Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C1326912 (tumorigenesis)
 57,481 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

It is well established that dietary polyunsaturated omega-6 fatty acids promote tumorigenesis and support the activity of mixed-function oxidases (MFO), which are responsible for carcinogen activation. This study was undertaken to determine if increased levels of dietary menhaden fish oil (rich in omega-3 fatty acids) would affect in vivo binding of [3H]benzo[a]pyrene (BP) to rat liver DNA. The effects of dietary menhaden oil on the activities of phase I and phase II drug-metabolizing enzymes were also studied to determine the possible relationships between the activity of these enzymes and the binding of [3H]BP metabolites to liver DNA. Following a single intraperitoneal injection of [3H]BP, more BP was bound to liver DNA recovered from rats fed diet containing 20% menhaden oil for 11 days at all time intervals tested (16, 24, 48, and 192 hours) than was bound from rats fed 0.5% menhaden oil. The increased binding of [3H]BP to liver DNA of rats fed the high level of menhaden oil may be due, in part, to increases in the MFO responsible for BP activation (as suggested by increased cytochrome P-450 level and total BP hydroxylase activity). The higher concentrations of radioactivity extracted from blood of rats fed 20% menhaden oil diet at the initial time periods (16 and 24 hours) may be a reflection of the greater capacity of the liver to metabolize BP to more water-soluble metabolites. The maximum velocity (Vmax) for ethoxycoumarin O-dealkylase, expressed as nanomoles per milligram protein or per gram liver, was increased three- to fourfold by feeding the high level of menhaden oil. The differences in these enzymatic responses suggest that certain form(s) of cytochrome P-450 are preferentially increased by feeding the omega-3 fatty acids of menhaden oil.
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PMID:BP metabolism and the in vivo binding to hepatic DNA of rats fed diets containing menhaden fish oil. 349 53

Nickel compounds that possess similar elemental compositions but vary in physicochemical properties can elicit markedly different biological effects. The crystalline nickel sulfides and oxides that slowly dissolve in body fluids and readily enter cells by phagocytosis tend to be most active in producing morphological transformation of SHE cells in vitro and stimulating erythrocytosis and carcinogenesis following ir administration to rats. The capacities of particulate nickel compounds to induce erythropoietin-mediated erythrocytosis in rats are closely correlated with their carcinogenic activities; hence erythrocytosis stimulation can serve as a screening test for carcinogenicity. Although water-soluble nickel salts have not been shown to initiate carcinogenesis in rodents, the soluble nickel salts are evidently effective as cancer promotors following initiation of tumorigenesis by aromatic hydrocarbons and nitrosoamines. Growing evidence suggests that the Ni(III)/Ni(II) redox-couple facilitates oxygen free-radical reactions, which may represent one of the molecular mechanisms for genotoxicity and carcinogenicity of nickel compounds.
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PMID:Physicochemical and biological attributes of nickel compounds in relationship to carcinogenic activities. 360 50

Chronic exposure to phenobarbital (PB) in the drinking water of male B6C3F1 mice starting at 4 weeks of age and subsequent to a single (ip) injection of diethylnitrosamine (DENA) administered on Day 15 of age has been shown to result in the inhibition of hepatic tumor formation. In this study, we varied the time of onset of PB administration to determine if sexual maturity would affect liver tumor formation and progression. Male B6C3F1 mice were divided into eight groups. Groups 1-4 received a single (ip) dose of 5 mg/kg DENA at 15 days of age while mice in groups 5-8 received saline. At weaning (4 weeks of age), groups 1 and 5 received deionized drinking water (DDW) for 24 weeks; groups 2 and 6 received PB (500 ppm) in the drinking water (PB DW) for 16 weeks followed by DDW for 8 weeks; groups 3 and 7 received DDW for 4 weeks, PB DW for 16 weeks, and then DDW for 4 weeks; and groups 4 and 8 received DDW for 8 weeks and PB DW for 16 weeks. Mice were killed at 28 weeks of age and hepatic lesions were evaluated. Mice which did not receive DENA (groups 5-8) exhibited no liver tumors. Animals in groups 1-4 exhibited hepatocellular foci and adenomas. PB treatment in groups 2, 3, or 4 resulted in a significant decrease in the incidence of DENA-initiated hepatocellular foci and adenomas when compared to those observed in group 1. The number of foci in group 4 was significantly decreased compared to those in groups 2 and 3. There was no significant difference in the adenoma incidence among groups 2, 3, and 4. No significant differences were observed in the sizes of foci or adenomas among groups 1-4. Data from this study suggest that the inhibition of hepatocellular tumorigenesis by PB remains intact even when the start of the administration of PB is withheld up to 12 weeks of age.
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PMID:Effect of the age of B6C3F1 mice on phenobarbital promotion of diethylnitrosamine-initiated liver tumors. 362 93

