher amounts of PS than Western societies. The latter societies have a higher incidence of these cancers than Asians and vegetarians. The aim of this study was to evaluate peanuts and its products as sources of PS in the American diet. Roasted peanuts contain 61-114 mg PS/100 g depending on the peanut variety, 78-83% of which is in the form of beta-sitosterol. Unrefined peanut oil contains 207 mg PS/100 g, which is similar to that of the US Department of Agriculture Nutrient Database. This value is higher than that of unrefined olive oil. Refining these oils results in reduction in PS concentration in the oil. This loss is greater in the case of olive oil than peanut oil. Further refining, such as deodorization, results in significant loss in PS, but hydrogenation after refining has a minimal effect on PS loss. Peanut butter, which represents 50% of the peanuts consumed in the United States, contains 144-157 mg PS/100 g. Peanut flour, which results from partial removal of oil from peanuts, contains 55-60 mg PS/100 g. The data suggest that peanuts and its products, such as peanut oil, peanut butter, and peanut flour, are good sources of PS.

Phytosterols as anticancer dietary components: evidence and mechanism of action

Phytosterols (PS) or plant sterols are structurally similar to cholesterol. The most common PS are beta-sitosterol, campesterol and stigmasterol. Epidemiologic and experimental studies suggest that dietary PS may offer protection from the most common cancers in Western societies, such as colon, breast and prostate cancer. This review summarizes the findings of these studies and the possible mechanisms by which PS offer this protection. These include the effect of PS on membrane structure and function of tumor and host tissue, signal transduction pathways that regulate tumor growth and apoptosis, immune function of the host and cholesterol metabolism by the host. In addition, suggestions for future studies to fill the gaps in our knowledge have been given.

K-ras mutations, rectal crypt cells proliferation, and meat consumption in patients with left-sided colorectal carcinoma

It has been suggested that N-nitroso compounds derived from meat may increase the risk of K-ras mutations in the human colon. We sought evidence of associations between red meat consumption, frequency and type of K-ras mutations in resected tumours, and the rate of crypt cell proliferation (CCP) in the normal mucosa of patients with left-sided colorectal carcinoma. Meat consumption was assessed by food frequency questionnaire, and CCP was determined in rectal biopsies obtained prior to surgery. K-ras mutations in the resected tumours were determined using a PCR-based oligonucleotide hybridization assay. Fifteen K-ras mutations were detected in tumours from 43 patients; 13/15 in codon 12, 3/15 in codon 13, and 1/15 in both codons 12 and 13. All mutations were G-->A or G-->T transitions. There was no statistically significant difference between intakes of red meat in patients with a K-ras mutation (92.4 +/- 9.7 g/day) and those without (82.3 +/- 7.7 g/day). Rectal CCP was significantly higher in patients than in healthy controls, but there was no correlation with meat consumption or K-ras mutation. These data do not support the hypothesis that meat consumption is a risk factor for acquisition of K-ras mutations during colorectal carcinogenesis.

Effect of eicosapentaenoic acid on the proliferation and incidence of apoptosis in the colorectal cell line HT29

Fish oil has been shown to reduce the induction of colorectal cancer in animal models by a mechanism which may involve suppression of mitosis, increased apoptosis, or both. We used the human colonic adenocarcinoma cell line HT29 to explore the effects of the long-chain n-3 polyunsaturated fatty acid eicosapentaenoic acid (EPA) on cell proliferation and death in vitro. Cells were cultured in media containing EPA at 5, 10, and 15 microg/mL. Cell number and thymidine incorporation were used to quantify proliferation, and cell cycle effects were studied using flow cytometry. Gel electrophoresis, annexin-V binding, and morphological criteria were used to characterize apoptosis. Adherent cells and freely floating detached cells were treated as two distinct populations. In the presence of EPA at 10 and 15 microg/mL there was a marked reduction in the growth rate of adherent HT29 colonies, owing to an increased detachment of adherent cells. After treatment with 10 or 15 microg/mL EPA the proportion of adherent cells in S-phase increased, indicating either a block in late S-phase or early G2. Floating cells showed evidence of extensive DNA cleavage, but the proportion of floating cells with sub GO DNA content declined on treatment with 10 or 15 microg/mL EPA even though the number of floating cells increased. We conclude that EPA does not inhibit mitosis of adherent cells, but increases the rate at which they become detached from the substrate, probably at an early stage in the initiation of apoptosis. This mechanism may be analogous to "anoikis," or induction of apoptosis in response to loss of cell contact, and may contribute to the anticarcinogenic effects of fish oil in vivo.

Antimitotic peptide characterized from soybean: role in protection from cancer?

Cell proliferation, or mitosis, is believed to play a central role in the multistep process of carcinogenesis. The recent identification, cloning, and characterization of a potent antimitotic peptide from soybeans is, therefore, of interest in view of epidemiologic associations between intake of soy products and reduced cancer risk. Several questions must be resolved, however, before the biochemistry and epidemiology can be linked.

