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Query: UMLS:C0596263 (carcinogenesis)
 64,820 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Fetal rat liver cells derived from 19-day gestation rats were exposed in culture to the carcinogen, 3'-methyl-4-dimethyl-aminoazobenzene (MDAB) for 3 days and then maintained in medium supplemented with the tumor promoter, phenobarbital (PB). Tumors developed in immunodeficient mice inoculated with cells derived from cultures which had been maintained for more than 8 weeks. Histologically, three types of tumors could be distinguished. One contained epithelial-like cells, which resembled what has previously been described as 'clear' epithelial cells. The second contained cells which were more basophilic, with prominent nuclei and closely resembled the hepatoma cell line Mc-A-R-777. The third group of tumors possessed cells of both varieties. Cell lines derived from these tumors were then characterized by determining their capacity to synthesize and secrete alpha-fetoprotein, albumin and transferrin by measuring the incorporation of 35S-methionine into immunoprecipitates obtained by reaction with the respective specific antibodies and the content of the respective mRNAs were determined by hybridization to cDNAs. The activity of gamma-glutamyl-transpeptidase (GGT) and the liver specific enzyme tyrosine aminotransferase (TAT), as well as the induction of TAT by dexamethasone was also evaluated. The presence of these markers in some of the cell lines strongly suggests that they are derived from parenchymal cells. In contrast, other cell lines which morphologically resemble 'clear' epithelial cells are negative, suggesting that they may be derived from non-parenchymal epithelial cells which exist in the original culture. However, some epithelial-like cell lines derived from tumors of mixed morphology appear different to those established from tumors which contained only epithelial-like cells. These express low levels of transferrin and tyrosine aminotransferase suggesting that they may be more closely related to hepatocytes than those cells which are derived from tumors which originally comprised only epithelial cells. The absence or presence of liver markers correlates with the morphology of the respective cell lines since transferrin and TAT are only present in significant levels in those lines which comprise cells with a morphology resembling hepatoma cell lines. In cell lines which show mixed morphology, immunocytochemistry reveals that significant amounts of transferrin are only present in the parenchymal-like population. Growth rate measurements show that the faster growing cell lines generally possessed lower levels of transferrin and TAT expression. It can be concluded from these studies that it is possible to transform cells derived from fetal rat liver in culture using a hepatocarcinogen.(ABSTRACT TRUNCATED AT 400 WORDS)
Carcinogenesis 1989 Jun
PMID:Transformation of cultured fetal rat liver cells by MDAB and phenobarbital. Morphological, biochemical and immunocytochemical characterization of cell lines. 247 May 26

Tumor induction with chronic feeding of methyl-donor-deficient diets has been well established; however, the biochemical and molecular mechanisms which predipose to tumorigenesis in this model are still not well understood. The purpose of the present investigation was to assess DNA damage and altered nucleotide metabolism in lymphocytes from Fischer 344 rats fed one of four semi-purified diets: (i) deficient in methionine and choline; (ii) deficient in folic acid; (iii) deficient in methionine, choline and folic acid; or (iv) a supplemented control diet. The accumulation of DNA-strand breaks, as assessed by DNA unwinding in alkali, was increased in lymphocytes from both the methionine/choline-deficient and folate-deficient groups, but was most severe in the group deficient in all three methyl donors. Lymphocyte DNA damage was consistently associated with alterations in folate-dependent thymidylate synthesis, and a decrease in intracellular levels of the DNA-repair-associated pyridine nucleotide, nicotinamide adenine dinucleotide. In the liver, a synergistic lipotropic interaction between folate deficiency and methionine/choline deficiency was observed, confirming the metabolic inter-relationship between these nutrients. Taken together, the results suggest that folate deficiency interacts with methionine/choline deficiency to potentiate symptoms of methyl-donor deficiency and that alterations in folate-dependent thymidylate synthesis are related to DNA damage in lymphocytes. These metabolic aberrations may contribute to immune dysfunction with chronic feeding of methyl-donor-deficient diets.
Carcinogenesis 1989 Jul
PMID:Diet-induced DNA damage and altered nucleotide metabolism in lymphocytes from methyl-donor-deficient rats. 247 30

