UMLS:C0596263 - FACTA Search

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Query: UMLS:C0596263 (carcinogenesis)
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Tris(2-ethylhexyl)phosphate is one of a family of triakyl phosphates that have been widely used as fire retardants and plasticizers. Another triakyl phosphate, tris(2,3-dibromopropyl)phosphate (Tris-BP), once used as a flame retardant in children's sleepwear, has been shown to be carcinogenic, but tris(2-ethylhexyl)phosphate has not been previously studied. Tris(2-ethylhexyl)phosphate, a clear, viscous liquid, is used as a component of vinyl stabilizers, grease additives, and flame-proofing compositions; however, it is used primarily as a plasticizer for vinyl plastic and synthetic rubber compounds. In 1974, approximately 3 million pounds of tris(2-ethylhexyl)phosphate was produced in the United States; imports during that year were negligible. Substantial human exposure probably occurs during production of tris(2-ethylhexyl)phosphate and during the manufacture and use of products containing it, but data on the magnitude of exposure are not available. Two-year toxicology and carcinogenesis studies of tris(2-ethylhexyl)phosphate were conducted by administering the test chemical in corn oil by gavage, 5 days per week for 103 weeks, to groups of 50 male and 50 female F344/N rats and B6C3F1 mice. Male rats received doses of 2,000 or 4,000 mg/kg body weight, female rats received 1,000 or 2,000 mg/kg, and male and female mice received 500 or 1,000 mg/kg. Fifty vehicle control animals of each sex and species received 10 ml/kg body weight (rats) or 3.3 ml/kg (mice) corn oil by gavage on the same schedule. Inflammation of the gastric mucosa in mice and mild weight depression in rats and mice were the only dose-related effects observed in the preliminary studies. In the 2-year studies, survival rates and mean body weight gains of dosed female rats and dosed mice were comparable to those of their perspective controls. Survival rates of dosed male rats were comparable to that of the vehicle controls, but body weight gains were depressed. One nonneoplastic lesion, follicular cell hyperplasia of the thyroid, was observed at increased incidences in dosed male and female mice. Two compound-related increased incidences of neoplasms could not be discounted. In male rats, the incidence of pheochromocytoma of adrenal glands increased with dose (2/50, 4%; 9/50, 18%; 12/50, 24%). There were also two additional malignant pheochromocytomas in the high dose group. However, the incidence of adrenal pheochromocytoma in vehicle controls of this study (2/50, 4%) was low compared with the 25% incidence observed in two previous studies in this laboratory or the overall historical incidence of 18% observed throughout the Program, and thus the evidence of carcinogenicity was considered to be equivocal. In female mice, the incidence of hepatocellular carcinoma (0/48; 4/50; 7/50) in high dose animals (1,000 mg/kg) was significantly increased relative to that of the vehicle controls. Decreased incidences were observed for acinar cell adenomas of the pancreas in dosed male rats (14/50, 28%; 5/48, 10%; 2/49, 4%) and for fibroadenomas of the mammary glands in low dose female rats (11/50, 22%; 2/50, 4%; 7/50, 14%). Hemangiosarcomas of the circulatory system in male mice (7/50, 14%; 0/50; 1/49, 2%) and lymphomas of the hematopoietic system in female mice (14/49, 29%; 10/50, 20%; 6/50, 12%) were decreased compared with vehicle controls. A decrease in the incidence of lymphomas and an increased incidence of carcinomas of the liver in female mice (both seen in this study) were observed in studies of di(2-ethylhexyl)adipate. Increased incidences of liver carcinomas and decreased incidences of mammary fibroadenomas were observed also in female rats in the di(2-ethylhexyl)phthalate studies. A possible link among these three chemicals may be metabolic conversion to 2-ethylhexanol. Tris(2-ethylhexyl)phosphate was not mutagenic in Salmonella typhimurium strains TA98, TA100, TA1535, or TA1537 in the presence or absence of 9000 x g (S9) fractions from Aroclor 1254-induced Sprague-Dawley rat or Syrian hamster liver. An audit of the experimental data from these carcinogeneoclor 1254-induced Sprague-Dawley rat or Syrian hamster liver. An audit of the experimental data from these carcinogenesis studies was conducted by the National Toxicology Program. No data discrepancies were found that significantly influenced the final interpretations of these experiments. Under the conditions of these studies, a comparison of concurrent and historical controls indicated that there was equivocal evidence of carcinogenicity in male F344/N rats receiving 2,000 and 4,000 mg/kg tris(2-ethylhexyl)phosphate, as evidenced by increased incidences of pheochromocytomas of the adrenal glands. There was no evidence of carcinogenicity in female F344/N rats or in male B6C3F1 mice receiving tris(2-ethylhexyl)phosphate. There was some evidence of carcinogenicity in female B6C3F1 mice that received 1,000 mg/kg tris(2-ethylhexyl)phosphate, as shown by an increased incidence of hepatocellular carcinoma. Tris(2-ethylhexyl)phosphate was associated with increased incidences of follicular cell hyperplasia of the thyroid gland in male and female B6C3F1 mice. Synonyms and Trade Names: TOF; trioctyl phosphate; phosphoric acid tri(2-ethylhexyl) ester; Flexolreg. TOF; Kronitexreg.
