Anthracene-induced Rat Mammary Tumors Research Articles

Hormone Dependence of 7,12-Dimethylbenz[<italic>a</italic>]anthracene-Induced Mammary Tumor Growth: Correlation With Prostaglandin E<sub>2</sub> Content<xref ref-type="fn" rid="fn2">2</xref><xref ref-type="fn" rid="fn3">3</xref>

Prostaglandin content in 7,12-dimethylbenz[a]anthracene-induced rat mammary tumors was correlated with growth responses to alterations in endogenous estrogen and prolactin. Prostaglandin E2 (PGE2) content varied inversely with tumor latency. Ovariectomy of tumor-bearing Sprague-Dawley rats resulted in regression of tumors in 90% of the castrated rats. PGE2 content in tumors from ovariectomized rats was elevated twofold (P less than 0.05) compared to PGE2 content in tumors from intact controls. Haloperidol treatment promoted tumor growth even after ovariectomy and returned tumor PGE2 values to control levels. Tumors grouped by growth status irrespective of hormone status showed an inverse relationship between PGE2 content and growth response.

A comparison of the efficacy for antitumor activity of the non-steroidal antiestrogens analog II and tamoxifen in 7,12-dimethylbenz[ a]anthracene-induced rat mammary tumors

Analog II is a cyclopropyl derivative of stilbene which has been shown to produce antiestrogenic activity with no latent estrogenic effects in the mouse and to reduce the growth of 7,12-dimethylbenz[ a]anthracene (DMBA)-induced tumors in the rat. Thus, it was of interest to compare the antitumor activity of analog II to the antiestrogen, tamoxifen, which is a partial estrogen agonist in the rat and fully estrogenic in the mouse. The results indicate that analog II and tamoxifen were equally effective in reducing the growth of established DMBA-induced rat mammary tumors and that analog II produced a greater reduction in the occurrence of new tumors during the 7-week treatment period.

Vasopressin: Action on WRK-1 Rat Mammary Tumor Cells

WRK-1, a cell line in long-term culture derived from a 7, 12-dimethylbenz[a]anthracene-induced rat mammary tumor, responds to physiologic concentrations of vasopressin with increased precursor incorporation into phospholipids and with increased protein accumulation. Because vasopressin has been reported to be a potent mitogen for Hela cells and 3T3 cells, a study was conducted to determine whether it could act as a mitogen for WRK-1 cells. Under no conditions was a clear-cut mitogen response to vasopressin demonstrated.

Hydroxylated metabolites of tamoxifen are formed in vivo and bound to estrogen receptor in target tissues.

After in vivo administration of [3H]tamoxifen to immature female rats and chickens, polar metabolites of tamoxifen were found in plasma, liver, uterus, and oviduct. 4-Hydroxytamoxifen and M2, another hydroxylated metabolite of tamoxifen, were the major tritiated compounds of the cytosol and the KCl-nuclear extract of target tissues and appeared to occupy the estrogen receptor sites since their accumulation in these fractions was saturable, resistant to charcoal, and prevented by estradiol. In the rat uterus, 4-hydroxytamoxifen was predominant during the 24 h following the [3H]tamoxifen injection, then its concentration declined while M2 became predominant. 4-Hydroxytamoxifen was also found in chicken oviduct where tamoxifen is acting as a full estrogen antagonist. Moreover, liver, chicken oviduct, and lamb uterus were able to convert tamoxifen into 4-hydroxytamoxifen in vitro. Other estrogen target tissues, such as the rat uterus, dimethylbenz (a) anthracene-induced rat mammary tumors, and MCF7 cells, did not transform tamoxifen significantly. 4-Hydroxytamoxifen formed in vitro was able to bind selectively to estrogen receptor with a high affinity and with a low dissociation rate similar to estradiol. These results demonstrate that 4-hydroxytamoxifen is formed in vivo and retained on estrogen receptor in target tissues, due to its high affinity. Since we have separately shown that 4-hydroxytamoxifen is a full anti-estrogen, more potent than tamoxifen itself in MCF7 cells, we conclude that tamoxifen is mostly acting in vivo indirectly via hydroxylated metabolite(s).

