Outcomes in patients with fractured ribs: middle aged at same risk of complications as the elderly

AIMS

Rib fractures occur in up to 10% of hospitalised trauma patients and are the most common type of clinically significant blunt injury to the thorax. There is strong evidence that elderly patients have worse outcomes compared with younger patients. Evolving evidence suggests adverse outcomes start at a younger age. The aim of this study was to explore the effect of age on outcomes in patients with rib fractures in Northland, New Zealand.

METHOD

A two-year retrospective study of patients admitted to any Northland District Health Board hospital with one or more radiologically proven rib fracture was performed. Patients with an abbreviated injury scale score >2 in the head or abdomen were excluded. The study population was stratified by age into three groups: >65, 45 to 65 and <45 years old.

RESULTS

170 patients met study inclusion criteria. Patients <45 had a significantly shorter length of stay (LOS) and lower rates of pneumonia compared to patients 45 and older, despite a higher Injury Severity Score and pulmonary contusion rate. There was no difference seen between groups in rates of intubation, ICU admission, mortality, empyema or acute respiratory distress syndrome.

CONCLUSION

This study found higher rates of pneumonia and an increased LOS in patients 45 and older despite their lower overall injury severity when compared to patients under 45. Patients aged 45-64 had outcomes similar to patients >65. Future clinical pathways and guidelines for patients with rib fractures should consider incorporating a younger age than 65 in risk stratification algorithms.

Promotion of the mediterranean diet incancer long-survivors by means of the Med-Food Anticancer Program: a pilot study

BACKGROUND

The intervention "Med-Anticancer Food Program" has proven to be effective in promoting the Mediterranean Diet, significantly increasing the Mediterranean Adequacy Index in healthy subjects. There are no studies that have investigated the effectiveness of this intervention in individuals who have had a diagnosis of cancer.

OBJECTIVE

To perform a pilot study to assess the opportunity of employing the methodology of the Med-Anticancer Food Program in order to encourage "long-term cancer survivors" to adhere to the Mediterranean Diet, as well as healthy people, and this in order to apply the program to larger groups.

METHODS

From the residents' register of Foggia, a city in southern Italy, forty adults of both sexes, over 25 years of age, were recruited at random and assigned (1:1) as follows: - Twenty healthy subjects to the intervention-1 group - Twenty long-term cancer survivors to the intervention-2 group. The Med-Anticancer Food Program was applied to both groups with an articulated intervention 11 weeks long, followed by a 52-week period of follow up. By means of a food diary of the last 3 days, the Mediterranean Adequacy Index values were calculated before intervention (T0), after a period of 11 weeks of interventions (T1) and at the end of the 52 weeks of follow-up period (T2). The H0 hypothesis of the study was that there are no differences between the two interventions in reaching by T1, and maintaining at T2, values of Mediterranean Adequacy Index around 7, considered the optimum for adherence to the Mediterranean diet.

RESULTS

Out of the subjects assigned to the intervention-1 group (n = 20), 11 subjects have completed the 52-months follow-up (55.0% ); for intervention-2, 16 (80%) out of 20 have completed it. The average age of subjects was 52.1 years. The Mediterranean Adequacy Index, of intervention-1 group significantly increased from 2.8 (T0) to 9.2 (T1) and to 9.0 (T2) (p <0.0001); whereas, in the intervention-2 group, Mediterranean Adequacy Index moved from 2.4 (T0) to 10.2 (T1) and to 9.3 (T2) (p <0.0001). The difference of Mediterranean Adequacy Index between the two study groups at T1 and T2 was not significant. Such non-significance persists also after the stratification by sex and age obtained with Mantel-Haenszel procedure. The performance of the values of the laboratory parameters considered (folic acid, total cholesterol, alkyl resorcinol) was similar in the subjects of both intervention 1 and 2, without any difference, while considered at a basal level T0, at T1 and at the end of the follow-up period (T2).

CONCLUSIONS

The results of our work suggest the feasibility of conducting the Med-Anticancer Food Program in long-term cancer survivors. The results of the pilot study show that such intervention, carried on a small number of long term cancer survivors, is adequate to assess its feasibility but, due to the limited size of our study, a confirmation is required through larger nutritional prevention intervention studies.

A quinazoline-based HDAC inhibitor affects gene expression pathways involved in cholesterol biosynthesis and mevalonate in prostate cancer cells

Chronic inflammation can lead to the development of cancers and resolution of inflammation is an ongoing challenge. Inflammation can result from dysregulation of the epigenome and a number of compounds that modify the epigenome are in clinical use. In this study the anti-inflammatory and anti-cancer effects of a quinazoline epigenetic-modulator compound were determined in prostate cancer cell lines using a non-hypothesis driven transcriptomics strategy utilising the Affymetrix PrimeView® Human Gene Expression microarray. GATHER and IPA software were used to analyse the data and to provide information on significantly modified biological processes, pathways and networks. A number of genes were differentially expressed in both PC3 and DU145 prostate cancer cell lines. The top canonical pathways that frequently arose across both cell lines at a number of time points included cholesterol biosynthesis and metabolism, and the mevalonate pathway. Targeting of sterol and mevalonate pathways may be a powerful anticancer approach.

Differential modification of genetic susceptibility to childhood eczema by two probiotics

BACKGROUND

In a double-blind, randomized, placebo-controlled birth cohort, we have recently shown a beneficial effect of Lactobacillus rhamnosus HN001 (HN001) for the prevention of eczema in children through to 6 years of age but no effect of Bifidobacterium animalis subsp lactis HN019 (HN019).

OBJECTIVE

Among this cohort of children, we aim to investigate whether these probiotics could modify the expression of genetic predisposition to eczema conferred by genetic variation in susceptibility genes.

METHODS

Thirty-three eczema susceptibility SNPs (in eleven genes) were genotyped in 331 children of European ancestry.

RESULTS

Children who carried a genetic variant that put them at a high risk of developing eczema were less likely to develop eczema if they had been randomized to the HN001 intervention group compared to those in the placebo group. HN019 was also able to protect against the effects of some SNPs. As well as modifying genetic susceptibility to childhood eczema, HN001 was also found to modify genetic susceptibility to eczema severity and atopy risk.

CONCLUSION AND CLINICAL RELEVANCE

This is the first study to show an effect of a probiotic on reducing eczema risk amongst those with particular eczema-associated genotypes. Our findings suggest that Lactobacillus rhamnosus HN001 may be particularly effective in preventing eczema in children with specific high-risk genotypes.

A possible mechanism of toxicity by the antidepressant amoxapine based on its effects in three in vitro models

When the antidepressant amoxapine is taken in overdose, it can cause metabolic acidosis, brain damage and sometimes death. In previous studies, biochemical evidence has been presented that amoxapine disrupts reactions of membrane-associated multi-enzyme complexes, and mitochondrial energy conservation may be one of the first systems affected. Three in vitro systems were investigated to determine whether general membrane disruption or more specific mitochondrial effects of amoxapine could be responsible for toxicity and for lactic acid accumulation. In Saccharomyces cerevisiae, increased amoxapine concentrations led to decreased oxygen uptake associated with decreased survival of cells. In Chinese hamster ovary cells in culture, an initial increase in oxygen uptake was observed up to 10 mug amoxapine/ml and a decrease thereafter. At drug levels that caused an increased oxygen uptake, there was increased lactic acid output by cells, but no observable toxicity. At higher drug levels, the decreased oxygen uptake was accompanied by cell death, reduced lactic acid output and a change in the mitochondrial cristae configuration. Cell death in both of the above systems was attributed to interference with energy conservation. Isolated, beating guinea-pig hearts perfused with 5 mug amoxapine/ml stopped after 13 min, but no lactic acid accumulated. This may be explained by the membrane-stabilizing activity of the drug. In an arrested perfused heart, increased concentrations of amoxapine stimulated oxygen consumption and lactic acid production. Hence, membrane-stabilizing activity alone is not adequate to explain the action of amoxapine on isolated cells, and on the perfused arrested heart, or the clinical pattern of overdose, and disruption of energy conservation in cells is likely to be involved also.