Dairy foods and prevention of colon cancer: human studies

Colon cancer is the commonest gastrointestinal cancer and the second leading cause of cancer deaths in the United States. Recent approaches to lowering the incidence of colon cancer have included attempts at dietary prevention and chemoprevention. International and national incidence rates for colon cancer suggest an inverse relationship with dietary calcium and/or vitamin D intake (or sun exposure). Several human intervention studies have suggested that supplemental calcium administration will change proliferative indices of risk for colon cancer from high to lower risk patterns. The principal current hypothesis for the action of calcium implies that calcium may precipitate or bring out of solution fatty acids and bile acids that are potentially toxic to the colorectal epithelium. Both calcium administration and dairy food administration are associated with lowering aqueous fecal concentrations of bile acids and fatty acids accompanied by a highly significant lowering of cytotoxicity in studies in vitro. There is biochemical and biological evidence in cell culture systems that exposure to calcium and/or vitamin D reduces the oncogenic properties of colon cancer cells. A recent blinded study of the administration of low-fat dairy foods demonstrated a significant improvement in several parameters of proliferation as well as in two differentiation markers from a high to a lower risk pattern. Furthermore, administration of calcium also has been shown to reduce the incidence of recurrent adenomatous polyps in individuals at increased risk for colon polyp formation because of the presence of prior colon adenomata. These combined data suggest that administration of supplemental calcium or low-fat dairy foods may have a significant effect upon colonic polyp and perhaps colon cancer incidence.

A dietary trial with a short-term low-sucrose diet in an Italian population: effects on colorectal mucosal proliferation

Colorectal mucosal proliferation is supposed to predict colon cancer risk. We investigated whether a low-sucrose diet might reduce colorectal mucosal proliferation in a group of patients at higher risk of colorectal cancer after at least two colon adenoma resections. In a pilot phase, 14 patients [12 men and 2 women, 60.3 +/- 5 (SD) yr] were instructed to adopt a low-sucrose diet for one month. Colorectal biopsies were taken twice in the same patients, at the start and the end of the intervention period, and mucosal proliferation was measured by [3H]thymidine uptake in vitro and autoradiography. Although compliance of study participants to dietary modification was high, only a few agreed to two consecutive endoscopies; thus we carried out a randomized study, and 107 patients were assigned to a low-sucrose diet (50 treated patients: 31 men and 19 women, 59.7 +/- 7.5 yr) or instructed to continue their usual diet for one month (55 control patients: 32 men and 23 women, 59.6 +/- 7.7 yr). At the end of this period, colorectal biopsies were obtained. The results of the pilot phase and the randomized study showed that a low-sucrose diet for one-month did not affect proliferation or the distribution of proliferation activity along the crypt. The food-frequency questionnaires indicated that treated patients consumed significantly less sucrose (and fewer total calories) during the dietary modification. Urinary fructose, a measure of dietary sucrose intake, was also reduced at the end of the intervention period. In conclusion, we found no evidence that a low-sucrose diet for one month influences colorectal mucosal proliferation.

Rectal epithelial proliferation in persons with or without a history of adenoma and its association with diet and lifestyle habits

BACKGROUND

Rectal epithelial proliferation (REP) measurements are used as a biomarker of risk for colorectal neoplasia and response to chemoprevention. The authors evaluated REP in screenees with and without a history of adenoma and its association with demographic and adenoma characteristics, diet, and other lifestyle habits.

METHODS

Long term lifestyle habits were evaluated and proliferation assessed by in vitro bromodeoxyuridine labeling of rectal biopsies in 223 screenees, 132 of whom had adenomas removed > 3 years previously. Analyses included the total population, screenees with a previous history of adenomas and adenoma free screenees separately, and a subgroup of 55 matched adenoma cases and controls.

RESULTS

Crypt proliferation measurements were not elevated in screenees with a history of adenomas compared with adenoma free screenees (mean total labeling index [LI] of 4.8% and 4.9%, respectively). This was confirmed by the case-control analysis, in which the LI of the most superficial crypt compartment was lower in the adenoma cases (P=0.05). Moreover, their total LI correlated negatively with the number of adenomas removed previously (P < 0.01). Proliferation was more frequent in the most superficial crypt compartments of female adenoma free screenees than in female screenees with a history of adenomas (P=0.02), and in men age > 65 years compared with younger men (P=0.06). In the total population, negative Spearman rank correlations were found between total LI and long term dietary intake of calcium (correlation coefficient [r]=-0.15; P=0.02), LI of the two most superficial crypt compartments and intake of fiber (r=-0.18; P=0.01), water (r=-0.12; P=0.08), and carbohydrates (not significant). A positive correlation was found between LI of the most superficial crypt compartment and cigarette smoking (r=0.4; P=0.02).

