Showing papers by "International Agency for Research on Cancer published in 1997"

Poly(ADP-ribose) polymerase gene disruption renders mice resistant to cerebral ischemia

Abstract: Nitric oxide (NO) and peroxynitrite, formed from NO and superoxide anion, have been implicated as mediators of neuronal damage following focal ischemia, but their molecular targets have not been defined. One candidate pathway is DNA damage leading to activation of the nuclear enzyme, poly(ADP-ribose) polymerase (PARP), which catalyzes attachment of ADP ribose units from NAD to nuclear proteins following DNA damage. Excessive activation of PARP can deplete NAD and ATP, which is consumed in regeneration of NAD, leading to cell death by energy depletion. We show that genetic disruption of PARP provides profound protection against glutamate-NO-mediated ischemic insults in vitro and major decreases in infarct volume after reversible middle cerebral artery occlusion. These results provide compelling evidence for a primary involvement of PARP activation in neuronal damage following focal ischemia and suggest that therapies designed towards inhibiting PARP may provide benefit in the treatment of cerebrovascular disease.

Cancer risk from occupational and environmental exposure to polycyclic aromatic hydrocarbons

Abstract: Epidemiologic evidence on the relationship between polycyclic aromatic hydrocarbons (PAH) and cancer is reviewed. High occupational exposure to PAHs occurs in several industries and occupations. Covered here are aluminum production, coal gasification, coke production, iron and steel foundries, tar distillation, shale oil extraction, wood impregnation, roofing, road paving, carbon black production, carbon electrode production, chimney sweeping, and calcium carbide production. In addition, workers exposed to diesel engine exhaust in the transport industry and in related occupations are exposed to PAHs and nitro-PAHs. Heavy exposure to PAHs entails a substantial risk of lung, skin, and bladder cancer, which is not likely to be due to other carcinogenic exposures present in the same industries. The lung seems to be the major target organ of PAH carcinogenicity and increased risk is present in most of the industries and occupations listed above. An increased risk of skin cancer follows high dermal exposure. An increase in bladder cancer risk is found mainly in industries with high exposure to PAHs from coal tars and pitches. Increased risks have been reported for other organs, namely the larynx and the kidney; the available evidence, however, is inconclusive. The results of studies addressing environmental PAH exposure are consistent with these conclusions.

The EPIC Project: rationale and study design. European Prospective Investigation into Cancer and Nutrition.

Abstract: Background The most consistent result of epidemiological studies on diet and cancer is that a diet rich in vegetables, fruit and, more generally, in plant foods is associated with a reduced risk of cancer at several anatomical sites. Epidemiological studies have been less consistent regarding the putative increase in risk related to consumption of fat or meat. In addition it has not been possible to identify clearly the biological role of specific nutrients or non-nutrient food components in the prevention or causation of cancer. Limitations in the precision and validity of traditional dietary intake measurements and limited use of biomarkers combined with narrow ranges of variations in dietary habits within single populations, have been the main reasons for the limited success in identifying more specific diet and cancer links. Methods EPIC is a multi-centre prospective cohort study designed to investigate the relation between diet, nutritional and metabolic characteristics, various lifestyle factors and the risk of cancer. The study is based in 22 collaborating centres in nine European countries and includes populations characterized by large variations in dietary habits and cancer risk. Data are collected on diet, physical activity, sexual maturation and reproductive history, lifetime consumption of alcohol and tobacco, previous and current illnesses and current medication. Following a common protocol and using identical equipment, blood samples are collected, aliquoted into plasma, serum, white blood cells and erythrocytes, and stored in liquid nitrogen at -196 degrees C for future laboratory analyses on cancer cases and matched healthy controls. Anthropometric measurements are taken according to a standard protocol. It is planned to include around 400,000 middle-aged men and women. Results and conclusions The collection of questionnaire data, anthropometric measurements and blood samples is under way. Almost 340,000 subjects had been included in the study by mid-1996, and recruitment is expected to be almost complete by 1997. Follow-up for cancer incidence and total mortality has started and it is expected that about 23000 cancer cases will be identified during the first 10 years of follow-up.