The metabolism and DNA binding of benzo(a)pyrene [B(a)P] were compared in early passage mouse embryo cell cultures prepared from SENCAR mice, a strain especially susceptible to two-stage tumorigenesis, and BALB/c mice, a strain relatively resistant to two-stage tumorigenesis. Cultures from both strains metabolized similar amounts of B(a)P; however, the proportion of water-soluble metabolites formed was higher in the BALB/c cultures than in the SENCAR cultures. The major metabolites formed in cultures from both strains were B(a)P-9,10-diol, B(a)P-7,8-diol and the glucuronic acid conjugate of 3-hydroxy-B(a)P. The level of binding of B(a)P to DNA was greater in the SENCAR mouse embryo cell cultures than in the BALB/c cultures after 5, 24, and 48 hr exposure. The major B(a)P-DNA adduct formed in B(a)P-treated cultures from both strains was the adduct formed by reaction of (+)anti-B(a)P-7,8-diol-9,10-epoxide [anti-B(a)PDE, the isomer with the epoxide and the benzylic hydroxyl on opposite faces of the molecule] with the exocyclic amino group of deoxyguanosine. Immobilized boronate chromatography followed by high-performance liquid chromatography demonstrated the presence of small amounts of syn-B(a)PDE (the isomer with the epoxide and benzylic hydroxyl on the same face of the molecule)-DNA adducts. The proportions of these amounts were similar in cultures from both strains. The results suggest that SENCAR mouse embryo cell cultures may convert less B(a)P to water-soluble metabolites and more to DNA-binding metabolites than BALB/c mouse embryo cells.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Metabolic activation of benzo(a)pyrene in SENCAR and BALB/c mouse embryo cell cultures. 378 Jun 31

The chlorinated hydrocarbons chloroform (CHCl3), 1,1-dichlorethane (1,1-DCE) and 1,2-dichloroethane (1,2-DCE) have been detected in finished drinking water. When administered to B6C3F1 mice by gavage in corn oil, these compounds have been shown to induce hepatic tumors. The present study examines the effect on liver tumor incidence of continuous treatment of CHCl3 (600 mg/L and 1800 mg/L), 1,1-DCE (835 mg/L and 2500 mg/L), and 1,2-DCE (835 mg/L and 2500 mg/L) administered in drinking water to male B6C3F1 mice using a two-stage (initiation/promotion) treatment protocol. Seventy 4-week-old male B6C3F1 mice constituted each treatment group. Of these mice, 35 were initiated by treatment with diethylnitrosamine (DENA) (10 mg/L) in the drinking water for 4 weeks. The remaining 35 received deionized drinking water. Each group was subsequently treated with one of two concentrations of CHCl3, 1,1-DCE, or 1,2-DCE in drinking water for 52 weeks. An additional group received phenobarbital (PB) (500 mg/L) and served as the positive control for liver tumor promotion. Mice were sampled after 24 weeks (10 mice) and 52 weeks (25 mice). At sampling, liver and lung tumors were detected. None of the compounds increased the number or incidence of lung or liver tumors by themselves. PB promoted liver tumor formation (but not lung tumors) in the DENA-initiated mice. 1,1-DCE and 1,2-DCE did not affect the incidence or number of liver or lung tumors in the DENA-initiated animals. CHCl3, however, inhibited liver and lung tumorigenesis in the DENA-initiated mice.
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PMID:Carcinogenicity of chlorinated methane and ethane compounds administered in drinking water to mice. 381 40