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PMID:NTP Toxicology and Carcinogenesis Studies of Tris(2-ethylhexyl)phosphate (CAS No. 78-42-2) In F344/N Rats and B6C3F1 Mice (Gavage Studies). 1274 80

Propylene is used as a starting material in the production of polypropylene plastics and various other chemicals, including acrylonitrile, isopropyl alcohol, propylene oxide, butyraldehyde, cumene, dodecane, nonene, and allyl chloride. The major derivatives are polypropylene (25%), acrylonitrile (15%), isopropyl alcohol (10%), and propylene oxide (10%). It is also a valuable feed-stock chemical for the production of gasoline. Other miscellaneous applications include use as a starting material for polymerization reactions to form vinyl chloride copolymers and low-molecular-weight homopolymers that are used as additives in lubricating oils and in the manufacture of hydroquinone. The chemical is also used as an aerosol propellant or component. The major end uses of propylene are in the production of fabricated plastics (50%) and fibers (15%). Toxicology and carcinogenesis studies of propylene (greater than 99% pure) were conducted by exposing groups of 50 F344/N rats and 49 or 50 B6C3F1 mice of each sex to propylene in air by inhalation at concentrations of 5,000 or 10,000 ppm, 6 hours per day, 5 days per week, for 103 weeks. Other groups of 50 rats and 50 mice of each sex in chambers received air only on the same schedule and served as chamber controls. The highest concentration of propylene that was considered safe for these studies was 10,000 ppm because of the risk of explosion that can occur at higher concentrations. The survival of exposed and control rats and mice was comparable. Throughout most of the studies, mean body weights of exposed male and female rats were slightly lower (0%-5%) than those of the controls, but the decrements were not concentration related. After week 59 of the study, mean body weights of 10,000-ppm male mice were usually slightly lower (5%) than those of the controls, whereas those in other exposed groups of male and female mice were generally comparable with those of the controls. No compound-related adverse clinical signs were observed in either species. An increased incidence of squamous metaplasia of the nasal cavity was observed in female rats exposed at the 5,000-ppm and 10,000-ppm concentrations (control, 0/49; low, 15/50; high, 6/50) and in male rats exposed at 5,000 ppm (2/50; 19/50; 7/50). Epithelial hyperplasia of the nasal cavity was increased in female rats exposed at the 10,000-ppm concentration (0/49; 4/50; 9/50); the incidences in male rats were 2/50, 2/50, and 5/50. Inflammation of the nasal cavity, characterized by an influx of lymphocytes, macrophages, and granulocytes into the submucosa and by granulocytes into the lumen, occurred at increased incidences in low concentration and high concentration male rats and in high concentration female rats. Chronic focal inflammation of the kidneys occurred at an increased incidence in low concentration and high concentration mice of each sex. Hemangiosarcomas were found in one low dose male mouse (liver), two high dose male mice (spleen), and three high dose female mice (subcutis, spleen, and uterus). Hemangiomas were found in one low dose and in one high dose female mouse (liver). Vascular tumors were not found in control mice of either sex. The low incidences of vascular tumors and their occurrence in a variety of organs suggest that they are not related to administration of propylene. The occurrence of uterine endometrial stromal polyps in female mice showed a positive trend (P<0.05; 0/47; 0/47; 3/48); the incidence in the 10,000-ppm group was not significantly greater than that in the concurrent control group, but the incidence was higher than the mean historical control rate (22/2,411, 0.9%) and was within the range (0%-6%) observed in studies throughout the Carcinogenesis Program. The occurrence of endometrial stromal polyps in three high concentration female mice was not considered to be clearly related to exposure to propylene. The incidence of male mice with alveolar/bronchiolar adenomas or carcinomas (combined) occurred with a negative trend (P<0.05; 16/50; 4/49; 7/50), and the reduced incidences in both exposed groups wegative trend (P<0.05; 16/50; 4/49; 7/50), and the reduced incidences in both exposed