Effect of contraceptive steroids on mammary gland of beagle dog and its relevance to human carcinogenicity

Dogs for Life: Beagles, Drugs, and Capital in the Twentieth Century

This article tracks the transformation of beagle dogs from a common breed in mid-twentieth century American laboratories to the de jure standard in global toxicological research by the turn of the twenty-first. The breed was dispersed widely due to the expanding use of dogs in pharmacology in the 1950s and a worldwide crisis around pharmaceutical safety following the thalidomide scandal of the 1960s. Nevertheless, debates continued for decades over the beagle's value as a model of carcinogenicity, even as the dogs became legislated stand-ins for human beings in multiple countries. Situating beagles as a biocommodity, the article calls for more sustained attention to the "political economy" of laboratory organism breeding, use, and production. The story of American commercial breeder Marshall Farms offers insight into the role of for-profit companies in contemporary laboratory animal provision, as the article makes a case for the value of a global perspective on transnational corporations as key sites of scientific practice and collaboration.

Removal of the toxic effects of chlormadinon acetate on the development of Drosophila melanogaster via the use of nordihydroguaiaretic acid

In this study, the effects of chlormadinon acetate (CMA) and CMA + nordihydroguaiaretic acid (NDGA) on various developmental stages of Drosophila melanogaster were investigated. Different concentrations of CMA (1.0; 3.0; 5.0 and 10.0 μM/100 mL medium) and CMA + NDGA as the concentrations of CMA (1.0 + 1.0; 3.0 + 3.0; 5.0 + 5.0 and 10.0 + 10.0 μM/100 mL medium) were carried out during the developmental periods of the flies. When F(1) progeny of control and application groups were compared, CMA was found to extend the process of metamorphosis and decrease the total offspring numbers. However, these negative effects were inhibited by NDGA treatment at different concentrations. These results suggest that NDGA could effectively inhibit CMA-induced abnormalities in developmental stages of D. melanogaster. It was found that the difference between the groups was significantly important (p < 0.05).

Species Differences in Inhibition Potential of Nonsteroidal Anti-Inflammatory Drugs Against Estradiol 3β-Glucuronidation Between Rats, Dogs, and Humans

Differences in the inhibitory potentials against UDP-glucuronosyltransferase (UGT) between species have been reported only rarely, even though the information would be useful for the precise characterization of drug candidates. In this study, the inhibition potentials of nonsteroidal anti-inflammatory drugs (NSAIDs) against UGT-catalyzed estradiol 3beta-glucuronidation (E3G) in the liver microsomes of rats, dogs, and humans were compared. Rat liver microsomes (RLMs) and human liver microsomes (HLMs) exhibited homotropic activation kinetics with S(50) values of 22 and 12 microM, respectively. However, dog liver microsomes (DLMs), exhibited Michaelis-Menten kinetics with no activation. Among the NSAIDs investigated (diclofenac, diflunisal, fenoprofen, flurbiprofen, ibuprofen, indomethacin, ketoprofen, mefenamic acid, niflumic acid, and sulindac), only niflumic acid and mefenamic acid inhibited E3G potently in all three species. The IC(50) values of NSAIDs against E3G in RLMs and HLMs were within a threefold difference of each other, while those in DLMs was more than three times higher than the other two. In conclusion, RLMs showed an inhibitory pattern similar to that of HLMs, whereas DLMs presented a distinct pattern. These results indicate that a rat animal model would be useful for evaluating the inhibitory potentials of drugs against estradiol glucuronidation, but a dog model would not.

Antigenotoxic effect of nordihydroguaiaretic acid against chlormadinone acetate-induced genotoxicity in mice bone-marrow cells

Nordihydroguaiaretic acid (NDGA), a phenolic lignan, was tested for its antigenotoxic potential against chlormadinone acetate (CMA)-induced genotoxic damage in mice bone-marrow cells. Doses of about 22.50 mg/kg body weight of CMA were given along with 1, 5 and 10 mg/kg body weight of NDGA intraperitoneally. The treatment resulted in the reduction of sister chromatid exchanges and chromosomal aberrations induced by CMA, suggesting an antigenotoxic potential of NDGA. Earlier studies show that CMA generates reactive oxygen species, responsible for genotoxic damage. The free radical-scavenging property of NDGA is responsible for the reduction of genotoxic damage induced by CMA in mice bone-marrow cells.