CONCLUSIONS

REP measurements did not discriminate between screenees with a history of adenomas and adenoma free screenees. Long-term lifestyle habits, gender, and age were associated with REP levels and need to be considered when evaluating human intervention studies.

Proliferative patterns of rectal mucosa as predictors of advanced colonic neoplasms in routinely processed rectal biopsies

OBJECTIVES

We sought to determine whether the evaluation of rectal cell proliferation in routinely processed rectal biopsies of apparently normal mucosa can predict the presence of advanced colonic neoplasms.

METHODS

Fifty consecutive patients, who did not meet any of the following exclusion criteria, underwent total colonoscopy. Patients with nonadvanced adenomas, inflammatory bowel disease, hereditary predisposition to colonic cancer, or a history of colonic neoplasms were excluded. Patients with neoplasms in the distal 40 cm of the large bowel were also excluded. An adenoma was considered advanced if it had a diameter > 1 cm, or villous or severe dysplasia histology were present. In 26 of the 50 patients (Group A: 16 men, 10 women; mean age, 65 yr) advanced colonic neoplasms (advanced adenomas or cancer) were detected; in the remaining 24 (Group B: 13 men, 11 women; mean age, 66 yr) the large bowel was free of neoplasms. In all patients the proliferative patterns of apparently normal rectal mucosa were evaluated using the monoclonal antibody MIB-1 to assess the expression of Ki-67 antigen in routinely processed tissues. Proliferation index for the entire crypt, as well as proliferation indices for each of the five equal compartments, into which the crypt had been divided longitudinally, were calculated for each patient.

RESULTS

The mean proliferation indices were similar between the two groups compared. The mean proliferation index for the upper crypt compartments (4 + 5) in the Group A patients was significantly higher than for those of the Group B patients (p < 0.01). Multivariate stepwise logistic regression analysis revealed that among gender, age, and proliferative parameters, the pattern of cell proliferation in the upper rectal crypt (4 + 5) compartment was the only predictor of advanced colonic neoplasms (beta = 11.01, p < 0.001).

CONCLUSIONS

Our data suggest that the evaluation of the upward expansion of the rectal crypt proliferative zone in routinely processed rectal biopsies of apparently normal mucosa appears to predict the presence of advanced colonic neoplasms. These preliminary results should be confirmed in larger studies.

Effect of dietary phytosterols on rat tissue lipids

The present study was designed to examine the incorporation of phytosterols (PS) in membranes and tissues of rats fed a diet containing 2% PS in the presence of 0.2% cholic acid for 22 days. The control diet contained 12 mg PS/100 g compared with 2,012 mg/100 g. Liver, kidney, testis, and prostate microsomes, plasma, and epididymal fat pads were examined for sterols. Fatty acid composition and phospholipid pattern were also examined in some tissues. The PS diet resulted in a fivefold increase in plasma PS compared with controls. PS was found to accumulate in adipose tissue and liver microsomes in rats fed the PS-supplemented diet. There was no effect of PS incorporation on microsomal cholesterol content, except in the testes, in which dietary PS reduced cholesterol content by 25%. Dietary PS increased 20:4n-6 and 22:5n-3 fatty acids in membranes of the liver, testis, and prostate but decreased 16:1 in liver microsomes. PS incorporation had no effect on the phospholipid pattern of the liver and testis.

Effect of dietary phytosterols on cell proliferation and protein kinase C activity in rat colonic mucosa

The present study investigated the role of phytosterols in colonic cell proliferation and examined the possible role of protein kinase C (PKC) in this process. A total of 18 male Sprague-Dawley rats weighing 240-270 g were fed, for a period of 22 days, one of three experimental diets: a control diet, a diet supplemented with 0.2% cholic acid, or a diet supplemented with 0.2% cholic acid + 2% dietary phytosterols. Two hours before decapitation, animals were injected with 5'-bromo-2'-deoxyuridine (BrdU, 50 mg/kg body wt ip). Cell proliferation in the proximal colon was measured using a monoclonal antibody to BrdU. PKC activity in the proximal colonic mucosa was assayed using a myelin basic protein as a substrate. Cell proliferation was significantly increased by 276% with 0.2% cholic acid feeding compared with controls. The presence of 2% phytosterols in the diet abolished the cholic acid-induced hyperplasia. Cholic acid induced a 31% expansion of the proliferative zone. Only the cytosolic PKC was significantly lower in the phytosterol-fed group. Neither the total PKC nor the particulate PKC demonstrated an effect of phytosterols on enzyme activity. In conclusion, we found that dietary supplementation with 2% phytosterol has a significant protective effect on enhanced cell proliferation and that this effect is not mediated through the PKC system.