The EPIC Project: Rationale and study design

Abstract: Background. The most consistent result of epidemiological studies on diet and cancer is that a diet rich in vegetables, fruit and, more generally, in plant foods is associated with a reduced risk of cancer at several anatomical sites. Epidemiological studies have been less consistent regarding the putative increase in risk related to consumption of fat or meat. In addition it has not been possible to identify clearly the biological role of specific nutrients or non-nutrient food components in the prevention or causation of cancer. Limitations in the precision and validity of traditional dietary intake measurements and limited use of biomarkers combined with narrow ranges of variations in dietary habits within single populations, have been the main reasons for the limited success in identifying more specific diet and cancer links. Methods. EPIC is a multi-centre prospective cohort study designed to investigate the relation between diet, nutritional and metabolic characteristics, various lifestyle factors and the risk of cancer. The study is based in 22 collaborating centres in nine European countries and includes populations characterized by large variations in dietary habits and cancer risk. Data are collected on diet, physical activity, sexual maturation and reproductive history, lifetime consumption of alcohol and tobacco, previous and current illnesses and current medication. Following a common protocol and using identical equipment, blood samples are collected, aliquoted into plasma, serum, white blood cells and erythrocytes, and stored in liquid nitrogen at -196°C for future laboratory analyses on cancer cases and matched healthy controls. Anthropometric measurements are taken according to a standard protocol. It is planned to include around 400 000 middle-aged ten and women. Results and conclusions. The collection of questionnaire data, anthropometric measurements and blood samples is under way. Almost 340 000 subjects had been included in the study by lid-1996, and recruitment is expected to be almost complete by 1997. Follow-up for cancer incidence and total mortality has started and it is expected that about 23 000 cancer cases will be identified during the first 10 years of follow-up.

Tumors associated with p53 germline mutations: a synopsis of 91 families.

Abstract: Although inherited p53 mutations are present in all somatic cells, malignant transformation is limited to certain organs and target cells. The analysis of 475 tumors in 91 families with p53 germline mutations reported since 1990 shows that breast carcinomas are most frequent (24.0%), followed by bone sarcomas (12.6%), brain tumors (12.0%), and soft tissue sarcomas (11.6%). The sporadic counterparts of these tumors also carry a high incidence of p53 mutations, suggesting that in these tissues p53 mutations are capable of initiating the process of malignant transformation. Hematological neoplasms (acute lymphoblastic leukemia and Hodgkin's lymphoma) and adrenocortical carcinomas occurred at a frequency of 4.2 and 3.6%, respectively. One-half of the families fulfilled the diagnostic criteria of the Li-Fraumeni syndrome. There were marked organ-specific differences in the mean age at which carriers of p53 germline mutations present with neoplastic disease: 5 years for adrenocortical carcinomas, 16 years for sarcomas, 25 years for brain tumors, 37 years for breast cancer, and almost 50 years for lung cancer. Analysis of the mutational spectrum showed a predominance of G:C-->A:T transitions at CpG sites, suggesting an endogenous formation, eg, by deamination of 5-methylcytosine, rather than a causation by environmental mutagenic carcinogens. The location of mutations within the p53 gene was found to be similar to that of somatic mutations in sporadic tumors. There is no evidence of an organ or target cell specificity of p53 germline mutations; the occasional familial clustering of certain tumor types is more likely to reflect the genetic background of the respective kindred or the additional influence of environmental and nongenetic host factors.

Socioeconomic differences in cancer incidence and mortality.

Abstract: This chapter summarizes accumulated data on the presence, magnitude and consistency of socioeconomic differentials in mortality and incidence of all malignant neoplasms and 24 individual types of neoplasms in 37 populations in 21 countries. More or less consistent excess risks in men in lower social strata were observed for all respiratory cancers (nose, larynx and lung) and cancers of the oral cavity and pharynx, oesophagus, stomach, and, with a number of exceptions, liver, as well as for all malignancies taken together. For women, low-class excesses were consistently encountered for cancers of the oesophagus, stomach, cervix uteri and, less consistently, liver. Men in higher social strata displayed excesses of colon and brain cancers and skin melanoma. In the two Latin American populations for which data were available, lung cancer was more frequent in higher social strata. Excesses in high female socioeconomic strata were seen in most populations for cancers of the colon, breast and ovary and for skin melanoma. Longitudinal data from England and Wales suggested widening over time of social class differences in men for all cancers combined and for cancers of the lung, larynx and stomach, and in women for all cancers combined and for cervical cancer.

Database of p53 gene somatic mutations in human tumors and cell lines: updated compilation and future prospects

Abstract: In recent years, there has been an exponential increase in the number of p53 mutations identified in human cancers. The p53 mutation database consists of a list of point mutations in thep53 gene of human tumors and cell lines, compiled from the published literature and made available through electronic media. The database is now maintained at the International Agency for Research on Cancer (IARC) and is updated twice a year. The current version contains records on 5091 published mutations and is expected to surpass the 6000 mark in the January 1997 release. The database is available in various formats through the European Bioinformatics Institute (EBI) ftp server at: ftp://ftp.ebi.ac.uk/pub/databases/p53/ or by request from IARC (p53database@iarc.fr) and will be searchable through the SRS system in the near future. This report provides a description of the criteria for inclusion of data and of the current formats, a summary of the relevance ofp53 mutation analysis to clinical and biological questions, and a brief discussion of the prospects for future developments.

