Showing papers on "7,12-Dimethylbenz[a]anthracene published in 1990"

Effects of dietary perilla oil, soybean oil and safflower oil on 7,12-dimethylbenz[a]anthracene (DMBA) and 1,2-dimethylhydrazine (DMH)-induced mammary gland and colon carcinogenesis in female SD rats

Abstract: The effects of diet supplemented with perilla oil, which contains a large amount of n-3 alpha-linolenic acid, and n-6 linoleic acid rich soybean and safflower oil supplemented diets on 7,12-dimethylbenz[a]anthracene (DMBA)- and 1,2-dimethylhydrazine (DMH)-induced mammary gland and colon carcinogenesis were investigated in female SD rats. Groups of 23 or 24, 5 week old animals were first given three s.c. injections of 40 mg/kg body wt DMH followed by a single intragastric administration of 50 mg/kg body wt DMBA within 2 weeks of the commencement. Starting 1 week after the DMBA treatment, they were administered pellet diet containing 10% perilla oil, soybean oil or safflower oil for the succeeding 33 weeks. Histological examination revealed that the resultant numbers of mammary tumors per rat were significantly lower in rats given perilla oil diet (4.4 +/- 2.5) than in the soybean oil diet group (6.5 +/- 3.9). Furthermore, colon tumor incidence was significantly lower in animals receiving the perilla oil supplement (18.2%) than in those given safflower oil diet (47.4%), and the numbers of colon tumors per rat tended to be lowest in rats administered perilla oil. Also the incidence of nephroblastomas in rats receiving perilla oil diet (0%) was significantly lower than that for the soybean oil diet group (23.8%). The results thus indicate that the alpha-linolenic acid (n-3)-rich perilla oil diet inhibits development of mammary gland, colon and kidney tumors as compared to linoleic acid (n-6)-rich safflower or soybean oil diet.

Induction of dorsolateral prostate adenocarcinomas and other accessory sex gland lesions in male Wistar rats by a single administration of N-methyl-N-nitrosourea, 7,12-dimethylbenz(a)anthracene, and 3,2'-dimethyl-4-aminobiphenyl after sequential treatment with cyproterone acetate and testosterone propionate.

Abstract: Groups of 20–25 male Wistar rats (Cpb:WU), nine groups of 4-week-old rats, and nine groups of 8-week-old rats, were given cyproterone acetate (CA) s.c. or by gavage daily for 18 days at a dose of 50 mg/kg/day. Directly following CA treatment, the rats received 3 daily s.c. injections with testosterone propionate (TP) at a dose of 100 mg/kg/day. On the day after the last TP administration, a single dose of one of the following carcinogens was given to 3 groups: N-methyl-N-nitrosourea (MNU), 50 mg/kg i.v.; 7,12-dimethylbenz(a)anthracene, 30 mg/kg i.v.; 3,2′-dimethyl-4-aminobiphenyl, 250 mg/kg s.c. Three other groups received the same carcinogen treatments after 7 days of recovery from the CA administration. The last 3 groups received carcinogen without TP treatment, but immediately after CA pretreatment was stopped. A 25% incidence of invasively growing, metastasizing adenocarcinomas was found in the dorsolateral prostate region of 8-week-old rats that had received MNU after treatment with CA plus TP. In addition, this group had a 5% incidence of carcinoma in situ and a 5% incidence of atypical hyperplasia in the dorsolateral prostate. Lower incidences of adenocarcinoma of the dorsolateral prostate region and of carcinoma in situ and atypical hyperplasia of the dorsolateral prostate were found in other groups that were treated with MNU or 7,12-dimethylbenz(a)anthracene after pretreatment with CA, followed by TP or recovery, but never in rats that had been treated with CA only. In the groups treated with 3,2′-dimethyl-4-aminobiphenyl, which is slowly metabolized, these lesions were also found in groups that were pretreated with only CA. The carcinomas seemed to originate from the dorsolateral prostate and their average latency time was approximately 61 weeks. The 8-week-old rat given a MNU injection after sequential treatment with CA and TP may provide a relevant animal model for human prostatic cancer.

Changes in keratin expression during 7,12-dimethylbenz[a]anthracene-induced hamster cheek pouch carcinogenesis.

