The search for the causes of breast and colon cancer

A simple HPLC method for the determination of apigenin in mouse tissues

The flavone apigenin occurs in many leafy vegetables and fruits. It has been reported to have cancer chemopreventive efficacy in rodents. An HPLC method described previously for the determination of tricin, the dimethoxy cogener of apigenin, was modified and validated for measurement of apigenin in mouse tissues. Separation was carried out on a Hypersil-BDS C(18) column (4.6 x 250 mm) with an isocratic mobile phase of 55% methanol in 0.1 m ammonium acetate, pH 5.10, containing 0.27 mm disodium ethylenediamine tetraacetic acid. UV detection was at 336 nm, without interference from endogenous tissue compounds. The assay was linear in the range 25-400 ng/mL, 0.25-4 microg/mL and 2.5-40 microg/mL, with r(2) > 0.99 in all cases, for mouse plasma, liver and intestinal mucosa, respectively. Apigenin in mouse plasma, liver and intestinal mucosa was efficiently extracted with 0.1 m acetic acid in acetone. The assay recovery at low, medium and high concentrations was between 94.6 and 131.7% for all biomatrices, with a relative standard deviation of <10%. The lower limit of quantification for plasma was 25 ng/mL with a relative standard deviation of <15%. The method was used to measure the steady-phase apigenin levels in tissues of mice receiving apigenin in their diet.

Geographic variation in the incidence of colorectal cancer in the United States, 1998–2001

BACKGROUND

This study examined the incidence rates and risk factors for colorectal cancer in 9 geographic divisions in the United States.

METHODS

The colorectal cancer cases were diagnosed between 1998 and 2001 in 39 states and the District of Columbia (grouped into 9 geographic divisions in the United States). The association between colorectal cancer and geographic division was analyzed using the Poisson regression model controlling for demographics and ecologic measures of education, behavioral factors and colorectal cancer screening data extracted from the Behavioral Risk Factor Surveillance System.

RESULTS

The age-adjusted incidence rates of colorectal cancer were highest in the Middle Atlantic division, followed by New England division, East and West North Central divisions, East South Central and South Atlantic divisions, West South Central and Pacific divisions, with the lowest rate observed in the Mountain division. Old age, male gender, black race, less than a twelfth-grade education, smoking, and no physical activity were significantly associated with higher incidence rates of colorectal cancer, whereas having sigmoidoscopy/colonoscopy in the past 5 years, fecal occult blood test in the past year, and obesity were associated with lower incidence rates of colorectal cancer. The relative ranking of incidence rates of colorectal cancer across divisions changed after adjusting for these factors.

CONCLUSIONS

Significant geographic variation in colorectal cancer exists in the United States. Risk factors, including demographics, education, behavior, and screening use, can only partially explain the differences across geographic divisions.

Green tea polyphenol epigallocatechin-3 gallate (EGCG) affects gene expression of breast cancer cells transformed by the carcinogen 7,12-dimethylbenz[a]anthracene

Since the 1980s, the incidence of late-onset breast cancer has been increasing in the United States. Known risk factors, such as genetic modifications, have been estimated to account for approximately 5 to 10% of breast cancer cases, and these tend to be early onset. Thus, exposure to and bioaccumulation of ubiquitous environmental chemicals, such as polycyclic aromatic hydrocarbons (PAHs), have been proposed to play a role in this increased incidence. Treatment of female Sprague-Dawley rats with a single dose of the PAH 7,12-dimethylbenz[a]anthracene (DMBA) induces mammary tumors in approximately 90 to 95% of test animals. We showed previously that female rats treated with DMBA and given green tea as drinking fluid displayed significantly decreased mammary tumor burden and invasiveness and a significantly increased latency to first tumor. Here we used cDNA microarray analysis to elucidate the effects of the green tea polyphenol epigallocatechin-3 gallate (EGCG) on the gene expression profile in a DMBA-transformed breast cancer cell line. RNA was isolated, in quadruplicate, from D3-1 cells treated with 60 mug/mL EGCG for 2, 7, or 24 h and subjected to analysis. Semiquantitative RT-PCR and Northern blot analyses confirmed the changes in the expression of 12 representative genes seen in the microarray experiments. Overall, our results documented EGCG-altered expression of genes involved in nuclear and cytoplasmic transport, transformation, redox signaling, response to hypoxia, and PAHs.

Bile acids as carcinogens in human gastrointestinal cancers

Bile acids were first proposed to be carcinogens in 1939 and 1940. On the basis of later work with rodent models, bile acids came to be regarded as cancer promoters rather than carcinogens. However, considerable indirect evidence, obtained more recently, supports the view that bile acids are carcinogens in humans. At least 15 reports, from 1980 through 2003, indicate that bile acids cause DNA damage. The mechanism is probably indirect, involving induction of oxidative stress and production of reactive oxygen species that then damage DNA. Repeated DNA damage likely increases the mutation rate, including the mutation rate of tumor suppressor genes and oncogenes. Additional reports, from 1994 through 2002, indicate that bile acids, at the increased concentrations accompanying a high fat diet, induce frequent apoptosis. Those cells within the exposed population with reduced apoptosis capability tend to survive and selectively proliferate. That bile acids cause DNA damage and may select for apoptosis-resistant cells (both leading to increased mutation), indicates that bile acids are likely carcinogens. In humans, an increased incidence of cancer of the laryngopharyngeal tract, esophagus, stomach, pancreas, the small intestine (near the Ampulla of Vater) and the colon are associated with high levels of bile acids. The much larger number of cell generations in the colonic (and, likely, other gastrointestinal) epithelia of humans compared to rodents may allow time for induction and selection of mutations leading to cancer in humans, although not in rodents.

Evaluation of co-stimulatory effects of Tamarindus indica L. on MNU-induced colonic cell proliferation

Colonic cell proliferation is the prerequisite for the genesis of cancer. Experimental and epidemiologic evidence indicate dietary factors to be one of the commonest predisposing factors in the development of several types of cancers including large intestine. Here we have investigated the role of the fruit pulp of Tamarindus indica L. (TI), a tropical plant-derived food material, on the proliferating colonic mucosa using Swiss albino mice. Crypt cell proliferation rate (CCPR), on histological basis and [3H]-thymidine incorporation assay were chosen to evaluate the modulating potential of TI per se and in response to a subacute dose of N-nitroso N'-methyl urea (MNU). Descending colonic segment showed greater rate of cell proliferation than the ascending colon and cecum tissues isolated from the group 2 (TI-per se) when compared with group 1 (negative controls). It also revealed a positive correlation with the incorporation studies. Significant increase in the CCPR and radiolabeled precursor incorporation (p <0.001) was observed in MNU-induced+TI fed group of animals (group 4) in all the three segments when compared with control diet fed normal (group 1) as well as MNU-induced (group 3) animals. This study therefore indicates a co-stimulatory effect of TI on MNU-induced colonic cell kinetics.

Incidence of BRCA1 and BRCA2 Mutations in Young Korean Breast Cancer Patients

Purpose

The prevalence of BRCA-associated breast carcinoma in the Korean population has not been evaluated extensively.

