The epidemiology of diet and cancer

Glucosinolate and isothiocyanate intakes are inversely associated with breast cancer risk: a case–control study in China

Although previous studies have investigated the association of cruciferous vegetable consumption with breast cancer risk, few studies focused on the association between bioactive components in cruciferous vegetables, glucosinolates (GSL) and isothiocyanates (ITC), and breast cancer risk. This study aimed to examine the association between consumption of cruciferous vegetables and breast cancer risk according to GSL and ITC contents in a Chinese population. A total of 1485 cases and 1506 controls were recruited into this case–control study from June 2007 to March 2017. Consumption of cruciferous vegetables was assessed using a validated FFQ. Dietary GSL and ITC were computed by using two food composition databases linking GSL and ITC contents in cruciferous vegetables with responses to the FFQ. The OR and 95 % CI were assessed by unconditional logistic regression after adjusting for the potential confounders. Significant inverse associations were found between consumption of cruciferous vegetables, GSL and ITC and breast cancer risk. The adjusted OR comparing the highest with the lowest quartile were 0·51 (95 % CI 0·41, 0·63) for cruciferous vegetables, 0·54 (95 % CI 0·44, 0·67) for GSL and 0·62 (95 % CI 0·50, 0·76) for ITC, respectively. These inverse associations were also observed in both premenopausal and postmenopausal women. Subgroup analysis by hormone receptor status found inverse associations between cruciferous vegetables, GSL and ITC and both hormone-receptor-positive or hormone-receptor-negative breast cancer. This study indicated that consumption of cruciferous vegetables, GSL and ITC was inversely associated with breast cancer risk among Chinese women.

Lessons learned from cancer prevention studies with nutrients and non-nutritive dietary constituents

Epidemiological studies have observed the association between dietary patterns and the risk of certain types of cancer. Extensive studies have been conducted on the cancer preventive activities of constituents from food and beverages. While laboratory research has shown impressive and promising results, such promising cancer preventive activities have not been demonstrated in many human intervention trials. This article analyzes the major differences between these different types of studies and the limitations of these studies. Animal and cell line studies usually use optimal conditions in order to demonstrate the hypothesized effects, sometimes without considering the human relevance. On the other hand, some clinical trials were designed without a good understanding of the biochemical and pharmacological properties of the agents used. Lessons learned from these studies will be illustrated using vitamin E, β-carotene and selenium as examples for nutrients, and green tea polyphenols as an example for non-nutritive dietary constituents. From the lessons learned, we believe that more interdisciplinary collaboration and integration of laboratory and human studies would effectively advance the field of cancer prevention.

Caloric restriction reduced 1, 2-dimethylhydrazine-induced aberrant crypt foci and induces the expression of Sirtuins in colonic mucosa of F344 rats

BACKGROUND

Caloric restriction (CR), a lowering of caloric intake without malnutrition, is associated with longevity. CR also decreases incidences of age-related diseases including cancer. The sirtuins (SIRTs) have been implicated as a key mediator for the beneficial effects of CR on longevity. However, the underlying mechanisms by which CR decreases cancer risk have not yet been fully elucidated.

MATERIALS AND METHODS

The present study was conducted to determine whether CR would modify the growth of preneoplastic colonic aberrant crypt foci (ACF). We also analyzed the expression of SIRTs to elucidate the molecular mechanisms of cancer-preventive effects of CR. F344 rats were fed a CR diet (60% of ad libitum diet) or a basal diet ad libitum. Then, the animals were given subcutaneous injection of either 1, 2-dimethylhydrazine (DMH) that enhances cell proliferation of colonic mucosa or saline. All animals were sacrificed at 5 weeks after the beginning of the experiment.

RESULTS

The number of ACF in colonic mucosa was significantly decreased in DMH-treated rats with CR as compared to in those without CR. No ACF was found in DMH-untreated animals with or without CR. Also, we found that CR decreased the cell proliferation of colonic mucosa in DMH-treated rats. The expressions of anti-apoptotic gene, Survivin, and cell cycle progression-associated gene, Cyclin D1, were increased by DMH-treatment. Both of the genes expressions were declined by CR in those of DMH-treated rats. The expressions of all SIRT1-7 mRNAs were significantly increased by CR in DMH-treated rats.

CONCLUSION

As previous studies demonstrated that SIRT1 down-regulates Survivin and Cyclin D1, our findings suggest that at least SIRT1 protect colonic mucosa from formation and development of ACF by increasing apoptosis and reducing excessive cell growth in colon epithelial cells.

An enhanced apoptosis and a reduced angiogenesis are associated with the inhibition of lung colonisation in animals fed an n-3 polyunsaturated fatty acid-rich diet injected with a highly metastatic murine melanoma line

Both epidemiological and experimental studies indicate that dietary n-3 PUFA inhibit carcinogenesis and tumour growth. Metastatic diffusion has also been found to be affected in animals fed diets containing purified n-3 PUFA or fish oil. In the present study, we investigated whether the metastatic diffusion of a highly metastatic variant (F10-SR cells) isolated from the B16 melanoma F10 line was affected by feeding host animals a diet containing 5 % fish oil. In these animals, compared with those fed a diet containing 5 % maize oil, there was a reduced number of metastatic pulmonary colonies. The immunohistochemical analysis of appropriate markers revealed that the antimetastatic effect of dietary n-3 PUFA was not related to a reduction of proliferation, but rather to an enhanced apoptotic activity. The reduction of von Willebrand factor immunoreactivity found in pulmonary colonies of F10-SR cells grown in fish oil-fed animals indicates that a decrease of angiogenesis contributes to the antimetastatic effect of dietary n-3 PUFA. This conclusion stands in spite of the higher expression of vascular endothelial growth factor observed in pulmonary colonies grown in fish oil-fed animals.

