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

Urethane was found to be uniformly distributed in all the major organs of foetal, young and adult ICR/Jcl mice and then to disappear rapidly as measured by the incorporation of urethane-carbonyl-14C, thus permitting the accurate comparison of tumour susceptibility of cells in various organs of mice at different ages. Lung tumour frequency (tumours/lung) was significantly higher in mice treated with urethane when young (21 days old) and adult (63 days old) than in those treated in utero (Days 11-19 of gestation). When relative sensitivity of a lung cell was calculated as the ratio of average number of tumours per lung per mg of lung at the time of treatment, however, a lung cell of the foetus was more sensitive to urethane than that of the young and adult. Hepatomata were induced significantly only when male foetuses and neonates were exposed to urethane. The offspring exposed to urethane on Days 11-16, however, developed hepatomata in lower incidence than those exposed on Days 14-19, whereas the previous investigation by the author revealed that Days 11-13 correspond to the stage most sensitive to hepatocarcinogenesis. This contradiction was due to the occurrence of testicular hypogenesis (chemical castration) in all offspring of the former group. Differentiating female gonad and rapidly proliferating blood vessels of the placenta and deciduum were also sensitive to tumour induction by urethane. Thus, high tumour susceptibility of rapidly proliferating and undifferentiated cells suggests that some initiating events in the process of carcinogenesis may occur during or after DNA replication. Leukaemia induction in the young mice, but not in the foetus, remains to be elucidated.
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PMID:Comparison of tumour susceptibility among various organs of foetal, young and adult ICR/Jcl mice. 17 60

The effect of reovirus type 3 infection on the pulmonary adenoma response to urethan in strain A mice was examined. Urethan carcinogenesis in this system was suppressed from 30 to 60% when mice were exposed to reovirus either 6 days before, on the same day as, or 14 days after urethan administration. These findings suggested that reovirus infection interfered with the progression of urethan-induced pulmonary adenoma rather than the induction of lung tumors by urethan. When mice received multiple exposures to reovirus, the lung tumor response was enhanced. These findings indicated that reovirus infection in particular and virus infection in general may play an important role in the carcinogenic response to environmental chemicals.
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PMID:Effect of reovirus infection on pulmonary tumor response to urethan in strain A mice. 20 99

Vinyl carbamate was much more active (10 to 50 times) than ethyl carbamate for the initiation of skin tumors and for the induction of lung adenomas in mice. Vinyl carbamate was also mutagenic to Salmonella typhimurium TA 1535 and TA 100 in the presence of reduced nicotinamide adenine dinucleotide phosphate-fortified rat or mouse liver mitochondrial supernatant fractions. This mutagenic activity was inhibited strongly by cytochrome P-450 inhibitors. No mutagenic activity was observed for vinyl carbamate in the absence of added liver preparations or for ethyl carbamate in the presence or absence of liver fractions. Extensive tests with sensitive methods failed to detect vinyl carbamate as a metabolite of ethyl carbamate in the mouse in vivo. However, on administration of [ethyl-1-14C;1,2-3H]ethyl carbamate to adult mice the 3H/14C ratios of the hepatic DNA-, rRNA-, and protein-adducts were similar to each other and much lower than the ratio of the administered ethyl carbamate. These data are consistent with the presence of desaturated and/or oxidized ethyl groups in the macromolecular adducts. The qualitatively similar, but much stronger, carcinogenic activity of vinyl carbamate as compared to that of ethyl carbamate suggests that the metabolic pathways of these two carbamates may converge in the formation of similar or identical electrophilic reactants that bind covalently to macromolecules in vivo and initiate carcinogenesis.
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PMID:Vinyl carbamate as a promutagen and a more carcinogenic analog of ethyl carbamate. 35 28

A maximum tolerated dose (15 mug/g) of the carcinogen 4-nitroquinoline 1-oxide (4NQO) induced neither fetal deaths nor malformations when given to pregnant ICR/Jcl mice at the sensitive stages (Days 9 to 11) for the induction of malformations, although these embryotoxicities were detected with urethan and X-ray. This may not be due to the lack of teratogenic actions of 4NQO, but to the difficulty this compound has in reaching the embryo, because direct injection of 4NQO into the amniotic cavity of the Day-11 embryo, so that exposure was more direct, induced a high incidence of malformations. Similarity of the mechanism of chemical carcinogen-initiated teratogenesis and carcinogenesis was also suggested by the following findings. Urethan-initiated teratogenesis was almost completely inhibited by posttreatment with caffeine during the period of 0 to 24 and 24 to 48 hr after urethan treatment, whereas it was not inhibited during the 48- to 72-hr post-urethan and the 6- to 30-hr pre-urethan period. The results are similar to those of 4NQO-initiated transformation in cultured mouse embryo cells and 4NQO- and urethan-initiated lung tumorigenesis in mice. Cells carrying preteratogenic or pretumorigenic damage produced by some chemical carcinogens may be extremely sensitive to caffeine treatment during and/or after the postcarcinogen DNA replication period, thus resulting in decrease of malformations and tumors. The process may be related to error-prone DNA repair, because caffeine is known to inhibit the postreplication repair in cultured mouse cells.
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PMID:Similarity of the mechanism of chemical carcinogen-initiated teratogenesis and carcinogenesis in mice. 40 2