Cancer Mortality in Workers Exposed to Phenoxy Herbicides, Chlorophenols, and Dioxins An Expanded and Updated International Cohort Study

Abstract: The authors examined cancer mortality in a historical cohort study of 21,863 male and female workers in 36 cohorts exposed to phenoxy herbicides, chlorophenols, and dioxins in 12 countries. Subjects in this updated and expanded multinational study coordinated by the International Agency for Research on Cancer were followed from 1939 to 1992. Exposure was reconstructed using job records, company exposure questionnaires, and serum and adipose tissue dioxin levels. Among workers exposed to phenoxy herbicides contaminated with 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) or higher chlorinated dioxins, mortality from soft-tissue sarcoma (6 deaths; standardized mortality ratio (SMR) = 2.03, 95% confidence interval (CI) 0.75-4.43) was higher than expected from national mortality rates. Mortality from all malignant neoplasms (710 deaths; SMR = 1.12, 95% CI 1.04-1.21), non-Hodgkin's lymphoma (24 deaths; SMR = 1.39, 95% CI 0.89-2.06), and lung cancer (225 deaths; SMR = 1.12, 95% CI 0.98-1.28) was slightly elevated. Risks for all neoplasms, for sarcomas, and for lymphomas increased with time since first exposure. In workers exposed to phenoxy herbicides with minimal or no contamination by TCDD and higher chlorinated dioxins, mortality from all neoplasms (398 deaths; SMR = 0.96, 95% CI 0.87-1.06), non-Hodgkin's lymphoma (9 deaths; SMR = 1.00), and lung cancer (148 deaths; SMR = 1.03) was similar to that expected, and mortality from soft-tissue sarcoma was slightly elevated (2 deaths; SMR = 1.35). In a Poisson regression analysis, workers exposed to TCDD or higher chlorinated dioxins had an increased risk for all neoplasms (rate ratio = 1.29, 95% CI 0.94-1.76) compared with workers from the same cohort exposed to phenoxy herbicides and chlorophenols but with minimal or no exposure to TCDD and higher chlorinated dioxins. These findings indicate that exposure to herbicides contaminated with TCDD and higher chlorinated dioxins may be associated with a small increase in overall cancer risk and in risk for specific cancers.

Tobacco smoking and gastric cancer: Review and meta-analysis

Abstract: Although declining, gastric cancer (GC) is estimated to be second in frequency worldwide. Major causes appear to be environmental rather than genetic. A relationship has been suggested between tobacco smoking and GC. A number of epidemiological studies have been performed dealing with this question. All the cohort studies showed a significantly increased risk of GC of the order of 1.5-2.5 for cigarette smokers. Evidence from case-control studies is less consistent. We have carried out a meta-analysis on the 40 studies providing a quantitative estimate of the association between GC risk and tobacco smoking. Results suggest a risk of stomach cancer among smokers of the order of 1.5-1.6 as compared to non-smokers. The summary relative risk was higher in men (1.59) than in women (1.11). Several studies examined the dose-response relationship which existed in 4 cohort studies and 6 case-control studies. We estimated the number of GC cases attributable to tobacco smoking occurring worldwide: in total, over 80,000 cases of GC (11% of all estimated cases) may be attributed to tobacco smoking each year. This figure is larger than that estimated for other cancers for which association with tobacco smoking is clearly established, such as pancreatic and renal cancers.

Hepatocellular Carcinoma: From Gene to Public Health

Abstract: Liver diseases associated with chronic hepatitis B virus (HBV) infection, including hepatocellular carcinoma, account for more than 1 million deaths annually worldwide. In addition to HBV infection, other risk factors are involved in the etiology of hepatocellular carcinoma and, among these, dietary exposure to the carcinogenic aflatoxins is of particular importance in certain regions of southeast Asia and sub-Saharan Africa. The relative contributions of these two risk factors and the mechanism of the interaction between them in the pathogenesis of hepatocellular carcinoma are still poorly understood. The recently developed individual biochemical and molecular markers of aflatoxin exposure, i.e., aflatoxin-albumin adducts in blood and a specific GC to TA transversion mutation in codon 249 of the p53 gene (249 ser p53 mutation) in hepatocellular carcinomas, permit a better quantitative estimation of aflatoxin exposure in different populations of the world. A comprehensive summary of the data from our laboratory and the literature, based on a large number (>1000) of individual cases of hepatocellular carcinoma, is presented here and shows the following: 1) A high level and high prevalence of exposure to aflatoxins occur in West Africa, Mozambique, and some regions of China; 2) a high prevalence of the 249 ser p53 mutation is detected in these countries; and 3) hepatocellular carcinomas from countries with low or no exposure to aflatoxins show a very low prevalence of the 249 ser p53 mutation and distinctly different p53 mutation spectra, probably indicating different etiologies. Experimental and epidemiologic studies demonstrate an interaction between HBV infection and aflatoxins in hepatocarcinogenesis. The relevance of the biochemical molecular markers of aflatoxin exposure, HBV vaccination, and the reduction of aflatoxin exposure, in addition to the interaction between HBV infection and other risk factors in liver carcinogenesis, are discussed with regard to the implementation of measures for primary prevention.