Antitumour promoting activity of indole-3-carbinol in mouse skin carcinogenesis

There has been growing interest in recent years in the potential of brassica vegetables (cabbage, cauliflower, brussels sprouts, etc.) as vectors for the introduction of anticarcinogenic compounds in the diet. Indole-3-carbinol, a major indole metabolite present in the cruciferous vegetables, has been found to inhibit various rodent tumours when administered prior to or during carcinogen exposure. In this study, the antitumour promoting potential of indole-3-carbinol was studied in a two-stage mouse skin model of carcinogenesis. The animals were initiated with a single subcarcinogenic dose of DMBA. After one week, 250 microg of indole-3-carbinol was applied topically to each animal prior to promotion with 5 microg TPA twice per week. Tumour development was significantly inhibited in indole-3-carbinol-supplemented animals in terms of cumulative numbers of tumours and average tumours per mouse. About 44% of male and 29% of female mice remained tumour-free in this group at the end of the experiment. A significant delay in the tumour induction time was also observed in indole-3-carbinol-supplemented animals. This evidence suggests that indole-3-carbinol, in the manner and dose given, inhibits the development of tumours in the two-stage mouse skin model of carcinogenesis.

Some lifestyle factors in human lung cancer: a case-control study of 792 lung cancer cases

In order to investigate the relationship between some lifestyle factors and lung cancer, a case-control study involving all lung cancer deaths registered in 1986 was performed. The results show that among males, 92.5% of the cases and 75.5% of controls were smokers, implying that cigarette smoking is a primary risk factor for lung cancer in males. By contrast, among females only 60.6% of the cases and 30.8% of the controls were smokers, implying factors other than cigarette smoking must be involved in the development of lung cancer in females. The risk of lung cancer in nonsmoking females was found to be unaffected by exposure to environmental tobacco smoke (ETS). A study of diet and eating habits showed that in males the risk of lung cancer was reduced by the intake of vegetables and fruits, but was significantly increased by a frequent intake of fried foods. The positive association between the intake of fried food and the risk of lung cancer could result from cooking practices and from inappropriate methods used in food preparation. No association can be demonstrated between the consumption of high protein or high fat diets, salty and smoked food items and the incidence of lung cancer. Thus, it is not likely that sufficient lung cancer inducing carcinogens can be generated through the intake of food. In addition, the positive association found to exist between the living index and the risk of lung cancer in females is consistent with the notion that coal smoke or cooking practices may generate sufficient indoor air pollutants to significantly increase the risk of lung cancer in females.

Variability of neoplastic parameters in colon tumours, and its significance in diagnostic practice

We have reviewed the value of individual variability in the reaction of tissues to treatment with carcinogens, and the manifestation of this variability in different morphological (histological, morphometric, and ultrastructural), histochemical and immunohistochemical parameters generated in tumorous tissues. Moreover, we also reviewed data in the literature on individual variability in the manifestation of some biochemical and immunochemical markers which are accumulated in the serum of tumour-bearing patients and which are characteristic for the different phases of tumourigenesis. The high variability of different tumorous parameters suggests that none can be utilized alone as a conclusive marker of neoplasia and that only their combined use can give objective information. We also reviewed the impact of this variability in the evaluation of various pathological methods to detect different stages of neoplastic transformation in the colon. It has been concluded that none of the present approaches can be absolutely conclusive and without false results, and that objective information regarding early cancerous changes may be obtained only by use of combined analyses utilizing several laboratory methods. The diagnostic procedures should be based on the complex utilization of all appropriate methods using the quantitative interpretation of the obtained data. Multivariate analysis of many parameters should be very effective for the prediction of therapeutic results.

Declining incidence is greater for esophageal than gastric cancer in Shanghai, People's Republic of China

Temporal trends in the incidence of esophageal and gastric cancers during 1972 to 1989 were addressed in urban Shanghai, the location of China's longest standing cancer registry. Over the 18 year study period, esophageal cancer rates decreased more than 50% from 28.8/100,000 person-years in 1972-74 to 13.3/100,000 in 1987-89 among men and from 11.3/100,000 to 5.4/100,000 among women. Reductions were apparent in each age group, but most pronounced among younger generations, with more than a 75% decline in incidence among those under age 55 years. The incidence rate for stomach cancer among men decreased 20% from 62.0/100,000 in 1972-74 to 50.1/100,000 in 1987-89. The reduction among women, however, was minor, from 23.9/100,000 to 23.2/100,000. The patterns varied by age, with declines among persons 45-64 years and increases among those in older and younger age groups. The determinants of these trends are not clear, but appear related in part to dietary changes.

Reverse smoking as a risk factor for palatal cancer: a cross-sectional study in rural Andhra Pradesh, India

A cross-sectional study of reverse smoking and its association with pre-malignant and malignant lesions of the palate was conducted in the north coastal areas of Andhra Pradesh, India. A total of 480 randomly selected persons were interviewed. Information about smoking status, diet and access to mass media was obtained in each case and an examination of the oral cavity was performed. Reverse smoking of chutta was practised by 33% of the total rural population. The prevalence rate of all palatal lesions was 55%. The prevalence rates of the separate lesions: leukoplakia palatii, palatal keratosis and palatal cancer, were 9.8%, 18.1% and 1.9%, respectively. The presence of these (pre-)malignant lesions was strongly associated with reverse smoking and also associated with conventional chutta smoking. Reverse smoking induced significantly more lesions than conventional chutta smoking, and was a major determinant of subsequent palatal cancer: all 9 newly diagnosed palatal cancers were observed within the group of reverse smokers. There was an inverse relationship between the incidence of palatal lesions and vitamin A intake. The study of access to mass media indicated that the most favourable medium for promoting a prevention campaign would be the cinema.

