Skin tumorigenic potential of benzanthrone: prevention by ascorbic acid.

Benzanthrone (BA) exposed occupational workers have been found to exhibit toxicological manifestations in the skin, thus it is quite likely that long term exposure may lead to skin tumorigenicity. Thus, attempts were made to elucidate the tumor initiating and promoting potentials of pure (PBA) and commercial benzanthrone (CBA). Additionally, the preventive role of ascorbic acid (AsA) was also assessed. PBA showed tumor initiating activity while CBA demonstrated tumor initiating as well as promoting activities in two-stage mouse skin tumor protocol. Further, prior treatment of AsA to PBA and CBA followed by twice weekly application of 12-o-tetradecanoyl phorbal myristate acetate (TPA) resulted into delayed onset of tumor formation and similarly single application of 7,12-dimethylbenz [α] anthracene (DMBA) followed by twice weekly application of AsA and CBA showed an increase in the latency period. Thus, AsA showed a protective effect against CBA promoted skin tumor. Furthermore, the topical application of CBA significantly increased the levels of xenobiotic enzymes. The animals topically treated with AsA along with topical application of CBA, restored all the impairment observed in enzyme activities. Thus, this study suggested that AsA can be useful in preventing PBA and CBA induced skin tumorigenicity.

Effects of ellipticine, flavone, and 7,8-benzoflavone upon 7,12-dimethylbenz[a]anthracene, 7,14-dimethyldibenzo[a,h]anthracene and dibenzo[a,h]anthracene initiated skin tumors in mice.

Varying doses of ellipticine (EL), flavone (FL), or 7,8-benzoflavone (78BF) were applied to mouse skin 5 min before an initiating dose of 10 nmol 7,12-dimethylbenz[a]anthracene (DMBA), 47.5 nmol 7,14-dimethylbenzo[a,h]anthracene (DDBA), or 200 nmol dibenzo[a,h]anthracene (DBA) and the development of skin tumors in the mice then promoted by topical applications of 2 micrograms 12-O-tetradecanoylphorbol-13-acetate (TPA). As expected, treatment with 78BF (37 nmol or 370 nmol) markedly inhibited the skin tumor initiation by DMBA (greater than 70%). High doses of FL (4500 nmol) or EL (410 nmol) also inhibited DMBA tumorigenesis (52% and 82%, respectively) but lower doses of FL (450 nmol) or EL (4.1 nmol) stimulated DMBA tumorigenesis (greater than 40%). As was the case with DMBA initiation, the higher doses of FL or EL inhibited DDBA skin tumorigenesis and the lower doses of these two modifiers stimulated the DDBA tumorigenesis. In contrast with the results with DMBA initiation, treatment with 78BF (370 nmol or 3700 nmol) slightly enhanced DDBA tumorigenesis (22% and 6%, respectively). Treatment with EL and FL at all doses tested stimulated DBA tumorigenesis (range 4-51%), while treatment with 370 nmol 78BF slightly stimulated DBA tumorigenesis (19%) and treatment with 3700 nmol slightly inhibited DBA tumorigensis (9%). The effects of a range of 78BF doses upon skin tumor initiation by 40 nmol DMBA were also investigated. While all doses of 78BF tested (0.37-370 nmol) inhibited the DMBA tumorigenesis, the dose response was not linear; treatment with 3.7 nmol 78BF resulted in more papillomas per mouse (12.20) than did treatment with either 0.37 nmol 78BF (8.70) or 37 nmol 78BF (5.97). It is concluded that modifiers such as 78BF, FL and EL may have a variable, dose-dependent effect upon skin tumor initiation by carcinogenic polycyclic arylhydrocarbons. Some implications of this proposal are discussed.

Effect of Japanese seaweed (Laminaria angustata) extracts on the mutagenicity of 7,12-dimethylbenz[a]anthracene, a breast carcinogen, and of 3,2'-dimethyl-4-aminobiphenyl, a colon and breast carcinogen.

Animal model studies suggest that diets containing Laminaria angustata, a brown seaweed commonly eaten in Japan, inhibit breast carcinogenesis. In order to identify the compound(s) in the seaweed responsible for tumor-inhibiting activity, we used Ames/mammalian microsome assay system to determine the antimutagenic (or anticarcinogenic) effect of various solvents and water extracts of Laminaria angustata. The antimutagenic effects of acetone, ether, chloroform, chloroform + methanol, hot water and cold water extracts on the mutagenicity induced by 7,12-dimethylbenz[a]anthracene (DMBA), a breast carcinogen, and 3,2'-dimethyl-4-aminobiphenyl (DMAB), a colon and breast carcinogen, was studied using the Salmonella typhimurium strains TA98 and TA100. All extracts were nonmutagenic in both bacterial tester strains. The addition of 10-100 mg solvent extracts of seaweed/plate greatly inhibited DMAB-induced mutagenicity in both tester strains (80-96% inhibition) and DMBA-induced mutagenicity in TA100 (about 82%), whereas hot and cold water extracts produced a moderate inhibition in a dose-related manner in both strains.