Abstract: This study was undertaken to explore the expression of keratins in the hamster cheek pouch carcinogenesis model, using monospecific keratin antibodies and a technique that allows immunoblotting analysis of tissues embedded in paraffin. Changes in keratin expression were correlated with histopathological changes and with the expression of the enzyme gamma-glutamyl transpeptidase. The right cheek pouch of 20 male golden Syrian hamsters was treated with 0.5% 7,12-dimethylbenz[a]anthracene for 16 weeks. As previously described by other laboratories, this treatment resulted in hyperplastic and dysplastic lesions and benign and malignant tumors. The keratins assayed in this study were K14 (Mr 55,000), K1 (Mr 67,000), and K13 (Mr 47,000). The normal hamster cheek pouch epithelium expressed K14 in the basal layer and K13 in the suprabasal and differentiated layers, whereas K1 was not detected by either immunohistochemistry or immunoblotting. Concomitant with 7,12-dimethylbenz[a]anthracene-induced hyperplasia, there were some topographical alterations in the distribution of K14. In this case, K14 was no longer restricted to the basal layer but was also expressed in differentiated cells. The same pattern was also observed in dysplastic lesions and in squamous cell carcinoma. Furthermore, expression of the K13 differentiation-associated keratin was preserved in this hyperplastic epithelium during all the stages of carcinogenesis, including either anaplastic or differentiated areas. In contrast, after 2 weeks of 7,12-dimethylbenz[a]anthracene treatment, K1 expression started as a weak and patchy pattern in suprabasal cells, becoming stronger and more homogeneous at 8 and 16 weeks of treatment. However, K1 was almost absent in squamous cell carcinoma, where only small very well differentiated areas were stained. We also observed gamma-glutamyl transpeptidase-positive foci in earlier stages of carcinogenesis, concomitant with the expression of the K1 keratin. However, it was not possible to find a perfect topographical correspondence between the two events. Alterations in the pattern of keratin expression appear to be a common feature during the development of squamous cell carcinoma in different systems and could be an excellent tool to study carcinogenesis and chemoprevention.

Expression of Epidermal Growth Factor Receptor, Polyamine Levels, Ornithine Decarboxylase Activity, Micronuclei, and Transglutaminase I in a 7,12-Dimethylbenz(a)anthracene-induced Hamster Buccal Pouch Carcinogenesis Model

Abstract: The expression of epidermal growth factor receptor and transglutaminase type I, polyamine (putrescine, spermidine, and spermine) levels, ornithine decarboxylase activity, and micronuclei occurrence were assessed in the 7,12-dimethylbenz( a )anthracene (DMBA)-induced hamster buccal pouch model to elucidate the role and timing of changes in different growth and differentiation markers during carcinogenesis. DMBA (0.5%) in heavy mineral oil was applied to the right buccal pouch 3 times per wk for up to 16 wk; controls received heavy mineral oil alone. Hamsters were killed after 0, 4, 8, and 16 wk. Frozen tissue was chemically analyzed for polyamine levels and ornithine decarboxylase activity and was also used for immunohistochemical analysis of transglutaminase I. Paraffin-embedded sections were used for epidermal growth factor receptor immunohistochemical determinations and for micronucleated cell assays. Hyperplasia was detected by histological analysis at 4 wk, dysplasia with or without papillomatous changes at 8 wk, and squamous cell carcinoma at 16 wk. Epidermal growth factor receptor was not expressed in the normal buccal epithelial layer, at a moderate level in both the superficial keratin and basal cell layers in hyperplastic epithelium, and at very high levels in both dysplasia and squamous cell carcinoma. Transglutaminase I was expressed at a limited level in normal buccal mucosa, was expressed at a low level in the basal layer of hyperplastic lesions, was somewhat elevated in dysplasia, and was markedly enhanced in squamous cell carcinoma. Putrescine and spermidine levels and ornithine decarboxylase activity increased dramatically after 8 and 16 wk of DMBA. Micronucleated cells increased after 4 wk of DMBA treatment, that high level sustained during all stages of carcinogenesis. We suggest that these biological markers could be excellent intermediate end points in assessing the effects of various chemopreventive agents to be tested in the hamster buccal pouch model and in human clinical trials.