Methods

Sixty Korean women who developed breast cancer by age 40 years were studied. Lymphocyte specimens from peripheral blood were processed for BRCA1 and BRCA2 by complete sequencing. Family history through three generations was obtained. Available paraffin-embedded tissue blocks were processed for immunohistochemical staining.

Results

In the cohort of 60 patients, nine patients with 11 deleterious mutations (six in BRCA1 and five in BRCA2) and seven missense mutations of unknown significance were found. Two patients had deleterious mutations in both BRCA1 and BRCA2 (double mutant). One half of the mutations were novel, and no founder mutations were observed in this cohort. Most of the BRCA-associated patients had no family history of breast and/or ovarian cancer. The expression of HER-2/neu, cyclin D1, and hormone receptors was less common, and p53 overexpression was more common in BRCA-associated tumors.

Conclusion

The prevalence of BRCA1 and BRCA2 mutations in Korean women with breast cancer at a young age was high. However, the penetrance, as evidenced by the low frequency of breast and ovarian cancers in family members, appears to be low. These data suggest that there may be different genetic and etiologic factors affecting transmission and penetrance of the BRCA genes in Korean patients with breast cancer diagnosed at a young age.

Association of p53 codon Arg72Pro and p73 G4C14-to-A4T14 at exon 2 genetic polymorphisms with the risk of Japanese breast cancer

BACKGROUND

The association between breast cancer risk and genetic polymorphisms of p53 at codon 72 (Arg72Pro) has been investigated by several studies, but the results are not consistent. The aim of this case-control study conducted in Nagoya, Japan, was to reconfirm the results of prior studies of polymorphisms of p53 Arg72Pro, and to test if polymorphisms of p73 G4C14-to-A4T14 at exon 2 (G4A) were also associated with breast cancer risk.

METHODS

The cases were 200 breast cancer patients who visited Aichi Cancer Center Hospital. The controls were 282 local citizens who underwent a health check-up. All cases and controls were recruited from Chubu Japan. Genotyping was carried out by polymerase chain reaction with confronting two-pair primers.

RESULTS

The p53 genotype distribution was 40.4% for Arg72 homozygous, 48.9% for heterozygous, and 10.7% for Pro72 homozygous in controls, and 32.0%, 50.0%, and 18.0% in cases, respectively. A comparison between cases and controls indicated a significantly increased risk for Pro72 homozygosity in cases (odds ratio=2.14; 95% confidence interval=1.21-3.79). The genotypic frequencies for p73 G4A were 54.3% for G/G, 39.7% for G/A, and 6.0% for A/A in controls; and 59.0%, 32.0%, and 9.0% in cases, respectively. There were no significant differences in p73 G4A frequency between cases and controls.

CONCLUSIONS

This study implies an association of breast cancer risk with the p53 polymorphism Arg72Pro, but not with p73 G4A.

Increased intake of n-3 polyunsaturated fatty acids elevates the level of apoptosis in the normal sigmoid colon of patients polypectomized for adenomas/tumors

To clarify preventive effects of n-3 polyunsaturated fatty acids (PUFAs) against colorectal carcinogenesis, we performed a dietary intervention in patients polypectomized for colorectal adenomas/tumors. For the former the following dietary advice was given: (1) decrease intake of fat from 30 to 20% of the total; (2) decrease consumption of n-6PUFAs containing foods, and increase intake of n-3 PUFAs for 2 years. For the comparison group only decreased intake of fat (30-20%) was recommended. Samples of normal sigmoid colon mucosa, obtained by colonoscopic check once a year during the intervention period, were used to investigate COX-2, cell proliferation (Ki67 expression), p53, Bcl-2 and Bax by immunostaining and determine the apoptosis index (AI) by terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate-nick end labeling (TUNEL) in 21 and 20 patients in experimental and comparison groups, respectively, who completed the 2 years of the intervention. After 24 months, the AI and positive cells of Bax and the ratio of Bax/Bcl-2 in normal sigmoid colon mucosa for the experimental group was significantly increased, whereas this change was not found in comparison group. These observations demonstrated for the first time that increased intake of n-3 PUFAs promotes apoptosis of normal colon mucosa in human which is related to effect on Bax or the balance of Bax and Bcl-2.

Colorectal cancer in 2003: old principles, new strategies

In the last two decades the prognosis of colorectal cancer has improved for two reasons: (i) the proportion of patients with localized disease has increased and treatment has been standardized, and (ii) new chemotherapeutic agents have led to a longer life expectancy for patients with advanced disease. In this review the current insights in disease etiology and treatment of localized and disseminated colorectal cancer are discussed.

Arginase in patients with breast cancer

The mean arginase activity in breast cancers (n = 80) was significantly higher than in control tissues and it accounted for 0.31 +/- 0.23 U/g wet tissue and 0.083 +/- 0.061 U/g (P < 0.05), respectively. With the cutoff value of 0.1 U/g wet tissue, raised arginase activity was observed in 74% of tumors. The preoperative arginase activity in blood serum from women with breast cancer was 11.2 +/- 7.9 U/l (n = 115), and it was significantly higher than in 70 healthy controls, where it was 5.7 +/- 2.4 U/l (P < 0.05). With the cutoff value for normal serum arginase activity above 8.0 U/l, the activity was raised in 10% of control individuals, and in 63% of women with breast cancer. The sensitivity and specificity of the arginase test in blood serum were 63% and 60%, respectively. Two isoforms immunologically identical to human kidney arginases (L-arginine amidinohydrolase) were found in both normal and cancerous breast tissues. The level of anionic form was similar in control and cancerous tissues, whereas the cationic isoform predominated in breast cancer. The cationic isoform was the only one present in serum of both ill and healthy women, and its level was higher in patients with breast cancer. Thus, it can be concluded that the cationic isoform is responsible for the increase of arginase activity in serum of patients with breast cancer.

Epidemiology and prevention of colorectal cancer

CRC, the second-leading cause of cancer death in the United States, is a highly preventable disease. Ironically, available and effective screening technologies are not consistently applied, even as new ones are developed. This discordance between preventive opportunity and practice conveys a sobering message regarding nontechnologic issues that must be addressed if the promise of CRC prevention is to be realized. Our response to this message will determine the public health impact of cancer prevention. In the 1980s, cancer chemoprevention was regarded as scientific speculation. Within the last decade, however, cancer has been recognized as a late, nonobligate stage of carcinogenesis, a chronic process that provides time and targets for preventive intervention. Further advances are emerging out of rigorous clinical testing, which remains the limiting factor in transforming ingenious concepts into useful tools for the prevention of CRC. The challenges and rewards of participation in chemoprevention research--both as patients and health care providers-have never been greater.