A population-based case-control study of cancers of the nasal cavity and paranasal sinuses in Shanghai

A population-based case-control study of cancer of the nasal cavity and sinuses, involving interviews of 60 incident cases and 414 controls, was conducted in Shanghai. Cigarette smoking was associated with a mild elevation in risk of squamous-cell carcinoma but not cancers of other cell types. Occupational exposures to wood and silica dusts and to petroleum products, and the use of wood and straw as cooking fuel, were linked to moderate increases in risk, while 4-fold or greater increases were associated with a history of chronic nasal diseases, including those occurring 10 or more years prior to cancer diagnosis. Dietary analyses revealed a significant protective effect of consumption of allium vegetables, oranges and tangerines, with a 50% reduced risk of nasal cancer among individuals in the highest intake group of these foods. Consumption of salt-preserved vegetables, meat and fish was associated with a significantly increased risk of nasal cancer in a dose-response fashion, with a 5-fold excess observed for the heaviest intake of these salted foods. These findings suggest that dietary factors may contribute to the development of nasal cancer.

Assessment of adherence to a low-fat diet for breast cancer prevention

BACKGROUND

The relationships between self-reported adherence to a low-fat diet in healthy women between the ages of 44 and 69 and a number of correlates of this self-reported behavior were examined in an attempt to improve monitoring of adherence to nutritional intervention trials for breast cancer prevention.

METHODS

Dietary fat intake in 87 women who completed 6 months of nutritional intervention was reduced from 38.2 +/- 5.9% to 21.7 +/- 7.8% of total energy intake (P less than 0.005). Reported total calorie intake was reduced by approximately 20%.

RESULTS

Body weight decreased by 2.7% from 68.1 +/- 11.2 kg to 66.3 +/- 11.9 kg (P less than 0.05). Fasting total plasma cholesterol levels decreased from 205 +/- 31 mg/dl to 184 +/- 29 mg/dl (P less than 0.05). Fasting plasma triglyceride levels did not change significantly (97 +/- 44 mg/dl vs 101 +/- 55 mg/dl). Relative percentage changes in body weight correlated with percentage changes in dietary fat intake (r = 0.23, P less than 0.05).

CONCLUSION

Self-reported changes in dietary behavior correlated significantly with objective changes in body weight and fasting cholesterol in these healthy women encouraged to consume a low-fat diet for prevention of breast cancer.

Alcohol and breast cancer: a review

This paper reviews the major studies on the possible relationship between drinking alcohol and breast cancer. The majority of these studies show some association between levels of alcohol consumption and breast cancer. However, the evidence of a causal link is lacking. A number of problems in interpreting the data are discussed. Given the high incidence of breast cancer in many countries, this is an important area. However, the imputed role of alcohol must not be exaggerated, particularly if this means that other more important factors in the equation fail to be examined.

Milk cream does not enhance 2,7-dimethylbenz[a]anthracene-induced mammary tumorigenesis

We have previously reported that a diet enriched with butter showed an inhibitory effect on the development of mammary tumors in mice and rats. To solve the problem of whether the inhibitory effect of butter was caused by lipids of cow's milk, we have studied the effects of dried milk (WM), skim milk (SM) and milk cream (CR) on mammary tumorigenesis in rats. The lowest incidence of mammary tumors was observed in the CR group, although the difference from other groups was statistically not significant. However, the number of papillary carcinomas in the CR group was significantly lower than the WM group. The result indicates that milk lipids have no enhancing effect on mammary tumorigenesis.

Epidemiological research in stomach cancer: progress over the last ten years

In this paper the progress of epidemiological research in stomach cancer during 1980-1990 is reviewed in respect to regional variation, etiology, and formation of carcinogens. The evaluation of 4 cohort and 16 case-control studies revealed a consistently inverse relationship of stomach cancer risk with raw vegetables, fruit, and wholemeal bread consumption and with vitamin C and carotene intake. Milk, cooked vegetables and vitamins A and E were not consistently found to be related to stomach cancer risk. Positive associations of increasing consumption with stomach cancer risk were occasionally found for processed or particularly prepared meat and fish, and for nitrite. Dietary nitrate intake did not appear to be related to stomach cancer risk in these studies. This latter observation is also supported by metabolic studies in high- and low-risk areas for stomach cancer. Consistently among studies, increased risk for stomach cancer was also found for later availability of refrigeration facilities in the household, non-centralized water supply (especially well water), and high salt intake. Prospective studies agreed in an increased risk for stomach cancer for cigarette smoking, but not for alcohol drinking, whereas case-control studies showed divergent results on these factors. Recent metabolic studies in high- and low-risk areas for stomach cancer or in groups with precursor lesions, with the N-nitrosoproline test as a marker for endogenous nitrosation, revealed inconsistent results. Higher nitrite concentration and increased pH in stomach juice were found to be associated with precursor conditions for stomach cancer. It is still not clear whether intake of preformed carcinogens or endogenous formation in the stomach with or without the inclusion of nitrite is the most important source of tumor-initiating or -promoting substances. Preservation or preparation of meat and fish may play an important role in this process, and vitamin C may be an inhibiting substance.

Family aggregation of cancer of the prostate in Quebec: the tip of the iceberg

Cancer of the prostate is one of the most common cancers among males in North America. Although some causative factors have been suggested by several surveys, the etiology of this common cancer is poorly understood. In a case-control study of prostatic cancer in Greater Montreal, 21 of 140 patients with prostatic cancer (15.0%) gave a positive family history of the same cancer, as compared with two cases among 101 (2.0%) population-based controls. This indicates about an eightfold difference in occurrence of cancer of the prostate among first-degree family members of the case group with an odds ratio (OR) of 8.7 and 95% CI, 2.00-38.17. In this report we present the pedigrees of three families (two cases and one control) with four pathologically confirmed cases of cancer of the prostate in each family. This data suggest that a familial predisposition to prostatic cancer may become apparent in later decades of life. In these family aggregations, in addition to the genetic factors, environmental factors may also play an important role in the etiology of the same cancer among family members.