[Nutrition prevention intervention for cancers: "Med-Food Anticancer Program"]

Several studies recommend the Mediterranean diet and daily physical activity to prevent cancer development. These recommendations, however must be transformed into public health structured programmes, so that they assume operational effectiveness. The aim of the diet and lifestyle intervention called Med-Food Anticancer Program (MFAP) is to promote the Mediterranean diet and physical activity in the adult population. In particular; the target for participants in the intervention is the increased consumption of legumes, fish, whole grain bread and cereals, fruits and vegetables, and the decreased consumption of meat, cheese and foods of animal origin. At the same time, it is recommended to make at least ten thousand steps a day. Two studies have shown the effectiveness of MFAP.

Blastomycosis of the skull base

Blastomycosis is usually considered a pulmonary or cutaneous disease. A patient with blastomycosis of the infratemporal fossa temporal bone and sinuses without pulmonary disease is presented. Extensive skull base involvement required surgical debridement for relief of pain, and long-term systemic antifungal therapy. The literature is reviewed and discussed.

Training the teachers for improving primary schoolchildren's fruit and vegetables intake: a randomized controlled trial

Effectiveness comparison of different school-based nutrition education interventions to improve fruit and vegetable (F&V) consumption in schoolchildren not yet well researched. We evaluated the effectiveness of two school-based interventions promoting fruit and vegetable intake among Italian schoolchildren. In this randomized intervention trials, the first intervention was conducted by schoolteachers who attended a nutritionist-led training course (group-1), the second intervention conducted by schoolteachers who performed a self-training course (group-2). Thirty-two second to fifth-grade elementary classes enrolling 96 schoolteachers and 813 schoolchildren were randomized, and assigned to the two different nutrition education interventions. 804 students completed the study. By the end of the study, the group-1 (n = 409) followed by the teachers who attended a nutritionist-led course successfully increased the consumption of fruit and vegetables: in 183 (44.7%) and 157 (38.3%) schoolchildren respectively; the group-2 (n = 395) with teachers who performed a self-training course reported an increased consumption of fruit and vegetables in 81 (20.5%) and 76 (19.2%), respectively. This study indicates that a school-based nutrition education conducted by teachers who attended a nutritionist-led training course has a significant impact on primary school-age children's F&V intake.

Randomized, controlled nutrition education trial promotes a Mediterranean diet and improves anthropometric, dietary, and metabolic parameters in adults

Several studies have shown that uptake of a Mediterranean diet could prevent many chronic diseases, such as cancer. However, the effectiveness of Mediterranean diet promotion interventions has not been well researched. The aim of this study was to evaluate the effectiveness of a nutrition education intervention for promoting the Mediterranean diet, by assessing changes in anthropometric, physical activity, dietetic and metabolic parameters in healthy adult subjects, before and after the intervention. Eighty participants, both sexes, aged 51-59 years, were randomly assigned in a 1:1 ratio to the intervention or the control group. The intervention group participated in the Med-Food Anticancer Program (MFAP), designed to promote a Mediterranean diet. This was organized into 15 weeks of intensive training and 10 weeks of consolidation. Participants of the two groups were assessed at baseline (T0) and after 25 weeks (T1) for anthropometric, physical activity, dietetic, and metabolic parameters. The hypothesis was that subjects participating in MFAP would show an improvement in these parameters. The primary endpoint was an improvement of the Mediterranean Adequacy Index (MAI), calculated by dividing the percentage of total energy from typical Mediterranean food groups by the percentage of total energy from non-typical Mediterranean food groups. At T1, the intervention group showed a significant decrease in body weight (-8.3%, P = 0.045), body mass index (-12.4%, P = 0.05), cheese (53.0%, P < 0.0001) and meat (-49.3%, P = 0.005) intake, fasting glycaemia (-9.2%, P = 0.012), and fasting insulin (-32.6%, P = 0.014), C-Reactive Protein (-34.0%, P = 0.005). They showed a significant increase in MAI (+213, P < 0.0001), physical activity (expressed in steps per day, +200.4%, P < 0.0001), fruit (+38.8, P < 0.0001), vegetables (29.3%, P < 0.0001), and dietary fiber (+38.6%, P = 0.04) intake. In contrast, the control group presented non-significant variations in measured parameters, for exception of cheese intake (+18.2%, P < 0.0001). The MFAP was found to promote uptake of the Mediterranean diet, and improve anthropometric, physical activity, dietary, and metabolic parameters in healthy subjects.

15-week long school-based nutritional education program to promote Italian primary schoolchildren's fruit and vegetable intake

A short-version (15-week long) of school-based nutrition education program called "Bring Fruit to School" to enhance primary schoolchildren's fruit and vegetable (F&V) intake was evaluated. We recruited 199 primary schoolchildren from 8 classes (grade 2-5). The primary end-point was an increase in the children's F&V intake. The intervention period lasted 15 weeks, and was divided into three phases: weeks 1-5, weeks 6-10 and weeks 11-15. The F&V intake of the schoolchildren was also monitored in a subsequent follow-up period (16th-32nd week). By week 15, 92 (46.2%, P < .001) schoolchildren increase fruit intake and 91 (45.7%, P < .001) increase vegetable intake. The F&V intake increased during the intervention period and was constant in follow-up. The BFtS program is an effective means to promote primary schoolchildren's F&V intake, and was implemented in Italy by the Food and Nutrition Service of Foggia's Local Health Authority. It could be extended to many other countries by local nutrition agencies, such as associations for nutrition.

PTPN2 but not PTPN22 is associated with Crohn's disease in a New Zealand population

Recent genome-wide association studies have provided evidence for the involvement of the genes PTPN2 and PTPN22 in the pathogenesis of Crohn's disease (CD). We investigated whether genetic variants in these genes were associated with CD in a New Zealand population. Single-nucleotide polymorphisms (SNPs) rs2542151 (PTPN2) and rs2476601 (PTPN22) were genotyped in 315 CD cases and 481 controls. In this sample, we were able to confirm an association between CD and PTPN2 (genotypic P = 0.019 and allelic P = 0.011), and phenotypic analysis showed an association of this SNP with late age at first diagnosis, inflammatory and penetrating CD behaviour, requirement of bowel resection and being a smoker at diagnosis. There was no evidence for an association with PTPN22.

Nutrigenomics in the whole-genome scanning era: Crohn's disease as example

Nutrigenomics has the potential to tailor diets to optimize health, based on knowledge of key genetic polymorphisms. Identification of candidate genes is often based on a priori knowledge of disease processes. However, genome-wide association methods are not only validating previously identified genes and polymorphisms, but also revealing new gene-disease associations not anticipated from prior knowledge. In Crohn's disease (CD), such studies not only confirm the importance of caspase-activated recruitment domain 15 and major histocompatibility complex II molecules, but also reveal strong associations with the proinflammatory cytokine interleukin-23 receptor and autophagy-related 16-like gene. Genes identified to date in CD can be linked into two interrelated pathways: receptor-mediated cytokine induction or autophagocytosis. New genomic technologies need to be matched with innovative methodologies to characterize the likely impact of foods and to take the field to another dimension of value for human diet development and optimized health.