The antiproliferative effects of biologically active isomers of conjugated linoleic acid on human colorectal and prostatic cancer cells

The antiproliferative effects of two commercial preparations of conjugated linoleic acid (CLA) and their constituent isomers, cis-9, trans-11 (c9,t11)-CLA, c9,c11-CLA, and t10,c12-CLA, were determined in vitro using human colorectal (HT-29, MIP-101) and prostate (PC-3) carcinoma cells adapted to serum-free medium. The antiproliferative effects of the preparations were dependent upon the type and concentration of CLA isomer present. The t10,c12-CLA isomer exhibited the greatest potency against colorectal cancer proliferation, and the c9,t11 and t10,c12 isomers were moderately effective against prostate cancer. The t10,c12 isomer induced caspase-dependent apoptosis in MIP-101 and PC-3 cells. The results are the first to demonstrate that physiologic levels of two CLA preparations, their constituent isomers, and the c9,t11-CLA elongation product, c11,t13-conjugated eicosadienoic acid, induce dose-dependent inhibitory effects on cancer proliferation in vitro. Novel CLA preparations may prove effective as chemopreventive supplements for individuals at risk of or diagnosed with colorectal or prostate cancer.

Peptide YY as a growth factor for intestinal epithelium

Peptide YY is an abundant distal gut hormone that may play a significant role in intestinal epithelial proliferation. Gut epithelial cells express specific receptors for PYY, PYY induces proliferation in intestinal cells in vivo and in vitro, and the Y1 receptor subtype couples to mitogenic signaling pathways. In addition to proposed physiologic effects on gut mucosal maintenance, PYY proliferative effects may be hypothesized to contribute to pathophysiologic consequences of stimulated growth.

Epidemiology of colorectal cancer

Colorectal cancer is a important public health problem: there are nearly one million new cases of colorectal cancer diagnosed world-wide each year and half a million deaths. Recent reports show that, in the US, it was the most frequent form of cancer among persons aged 75 years and older. Given that the majority of cancers occur in elder people and with the ageing of the population in mind, this observation gives further impetus to investigating prevention and treatment strategies among this subgroup of the population. Screening research, recommendations and implementation is an obvious priority. While there are many questions to be resolved, it is apparent that many facets of colorectal cancer are becoming increasingly understood and prospects for prevention are becoming apparent. Achieving colorectal cancer control is the immediate challenge.

Folate deficiency in vitro induces uracil misincorporation and DNA hypomethylation and inhibits DNA excision repair in immortalized normal human colon epithelial cells

Epidemiological studies have indicated that folic acid protects against a variety of cancers, particularly cancer of the colorectum. Folate is essential for efficient DNA synthesis and repair. Moreover, folate can affect cellular S-adenosylmethionine levels, which regulate DNA methylation and control gene expression. We have investigated the mechanisms through which folate affects DNA stability in immortalized normal human colonocytes (HCEC). DNA strand breakage, uracil misincorporation, and DNA repair, in response to oxidative and alkylation damage, were determined in folate-sufficient and folate-deficient colonocytes by single cell gel electrophoresis. In addition, methyl incorporation into genomic DNA was measured using the bacterial enzyme Sss1 methylase. Cultured human colonocyte DNA contained endogenous strand breaks and uracil. Folate deficiency significantly increased strand breakage and uracil misincorporation in these cells. This negative effect on DNA stability was concentration dependent at levels usually found in human plasma (1-10 ng/ml). DNA methylation was decreased in HCEC grown in the absence of folate. Conversely, hypomethylation was not concentration dependent. Folate deficiency impaired the ability of HCEC to repair oxidative and alkylation damage. These results demonstrate that folic acid modulates DNA repair, DNA strand breakage, and uracil misincorporation in immortalized human colonocytes and that folate deficiency substantially decreases DNA stability in these cells.

Comparative study for histology, proliferative activity, glycoproteins, and p53 protein between old and recent colorectal adenomas in Japan

The incidence of colorectal carcinoma is increasing in Japan. Malignant transformation in colorectal neoplasia is usually considered to be owing to adenoma-carcinoma sequence. Elucidation of the recent alteration in the biological properties of colorectal adenoma is sure to be useful to understand the recent increase of the colorectal carcinoma in Japan. We compared the histopathological feature, mitotic index, proliferative activity (Ki-67 labeling index), expression of glycoproteins such as MUC2 mucin, sialyl Lewis A (SLe(a)) and sialyl dimeric Lewis X (SLe(x)), and p53 protein overexpression, between 108 adenomas in the old period (Group A, from 1969 to 1985) and 140 adenomas in the recent period (Group B, from 1995 to 1998). The histological dysplasia, mitotic index and Ki-67 labeling index of the adenomas were significantly higher in Group B than in Group A. In contrast, the expression of MUC2 mucin, which is considered to be a differentiation factor of intestinal mucosal epithelium, was significantly reduced in Group B than in Group A. The SLe(a) and SLe(x) expressions showed no significant difference between them. The p53 expression showed no significant difference between them, except for the moderate dysplasia. These findings indicate that recent colorectal adenomas show more advanced degrees of histological dysplasia, more rapid growth, and reduced differentiation than colorectal adenomas, which developed at earlier times, and may be related with the recent high incidence of colorectal carcinoma in Japan.

The role of bile acids in carcinogenesis

Bile acids play a role in colorectal carcinogenesis as evidenced by epidemiological and experimental studies. Some bile acids stimulate growth of normal colonic and adenoma cells, but not of colorectal cancer cells. Moreover, bile acids stimulate invasion of colorectal cancer cells, at least in vitro. One possible mechanism of action is bile acid-induced DNA binding and transactivation of the activator protein-1 (AP-1) by co-operate activation of extracellular signal-regulated kinases (ERKs) and PKC signaling. In the present paper, we review the mechanisms by which bile acids influence carcinogenesis.

Fruit, vegetables, dietary fiber, and risk of colorectal cancer

BACKGROUND

Several recent large prospective cohort studies have failed to demonstrate the presumed protective effect of fruit, vegetable, and dietary fiber consumption on colorectal cancer risk. To further explore this issue, we have examined these associations in a population that consumes relatively low amounts of fruit and vegetables and high amounts of cereals.

METHODS

We examined data obtained from a food-frequency questionnaire used in a population-based prospective mammography screening study of women in central Sweden. Women with colorectal cancer diagnosed through December 31, 1998, were identified by linkage to regional cancer registries. Cox proportional hazards models were used to estimate relative risks. All statistical tests were two-sided.

RESULTS

During an average 9.6 years of follow-up of 61 463 women, we observed 460 incident cases of colorectal cancer (291 colon cancers, 159 rectal cancers, and 10 cancers at both sites). In the entire study population, total fruit and vegetable consumption was inversely associated with colorectal cancer risk. Subanalyses showed that this association was due largely to fruit consumption. The association was stronger, however, and the dose-response effect was more evident among individuals who consumed the lowest amounts of fruit and vegetables. Individuals who consumed less than 1.5 servings of fruit and vegetables per day had a relative risk for developing colorectal cancer of 1.65 (95% confidence interval = 1.23 to 2.20; P(trend) =.001) compared with individuals who consumed more than 2.5 servings. We observed no association between colorectal cancer risk and the consumption of cereal fiber, even at amounts substantially greater than previously examined, or of non-cereal fiber.

CONCLUSIONS

Individuals who consume very low amounts of fruit and vegetables have the greatest risk of colorectal cancer. Relatively high consumption of cereal fiber does not appear to lower the risk of colorectal cancer.