groups were less (P<0.05) than that in the control group. The control incidence of these tumors in an inhalation study conducted concurrently at the same laboratory was similar (15/50), suggesting a possible exposure-related decrease. The biologic significance of this decrease in male mice is difficult to assess; the incidences seen in these control and exposed animals are within the range of incidences (2&percnt;-34&percnt;; mean, 16.7&percnt;) observed in control male mice in other studies throughout the Carcinogenesis Program. An audit of the experimental data was conducted for these carcinogenesis studies on propylene. No data discrepancies were found that influenced the final interpretations. Under the conditions of these studies, there was no evidence of carcinogenicity in male and female F344/N rats or in male and female B6C3F1 mice exposed to propylene by inhalation at concentrations of 5,000 or 10,000 ppm for 103 weeks. In the nasal cavity, propylene induced squamous metaplasia of the respiratory epithelium in male and female rats and epithelial hyperplasia in female rats. Synonyms: propene; methylethylene; methylethene
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PMID:NTP Toxicology and Carcinogenesis Studies of Propylene (CAS No. 115-07-1) in F344/N Rats and B6C3F1 Mice (Inhalation Studies). 1274 82

1,3-Butadiene is used as an intermediate in the production of elastomers, polymers, and other chemicals. Of the 1,3-butadiene used in 1978, 44% was used to manufacture styrene-butadiene rubber (a substitute for natural rubber, produced by copolymerization of 1,3-butadiene with styrene), and 19% was used to produce polybutane elastomer (a substance that increases resistance of tire products to wear, heat degradation, and blowouts). Chloroprene monomer, derived from 1,3-butadiene, is used exclusively to manufacture neoprene elastomers for non-tire and latex applications. Commercial nitrile rubber, used largely in rubber hoses, seals, and gaskets for automobiles, is a copolymer of 1,3-butadiene and acrylonitrile. Acrylonitrile- butadiene- styrene resins, usually containing 20%-30% 1,3-butadiene by weight, are used to make parts for automobiles and appliances. Other polymer uses include specialty polybutadiene polymers, thermoplastic elastomers, nitrile barrier resins, and K resins(R). 1,3-Butadiene is used as an intermediate in the production of a variety of industrial chemicals, including two fungicides, captan and captofol. It is approved by the U.S. Food and Drug Administration for use in the production of adhesives used in articles for packaging, transporting, or holding food; in components of paper and paperboard that are in contact with dry food; and as a modifier in the production of semigrid and rigid vinyl chloride plastic food-contact articles. No information was located on the levels of monomer or on its elution rate from any of the commercially available polymers. It is not known if unreacted 1,3-butadiene migrated from packaging materials. Male and female B6C3F1 mice were exposed to air containing 1,3-butadiene (greater than 99% pure) at concentrations of 0-8,000 ppm in 15-day and 14-week inhalation studies. In the 15-day studies, survival was unaffected by dose, and no pathologic effects were observed; slight decreases in mean body weight occurred at the high concentrations. In the 14-week studies, mean body weight gain decreased with dose, and survival in the 5,000-ppm and 8,000-ppm groups of males was markedly reduced; no other compound-related effects were reported. Inhalation carcinogenesis studies of 1,3-butadiene were conducted by exposing groups of 50 male and female B6C3F1 mice 6 hours per day for 5 days per week to air containing the test chemical at concentrations of 0 (chamber controls), 625, or 1,250 ppm. These studies were planned for 103-week exposures but were terminated at week 60 for male mice and week 61 for female mice because of the rapidly declining survival, primarily due to neoplasia. Body weights were not affected by 1,3-butadiene. Significantly increased incidences of neoplasms at multiple sites were observed in mice exposed to 1,3-butadiene. Hemangiosarcomas of the heart occurred at increased incidences in exposed males and females (male: control, 0/50; low dose, 16/49; high dose, 7/49; female: 0/50; 11/48; 18/49). Hemangiosarcomas were also observed in the