The intake of known dietary carcinogens was compiled and the cancer risk was estimated on the basis of carcinogenic potencies in animals as derived from the Carcinogenic Potency Database by Gold and co-workers. The total cancer risk was compared with the number of cancer cases attributed by epidemiologists to dietary factors (one-third of all cancer cases, i.e. approximately 80,000 per one million lives). Except for alcohol, the known dietary carcinogens could not account for more than a few hundred cancer cases. This was seen both with the DNA-reactive carcinogens (heterocyclic aromatic amines, polycyclic aromatic hydrocarbons, N-nitroso compounds, estragole, aflatoxin B1, ethyl carbamate, to name the most important factors) as well as with those carcinogens which have not been shown to react with DNA (e.g. caffeic acid and the carcinogenic metals arsenic and cadmium). Residues and contaminants turned out to be negligible. Among the various possibilities to explain the discrepancy we investigated the role of overnutrition. Dietary restriction in animals is well known for its strong reducing effect on spontaneous tumor formation. These data can be used to derive a carcinogenic potency for excess macronutrients: the tumor incidence seen with the restricted animals is taken as a control value and the increased tumor incidence in the animals fed ad libitum is attributed to the additional feed intake. For excess standard diet in rats, a carcinogenic potency TD50 of 16 g/kg/day was deduced from a recent study. Overnutrition in Switzerland, estimated to be 5.5 kcal/kg/day, was converted to excess food (1.9 g/kg/day) and the cancer incidence was calculated. The result, 60,000 cancer cases per one million lives, is provocatively close to the number of cases not explained by the known dietary chemical carcinogens. Mechanistic studies will be required to test our hypothesis and investigate the role of different types of macronutrients in overnutrition.
Carcinogenesis 1992 Dec
PMID:Chemical carcinogens and overnutrition in diet-related cancer. 147 26

Previous studies from this laboratory showed that (i) vinyl carbamate (VC) was much more carcinogenic than ethyl carbamate (EC) and that both carbamates induced the same spectrum of tumors in mice and rats, (ii) adducts of [14C]- or [3H]1,N6-ethenoadenosine and [14C]- or [3H]3,N4-ethenocytidine e were formed in the hepatic RNA of infant male B6C3F1 mice administered [1-14C]ethyl or [1,2-3H]ethyl EC and (iii) VC formed much more of the 1,N6-ethenoadenosine (epsilon Ado) adduct in the hepatic RNA and the 7-(2-oxoethyl)-guanine adduct in the hepatic DNA of mice than did EC. By analogy to the similar results of earlier studies by other investigators on the related carcinogen vinyl chloride, the above data suggested that VC epoxide was a reactive electrophilic metabolite of these carbamates. In the present studies, VC, but not EC, was found to be oxidized by 3-chloroperbenzoic acid to a derivative that reacted with adenosine to form epsilon Ado. Far more of this etheno nucleoside was formed from VC than from EC when these carbamates were metabolized by cofactor-fortified mouse liver microsomes in the presence of adenosine. Sodium diethyldithiocarbamate strongly inhibited these microsomal reactions and the formation of epsilon Ado in the hepatic RNA of mice administered either carbamate. Likewise, the i.p. preadministration of deithyldithiocarbamate markedly inhibited the induction of tumors by single i.p. doses of EC or VC in the livers of infant male B6C3F1 mice and in the livers, lungs and Harderian glands of infant female B6C3F1 mice. This inhibitor also considerably reduced lung tumor induction by VC in adult female A/Jax mice. 2-(2,4-Dichloro-6-phenyl) phenoxyethyl amine, a cytochrome P450 inhibitor, reduced the carcinogenicity of low doses of EC but appeared to increase the carcinogenicity of low doses of VC. The mutagenicity of VC for Salmonella typhimurium TA1535 in the presence of a hepatic activating system was greatly reduced by these inhibitors. The data from all these studies are consistent with the proposal that VC epoxide is an ultimate electrophilic and carcinogenic metabolite of EC and VC in the mouse.
Carcinogenesis 1990 Mar
PMID:1,N6-ethenoadenosine formation, mutagenicity and murine tumor induction as indicators of the generation of an electrophilic epoxide metabolite of the closely related carcinogens ethyl carbamate (urethane) and vinyl carbamate. 169 91