Characterization of adenocarcinomas of the dorsolateral prostate induced in Wistar rats by N-methyl-N-nitrosourea, 7,12-Dimethylbenz(a)anthracene, and 3,2'-Dimethyl-4-aminobiphenyl, following sequential treatment with cyproterone acetate and testosterone propionate

Abstract: Carcinomas of the rat prostate induced by a single injection of N-methyl-N-nitrosourea, 7,12-dimethylbenz(a)anthracene, and 3,2'-dimethyl-4-aminobiphenyl, after sequential treatment with cyproterone acetate and testosterone propionate, were evaluated as potential animal model for prostatic cancer. All ten carcinomas examined were located in the dorsolateral prostate region and did not involve the distal parts of the seminal vesicle and coagulating glands. The incidence of urinary obstruction leading to the animals' death was 6 of 10 rats, and metastases in the lung, abdominal lymph nodes, and/or liver also occurred in 6 of 10 rats. The tumors were invasive adenocarcinomas, showing frequent perineural invasion and a variable degree of differentiation. There were ultrastructural similarities with human prostatic carcinoas, such as intracellular lumina. Plama acid phosphatase was increased. Enzyme histochemical analysis revealed similarities with the Dunning R3327H and -HI prostatic carcinomas but was not helpful in determining the site or origin of the tumors. The gross and microscopic appearance of the tumors and the observation of preneoplastic lesions exclusively located in the dorsolateral prostate suggest this lobe as site origin of the carcinomas. Preneoplastic lesions (n = 9) included atypical hyperplasias (n = 5) and lesions with all histological characteristics of carcinoma except for local invasion and metastases, which were classified as carcinoma in situ (n = 4). Although androgen sensitivity could not be assessed, the observed characteristics of the tumors [their long latency time (46-80 weeks), the presence of preneoplastic lesions, and the short duration of the treatment, leaving the animals intact] all indicate that the present approach is a valid animal model for the study of prostatic carcinogenesis. Chemicals/CAS: cyproterone acetate, 427-51-0; testosterone propionate, 57-85-2; 2',3-dimethyl-4-aminobiphenyl, 13394-86-0; 9,10-Dimethyl-1,2-benzanthracene, 57-97-6; Acid Phosphatase, EC 3.1.3.2; Aminobiphenyl Compounds; Methylnitrosourea, 684-93-5

Studies on the anti-tumor-promoting activity of naturally occurring substances. IV. Pd-II [(+)anomalin, (+)praeruptorin B], a seselin-type coumarin, inhibits the promotion of skin tumor formation by 12-O-tetradecanoylphorbol-13-acetate in 7,12-dimethylbenz[a]anthracene-initiated mice.

Abstract: Since Pd-II [(+)anomalin, (+)praeruptorin B], a seselin-type coumarin, was found to inhibit tumor promoter induced phenomenon in vitro, the effect of Pd-II on the in vivo tumor-promoting action of 12-O-tetradecanoylphorbol-13-acetate (TPA) in 7,12-dimethylbenz[a]anthracene-initiated mouse skin was investigated. Pd-II, applied 40 min before the TPA treatment, at a dose of 10 mumol/painting, completely suppressed tumor formation up to 20 weeks of tumor promotion, without any toxicity. Besides Pd-II, various anti-tumor-promoter coumarins were found in the traditional Chinese medicine Qian-Hu, from which Pd-II was obtained. These coumarins may be useful for the development of an effective method to prevent cancer.

Metabolism and toxicity of xenobiotics in the adrenal cortex, with particular reference to 7,12-dimethylbenz(a)anthracene.

Abstract: The adrenal cortex contains high amounts of detoxifying enzymes, as well as generators and protectors of reactive oxygen species. The high content of cytochrome P-450 enzymes in the adrenal cortex together with its remarkable tendency to accumulate hydrophobic substances probably contributes to the extraordinary vulnerability of the gland to a number of xenobiotics. The best studied adrenocorticolytic compounds are the potent carcinogen 7,12-dimethylbenz(a)anthracene (DMBA) and its liver metabolite 7-hydroxymethyl-12-methylbenz(a)anthracene (7-OHM-12-MBA). Adrenocorticolysis generated by these agents in vivo as well as in vitro demonstrates high regioselective requirements and is strongly influenced by the presence of ACTH, steroids, cytochrome P-450 inhibitors and antioxidants. Furthermore, 7-OHM-12-MBA has been demonstrated to uniquely generate selective and massive oxidation of mitochondrial glutathione in cultured rat adrenal cells. The DMBA-induced adrenocorticolysis is thoroughly discussed in this review with particular emphasis on the metabolism of DMBA and the influence of various effectors. A working hypothesis involving a possible peroxidative mechanism is also presented.