Gender-stratified analysis of DLG5 R30Q in 4707 patients with Crohn disease and 4973 controls from 12 Caucasian cohorts

BACKGROUND

DLG5 p.R30Q has been reported to be associated with Crohn disease (CD), but this association has not been replicated in most studies. A recent analysis of gender-stratified data from two case-control studies and two population cohorts found an association of DLG5 30Q with increased risk of CD in men but not in women and found differences between 30Q population frequencies for males and females. Male-female differences in population allele frequencies and male-specific risk could explain the difficulty in replicating the association with CD.

METHODS

DLG5 R30Q genotype data were collected for patients with CD and controls from 11 studies that did not include gender-stratified allele counts in their published reports and tested for male-female frequency differences in controls and for case-control frequency differences in men and in women.

RESULTS

The data showed no male-female allele frequency differences in controls. An exact conditional test gave marginal evidence that 30Q is associated with decreased risk of CD in women (p = 0.049, OR = 0.87, 95% CI 0.77 to 1.00). There was also a trend towards reduced 30Q frequencies in male patients with CD compared with male controls, but this was not significant at the 0.05 level (p = 0.058, OR = 0.87, 95% CI 0.74 to 1.01). When data from this study were combined with previously published, gender-stratified data, the 30Q allele was found to be associated with decreased risk of CD in women (p = 0.010, OR = 0.86, 95% CI 0.76 to 0.97), but not in men.

CONCLUSION

DLG5 30Q is associated with a small reduction in risk of CD in women.

Mechanisms by which resistant starches and non-starch polysaccharide sources affect the metabolism and disposition of the food carcinogen, 2-amino-3-methylimidazo[4,5-f]quinoline

Although both non-starch polysaccharides (NSP) and resistant starches (RS) are included in current definitions of dietary fibre, our previous work has suggested fundamental differences in the way in which these two classes of material affect the disposition and absorption of a dietary carcinogen. The present studies explore whether different effects on carcinogen metabolism could play a role in the contrasting patterns seen previously. Groups of female Wistar rats were pre-fed for 4 weeks one of five types of defined diet (AIN-76). The control diet contained 35% maize starch and no dietary fibre. The RS-containing diets had all the maize starch substituted with either Hi-maize or potato starch. In the NSP-containing diets, 10% of the maize starch was substituted with dietary fibre in the form of either lignified plant cell walls (wheat straw) or soluble dietary fibre (apple pectin). Pre-fed rats were gavaged with the food carcinogen, [2-14C] 2-amino-3-methylimidazo[4,5-f]quinoline (IQ), and plasma and urinary metabolites characterized using HPLC at various time intervals after administration. After 4 h gavage, plasma from rats on both RS-containing diets contained significantly higher levels of intact IQ and lower levels of the major metabolites, IQ-5-O-glucuronide and IQ-5-sulfate, as compared with plasma from the negative control group at this time. In contrast, plasma from animals on the NSP-containing wheat straw diet (and to a lesser extent the apple pectin diet) showed significantly lower levels of intact IQ, and significantly higher levels of the two major metabolites, as compared with those from the control rats. These different metabolite profiles were also reflected in different urinary excretion profiles. Urine from rats pre-fed RS-containing diets revealed significantly slower metabolite excretion as compared with urine from rats that had been given the NSP-containing diets. Western blotting methodologies also profiled differences between the effects of these two types of dietary fibre in the expression of xenobiotic metabolizing enzymes. We conclude that changes in activity and expression of xenobiotic metabolising enzymes could play a role in the contrasting effects of these two types of dietary fibre on carcinogen uptake and disposition.

The 10 basic requirements for a scientific paper reporting antioxidant, antimutagenic or anticarcinogenic potential of test substances in in vitro experiments and animal studies in vivo

There is increasing evidence that chemicals/test substances cannot only have adverse effects, but that there are many substances that can (also) have a beneficial effect on health. As this journal regularly publishes papers in this area and has every intention in continuing to do so in the near future, it has become essential that studies reported in this journal reflect an adequate level of scientific scrutiny. Therefore a set of essential characteristics of studies has been defined. These basic requirements are default properties rather than non-negotiables: deviations are possible and useful, provided they can be justified on scientific grounds. The 10 basic requirements for a scientific paper reporting antioxidant, antimutagenic or anticarcinogenic potential of test substances in in vitro experiments and animal studies in vivo concern the following areas: (1) Hypothesis-driven study design; (2) The nature of the test substance; (3) Valid and invalid test systems; (4) The selection of dose levels and gender; (5) Reversal of the effects induced by oxidants, carcinogens and mutagens; (6) Route of administration; (7) Number and validity of test variables; (8) Repeatability and reproducibility; (9) Statistics; and (10) Quality Assurance.

Changing concepts of dietary fiber: implications for carcinogenesis

The dietary fiber (DF) hypothesis suggested that DF, as plant cell walls, protected against colorectal cancer. The implicit assumption in much historic literature was that the readily analyzed and quantified nonstarch polysaccharide (NSP) component was critical in cancer protection. However, the presence of polymeric phenolic components such as lignin or suberin has profound effects on the physicochemical properties of the cell walls and largely determines their physiological properties in humans. In certain groups of food plants, degradation of cell walls that contain neither lignin nor suberin releases ferulic acid and other hydroxycinnamic acids. These acids have antioxidant, antimutagenic, and other anticancer effects, including modulation of gene expression and immune response. Reexamination of literature on cancer protection suggests that plant cell walls containing significant amounts of phenolic components may be the most likely to protect against cancer. In the last 30 years, the definition of DF has been incrementally expanded to incorporate NSP extracted from plant cell walls and from sources other than plant cell walls, then resistant starch, and most recently nondigestible oligosaccharides. On the early definitions, increased consumption of DF could only be achieved by increasing the intake of whole grains, brans, or other food plant material that would increase the intake of plant cell walls containing significant amounts of phenolic components. However, the new definitions make it possible to increase "dietary fiber" without consuming any such materials. We suggest that this could have negative connotations for cancer risk in human populations.

Evidence for epidermal growth factor receptor-enhanced chemosensitivity in combinations of cisplatin and the new irreversible tyrosine kinase inhibitor CI-1033

Irreversible inhibitors of the epidermal growth factor receptor (EGFR) are showing promise in clinical trials. This report is the first to show that inhibition of the EGFR tyrosine kinase by an irreversible binder synergizes with cisplatin, at least in EGFR-overexpressing tissue culture cell lines in vitro. Unlike previous synergies demonstrated between ErbB2 blockade and DNA-damaging drugs, the synergy between the irreversible EGFR inhibitor and cisplatin does not appear to involve the repair of DNA-cisplatin adducts. Given the current clinical data, this combination may be of more than theoretical interest.