peritoneal cavity (one high dose male), subcutaneous tissue (two low dose females), and liver (one high dose female). Malignant lymphomas, diagnosed as early as week 20, were observed at increased incidences in exposed male and female mice (male: 0/50; 23/50; 29/50; female: 1/50; 10/49; 10/49). Alveolar/bronchiolar adenomas and alveolar/bronchiolar (both separately and combined) occurred at increased incidences in exposed male and female mice (combined incidences -- male: 2/50; 14/49; 15/49; female: 3/49; 12/48; 23/49). Epithelial hyperplasia of the forestomach occurred at increased incidences in dosed mice (male: 0/49; 5/40; 7/44; female: 0/49; 5/42; 9/49). Papillomas of the forestomach occurred in low dose male and in low dose and high dose female mice (male: 0/49; 5/40; 0/44; female: 0/49; 4/42; 10/49). Squamous cell carcinomas of the forestomach were observed in dosed mice (male: 0/49, 2/40, 1/44; female: 0/49, 1/42, 1/49). Acinar cell carcinomas of the mammary gland were observed at an increased incidence in high dose female reased incidence in high dose female mice (0/50; 2/49; 6/49); adenosquamous carcinomas were found in four low dose females. The incidences of granulosa cell tumors of the ovary were increased in dosed females (0/49; 6/45; 12/48). A granulosa cell carcinoma was observed in another high dose female. Gliomas were observed in two 68- to 69-week-old low dose and one high dose male mice; brain tumors are uncommon even in 2-year old mice. Liver necrosis occurred at increased incidences in dosed male and low dose female mice (male; 1/50, 8/49, 8/49; female: 6/50, 15/47, 6/49). Hepatocellular adenomas or carcinomas (combined) were observed at an increased incidence in high dose female mice (0/50, 2/47 5/49). No neoplastic lesions of the nasal cavity were observed at any dose level. The following nonneoplastic lesions of the nasal cavity occurred in mice exposed at 1,250 ppm: chronic inflammation (male, 35/50; female, 2/49); fibrosis (male, 33/50; female, 2/49); cartilaginous metaplasia (male, 16/50; female, 1/49); osseous metaplasia (male, 11/50; female, 2/49); and atrophy of the sensory epithelium (male, 32/50). No nonneoplastic lesions of the nasal cavity were found in the controls. The incidence of testicular atrophy (0/50, 19/49, 11/48) or ovarian atrophy (2/49, 40/45, 40/48) was increased in exposed male or female mice. An audit of the experimental data from these studies on 1,3-butadiene was conducted by the National Toxicology Program. No data discrepancies were found that influenced the final interpretation of these experiments. Under the conditions of these studies, there was clear evidence of carcinogenicity for 1,3-butadiene in male and female B6C3F1 mice, as shown by increased incidences and early induction of hemangiosarcomas of the heart, malignant lymphomas, alveolar/bronchiolar adenomas and carcinomas, and papillomas of the stomach in males and females; and of acinar cell carcinomas of the mammary gland, granulosa cell tumors of the ovary, and hepatocellular adenomas and adenomas or carcinomas (combined) in females. 1,3-Butadiene was associated with nonneoplastic lesions in the respiratory epithelium, liver necrosis, and testicular or ovarian atrophy. Synonyms: butadiene; biethylene; bivinyl; divinyl; erythrene; vinylethylene; pyrrolylene
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PMID:NTP Toxicology and Carcinogenesis Studies of 1,3-Butadiene (CAS No. 106-99-0) in B6C3F1 Mice (Inhalation Studies). 1274 15

Dimethylvinyl chloride is a clear colorless liquid, which, because of its volatility and flammability at room temperature, is a significant fire hazard. It has a boiling point of 68.1 degrees C (155 degrees F) and a density at 20 degrees C of 0.919 g/ml. Dimethylvinyl chloride is a byproduct in the production of 3-chloro-2-methylpropene by the chlorination of isobutene. It is not known to be produced in the United States for other than laboratory purposes. This chemical was nominated for toxicologic studies because of its reported presence in ambient air in the Baltimore area and was selected for toxicologic characterization because of its structural similarity to the known animal and human carcinogen, vinyl chloride monomer. Toxicology and carcinogenesis studies of dimethylvinyl chloride (96%-98% pure), a structural analog of vinyl chloride monomer, a known human