Ultrastructure of mammary carcinomas in male rats induced by 7,12-dimethylbenz(a)anthracene

The morphology of mammary tumors induced by 7,12-dimethylbenz(a)anthracene in male rats was investigated by light and electron microscopy. All tumors induced in male rats were carcinomas with prominent epithelial growth which shows a medullary or cribriform appearance. Neither mammary dysplasias nor fibroadenomas were induced in male rats. Foci of adenoid cystic carcinoma were encountered in some parts of tumors. Papillary and/or tubular patterns, which have been observed frequently in mammary carcinomas in female rats, were not prominent histologic features in male rats. Secretory activity was not remarkable. The morphology of mammary carcinomas in male rats was unchanged in primary and transplanted tumors under various hormonal conditions. This finding supports our previously published results that the mammary carcinomas in male rats are hormone-independent, although our previous biochemical study revealed that the tumors contain both estrogen and estrogen-dependent progesterone receptors.     

Anti-tumor promoting potential of luteolin against 7,12-dimethylbenz(a)anthracene-induced mammary tumors in rats

In this study, we evaluated the anti-tumor potential of luteolin (30mg/kg, p.o.), combined with cyclophosphamide (10mg/kg, i.p.) (LU+CYC) orally administered for 20 days; and CYC individually for 10 days against 7,12-dimethylbenz(a)anthracene (DMBA)-induced mammary carcinogenesis in Wistar rats. Combination treatment (LU+CYC) inhibited the incidence rate of tumors and decreased tumor volume significantly without changing the total body weight of the animals. Long-term treatment did not show any apparent toxicity in rats. The CYC-treated group showed potential reduction of tumor volume (74%), severe toxicity, and loss of body weight. In order to elucidate the anticancer mechanism of luteolin, antioxidant activities such as superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPx) generation in the liver, kidney and breast, as well as protein profiles, were also examined. Biochemical analysis of the combination-treated group showed significant (P<0.01; P<0.05) inhibition of lipid peroxide (LPx) formation (oxygen-free radicals), the level and the activity of SOD, CAT and GPx were found to be very high than the LU and CYC individually treated rats at a 30mg/kg dose. 2D gel electrophoresis analysis revealed that (56kDa) high molecular weight protein was detected in tumors of rats receiving combination treatment than the cancer controls. The biological significance of that protein involved for the dysfunction of cancer cells and induces apoptosis. Histopathological changes also confirmed the formation of tumor tubules and neovascularization after the treatment. Overall, these results suggest that the combination treatment provided antioxidant defense with strong chemopreventive activity against the genesis of DMBA-induced mammary tumors.     

Pineal gland in rats with 7,12-dimethylbenz(a)anthracene-induced mammary tumors subjected to manipulations known as enhancers of pineal actions

The ultrastructure of pinealocytes was studied in rats with 7,12-dimethylbenz(a)anthracene-induced mammary tumors which were subjected to experimental manipulations known as enhancers of pineal actions (anosmia, underfeeding or cold exposure). In these animals we found: (I)--more nuclei with deep nuclear invaginations; (II)--a large number of cytoplasmic organelles, including lipid droplets, myeloid bodies, synaptic ribbons and lysosomes; (III)--numerous degenerative changes. In general, we found an increase in structural features related to pineal photoneuroendocrine activity. Our results indicate that pineal-dependent inhibition of neoplastic growth induced by these experimental manipulations, previously reported, can be mediated through an increase in pineal metabolic activity.     

Influence of estrogen and progesterone on the induction of mammary carcinomas by 7,12-dimethylbenz(a)anthracene in ovariectomized rats.

The influence of estrogen on mammary carcinogenesis was studied in female Sprague-Dawley rats ovariectomized at the age of 36 days and given injections of 17 beta-estradiol (group I:0, II:1, III:10, IV:100, V:1000 micrograms/2 days) between the ages of 36 and 250 days and a single oral dose of 20 mg of 7,12-dimethylbenz(a)anthracene (DMBA) at the age of 50 days. No palpable mammary carcinomas were detected up to the age of 135 days. At the age of 135 days, each group was divided into two subgroups (a and b). Rats of the second subgroup (Ib, IIb, IIIb, IVb and Vb) were given additional injections of progesterone (P; 4 mg/2 days) between the ages of 135 and 250 days. At the age of 250 days, the incidence of mammary carcinoma was significantly higher in rats from group IIIb than in groups Ib and IIIa, and that in group IVa was also higher than in group Ia. The incidence in group IVb was significantly lower than in group IVa. The carcinomas in group IIIb were palpable papillo-tubular adenocarcinomas and those in group IVa were secretory micro-adenocarcinomas. These results indicate that the induction of mammary carcinomas by DMBA is totally inhibited by ovariectomy and/or high doses of estrogen, but that mammary carcinomas are initiated by DMBA under hormonal conditions in which suitable levels of estrogen are present. They also suggest that the growth of DMBA-induced mammary carcinomas in the rats from group III were accelerated by additional injections of P and that those in rats from group IV were inhibited by additional P.(ABSTRACT TRUNCATED AT 250 WORDS)     

Stimulation of estradiol-17 beta secretion by 7,12-dimethylbenz (a) anthracene during mammary tumor induction in Sprague-Dawley rats