The use of the mouse skin multistage model of carcinogenesis has aided our understanding of critical target genes in chemical carcinogenesis. The mutagenic activation of the Harvey-ras proto-oncogene has been found to be an early event associated with the initiation of mouse skin tumors by the polycyclic aromatic hydrocarbon 7,12 dimethylbenz[alpha]anthracene and the pure initiator ethyl carbamate (urethane). In contrast to chemical initiation of mouse skin tumors, ionizing radiation-initiated malignant skin tumors have been shown to possess distinct non-ras transforming gene(s). Differential screening of cDNA libraries made from chemically initiated malignant skin tumors has been used to identify a number of cellular gene transcripts that are overexpressed during mouse skin tumor progression. These differentially expressed genes include beta-actin, ubiquitin, a hyperproliferative keratin (K6), a gene whose product is a member of a fatty acid or lipid-binding protein family, and a gene called transin or stromelysin. The overexpression of the stromelysin gene, which encodes a metalloproteinase that degrades proteins in the basement membrane, is hypothesized to play a functional role in malignant tumor cell invasion and metastasis. We believe that the cloning, identification, and characterization of gene sequences that are differentially expressed during tumor progression could lead to the discovery of gene products that either play functional roles in skin tumor progression or in the maintenance of various progressive tumor phenotypes.
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PMID:Differential gene expression during multistage carcinogenesis. 177 1

Groups of hairless mice were painted with urethan alone, with the complete carcinogen 7,12-dimethylbenz[a]anthracene (DMBA) alone, and with an initiating dose of DMBA followed by continual treatment with urethan or with the promoter 12-O-tetradecanoylphorbol-13-acetate (TPA). The animals were examined once a week for an appropriate time period. Malignant and non-malignant skin tumors were registered and classified. Lung adenomas and other internal tumors were also counted. The results show that all types of treatment produced skin tumors, some of which were malignant. When urethan was used lung adenomas also appeared, along with a few other tumors. The results show that a 10% solution of urethan in acetone is a significant promoter, showing synergistic increase of DMBA-induced skin tumors, but urethan is not as strong a promoter as 10 nmol TPA. Urethan is said to be the pure initiator of skin carcinogenesis. Previously the author has shown that urethan alone is a complete carcinogen and here it is shown that it is also a promoter. Hence, the current hypothesis of urethan as a pure initiator in skin carcinogenesis has been disproved.
Carcinogenesis 1991 May
PMID:Urethan (ethyl carbamate) is an effective promoter of 7,12-dimethylbenz[a]anthracene-induced carcinogenesis in mouse skin two-stage experiments. 190 92

Murine susceptibility to ethyl carbamate-induced carcinogenesis is strain dependent. In vivo sister chromatid exchange (SCE) responses to ethyl carbamate were evaluated in bone marrow cells of gravid adenoma-susceptible (ICR/Jcl), and resistant (C57Bl/6J) and (DBA/2J) murine dams, as well as in liver cells of their respective ICR/Jcl, C57Bl/6J X DBA/2J (BDF1), and DBA/2J X C57Bl/6J (BDF), fetuses following a single intravenous injection of 1.1, 2.2, or 3.3 mmol/kg of ethyl carbamate on gestation day 13/14. Bone marrow tissues of C57Bl/6J and DBA/2J, but not ICR/Jcl dams, demonstrated greater sensitivity to SCE induction than liver cells of their respective fetuses. Furthermore, relative SCE responses in bone marrow among dams indicated greater sensitivity of the more tumor-susceptible ICR/Jcl and C57Bl/6J strains to SCE induction by ethyl carbamate relative to the more tumor-resistant DBA/2J strain. In addition, concurrent alterations (stimulation or inhibition) of bone marrow cell cycle kinetics by ethyl carbamate were consistent with hormone-related, strain-dependent hematopoietic stress during pregnancy.
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PMID:Comparative in vivo sister chromatid exchange induction by ethyl carbamate in maternal and fetal tissues of tumor-susceptible and -resistant murine strains. 197 64

Liuwei Dihuang Decoction is a representative classic prescription for nourishing Yin in Traditional Chinese Medicine. Experimental and clinical studies showed that the recipe could 1. inhibit carcinogenesis of anterior stomach by N-nitrososarcosine ethyl ester in mice; 2. inhibit the formation of lung tumors induced by Urethan in mice; 3. decrease spontaneous tumorigenesis in LACA strain; 4. inhibit the mutagenic activity of Endoxan in micronuclear test. Patients with epithelial dysplasia of esophagus, a preneoplastic lesion, were treated by using this recipe. The canceration rate within 1 year was 2.2% in the treated and 12.4% in an untreated group. Within 5 years these rates were 9% and 26% respectively (p less than 0.025).
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PMID:Preventing effect of "liuwei dihuang decoction" on esophageal carcinoma. 254 8


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