Diet and cancer

The large differences in cancer rates among countries, striking changes in these rates among migrating populations, and rapid changes over time within countries indicate that some aspect of lifestyle or environment is largely responsible for the common cancers in Western countries. Dietary fat has been hypothesized to be the key factor because national consumption is correlated with the international differences. However, detailed analyses in large prospective studies have not supported an important role of dietary fat. Instead, positive energy balance, reflected in early age at menarche and weight gain as an adult, is an important determinant of breast and colon cancers, consistent with numerous studies in animals. As a contributor to positive energy balance, and possibly by other mechanisms, physical inactivity has also been shown to be a risk factor for these diseases and in part accounts for the international differences. Although the percentage of calories from fat in the diet does not appear related to risk of colon cancer, greater risks have been seen with higher consumption of red meat, suggesting that factors other than fat per se are important. In many case-control studies, a high consumption of fruits and vegetables has been associated with reduced risks of numerous cancers, but recent prospective studies suggest these associations may have been overstated. Among the factors in fruits and vegetables that have been examined in relation to cancer risk, present data most strongly support a benefit of higher folic acid consumption in reducing risks of colon and breast cancers. These findings have been bolstered by an association between incidence of colon cancer and a polymorphism in the gene for methylenetetrahydrofolate reductase, an enzyme involved in folic acid metabolism. The benefits of folic acid appear strongest among persons who regularly consume alcohol, which itself is associated with risk of these cancers. Numerous other aspects of diet are hypothesized to influence the risks of cancers in Western countries, but for the moment the evidence is unclear.

Prospective study of colorectal cancer risk and physical activity, diabetes, blood glucose and BMI: exploring the hyperinsulinaemia hypothesis

A sedentary lifestyle, obesity, and a Westernized diet have been implicated in the aetiology of both colorectal cancer and non-insulin dependent diabetes mellitus, leading to the hypothesis that hyperinsulinaemia may promote colorectal cancer. We prospectively examined the association between colorectal cancer risk and factors related to insulin resistance and hyperinsulinaemia, including BMI, physical activity, diabetes mellitus, and blood glucose, in a cohort of 75 219 Norwegian men and women. Information on incident cases of colorectal cancer was made available from the Norwegian Cancer Registry. Reported P values are two-sided. During 12 years of follow up, 730 cases of colorectal cancer were registered. In men, but not in women, we found a negative association with leisure-time physical activity (P for trend = 0.002), with an age-adjusted RR for the highest versus the lowest category of activity of 0.54 (95% CI = 0.37-0.79). Women, but not men, with a history of diabetes were at increased risk of colorectal cancer (age-adjusted RR = 1.55; 95% CI = 1.04-2.31), as were women with non-fasting blood glucose > or = 8.0 mmol l(-1)(age-adjusted RR = 1.98; 95% CI = 1.31-2.98) compared with glucose <8.0 mmol l(-1). Overall, we found no association between BMI and risk of colorectal cancer. Additional adjustment including each of the main variables, marital status, and educational attainment did not materially change the results. We conclude that the inverse association between leisure-time physical activity and colorectal cancer in men, and the positive association between diabetes, blood glucose, and colorectal cancer in women, at least in part, support the hypothesis that insulin may act as a tumour promoter in colorectal carcinogenesis.

Being breastfed in infancy and breast cancer incidence in adult life: results from the two nurses' health studies

Events during perinatal and early life may influence the incidence of breast cancer in adult life, and some case-control studies suggest that having been breastfed may reduce breast cancer risk. The authors studied this association among premenopausal and postmenopausal women by using data from the two Nurses' Health Studies, the Nurses' Health Study (using data from 1992 to 1996) and the Nurses' Health Study II (using data from 1991 to 1997). A history of being breastfed was self-reported by the study participants. During a total of 695,655 person-years, 1,073 cases of invasive breast cancer were diagnosed. The authors did not observe any important overall association between having been breastfed and the development of breast cancer later in life among premenopausal women (covariate-adjusted relative risk = 0.97, 95% confidence interval (CI): 0.78, 1.20) or postmenopausal women (covariate-adjusted relative risk = 1.12, 95% CI: 0.92, 1.37). No significant trend was observed with increasing duration of breastfeeding. The authors also used data on breastfeeding retrospectively collected from 2,103 mothers of participants of the two Nurses' Health Studies. With the mothers' reports, the covariate-adjusted odds ratio of breast cancer was 1.11 (95% CI: 0.88, 1.39) for women who were breastfed compared with those who were not. Data from these two large cohorts do not support the hypothesis that being breastfed confers protection against subsequent breast cancer.

Anticancer properties of bovine milk

Improved means of cancer prevention and treatment remain key goals of global health programmes. This is particularly true in Western society, where the elderly represent a large proportion of the population, and where the likelihood of tumour development is compounded by risk factors such as poor fibre/high fat diets and environmental pollution. Dietary intervention represents an attractive, non-invasive means of providing anticancer preventative and therapeutic benefits to at-risk individuals. This review focuses on the evidence for anticancer properties of bovine milk and milk-derived components. Evidence of a role for whole milk constituents, as well as purified minor components, in combating tumorigenesis is outlined. Shortcomings in current studies are highlighted, and future opportunities for targeted research to characterize important anticancer properties of milk are discussed.

Selected micronutrients and colorectal cancer. a case-control study from the canton of Vaud, Switzerland

The association between dietary intake of various micronutrients and colorectal cancer risk was analysed using data from a case-control study conducted between 1992 and 1997 in the Swiss Canton of Vaud. Cases were 223 subjects (142 (64%) males, 81 (36%) females; median age 63 years) with incident, histologically confirmed colon (n=119; 53%) or rectal (n=104; 47%) cancer, and controls were 491 subjects (211 (43%) males, 280 (57%) females; median age 58 years; range 27-74) admitted to the same university hospital for a wide spectrum of acute non-neoplastic conditions, unrelated to long-term modifications of diet. Dietary habits were investigated using a validated food frequency questionnaire (FFQ). Odds ratios (OR) were obtained after allowance for age, sex, education, smoking, alcohol, body mass index, physical activity, and total energy and fibre intake. No significant association was observed for calcium, retinol, folate, vitamin D or E. The risk of colorectal cancer was directly associated with measures of iron intake (OR=2.43 for the highest tertile, 95% confidence interval (CI): 1.2-5.1) and inversely associated with vitamin C (OR=0.45; 95% CI: 0.3-0.8), and non-significantly with total carotenoids (OR=0.66, 95% CI: 0.4-1.1). Among various individual carotenoids considered, inverse associations were observed for alpha-carotene, beta-carotene and lutein/zeaxanthin. These findings were consistent across the strata of gender and age, and support the hypothesis that selected micronutrients have a favourable effect on colorectal carcinogenesis.