The effect of beta-carotene on the regression and progression of cervical dysplasia: a clinical experiment

In order to gain insight into the causality of the relation between beta-carotene and cancer, we performed a randomized placebo-controlled trial in which the effect of beta-carotene on the regression and progression rates of cervical dysplasia were examined. The experimental group (n = 137) received a supplemental dose of 10 mg of beta-carotene daily for 3 months. The control group (n = 141) received placebo capsules. As the outcome parameter, two definitions of regression and progression were used, which were based on the degree of dysplasia before and after the medication period. The number of patients who showed progression was too small to allow conclusions. No effect of beta-carotene on the regression percentages was observed: OR = 0.68 (95% CI: 0.28-1.60) using the broad definition; and OR = 1.22 (95% CI: 0.43-3.41) with the strict definition. A secondary analysis, in which the effect of the total intake of beta-carotene (diet + medication) on the regression percentages of cervical dysplasia was studied, did not show a positive effect either. The paper discusses to what extent issues in the study design may have masked a potential effect and how our results affect the evidence for a causal relation between beta-carotene and cancer.

Immunoregulation of natural and lymphokine-activated killer cells by selenium

The effect of selenium (Se) on natural killer (NK) and lymphokine-activated killer (LAK) cell activities and proliferative responses of human lymphocytes was studied in vitro. Direct addition of Se at 1.0 microgram/ml final concentration to the mixture of target and effector cells during a 4 h cytotoxicity assay significantly suppressed the NK activity of normal lymphocytes. When lymphocytes were preincubated with Se at concentrations as low as 0.2 microgram/ml for a period of 48 h, a significant inhibitory effect on NK activity was observed. In the LAK cell assay, direct addition of Se at concentrations of 0.2-1.0 microgram/ml to a mixture of target and effector cells did not show any effects on LAK cell activity, whereas LAK cells generated in the presence of Se at 0.8 microgram/ml showed significant inhibition of their functions. Lymphocyte proliferative responses to T cell mitogens such as phytohemagglutinin (PHA) and concanavalin A (Con A) were also significantly suppressed by direct addition of Se at 0.5-1.0 microgram/ml. The inhibitory effect of Se was not due to nonspecific toxicity of effector cells as demonstrated by viability nor was the effect directed against target cells. These studies suggest that although Se is an essential micronutrient for various immune mechanisms, an excess of Se may have a deleterious effect on certain immunological functions. As these activities are considered to be important defense mechanisms against tumors and virus infections, a nutritional imbalance of Se could result in an increased risk of these disorders.

A case-control study of male colorectal cancer in Aichi Prefecture, Japan: with special reference to occupational activity level, drinking habits and family history

The relationships of occupational activity level, drinking habits and family history of cancer to the risk of male colorectal cancer by subsites were investigated in a case-control study involving 1,716 cases with colon cancer, 1,611 cases with rectal cancer and 16,600 controls with other sites of cancer identified from the Aichi Cancer Registry, Japan 1979-1987. An occupation with a low activity level was associated with an increased risk of colorectal cancer; the age-adjusted relative risk (RR) compared to the high activity level group was 1.92 (95% confidence interval (CI): 1.38-2.67) for proximal colon cancer, 1.52 (95% CI: 1.19-1.94) for distal colon cancer and 1.38 (95% CI: 1.17-1.62) for rectal cancer. Beer drinkers showed an increased risk of colorectal cancer; the age-adjusted RR was 1.49 (95% CI: 1.13-1.95) for proximal colon cancer, 1.65 (95% CI: 1.34-2.04) for distal colon cancer and 1.88 (95% CI: 1.62-2.18) for rectal cancer. The RR for family history of colorectal cancer was 3.40 (95% CI: 2.19-5.29) for proximal colon cancer, 2.54 (95% CI: 1.73-3.75) for distal colon cancer and 1.78 (95% CI: 1.28-2.49) for rectal cancer. Multivariate analysis controlled for age, residence, marital status and smoking in addition to occupational activity level, beer drinking and family history of colorectal cancer did not materially change the RRs. When these three variables were combined, the RR was 15.72 (95% CI: 5.40-45.78) for proximal colon cancer, 10.55 (95% CI: 4.24-26.27) for distal colon cancer and 6.69 (95% CI: 3.12-14.36) for rectal cancer.

Case-control study on occupational exposure to diesel exhaust and lung cancer risk

The association between lung cancer and occupations with probable exposure to diesel exhaust (DE) was studied among 2,584 cases and 5,099 hospital controls. The crude odds ratio (OR) for probable exposure was 1.31 (95% confidence interval [CI] 1.09-1.57), but adjustment for smoking and other confounders reduced the estimate to 0.95 (95% CI = 0.78-1.16). Similar results were observed for truck drivers, the only occupational category large enough for separate analysis. Data on self-reported exposure for 477 cases and 946 controls revealed a crude OR of 1.45 (95% CI = 0.93-2.27), which was reduced to 1.21 (95% CI = 0.78-2.02) after controlling for smoking and other confounders. The present results and a review of the literature do not definitively support an etiologic association between DE exposure and elevated lung cancer risk.

Causes of cancer--an alternative view to Doll and Peto (1981)

This paper presents an alternative view to a commonly held misconception. The extent to which the causes of human cancer can be known is less than generally believed on the basis of the formal summation of estimates on the causal role of certain carcinogenic factors that have been tabulated by Doll and Peto (1981). Here it is stressed that the factors with known causal relation in the etiology have not as yet been ascertained for up to 97% of human cancers. Currently only one-third of the cancer deaths registered in the Federal Republic of Germany can be assigned etiologically to known exogenous carcinogenic agents or lifestyle. Accordingly, the causes of less than 50% of all malignant neoplasms are known and amenable to direct causal primary prevention. This, however, does not preclude a concept of "indirect primary prevention" which, based on the probable summation of subcarcinogenic effects of single carcinogens, enables removal from the environment of compounds that show carcinogenicity in animals, even if these compounds lack epidemiological evidence of carcinogenic activity.