Distribution of covalent DNA adducts in mouse epidermal subpopulations after topical application of benzo(a)pyrene and 7,12-dimethylbenz(a)anthracene.

Abstract: The distribution of benzo(a)pyrene [B(a)P] and 7,12-dimethylbenz(a)anthracene (DMBA):DNA adducts was examined in five different subpopulations of SENCAR mouse epidermal cells separated based on buoyant density in continuous gradients of 61.5% Percoll. Three fractions consisted of primarily basal cells (Fractions 3 to 5), while two less dense fractions (Fractions 1 and 2) consisted of primarily differentiating keratinocytes. The levels of B(a)P and DMBA:DNA adducts were examined at 1 h, 6 h, 24 h, 72 h (except DMBA), and 28 days after a single topical application of an initiating dose. Among the basal cell subpopulations, the level of covalent B(a)P:DNA adducts in Fraction 5 cells was significantly higher (P less than 0.05) than Fractions 3 and 4 at every time point examined. On the other hand, B(a)P:DNA adduct levels in Fraction 5 were only significantly higher than Fraction 2 at 6 h and 72 h and not significantly different from Fraction 1 at any time point. With DMBA, no significant differences were initially observed in the levels of covalent DNA adducts among the various Percoll fractions at 1 h and 6 h after treatment. However, at 24 h and at 28 days. Fraction 5 cells had significantly higher (P less than 0.05) levels of covalent DMBA:DNA adducts than Fractions 1 to 4. To explore whether the observed differences in DNA adduct levels were due to differences in metabolic activation, we examined the levels of covalent adducts among epidermal subpopulations after topical application of (+/-)-anti-benzo(a)pyrene-7,8-diol-9,10-epoxide (anti-BPDE). Interestingly, 3 h after treatment with anti-BPDE, significantly higher (P less than 0.05) levels of binding were found in Fraction 5 compared with Fractions 1 to 4. High-pressure liquid chromatographic analyses of B(a)P and DMBA:DNA adducts 6 h and 24 h after treatment did not show any significant differences in adduct profiles among the various subpopulations. These results demonstrate the presence and persistence of hydrocarbon:DNA adducts in all epidermal subpopulations isolated on continuous Percoll gradients for at least 28 days after treatment. Furthermore, of the three basal cell subpopulations, the most dense cells (Fraction 5) developed the highest DNA adduct levels within 24 h and retained these higher levels over 28 days. Finally, differences in DNA adduct levels among epidermal subpopulations do not appear to result from different metabolic capabilities of the cells. The potential significance of these results is discussed in terms of the process of skin tumor initiation.

DNA fingerprinting of 7,12-dimethylbenz[a]anthracene-induced and spontaneous CD-1 mouse liver tumors.

Abstract: Determining to what degree chemicals and environmental agents contribute to the development of cancer would be materially enhanced by the ability to distinguish chemically induced tumors from those that arise spontaneously. Using DNA fingerprinting as an assay, we investigated whether somatic DNA rearrangements are more frequent in chemically induced mouse liver tumors than they are in spontaneous mouse liver tumors. Tumors were induced by a single i.p. injection of 12-day old male Crl:CD-1(ICR)BR (CD-1) mice with 20 nmol/g 7,12-dimethylbenz[a]-anthracene and were harvested 9 to 12 months after injection. Spontaneous tumors were obtained from 94- to 98-week old male CD-1 mice. We detected 8 rearrangements in 14 7,12-dimethylbenz[a]anthracene-induced tumors, which corresponds to a high rearrangement frequency of about 2% (of the minisatellite bands examined). Furthermore, 6 of these rearrangements included complete band losses which must have occurred early in tumor development. However, only 2 band changes were observed in 15 spontaneous tumors, and both changes were intensity shifts which may represent rearrangements that occurred later during tumor progression. Histological examination showed that the higher frequency of rearrangements in 7,12-dimethylbenz[a]anthracene-induced tumors versus spontaneous tumors was not related to differences in the degree of tumor progression or malignancy. Our results suggest that DNA fingerprinting may be a valuable assay for differentiating certain chemically induced tumors from spontaneous tumors.