Relationship among colonocyte proliferation, differentiation, and apoptosis as a function of diet and carcinogen

To determine the relationship among colonocyte proliferation, differentiation, and apoptosis as a function of fiber and carcinogen, we conducted a 2 x 2 factorial design study with two fibers (pectin or cellulose) and two injection protocols (azoxymethane or saline) in male Sprague-Dawley rats. Rats were killed six weeks after the injections, and in vivo cell proliferation was measured by incorporation of bromodeoxyuridine into DNA, differentiation by binding of the lectin Dolichos biflorus agglutinin, and apoptosis by immunoperoxidase detection of digoxigenin-labeled genomic DNA. In the proximal colon, pectin decreased differentiation and apoptosis, resulting in a greater number of cells per crypt column. In the distal colon, pectin increased cell proliferation, resulting in more crypts per millimeter of colon and a greater number of surface cells. Azoxymethane increased cell proliferation and decreased differentiation and apoptosis in the proximal and the distal colon. This resulted in a greater number of surface cells proximally and more crypts per millimeter of colon distally. These results illustrate the importance of considering all three parameters (proliferation, differentiation, and apoptosis) when evaluating neoplastic growth.

Antiproliferative effects of the enantiomers of flurbiprofen

Nonsteroidal antiinflammatory drugs (NSAIDs) are recognized for inhibiting growth of colon tumors in animal models, and for reducing the risk of colon cancer in humans. The mechanisms involved have not been established, but are thought to be related to reduced prostaglandin biosynthesis. The present study investigates the effect of COX-inhibiting and non-COX-inhibiting enantiomers of flurbiprofen on rat colonocyte proliferation. Intestinal ulceration was used as a surrogate indicator of COX inhibition. Sprague Dawley rats were treated orally with 6.3 mg/kg of R- or s-flurbiprofen or vehicle. Colonocyte labeling index and small bowel ulcer index were measured. R-flurbiprofen and S-flurbiprofen significantly reduced colonocyte labeling index, by 34% and 23% respectively, compared with vehicle. R-flurbiprofen caused minimal ulcer formation (4.48 mm2) compared with S-flurbiprofen (94.4 mm2). These findings suggest that R-flurbiprofen-mediated control of colonocyte proliferation is independent of prostaglandin biosynthesis.

Diet, body mass index, and colonic epithelial cell proliferation in a healthy population

Using 63 healthy subjects, we conducted an observational study to assess associations between colonic epithelial cell proliferation and dietary intake of selected nutrients. Study subjects exhibited no personal or family history of colon carcinoma, familial polyposis coli, sporadic adenomas, or chronic inflammatory bowel diseases. In this study population, a negative association between the tritiated thymidine-labeling index and dietary intake of calcium (p < 0.003) was found after the effects of age, sex, body mass index (kg/m2), dietary fat, and total energy were controlled in a linear regression model. The association for calcium indicated that a daily calcium intake of 1,200 mg was associated with a predicted thymidine-labeling index of 6%. In the same model, a positive association with the thymidine-labeling index was found for body mass index (p < 0.002) and was suggested for female gender (p < 0.09). No association was found between the thymidine-labeling index and intake of fat, protein, carbohydrate, retinol, ascorbic acid, phosphorus, or iron. Repeat measures of diet in this investigation were used to estimate a subject's daily intake of selected nutrients.

Rectal proliferation and polyp occurrence in patients with familial adenomatous polyposis after sulindac treatment

BACKGROUND/AIMS

Sulindac, a nonsteroidal anti-inflammatory drug (NSAID), decreases the occurrence of polyps in patients with familial adenomatous polyposis (FAP). The effects of colectomy with ileorectal anastomosis (IRA) and sulindac treatment on rectal mucosa proliferation and polyp occurrence were examined in patients with FAP.

METHODS

The number and size of rectal polyps were measured with colonoscopy. The labeling index, the percentage of labeled cells per crypt compartment, was assessed in rectal biopsy specimens with [3H]thymidine incorporation and autoradiography in 6 non-IRA and 14 IRA patients before and after treatment with 200 mg of sulindac/day for 60 days.

RESULTS

The IRA patients had a lower labeling index and a decrease in the percentage of labeled cells in the upper compartment of the crypt (P < 0.01) relative to non-IRA subjects. Sulindac did not influence the labeling index and the distribution of labeled cells along the crypt. On the contrary, a dramatic decrease in the size and number of polyps was observed after sulindac treatment (P < 0.001).

CONCLUSIONS

The persistence of a abnormal mucosal proliferation after sulindac therapy, in spite of the reduction of polyp number, suggests caution in assuming a lower risk of rectal cancer in patients with FAP.