Inhibition of DMBA-induced mammary tumorigenesis by caloric restriction in rats fed high-fat diets

Most previous studies on the inhibiting effect of caloric restriction during promotion of DMBA-induced mammary carcinogenesis have used low to moderate levels of dietary fat, i.e., about 4 to 14% by weight. The current study was designed to test whether a moderate degree of caloric restriction, 25%, would inhibit tumor growth in rats fed the equivalent of 20% dietary fat which approximates human consumption in affluent countries. Rats were fed diets ad libitum that contained 5, 15 or 20% corn oil. Groups of rats were pair-fed to the last 2 groups, but subjected to a 25% caloric restriction. These groups were fed 20 or 26.7% corn oil so that absolute fat intake in the paired groups was identical. Significant inhibition of tumor incidence, tumor weight, tumor burden, body fat deposition, and fasting serum insulin were observed in the 2 calorically restricted groups. We conclude that moderate caloric restriction is significantly more effective in inhibiting tumor growth than is the promoting effect of diets high in fat. Total body weight, body fat and serum insulin concentrations may be better correlates of risk of developing mammary tumors than is dietary fat.

Premalignant alterations in rat colonic N1-acetylspermidine levels induced by 1,2-dimethylhydrazine: effects of a high corn oil dietary regimen

Recently, our laboratory has demonstrated that elevations in the levels of N1-acetylspermidine could be detected in the colonic mucosa of rats after administration of 1,2-dimethylhydrazine for 15 weeks, i.e., before the development of colon tumors. Since prior studies have indicated that diets high in fat, particularly unsaturated fat, promote the development of dimethylhydrazine-induced tumors, it was of interest to examine the effect of a corn oil dietary regimen (20% by weight) on colonic N1-acetylspermidine levels in this model of colonic adenocarcinoma. Four groups of rats were used in these studies: chow, chow + carcinogen, corn oil and corn oil + carcinogen. The carcinogen groups received weekly s.c. injections of 1,2-dimethylhydrazine (20 mg/kg body wt) for 15 weeks, while the control groups received diluent. 1 week after the last injection, animals from each group were killed, and their proximal and distal colons were resected, examined and compared with respect to polyamine levels, including N1-acetylspermidine, as well as the activities of ornithine decarboxylase, spermidine N1-acetyltransferase, and polyamine oxidase. In view of previous studies which suggested that N1-acetylspermidine levels may be elevated in the urine of patients with various malignancies, it was also of interest to examine and compare the urinary levels of this acetylated polyamine in animals from each group. The results of these experiments demonstrated that: (1) the levels of N1-acetylspermidine in the distal colonic segment were found to be increased approx. 25 and 80% in the chow + carcinogen and corn oil + carcinogen groups, respectively, compared to their control counterparts; (2) the activities of spermidine N1-acetyltransferase in the distal colonic segments of chow + carcinogen and corn oil + carcinogen animals were increased 1.5- and 2-fold, respectively, compared to control values; (3) dimethylhydrazine administration did not affect the levels of this acetylated polyamine or spermidine N1-acetyltransferase activities in the proximal colon, but, in general, did increase the levels of putrescine and spermidine as well as ornithine decarboxylase activities in both colonic segments of animals fed chow or corn oil diets; and (4) elevated urinary levels of N1-acetylspermidine did not appear to be a reliable 'premalignant' marker in this experimental model of colonic adenocarcinoma.

Diet, nutritional status, and cancer risk in American blacks

About 35% (10-70%) of all cancers may be associated with nutritional causes (1). However, while natural or added substances in foods may be carcinogenic, nutritional deficiencies or excesses may promote carcinogenesis. We compared data from blacks and whites using dietary and nutritional status surveys in the United States to determine whether the poorer dietary patterns and nutritional status of American blacks may be associated with their higher incidence and mortality from certain cancers (compared with whites). Our review indicates that blacks eat more nitrate and animal foods and not enough fiber in relation to protein, fat, and carbohydrate. Blacks also have poorer nutritional status with respect to getting enough thiamine, riboflavin, vitamins A and C, and iron, to being obese (females), and to being underweight (males). This is in agreement with hypotheses regarding the interactions between diet and cancer (associations found in whites) and dose-response relationships reported for some cancers for which blacks have a higher incidence and mortality than whites. More large-scale prospective case-control and cohort studies are needed in both blacks and whites to elucidate the contribution of specific dietary and nutritional factors to the risk of specific cancers in these population groups. However, such studies must be preceded by methodological research to obtain more valid measures of dietary and nutritional status.

Diesel exhaust exposure and lung cancer risk

The association between lung cancer and occupations with probable exposure to diesel exhaust has been examined in several studies in the past with inconclusive results. We report a case-control study among 2,584 cases and 5,099 hospital controls. The crude odds ratio for probable exposure was 1.31 (95% Cl 1.09, 1.57), but adjustment for smoking and other confounders reduced the estimate to 0.95 (95% Cl 0.78, 1.16). Similar results were observed for truck drivers, the only occupational category large enough for separate analysis. Data on self-reported exposure for a subset of 477 cases and 946 controls revealed a crude odds ratio of 1.45 (95% Cl 0.93, 2.27) which was reduced to 1.21 (95% Cl 0.78, 2.02) after controlling for smoking and other confounders. A duration-response relationship was suggested (P less than 0.12) only for self-reported exposure. Cigarette smoking was the predominant confounder in the analysis. Problems arising from biases and confounding in the present and in other previously published reports on the association between diesel exhaust exposure and lung cancer risk are discussed, and a review on the evidence of human carcinogenicity of diesel exhaust exposure is presented.

Colorectal adenomas and food. A prospective study of change in volume and total mass of adenomas in man

In an endoscopic population screening study for detection of colorectal polyps the diet was registered before ascertaining whether polyps were present. Polyps less than 5 mm in diameter were followed up for 2 years before removal and histologic diagnosis. The relative risk of an increase both in the volume of registered adenomas (excluding new adenomas) and in the total mass of adenomas (including new adenomas) showed a trend towards an inverse relationship with intake of dietary fiber, non-fiber carbohydrate, and cruciferous vegetables, reaching the significance level only for intake of dietary fiber for increase of adenoma volume in men. A trend towards a positive relationship between growth and total fat intake was more inconsistent, although the significance level was reached for the relative risk of increase in adenoma mass for men. These prospective observations with regard to polyp-bearing individuals agree with previous incidence and prevalence data that have indicated a relationship between dietary habits and colorectal carcinogenesis.