Incidence and Timing of p53 Mutations during Astrocytoma Progression in Patients with Multiple Biopsies

Abstract: Mutations of the p53 tumor suppressor gene are a genetic hallmark of human astrocytic neoplasms, but their predictive role in glioma progression is still poorly understood. We analyzed 144 biopsies from 67 patients with recurrent astrocytoma by single-strand conformation polymorphism and direct DNA sequencing. We found that 46 of 67 patients (69%) had a p53 mutation in at least one biopsy. In 41 of these (89%), the mutation was already present in the first biopsy, indicating that p53 mutations are early events in the evolution of diffuse astrocytomas. Double mutations of the p53 gene were observed in three tumors and also present from the first biopsy. Of 28 low-grade astrocytomas with a p53 mutation, 7 (25%) showed loss of the normal allele in the first biopsy. The allele status remained the same in 95% of the cases, irrespective of whether the recurrent lesion had the same or a higher grade of malignancy. Progression of low-grade astrocytomas to anaplastic astrocytoma or glioblastoma occurred at a similar frequency in lesions with (79%) and without (63%) p53 mutations (P = 0.32), indicating that this genetic alteration is associated with tumor recurrence but not predictive of progression to a more malignant phenotype. However, the time interval until progression was shorter in patients with low-grade astrocytomas carrying a p53 mutation (P = 0.055).

Prospective study of diet and female colorectal cancer: The New York university women's health study

Abstract: The relation between diet and female colorectal cancer was analyzed in a prospective study of 14,727 women aged 34-65 years, who were enrolled at mammographic screening clinics in New York and Florida from 1985 to 1991. They were followed through the end of 1994 (average 7.1 yrs) by a combination of direct contact through mail and telephone and record linkages with regional tumor registries, resulting in 100 incident cases of colorectal cancer. There was no overall positive or inverse association of colorectal cancer risk with intakes of total calories, total or subclasses of fat, carbohydrate, or dietary fiber, whereas there was an inverse association with total protein. Among major food groups, there was a progressive decline in risk of colorectal cancer with increasing intake of fish and shellfish (relative risk for 4th vs. 1st quartile = 0.49, 95% confidence interval = 0.27-0.89). A similar inverse association was also observed for consumption of dairy products, and this association was explained mainly by calcium, not by other nutrients, such as fat or protein. The results of the present study indicated that certain dietary components of fish or dairy products may protect against colorectal cancer, whereas the relations with red meat or total fat remained unclear.

Transplacental Effects of 3′-Azido-2′,3′-Dideoxythymidine (AZT): Tumorigenicity in Mice and Genotoxicity in Mice and Monkeys

Abstract: Background: When given during pregnancy, the drug 3'-azido-2',3'-dideoxy-thymidine (AZT) substantially reduces maternal-fetal transmission of human immunodeficiency virus type 1 (HIV-1). However, AZT has been shown to be carcinogenic in adult mice after lifetime oral administration. In this study, we assessed the transplacental tumorigenic and genotoxic effects of AZT in the offspring of CD-1 mice and Erythrocebus patas monkeys given AZT orally during pregnancy. Methods: Pregnant mice were given daily doses of either 12.5 or 25.0 mg AZT on days 12 through 18 of gestation (last 37% of gestation period). Pregnant monkeys were given a daily dose of 10.0 mg AZT 5 days a week for the last 9.5-10 weeks of gestation (final 41%-43% of gestation period). AZT incorporation into nuclear and mitochondrial DNA and the length of chromosomal end (telomere) DNA were examined in multiple tissues of newborn mice and fetal monkeys. Additional mice were followed from birth and received no further treatment until subjected to necropsy and complete pathologic examination at 1 year of age. An anti-AZT radioimmunoassay was used to monitor AZT incorporation into DNA. Results: At 1 year of age, the offspring of AZT-treated mice exhibited statistically sig nificant, dose-dependent increases in tumor incidence and tumor multiplicity in the lungs, liver, and female reproductive organs. AZT incorporation into nuclear and mitochondrial DNA was detected in multiple organs of transplacentally exposed mice and monkeys. Shorter chromosomal telomeres were detected in liver and brain tissues from most AZT-exposed newborn mice but not in tissues from fetal monkeys. Conclusions : AZT is genotoxic in fetal mice and monkeys and is a moderately strong transplacental carcinogen in mice examined at 1 year of age. Careful long-term follow-up of AZT-exposed children would seem to be appropriate.