The identification of high and low risk groups for colorectal cancer using rectal mucosal crypt cell production rate (CCPR)

Rectal mucosal proliferation was measured in 116 individuals using the metaphase arrest technique crypt cell production rate (CCPR). CCPR was found to be significantly elevated in individuals with adenomas (n = 42, CCPR = 13 cc c-1h-1, range 7-25 Cl 10-15) compared with normals (n = 21, CCPR = 10 cc c-1h-1 range 5-24 Cl 7-11, Mann-Whitney P = 0.001 z = 3.2). Mucosal proliferation was increased among individuals who were undergoing adenoma follow up but in whom no further adenomas were found (n = 37 CCPR = 12 range 5-26 cc c-1h-1 Cl 10-14) compared to controls (Mann-Whitney P = 0.01 z = 2.4) Proliferation in vegetarians i.e. low risk (n = 16) was similar to controls. Measurement of proliferative indices in rectal mucosa by the stathmokinetic technique CCPR can discriminate between high and low risk groups for colorectal cancer.

Effect of cooked meat on micronucleus frequency

The possibility that inclusion of cooked meat in the diet could elevate chromosome damage risk was investigated in mice fed either a cereal diet only or a cereal diet supplemented with mutton cooked by microwaving, pan-frying or charcoal-barbecueing. The meat was provided as a supplement to the standard cereal-based diet on an approximately one-to-one basis. Chromosome damage indices included the cytokinesis-block micronucleus assay in spleen lymphocytes, the bone marrow micronucleus assay in erythrocytes and two versions of the colonic micronucleus assay. These indices were assessed after 3 or 6 months of feeding, and under each circumstance no increment in the micronucleus frequency in any of the tissues could be detected in the groups fed cooked meat when compared with each other or with the group fed the cereal diet only. There was also no correlation between the micronucleus index in lymphocytes and body weight. These data suggest that, over the time-frame studied, inclusion of meat in the diet and the extent to which meat is cooked are unlikely to be important variables affecting the micronucleus index.

Mitotic activity in colorectal mucosa of healthy subjects in two Italian areas with different dietary habits

The proliferative activity was evaluated in colorectal biopsies of 39 healthy subjects living in two distinct geographical areas, Trieste in northern and Florence in central Italy. Subjects living in Trieste had a significantly higher mitotic activity compared with subjects living in Florence (mitoses/cells counted x 100 were 0.17 +/- 0.04 in Trieste and 0.089 +/- 0.02 in Florence). The results of a dietary questionnaire also showed that subjects in Trieste consumed significantly fewer starches, fibers, nitrites, and proteins. However, no correlation was evident between the consumption of these nutrients and intestinal proliferation.

Colonic epithelial proliferation indices before and after colon cancer removal

Rectal mucosal (epithelial) proliferation labeling indices (LI) have been widely used as a risk marker for colorectal cancer and as an intermediate end-point in chemoprevention studies. The purpose of this study was to determine whether the presence of cancer preoperatively altered the LI and whether these LI could be used over the long term as a marker for colon cancer. We studied 25 patients (18 with colorectal cancer and 7 with benign colonic diseases) who were admitted for colonic resection. Biopsies for thymidine LI were taken before, during, and 4 and 7 months after the operation. The preoperative LI of cancer patients was higher, but not significantly, than that of noncancer patients (5.22 +/- 3.54 and 4.11 +/- 1.34%, respectively, p = 0.28). The intraoperative LI was significantly higher than the preoperative LI (8.08 +/- 4.00 and 4.90 +/- 3.07%, respectively; p = 0.004). After 4 and 7 months, the LI was not significantly different from the preoperative LI (p = 0.60 and 0.89, respectively). Resection of a colonic segment did not affect the level of proliferation over time. Therefore, it is unlikely that LI can be used as a marker to predict local recurrence after curative resection of colorectal cancer.

An epidemiologic perspective on biomarkers

The authors discuss biological markers from an epidemiologic perspective, emphasizing the importance of integrating biomarkers into large-scale observational and intervention studies. Whereas any biologic phenomenon can be considered a biomarker, an intermediate end-point is defined as being on the causal pathway between exposure and disease. An intermediate end-point is a valid surrogate for a disease in relation to a given exposure if, and only if, that exposure causes a similar change in the occurrence of both the intermediate end-point and the disease. Cancer studies using surrogate end-points may be shorter, smaller and cheaper than those using malignancy per se as an outcome. Three types of studies may be carried out to determine whether a given biomarker is an intermediate end-point and whether it can serve as a surrogate: (i) exposure-marker studies, (ii) marker-disease studies, and (iii) studies comprising all three elements, exposure, marker, and disease. The authors discuss statistical aspects of these three types of studies and provide examples from investigations of alcohol-hormone-breast cancer, diet-epithelial proliferation markers-large bowel adenomatous polyps, and reproductive risk factors-human papillomavirus infection-cervical cancer.