The modifying effects of antioxidants were examined in a carcinogenesis system after N,N-dibutylnitrosamine treatment. Male F344 rats were given 0.05% N,N-dibutylnitrosamine in their drinking water for 4 wk and then treated with basal diet containing 2% butylated hydroxyanisole (BHA), 1% butylated hydroxytoluene (BHT) with 7 ppm vitamin K, 0.8% ethoxyquin, 5% sodium L-ascorbate, 5% sodium erythorbate, or no added chemical for 32 wk. BHA enhanced forestomach carcinogenesis but did not enhance esophageal carcinogenesis. BHT enhanced esophageal carcinogenesis but did not enhance forestomach carcinogenesis. Ethoxyquin significantly enhanced esophageal tumorigenesis. Neither esophageal nor forestomach carcinogenesis was affected by the other antioxidants evaluated. BHA significantly increased DNA synthesis of the forestomach epithelium, whereas BHT tended to increase that of the esophageal epithelium. Thus, BHA and BHT showed different modifying responses in carcinogenesis of the esophagus and forestomach.
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PMID:Different modifying response of butylated hydroxyanisole, butylated hydroxytoluene, and other antioxidants in N,N-dibutylnitrosamine esophagus and forestomach carcinogenesis of rats. 382

Six groups of inbred male WF rats were castrated at 40 days of age. Group 1 was given no further treatment; groups 3-6 received sc implantations of 5.0 mg diethylstilbestrol [(DES) CAS: 56-53-1]. At 50-55 days of age, groups 5 and 6 were given drinking water containing 5.0 mg N-nitrosobutylurea [(NBU) CAS: 869-01-2] per day for 30 days. After the termination of NBU treatment, groups 2, 4, and 6 were given 3-amino-1H-1,2,4-triazole (AT), considered an inhibitor of hydroperoxidases, in the drinking water throughout the experiment. Castrated male rats or rats castrated and treated with AT alone developed neither hepatic tumors nor pituitary tumors. The hepatic tumor incidence, the size and total number of hepatic tumors, and the mean liver weight were significantly reduced in rats given the DES-NBU combination and slightly reduced in rats given DES alone when AT was administered. In contrast, AT treatment did not change the pituitary tumor incidence and the mean pituitary weight. The thyroid gland weights were approximately 7-44 times greater in AT-treated groups than those in each corresponding control group. These data indicate that AT inhibited hepatic but not pituitary tumorigenesis and caused enlargement of the thyroid gland. The present study, therefore, provides evidence that the metabolic activation of DES by oxidation is involved in rat liver carcinogenesis.
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PMID:Inhibition by 3-amino-1H-1,2,4-triazole of hepatic tumorigenesis induced by diethylstilbestrol alone or combined with N-nitrosobutylurea in WF rats. 385 99

Effects of phenobarbital [(PB) CAS: 50-06-6], a systemic tumor promoter, on carcinogenesis initiated by the broad-spectrum carcinogen N-nitroso-N-methylurea [(NMU) CAS: 684-93-5] were investigated in F344/NCr rats. Single and divided doses of NMU were evaluated for this purpose in 4-week-old rats of both sexes. Rats received iv injections of either 0.2 mmol NMU/kg (body wt) once or 0.05 mmol NMU/kg (body wt) for 4 weeks (1 injection/wk), followed by or concurrently with PB (0.05% in drinking water) that was continued until the termination of the experiment. Half the rats were killed at 52 weeks and survivors at 80 weeks. At 52 weeks, PB given subsequent to NMU or concurrently with divided doses of NMU significantly enhanced the incidence of thyroid follicular tumors only in male rats. This sex difference in thyroid tumorigenesis was somewhat less pronounced in animals killed at 80 weeks. Only 1 liver cell adenoma occurred in males and none in females given NMU alone. PB given concurrently with divided doses of NMU enhanced the yield of hepatocellular foci/cm2 but had no significant effect on hepatic tumor development. Subsequent exposure to PB, however, significantly promoted hepatocarcinogenesis in rats of both sexes given NMU in divided doses; 50% of males and 40% of females given NMU (0.05 mmol/kg, administered four times) followed by PB had hepatocellular adenomas and carcinomas by 80 weeks. PB did not affect the incidence of any other kind of neoplasms seen in NMU-initiated or control rats. These lesions included squamous cell neoplasms of the skin, oropharynx, and forestomach; nonsquamous epithelial tumors of mammary gland, pituitary body, intestinal mucosa, and urinary bladder; tumors of the central and peripheral nervous system; and mesenchymal tumors of the kidney. A sequence of multiple low doses of NMU appeared to be a convenient and useful systemic, multitissue, tumor-initiation regimen for systematic investigation of organ-specific tumor promotion in rats.
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PMID:N-Nitroso-N-methylurea initiation in multiple tissues for organ-specific tumor promotion in rats by phenobarbital. 386 12