Alterations in DNA-protein interactions (DPI) may play an important role in carcinogenesis. Although the mechanism of nickel carcinogenesis is unknown, nickel reportedly affects DPI. A microfiltration, nitrocellulose filter assay was utilized to study DPI in intact Chinese hamster ovary (CHO) cells and in isolated nuclei. Prior to exposure of CHO cells or isolated CHO cell nuclei, DNA and proteins were radiolabeled using 3H-thymidine and 35S-methionine, respectively. Nuclei were exposed to NiCl2 in 10 mM HEPES buffer (pH 6.8). CHO cells were exposed in either complete or a salts-glucose medium. Following exposure, nuclei or cells were incubated at 37 degrees C for 20 min in a high salt lysis solution; aliquots were loaded onto nitrocellulose filters and washed with a low salt solution. DNA (3H) retained on each filter was normalized to protein (35S) bound on the filter. Exposure of either whole cells or isolated nuclei to increasing, noncytotoxic concentrations of NiCl2 resulted in a dose dependent decrease in DPI. The effect of nickel on specific DNA-protein interactions was examined using a band shift assay and a cloned satellite DNA sequence. Nickel inhibited specific protein binding to the satellite DNA probe. The results of these two independent assays, which were conducted at physiological pH, indicate that NiCl2 inhibits specific DNA-protein interactions.
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PMID:Effect of nickel(II) on DNA-protein interactions. 248 78

We previously reported a rapid production model for pancreatic carcinoma development in Syrian hamsters incorporating the principle of selection by resistance to cytotoxicity. In the present experiment, the efficacy of repeated augmentation pressure with regard to generation of pancreatic lesions in hamsters initiated with N-nitrosobis(2-oxopropyl)amine (BOP) was investigated. Forty-eight female Syrian golden hamsters were divided into four groups according to the frequency of augmentation pressure. Group 1 received 70 mg/kg body weight of BOP and three injections of 20 mg/kg BOP. Groups 2-4 received 70 mg/kg BOP followed by one, two or three cycles of augmentation pressure consisting of dl-ethionine on sugar and salt diet, l-methionine and 20 mg/kg BOP. Hamsters were killed 10 weeks after the beginning of the experiment and the resultant incidences of pancreatic carcinomas from groups 1-4 were 0, 30, 50 and 46.2% respectively, the numbers of pancreatic carcinomas increasing with the frequency of augmentation pressure. A 46.2% yield of cholangiocarcinomas was also observed in group 4. The model should be useful for investigation of potential modulating factors since large numbers of lesions can be induced within a total experimental period of only 10 weeks.
Carcinogenesis 1989 Aug
PMID:Cycles of repeated augmentation pressure in rapid production of pancreatic and cholangiocellular carcinomas in hamsters initiated with N-nitrosobis(2-oxopropyl)amine. 254 90

DNA damage induced by Ni(II) plus H2O2 was investigated by a DNA sequencing technique using 32P-5'-end-labeled DNA fragments obtained from human c-Ha-ras-1 protooncogene. Ni(II) induced strong DNA cleavage in the presence of H2O2 even without piperidine treatment. Piperidine-labile sites were induced frequently at cytosine, thymine and guanine residues, and rarely at adenine residue. Diethylene-triamine N,N,N',N",N"-pentaacetic acid inhibited the DNA damage. In experiments with singlet oxygen scavengers, sodium azide and dGMP inhibited the DNA damage completely, whereas neither 1,4-diazabicyclo[2.2.2]octane nor dimethylfuran inhibited it. Among hydroxyl radical scavengers, dimethylsulfoxide and sodium formate inhibited the DNA damage considerably, whereas ethanol and mannitol did not. Methionine and methional inhibited the DNA damage completely. The results suggest that Ni(II) ion binds to DNA and subsequently reacts with H2O2 to form active species, which cause DNA damage. The possibility of Ni(II) plus H2O2-mediated DNA damage in vivo is discussed relative to the molecular mechanism of nickel carcinogenesis.
Carcinogenesis 1989 Dec
PMID:Site-specific DNA damage induced by nickel(II) ion in the presence of hydrogen peroxide. 268 51

Relatively simple and rapid analytical procedures involving two sequential HPLC separations were developed for the isolation of methylated purines in the urine of rats administered radiolabeled methylating carcinogens. Following a dose of [3H]N-methyl-N-nitrosourea (MNU), 7-methyl-adenine (m7Gua) was detected by chromatography as a urinary methylpurine in addition to the expected 7-methylguanine (m7Gua) and 3-methyladenine (m3Ade). When methyl-labeled methionine was given to rats concurrently with MNU, urinary m7Gua was labeled, but no radioactivity was recovered in either of the two methyladenine fractions. The profile of urinary methylated purines following a dose of dimethyl sulfate to the rat was similar. Small amounts of 1-methyladenine (m1Ade) and 3-methylguanine (m3Gua) were also detected in the urine. The excretion of m7Ade derived from the methyl group of the carcinogen rather than from the normal precursor for methylation, implies that this adduct, like m3Ade, may serve as an indicator in urine for exposure to methylating carcinogens.
Carcinogenesis 1989 Apr
PMID:Chromatographic detection of 7-methyladenine in urine of rats administered N-methylnitrosourea: a potential marker for monitoring exposure to methylating carcinogens. 270 23