The study of markers of biological effect in cancer prevention research trials

Biological markers may provide a valuable tool for the development of cancer prevention agents, for monitoring patient compliance to a selected intervention, or for further defining the carcinogenic process. This discussion focuses on markers of biological effect and the rationale for their use in cancer prevention trials. Recent studies with biological markers are investigating their incorporation into phase-I, -II, and -III chemoprevention clinical trial designs. Their use in clinical studies is expected to increase the number of agents that may be evaluated and to provide valuable information on the biological effectiveness of agents, doses, and schedules. Markers may also provide information to help in selecting high-risk groups for prevention research, and to indicate the pathways inhibited and the stage of carcinogenesis affected. Such information may prove of crucial importance in strengthening the rationale for long-term trials and other ancillary research. Biomarker research for colon carcinogenesis is discussed, including examples of a number of recent trials that may influence future progress in this area of prevention research. A crucial step in this process is marker validation as an aspect of major prospective observational and intervention studies where cancer incidence is the endpoint. We cannot be fully confident of markers as intermediate endpoints until the evidence from clinical trials is sufficiently strong to support major public health initiatives for prevention.

Reduction of mucosal crypt cell proliferation in patients with colorectal adenomatous polyps by dietary calcium supplementation

The crypt cell production rate was measured in 14 patients with adenomatous colorectal polyps, 17 patients with colorectal cancer and 12 control subjects. The median (interquartile range) rate (cells per crypt per hour) was found to be significantly higher (P less than 0.001) in the polyp (2.45 (1.94-3.20)) and cancer (3.01 (2.35-3.68)) groups compared with controls (1.25 (0.70-1.85)). A double-blind cross-over study was performed in patients with adenomatous polyps consisting of 2 months' treatment, 2 weeks' washout, followed by 2 months' treatment with dietary calcium supplementation (1.25 g day-1) versus placebo. A significant reduction in the crypt cell production rate occurred with calcium treatment compared with the placebo (1.25 (0.6-2.25) versus 2.15 (1.58-3.08) cells per crypt per hour, P = 0.035). This study demonstrates a significant reduction in mucosal cell proliferation by dietary calcium supplementation in patients with adenomatous polyps. Such treatment may be worthy of further investigation in patients at high risk of developing colorectal polyps.

Gastrointestinal cancer: pathogenesis, risk factors and the development of intermediate biomarkers for chemoprevention studies

Dietary, environmental and genetic factors contribute to the etiology, pathogenesis and risk for gastrointestinal cancers. Measurements of cell proliferation and differentiation further identify abnormal cellular properties associated with increased susceptibility to gastrointestinal cancer. In precancerous esophagus, the proliferative compartment increases in size, increased ploidy and dysplasia develop, and epithelial cells express abnormal cytokeratins and ectopic tumor-associated antigens. In precancerous stomach, increased proliferative activity and metaplasia develop. Intestinal enzymes and mucins are expressed and normal gastric antigens are replaced by intestinal or embryonic antigens. In flat colonic mucosa and in colonic adenomas, expansions of the proliferative compartment occur. Gene expression is modified, gene deletions occur and blood group-related antigens are modified as the cells undergo abnormal differentiation and develop into adenomas and carcinomas. Chemopreventive regimens are now being tested to determine whether they modify such intermediate biomarkers toward normal levels characteristic of lower risk for neoplasia. It is anticipated that the utilization of intermediate biomarkers in chemoprevention studies may permit more novel chemopreventive regimens to be tested in human subjects than heretofore was possible.

Effect of short-chain fatty acids on the human colonic mucosa in vitro

Fermentable dietary fiber components are known to stimulate colonic crypt proliferation. As these compounds are rapidly degraded to short-chain fatty acids (SCFAs) by the anaerobic microflora, the hypothesis was tested that this trophic effect of fiber may be mediated by SCFAs. Biopsies were taken from normal cecal mucosa of 45 individuals during routine colonoscopy. They were incubated for 3 hours with sodium salts of SCFAs at physiological concentrations (three SCFAs = acetate 60 mmol/L + propionate 25 mmol/L + butyrate 10 mmol/L; acetate 60 mmol/L; propionate 25 mmol/L; butyrate 10 mmol/L) or equimolar NaCl (control). Cell proliferation was measured autoradiographically by subsequent pulse labeling with [3H]thymidine (1 hour). The labeling index (number of labeled cells divided by the total number of cells) was computed for the crypt as a whole and for five equal crypt compartments (compartment 1 = crypt base, compartment 5 = crypt surface). Cecal crypt proliferation was raised significantly in all incubation experiments with SCFAs. Butyrate (10 mmol/L, increase + 89%) and propionate (25 mmol/L, + 70%) were as effective in stimulating proliferation as the combination of three SCFAs (+103%), although the effect of acetate (+31%) was minor. Increasing the butyrate concentration to 25 mmol/L or 60 mmol/L did not result in a further increase of cell labeling. SCFAs stimulated proliferation in the basal three crypt compartments only. An expansion of the proliferative zone to compartments 4 and 5 was not observed. SCFAs, especially butyrate and propionate, are luminal trophic factors for the cecal epithelium.(ABSTRACT TRUNCATED AT 250 WORDS)

Interspecies comparison of calmodulin binding proteins throughout the gastrointestinal tract: comparison with human colon adenomas and adenocarcinomas