Diet and cancer. Any progress in the interim?

It has been 5 years since the National Research Council (NRC) Committee on Diet, Nutrition and Cancer published "Interim Dietary Guidelines" for the nutritional prevention of cancer. The term "interim" implies that these recommendations should be regarded as temporary, pending more definitive findings from additional scientific research. This article reviews findings relevant to the connections between diet and cancer that have emerged from nutritional epidemiology subsequent to the 1982 the NRC report. Some recent research has supported the earlier work which served as a basis for the interim recommendations, some has not, and additional hypotheses have emerged. There continues to be evidence, although it is inconsistent, that dietary fat may be an important factor in colon cancer, and that something related to fruits and vegetables, perhaps carotene, may lower the risk of lung cancer. However, the hypothesized relationships between dietary fat and breast cancer and between dietary fiber and colon cancer have been less consistently supported by new findings. Meanwhile, a new hypothesis has emerged relating alcohol intake to breast cancer risk, although many important questions remain regarding the age at which alcohol use may affect risk, and the dose above which risk is increased. The last 5 years seem to have been characterized by only slow progress in our understanding of the relationship between diet and cancer. It is clear that in 1988 we are still very much in the interim. Critical methodologic assessments of the reasons for the discrepancies in findings among the various studies, and meta analytic approaches may be helpful in increasing our understanding of the set of epidemiologic research conducted to date. More important, however, are the many types of studies now underway, including more rigorously designed observational studies and chemo-preventive and dietary-preventive trials. These studies will likely provide more definitive future answers to the questions we still face in the interim.

Possibilities and limitations in cancer prevention

The possibilities and limitations in cancer prevention are shown by means of some examples and historical facts. A necessary prerequisite for effective prevention is to know the exact cause of cancer. This is known for some tumor types (e.g., bronchial cancer), while for others it is hardly known (e.g., breast cancer). There are many factors which influence the whole process of carcinogenesis. Exposure to environmental pollutants in a wide sense represents only one of many possible etiologies. This has to be taken into consideration.

Stone agers in the fast lane: chronic degenerative diseases in evolutionary perspective

From a genetic standpoint, humans living today are Stone Age hunter-gatherers displaced through time to a world that differs from that for which our genetic constitution was selected. Unlike evolutionary maladaptation, our current discordance has little effect on reproductive success; rather it acts as a potent promoter of chronic illnesses: atherosclerosis, essential hypertension, many cancers, diabetes mellitus, and obesity among others. These diseases are the results of interaction between genetically controlled biochemical processes and a myriad of biocultural influences--lifestyle factors--that include nutrition, exercise, and exposure to noxious substances. Although our genes have hardly changed, our culture has been transformed almost beyond recognition during the past 10,000 years, especially since the Industrial Revolution. There is increasing evidence that the resulting mismatch fosters "diseases of civilization" that together cause 75 percent of all deaths in Western nations, but that are rare among persons whose lifeways reflect those of our preagricultural ancestors.

Murine antiestrogen-binding protein: characterization, solubilization and modulation by lipids

The properties of the antiestrogen-binding protein have been examined in mouse tissues, a species in which nonsteroidal antiestrogens are virtually pure agonists. As in other species studied, this protein was distributed in all tissues - highest levels being in the liver. Subcellular fractionation of mouse liver showed that 82% of the antiestrogen-binding protein was associated with the rough endoplasmic reticulum where it was confined to the membranous component. The antiestrogen-binding protein was also present in smooth endoplasmic reticulum, nuclei and cytosol. Its concentration in intact nuclei was at least 10-times higher than levels previously reported in intact rat liver nuclei. Binding of [3H]tamoxifen to the murine antiestrogen-binding protein was of high affinity (Kd = 1 nM) and was inhibited by unsaturated fatty acids and 7-ketocholesterol. In general, cis-isomers of unsaturated fatty acids were more effective binding inhibitors than trans-isomers. The antiestrogen-binding protein solubilized from rough endoplasmic reticulum membranes by the zwitterionic detergent CHAPS, had a molecular mass of approx. 700 kDa and a sedimentation coefficient of about 19 S. [3H]Tamoxifen binding capacity of the solubilized protein was abolished by trypsin and nonspecific proteinases but not by clostripain or Staphylococcus aureus V8 proteinase, suggesting that lysine residue(s) may be involved in [3H]tamoxifen binding.

Familial colon cancer in the Tel-Aviv area and the influence of ethnic origin

The family history of colon cancer was investigated in 38,823 individuals (2,129 families) who comprised a control and an oncology patient series from Tel-Aviv and nearby areas. A significant increased risk for colon cancer was observed among first-degree relatives of colon cancer patients when compared to controls. When the patient sample was divided into two groups based on country and continent of birth--European (Ashkenazim) and other (nonAshkenazim)--the relatives of the nonAshkenazi subjects showed a greater relative risk for colon cancer (P less than 0.05). Colon cancer was found to be less frequent in nonAshkenazim than in Ashkenazim controls. These findings suggest that although the colon cancer frequency in the nonAshkenazi group is lower, the genetic component may be more important than for the Ashkenazi sample. The nonAshkenazi Jews may represent distinct subgroups that differ with respect to either primary genetic susceptibility to colorectal cancer and/or they may have been subjected to peculiar, environmental carcinogenic exposures when compared to their Ashkenazim brethren.