The Malmö Food Study: validity of two dietary assessment methods for measuring nutrient intake.

Abstract: BACKGROUND Nutritional epidemiology relies largely on dietary assessment methods for the estimation of the "exposure' variables which may be related to disease risk. METHODS This paper describes a methodological study conducted in Malmo, Sweden, to compare nutrient intake--estimated by two alternative dietary assessment methods--with a reference method consisting of 18 days of weighed food records. The two candidate methods were an extensive food frequency questionnaire with portion size to be estimated from a booklet of 120 sets of photos (method A) and a method involving the combination of a shorter questionnaire and a two-week food record (method B). RESULTS In absolute values, both methods overestimated nutrient intake by 20-40%, with method B closer to the reference for most nutrients. Both crude and energy-adjusted correlations between A-reference and B-reference were of the order of 0.50-0.60 for energy, energy-providing nutrients and most vitamins and minerals. Correlations were in the same range for most of the 14 fatty acids considered in the analyses. Protein intake, estimated from the analyses of urinary nitrogen on 6-8 repeated 24-hour urine collections per subject, was almost identical to the reference method values. Correlation between nitrogen-derived values and dietary measurement was 0.75. CONCLUSIONS Overall, the study indicated that both methods A and B had good ranking validity compared to the reference and that in most cases the combined method (B) performed slightly better than the extensive food frequency method (A).

Validation and calibration of dietary intake measurements in the EPIC project: Methodological considerations

Abstract: The statistical power of prospective studies on diet in relation to chronic disease risk can be improved by maximizing the variation in true intake levels actually distinguished-or 'predicted'-by dietary questionnaire assessments collected at baseline. This can be achieved by 1) developing a questionnaire method that provides measurements with the smallest possible random errors, thus maximizing the correlation of measured with true habitual intake levels; and 2) increasing the between-person variation in true dietary intake levels when combining multiple cohorts in populations with diverse consumption patterns. The first approach implies that, during the development or selection of the questionnaire method, correlations between measurements and true intake levels can be monitored; the second approach requires adjustment for between-centre differences in over- or underestimation of dietary questionnaire measurements. Besides optimizing the statistical power, it is important that the magnitude of the predicted variation in true intake level is estimated accurately, so as to allow unbiased estimations of relative risks. To meet these various objectives, substudies must be conducted for the 'validation' or 'calibration' of dietary questionnaire assessments, by comparison with additional measurements that have independent sources of error. This paper reviews the methodological considerations underlying the design and implementation of such substudies in the EPIC project, a collaborative multicentre study in nine Western European countries.

Design and methods of a population-based natural history study of cervical neoplasia in a rural province of Costa Rica: the Guanacaste Project

Abstract: This paper reports on the enrollment phase of a population-based natural history study of cervical neoplasia in Guanacaste, a rural province of Costa Rica with consistently high rates of invasive cervical cancer. The main goals of the study are to investigate the role of human papillomavirus (HPV) infection and its co-factors in the etiology of high-grade cervical neoplasia, and to evaluate new cervical cancer screening technologies. To begin, a random sample of censal segments was selected and enumeration of all resident women 18 years of age and over was conducted with the aid of outreach workers of the Costa Rican Ministry of Health. Of the 10738 women who were eligible to participate, 10049 (93.6%) were interviewed after giving written informed consent. After the interview on cervical cancer risk factors was administered, a pelvic examination was performed on those women who reported previous sexual activity. The pelvic examination included a vaginal pH determination and collection of cervical cells for cytologic diagnosis using three different techniques. Additional cervical cells were collected for determination of the presence and amount of DNA from 16 different types of HPV, and two photographic images of the cervix were taken and interpreted offsite by an expert colposcopist. Finally, blood samples were collected for immunologic and micronutrient assays. Women with any abnormal cytologic diagnosis or a positive Cervigram, as well as a sample of the whole group, were referred for colposcopy, and biopsies were taken when lesions were observed. The enrollment screening will serve as the basis for a prevalent case-control study, and the members of the cohort free from serious disease will be followed actively, at intervals of no more than a year, to study the natural history of HPV infection and the origins of high-grade squamous intraepithelial lesions (HSIL). Details of the field operation are outlined, with particular reference to the realization of this kind of study in developing countries. Descriptive data on the prevalence of disease and exposure to various risk factors are also presented.