Vitamins/minerals and genomic stability in humans

Recommended dietary allowances (RDAs) of micronutrients have been traditionally derived as those levels necessary to prevent symptoms of deficiency diseases. There is increasing evidence that higher levels of many such micronutrients may be necessary for various DNA maintenance reactions, and that the current RDAs for some micronutrients may be inadequate to protect against genomic instability. Supplementation of a normal diet, with either vitamins and/or minerals or with isolated plant polyphenols, is becoming increasingly common in most Western populations. However, there is no clear agreement as to how much supplementation should occur, if at all, and genotypic differences are not accounted for. The 14 mini-reviews in this special issue summarise the role of specific micronutrients in various aspects of DNA maintenance: DNA synthesis, DNA repair, DNA methylation, gene mutation, chromosome breakage, chromosome segregation, gene expression, oxidative stress, necrosis and apoptosis. Evidence has been collated from mammalian and human experiments, both using in vitro cultures and in vivo approaches. Authors were asked to critically assess the strength of evidence as to whether the micronutrient can affect genomic stability in humans at realistic intake levels, and to estimate optimal dietary ranges where possible. Information on further research necessary is also documented. These reviews are an essential step towards a definition of RDAs designed to maintain genomic stability.

Role of plant polyphenols in genomic stability

Polyphenols are a large and diverse class of compounds, many of which occur naturally in a range of food plants. The flavonoids are the largest and best-studied group of these. A range of plant polyphenols are either being actively developed or currently sold as dietary supplements and/or herbal remedies. Although, these compounds play no known role in nutrition (non-nutrients), many of them have properties including antioxidant, anti-mutagenic, anti-oestrogenic, anti-carcinogenic and anti-inflammatory effects that might potentially be beneficial in preventing disease and protecting the stability of the genome. However not all polyphenols and not all actions of individual polyphenols are necessarily beneficial. Some have mutagenic and/or pro-oxidant effects, as well as interfering with essential biochemical pathways including topoisomerase enzyme activities, prostanoid biosynthesis and signal transduction. There is a very large amount of in vitro data available, but far fewer animal studies, and these are not necessarily predictive of human effects because of differences in bacterial and hepatic metabolism of polyphenols between species. Epidemiological studies suggest that high green tea consumption in the Japanese population and moderate red wine consumption in the French population may be beneficial for heart disease and cancer, and these effects may relate to specific polyphenols. A small number of adequately controlled human intervention studies suggest that some, but not all polyphenol extracts or high polyphenol diets may lead to transitory changes in the antioxidative capacity of plasma in humans. However, none of these studies have adequately considered long-term effects on DNA or the chromosome and unequivocally associated these with polyphenol uptake. Furthermore, clinical trials have required intravenously administered polyphenols at concentrations around 1400mg/m(2) before effects are seen. These plasma concentrations are unlikely to be achieved using the dietary supplements currently available. More focused human studies are necessary before recommending specific polyphenolic supplements at specific doses in the human population.

Comparative effects of three resistant starch preparations on transit time and short-chain fatty acid production in rats

A high-fiber diet may protect against colon cancer because of the butyrate generated in the colon by bacterial fermentation of nonstarch polysaccharides. Butryrate can reverse neoplastic changes, at least in vitro, and resistant starch (RS) represents a source of butyrate in vivo. We examined the effects of replacing normal maize starch in the diet of rats with three preparations of RS on the amounts of starch, butyrate, and other short-chain fatty acids in the cecum. We examined the effects on fecal bulking and transit time, which have been suggested to protect against colon cancer. The RS preparations that we tested were potato starch, high-amylose maize starch, and an alpha-amylase-treated high-amylose maize starch. All had major effects on fecal weight and on the weight of the cecum but only slightly shortened transit times. All increased the amount of starch reaching the cecum and increased short-chain fatty acid production in the cecum; potato starch had the greatest effect and high-amylose maize starch the least. Potato starch, unlike high-amylose maize starch, enhanced the proportion of butyrate. Thus there were marked differences among sources of RS, even though these were all classified as RS2. The significance for colon cancer is discussed.

Contrasting effects of acute and chronic dietary exposure to 2-amino-3-methyl-imidazo[4,5-f]quinoline (IQ) on xenobiotic metabolising enzymes in the male Fischer 344 rat: implications for chemoprevention studies

BACKGROUND

2-Amino-3-methyl-imidazo[4,5-f]quinoline (IQ) is a mutagen produced in cooked food. It is commonly present in the human diet and often used as a (pro)carcinogen for chemoprevention studies. Many foodstuffs act as chemopreventers by altering xenobiotic metabolising enzyme expression in favour of detoxication over bioactivation pathways. However, IQ itself can also affect enzyme expression, which may be a confounding factor in chemoprevention studies.

AIM OF STUDY

Chronic low dose IQ exposure is intuitively closest to the human dietary situation. The aim was to investigate the effects of chronic dietary exposure to IQ on the expression of enzymes involved in the bioactivation and detoxification of xenobiotics and to compare this with acute exposure, often used in chemoprevention studies.

METHODS

Male Fischer rats received IQ (300 ppm) in the diet (AIN-76) for 52 weeks or were given IQ (20 mg.kg-1) orally for 3 days. Animals were killed, livers removed and subcellular fractions prepared. A range of enzymes was selected to allow investigation of several cellular mechanisms. Enzyme expression and activity were determined by Western blotting and the use of selective probe substrates as appropriate.

RESULTS

Chronic exposure to IQ led to an increase in phase II detoxifying enzymes. Both the activity and expression of glutathione S-transferase (GST-A1/2) were increased, as were NADPH: Quinone oxidoreductase (NQO), UDP-glucuronosyl transferase (UGT) and beta-glucuronidase activities. There were no statistically significant changes in the potential for bioactivation by three cytochrome P450s. In contrast, acute IQ exposure significantly increased the expression and activity of some cytochrome P450 (CYP1A1 and CYP1A2), UGT and beta-glucuronidase, but significantly decreased glutathione S-transferase expression and activity. There was a non-significant decrease in NQO but no change in CYP3A2 and CYP2E1 activities.

CONCLUSIONS

The changes after acute exposure suggest an interaction through the Ah receptor and xenobiotic response element, modified by the glucocorticoid response element. In contrast, the pattern of effects after chronic exposure suggests activation of the antioxidant response element (ARE). Although the acute model is more practically convenient for short-term chemoprevention screening, the data suggest that an entirely new mechanism is being invoked that completely masks effects of the ARE that occur during chronic exposure. There is a danger that chemopreventive strategies developed using acute models may be misleading, since the mechanism is unlikely to occur during human dietary exposures.

Flow cytometric enumeration of micronucleated reticulocytes: high transferability among 14 laboratories

This laboratory previously described a single-laser flow cytometric method, which effectively resolves micronucleated erythrocyte populations in rodent peripheral blood samples. Even so, the rarity and variable size of micronuclei make it difficult to configure instrument settings consistently and define analysis regions rationally to enumerate the cell populations of interest. Murine erythrocytes from animals infected with the malaria parasite Plasmodium berghei contain a high prevalence of erythrocytes with a uniform DNA content. This biological model for micronucleated erythrocytes offers a means by which the micronucleus analysis regions can be rationally defined, and a means for controlling interexperimental variation. The experiments described herein were performed to extend these studies by testing whether malaria-infected erythrocytes could also be used to enhance the transferability of the method, as well as control intra- and interlaboratory variation. For these studies, blood samples from mice infected with malaria, or treated with vehicle or the clastogen methyl methanesulfonate, were fixed and shipped to collaborating laboratories for analysis. After configuring instrumentation parameters and guiding the position of analysis regions with the malaria-infected blood samples, micronucleated reticulocyte frequencies were measured (20,000 reticulocytes per sample). To evaluate both intra- and interlaboratory variation, five replicates were analyzed per day, and these analyses were repeated on up to five separate days. The data of 14 laboratories presented herein indicate that transferability of this flow cytometric technique is high when instrumentation is guided by the biological standard Plasmodium berghei.