Expression of the aryl hydrocarbon receptor/transcription factor (AhR) and AhR-regulated CYP1 gene transcripts in a rat model of mammary tumorigenesis

Exposure to ubiquitous environmental chemicals, such as polycyclic aromatic hydrocarbons (PAH), may contribute to human breast cancer. In animals, PAH induce tumors in part by activating the aryl hydrocarbon receptor (AhR)/transcription factor. Historically, investigations into AhR-regulated carcinogenesis have focused on AhR-dependent transcriptional regulation of cytochrome P450 (CYP) enzymes which oxidize PAH to mutagenic intermediates. However, recent studies suggest that the AhR directly regulates cell growth. Given the postulated role of the AhR in carcinogenesis, we predicted that: (1) tissue predisposed to PAH tumorigenesis would express the AhR and (2) aberrant AhR and/or AhR-regulated gene expression would accompany malignant transformation. To test these hypotheses, AhR and CYP1 protein and/or mRNA levels were evaluated in rat mammary tumors induced with 7, 12-dimethylbenz[a]anthracene (DMBA), a prototypic PAH and AhR ligand. Results indicate modest AhR expression in normal mammary myoepithelial and ductal epithelial cells. In contrast, high AhR levels were detected in DMBA-induced tumors. Nuclear AhR localization in tumors suggested constitutive AhR activation. In situ hybridization and quantitative RT-PCR assays indicated high AhR mRNA levels in neoplastic epithelial cells. While both AhR-regulated CYP1A1 and CYP1B1 mRNAs were induced in breast tissue within 6 h of DMBA gavage, only CYP1B1 mRNA remained elevated in tumors. These results: (1) help explain targeting of breast tissue by carcinogenic PAH, (2) imply that AhR and CYP1B1 hyper-expression represent molecular biomarkers for, at least, PAH-induced mammary cell transformation, and (3) suggest mechanisms through which the AhR may contribute to carcinogenesis well after exogenous AhR ligands have been eliminated.

Update on cancer control in women

The global cancer burden in women appears to have stabilized according to the most recent estimates available although the distribution of cancer types appears to be changing with a sharp contrast between the increase in the absolute numbers of breast cancers and a decline in cervix cancers. Prospects for cancer control in women appear to be good within our current knowledge and deserve close attention. Rates of lung cancer in women are increasing substantially in many countries and seem set to overtake breast cancer as the commonest form of cancer death in women in many parts of the world. These changes are due to the effects of cigarette smoking, a habit which women widely embraced during the second half of the last century. The high levels of smoking currently in young women, which have yet to have their full impact on death rates, constitute an important hazard not only for future cancer risks but for several other important causes of death. There is strong and consistent evidence that increased consumption levels of fruit and vegetables is associated with reduced risks of many common forms of cancer including breast cancer. Although the breast is the commonest form of cancer in women in most western countries, the etiology of this disease remains elusive and preventable causes remain to be identified. Endogenous hormones also appear to have a role in cancer risk in women: oral contraceptives seem to increase slightly the risk of breast cancer in users in the use and in the immediate post-use period, but 10 years after cessation the risk again returns to that of never users. Oral contraceptive usage also appears to be protective against ovarian and endometrial cancer. The use of hormonal replacement therapy (HRT) appears to increase the risk of endometrial cancer and a positive association with breast cancer risk appears to exist. Within our current knowledge of the epidemiology of cancer in women, the most important preventive strategies would appear to be the prevention of cigarette smoking and increased dietary intake of vegetables and fruits. Screening has also shown to be effective in reducing incidence and mortality of cervix cancer and mortality from breast cancer. Although more work is needed, it is becoming clear that there could be an important role of HPV testing to further enhance cervix cancer screening. There are important variations in survival from a variety of cancers which are due to factors unrelated to the tumor behavior and that there are significant variations in survival from cancer. Reduction of these gaps could lead to a reduction in cancer mortality and contribute towards increased prospects for cancer control in women.

Combined influence of genetic and dietary factors on colorectal cancer incidence in Japanese Americans

Colorectal cancer (CRC) rates for Japanese migrants to the United States increased rapidly to surpass the level of the host population. CRC rates for the Japanese in Hawaii and California are now the highest in the world. Rates for this disease have also increased in Japan, presumably as the result of the westernization of the diet. A series of population-based studies in Hawaii was undertaken to determine which dietary factors are responsible for this remarkable susceptibility of the Japanese to CRC and whether genetic factors are also involved. A first case-control study suggested that a high intake of red meat is a major risk factor for the disease in Hawaii Japanese men and that family history of CRC among first-degree relatives may strongly modify this association. A case-control family study is currently being completed to explore further the interaction between family history and the intake of red meat after adjustment for environmental covariates among family members. Also, a segregation analysis will guide gene discovery studies among high-risk Japanese families being recruited in the Cooperative Family Registry for Colorectal Cancer Studies. Retrospective and prospective studies are also ongoing to test associations of CRC with specific polymorphisms in genes controlling the metabolic activation or detoxification of the carcinogens associated with a diet high in red meat. Preliminary results suggest an association of the combined rapid NAT2 genotype and rapid CYP1A2 phenotype with CRC in individuals consuming well-done red meat. Populations in which dramatic changes in cancer incidence have occurred may offer opportunities to identify gene-environment interactions.

Effect of colonic luminal components on induction of apoptosis in human colonic cell lines

Apoptosis is central to cell number regulation in the colonic epithelium, and interest in its role in colon carcinogenesis has been growing rapidly. It thus becomes of interest to characterize luminal components, possibly of dietary origin, that may influence this process. We have investigated the sensitivity of two human colonic cell lines, the human adenocarcinoma cell line (HT-29) and the human fetal colonic mucosa cell line (FHC), to induction of apoptosis by sodium butyrate, bile acids, and human fecal water fractions. The apoptotic effect has been studied by 1) morphological changes in cells examined by fluorescence microscopy, 2) DNA fragmentation analysis by gel electrophoresis, 3) flow cytometry analysis of DNA strand breaks assessed by the terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling assay (TUNEL), and 4) poly(ADP-ribose) polymerase cleavage by Western blot. Sodium butyrate and bile acids induced a time- and concentration-dependent apoptosis in both cell lines. Quantitation of this effect, by use of the TUNEL assay, indicated that deoxycholic acid was most effective in inducing this effect at lower concentrations and at shorter times. Apoptotic effects were also observed, in both cell lines, when the cells were exposed to intact human fecal waters (the fecal fraction in direct contact with the epithelium) and their lipid extracts, with the intact samples being more effective. Although all fecal waters examined induced apoptosis, quantitation of the effect by the TUNEL assay indicated that the ability to induce apoptosis differed markedly between samples. Induction of apoptosis by the fecal waters was not correlated to cytotoxicity but was negatively correlated to the pH of the samples. Interestingly, the cells derived from the fetal mucosa (FHC) were consistently less sensitive to apoptotic effects of the luminal components than the tumor-derived cells (HT-29). Thus human fecal water fractions induce apoptosis in colonic cells, and this effect is not due to lipid components alone.

Oxidants and antioxidants in breast cancer

Although a number of risk factors have been identified for breast cancer, mechanisms by which they increase risk of the disease are not clear. Breast cancer etiology could, in part, be related to oxidative stress. Recognized risk factors for breast cancer include a family history of the disease. BRCA1 is needed for post-transcriptional repair of oxidative damage, indicating that oxidative stress may be an important risk factor for women with a family history of the disease. Reproductive and hormonal factors that result in greater exposure to circulating estrogens also increase risk, and steroid hormones are metabolized to reactive quinones and hydroquinones, which can directly damage DNA. Alcohol consumption is associated with increased risk, and the metabolism of alcohol results in production of DNA-damaging reactive oxygen species (ROS). Finally, the inverse relationship noted with consumption of fruits and vegetables could be related to their being a source of antioxidant vitamins. Endogenous factors may play an equally important role in the effects of oxidative stress on breast carcinogenesis. Genetic variability in enzymes that result in increased production of ROS and those that protect the cell from oxidative stress could also have an impact for risk of the disease. In this review, a rationale is given for linking breast cancer risk factors to oxidative stress. The possible role of genetic polymorphisms in a number of enzymes that may be important in affecting levels of ROS to which the cell is exposed, as well as those that protect the cell from oxidative stress, is discussed.