The activity of 42 cytostatic drugs used for the treatment of human cancer was tested by the initiator tRNA acceptance assay for carcinogens. Of 17 drugs carcinogenic for rodents, 16 (94.1%) gave a positive response in the assay and six (85.7%) out of seven non-carcinogens showed no activity. The predictive value of the test for cytostatics was 91.7%. Treatment of tRNA with several cytostatics resulted in an inhibition of its acceptance for L-methionine. Cyclophosphamide, dibromdulcitol, 5-deoxy-5-fluorouridine and vincristine also inhibited, in addition to this, the charging of unfractionated tRNA from rat liver with L-alanine, L-lysine, L-phenylalanine and L-valine. Some drugs apparently react with the same target nucleoside which is common for all species of tRNA (probably the terminal adenosine residue that is esterified with amino acids). Such compounds do not yield reliable results in the initiator tRNA acceptance assay since this inhibitory effect interferes with the stimulating effect characteristic for carcinogens. However, results of the present study agree well with those obtained earlier with different classes of compounds (N-nitroso compounds, mycotoxins, etc.) and indicate that this newly developed assay may be a useful alternative also for the testing of carcinogenicity of cytostatic drugs.
Carcinogenesis 1989 Aug
PMID:The initiator tRNA acceptance assay as a short-term test for carcinogens. 5. Results with 42 cytostatic drugs. 275 15

Techniques are described for the isolation and cultivation of functionally intact mouse hair follicles. Follicles were isolated by collagenase digestion of dermis from 5-day-old mice and purified by differential centrifugation and filtration. Purified follicles were cultured in a Type 1 collagen matrix using Medium 199 and 8% fetal calf serum as the basic nutrient. Viability of follicles was maintained in culture since the cultures incorporated thymidine into DNA and methionine into proteins for at least 7 days. Furthermore, follicles isolated from the collagen matrix after 7 days could reattach to a plastic culture substrate or be further cultivated in a fresh collagen matrix. Functional integrity of cultured follicles was maintained since some follicle-specific cytoskeletal proteins were synthesized in vitro, and follicles isolated from the collagen matrix after 7 days formed a haired skin when recombined with dermal fibroblasts and grafted to a skin site on nude mice. Only a minority of follicles appeared to produce a mature hair shaft in vitro by morphologic criteria, however, and synthesis of the total complement of hair proteins was not observed. Cholera toxin was a strong mitogen for cultured follicles, whereas epidermal growth factor was slightly mitogenic. Epidermal growth factor stimulated the release of a Type 1 collagenase by follicle cells, however. This model system provides an opportunity for the systematic analysis of factors required for the induction of hair growth and the underlying physiology of hair follicle development. This model should also be useful for studying the role of the hair follicle in skin carcinogenesis.
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PMID:Cultivation of murine hair follicles as organoids in a collagen matrix. 282 17

The foregoing review of current risk factors associated with single nutrients and nutritional status in human populations, supported by animal studies, point clearly to a possibility for manipulation of nutrients in our diet, which may be a major tool for prevention of cancer. Migrant populations exhibit changes in incidence and frequency of certain types of cancer indicating external causes for cancer with diets high on the list of suspects. The foods we eat are probably the most important risk factors that human populations encounter and they offer a major focus for hope of preventing cancer. Food is also the most complex mixture to which we are exposed. Of all lifestyle factors associated with cancer, diet is one over which we exercise control. Epidemiologic observations, supported by controlled animal model research on carcinogenesis strongly suggest that through dietary control, some types of cancer are preventable. The evidence to date suggest that of all dietary factors of significance, those most likely to affect risk include total calories, protein, fat, vitamin A and carotene, the lipotropic factors methionine and choline, and the minerals zinc and selenium.
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PMID:Dietary modifiers of cancer. 283 41

Hepatocyte nodules, structures consistently seen in every model of liver carcinogenesis well before the first appearance of cancer, were examined with respect to some Phase I and Phase II components considered to be important in the metabolism of carcinogens and other xenobiotics. Phase I components are those related to the metabolism of xenobiotics and include microsomal cytochromes P-450 and mixed-function oxygenase activities. Phase II components are those related to the conjugation and detoxification reactions of xenobiotics and their metabolites and include glutathione S-transferases and glutathione. Nodules were induced by the resistant hepatocyte, choline-deficient, methionine-low diet, phenobarbital and orotic acid models of liver carcinogenesis. Also, nodules generated by the resistant hepatocyte model were examined after transplantation to the spleen of syngeneic animals. The hepatocyte nodules show a common biochemical pattern, consisting of decreased microsomal cytochromes P-450, cytochrome b5, and aminopyrine N-demethylase activity and increased glutathione and gamma-glutamyltransferase in whole homogenates and glutathione S-transferase activity in the cytosol. This similarity, appropriate to a resistance phenotype, adds additional support for the hypothesis that hepatocyte nodules may be a common step in liver carcinogenesis in several different models.
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PMID:A common biochemical pattern in preneoplastic hepatocyte nodules generated in four different models in the rat. 285 8


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