Familial Nontoxic Multinodular Thyroid Goiter Locus Maps to Chromosome 14q but Does Not Account for Familial Nonmedullary Thyroid Cancer

Abstract: Thyroid goiter is a common condition that is often associated with iodine deficiency. Familial forms of goiter in areas not known to feature iodine deficiency are much less common. We have performed a genomic search on a single large Canadian family with 18 cases of nontoxic multinodular goiter in which 2 individuals also had papillary lesions highly suggestive of papillary carcinoma. A locus on chromosome 14q (MNG1 [multinodular goiter 1]) has been identified, with a maximal two-point LOD score of 3.8 at D14S1030 and a multipoint LOD score of 4.88 at the same marker, defined by D14S1062 (upper boundary) and D14S267 (lower boundary). The gene encoding thyroid-stimulating hormone receptor (TSHR), which is located on chromosome 14q, is outside the linked region. To determine the role of this gene in familial nonmedullary thyroid cancer (NMTC), we studied 37 smaller pedigrees each containing at least two cases of NMTC. Analysis by both parametric and nonparametric methods indicates that only a very small proportion of familial NMTC (point estimate 0.001, support intervals 0-.6 under a dominant model) is attributable to MNG1.

Validation and calibration of dietary intake measurements in the EPIC project: methodological considerations. European Prospective Investigation into Cancer and Nutrition.

Abstract: The statistical power of prospective studies on diet in relation to chronic disease risk can be improved by maximizing the variation in true intake levels actually distinguished--or 'predicted'--by dietary questionnaire assessments collected at baseline. This can be achieved by 1) developing a questionnaire method that provides measurements with the smallest possible random errors, thus maximizing the correlation of measured with true habitual intake levels; and 2) increasing the between-person variation in true dietary intake levels when combining multiple cohorts in populations with diverse consumption patterns. The first approach implies that, during the development or selection of the questionnaire method, correlations between measurements and true intake levels can be monitored; the second approach requires adjustment for between-centre differences in over--or underestimation of dietary questionnaire measurements. Besides optimizing the statistical power, it is important that the magnitude of the predicted variation in true intake level is estimated accurately, so as to allow unbiased estimations of relative risks. To meet these various objectives, substudies must be conducted for the 'validation' or 'calibration' of dietary questionnaire assessments, by comparison with additional measurements that have independent sources of error. This paper reviews the methodological considerations underlying the design and implementation of such substudies in the EPIC project, a collaborative multicentre study in nine Western European countries.

The relationship between dietary fat intake and risk of colorectal cancer: evidence from the combined analysis of 13 case-control studies

Abstract: The objective of this study was to examine the effects of the intakeof dietary fat upon colorectal cancer risk in a combined analysis of datafrom 13 case-control studies previously conducted in populations withdiffering colorectal cancer rates and dietary practices. Original datarecords for 5,287 cases of colorectal cancer and 10,470 controls werecombined. Logistic regression analysis was used to estimate odds ratios (OR)for intakes of total energy, total fat and its components, and cholesterol.Positive associations with energy intake were observed for 11 of the 13studies. However, there was little, if any, evidence of anyenergy-independent effect of either total fat with ORs of 1.00, 0.95, 1.01,1.02, and 0.92 for quintiles of residuals of total fat intake (P trend =0.67) or for saturated fat with ORs of 1.00, 1.08, 1.06, 1.21, and 1.06 (Ptrend = 0.39). The analysis suggests that, among these case-control studies,there is no energy-independent association between dietary fat intake andrisk of colorectal cancer. It also suggests that simple substitution of fatby other sources of calories is unlikely to reduce meaningfully the risk ofcolorectal cancer.

Atypical Central Neurocytoma

Abstract: The proliferative potential of central neurocytomas was determined in a biopsy series of 36 cases and compared with clinical outcome. The mean size of the growth fraction, as determined by MIB-1 labeling index (MIB-1 LI) at first biopsy, was 2.8 +/- 2.5 with a range of 0.1 to 8.6%. Neurocytomas with an MIB-1 LI > 2% comprised 39% of cases and showed a close correlation with the presence of vascular proliferation (p = 0.0006). The Kaplan-Meier analysis showed a highly significant difference in disease-free survival between the 2 groups (p = 0.0068). Over an observation time of 150 months, there was a 22% relapse among patients with an MIB-1 LI less than 2% and a 63% chance of relapse among those with an MIB-1 LI greater than 2%. We propose the term "atypical central neurocytoma" for the latter subset, corresponding to WHO grade II.