Apolipoprotein E genetic polymorphism, serum lipoproteins, and breast cancer risk

Apolipoprotein E (apoE) is a polymorphic gene involved in lipid metabolism with three common variant alleles (epsilon2, epsilon3, and epsilon4). The epsilon4 allele has been associated with elevated levels of cholesterol as well as greater risk of coronary heart disease and Alzheimer's disease. In this case-control study we examined whether apoE genotype affected the association between serum lipids and breast cancer risk. In a subset of a study in western New York, 260 women with incident, primary breast cancer and 332 community controls were interviewed and provided blood samples. Polymerase chain reaction-restriction fragment length polymorphism analyses of the apoE polymorphism were performed. Participants were classified as apoE2 (epsilon2, epsilon2 or epsilon2, epsilon3), apoE3 (epsilon3, epsilon3), or apoE4 (epsilon4, epsilon4 or epsilon4, epsilon3). No unconditional logistic regression was used to compute adjusted odds ratios (ORs) and 95% confidence intervals (CI). Compared with women with the apoE3 genotype, there were no associations with risk for women with the apoE2 (OR=1.0; 95% CI=0. 91-1.64) or apoE4 genotype (OR=0.97; 95% CI=0.63-1.54). Higher serum levels of total cholesterol, HDL cholesterol, and LDL cholesterol were not associated with risk, either in the total sample or among subgroups of women defined by apoE genotype. Women with the highest serum triglyceride levels had an increase in risk (OR=1.63; 95% CI=1. 03-2.59) compared to women with the lowest levels. This effect was not apparent among women with the apoE2 or apoE3 genotype, but much stronger among women with the apoE4 genotype (OR=4.69; 95% CI=1. 49-14.7). These data suggest that the apoE4 genotype may modify the association between serum triglycerides and breast cancer risk.

A diet high in fat and meat but low in dietary fibre increases the genotoxic potential of 'faecal water'

To determine the effects of different diets on the genotoxicity of human faecal water, a diet rich in fat, meat and sugar but poor in vegetables and free of wholemeal products (diet 1) was consumed by seven healthy volunteers over a period of 12 days. One week after the end of this period, the volunteers started to consume a diet enriched with vegetables and wholemeal products but poor in fat and meat (diet 2) over a second period of 12 days. The genotoxic effect of faecal waters obtained after both diets was assessed with the single cell gel electrophoresis (Comet assay) using the human colon adenocarcinoma cell line HT29 clone 19a as a target. The fluorescence and length of the tails of the comet images reflects the degree of DNA damage in single cells. The mean DNA damage, expressed as the ratio of tail intensity (fluorescence in the tail) to total intensity of the comet after incubation with faecal water from volunteers consuming diet 1 was about twice as high as for diet 2. The susceptibility of the cells incubated with faecal water to DNA damage caused by additional hydrogen peroxide treatment showed no significant differences between the two diets. Generation of oxidized pyrimidine and purine bases revealed no differences after pretreatment with both types of faecal water. The results indicate that diets high in fat and meat but low in dietary fibre increase the genotoxicity of faecal water to colonic cells and may contribute to an enhanced risk of colorectal cancer.

DNA adducts in normal tissue adjacent to breast cancer: a review

To identify possible extrinsic and intrinsic DNA-damaging factors involved in breast cancer etiology, we measured the level of aromatic and lipid peroxidation-related DNA adducts in samples of normal tissue adjacent to breast tumors obtained from 87 breast cancer patients using 32P postlabeling. Twenty-nine cancer-free women who underwent reduction mammoplasty served as controls. Tissue samples from the breast cancer patients contained significantly higher levels of aromatic DNA adducts (mean +/- SEM: 97.4 +/- 23.4 x 109 nucleotides) than did samples obtained from the controls (mean +/- SEM: 23.5 +/- 6.9 x 109 nucleotides). A bulky benzo[a]pyrene (BP)-like adduct was detected in 41% of the cancer patients, but in none of the controls. The level of this adduct was extremely high in some patients (> 1/106). While 88% of the patients with a smoking history had smoking-specific DNA adducts in their breast tissues, the presence of BP-like adduct was not related to smoking history. The cancer patients also had a significantly higher level of lipid peroxidation-related DNA adducts than did controls. The level of these adducts correlated with the presence of the BP-like adduct. To further explore the origin of the BP-like adduct, we examined the level of polycyclic aromatic hydrocarbon (PAH)-DNA adducts and 8-hydroxyguanine (8-OH-G) in tissue sections obtained from 37 breast cancer patients using immunocytochemistry. We found that patients who had the BP-like adduct showed significantly greater immunostaining for PAH adducts than did those without the BP-like adduct (p = 0.04). In addition, we found that adipocytes tended to have greater immunostaining for the PAH adducts than did epithelial cells. On the other hand, epithelial cells tended to have a higher frequency and greater intensity of staining for 8-OH-G than did adipocytes. The detection of PAH adducts, lipid peroxidation-related DNA adducts, and 8-OH-G in normal breast tissues of breast cancer patients suggests that both exogenous and endogenous DNA-damaging factors may be involved in breast cancer. The exogenous source may involve the types of carcinogen exposure other than cigarette smoking, and the endogenous source may involve oxidative stress associated with normal metabolic activities.

Second primary tumors after prostate carcinoma

BACKGROUND

Several large datasets have shown a reduced risk of all neoplasms after a diagnosis of prostate carcinoma but an increased incidence rate of urologic carcinoma has been suggested.

METHODS

Data collected by the Cancer Registries of the Swiss Cantons of Vaud and Neuchâtel (approximately 760,000 inhabitants) were used to estimate the incidence rate of a second primary tumor after a diagnosis of prostate carcinoma. A total of 4503 cases registered between 1974 and 1994 were followed until the end of 1996 (17,065 person-years).

RESULTS

A total of 380 second primary neoplasms were observed versus 534.1 expected primary neoplasms (standardized incidence ratio [SIR] = 0.7; 95% confidence interval, 0.6-0.8). SIRs were significantly below unity for lung carcinoma (SIR = 0.7) and other major tobacco-related neoplasms, including those of the mouth or pharynx (SIR = 0.5), esophagus (SIR = 0.4), pancreas (SIR = 0.5), and larynx (SIR = 0.8). There was no excess rate of subsequent urologic carcinoma (SIR = 1.0) or colorectal carcinoma (SIR = 0.9). The reduced SIRs for lung carcinoma were stronger in elderly men (age >/= 75 years) and in patients with a shorter period since diagnosis (< 5 years).