Binding of catechol estrogens to the estrogen receptor of dimethylbenz(a) anthracene induced rat mammary tumors

The effect of 2-hydroxyestrone, 2-hydroxyestradiol and estriol on binding to cytosol receptors of dimethylbenzanthracene-induced rat mammary tumors was investigated. All three steroids bind to a high affinity estrogen receptor with 2-hydroxyestradiol having twice the affinity for tumor cytosol receptors than estriol or 2-hydroxyestrone. Both 2-hydroxyestradiol and estriol were able to translocate tumor cytosol receptor to the nucleus. Furthermore, experiments on the in vivo effect of these steroids on the nuclear accumulation and retention of estrogen receptors by rat uterus showed that 2-hydroxyestradiol and estriol caused significant nuclear receptor translocation with short retention time which is paralleled by a corresponding short term uterine growth responses. However, 2-hydroxyestrone was unable to induce receptor translocation or uterine growth effects.

Regulation of cyclic adenosine 3′,5′-monophosphate in relation to growth of dimethylbenz[ a]anthracene-induced mammary tumors in rats

In this study, adenylate cyclase, phosphodiesterase and cyclic adenosine 3′,5′-monophosphate (cAMP) levels were measured in 7,12-dimethylbenz[ a]anthracene (DMBA)-induced mammary tumors with different growth characteristics in both intact and ovariectomized rats. Tumors were classified as growing, stable, or regressing over a 10–;14-day period before excision. Regressing or static tumors had a higher cAMP concentration relative to tumors that were growing actively. This was due to high adenylate cyclase activity and low phosphodiesterase (both high and low K m) activities. Although estrogen deprivation resulted in a much greater rate of tumor regression than would occur spontaneously under normal conditions, the levels of adenylate cyclase, phosphodiesterases and cAMP were the same in tumors obtained from either intact or ovariectomized rats, when comparisons were made within the same category of tumor. These observations suggest that cAMP metabolism is independent of estrogen, since it is related to enhancement or retardation of growth rather than to the presence of absence of estrogen.

CAMP-dissociation kinetics in hormone-dependent and -independent rat mammary tumor cytosols.

Cytosols from 7, 12-dimethylbenz (alpha) anthracene-induced rat mammary tumors which exhibit different hormone-responsiveness were compared with respect to their cAMP-dissociation kinetics. At 22 degree C, pH 4.5, 1 micrometer cAMP, hormone-dependent mammary tumors exhibited monophasic dissociation rates with a rate constant of k-1 = 0.06 min-1. In contrast, hormone-independent mammary tumors exhibited biphasic dissociation curves with rate constants of k-1 = 0.47 and k-2 = 0.06 min-1. The binding of cAMP was completely reversible; radio-labeled ligand was completely dissociated by 1mM nonradioactive cAMP; the binding protein could be reassociated to its original binding level after dextran-coated charcoal adsorption. The mammary cytosols exhibited specific binding for cAMP which could be displaced partially by cGMP but not by ATP, ADP, AMP, or adenosine. Receptor inactivation during the course of incubation was negligible. Both mammary tissue cytosols exhibited similar association rates at 22 degree C, pH 4.5, 1 micrometer cAMP (k+1 = 5-7 x 10(5)M-1 min-1). These data indicate that mammary tissues exhibit 2 cAMP dissociation rates. Hormone-dependent mammary tumors exhibit a dissociation constant of a high affinity binding site (k-1/k+1 = 0.07 micrometer) whereas hormone-independent mammary tumors exhibit dissociation constants of one high affinity (k-1/k+1 = 0.07 micrometer) and a second low affinity site (k-1/k+1 = 0.05 micrometer).

Effects of LS 1727, a nitrosocarbamate of 19-nortestosterone, on dimethylbenz(a)anthracene-induced mammary tumors in the rat

LS 1727, a nitrosocarbamat of 19-nortestosterone, caused a dose-dependant retardation of growth of dimethylbenz(a)anthracene-induced mammary tumors in rats. LS 1727 had a more pronounced depressive effect on tumor growth and tumor DNA synthesis than 19-nortestosterone or CCNU. The uterine weight was increased and the ovarian weight decreased by LS 1727. The uptake of radioactivity in the tumors after injection of 3H -dihydrotestosterone was reduced by LS 1727 but not the radioactivity uptake after injection of 3H -estradiol- 17β or 3H -progesterone. There was no accumulation of radioactivity in the tumors after injection of 3H -LS 1727 labeled in the steroid moiety but the radioactivity concentration declined with time parallel with the decline in blood concentration. Thin layer chromatography revealed that LS 1727 is rapidly metabolized to 19-nortestosterone and polar metabolites. It is concluded that LS 1727 may have a cytostatic effect on the tumors owing to an action of the alkylating moiety of the compound. The cytostatic action may be enhanced by androgenic and estrogenic effects of the compound.