Nitric Oxide Induces Conformational and Functional Modifications of Wild-Type p53 Tumor Suppressor Protein

Abstract: Incubation in vitro of recombinant wild-type murine p53 protein with S-nitroso-N-acetyl-DL-penicillamine [a nitric oxide (NO)-releasing compound] has resulted in a change of p53 conformation and also in a significant decrease of its specific DNA binding activity. Similarly, upon treatment with S-nitroso-N-acetyl-DL-penicillamine (2-5 mM) or S-nitroso-glutathione (1-2 mM), human breast cancer cells (MCF-7), which express wild-type p53, rapidly accumulated p53 protein in the nuclei. This p53 protein, however, possessed a significantly decreased activity of specific DNA binding. On the other hand, lower concentrations of NO donors (0.25-0.5 mM) stimulated p53 accumulation as well as its DNA binding activity. These results suggest that excess NO produced in inflamed tissues could play a role in carcinogenesis by impairing the tumor suppressor function of p53.

Genetic interaction between PARP and DNA-PK in V(D)J recombination and tumorigenesis

Abstract: Poly(ADP-ribose) polymerase (PARP) and DNA-dependent protein kinase (DNA-PK) are DNA break-activated molecules, Although mice that lack PARP display no gross phenotype and normal DNA excision repair, they exhibit high levels of sister chromatid exchange, indicative of elevated recombination rates. Mutation of the gene for DNA-PK catalytic subunit (Prkdc) cases defective antigen receptor V(D)J recombination and arrests B- and T-lymphocyte development in severe combined immune-deficiency (SCID) mice. SCID V(D)J recombination can be partly rescued in T-lymphocytes by either DNA-damaging agents (gamma-irradiation and bieomycin) or a null mutation of the p53 gene, possibly because of transiently elevated DNA repair activity in response to DNA damage or to delayed apoptosis in the absence of p53. To determine whether the increased chromosomal recombination observed in PARP-deficient cells affects SCID V(D)J recombination, we generated mice lacking both PARP and DNA-PK. Here, we show that thymocytes of SCID mice express both CD4 and CD8 co-receptors, bypassing the SCID block. Double-mutant T-cells in the periphery express TCR beta, which is attributable to productive TCR beta joints. Double-mutant mice develop a high frequency of T-cell lymphoma. These results demonstrate that increased recombination activity after the loss of PARP anti-recombinogenic function can rescue V(D)J recombination in SCID mice and indicate that PARP and DNA-PK cooperate to minimize genomic damage caused by DNA strand breaks.

A 1-kb Alu-mediated germ-line deletion removing BRCA1 exon 17.

Abstract: Although more than 100 different BRCA1 germ-line mutations have already been identified in breast and/or ovarian cancer families, we report for the first time a deleterious genomic rearrangement in BRCA1. A 1-kb deletion comprising exon 17 was found in a large breast and ovarian cancer family, leading to a frameshift in the mutant mRNA due to the absence of exon 17. This deletion is probably the result of a recombination between two closely related Alu sequences. It was not detected by conventional PCR-based methods involving the genomic screening of the 22 coding exons or reverse transcription-PCR because the transcript without exon 17 is unstable in lymphoblastoid cell lines. Therefore, rearrangements in the BRCA1 gene should be sought in breast/ovarian cancer families in which no mutations have been found by PCR-based methods in the coding region or in the splice sites.

Mutations in BRCA1 and BRCA2 in breast cancer families: are there more breast cancer-susceptibility genes?

Abstract: To estimate the proportion of breast cancer families due to BRCA1 or BRCA2, we performed mutation screening of the entire coding regions of both genes supplemented with linkage analysis of 31 families, 8 containing male breast cancers and 23 site-specific female breast cancer. A combination of protein-truncation test and SSCP or heteroduplex analyses was used for mutation screening complemented, where possible, by the analysis of expression level of BRCA1 and BRCA2 alleles. Six of the eight families with male breast cancer revealed frameshift mutations, two in BRCA1 and four in BRCA2. Although most families with female site-specific breast cancers were thought to be due to mutations in either BRCA1 or BRCA2, we identified only eight mutations in our series of 23 site-specific female breast cancer families (34%), four in BRCA1 and four in BRCA2. According to the posterior probabilities calculated for mutation-negative families, based on linkage data and mutation screening results, we would expect 8-10 site-specific female breast cancer families of our series to be due to neither BRCA1 nor BRCA2. Thus, our results suggest the existence of at least one more major breast cancer-susceptibility gene.