Calmodulin is an ubiquitous cytoplasmic protein which mediates many of the actions of calcium on intestinal tissue including regulation of growth and differentiation of normal and neoplastic cells. Using a biotinylated calmodulin overlay system, we compared the pattern of calmodulin binding proteins throughout the gastrointestinal tract of mice, rats, rabbits, and humans, and in human colonic adenomas and adenocarcinomas. A common calmodulin binding protein of 67 kDa was found in membrane and cytosolic fractions of oesophagus, stomach, proximal and distal small intestine, and colon from all four species. In human tissue this 67 kDa protein was present in greatest concentration in stomach tissue. Furthermore, a 67 kDa binding protein was the major calmodulin binding protein from human stomach and ileum as determined by ion exchange and calmodulin affinity chromatography. A similar pattern of binding proteins was noted between rabbit and human cytosolic fractions; proteins of 60/67 kDa and 105 kDa were present in stomach tissue. A 94 kDa protein was present in samples of rabbit and human ileum but not of mouse or rat. A similar pattern of calmodulin binding proteins was seen in normal and neoplastic large bowel tissue, apart from one of nine adenocarcinomas, where a distinct 54 kDa band was noted in both cytosolic and membrane fractions. The results of this study show interspecies and organ differences between calmodulin binding proteins, but suggest that a 67 kDa protein is the major binding protein present throughout normal gastro-intestinal tract and neoplastic human tissue.

Mucosal cell proliferation of the rectal stump in ulcerative colitis patients after ileorectal anastomosis

The proliferative activity and polyamine levels of the rectal epithelium in unoperated ulcerative colitis patients and in ulcerative colitis patients after total colectomy and ileorectal anastomosis were determined and compared with control subjects. Cell proliferation was evaluated in rectal biopsies by in vitro 3H thymidine incorporation by measuring the labeling index and the position of labeled cells along the crypt; polyamines were determined with a chromatographic method. In ulcerative colitis patients the labeling index was significantly increased, and labeled cells were shifted toward the upper part of the crypt when compared with controls. Ileorectal anastomosis patients showed a normalization of the labeling index and a distribution of labeled cells similar to controls. Polyamine levels were also increased in ulcerative colitis patients; in ileorectal anastomosis patients, the level of polyamines was decreased in respect to unoperated patients and return to normal values except for spermine. Because the increased proliferation and higher polyamine levels are related to increased colon cancer risk, our results confirm that ulcerative colitis is a risk factor for the development of carcinoma. Ileorectal anastomosis may reduce this risk through a normalization of mucosal cell proliferative activity and of some polyamine levels.

Effect of high-fat and low-fiber meals on the cell proliferation activity of colorectal mucosa

Normal healthy volunteers (n = 43) were divided into four groups that received diets providing low or high levels of dietary fat (33 or 96 g/day) and low or high levels of dietary fiber (6 and 41 g/day) for a period of five days. Proliferation was assessed with tritiated thymidine labeling of three rectal biopsies. After five days on the prescribed diets, the average thymidine labeling index (LI) of the group on the high fat-low fiber diet was only 25% higher than the average LI of the group on the low fat-high fiber diet, a difference that is not statistically significant. We conclude that a short-term increase in dietary fat and decrease in dietary fiber does not result in a large increase in cell proliferation rate.

Cholecystectomy and right colon cancer in Puerto Rico

A case-control study was undertaken to evaluate the possible relationship between cholecystectomy and right colon cancer. Two hundred patients with adenocarcinoma of the cecum or ascending colon (diagnosed between 1984 and 1989) were compared with 200 matched neighborhood controls. Cholecystectomy history was obtained through interviews using structured questionnaires and subsequently validated from hospital records. A statistically significant association (odds ratio = 2.14) was found between right colon cancer and a history of prior cholecystectomy. The altered bile metabolism which occurs after removal of the gallbladder may have a carcinogenic effect on the right colon. Dietary habits of the colon cancer patients in our study were consistent with prior reports in the literature, showing that this group has a lower intake of vegetables and cereal fiber than the control population.

Colonic polyamine content and ornithine decarboxylase activity as markers for adenomas

Polyamine content (putrescine, spermidine, and spermine) or ornithine decarboxylase (ODC) activity was measured in normal-appearing colonic mucosa from patients undergoing colonoscopy. Comparisons were made between those with and those without adenomatous polyps. Colonic mucosal polyamine content was measured in 44 persons. Mean putrescine content was 1.25 +/- 0.26 (SE) nmol/mg protein in 22 patients with adenomatous polyps compared with 0.53 +/- 0.12 nmol/mg protein in patients without polyps (P less than 0.02). Tissue content of spermidine and spermine did not differ between these two groups. Ornithine decarboxylase activity was measured in tissue from 45 patients. Mean ODC activity was 2.84 +/- 0.73 pmol/hr/mg protein in 23 persons with adenomatous polyps compared with 1.15 +/- 0.18 pmol/hr/mg protein in persons without polyps (P less than 0.05). Mucosal putrescine and ODC activity are elevated in patients with adenomatous polyps compared with patients without polyps. These biochemical markers may prove helpful in improving surveillance methods for colorectal cancer and premalignant adenomatous polyps.