carcinogen, by administered dimethylvinyl chloride in corn oil by gavage to groups of 50 male and 50 female F344/N rats and B6C3F1 mice at doses of 0, 100, or 200 mg/kg body weight 5 days per week for 102 or 103 weeks. The selection of these doses was based on results of 13-week studies, which included depression of body weight at doses of 500 mg/kg or above in rats as well as histopathologic changes intestinal epithelium, bone marrow, hepatocytes, and the testes at doses of 250 mg/kg and above; doses in mice were selected on the basis of histopathologic changes in lymphopoietic cells, liver, pancreatic islets, ovary, testis, and spleen, with changes being most prominent at doses of 500 mg/kg and above. In the 2-year studies, body weights of rats and mice given 100 mg/kg were comparable to those of the vehicle controls except for the last few weeks in mice when body weights were markedly lower than those for the vehicle controls. At 200 mg/kg, the mean body weights of rats and mice were progressively decreased relative to those of vehicle controls, with the significant departure from vehicle controls occurring somewhat earlier in males than in females. Survival of vehicle control rats and mice was comparable to historical values; however, survival of dosed male and female rats was significantly lower than that of vehicle controls, with the incidence of mortality being more severe at the high dose than at the low dose. There were no survivors in the high dose group of male rats after week 85 or in the high dose group of female rats after week 97. Survival was significantly lower among dosed male and female mice compared with vehicle controls. In the absence of toxicological findings that would explain the early deaths, it is assumed that the high incidence of tumors and chemical-related toxicity contributed to the decreased survival of dosed rats and mice. In rats, the severity and incidence of nonneoplastic lesions were minimal; these lesions included necrosis of the duodenum and epithelial hyperplasia at the sites of tumor formation--the nasal cavity, esophagus, and forestomach. In mice, the severity of nonneoplastic lesions was also minimal; the lesions included necrosis of the liver, bone marrow granulocytic hyperplasia, and inflammation of the nasal cavity (small number, females only.) Several types of neoplastic lesions occurred with significantly increased incidences in dosed animals as shown in the following table (see page 11 of Technical Report). Among rats, these lesions included malignant epithelial tumors of the nasal cavity and squamous cell tumors of the oral cavity, esophagus, and forestomach in males and females. The increased number of fibroadenomas of the mammary gland in female rats may have been related to dimethylvinyl chloride administration. The lack of a clear dose-response relationship for certain tumors in rats is considered to be related to the increased number of early deaths observed in the high dose groups. Among dosed mice, there were significantly increased incidences of squamous cell carcinomas of the forestomach (both sexes), squamous cell papillomas of the forestomach (males), and squamous cell carcinomas of the preputial gla preputial gland (males). The increased incidence of papillary adenomas of the harderian gland and alveolar/bronchiolar adenomas or carcinomas in female mice may have been related to administration of dimethylvinyl chloride. Limited metabolism studies of 14C-labeled dimethylvinyl chloride were conducted in male F344/N rats and B6C3F1 mice. Single doses of 150 mg/kg were administered to rats for 1, 2, or 4 consecutive days. About 25&percnt; of the administered doses was exhaled as carbon dioxide; this amount was independent of the number of doses administered. Another 25&percnt;-35&percnt; of the administered dose was exhaled; 96&percnt; of this parent was material. Approximately 35&percnt; and 6&percnt; were excreted in the urine and feces, respectively. The elimination half-life of radioactive label was 3-4 days for the liver and kidney, the two organs containing the greatest amounts of the administered dose. In mice, a much smaller fraction of the dose was exhaled and a larger proportion was excreted in urine compared with rats. Dimethylvinyl chloride was not mutagenic in four strains ofSalmonella typhimurium with or without metabolic activation, but