Our recent studies have shown that ellagic acid, a naturally occurring dietary plant phenol, protects BALB/c mice against 3-methylcholanthrene-induced skin tumorigenesis. To further elucidate the mechanism of the antineoplastic action of ellagic acid its effect on hepatic and pulmonary benzo[a]pyrene (BP) metabolism, cytochrome P-450-dependent monooxygenases and glutathione S-transferase activities were studied in BALB/c mice. Chronic oral feeding of the compound in drinking water (0.3 mg/l for 16 weeks) or acute intraperitoneal administration (50 mg/kg for five consecutive days) of ellagic acid resulted in 20-25% decreases in hepatic and pulmonary cytochrome P-450 levels. Hepatic and pulmonary aryl hydrocarbon hydroxylase and 7-ethoxycoumarin O-deethylase activities in both groups of ellagic acid-treated animals were 33-52% and 28-43% lower than their respective non-ellagic acid-treated controls. Hepatic as well as pulmonary aminopyrine N-demethylase and epoxide hydrolase activities were unchanged in both groups of ellagic acid-treated mice. Hepatic glutathione S-transferase activity towards BP-4,5-oxide or 1-chloro-2,4-dinitrobenzene as substrates was found to be enhanced 51-79% and 38-58% in both groups of animals. H.p.l.c. analysis of organic solvent-soluble metabolites of BP by liver and lung microsomes indicated a substantial inhibition of diol formation (including BP-7,8-diol), as well as of phenols and quinones. In liver, these inhibitory effects were more pronounced after oral feeding than after intraperitoneal administration. Our results indicate that both acute and chronic administration of ellagic acid inhibits BP metabolism and/or enhances glutathione S-transferase activity. Thus the modulation of polycyclic aromatic hydrocarbon metabolism by ellagic acid may be related to the anticarcinogenic effects of this compound.
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PMID:Effect of ellagic acid on hepatic and pulmonary xenobiotic metabolism in mice: studies on the mechanism of its anticarcinogenic action. 387 74

Dose-response studies were undertaken to investigate the enhancing activity of potassium bromate (KBrO3), a food additive, on renal tumorigenesis initiated by N-ethyl-N-hydroxyethylnitrosamine (EHEN). A total of 180 male 6-week-old F344 rats were divided into 12 groups. EHEN was given in the drinking water for the first 2 weeks at a concentration of 500 ppm for initiation of carcinogenesis. Thereafter, the rats were treated orally either with KBrO3 at a concentration of 500, 250, 125, 60, 30 or 15 ppm, or with potassium bromide (KBr) at a concentration of 1750 or 350 ppm for 24 weeks. The mean numbers of kidney dysplastic foci were significantly increased in a dose-related manner in rats treated with more than 30 ppm KBrO3. The mean number of renal cell tumors was significantly higher after treatment with KBrO3 at the highest concentration of 500 ppm. On the other hand, KBr had no effect. It was concluded that KBrO3 at doses higher than 30 ppm in the drinking water has an enhancing effect on renal tumorigenesis.
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PMID:Dose-related enhancing effect of potassium bromate on renal tumorigenesis in rats initiated with N-ethyl-N-hydroxyethyl-nitrosamine. 392 54


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