Prolactin receptors in primary cultures of carcinogen-induced rat-mammary tumors

7,12-Dimethylbenz [ a] anthracene-induced rat mammary tumors were dissociated with collagenase and hyaluronidase and placed into primary culture. In most cultures, specific binding of 125I-labeled ovine prolactin was (i) lower than that for the original tumors unless bovine prolactin (1 μg/ml) had been added to the dissociation medium, and (ii) varied with the type of growth medium used. The level of prolactin binding in cultured cells was relatively constant for the first 7–10 days. Prolactin binding in cultured cell homogenates was maximal at pH 7.0, proportional to cell protein, specific for prolactin, and reached a steady state by 12 h at 22° C. The half-maximum inhibition of 125I-labeled prolactin binding by unlabeled prolactin was 100 ng/ml for cells grown in 5–1000 ng of prolactin/ml. After prolactin was removed from the growth medium, the level of available binding sites progressively increased, reached a maximum at 48 h and then declined. At 48 h, the dissociation constant for prolactin binding ( K d ∼ 1 × 10 −10 M) was comparable to that in tumors. In some cultured tumors, a 48-h treatment with 0.5 or 1.0 ng of prolactin/ml caused an apparent increase in the level of prolactin binding. Prolactin increased DNA synthesis and its removal caused a reduction in [ 3H]estradiol and [ 3H]R5020 binding to cultured cell cytosols.

The effect of altered thyroid state on prolactin binding to liver and 7,12-dimethylbenz(a)anthracene-induced mammary tumors in rats.

SummaryThe effects of propylthiouracil (PTU) and pharmacological doses of thyroxine (T4) on growth and prolactin (PRL)-binding activity of DMBA-induced mammary tumors were studied. The hypo- or hyperthyroidism induced by these respective treatments did not affect the growth rate of established tumors, PRL binding activity in these tumors or plasma PRL in the tumor-bearing rats. In contrast, both PTU and T4 treatments caused a large reduction of PRL binding activity in the liver.

Failure of breast cancer cells in long-term culture to aromatize androstenedione

The ability of breast cancer cells in long-term tissue culture to aromatize androstenedione to estrone and estradiol was examined. ( 3H) androstenedione (1.1 × 10 −7M) was incubated with 9 cell lines of human breast cancer and one line derived froa a dimethylbenz(a)anthracene induced rat mammary tumor. No conversion to estrone or estradiol was detected. The findings are discussed in light of previous studies showing aromatization of androgens in breast cancer tissues.

Effects of a gonadotropin-releasing hormone (GnRH) analogue (A-43818) on7,12-dimethylbenz(a)anthracene-induced rat mammary tumors. Histological and endocrine studies

The effect of A- 43818 [D-leu 6 (des-gly-NH 10 2 , pro-ethylamide 9 )]-gonadotropin releasing hormone (GnRH) was investigated on rats bearing 7,12-dimethylbenz(a)anthracene (DMBA)-induced mammary tumors. Tumor growth was significantly inhibited by the s.c. administration of 10 μ g A- 43818, twice daily, for six weeks. A dose of 25 μ g seemed less effective. Controls and experimental groups were subjected to radioimmunoassays (RIA) of serum luteinizing hormone (LH), follicle-stimulating hormone (FSH) and prolactin (PRL), and to histological examination of pituitaries and ovaries. Treatment with A- 43818 resulted in atrophy of pituitary lactotropes and decreased prolactin concentration in plasma. Plasma LH levels were enhanced whereas FSH levels remained unchanged. The endocrine mechanisms of inhibition of tumor growth are discussed in the light of the well-known hormone dependance of DMBA-induced mammary tumors.

Histopathogenesis of 7,12-diemthylbenz(a)anthracene-induced rat mammary tumors.