Effect of the mammary carcinogen 7,12-dimethylbenz[a]anthracene on pineal melatonin biosynthesis, secretion and peripheral metabolism.

Abstract: The aim of this study was to establish whether the nocturnal peak concentrations of circulating melatonin are affected by a single dose of 7,12-dimethylbenz[a]anthracene (DMBA) in female Sprague-Dawle

Use of Intracellular H3 Messenger RNA as a Marker to Determine the Proliferation Pattern of Normal and 7,12-Dimethylbenz[a]anthracene-transformed Hamster Oral Epithelium

Abstract: One of the major goals in cancer research and diagnosis is to identify in a tissue the population of actively dividing cells and their pattern of growth and to differentiate the proliferation patterns of normal and transformed tissues. We now describe a method for determining the proliferation pattern of any tissue (normal, diseased, or transformed), applicable in any mammalian species. This method is based on the fact that the transcription of histone H3 gene in mammalian cells is tightly coupled to DNA synthesis during cellular division. Resting cells or cells that just exited the cell cycle will have no detectable H3 mRNA. The presence of H3 mRNA in a cell is thus a good indicator of its proliferation status. We carried out in situ hybridization of H3 mRNA in hamster oral epithelia exhibiting a variety of altered growth patterns as a consequence of exposure to the chemical carcinogen, 7,12-dimethylbenz[ a ]anthracene to demonstrate the usefulness of this technique. This application does not require in vitro manipulation of tissues nor does it require the prior administration of a tracer. The proliferation pattern at a single moment in time instead of an accumulated pattern over a period of time is produced. Finally, since the technique of in situ hybridization can be applied to archival tissues, retrospective studies can be done. This application should find usefulness in a wide variety of experimental research settings, particularly cancer research.

Chemoprevention of 7,12-dimethylbenz[a]anthracene-induced mammary carcinogenesis in rat by the combined actions of selenium, magnesium, ascorbic acid and retinyl acetate.

Abstract: The chemopreventive actions of sodium selenite (SS), magnesium chloride (MC), ascorbic acid (AA) and retinyl acetate (RA), given singly or in combinations, on mammary carcinogenesis induced by 30 mg of 7,12-dimethylbenz[a]anthracene (DMBA) in female adult rats were evaluated. Administration of modulators was carried out from the age of 40 +/- 3 days to 240 +/- 3 days. When DMBA alone was given 100% of the rats developed mammary tumors. When modulators were given singly the tumor incidences were reduced to 51.77% (SS), 46.4% (MC), 57.1% (AA) and 48.1% (RA). When the modulators were given in combination of twos, the tumor incidences were further reduced to 29.5% (SS + MC), 31% (SS + AA), 29.6% (SS + RA), 25.9% (MC + AA), 31.8% (MC + RA) and 34.6% (AA + RA). Administration of modulators in combinations of threes resulted in still further reduction of tumor incidences to 22.2% (SS + MC + AA), 19.2% (SS + MC + RA), 16% (MC + AA + RA) and 23.1% (AA + RA + SS). When all four modulators were given concurrently the tumor incidence was only 12%. Further, the number of tumors per tumor-bearing animal declined with the increase in the number of agents used in combination for modulation.

Retinoids as modulators of metabolism: their inhibitory effect on cyclophosphamide and 7,12-dimethylbenz[a]anthracene induced sister chromatid exchanges in a metabolically competent cell line.

Abstract: Recently, retinoids have been studied for their ability to modify the carcinogenic/mutagenic activity of chemical compounds. Results show that they can inhibit the malignant transformation of cells, the induction of cancer in experimental animals and the mutagenicity of promutagens. Our experiments examine how retinol and retinoic acid can decrease the frequency of sister chromatid exchange (SCE) induced by two indirect mutagens/carcinogens (cyclophosphamide and 7,12-dimethylbenz[a]anthracene) in an epithelial liver cell line of male Chinese hamster (CHEL cells). These cells are metabolically competent and activate different classes of promutagens into biologically active metabolites. Our results are consistent with the suggestion that retinoids modulate the genotoxicity of indirect-acting mutagens by altering their metabolic activation or cellular detoxification processes or both.

Effect of nicotine on 7,12-dimethylbenz[a]anthracene carcinogenesis in hamster cheek pouch.