HUman MicroNucleus project: international database comparison for results with the cytokinesis-block micronucleus assay in human lymphocytes: I. Effect of laboratory protocol, scoring criteria, and host factors on the frequency of micronuclei

Micronucleus (MN) expression in peripheral blood lymphocytes is well established as a standard method for monitoring chromosome damage in human populations. The first results of an analysis of pooled data from laboratories using the cytokinesis-block micronucleus (CBMN) assay and participating in the HUMN (HUman MicroNucleus project) international collaborative study are presented. The effects of laboratory protocol, scoring criteria, and host factors on baseline micronucleated binucleate cell (MNC) frequency are evaluated, and a reference range of "normal" values against which future studies may be compared is provided. Primary data from historical records were submitted by 25 laboratories distributed in 16 countries. This resulted in a database of nearly 7000 subjects. Potentially significant differences were present in the methods used by participating laboratories, such as in the type of culture medium, the concentration of cytochalasin-B, the percentage of fetal calf serum, and in the culture method. Differences in criteria for scoring micronuclei were also evident. The overall median MNC frequency in nonexposed (i.e., normal) subjects was 6.5 per thousand and the interquartile range was between 3 and 12 per thousand. An increase in MNC frequency with age was evident in all but two laboratories. The effect of gender, although not so evident in all databases, was also present, with females having a 19% higher level of MNC frequency (95% confidence interval: 14-24%). Statistical analyses were performed using random-effects models for correlated data. Our best model, which included exposure to genotoxic factors, host factors, methods, and scoring criteria, explained 75% of the total variance, with the largest contribution attributable to laboratory methods.

Antimutagenic effects of wheat bran diet through modification of xenobiotic metabolising enzymes

Diets containing wheat bran (WB) protect against cancers of the colon or breast in rats, and may be beneficial in humans. In a previous study of rats treated with the carcinogen 2-amino-3-methylimidazo[4,5-f]quinoline (IQ), inclusion of 10% wheat bran in the diet led to an apparent reduction in IQ metabolites but not of intact IQ in plasma. In the present study, male Wistar rats were fed diets containing 0, 10 or 20% wheat bran, and effects on xenobiotic metabolising enzymes compared. Wheat bran-supplementation showed differential effects on phase I enzymes, significantly increasing the activity of hepatic cytochrome P450 isozyme CYP3A2, but slightly reducing the activity of CYP1A1/2. The activities of both hepatic phase II detoxification enzymes glutathione-S-transferase and glucuronosyl transferase were also reduced. Western blotting revealed similar effects on expression of the proteins. Interestingly, the expression of xenobiotic metabolising enzymes (XME) in the colon appeared to be modulated independently of hepatic XME. Although the wheat bran-supplemented diet still led to an increased expression of CYP3A, it now slightly increased CYP1A in the colon. However, 20% wheat bran significantly increased the expression of both glutathione transferase isozymes, GST A1 & A2, in the colon. Natures Gold (NG) is a commercial wheat bran derivative which is lower than wheat bran in dietary fibre, but enriched in vitamins, minerals and various phytochemicals. Dietary supplementation with 20% Natures Gold led to similar trends as seen in wheat bran-fed rats, but more potent effects in both hepatic and colonic enzymes. The significance of these changes for activation of carcinogens to mutagenic metabolites was investigated using the Salmonella/mammalian microsome mutagenicity test. The activation of IQ and benzo[a]pyrene, but not cyclophosphamide, to a mutagen by hepatic S9 from wheat bran-fed or Natures Gold-fed rats was significantly reduced compared with S9 from animals on a diet lacking wheat bran. We suggest that modulation of xenobiotic metabolising enzymes may be an important component of cancer protection by wheat bran, and this effect may relate to micronutrients or cancer-protective non-nutrient phytochemicals rather more than to dietary fibre.

The mutagenic spectrum of acridine-linked aniline nitrogen mustards in AS52 cells: implications of DNA targeting with high selectivity for adenine or guanine bases

The mutational spectra generated in AS52 cells at the gpt gene locus by aniline mustards were studied by the isolation of resistant clones and sequencing of the altered gene. A set of four aniline mustards (both mono- and bifunctional) linked to a DNA-affinic 9-aminoacridine (9-AA) carrier was used, together with the untargeted mustards chlorambucil (CHL) and its half-mustard, and the DNA binding carrier, 9-AA. Both 9-AA and CHL were weak cytotoxins, with the DNA-targeted mustards being markedly (10-40-fold) more dose potent, and the bifunctional ones somewhat more toxic than the monofunctional ones. 9-AA produced a different spectrum of mutations to the spontaneous background, with more minor addition events and less base pair substitutions, and showing for the first time that frameshift events so characteristic of 9-AA in bacteria or bacteriophage also occur in mammalian cells. The mutational spectra of the DNA-targeted mustards were quite different both from this and from the lesions caused by the untargeted mustards, which cause largely transition mutations at AT sites (despite a clear preference for formation of N(7)-guanine adducts). There were very few transition mutations, suggesting that the initial O(6)-alkylguanine/O(4)-alkylthymine lesions considered to give rise to these are relatively rare. There was also a lower incidence of complete deletions, usually attributed to DNA cross-links. For the short chain length targeted mustards, which form initial stable adducts largely (95%) at guanine N(7) sites, base pair substitution mutations, predominantly transversions, involved AT and GC base pairs equally. In contrast, the longer chain length targeted mustards, which form >90% of initial adducts at adenine N(1) sites, generated also formed transversion mutations, but these overwhelmingly (24/27) involved AT base pairs.

Role of DNA minor groove alkylation and DNA cross-linking in the cytotoxicity of polybenzamide mustards

Interstrand DNA cross-links have been considered essential to the activity of current clinical DNA-alkylating antitumour drugs, which generally alkylate in the major groove. However, the relationship between cross-linking adducts located in the minor groove of DNA with cytotoxicity and antitumour activity has not been extensively investigated. Previous studies have shown that cross-linking ability is not correlated with cytotoxicity in a novel series of polybenzamide-linked nitrogen mustard compounds which alkylate DNA at adenines in the minor groove. In the present study the nature of these cross-linking adducts was explored for a related pair of compounds which are both highly effective cross-linkers but which differ in antitumour potential. Both of these drugs effectively interact with adenines in the minor groove, although their sequence specificity differs. However, the cross-linking event was not inhibited by pre-treatment with Hoechst 33258, although this pre-treatment effectively prevented adenine alkylation. The primary cross-links detected may thus represent guanine N7 alkylations in the major groove. Whether minor groove cross-linking adducts can be formed is uncertain, since the effect of background guanine N7 alkylation may complicate analysis. The cytotoxicity of the polybenzamides may therefore be related to other factors such as their interaction with cellular repair systems.