Short-term tests and long-term prospects for colon cancer prevention

Five assay systems that have been used for identifying possible carcinogenic factors responsible for human colon cancer are described. These are: Salmonella, colonic micronuclei, colonic epithelial proliferation and aberrant crypt assays, and polyp recurrence trials. The assays have led to the development and testing of 7 hypotheses. A review of this process points to the importance of specificity in the assay system.

Rectal epithelial proliferation characteristics of first degree relatives of sporadic colon cancer patients

Hyperproliferation of rectal epithelium is characteristic of families at high genetic risk for large bowel neoplasia, but has not been well-documented in families of sporadic colorectal cancer patients. This was studied in 119 such first degree relatives and 44 comparison subjects without this family history. All screened negative for large bowel neoplasia. Within the family group proliferation was significantly higher in the men and those aged less than 45 years, also higher (insignificantly) in non-Europeans and those having greater than 1 first degree colorectal cancer relative. In comparison to the nonfamily group the labelling index (LI) of the relatives showed a significant negative correlation with age (R = -0.20, P = 0.03). Within this family group the probability of having an elevated LI (greater than 6.0%) was greatest in the young (less than 50 years old) men (odds ratio = 2.0). Measurements of rectal epithelial proliferation (REP) in these first degree relatives, at a young age, might help delineate a high risk subgroup for prospective primary and secondary intervention.

Restoration of colorectal continuity reverses atrophy in human rectal mucosa

Cell kinetic activity and adaptive response of rectal mucosa from patients with Hartmann's procedure were studied before and after restoration of colorectal continuity. Patients without colostomy and with normal rectal mucosa were used as controls. Autoradiography of in vitro labeled mucosal samples with [3H]thymidine was used. The proliferative activity in the rectal crypts was estimated by measuring labeling and mitotic indices, total DNA of isolated crypts, and total crypt cell numbers. One hundred forty days after creating a proximal end colostomy, labeling index (P less than 0.05), mitotic index (P less than 0.01), DNA content per crypt (P less than 0.05), and number of cells per crypt (P less than 0.05) decreased significantly compared to control values. Restoration of colorectal continuity resulted in a significant increase of the labeling index (P less than 0.05), the mitotic index (P less than 0.01), the DNA content per crypt (P less than 0.05), and the cell number per crypt (P less than 0.05). There were no significant differences between the postclosure values and the controls. These data indicated that excluding the human rectal mucosa from fecal stream determined a mucosal atrophy that could be reversed by restoration of colorectal continuity.

Influence of demographic parameters on rectal epithelial proliferation

Measurement of rectal epithelial proliferation is now being used as a biomarker for assessing risk for colorectal cancer and response within dietary intervention studies. We examined the possible confounding effects of demographic parameters on the proliferation of 52 healthy middle-aged volunteers without known risk factors for colorectal cancer. No significant effects on proliferation of age, sex or ethnic grouping were found other than marked urban-rural differences amongst men. We hypothesise that these could be explained by differences in dietary habits and their deleterious effects in the older male population. Careful matching of controls are probably needed in order to demonstrate the minor changes in mucosal proliferation that could reflect risk for neoplasia. Further human studies are needed to examine the effects of diet and extremes of age on proliferation.

Heterogeneity in the response of familial polyposis epithelial cells and adenomas to increasing levels of calcium in vitro

A biomarker of increased risk for colon cancer is abnormally high proliferation of colonic epithelial cells. The authors developed an in vitro assay that measures the ability of human colonic epithelial cells that are in progressive stages of abnormal development to respond to direct application of calcium as the chloride in tissue culture medium. Incorporation of 3H-thymidine and autoradiography in situ was employed to measure the number of proliferating cells cultured at 0.1 mM CaCl2, the optimum level for growth, and 2.2 to 5 mM, both levels achievable in the colonic lumen. Abnormal cell proliferation was reduced in biopsies from 13 of 14 patients without familial polyposis but at increased risk for colon cancer because of previous colonic neoplasms or familial association; in cells from three of four asymptomatic individuals in familial polyposis families at risk for that disease; and in cells of three of ten patients symptomatic with familial polyposis. Growth of tubular adenoma cells from two of seven familial polyposis patients was also inhibited by calcium. Growth inhibition was not observed in more advanced colon tumors including eight adenomas, either villotubular or villous, and five carcinomas. These findings indicate heterogeneity within the familial polyposis phenotype for the normal cellular response to growth inhibition by calcium, and a further loss of response to calcium as these cells progress toward malignancy.