Abstract: We divided 40 male Syrian golden hamsters into four groups of 10 animals each, and we treated both cheek pouches of each hamster three times a week as follows: group 1, 50 microL of sesame oil; group 2, 50 microL of 6% nicotine in sesame oil; group 3, 50 microL of 1% 7,12-dimethylbenz[a]anthracene (DMBA) in sesame oil; and group 4, 50 microL of 1% DMBA in 6% nicotine in sesame oil. Cheek pouches were examined clinically and histologically after 12 weeks of treatment. Hamsters treated with DMBA and nicotine showed significantly (P less than .001) more tumors and a significantly (P less than .05) greater-than-expected proportion of large tumors (greater than or equal to 3-mm diameter) than hamsters treated with DMBA alone. Histologically, there was a greater degree of dysplasia in lesions from the group receiving DMBA plus nicotine than in the DMBA only group. The results suggest that nicotine acts as a cofactor in DMBA tumorigenesis.

Inhibition of the binding of 7,12-dimethylbenz[a] anthracene and benzo[a] pyrene to dna in mouse skin epidermis by 1-ethynylprene

Abstract: The effects of 1-ethynylpyrene (EP), 1-vinylpyrene (VP) and 2-ethynlnaphthalene (EN) on the covalent binding of 7,12-dimethylbenz[a]anthracene (DMBA) and of benzo[a]-pyrene (B[a]P) to the epidermal DNA in mouse skin were investigated. When applied topically, 5 min before an initiating dose of 10 nmol DMBA or of 200 nmol B[a]P, EP was an effective inhibitor of the formation of the covalent complexes of these procarcinogenic polycyclic aromatic hydrocarbons (PAHs) with the epidermal DNA. VP, applied under the same conditions, was a significantly less effective inhibitor of the binding of DMBA to DNA and showed even weaker inhibition of the binding of B[a]P. EN was ineffective as an inhibitor of the binding of either DMBA or B[a]P. These results establish that both the pyrene nucleus and the ethynyl substituent of EP contribute to the effective inhibition of the binding of DMBA and B[a]P to the epidermal DNA of mouse skin. No significant changes in the ratios of the anti- to the syndiol epoxide-DNA adducts of DMBA or of B[a]P were produced by doses of EP that produced inhibitions of the binding to DNA. At doses of VP that inhibited covalent binding of both DMBA and B[a]P, no changes in DMBA-DNA adduct distributions were observed but changes in the relative proportions of several B[a]P-DNA adducts were noted. These data are discussed in terms of the potential of aryl acetylenes to act as suicide inhibitors (mechanism-based inactivators) of cytochrome P450-dependent monooxygenase isozymes.

Effect of ultraviolet (UV) radiation and UVB-absorbing sunscreen ingredients on 7,12-dimethylbenz(a)anthracene-initiated skin tumorigenesis in hairless mice.

Abstract: These experiments describe the enhancement of 7,12-dimethylbenz(a)anthracene (DMBA)-initiated skin tumorigenesis in hairless mice by subsequent chronic ultraviolet (UV) irradiation of the same skin site. Each carcinogen was administered at a level that separately resulted in threshold tumorigenesis. The cocarcinogenic response was evident as a marked increase in tumour incidence, tumour multiplicity and degree of tumour malignancy. Irradiation through the topically applied UVB (290-315 nm)-absorbing sunscreen ingredient, 2-ethylhexyl-p-methoxycinnamate, totally protected from the photoenhancement. However, irradiation through an alternative UVB absorber, octyl-N-dimethyl-p-aminobenzoate, failed to protect from photoenhancement. A possible immunologic role for the enhancement of DMBA tumorigenesis by UV radiation is proposed.

Effects of high dietary fat on the total DNA and receptor contents in rats with 7,12-dimethylbenz[a]anthracene-induced mammary carcinoma.

Abstract: The influence of high dietary fat on the malignant intensity and the hormone receptors of 7,12-dimethylbenz[a]anthracene (DMBA)-induced mammary carcinoma in female Sprague-Dawley rats were analyzed by

Ha-ras oncogene mutations in cell lines derived from rat tracheal implants exposed in vivo to 7,12-dimethylbenz[a]anthracene.