Inhibitory effects of alpha- and beta-naphthoflavones on DMBA-induced anomalies in germ cells assessed by sperm abnormality assay.

Frequencies of abnormal sperms in B6C3F1 male mice were analyzed after injection with 7,12-dimethylbenz[a]anthracene (DMBA), alpha-naphthoflavone (alpha-NF or 7,8-benzoflavone), beta-naphthoflavone (beta-NF or 5,6-benzoflavone) and combinations of either alpha-NF and DMBA or beta-NF and DMBA. Either alpha-NF or beta-NF was injected 48 and 24 h before injecting mice twice with DMBA for 2 days at 24-h intervals. Prior injection of mice with alpha-NF and beta-NF was based on the assumption that enhanced activity of monooxygenase enzymes (P-450) in the mouse system so as to modify the metabolism of DMBA towards increased detoxification. Both flavones showed inhibitory effects in the genotoxic action of DMBA to the extent of 83% reduction by alpha-NF and 60% by beta-NF in the number of abnormal sperms as compared with those found in germ cells due to DMBA alone. compared with those found in germ cells due to DMBA alone.

The reduction of tumor initiating activity and cell mediated mutagenicity of dimethylbenz[a]anthracene by a copper coordination compound.

Cu(II) (3,5-diisopropyl salicylate)2 (CuDIPS) which is an anti-inflammatory copper coordination compound (mol. wt. 503) possessing superoxide dismutase (SOD) activity was tested to determine its effect on 7,12-dimethylbenz[a]anthracene (DMBA)-induced initiation of tumors in mouse skin and on mutagenicity to 6-thioguanine resistance in a mouse keratinocyte mediated Chinese hamster V-79 cell system. A single application of CuDIPS (0.4 mg/mouse) administered at a short interval before DMBA application when followed by 20 weeks of promotion by TPA reduced the mouse skin tumor yield by 55%. When DMBA-induced cell-mediated mutagenesis was tested in the presence of CuDIPS a significant reduction in the number of V-79 6-thioguanine resistant mutants was observed.

Anticarcinogenic effect of N6,O2'-dibutyryl cyclic adenosine 3':5'-monophosphate on 7,12-dimethylbenz(a)anthracene mammary tumor induction in the rat and its relationship to cyclic adenosine 3':5'-monophosphate metabolism and protein kinase.

A single intubation of 7,12-dimethylbenz(a)anthracene (DMBA) (20 mg in 1 ml sesame oil) to female Sprague-Dawley rats at 50 days of age produces primary mammary carcinomas in 80% of rats at 100 to 150 days of age. Administration of N6,O2'-dibutyryl cyclic adenosine 3':5'-monophosphate (DBcAMP) p.o. beginning at 1 day prior to DMBA intubation resulted in marked delay and reduction of tumor production: only 15% as many DBcAMP-treated rats had tumors as in the control group (DMBA only) with 60 days of delay in the first tumor appearance. DMBA-induced tumor production was preceded by changes in the cyclic adenosine 3':5'-monophosphate (cAMP) metabolism and protein kinase of the mammary gland. Within 24 hr post-DMBA intubation, the intracellular cAMP level and adenylate cyclase activity increased with an increase in type I isozyme of cAMP-dependent protein kinase, a form which has been associated with increased proliferative activity and a less differentiated cellular state in other tissues. The increases in cAMP level, adenylate cyclase activity, and the protein kinase activity were transient, and the values decreased to below the control values by Day 10 post-DMBA intubation. In mammary glands of rats that had received DBcAMP, the cAMP level and protein kinase isozyme pattern were similar to those of older rats that are no longer susceptible to the carcinogen. The inhibitory effect on DMBA-induced carcinogenesis may be related to the modifications that DBcAMP induces on cAMP level, adenylate cyclase activity, and cAMP-dependent protein kinase of the mammary gland.

[Effect of sulpiride and castration on mammary carcinogenesis caused by 7,12-dimethylbenzanthracene in the Wistar rat]. / Efectos del sulpiride y castración sobre la carcinogenesis mamaria por el 7,12-dimetilbenzantraceno (DMBA) en la rata Wistar.