it was mutagenic in the mouse lymphoma L5178Y/TK± assay in the absence of metabolic activation. Sister-chromatid exchanges were induced in Chinese hamster ovary cells with and without metabolic activation, but there was no increase in chromosomal aberrations. When fed to Drosophila, dimethylvinyl chloride induced significant increases in the frequencies of both sex-linked recessive lethal mutations and reciprocal translocations. Studies of the immunotoxicity of dimethylvinyl chloride were conducted in which female B6C3F1 mice received daily oral doses of 0, 50, 100, 200, or 400 mg dimethylvinyl chloride per kilogram body weight. Compound-related increases in susceptibility to bacterial infection and decreases in macrophage cytostasis were observed at all doses. At the highest dose, the decreased resistance to bacterial and viral challenge could be related to alterations in specific immune function. However, the increased mortality in rats and mice in the 2-year studies was not relatable to infectious processes. An audit of the experimental data was conducted for these2-year toxicology and carcinogenesis studies on dimethylvinyl chloride. No data discrepancies were found that influenced the final interpretations. Under the conditions of these 2-year gavage studies, there was clear evidence of carcinogenicity of dimethylvinyl chloride for both sexes of F344/N rats and B6C3F1 mice. This was based on increased incidences of neoplasms of the nasal cavity, oral cavity, esophagus, and forestomach of male and female F344/N rats. B6C3F1 mice showed increased incidences of squamous cell neoplasms of the forestomach in males and females and squamous cell carcinomas of the preputial gland in males. Synonym: 1-chloro-2-methylpropene
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PMID:NTP Toxicology and Carcinogenesis Studies of Dimethylvinyl Chloride (1-Chloro-2-Methylpropene) (CAS No. 513-37-1) in F344/N Rats and B6C3F1 Mice (Gavage Studies). 1274 37

A carcinogenesis bioassay of butyl benzyl phthalate, a plasticizer for vinyl chloride plastics, was accomplished by feeding diets containing 6,000 or 12,000 ppm of the phthalate to groups of 50 F344/N rats and 50 B6C3F1 mice of each sex for 28 to 103 weeks. Mean body weights of dosed female rats and mice of each sex were lower than those of the control animals throughout most of the study. After week 14, an increasing number of dosed male rats died as a result of an unexplained internal hemorrhaging, and all surviving male rats were killed at week 29 to 30. Because of compound-related mortality, butyl benzyl phthalate was not adequately tested for carcinogenicity in male F344/N rats. Mononuclear cell leukemias occurred at a statistically significant (P=0.011) increased incidence in the high-dose group of female rats when compared with the control group and with a significantly (P=0.006) increasing trend (controls 7/49, 14%; low-dose 7/49, 14%; high-dose 18/50, 36%). The incidence in the high-dose group and the overall trend remained statistically significant (P=0.008 and P=0.019) when compared with the historical incidence for F344/N female rats with leukemia at this laboratory (77/ 399, 19%). Further, this leukoproliferation was generally characterized by splenomegaly and often by hepatomegaly. Administration of butyl benzyl phthalate was not associated with increased incidences of any type of tumor among male or female mice. Tumor rates were decreased in female rats for fibroadenomas of the mammary glands (20/49, 14/49, 9/50) and in male mice for lymphomas of the hematopoietic system (13/50, 11/49, 4/50) and for alveolar/bronchiolar adenomas or carcinomas (17/50, 11/49, 8/50). Under the conditions of this bioassay, butyl benzyl phthalate was probably carcinogenic for female F344/N rats, causing an increased incidence of mononuclear cell leukemias. The male F344/N rat study was considered inadequate for evaluation due to compound-related toxicity and early mortality. Butyl benzyl phthalate was not carcinogenic for B6C3F1 mice of either sex. Levels of Evidence of Carcinogenicity: Male Rats: Inadequate Study Female Rats: Positive Male Mice: Negative Female Mice: Negative Synonyms: BBP; benzyl butyl phthalate; phthalic acid; benzyl butyl ester; Santicizer 160
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PMID:Carcinogenesis Bioassay of Butyl Benzyl Phthalate (CAS No. 85-68-7) in F344/N Rats and B6C3F1 Mice (Feed Study). 1277 22