Abstract: The frequency of Ha-ras mutations was determined as a function of neoplastic progression in cell lines derived from rat tracheal implants exposed in vivo to 7,12-dimethylbenz[a]anthracene. Restriction fragment-length polymorphism (RFLP) analysis revealed an A----T transversion in the second base of codon 61 in 2 of 11 cell lines. One of the positive cell lines was tumorigenic, but the other was neither tumorigenic nor anchorage independent, thus indicating a lack of correlation between neoplastic stage and ras mutation. Densitometry analysis of the RFLP bands indicated that approximately 50% of the cells within these two heterogeneous populations contained the mutation. Direct sequence analysis of polymerase chain reaction-amplified DNA confirmed these results and did not reveal any other mutations in this region of the Ha-ras gene.

Effects of OK-432 (Picibanil) on Estrogen Receptor Levels and Tamoxifen Treatment in 7,12-Dimethylbenz[a]anthracene-Induced Rat Mammary Cancers

Abstract: The effects of OK-432 (Picibanil) on estrogen receptor (ER) levels and subsequent tamoxifen (TAM) treatment were examined in 189 female Sprague-Dawley rats with 7,12-dimethylbenz[a]anthracene (DMBA)-induced mammary cancers. When OK-432 was administered (0.1 KE/kg i.p. once weekly) for 12 weeks to the rats after DMBA, the average ER level of the TAM-responsive tumors in the OK-432-treated group was significantly higher than that in the control group. The antitumor effect of TAM was significantly greater in the OK-432-treated group. When OK-432 was administered to rats with established DMBA tumors, the average ER levels did not change significantly after 2 or 4 weeks of treatment. ER levels in the control group (no treatment) fell significantly after 2 or 4 weeks. These results suggest that hormone dependence of DMBA-induced rat mammary cancers may be maintained or augmented by the administration of OK-432.

Antiestrogen-binding sites in 7,12-dimethylbenz(a)anthracene-induced rat mammary tumors: relation to growth.

Abstract: We have detected specific high-affinity binding sites for nonsteroidal antiestrogens in 98% of 7,12-dimethylbenz(a)anthracene-induced rat mammary tumors. Since recent studies have suggested that these binding sites may be involved in the regulation of cell growth and proliferation, we attempted to define a possible relationship between the growth of these hormone-dependent tumors and their antiestrogen-binding site content. Rats bearing such tumors were either treated with haloperidol (to increase prolactin secretion and stimulate tumor growth) or oophorectomized (to reduce circulating estrogen concentration and suppress tumor growth). Compared with controls, haloperidol treatment clearly enhanced tumor growth while oophorectomy induced tumor regression, but neither procedure had any effect on the antiestrogen-binding site concentration. Furthermore, tumors which responded to endocrine manipulation had similar antiestrogen-binding site concentrations as tumors which did not respond. We conclude that (1) the alterations in tumor growth induced by these endocrine manipulations are probably not mediated through a change in antiestrogen-binding site concentration, and (2) the tumor concentration of these binding sites is not under estrogen or prolactin control.

Mechanism of suppression of footpad reaction in mice by 12-tetradecanoylphorbol 13-acetate and 7,12-dimethylbenz[a]anthracene.

Abstract: We reported previously that footpad reaction (FPR) of BALB/c mice against sheep red blood cells (SRBC) was suppressed by the percutaneal administration of 12-tetradecanoyl 13-acetate (TPA), a tumor promoter, following that of 7,12-dimethylbenz[a]anthracene (DMBA), a tumor initiator. This effect could be transferred with Thy-1(+) and Lyt-2(+) spleen cells. These findings suggested that this effect was caused by induction of the antigen nonspecific T-suppressor cells and that the process of the induction consisted of two steps. In the present report, we studied the cells related to the first step of this process. The spleen cells from the donor mice on which 400 nmol of DMBA was painted were transferred to the recipient mice which had been immunized 1 hr before the transfer. Then, 8 nmol of TPA was painted on the recipient mice every day for a week. Nine days after the transfer, FR against SRBC was measured. FPR in the recipient mice was suppressed compared to the control, showing that the effect of DMBA can be transferred with the spleen cells. The results of the treatment of the cells to be transferred with monoclonal antibodies and complement show that the cells which is responsible for the transfer of the effect are Mac-1(+), Thy-1(-), Lyt-2(-) and Ia(-). Also the effect of DMBA could be transferred with peritoneal macrophages from the donor mice on which DMBA was painted and anti Ia antibody treatment of the macrophages did not abrogate the effect of transfer.(ABSTRACT TRUNCATED AT 250 WORDS)