Gastric cancer in San Marinese and their first degree relatives in San Marino and the United States. Gastroscopic biopsy as an epidemiological tool

The Republic of San Marino, a small, 23-square mile, independent country near the Adriatic Coast within Italy, has been noted to have a high incidence of gastric cancer in its 22,000 population (9% of all deaths from 1969-1983 with 33% of all cancer deaths attributed to gastric cancer). Gastroscopic biopsy studies on 284 first degree relatives of San Marinese gastric cancer patients in the Republic of San Marino and in Detroit, where 2,000-2,500 San Marinese reside, have allowed detection of six gastric malignancies. Intestinal metaplasia of gastric mucosa was found in 16 (52%) of 31 Detroit first degree relatives and 51 (36%) of 143 San Marino first degree relatives. Gastroscopy provides an important tool not only for the early detection of gastric cancer in populations of high risk (such as that of San Marino), but also for providing clues to the genetic and environmental factors in gastric neoplasia.

Differential induction of mixed-function oxidase (MFO) activity in rat liver and intestine by diets containing processed cabbage: correlation with cabbage levels of glucosinolates and glucosinolate hydrolysis products

Both white and Savoy-type cabbage added to a semi-purified diet at 25% dry weight and fed to rats ad lib. for 5 days significantly induced ethoxyresorufin (ERR) deethylation in the small and large intestine. Savoy cabbage also induced hepatic activity and, in general, exhibited a greater inducing effect than white cabbage. These enzyme-inducing effects were altered when the cabbage had been processed. The content of intact glucosinolate was greater in Savoy than in white cabbage. The indole glucosinolate (glucobrassicin) content of both types of cabbage was approximately halved by cooking but was unaffected by fermentation, whilst homogenization of Savoy cabbage led to the total disappearance of intact glucosinolates. Levels of the indole glucosinolate breakdown products ascorbigen and indole-3-carbinol were highest in homogenized cabbage, and ascorbigen levels were also higher in cooked than in fresh cabbage of either type. When added to the semi-purified diet and fed ad lib. to rats for 5 days, indole-3-carbinol was a potent inducer of hepatic ERR deethylation and cytochrome P-450 activity, but had much less effect in the intestine. Other glucobrassicin metabolites, diindolylmethane and indole-3-acetonitrile, also had some inducing effect in the liver but no effect in the intestine, while ascorbigen significantly induced ERR deethylation in the small and large intestine but had no effect on hepatic MFO activity.

The role of micronutrient deficiency in carcinogenesis

Nutritional deficiencies are suspected to be contributing factors to several types of human cancers. Studies with laboratory animals have demonstrated that deficiencies in certain nutrients can enhance chemically induced carcinogenesis. In this review, we discuss several possible mechanisms for the involvement of nutritional deficiencies in carcinogenic processes, and note that different severities of deficiency may have varied effects on these processes. The relationship between results from studies with animals and the genesis of human cancer is discussed, and the application of the concept of nutrient density in relating experimental animal diets to human dietary conditions is emphasized. We also discuss in detail several recent studies that potentially may have a great impact on the prevention of human cancer. These include (1) the possible involvement of micronutrient deficiencies in carcinogenesis of the esophagus; (2) the effects of choline/methionine deprivation and calcium supplementation on liver carcinogenesis; and (3) the roles of low-calcium and high-fat intake on development of colon cancer. The possible mechanistic link between teratogenesis and carcinogenic processes is noted.

The influence of different levels of dietary fat on the incidence and growth of MNU-induced mammary carcinoma in rats

This study describes the influence of isocalorically fed diets (containing different amounts of fat) on tumor incidence and parameters of fat metabolism in female Sprague-Dawley rats. Comparisons are made between rats induced with methylnitrosourea (25 mg/kg body wt) and untreated controls (Group I). The animals received either control diets (3.9% fat by weight, Groups I and II) or fat-enriched diets (10.7%, Group III; 15.6%, Group IV; 21.4%, Group V) over a period of 180 days. At the termination of the experiment, intake of the diet containing 10.7% fat by weight (24% fat per total calories) was associated with the highest tumor incidence. Comparing the different diets, liver lipid concentrations in the individual groups increased with increasing dietary fat, whereas the total lipid in plasma decreased. During the feeding period, total lipid of the liver and plasma, and plasma cholesterol, increased in all groups, but triglycerides of plasma decreased. However, when plasma cholesterol and triglycerides were calculated as a relative amount of total lipid in plasma, cholesterol was found to be significantly decreased in Groups III and IV, and triglycerides were increased in Group III but decreased significantly in Groups I, II, and V at the end of the experiment.

Diet, nutrition, and cancer. The role of fiber

The mechanisms by which dietary fiber could inhibit development of colon cancer include effects on fecal weight and transit time, adsorption of bile acids, dilution of colonic contents, production of short chain fatty acids (products of fiber fermentation), inhibition of dehydroxylation of bile acids, and regulation of energy intake. Review of the literature suggests that effects on fecal weight and transit time and adsorption of bile acids are not likely mechanisms. Since concentration of bile acids is lower in feces of less susceptible populations, dilution of colonic contents may contribute to fiber effects. High colonic pH is associated with promotion of cancer and production of short chain fatty acids would counteract this effect. Animals maintained on calorie-restricted diets exhibit fewer spontaneous or experimentally induced tumors. Regulation of energy intake by fiber may contribute towards reduction of colon cancer incidence in man especially when caloric content is low from infancy.

Fat and cancer

Experimental studies and epidemiologic data both indicate that high-fat diets increase the risk of cancer at sites such as breast, colon, and pancreas. Dietary polyunsaturated vegetable oils promote tumorigenesis in animals whereas saturated fats and polyunsaturated fish oils either have little effect or are inhibitory. A blend of fats typical of the American diet enhanced mammary tumorigenesis effectively when fed as 40% of calories. After 9 to 10 weeks on this diet, reducing the fat to 10% of calories inhibited subsequent tumor development. Although dietary fat appears to act as a promoter, the exact mechanisms are still unknown. Cancer mortality in humans correlates better with total dietary fat than with degree of unsaturation, perhaps because most diets contain more than the amount of polyunsaturated fatty acids required for maximum effect on tumorigenesis in animals. A reduction in total dietary fat is recommended to reduce the current high cancer mortality.