Di(2-ethylhexyl)adipate is a plasticizer used to give flexibility to vinyl plastics. A carcinogenesis bioassay was conducted by feeding diets containing 12,000 or 25,000 ppm of di(2-ethylhexyl)adipate to groups of 50 male and 50 female F344 rats and 50 male and 50 female B6C3F1 mice for 103 weeks. Groups of 50 undosed rats and mice of each sex served as controls. All surviving animals were killed at 104 to 107 weeks. Mean body weights of high-dose rats and mice of either sex were lower than those of the controls throughout the study. Compound administration was not associated with tumor formation in F344 rats of either sex. Hepatocellular carcinomas or adenomas occurred in mice of both sexes in a dose-related fashion at incidences that were significantly higher for high-dose males and for low- and high-dose females than those in the controls. When compared with the incidence in historical laboratory control mice, however, the liver tumors in male mice could not be clearly related to compound administration. Under the conditions of this bioassay, di(2-ethylhexyl)adipate was not carcinogenic for F344 rats. Di(2-ethylhexyl)adipate was carcinogenic for female B6C3F1 mice, causing increased incidences of hepatocellular carcinomas, and was probably carcinogenic for male B6C3F1 mice, causing hepatocellular adenomas. Levels of Evidence of Carcinogenicity: Male Rats: Negative Female Rats: Negative Male Mice: Positive Female Mice: Positive Synonyms: bis(2-ethylhexyl)adipate; DEHA; octyl adipate; dioctyl adipate; DOA
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PMID:Carcinogenesis Bioassay of Di(2-ethylhexyl)adipate (CAS No. 103-23-1) in F344 Rats and B6C3F1 Mice (Feed Study). 1277 23

CD-1 is the outbred mouse line most often used in toxicology and carcinogenicity bioassays. A literature survey revealed a relatively high (21.8%) incidence of spontaneous lung tumors in these mice, and a susceptibility to lung tumorigenesis induced by vinyl chloride, styrene or benzene inhalation that is not seen in B6C3F1 or C57BL/6 mice, or in rats and hamsters. As the pulmonary adenoma susceptibility 1 (Pas1) locus is the major determinant of genetic susceptibility to lung tumorigenesis in mice, we analyzed CD-1 mice for genetic polymorphisms of the Kras2 and Pthlh genes, which are tightly linked with the Pas1 locus. From 95 to 98% of CD-1 mice carried the susceptibility allele at the Pas1 locus either at homozygosity or heterozygosity, providing a molecular genetic explanation for the high susceptibility of CD-1 mice to spontaneous and chemically induced lung tumorigenesis. These results may have implications for the risk assessment of chemicals in humans using experimental animals that display strain-specific lung tumorigenicity.
Carcinogenesis 2003 Jun
PMID:Outbred CD-1 mice carry the susceptibility allele at the pulmonary adenoma susceptibility 1 (Pas1) locus. 1280 61

Lipid peroxidation generates aldehydes, which react with DNA bases, forming genotoxic exocyclic etheno(epsilon)-adducts. E-bases have been implicated in vinyl chloride-induced carcinogenesis, and increased levels of these DNA lesions formed by endogenous processes are found in human degenerative disorders. E-adducts are repaired by the base excision repair pathway. Here, we report the efficient biological hijacking of the human alkyl-N-purine-DNA glycosylase (ANPG) by 3,N(4)-ethenocytosine (epsilonC) when present in DNA. Unlike the ethenopurines, ANPG does not excise, but binds to epsilonC when present in either double-stranded or single-stranded DNA. We developed a direct assay, based on the fluorescence quenching mechanism of molecular beacons, to measure a DNA glycosylase activity. Molecular beacons containing modified residues have been used to demonstrate that the epsilonC.ANPG interaction inhibits excision repair both in reconstituted systems and in cultured human cells. Furthermore, we show that the epsilonC.ANPG complex blocks primer extension by the Klenow fragment of DNA polymerase I. These results suggest that epsilonC could be more genotoxic than 1,N(6)-ethenoadenine (epsilonA) residues in vivo. The proposed model of ANPG-mediated genotoxicity of epsilonC provides a new insight in the molecular basis of lipid peroxidation-induced cell death and genome instability in cancer.