DMBA exerts strong oncogenic activity on the mammary tissue of female Wistar rats, inducing neoplasms in 74% of the animals exposed to it. Most of the tumors obtained in this way are of an epithelial nature, and show histological characteristics of malignancy. The castration of animals which have been administered DMBA drastically reduces the appearance of tumors, but does not totally eliminate them. The joint administration of Sulpiride and DMBA neither modifies the incidence of mammarian tumors nor their nature and histology with respect to the tumors obtained from the administration of DMBA alone. Sulpiride does not modify the DMBA tumoral induction in castrated rats. The Sulpiride itself cannot induce mammarian tumors in Wistar rats, according to the Huggins experimental model (production of mammarian tumors in Wistar rats by the administration of DMBA). The stimulating diencephalic action of the secretion of prolactin with Sulpiride is not tumorogenical in the experimental model investigated.

Tumor initiation by 7,12-dimethylbenz[a]anthracene in dermal melanocytes of hamster: inhibition through 7,8-benzoflavone.

Initiation of dermal melanocytes by 7,12-dimethylbenz[a]-anthracene (DMBA) in the dorsal skin of Syrian golden hamsters was investigated for its sensitivity to inhibition by 7,8-benzoflavone (BF). Initiation was carried out by a single intragastric application of DMBA (50 mg/kg body weight) and melanoma development pursued with or without subsequent promotion through repeated topical administration of 12-O-tetradecanoylphorbol-13-acetate (40 nmol/animal, 3 X weekly). A single intragastric application of BF (200 mg/kg body weight) 2 h prior to DMBA resulted in a suppression of melanoma yields by approximately 70%. Further, there were indications that BF generally causes a decrease of melanoma rates and an increase of survival rates. The study provides a first mechanistic concept for melanoma initiation by DMBA. It shows that metabolic activation of DMBA (i) is prerequisite to initiation and (ii) has a similar molecular basis as in other target cells of DMBA, the essential pathway including the cytochrome P-448-dependent monooxygenase system.

Comparison of the effect of butylated hydroxytoluene on N-nitrosomethylurea and 7,12-dimethylbenz[a]-anthracene-induced mammary tumors.

The antioxidant butylated hydroxytoluene (BHT) when fed at a level of 0.3% in a defined semi-purified diet was found to decrease mammary tumor incidence in female Sprague-Dawley rats induced by 7,12-dimethylbenz[a]-anthracene (DMBA). however, no effect of BHT on tumor incidence was seen in animals consuming the same diet, under identical experimental conditions, but treated with the carcinogen nitrosomethylurea (NMU). Differences in effectiveness of BHT as a tumor inhibitor in the 2 model systems, and thoughts as to a possible mechanism of action with regard to BHT are discussed.

[Inhibition of the growth of 7,12-dimethylbenz(a)anthracene- and N-nitrosomethylurea-induced mammary gland neoplasms by methionine in rats]. / Tormozhenie metioninom razvitiia raka molochnoi zhelezy, indutsirovannogo 7,12-dimetilbenz(a)antratsenom i N-nitrozometilmochevinoi u krys.

The diets supplemented with 0.5% methionine inhibited the development of mammary adenocarcinomas induced in female rats with 7,12-dimethylbenz(a)anthracene and N-nitrosomethylurea by 3.8 and 2.3 times, respectively. Methionine produced no effect on the incidence of other new-growths. It is suggested that the mechanism by which methionine exerts an antineoplastic effect on mammary carcinomas is a consequence of its hypolipidemic and neurotropic activity.

Evidence that the effectiveness of antioxidants as inhibitors of 7,12-dimethylbenz(a) anthracene-induced mammary tumors is a function of dietary fat composition.

A study of tumor incidence and tumor growth rates in 7,12-dimethylbenz(a)anthracene-treated female Sprague-Dawley rats fed different types and amounts of dietary fat indicates that the difference in tumor incidence may be a reflection of marked differences in the growth of neoplastic clones to a palpable size within the time frame of the study. In addition, the observation is made that some antioxidants which inhibit tumor development in animals fed commercial rations are not effective when given in purified diets.

Inhibition of carcinogen-induced neoplasia by sodium cyanate, tert-butyl isocyanate, and benzyl isothiocyanate administered subsequent to carcinogen exposure.

The effects of sodium cyanate, tert-butyl isocyanate, and benzyl isothiocyanate on carcinogen-induced neoplasia were studied in experiments in which the test compound was fed starting 1 week following completion of carcinogen administrations. Under these conditions, all three test compounds exerted an inhibitory effect on the occurrence of 7,12-dimethylbenz(a)anthracene-induced neoplasia of the breast of Sprague-Dawley rats. In a second experiment model, sodium cyanate inhibited the occurrence of 1,2-dimethylhydrazine-induced neoplasia of the large bowel of female CF-1 mice. Thus, a new group of compounds has been identified which has inhibitory capacities against neoplasia when given subsequent to carcinogen exposure.

