Showing papers by "International Agency for Research on Cancer published in 1981"

Mutagenicity assays of estrogenic hormones in mammalian cells.

Abstract: In view of the extensive use of estrogenic hormones by the human population, either as therapeutic agents, or in the composition of contraceptive pills, it is important to investigate more thoroughly the adverse biological effects of synthetic hormones. Diethylstilbestrol, ethynylestradiol, estradiol-17beta and estrone were chosen for our experiments. Evidence of carcinogenicity in rodents has been reported for each of these compounds, but so far only few studies have been carried out in vitro. Because it has been shown that isolated liver cells in suspension are able efficiently to metabolize steroid hormones, we have tested these chemicals in V79 cells with a cell-mediated system using primary hepatocytes from male and female rats as the metabolic layer. The incubation in the presence of the chemical to be tested was carried out at concentrations ranging from 25 to 100 microM, for 48 h before plating the V79 cells to score for mutagenicity or toxicity. In the absence of hepatocytes, the 4 estrogenic hormones were very toxic, but not mutagenic. The co-cultivation of V79 cells with primary hepatocytes decreased the toxic effect induced by the sex hormones, except in the case of ethynylestradiol. However, no mutation, determined as 8-azaguanine- or ouabain-resistance, was induced under these conditions by any of the hormones tested. The lack of mutagenic activity of these hormones in our assay had been confirmed by the use of primary liver cells that originated from a rat treated with Aroclor, an inducer of drug-metabolizing enzymes.

Studies on the miscoding properties of 1,N6-ethenoadenine and 3,N4-ethenocytosine, DNA reaction products of vinyl chloride metabolites, during in vitro DNA synthesis

Abstract: 1,N6-Ethenoadenine (epsilon A) and 3,N4-ethenocytosine (epsilon C) are formed when electrophilic vinyl chloride (VC) metabolites, chloroethylene oxide (CEO) or chloroacetaldehyde (CAA) react with adenine and cytosine residues in DNA. They were assayed for their miscoding properties in an in vitro system using Escherichia coli DNA polymerase I and synthetic templates prepared by reaction of poly(dA) and poly(dC) with increasing concentrations of CEO or CAA. Following the introduction of etheno groups, an increasing inhibition of DNA synthesis was observed. dGMP was misincorporated on CAA- or CEO-treated poly(dA) templates and dTMP was misincorporated on CAA- or CEO-treated poly(dC) templates, suggesting that epsilon A and epsilon C may miscode. The error rates augmented with the extent of reaction of CEO or CAA with the templates. Base-pairing models are proposed for the epsilon A.G. and epsilon C.T pairs. The potentially miscoding properties of epsilon A and epsilon C may explain why metabolically-activated VC and its reactive metabolites specifically induce base-pair substitution mutations in Salmonella typhimurium. Promutagenic lesions may represent one of the initial steps in VC- or CEO-induced carcinogenesis.

Alkylation of DNA and tissue specificity in nitrosamine carcinogenesis

Abstract: A peculiarity of nitrosamines is the high degree of cell and organ specificity in inducing tumors. There is substantial evidence that the initiation of the carcinogenesis process by carcinogens of this group is linked to the metabolic competence of the target tissue or cell to convert these carcinogens into mutagenic metabolites and to the binding of those metabolites to cellular DNA. Alkylation occurs in the DNA at the N-1, N-3, and N-7 positions of adenine; the N-3, N-7, and O6 of guanine; the N-3, and O2 of cytosine; and the N-3, O4, and O2 of thymine; and the phosphate groups. The initial proportion of each DNA adduct depends upon the alkylating agent used. The various DNA adducts are lost to a variable extent from DNA in vivo by spontaneous release of bases and/or by specific DNA repair processes. Studies conducted in vitro and vivo indicate that alkylation at the oxygen atoms of DNA bases is more critical than alkylation at other positions in the mutagenesis and carcinogenesis induced by N-nitroso compounds. In particular, tissues in which tumors occur more frequently after a pulse dose of nitrosamine are those in which O6-alkylguanine persists longest in DNA, presumably resulting in an increased probability that a miscoding event (mutation) will take place during DNA synthesis. The more rapid removal of O6-methylguanine from the DNA of liver (as compared with extrahepatic tissues) of rats has been associated with the absence of tumor production in this organ by a single dose of dimethylnitrosamine; however, a significant incidence of liver tumors is observed if the same dose is given 24 hr after partial hepatectomy, and tumors are induced by such a dose of dimethylnitrosamine in the liver of hamsters, which has a low capacity to remove O6-methylguanine from its DNA. These data also indicate that the rate of disappearance of 7-methylguanine from the liver or extrahepatic tissues is independent of the dose of dimethylnitrosamine; whereas O6-methylguanine is lost from DNA more rapidly after a low dose of this nitrosamine. It has been shown that in liver the removal of O6-methylguanine but not other DNA adducts, from DNA can be affected by pretreating the animals with N-nitroso compounds. The modulation of DNA repair processes observed after a single dose and after chronic treatment with nitrosamines is discussed in relation to the tissue-specific carcinogenic effect of this group of carcinogens.