Amplification and overexpression of MDM2 in primary (de novo) glioblastomas

Abstract: Glioblastoma multiforme (WHO Grade IV), the most malignant neoplasm of the human nervous system, develops rapidly de novo (primary glioblastoma) or through progression from low-grade or anaplastic astrocytoma (secondary glioblastoma). We recently reported that mutations of the p53 gene are present in more than two-thirds of secondary glioblastomas but rarely occur in primary glioblastomas, suggesting the presence of different genetic pathways (Watanabe et al, Brain Pathol 1996:6:217-24). In the present study, primary and secondary glioblastomas were screened by immunohistochemistry for MDM2 overexpression and by differential PCR for gene amplification. Tumor cells immunoreactive to MDM2 were found in 15 of 29 primary glioblastomas (52%), but in only 3 of 27 secondary glioblastomas (11%; P=0.0015). MDM2 amplification occurred in 2 primary (7%) glioblastomas but in none of the secondary glioblastomas. Only one out of 15 primary glioblastomas overexpressing MDM2 contained a p53 mutation. These results suggest that MDM2 overexpression with or without gene amplification constitutes a molecular mechanism of escape from p53-regulated growth control, operative in the evolution of primary glioblastomas that typically lack p53 mutations.

Pilot phase studies on the accuracy of dietary intake measurements in the EPIC project: Overall evaluation of results

Abstract: Background. As part of the European Prospective Investigation into Cancer and Nutrition (EPIC), preliminary studies were conducted to evaluate the accuracy of individuals' dietary intake measurements from newly developed questionnaires. Methods. In six countries that adhered from the very beginning to the multicentre, co-ordinated EPIC project, the validity studies were based on two repeat questionnaire measurements at the start and at the end of a 1-year period, in groups of about 100 volunteers of both sexes. In addition, during this year, up to 12 24-hour recalls per person were taken monthly, and up to four blood and urine specimens were collected for measurement of biochemical markers. In three countries that joined EPIC later, the designs of the validity studies and type of 'reference' measurement chosen were somewhat different. The results presented in this overview paper are taken partly from more detailed, country-specific publications, and partly from a central (re-)analysis of the original data, to ensure a uniform approach to the statistical analyses and presentation. Results. Averaged over subgroups by country and gender, Spearman coefficients of correlation between questionnaire measurements and the individuals' average 24-hour recalls ranged from 0.37 for fish to 0.68 for dairy products and 0.79 for alcoholic beverages. For energy-adjusted nutrient intakes (or nutrient densities, in the UK), mean Pearson correlation coefficients, corrected for residual attenuation due to day-to-day variations in the 24-hour recalls in all but two countries, ranged from 0.37 for retinol and 0.48 for vitamin E to 0.60 for carbohydrates and 0.12 for total alcohol intake. Correlations between energy-adjusted nutrient intakes and biochemical markers on average were low, but varied considerably between study centres. Conclusions. On average, most estimated correlation coefficients were of similar magnitude to those observed by independent research groups. The role of the preliminary validity studies, and various benefits drawn from these studies for further planning of the EPIC project are discussed.

Regulation of p53 by metal ions and by antioxidants: dithiocarbamate down-regulates p53 DNA-binding activity by increasing the intracellular level of copper.

Abstract: Mutations in the p53 tumor suppressor gene frequently fall within the specific DNA-binding domain and prevent the molecule from transactivating normal targets. DNA-binding activity is regulated in vitro by metal ions and by redox conditions, but whether these factors also regulate p53 in vivo is unclear. To address this question, we have analyzed the effect of pyrrolidine dithiocarbamate (PDTC) on p53 DNA-binding activity in cell lines expressing wild-type p53. PDTC is commonly regarded as an antioxidant, but it can also bind and transport external copper ions into cells and thus exert either pro- or antioxidant effects in different situations. We report that PDTC, but not N-acetyl-L-cysteine, down-regulated the specific DNA-binding activity of p53. Loss of DNA binding correlated with disruption of the immunologically "wild-type" p53 conformation. Using different chelators to interfere with copper transport by PDTC, we found that bathocuproinedisulfonic acid (BCS), a non-cell-permeable chelator of Cu1+, prevented both copper import and p53 down-regulation. In contrast, 1,10-orthophenanthroline, a cell-permeable chelator of Cu2+, promoted the redox activity of copper and up-regulated p53 DNA-binding activity through a DNA damage-dependent pathway. We have previously reported that p53 protein binds copper in vitro in the form of Cu1+ (P. Hainaut, N. Rolley, M. Davies, and J. Milner, Oncogene 10:27-32, 1995). The data reported here indicate that intracellular levels and redox activity of copper are critical for p53 protein conformation and DNA-binding activity and suggest that copper ions may participate in the physiological control of p53 function.