CONCLUSIONS

The incidence of all neoplasms was reduced significantly in men diagnosed with prostate carcinoma. Selection of the population, under-registration of second primary tumors, and reduced surveillance in elderly men with prostate carcinoma may, at least in part, explain this reduction in risk. No excess risk was observed for the complex of urologic neoplasms nor for tobacco-related neoplasms. This finding would not support an association between cigarette smoking and prostate carcinoma.

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.

Nutritional strategies in the prevention of colorectal cancer

A variety of dietary factors have been implicated as agents that can modulate the development of malignancies of the gastrointestinal tract, particularly colorectal cancer. The effects of fat, red meat, fruits, vegetables, and alcohol on colorectal carcinogenesis have been examined extensively and appear to play substantial roles. Although fiber may play a protective role, recent studies raise the question of whether the protection is conveyed by other components in fiber-laden foods. Folate, selenium, calcium, and omega-3 fatty acids have emerged as factors more recently but may be equally important agents in nutritional chemoprevention, whereas the role of antioxidant vitamins is less certain. Until more firm data are available, the dietary recommendations provided by the American Cancer Society and the National Cancer Institute are appropriate for use in counseling patients on this issue.

Fat and dietary fiber intake and colon cancer mortality: a chronological comparison between Japan and the United States

To estimate the role of dietary fiber (DF) and fat in the striking growth of colon cancer mortality in Japan after World War II, we analyzed relations between the above variables in comparison with those in the United States. In the United States, fat intake grew by only one-third over the past 70 years (from 124 g in 1909-1913 to 166 g in 1984), whereas colon cancer mortality increased fourfold (from 5 to 20 per 100,000). In Japan, although fat intake roughly doubled during the 40 years after World War II (from 20 to 38 g), colon cancer mortality grew 5.5-fold (from 2 to 11 per 100,000). It is difficult to give a consistent explanation for the growth patterns of colon cancer mortality in both countries on the basis of fat consumption as a cancer promoter. In the United States, DF intake continuously dwindled at a level always less than in Japan throughout this century. DF intake in Japan also declined rather steadily, except for war time, over the past 80 years. However, with regard to the growth pattern of colon cancer mortality, it began rising steeply around the period when the daily DF intake diminished below 20 g, suggesting the presence of a threshold level in this neighborhood in preventing the development of colon cancer.

The influence of maternal diet on breast cancer risk among female offspring

The induction of breast cancer is a long process, containing a series of biological events that drive a normal mammary cell towards malignant growth. However, it is not known when the initiation of breast cancer occurs. One hypothesis is that a high estrogenic environment during the perinatal period increases subsequent breast cancer risk. There are many sources of extragonadal estrogens, particularly in the diet. The purpose of this paper is to review the evidence that a high maternal intake of dietary fats increases serum estrogens during pregnancy and increases breast cancer risk in daughters. Our animal studies show that a high maternal consumption of corn oil consisting mainly of linoleic acid (omega-6 polyunsaturated fatty acid, PUFA), increases both circulating estradiol (E2) levels during pregnancy and the risk of developing carcinogen-induced mammary tumors among the female rat offspring. A similar increase in breast cancer risk occurs in female offspring exposed to injections of E2 through their pregnant mother. Our data suggest that the mechanisms by which an early exposure to dietary fat and/or estrogens increases breast cancer risk is related to reduced differentiation of the mammary epithelial tree and increased number of mammary epithelial cell structures that are known to the sites of neoplastic transformation. These findings may reflect our data of the reduced estrogen receptor protein levels and protein kinase C activity in the developing mammary glands of female rats exposed to a high-fat diet in utero. In summary, a high dietary linoleic acid intake can elevate pregnancy estrogen levels and this, possibly by altering mammary gland morphology and expression of fat- and/or estrogen-regulated genes, can increase breast cancer risk in the offspring. If true for women, breast cancer prevention in daughters may include modulating the mother's pregnancy intake of some dietary fats.

Risk factors for breast cancer in nulliparous women

The relation between hormonal and lifestyle factors and breast cancer risk in nulliparae was investigated using data from two case-control studies conducted in Italy between 1983 and 1994. The study included 1041 nulliparae with histologically confirmed incident breast cancer and 1002 nulliparous controls admitted to hospital for a wide range of acute, non-neoplastic, nonhormone-related diseases. In premenopausal nulliparae, there was an inverse relation with age at menarche [odds ratios (OR) 0.45; 95% confidence intervals (CI) 0.24-0.86 for > or = 15 years vs < 12], while no association emerged in postmenopausal. Breast cancer risk increased with age at menopause, the OR being 1.91 (95% CI 1.26-2.90) for nulliparae reporting age at menopause > or = 53 years compared with < 45. Abortion was not related to breast cancer risk, the OR being 0.92 for any spontaneous, 0.97 for any induced and 0.77 for > or = 2 total abortions compared to none. The OR was 1.75 (95% CI 1.03-2.97) for women reporting their first abortion at age > or = 30 years compared with < 30. Oral contraceptives and hormone replacement therapy in menopause were moderately related to risk. The OR was 2.71 (95% CI 1.85-3.95) in nulliparae with a family history of breast cancer and 1.60 (95% CI 1.20-2.14) in those with a history of benign breast disease. Compared with nulliparae reporting a low physical activity, the OR was 0.79 (95% CI 0.54-1.16) for those reporting intermediate/high activity. Breast cancer risk increased with total energy intake, the OR being 1.65 (95% CI 0.99-2.75) in the highest tertile; beta-carotene was inversely related to risk (OR 0.60, 95% CI 0.38-0.95) for the highest tertile. Thus, most risk factors for breast cancer in nulliparae were similar to those in women generally.

Serum folate, homocysteine and colorectal cancer risk in women: a nested case-control study

Accumulating evidence suggests that folate, which is plentiful in vegetables and fruits, may be protective against colorectal cancer. The authors have studied the relationship of baseline levels of serum folate and homocysteine to the subsequent risk of colorectal cancer in a nested case-control study including 105 cases and 523 matched controls from the New York University Women's Health Study cohort. In univariate analyses, the cases had lower serum folate and higher serum homocysteine levels than controls. The difference was more significant for folate (P < 0.001) than for homocysteine (P = 0.04). After adjusting for potential confounders, the risk of colorectal cancer in the subjects in the highest quartile of serum folate was half that of those in the lowest quartile (odds ratio, OR = 0.52, 95% confidence interval, CI = 0.27-0.97, P-value for trend = 0.04). The OR for the highest quartile of homocysteine, relative to the lowest quartile, was 1.72 (95% CI = 0.83-3.65, P-value for trend = 0.09). In addition, the risk of colorectal cancer was almost twice as high in subjects with below-median serum folate and above-median total alcohol intake compared with those with above-median serum folate and below-median alcohol consumption (OR = 1.99, 95% CI = 0.92-4.29). The potentially protective effects of folate need to be confirmed in clinical trials.