Antimutagenic effect of selenium on acridine orange and 7,12-dimethylbenz[alpha]anthracene in the Ames Salmonella/microsomal system.

The antimutagenic effects of selenium as sodium selenite were investigated using the Ames Salmonella/microsome mutagenicity test. The compounds examined were acridine orange and 7,12-dimethylbenz[alpha]anthracene. Selenium (22 ppm) reduced the number of histidine revertants caused by 20 microgram acridine orange and 20 microgram 7,12-dimethylbenz[alpha]anthracene by 52 and 74%, respectively. Increasing the quantity of selenium added to the plates further suppressed the mutagenicity of the test compounds. The antimutagenic effects of selenium cannot be explained by lethality of Salmonella typhimurium.

Selenium-mediated inhibition of 7,12-dimethylbenz[a]anthracene-induced mouse mammary tumorigenesis.

The effect of supplemental selenium on 7,12-dimethylbenz[a] anthracene (DMBA)-induced mammary tumorigenesis was investigated in several mouse strains. Selenium, administered as SeO2 in the drinking water, inhibited mammary tumor formation in DMBA-treated (C57BL x DBA/2f)F1, C3H/StWi and BALB/c female mice. In addition, selenium inhibited the occurrence of DMBA-induced ductal hyperplasias in (C57BL x DBA/2f)F1 and BALB/c mice and mammary tumour virus-induced alveolar hyperplasias in BALB/cfC3H mice. Selenium did not alter the growth of established mammary tumors. These results demonstrate that supplemental selenium inhibits both chemical-and viral-induced mouse mammary tumorigenesis, and secondly, that the development of preneoplastic lesions, an early stage in mammary tumorigenesis, is very sensitive to selenium-mediated inhibition.

Inhibition of DMBA carcinogenesis of hamster buccal pouch by phenanthrene and dimethylnaphthalene.

Phenanthrene (Phe) and to a lesser degree 1,4-dimethylnaphthalene (DMeN) were each found to retard the development of epidermoid carcinomas in hamster buccal pouch induced by the thrice weekly application of a 0.5 per cent solution of 7,12-dimethylbenz[a]anthracene (DMBA) in heavy mineral oil.

[Inhibition of the blastomogenic effect of 7,12-dimethylbenz(a)anthracene in female rats by buformin, diphenin, a polypeptide pineal extract and L-DOPA]. / Tormozhenie buforminom, difeninom, polipeptidnym ékstraktom épifiza i L-DOFA blastomogennogo éffekta 7,12-dimetilbenz(a)antratsena u krys-samok.

Female rats were treated with buformin, phenytoin, polypeptide pineal extract, L-DOPA or buformin combined with L-DOPA during 3 weeks before intravenous injections of DMBA (1.5 mg 6 times with one-week intervals) over a period of carcinogen injections and after it till the animals' death. The overall tumour incidence in the control group was 97%, while in buformin, phenytoin, pineal extract, L-DOPA and buformin + L-DOPA treated groups it amounted to 55, 71, 80, 50 and 62%, respectively (P < 0.05). The incidence of mammary adenocarcinoma amounted to 81, 36, 55, 26, 25 and 19%, respectively (P < 0.05). The mechanisms of the similar effects the drugs belonging to different classes produce on chemical carcinogenesis are discussed.

9-Hydroxyellipticine: inhibitory effect on skin carcinogenesis induced in Swiss mice by 7,12-dimethylbenz[a]anthracene.

9-Hydroxyellipticine (9-hydroxy-5,11-dimethyl-6-H-pyrido[4,3b]carbazole), a potent inhibitor of monooxygenases, strongly inhibits the initiation of skin tumors by 7,12-dimethylbenz[a]anthracene (DMBA) in male NMRI Swiss mice. 9-Hydroxyellipticine has not effect on promotion step.

Inhibition of polycyclic aromatic hydrocarbon-induced neoplasia by sodium cyanate.

The effects of sodium cyanate on the occurrence of 7,12-dimethylbenz(a)anthracene- and benzo(a)pyrene-induced neoplasia have been studied in rodents. Sodium cyanate added to the diet for 8 days prior to challenge with 7,12-dimethylbenz(a)anthracene inhibits 7,12-dimethylbenz(a)anthracene-induced mammary neoplasia in female Sprague-Dawley rats. Likewise, sodium cyanate in the diet inhibits the occurrence of benzo(a)pyrene-induced neoplasia of the forestomach and lung of ICR/Ha mice. Inhibition of benzo(a)pyrene-induced pulmonary neoplasia in A/J mice also is brought about by this compound. The identification of sodium cyanate as an inhibitor of chemical carcinogenesis adds a new chemical structure to those found previously to have inhibitory properties.