Transcriptional blockages in a cell-free system by sequence-selective DNA alkylating agents

There is considerable interest in DNA sequence-selective DNA-binding drugs as potential inhibitors of gene expression. Five compounds with distinctly different base pair specificities were compared in their effects on the formation and elongation of the transcription complex from the lac UV5 promoter in a cell-free system. All were tested at drug levels which killed 90% of cells in a clonogenic survival assay. Cisplatin, a selective alkylator at purine residues, inhibited transcription, decreasing the full-length transcript, and causing blockage at a number of GG or AG sequences, making it probable that intrastrand crosslinks are the blocking lesions. A cyclopropylindoline known to be an A-specific alkylator also inhibited transcription, with blocks at adenines. The aniline mustard chlorambucil, that targets primarily G but also A sequences, was also effective in blocking the formation of full-length transcripts. It produced transcription blocks either at, or one base prior to, AA or GG sequences, suggesting that intrastrand crosslinks could again be involved. The non-alkylating DNA minor groove binder Hoechst 33342 (a bisbenzimidazole) blocked formation of the full-length transcript, but without creating specific blockage sites. A bisbenzimidazole-linked aniline mustard analogue was a more effective transcription inhibitor than either chlorambucil or Hoechst 33342, with different blockage sites occurring immediately as compared with 2 h after incubation. The blockages were either immediately prior to AA or GG residues, or four to five base pairs prior to such sites, a pattern not predicted from in vitro DNA-binding studies. Minor groove DNA-binding ligands are of particular interest as inhibitors of gene expression, since they have the potential ability to bind selectively to long sequences of DNA. The results suggest that the bisbenzimidazole-linked mustard does cause alkylation and transcription blockage at novel DNA sites. in addition to sites characteristic of untargeted mustards.

Mutations induced by some DNA minor groove binding alkylators in AS52 Chinese hamster cells

Nitrogen mustards are commonly used in cancer chemotherapy. They interact with DNA at electronegative sites, primarily forming N7 guanine mono-adducts and interstrand cross-links. Targeting nitrogen mustards to DNA by attachment of a DNA minor groove binding carrier such as the bisbenzimidazoles Hoechst 33258 (pibenzimol) or Hoechst 33342 (HOE) makes it possible to direct DNA alkylation to more specific stretches of DNA. We have performed a detailed molecular analysis of 6-thioguanine resistant clones arising in Chinese hamster AS52 cells after treatment with HOE, in comparison with a mono- and bifunctional pair of bisbenzimidazole-targeted nitrogen mustards (MGBs). HOE showed no significant ability to induce 6-thioguanine resistant mutants, possibly because drug-treated cells are highly susceptible to apoptosis within very short times. Neither of the MGBs caused the rapid cell death seen with the bisbenzimidazole. However, both MGBs were weaker mutagens than previously found for undirected mustards in the same system, an effect that we suggest could relate to greater structure-directed binding to less mutable DNA sites in the minor groove. Additionally, the nature of some of the mutants suggested there may be a small component of topo I and/or II-mediated events in the mutagenicity of the MGBs. Both MGBs showed high activity in causing deletion mutations, which may be due to errors in attempted repair of the complex lesions formed by minor groove targeted alkylators.

Heterocyclic amine content of cooked meat and risk of prostate cancer

BACKGROUND

Some epidemiologic studies have described positive associations between prostate cancer risk and meat consumption, but underlying mechanisms have not been identified. Heterocyclic amines are mutagens formed during the cooking of meat. Well-done meat has been associated with increased risks of colorectal and breast cancers in humans. This study examined associations between prostate cancer risk and 1) estimated daily intake of heterocyclic amines from cooked meat and 2) level of cooked-meat doneness.

METHODS

A population-based, case-control study involving 317 case patients with prostate cancer and 480 age-matched control subjects was carried out in Auckland, New Zealand. Levels of meat doneness and daily intake of heterocyclic amines were determined from self-reported dietary data and experimentally measured heterocyclic amine levels in locally sourced meat samples cooked under controlled conditions to varying degrees of doneness.

RESULTS

The heterocyclic amines found in the highest concentrations in meat samples were 2-amino-1,6-dimethylfuro[3,2-e]imidazo[4,5-b]pyridine (IFP) and 2-amino-1-methyl-6-phenylimidazo [4,5-b]pyridine (PhIP) from well-done chicken and pork and very well-done beefsteak. Meat doneness was weakly and inconsistently associated with prostate cancer risk for individual types of meat, but increased risk was observed for well-done beefsteak (relative risk = 1.68; 95% confidence interval = 1.02-2.77; two-sided P for trend =.03). A weak positive gradient of increased risk was associated with estimated daily exposure to IFP but not with the other major heterocyclic amines.

CONCLUSIONS

Meat doneness and estimated intake of heterocyclic amines from cooked meat were not clearly associated with prostate cancer risk.

Studies on the mechanism of cancer protection by wheat bran: effects on the absorption, metabolism and excretion of the food carcinogen 2-amino-3-methylimidazo[4,5-f]quinoline (IQ)

We examined ways in which dietary supplements of wheat bran may protect against colon cancer. The effects of supplementing the diet of female Wistar rats with 10% wheat bran on the disposition and metabolism of the dietary carcinogen 2-amino-3-methylimidazo[4,5-f]quinoline (IQ) labelled with (14)C was determined. Our data show that the wheat bran had a major effect on both the distribution and metabolism of IQ. At a low dose of IQ (1 mg/kg), we unexpectedly found that up to 2 h after gavage there were higher concentrations of radioactivity in the plasma of rats fed wheat bran compared with the controls, but there were lower concentrations of radioactivity after 2 h. At a high dose of IQ (50 mg/kg), there were always lower concentrations of radioactivity in the plasma of rats fed wheat bran compared with the control rats. One of the most marked effects of wheat bran was apparently to significantly retard the metabolism of IQ in the plasma when this was fed at either dose. There were also differences between the rats fed wheat bran and the control in the concentrations and types of IQ metabolites in the urine.

Dietary fibres may protect or enhance carcinogenesis

Dietary fibre (DF) is widely considered to protect against cancer, especially colorectal cancer. However, a large prospective epidemiological study has shown no apparent effect of DF intake on the development of colorectal cancer. We suggest that this may be because the term DF represents a wide range of materials, some able to protect, but some able to enhance carcinogenesis. This is consistent with data from animal carcinogenesis experiments. Most of the DF in western diets is in the form of plant cell walls, but these vary in their composition and it is unlikely that all types are protective. The few data available indicate that plant cell walls containing suberin or lignin may be the most protective, although they are present in only small amounts in food plants. DFs are also added to foods. These include components obtained from plant cell walls, such as pectins, as well as soluble DFs from other sources. In general, animal carcinogenesis experiments indicate that soluble DFs do not protect and some may enhance carcinogenesis. Few human intervention studies have been done on DF or sources of DF, with the exception of wheat bran, a good source of DF, which has been shown to protect. Possible mechanisms whereby DF may enhance carcinogenesis are discussed. In addition to DFs, resistant starches and non-digestible oligosaccharides are added to foods; these, like DF, escape digestion in the small intestine. However, so far only a few animal carcinogenesis experiments have been reported using these materials, and no human intervention studies. We believe caution should be exercised in the addition of such materials to food.

Prospects for cancer prevention

As in many other countries, the New Zealand Cancer Society produces guidelines for cancer prevention. These recommend avoiding asbestos, smoking, sunlight, alcohol, fatty food and obesity. Women are advised to have a regular cervical smear test. Additional 'probably helpful' suggestions include eating plenty of fresh fruit and vegetables and dietary fibre. However, considerable data from animal studies and more slowly accumulating data from human intervention studies suggest additional and more specific advice may be appropriate. Fruit and vegetable servings should total a minimum of five each day. Some specific fruits and vegetables (e.g., tomato, broccoli, onions) may have particular benefits against individual cancer types. Positive human evidence on potential benefits of increasing dietary fibre comes from studies where wheat bran was added to the diet. This is not a dietary fibre per se, but merely a good fibre source. Indeed, our own studies suggest that it could be various phytochemicals in the bran, rather than dietary fibre, which is beneficial. An increase either in whole wheat or wheat bran, rather than fibre, would be a sounder recommendation. Although there is some evidence that multivitamin supplementation can protect against cancer, this may be only in the special situation where the population is already significantly vitamin-deficient. For example, a combination of beta-carotene, vitamin E and selenium significantly reduced cancer mortality in a Chinese population, whereas lung cancer risks (in already high risk groups) were increased in Finnish and American trials with high dose beta-carotene. Various other chemopreventive drugs are being actively developed and at various stages in clinical trials. The enhanced cancer incidence in the beta-carotene trial illustrates the potential benefit of utilising surrogate endpoints of malignant disease rather than incident cancer as a trial endpoint.