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PMID:Hijacking of the human alkyl-N-purine-DNA glycosylase by 3,N4-ethenocytosine, a lipid peroxidation-induced DNA adduct. 1476 49

Nitro-reduction by the vinyl halide radical cation CH2 = CH-X+* (X = Cl or Br) converts nitroaromatics into arylnitrenium ions, significant intermediates in carcinogenesis, and the present study reports on the scope and regioselectivity of this versatile reaction. The reaction is general for different kinds of substituted nitroaromatics; para/meta substitutents have little effect on the reaction while ortho substitutents result in low yields of arylnitrenium ions. The phenylnitrenium ion PhNH+ can be generated by chemical ionization (CI) of nitrobenzene using 1,2-dichloroethane as the reagent gas or by atmospheric pressure chemical ionization (APCI) of 1,2-dichloroethane solution doped with nitrobenzene. The chemical reactivities of the arylnitrenium ions include one-step ion/molecule reactions with nucleophiles ethyl vinyl ether and 1,3-dioxolanes, respectively, involving the direct formation of new CN bonds and synthesis of indole and benzomorpholine derivatives. The indole formation reaction parallels known condensed phase chemistry, while the concise morpholine-forming reaction remains to be sought in solution. The combination of collision-induced dissociation (CID) with novel ion/molecule reactions should provide a selective method for the detection of explosives such as TNT, RDX and HMX in mixtures using mass spectrometry. In addition to the reduction of the nitro group, reduction of methyl phenyl sulfone PhS(O)2Me to the thioanisole radical cation PhSMe+* occurs using the same chemical ionization reagent 1,2-dichloroethane. This probably involves an analogous reduction reaction by the reagent ion CH2 = CH-Cl+*.
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PMID:Generation of arylnitrenium ions by nitro-reduction and gas-phase synthesis of N-heterocycles. 1551 36

Because of potential exposure both in the workplace and from ambient air, the known carcinogen 1,3-butadiene (BD) is considered a priority hazardous air pollutant. BD and its 2-methyl analog, isoprene (ISO), are chemically similar but have very different toxicities, with ISO showing no significant carcinogenesis. Once released into the atmosphere, reactions with species induced by sunlight and nitrogen oxides convert BD and ISO into several photochemical reaction products. In this study, we determined the relative toxicity and inflammatory gene expression induced by exposure of A549 cells to BD, ISO, and their photochemical degradation products in the presence of nitric oxide. Gas chromatography and mass spectrometry analyses indicate the initial and major photochemical products produced during these experiments for BD are acrolein, acetaldehyde, and formaldehyde, and products for ISO are methacrolein, methyl vinyl ketone, and formaldehyde; both formed < 200 ppb of ozone. After exposure the cells were examined for cytotoxicity and interleukin-8 (IL-8) gene expression, as a marker for inflammation. These results indicate that although BD and ISO alone caused similar cytotoxicity and IL-8 responses compared with the air control, their photochemical products significantly enhanced cytotoxicity and IL-8 gene expression. This suggests that once ISO and BD are released into the environment, reactions occurring in the atmosphere transform these hydrocarbons into products that induce potentially greater adverse health effects than the emitted hydrocarbons by themselves. In addition, the data suggest that based on the carbon concentration or per carbon basis, biogenic ISO transforms into products with proinflammatory potential similar to that of BD products.
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PMID:Effects of 1,3-butadiene, isoprene, and their photochemical degradation products on human lung cells. 1553 32

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