The histopathogenesis and growth behavior of mammary tumors and dysplasias induced by a single intragastric dose of 7,12-dimethylbenz[a]anthracene in 50-day-old virgin female Lewis rats were examined both in situ and after transplantation into gland-free mammary fat pads of syngeneic hosts. Terminal mammary ductules are indicated as a site of origin of both ovarian hormone-dependent mammary tumors and spontaneously gegressing mammary tumors, and terminal ductule hyperplasia appears to be an early stage in mammary tumor formation. The precancerous nature of hyperplastic alveolar nodules induced by dimethylbenzanthracene in rats has been further examined, and our studies indicate that these nodules are not significantly preneoplastic.

7,12-Dimethylbenz(a)anthracene誘発ラット乳癌に及ぼすホルモンの影響に関する電子顕微鏡的研究

7,12-Dimethylbenz(a)anthracene誘発ラット乳癌に及ぼすホルモンの影響に関する電子顕微鏡的研究

Relationship of Adenosine 3′,5′-Cyclic Monophosphate and Guanosine 3′,5′-Cyclic Monophosphate to Growth of Dimethylbenz[ a ]anthracene-Induced Mammary Tumors in Rats 2 3 4

Alteration of growth of dimethylbenz[a]anthracene-induced mammary tumors was caused by removal of estrogen (ovariectomy), or insulin (diabetes), or by inhibition of prolactin secretin (treatment with an ergoline derivative). The levels of cyclic AMP (cAMP) and cGMP were measured in carcinomas classified as growing, static, and regressing. The amount of cAMP, expressed as pmoles/mg tumor weight or pmoles/mg protein, was lowest in growing tumors, intermediate in static tumors, and highest in those regressing. No correlation was seen between tumor growth and cGMP levels. Cyclophosphamide-induced tumor stasis did not elevate cAMP levels. The data suggest a role of cAMP in arrest of hormone-induced tumor growth.

Demonstration of antibodies against 7,12-dimenthylbenz(a)anthracene-induced rat mammary tumors by immunofluorescence.

Abstract: Anaplastic oligodendroglioma (AO) is a rare malignant tumor occurring in adults. Despite early indications of chemosensitivity, no clinical trial had demonstrated a benefit of chemotherapy beyond that of radiotherapy alone. Now, however, the Radiation Therapy Oncology Group (RTOG) 9402 and the European Organisation for Research and Treatment of Cancer (EORTC) 26951 studies investigating PCV (procarbazine [Matulane], lomustine [CeeNU], and vincristine) and radiation therapy vs radiation alone both show improved outcomes in patients with the 1 p/19q codeletion who received PCV and radiation therapy. These differences were detected with additional follow-up after publication of the initial results in 2006, when no differences in survival were detected. The two studies have also validated the use of the 1p/19q codeletion as a predictive biomarker in AO. Many will debate the wisdom of adopting PCV therapy as standard of care because of the greater toxicity of PCV compared with temozolomide (Temodar). Nonetheless, although important questions still remain regarding chemotherapy choice, sequence, and dosing, the answers to which will require additional large phase III trials, radiotherapy alone is no longer appropriate therapy for 1p/19q codeleted AOs.

AN INHIBITORY EFFECT OF STEROIDS ON 20-METHYLCHOLANTHRENE- AND 7,12-DIMETHYLBENZ(A)-ANTHRACENE-INDUCED RAT MAMMARY TUMORS.

The curability of the aggressive, large-cell lymphomas was first convincingly reported by Levitt et al in 1972.[1] Patients with “reticulum cell sarcoma” were treated with a regimen that came to be known as COMLA (cyclophosphamide, vincristine [Oncovin], methotrexate, leucovorin, cytarabine [Ara-C]). A more commonly quoted paper was published in 1975 by DeVita et al describing the cure of advanced “diffuse histiocytic lymphoma” with COPP (cyclophosphamide, vincristine [Oncovin], procarbazine, prednisone).[2] During the 1970s the CHOP regimen (cyclophosphamide, doxorubicin HCl, vincristine [Oncovin], prednisone) was described by McKelvey et al[3]; it quickly became the most widely used treatment for the aggressive large-cell lymphomas. Patients treated with two cycles of CHOP beyond documentation of a complete remission were often cured.[4]