Studies on mutagenic constituents of apple brandy and various alcoholic beverages collected in western France, a high incidence area for oesophageal cancer.

Abstract: Apple brandies, alcoholic spirits produced in the west of France, as well as other types of alcoholic beverage (rums, whiskies, armagnacs, cognacs) were tested for mutagenicity on Salmonella typhimurium TA98 and TA100 in the plate-incorporation assay in the presence or the absence of rat-liver S9. The mutagenic activity of acrolein, gamma-butyrolactone, furfural and glycidol, chemicals usually found in these spirits, was assayed by the same procedure. Glycidol was mutagenic in TA1535 and TA100 without metabolic activation. We found higher and more frequently positive responses in home-made apple brandies than in the other beverages; therefore, further fractionation for isolation of the mutagenic compound(s) was performed by using spinning band column distillation, HPLC and gas chromatography. The fractions contained various types of mutagen, i.e., frameshift and/or base-pair substitution mutagens; some required metabolic activation and others did not in either the alcoholic, aqueous or non-volatile fractions. The results indicate that the high incidence of oesophageal cancer correlated with the alcoholic consumption in these areas might be at least partially attributable to the presence of mutagens in apple brandies.

Increased cancer incidence in the progeny of male rats exposed to ethylnitrosourea before mating.

Abstract: Results from previous experiments have indicated tha persistence of an increased cancer risk in subsequent generations following prenatal exposure to a chemical carcinogen. In the present experiment, the possible role of prezygotic events in determined cancer risk was investigated in the progeny of male rats treated with ethylnitrosourea (ENU) before mating with untreated females. Eight BDVI male rats were given a single i.p. dose of 80 mg/kg bw ENU and each rat was then caged at weeks 1, 2, 3 and 4 after treatment with three untreated females. Fertility was lower and preweaning mortality higher in the experimental group, as compared to controls, particularly at the 4th-week mating. Survival rates after weaning were similar in the progeny of treated males and controls, as was the total incidence of tumours. However, analysis of tumour incidence at the various organ sites showed an increased incidence of neurogenic tumours in the progeny of ENU-treated males, as compared to that of controls.

Inter-individual differences in oxidative benzo(a)pyrene metabolism by normal and tumorous surgical lung specimens from 105 lung cancer patients.

Abstract: Oxidative benzo(a)pyrene (BP) metabolism was studied in 12,000 g(S12) supernatant fractions of surgical lung specimens obtained from lung cancer patients undergoing surgical resection. Arylhydrocarbon (BP)hydroxylase (AHH) activity was determined in both normal and tumorous lung tissue specimens from the same patient. A more than 20-fold inter-individual variation in AHH activity was found in both the normal and the tumorous lung tissue samples investigated. The apparent KM of the pulmonary enzyme (1–2.5 × 10−4 M) was identical in tumorous and normal tissue. High-performance liquid chromatography (HPLC) of ethyl acetate-extractable BP metabolites from the normal lung tissue of six patients identified phenols, dihydrodiols and quinones of BP. The mean yields of these metabolites were very similar to those obtained in assays in the presence of lung S12 from BDVI rats, except that more trans−9, 10-dihydro-9, 10-dihydroxy-BP (BP-9, 10-diol) was formed in the presence of human lung S12. The formation of 3-hydroxy-BP (3-HO-BP) and BP-9, 10-diol in human lung specimens, however showed variations up to 7- and 13-fold, respectively. In normal lung specimens, the total amounts of 3-HO-BP and 9-HO-BP formed correlated positively with the total amounts of trans-7, 8-dihydro-7, 8-dihydroxy-BP (BP-7, 8-diol), BP-9, 10-diol and trans-4, 5-dihydro-4, 5-dihydroxy-BP (BP-4, 5-diol) formed (r = 0.83; p 1 in 11. In 7 of 10 subjects who underwent surgical resection for suspected lung tumours, but in whom histological analysis revealed no malignant tissue, R was > 1 for the AHH activity in the inflammatory tissue to that in normal tissue. The observation of consistently lower AHH activity in malignant lung tissue parallels findings in hyperplastic liver nodules induced in rats by hepatocarcinogens. The frequency distribution of pulmonary AHH activity in normal and tumorous tissue from 105 lung cancer patients, with all types of tumours, was compatible with a unimodal distribution of the enzyme activity. In a subset of 43 patients with squamous-cell carcinoma, the same distribution was seen; in those patients, AHH activity in tumorous tissue correlated negatively (r = −0.18; p > 0.10) with the number of cigarettes smoked per day prior to surgery. No differences were observed between the mean values for AHH activity in cases of squamous-cell carcinoma and those of adenocarcinoma. No relationship was found between AHH activity in normal or tumour tissue and the age of patients. Whether differences in pulmonary AHH activity represent a host risk factor in persons who smoke remains to be investigated.