The role of diet and nutrition in cancer

Experimental and epidemiologic studies in recent years are pointing to diet as an important contributor to the cancer death toll which in the US this year will reach nearly one half million. Obesity, high fat intake, low fiber content and a dearth of vitamin A- and C-containing fruits and vegetables have been identified as risk factors; but these are not independent variables. The complex network of metabolic mechanisms involved are still obscure and association is not necessarily causation. Experts may agree on the data, but differ on whether we know enough to recommend dietary changes to the public. The Society in its continued efforts toward cancer prevention, has taken the stand that the available evidence, although inferential, is sufficiently solid to share with the public, and its guidelines are compatible with currently acceptable good nutritional practice. This conference should be a landmark of progress in the Society's continuing surveillance of this active field of investigation.

Unsaturated fatty acids as endogenous inhibitors of tamoxifen binding to anti-oestrogen-binding sites

It is known that triphenylethylene anti-oestrogens such as tamoxifen bind to specific high-affinity anti-oestrogen-binding sites, which are distinct from oestrogen receptors. These binding sites are widely distributed in human and animal tissues, but their function and endogenous ligands are unknown. By using [3H]tamoxifen and a rat liver microsomal fraction, a radio-ligand-binding assay was developed in an attempt to identify endogenous ligands for the anti-oestrogen-binding sites in the rat. An ether extract of rat serum inhibited [3H]tamoxifen binding to rat liver binding sites in a dose-dependent manner. Identification of the active serum constituents that inhibited [3H]tamoxifen binding was achieved by g.l.c.-mass spectrometry after preliminary purification of a rat serum extract by silica-gel t.l.c. Three unsaturated fatty acids (oleic, linoleic and arachidonic) accounted for about 50% of the total inhibiting activity of the serum extract. The concentrations of these fatty acids required to inhibit [3H]tamoxifen binding were in the range of 10-100 microM, comparable with those found in the rat circulation under physiological conditions. Saturated fatty acids present in rat serum (palmitic and stearic) did not inhibit [3H]tamoxifen binding. A survey of other fatty acids revealed that, in general, unsaturated fatty acids were far more potent than saturated fatty acids in inhibiting [3H]tamoxifen binding. These studies demonstrate that unsaturated fatty acids are quantitatively the most important circulating inhibitors of [3H]tamoxifen binding to the anti-oestrogen-binding sites. The biological significance of their interaction with these sites, however, remains to be clarified.

Familial heterogeneity of colon cancer risk

The authors have assembled detailed family histories of cancer on 857 cancer probands, of whom 180 manifested colorectal carcinoma. This study determines if some families had a greater risk for colorectal cancer than others, and if so, what factors were associated with an increase in risk. To test for the possibility of heterogeneity of risk, a parameter called the Z-score, was calculated for each family. The Z-score is a measure of the number of cancer cases in the family adjusted for the number of expected cases. A permutation test was employed to test whether or not the variance of Z-scores from the sample was greater then expected by random chance. The variance for families ascertained through colon cancer probands, but not in any of the other groups, was significantly increased. Of the colon group, 10.6% fell into a high-risk category, as did 5.56% of the rectal cancer families, but only 3.95% of the other groups combined were at high risk. Anatomic sites (in the proband) with the highest Z-score variances were sigmoid and transverse colon, whereas lower variances were seen for cecum and descending colon. Risk status therefore may be partially dependent upon exact anatomic sites within the colon. The effect of proband's age of diagnosis was not significant, but did show the possibility of an effect on heterogeneity of risk for both the younger and older groups.

Nutrition, cancer, and aging: an annotated review. I. Diet, carcinogenesis, and aging

The interrelationships of diet and carcinogenesis are discussed with the focus on aging. To establish whether the elderly are more susceptible to dietary carcinogens and whether dietary prevention of cancer is a reasonable goal for this population, the mechanisms of chemical carcinogenesis, the age-related metabolic and physiologic changes, and the current cancer preventive dietary strategies are reviewed. Vulnerability to dietary carcinogens results from a combination of factors that may increase or decrease the occurrence of cancer in the elderly, and it is, therefore, a very individualized feature, unpredictable when based solely on a subject's age. Dietary prevention of cancer may be effective in advanced age, and the dietary guidelines of the National Academy of Sciences should be implemented in this population.

Dietary fiber and human cancer: critique of the literature

The relationship between dietary fiber consumption and risk of gastrointestinal cancer in humans is examined using representative studies of several types: international and intranational correlations, case-control analyses, metabolic investigations, cohort studies, and migrant studies. The strongest statistical association between diet and cancer is found in international studies in which numerous environmental variables differ. Studies on smaller groups within a single culture have not given strong support to the findings of international comparisons. Colon cancer rates within regions of the U.S. and other countries vary with sufficient magnitude that diet is unlikely to account for more than a minor proportion of risk. The evidence that a diet containing fiber-rich foods reduces risk of colon cancer must be considered tentative. Foods high in starch and fiber are statistically associated with a high rate of stomach cancer. Examination of the combined rates of colon and gastric cancer shows that the U.S. risk is low relative to countries in which a diet higher in fiber is consumed. It would be premature to suggest that a high fiber diet will confer protection against gastrointestinal cancer.

Role of fat, fiber, nitrate, and food additives in carcinogenesis: a critical evaluation and recommendations

This review presents a critical, select evaluation of the amount and type of fat or fiber in nutritional carcinogenesis, with the emphasis being on cancer development in the mammary gland and large bowel. The role of nitrate and nitrosation is described in relation to risk for cancers of the head and neck (especially the esophagus) and cancers of the stomach and the liver. Systematic tests of increasing complexity to delineate possible carcinogenic risk in food additives and contaminants are described. Specific recommendations stemming from these evaluations are made as to dietary recommendations designed to reduce cancer risk.