Natural and man-made mutagens and carcinogens in the human diet

Around 40% of human cancers may relate to dietary factors, including both exogenous and endogenous mutagens. Of exogenous factors, alcohol, certain metals and certain pesticides (both naturally produced or manufactured by the chemical industry), N-nitroso compounds, heterocyclic amines and polycyclic aromatic hydrocarbons are all probable human carcinogens. Despite current negative publicity, genetic engineering appears to be a more precise process and no more likely to lead to cancer risks than conventional breeding processes. Many traditional assessments of cancer hazard from endogenous or exogenous chemicals ignore the presence of modifying factors in the human diet. For example, dietary fat and dietary fibre probably either enhance or protect against cancer, depending upon the exact amounts and chemical nature of the fat fibre. Considerable numbers of other types of antimutagen/anticarcinogens have been identified, with varying modes of action. Additionally, there is an interaction of dietary factors with genetics. Epidemiology will always be important in assessing relative risks, but it is essential to continue developing more sensitive biomonitoring methodologies. It would be desirable to compare precise measures of individual exposure to dietary carcinogens with levels of oxidative damage and evidence of genotoxic effects in a given tissue. Such experimental approaches might be expected to lead a better understanding of the interplay between different dietary factors and also between diet, hereditary and the environment.

Dietary fibres may protect or enhance carcinogenesis

Dietary fibre (DF) is widely considered to protect against cancer, especially colorectal cancer. However, a large prospective epidemiological study has shown no apparent effect of DF intake on the development of colorectal cancer. We suggest that this may be because the term DF represents a wide range of materials, some able to protect, but some able to enhance carcinogenesis. This is consistent with data from animal carcinogenesis experiments. Most of the DF in western diets is in the form of plant cell walls, but these vary in their composition and it is unlikely that all types are protective. The few data available indicate that plant cell walls containing suberin or lignin may be the most protective, although they are present in only small amounts in food plants. DFs are also added to foods. These include components obtained from plant cell walls, such as pectins, as well as soluble DFs from other sources. In general, animal carcinogenesis experiments indicate that soluble DFs do not protect and some may enhance carcinogenesis. Few human intervention studies have been done on DF or sources of DF, with the exception of wheat bran, a good source of DF, which has been shown to protect. Possible mechanisms whereby DF may enhance carcinogenesis are discussed. In addition to DFs, resistant starches and non-digestible oligosaccharides are added to foods; these, like DF, escape digestion in the small intestine. However, so far only a few animal carcinogenesis experiments have been reported using these materials, and no human intervention studies. We believe caution should be exercised in the addition of such materials to food.

Antimutagens in food plants eaten by Polynesians: micronutrients, phytochemicals and protection against bacterial mutagenicity of the heterocyclic amine 2-amino-3-methylimidazo[4,5-f]quinoline

We have previously suggested that differences in cancer incidence between Polynesians (including Maoris and people from several Pacific islands) and Europeans in New Zealand may at least partially relate to differences in the species of food plants (fruits, vegetables and cereals) preferentially eaten by these groups. Twenty-five food plants that are typically eaten in different amounts by these two population groups were selected for detailed study. Antimutagenic properties of three extracts from each of the selected plants were investigated using a preincubation mutagenicity assay with Salmonella typhimurium strain TA1538 against the mutagenicity of the heterocyclic amine 2-amino-3-methylimidazo[4,5-f]quinoline (IQ). The data revealed strong antimutagenic properties in several of the food plants commonly eaten by Polynesians, especially rice, watercress, pawpaw, taro leaves, green banana and mango. Using the New Zealand food database, a number of nutrients and micronutrients with antimutagenic and anticarcinogenic potential were identified from the selected food plants. Some of these were tested for antimutagenic potential in parallel experiments to those done with the food plant extracts. Although some of these micronutrients are antimutagens against IQ, their concentrations in the food plants failed to explain the protection against mutagenicity found in the experiments with extracts of the food plants. Thus, other types of chemical, not identified in the database, must be leading to antimutagenesis. Possible active molecules include chlorophylls, carotenoids, flavonoids and coumarins, many of which are also known to be anticarcinogens. If human cancer data are to be interpreted in terms of cancer protection, these components need urgently to be quantified in food plants in the New Zealand diet, especially in those food plants eaten in large amounts by Polynesians.

Polybenzamide mustards: structure-activity relationships for DNA sequence-specific alkylation

A series of cytotoxic polybenzamide mustards targeted to the minor groove of DNA were used to define structure-activity relationships for sequence-specific DNA alkylation. Compounds with an annular structure closely matched to the minor groove of DNA, and with concave-facing, potentially H-bonding NH groups, had a strong preference for alkylating adenines in sequences possessing four or more consecutive adenines. Two compounds whose annular structure matched that of the minor groove better when at least one carboxamide NH group faced outwards showed a high specificity for the consensus sequence (A/T)A(G/C) (A/T)N. Several compounds also alkylated specific guanines, presumably at the N3 position. Modelling studies suggest the most important contribution to sequence-specific alkylation is the H-bonds formed between these compounds and DNA, with factors such as the degree and positioning of cationic charge being less influential.

Protection against cancer by wheat bran: role of dietary fibre and phytochemicals

Human intervention and animal studies have shown that supplementing the diet with wheat bran can protect against the development of a range of cancers, especially those of the colon and breast. Wheat bran is a rich source of dietary fibres (plant cell walls) that have structures and compositions which indicate that they may protect against cancer. Nevertheless, dietary fibre makes up less than half of wheat bran. Other nutrients and phytochemicals are present in wheat bran, some of which may also protect against cancer. These include phytic acid and various phenolic components such as phenolic acids, lignans and flavonoids. A major goal of future research on wheat bran should be to determine the relative roles in cancer prevention of the different components in wheat bran.

Binding of polybenzamides to DNA: studies by DNase I and chlorambucil interference footprinting and comparison with Hoechst 33258

The DNA sequence-specific binding ability of polybenzamide minor groove binding ligands was investigated. These ligands were compared with the known minor groove binder Hoechst 33258, using both DNase I footprinting and chlorambucil interference footprinting. The monocationic derivative showed some sequence specific binding to A/T-rich sequences, as shown by DNase I footprinting, but results for the biscationic polybenzamide were inconclusive. A general non-specific inhibition of cleavage at high drug concentrations was observed, suggesting these compounds had a low DNA binding affinity compared to Hoechst 33258. Using a complementary technique, chlorambucil interference footprinting, the biscationic derivative displayed a clear preference for sites containing at least three consecutive adenines and in contrast with the monocationic analogue, a lesser affinity for mixed A/T sequences.