Report on international comparative evaluation of possible value of assays for immune complexes for diagnosis of human breast cancer.

Abstract: There have been several reports on the possible value of measurements of circulating immune complexes for the diagnosis of human breast cancer. To begin to evaluate this possibility and the comparability of results among laboratories, a cooperative study was organized under the auspices of the International Agency for Research on Cancer and the National Cancer Institute (NCI) of the United States. Investigators from four laboratories performing assays for immune complexes were sent coded aliquots of serum specimens from the NCI-Mayo Clinic Serum Bank. The serum panel consisted of specimens from 30 patients with breast cancer (including 20 from untreated patients with resectable tumors), 30 preoperative patients with benign breast disease, and 30 normal women. Although some significant differences in levels of immune complexes between cancer patients and controls were seen, none of the assays had sufficient discriminatory capacity to support optimism about the diagnostic value of this approach. To relate the results with immune complexes to those with a widely used cancer marker, the same sera were also tested for levels of carcinoembryonic antigen (CEA). The CEA assay provided significant discrimination between cancer patients and normal donors but did not significantly discriminate between malignant and benign breast diseases.

Problems related to the use of sodium hypochlorite in the detoxification of aflatoxin B1

Abstract: Sodium hypochlorite solution which has been in use for a long time as a reagent to treat laboratory wastes and equipment contaminated with aflatoxin B1, has been shown by TLC, HPLC and mass spectrometry to lead to the formation of products which include its carcinogenic 2,3-dichloro derivative. A modification to the method of decontamination using sodium hypochlorite, based on the instability of the 2,3-dichloro derivative in the presence of acetone, is suggested.

EBV-positive Burkitt's lymphoma from Algeria, with a three-way rearrangement involving chromosomes 2, 8 and 9.

Abstract: Burkitt's lymphoma was diagnosed in a male Algerian child presenting with abdominal and jaw tumours. Viral studies revealed that this non-endemic case was associated with the Epstein-Barr virus. Cytogenetic examination of tumour cells showed a complex three-way rearrangement involving chromosomes 2, 8 and 9. Our report indicates that, in Burkitt's lymphoma, not only simple but also complex translocations involving chromosome 8 may arise. This finding in a North African case emphasizes the need for more detailed study of the clinical, virological and cytogenetic features of Burkitt's lymphoma throughout the world.

Effect of glutathione and uridine 5'-diphosphoglucuronic acid on mutagenesis by benzo[a]pyrene and aflatoxin B1 in the Salmonella/microsome assay.

Abstract: In the Salmonella/microsome plate or liquid assay, the addition of glutathione (GSH) and uridine 5'-diphosphoglucuronic acid (UDPGA), both cofactors for GSH-S-transferases or UDPGA-transferases, altered the rat-liver microsome-mediated mutagenesis of benzo[a]pyrene (BP) and aflatoxin B1 (AFB). With either BP or AFB, an increased, unchanged or decreased number of revertant colonies of S. typhimurium was observed, depending on the substrate concentration, the source of rat-liver 9000 X g supernatant (S9), the time of incubation and the type of mutagenicity test (liquid or plate assay). Several factors responsible for quantitative changes in the pattern of BP and AFB metabolites under various assay conditions in vitro, which alter the overall mutagenic activity of the parent compound, are discussed.