Testosterone, androstenedione, progesterone, 17-hydroxyprogesterone, estrone and estradiol-17 beta serum levels were measured at given times after dimethylbenz (a) anthracene (DMBA) treatment of a sensitive rat strain Sprague-Dawley (S-D) and a resistant strain Wistar (W). Tumors appeared with a 100% incidence around the 14th to 15th estrous cycle after DMBA treatment in in Sprague-Dawley rats. Hormonal determinations were made, during the 5th or 6th estrous cycle after DMBA treatment, in groups of 4-day cycling rats of both strains which were given DMBA or the carrier solution (sesame oil) when they were about 55-days old. In Sprague-Dawley female rats, DMBA treatment significantly stimulated estradiol-17 beta and estrone preovulatory surge on proestrous days. No such stimulation was found for any other steroid at any time of the estrous cycle. On the other hand, the resistant Wistar rats did not show any disturbed preovulatory or basal steroid hormone release after the carcinogen treatment. These results complete and explain previous findings concerning the hypothalamo-pituitary activity after DMBA treatment of S-D rats: an early and persistent alteration in the centers involved in the hormonal cyclicity of the hypothalamo-pituitary-ovarian axis must be a result of the DMBA treatment. This deregulation could probably account for the distant and selective production of tumors in the mammary gland induced by a single gastric administration of DMBA.     

Chloramphenicol and dextramycin, inhibitors of mammary carcinogenesis induced by 7,12-dimethylbenz(a)anthracene]

In noninbred rats chloramphenicol and its optical isomer dextramycin diminished the blastomogenic effect of 7,12-dimethylbenz(a)anthracene on mammary glands. The protective effect was shown by a decreased tumor incidence at all periods of observation and an increase in the life span of rats and in the case of dextramycin this action consisted in a prolongation of the latent period of tumor emergence.     

Influence of age and parity on the susceptibility of rat mammary gland epithelial cells in primary cultures to 7,12-dimethylbenz(a) anthracene

Summary Mammary gland epithelial cells from rats of different ages or with different reproductive histories vary in their proliferative properties and susceptibility to dimethylbenz(a)anthracene (DMBA) carcinogenesis in vivo. The present study was carried out to determine whether these differences are maintained under in vitro conditions. Primary cultures of mammary gland epithelial cells of young virgin, old virgin, and parous rats were treated with various doses of DMBA. Growth rates, DNA synthesis, and dose-response curves were determined; the toxicity of DMBA was measured by its effect on cell growth. Cell morphology was studied by transmission and scanning electron microscopy. Epithelial cells from the mammary gland of young virgin rats adapted rapidly to the culture conditions, behaving as if the cells were in the logarithmic phase of growth prior to plating. Mammary gland epithelial cells from old virgin and parous rats required a lag period prior to cell growth during which the proliferating cells adapted to the culture conditions. Cells from each group had comparable doubling times, and DNA synthesis peaked approximately 1 d after initiation of growth in culture. The numbers of proliferating cells decreased with increasing age and parity of the donor. Mammary gland epithelial cells of young virgin rats were more susceptible to both low and high doses of DMBA than those of old virgin and parous rats when the carcinogen was added either 24 h after plating or at the peak of DNA synthesis. These results indicate that age and parity influence the proliferative status of the cells and their susceptibility to DMBA in vitro, simulating in that way the in vivo situation. Supported by Public Health Service Grants CA-23539 and CA-27026 from the National Cancer Institute and by an Institutional grant from the United Foundation of Greater Detroit.     

Scanning electron microscopy of 7,12-dimethylbenz(a)-anthracene-induced mammary carcinoma in the female Sprague-Dawley rat

The surface morphology of normal mammary glands and mammary carcinomas was examined under the scanning electron microscope after digestion of connective tissue and the basal lamina with collagenase, hyaluronidase and hydrochloric acid (HCl). Two types of cells were clearly identified in the acini of normal glands; granular epithelial cells and stellate myoepithelial cells. Spindle-shaped myoepithelial cells lying longitudinally along the mammary ducts were also recognized. 7,12-dimethylbenz(a)anthracene-induced mammary carcinomas consisted of irregular masses of cells which had polypoid or columnar processes with rounded heads; the masses appeared to be composed of a single type of rhomboid cell. The tumors lacked the stellate or spindle-shaped myoepithelial cells found in normal acini and ducts.     

Morin augments anticarcinogenic and antiproliferative efficacy against 7,12-dimethylbenz(a)-anthracene induced experimental mammary carcinogenesis

In general, oxidative stress resulting from an imbalance between prooxidant and antioxidant systems plays an important role in the pathogenesis of cancer. Morin (3,5,7,2',4'-pentahydroxyflavone), a member of the flavanol group, has been shown to possess chemopreventive potential against hepatocellular and colon cancer in experimental animals. Given the demonstrated importance of morin, aim of the present study was to evaluate the effect of morin on antiproliferative and anticarcinogenic effect against DMBA-induced experimental mammary carcinogenesis. Oral administration of 7,12-dimethylbenz(a)-anthracene (25 mg/kg body weight) to rats resulted in significant reduction of body weight, enzymic antioxidants (superoxide dismutase, catalase, glutathione peroxidase, and glutathione reductase), and nonenzymic antioxidants (reduced glutathione, vitamin C, and vitamin E). The levels of lipid peroxidation markers (thiobarbituric acid reactive substances and hydroperoxides) and tumor markers such as CA 15-3, AFP and CEA in serum were increased significantly in cancer-induced animals as compared to control rats. Oral supplementation of morin at a dose of 50 mg/kg body weight significantly improved the body weight, enzymic, and nonenzymic antioxidants and considerably decreased the lipid peroxidation marker and tumor markers levels. Histological observations also correlated with the biochemical parameters. Tumor bearing animals showed marked increase in proliferating cell nuclear antigen-positive cells and also the number of AgNOR/nuclei compared with control rats while this expression levels were significantly reduced upon morin treatment. Thus, this study reveals the possible beneficial effect of morin as chemopreventive agent against the oxidative stress induced during mammary carcinogenesis.