Mutagenic properties of topoisomerase-targeted drugs

Topoisomerases maintain DNA structure by relieving torsional stress occurring in DNA during transcription, replication and cell division. Topoisomerases are of two main types, causing transient breaks in one (type I) or both (type II) and strands of DNA, and a number of clinical anticancer drugs are thought to act by inhibiting religation of these transient breaks. Topoisomerase II appears to have a close association with the SMC (stable maintenance of chromosomes) family of proteins involved in organisation of the chromatin in a series of loops on the proteinaceous chromosomal scaffold. Inhibition of topoisomerase II function can result in deletions of such loops, probably mediated by reciprocal exchange of topoisomerase subunits. Disruption of topoisomerase I and/or II function during DNA replication results in smaller DNA deletions and other mutations, probably arising from non-homologous recombination. Inhibition of topoisomerase II action during mitosis and meiosis can cause incomplete separation of chromatids and chromosomes, with the consequent production of genomic mutations. Topoisomerase-mediated mutagenicity is important because it can lead not only to drug resistance but also to drug-induced secondary cancers. Mutagenicity of topoisomerase-directed agents has been underestimated in the past, since these drugs are not usually capable of reacting covalently with DNA and usually have low mutagenicity in microbial assays.

Suberized plant cell walls suppress formation of heterocyclic amine-induced aberrant crypts in a rat model

Dietary fibre is believed to protect against a range of Western diseases, including colorectal cancer. Whole plant cell walls make up most of the dietary fibre in Western diets, but their role in disease protection has rarely been studied. At least in vitro, suberized plant cell walls possess novel properties that suggest they could have exceptional potential for cancer protection. Our aim was to test in a rat model the abilities of suberized cell walls from potato skins and commercial cork to decrease gastrointestinal transit time and to protect against the development of aberrant crypts, an early marker of colon cancer. Groups of six rats were fed a modified AIN-76 diet as the control diet and this diet supplemented with 5% dietary fibre from the following sources: commercial cork, commercial-cork cell walls and potato-skin cell walls. A diet supplemented with wheat bran was used as a positive control. The colon carcinogen IQ (2-amino-3-methylimidazo[4,5-f]quinoline) was administered for 3 weeks and after another 12 weeks the number of aberrant crypts determined. Transit times were determined after feeding the diets for 4 weeks. Compared with rats fed the control diet, rats fed diets supplemented with the suberized cell-wall preparations had decreased transit times and had significantly fewer aberrant crypts, with no aberrant crypt foci containing four or more crypts. The diets supplemented with suberized cell walls were more effective than thediet supplemented with wheat bran. We conclude that suberized and lignified cell walls, but particularly suberized, may play an important role in protection against Western diseases, including colorectal cancer. Failure to distinguish suberized and lignified plant cell walls from other sources of non-starch polysaccharides may provide a major limitation in current assessments of the role of dietary fibre in preventing colorectal cancer in humans.

Effect of selected antimutagens on the genotoxicity of antitumor agents

Cyclophosphamide (CP), bleomycin (BL), doxorubicin (DOX) and cisplatin (CISP) are potent antitumor drugs used worldwide against many forms of human cancer. As with most such agents, there can be physiological side-effects and the possible induction of mutations and other genotoxic effects in non-tumor cells. It is common for patients to ingest a host of food supplements to diminish the discomforting side-effects of therapy. Because these food supplements are often also rich in antimutagens that could also affect the biological efficacy of the antitumor drugs, we investigated if such antimutagenic agents were indeed antimutagenic to these antitumor drugs. Using the Salmonella/microsome bioassay, we tested CP, BL, DOX, and CP for mutagenicity in the presence and absence of the antimutagens ascorbic acid (AA), chlorophyllin (CHL) and (+)-catechin (CAT). AA was a very effective antimutagen against CISP and less effective against BL and DOX. It was not antimutagenic to CP. CHL was effective as an antimutagen against all four antitumor drugs, and CAT was a strong inhibitor of DOX mutagenicity, but had little effect on BL, CP and CISP. These data now provide a basis for future in vivo antitumor/antimutagen combination studies to determine if these antimutagens function in a manner to reduce genetic effects without having concomitant effects on intended antitumorogenicity of these therapeutic agents.

Comparative mutational spectra of the nitrogen mustard chlorambucil and its half-mustard analogue in Chinese hamster AS52 cells

Nitrogen mustards play an important role in current cancer chemotherapy. The most effective antitumour agents are those carrying two alkylating functions, probably through their ability to form interstrand cross-links in DNA. Such lesions appear to create more of a block in DNA replication and are more difficult to repair than are most monoadducts. Although there were early reports that monofunctional drugs were more mutagenic than the bifunctional drugs, this has not been formally proved using structurally related drugs in a mutagenicity assay capable of detecting a range of different events. We have studied both the mutagenic potency and spectrum of events caused by treatment with the clinical agent, chlorambucil, compared with its half-mustard analogue, in Chinese hamster ovary (CHO)-AS52 cells. Although both drugs caused comparable increases in mutation frequency at doses killing 90% of cells (from around 9x10-6 to around 9x10-5 mutant cells), the nature of events differed significantly between the drugs. By far the majority of mutations caused by the half-mustard were transversion mutations, and almost all of these could be interpreted in relation to the DNA adducts that are known to be formed. In contrast, the majority of chlorambucil-induced mutations were major deletions, and point mutations were only identified from a few clones. Parallel micronucleus assays verified that chlorambucil has a stronger ability to break chromosomes than the half-mustard. These two drugs are thought to form similar monoadducts, but only the full mustard can form interstrand cross-links. The data suggest that DNA cross-links, although only a minor fraction of the total lesions, dominate the mutagenic spectrum and lead to gross changes at the chromosome level that can not be readily associated with individual lesions produced by the drug.

Inhibitors of topoisomerase II enzymes: a unique group of environmental mutagens and carcinogens

Many inhibitors of topoisomerase II enzymes are potent mutagens, leading to major chromosomal deletions, illegitimate recombination and aneuploidy. There is increasing evidence that they are also human carcinogens. However, their lack of chemical reactivity means that they may give weak or negative results in commonly used mutagenicity tests, or may give data with characteristics quite distinct from chemicals that alkylate DNA. They do not form DNA adducts and assays such as 32P-postlabelling will not detect their presence in the body. They are generally not point mutagens and may fail to provide distinctive fingerprints in mutation spectra. These characteristics may be limiting a realistic evaluation of their role in human carcinogenesis using current methodologies.

Adsorption of a hydrophobic mutagen to cereal brans and cereal bran dietary fibres

The abilities of brans from the cereals barley, oats, maize, rice, and wheat to adsorb in vitro the hydrophobic, environmental mutagen 1,8-dinitropyrene (DNP) were investigated using a mutagenicity assay. These brans were obtained from known cultivars using defined milling conditions and were chemically characterised. The abilities of total and insoluble dietary fibre preparations obtained from these brans to adsorb DNP were also investigated. The predicted weight of each bran required to adsorb 50% of the added DNP was used to compare the adsorptive abilities of the different brans. The brans were ranked in the order (most effective to least effective): rice, wheat, maize, barley, and oats. The adsorptive abilities of the dietary fibre preparations were not significantly different from the bran from which they were prepared. However, if the dietary fibres (cell walls) were the only components adsorbing the DNP, we would have expected the dietary fibre preparations to have adsorbed more DNP than the equivalent unextracted bran. This suggests that other components, probably starch, also adsorb DNP in the unextracted brans. It is not known why brans from different cereal species differ in adsorptive ability but the lignified cell walls in wheat bran may be important in conferring good adsorptive properties to this bran. The possible relationship between adsorptive ability and ability of the bran from a particular species to protect against colorectal cancer is discussed.