The Enhanced Repair of O 6 -Alkylguanine in Mammalian Systems

Abstract: The “adaptive” response in bacteria may be defined in terms of a reduction in the toxicity and mutagenicity of certain agents by pre-exposure to low levels of the agent and the effect is intimately associated with an enhanced DNA repair process1,2,3. In mammals it is premature to conclude that an equivalent system exists since none of these parameters have been examined simultaneously but there are now a number of systems in which pretreatment with various carcinogenic agents has been shown to enhance the capacity of certain tissues to repair O6-alkylguanine lesions in DNA. These systems are outlined here and the possible relationship of this phenomenon to carcinogenicity is considered.

Antiviral specificities of immunoglobulins secreted by human lymphocytes immortalized in vitro with Epstein-Barr virus

Abstract: Summary Lymphocytes from a patient (Ma.) with a chronic T-lymphocytic leukaemia were infected with 2 different strains of Epstein-Barr Virus (EBV): B95-8 and M81. Two lymphoblastoid B-cell lines were established; whereas the Ma-M81-cell line secreted a low level of immunoglobulins (Ig) into the culture medium, the Ma-B95-cell line produced unusually large amounts (32 μg/10 6 cells/24 h), mainly IgG. These polyclonal IgG possessed antiviral activities against cytomegalovirus, respiratory syncytial virus, rubella and measles viruses (the patient's serum at the time of lymphocyte immortalization contained IgG antibodies of the same specificities). The Ma-M81-cell line produced complete EBV virions, while in the Ma-B95 cells the replicative cycle of EBV was blocked at the early antigen stage; intracytoplasmic enlarged cisternae were observed in numerous of these latter cells which produced Ig for more than a year.

Liver cell cancer--intervention studies.

Abstract: The field studies leading to possible intervention procedures are reviewed. Currently the most promising form of intervention is the prevention of aflatoxin contamination of foodstuffs. It is essential that these are monitored and their efficacy in lowering the incidence of liver cancer measured. The association of liver cancer with hepatitis B infection may be a confounding factor and the impact of this on the study population must also be considered. The imminent production of vaccines for hepatitis B infection may provide an alternative or additional mode of intervention. The possibilities for intervention in liver cell cancer appear one of the brighter prospects for primary prevention of a cancer.

Analyse ordinaler daten am beispiel von beobachtungsstudien

Abstract: Ordinal-Merkmale, wie z.B. Krankheitsstadium, Altersgruppe, histologische Differenzierung u. a. fallen sehr haufig bei der Gewinnung von Daten aus Krankenregistern oder ahnlichen Erhebungen, aber auch bei geplanten Studien an. McCullagh (1980) hat in einer umfangreichen Arbeit an Beispielen gezeigt, das statistische Methoden die Analyse solcher Daten aus verschiedenen Blickwinkeln mit verschieden gearteten Aussagen erlauben. Dabei sind die vorliegende Stichprobensituation und die damit verbundenen Aussagemoglichkeiten sehr grundlich zu beachten. Am Beispiel einer Beobachtungsstudie werden die Einsatzmoglichkeiten verschiedener, zum Teil neuerer Methoden, demonstriert und die unterschiedlichen Interpretationsmoglichkeiten diskutiert, wie z.B. Test auf Trend nach Armitage (1955), verallgemeinerte Logittransformation und relatives Risiko auf eine Antwortklasse. Weiterhin wird die Frage nach der Konsistenz des Assoziationsmusters (Wahrendorf 1980) mit Hilfe weiterer Methoden nachgegangen. Dabei zeigt es sich, das all die verschiedenen relevanten Fragestellungen letztlich das eine Ziel haben, namlich die Beantwortung der Frage nach dem Ausmas einer Wechselwirkung zwischen den ordinalen Merkmalen.

On the Possible Role of the Miscoding DNA-Lesions, 1,N6-Etheno-Adenine and 3,N4-Ethenocytosine, in Vinyl Chloride-Induced Mutagenesis and Carcinogenesis

Abstract: Chloroacetaldehyde (CAA) and chloroethylene oxide (CEO), two reactive metabolites of vinyl chloride, were used to introduce increasing amounts of 1,N6-ethenoadenine (eA) and 3,N4-etheno cytosine (eC) residues in poly(dA) and poly(dC), respectively. The modified polynucleotides were assayed with E. coli DNA polymerase I for their template activity and for misincorporation. The miscoding properties of eA and eC that we observed may explain the mutagenic effects reported for vinyl chloride and its metabolites; these lesions may also represent one of the initial steps in vinyl chloride or CEO-induced carcinogenesis.