Diet, body size and menarche in a multiethnic cohort

A multiethnic cohort of 1378 Southern California school girls aged 8-13 years was followed for 4 years to evaluate factors predicting age at menarche, a risk factor for breast cancer. Height and weight were measured and dietary intake was assessed using a semi-quantitative food frequency questionnaire. Of 939 girls providing data on menarcheal status, 767 were premenarcheal at the start of the study; 679 girls provided acceptable dietary data and were included in the analyses. Cox proportional hazards models were used to assess the relationship between diet, body size, ethnicity and age at menarche. Hispanic, Asian/Pacific Island and African-American girls were more likely to experience early menarche than non-Hispanic white girls. Tall (> 148.6 cm) versus short (< 135.9 cm) girls experienced earlier menarche (relative hazard (RH) = 2.9, 95% confidence interval (CI) 2.1-4.1) as did those with high Quetelet's index (QI, kg m(-2)) (> 20.7) versus low QI (< 16.1) (RH = 2.2, 95% CI 1.7-2.9). Of all the dietary variables analysed, only energy intake was related to age at menarche. High versus low energy intake (> 12,013 kJ vs < 7004 kJ) was associated with a delay in menarche (RH = 0.7, 95% CI 0.5-0.9); this finding was limited to a subset of heavy Hispanic girls who appeared to underreport their dietary intake.

A comparison of prospective and retrospective assessments of diet in a study of colorectal cancer

Dietary factors are widely studied as risk factors for colorectal cancer, with much information from case-control studies. We evaluated the validity of dietary data from a retrospective case-control study of diet and colorectal cancer. As part of the alpha-Tocopherol, beta-Carotene Cancer Prevention Study, diet was assessed at baseline and after diagnosis for colorectal cancer cases and at baseline and regularly during the trial for a random control group. The dietary assessment referred to the previous 12 months (in cases before diagnosis). In the two dietary assessments, the cases reported a greater increase in consumption of fruits and dairy products and a decrease in consumption of potatoes. Accordingly, relative risks for colorectal cancer by baseline dietary data differed markedly from odds ratios from case-control data; e.g., relative risk for a 652-mg increase in calcium intake was 0.79 (95% confidence interval = 0.48-1.30) in case-cohort analysis vs. an odds ratio of 1.57 (95% confidence interval = 1.06-2.33) for case-control analysis. The most likely explanation is the influence of current diet on recall of prediagnosis diet and effects of occult cancer on diet in the year before cancer diagnosis, which have implications for interpretation of case-control studies in evaluating associations between diet and colorectal cancer.

Food groups and colorectal cancer risk

Most studies of diet and colorectal cancer have considered nutrients and micronutrients, but the role of foods or food groups remains open to debate. To elucidate the issue, we examined data from a case-control study conducted between 1992 and 1997 in the Swiss canton of Vaud. Cases were 223 patients (142 men, 81 women) with incident, histologically confirmed colon (n= 119) or rectal (n= 104) cancer (median age 63 years), linked with the Cancer Registry of the Swiss Canton of Vaud, and controls were 491 subjects (211 men, 280 women, median age 58 years) admitted to the same university hospital for a wide spectrum of acute non-neoplastic conditions unrelated to long-term modifications of diet. Odds ratios (OR) were obtained after allowance for age, sex, education, smoking, alcohol, body mass index, physical activity and total energy intake. Significant associations were observed for refined grain (OR = 1.32 for an increase of one serving per day), and red meat (OR = 1.54), pork and processed meat (OR = 1.27), alcohol (OR = 1.28), and significant protections for whole grain (OR = 0.85), raw (OR = 0.85) and cooked vegetables (OR = 0.69), citrus (OR = 0.86) and other fruits (OR = 0.85), and for coffee (OR = 0.73). Garlic was also protective (OR = 0.32 for the highest tertile of intake). These findings in a central European population support the hypothesis that a diet rich in refined grains and red meat increases the risk of colorectal cancer; they, therefore, support the recommendation to substitute whole grains for refined grain, to limit meat intake, and to increase fruit and vegetable consumption.

Prospective case-cohort study of intestinal colonization with enterococci that produce extracellular superoxide and the risk for colorectal adenomas or cancer

OBJECTIVE

The aim of this study was to determine whether intestinal colonization with enterococci that produce extracellular superoxide (O2*-), a free radical implicated in the development of colorectal cancer, is associated with these lesions or their precursors.

METHODS

A prospective case-cohort study was performed by isolating enterococci from stools of consecutive patients undergoing colonoscopy who had no prior history of colonoscopy or colorectal cancer. A food frequency questionnaire was also administered to control for dietary factors known to affect the risk for these lesions.

RESULTS

Among 159 evaluable participants were 77 with no precancerous or cancerous pathology, 61 with adenomas <2 cm, 10 with adenomas > or =2 cm, and 11 with cancer. Regression analyses found no associations for those subjects with adenomas of any size or with cancer and colonization with O2*--producing enterococci, any nutrient, or age. For those patients with large adenomas > or = 2 cm or cancer, however, significant associations were noted for age (OR 1.94 per decade, 95% CI 1.2-3.5), beta-carotene (OR 0.44 per 500 microg/1000 kcal/day, 95% CI 0.2-0.8), vitamin A (OR 3.20 per 500 microg/1000 kcal/day, 95% CI 1.2-8.9), and vitamin E (OR 0.09 per 10 mg/ 1000 kcal/day, 95% CI 0.006-0.9), but not colonization with O2*--producing enterococci. Second stools collected 1 yr later, however, often contained dissimilar enterococcal flora, undermining an important study assumption.

CONCLUSIONS

Significant associations were found for those with large adenomas or cancer (but not small adenomas), with age, and with foods enriched for vitamin A, vitamin E, and beta-carotene. An association between colonization with O2*--producing enterococci and colorectal adenomas or cancer, however, could not be ascertained, possibly because intestinal enterococcal flora changes over time, leaving a potentially cohesive hypothesis of colon cancer and risk factors as yet unanswered.

Association between breast and colorectal cancers

BACKGROUND

The risk of breast and colorectal cancers in immigrants from non-industrialised countries is sharply increased when they adopt a Western lifestyle. In addition, epidemiological studies on Western populations show an association between the two tumours, both in the same individual and also in close relatives. Most studies agree that high energy intake, obesity and inadequate physical exercise are associated with an increased risk of both tumours.

METHODS

Risk markers for each cancer are examined in order to identify causative nutritional factors or metabolic-endocrine dysfunction. The role of steroid hormones and other possible carcinogenic mechanisms is discussed, concentrating on evidence of a role for insulin and insulin-like growth factors (IGFs) in the promotion of carcinogenesis in both organs.

RESULTS

Individuals with a genetic susceptibility to insulin resistance show triggering of hyperinsulinaemia following excessive weight gain or long-term diet high in saturated fat. Case-control studies show an association between hyperinsulinaemia and evidence of breast or colorectal carcinoma. Multiple laboratory studies show that increased activity of IGFs can stimulate the growth of human breast and colorectal cancer cells.

CONCLUSION

It is postulated that either insulin resistance and its concomitants promote the development of breast and colorectal cancers, or that they share common risk factors. Sex steroid metabolism and organ specificity may explain age and sex differences between the tumours in relation to the role of obesity. Recent research suggests that a diet high in n-3 polyunsaturated fatty acids may reduce the risk of developing insulin resistance. This observation may be applied to test the hypothesis that an effect on hyperinsulinaemia may modify the risk of developing breast or colorectal cancer.