Evaluation of genotoxic potential of synthetic progestin chlormadinone acetate

The genotoxicity study of a synthetic progestin chlormadinone acetate, was carried out on mouse bone marrow cells using sister chromatid exchanges (SCEs) and chromosomal aberrations (CAs) as parameter, chlormadinone acetate was studied at three different doses, i.e. 5.62, 11.25 and 22.50 mg/kg body weight and was found to be non-genotoxic at 5.62 mg/kg body weight. But at 11.25 and 22.50 mg/kg of body weight chlormadinone acetate increases SCE (P < 0.001) and CA (P < 0.01) at significant level compared to normal control. The results suggests a genotoxic and cytotoxic effect of chlormadinone acetate in mouse bone marrow cells.

Morphogenic and tumorigenic potentials of the mammary growth hormone/growth hormone receptor system

Due to the characteristics of the luteal phase of the ovarian cycle in the dog, which spans a prolonged time period, this species is a suitable model to study the role of progestins in both normal morphogenic and abnormal tumorigenic processes in the mammary gland. It has been convincingly shown that progestins, including endogenous progesterone, induce the synthesis of growth hormone (GH) in the normal and the tumorous canine mammary gland. The growth hormone receptor (GHR) is also expressed in normal and tumorous canine mammary tissues and in this concise overview we highlight recent advances in our understanding of the significance of the GH/GHR system for mammary gland (patho)biology. In an attempt to unravel the cellular and molecular mechanisms associated with the GH/GHR system, we were able to show that both GH and GHR are differentially expressed in normal canine mammary tissues. Maximum expression of both GH and GHR occurs during the proliferation phase of the tissue, which links the progestin-induced mammary GH synthesis to the progestin-associated proliferation of epithelial cells in the mammary gland. Expression of the GH/GHR system is also present in most canine mammary tumors, albeit that GHR expression may be downregulated in undifferentiated mammary carcinomas. Upon GH stimulation of the GHR-positive CMT-U335 canine mammary tumor cell line, the transcription factors STAT5A and STAT5B become phosphorylated on their tyrosine residues, which is likely to reflect the significance of mammary GH in vivo. Molecular analysis of the canine mammary GHR transcripts by RT-PCR provided evidence for normal and alternative processing of the GHR primary transcript encoding the full-length plasma membrane GHR and at least four putative GH binding proteins (GHBPs), respectively. The translation products from the alternatively spliced GHR transcripts indicate an intact N-terminal ligand binding domain and an unique C-terminal portion, lacking the transmembrane domain and cytoplasmic tail. Thus, these proteins are considered to be able to bind GH, but have lost their signaling potential. The exact biological role of these GHBPs remains to be established, but GHBPs may have a transport function in the endocrine route, regulate the level of biologically available GH locally, or dominant-negatively influence the full-length plasma membrane GHR. In dog mammary cancer specimens strongly reduced levels of alternatively spliced GHR transcripts were found compared to the non-malignant mammary tissue. Notably, expression of both GH and GHR in mammary cancer cells is not restricted to dogs. Recent experiments generated evidence for GH and GHR expression in human breast cancer cells, and also in human prostate cancer cells, which represents another highly prevalent hormone-sensitive human malignancy. In agreement with our findings in the dog, the expression of the hGH-N gene in human mammary cancer cells seemed to correlate positively with their progesterone receptor status, which warrants, in our opinion, a reconsideration of the role of progestins in breast cancer of women. In human prostate cancer cells four different hGH-N transcripts were detected, which encode classical 22 kDa GH and GH-related proteins. Consistent with the findings on the canine GHR, different GHR transcripts in human mammary cancer cells and prostate cancer cells were detected encoding the full-length plasma membrane GHR and putative GHBPs.

IGF-I and retinoic acid regulate the distribution pattern of IGFBPs synthesized by the canine mammary tumor cell line CMT-U335

Stromal-epithelial interactions modulate growth and development in normal and neoplastic mammary gland. The release of IGF binding proteins (IGFBPs) by the stromal compartment of the mammary gland may play a modulating role in the IGF-mediated proliferation of mammary epithelium. Therefore, the IGFBP-expression pattern of the canine mammary tumor cell line U335 (CMT-U335), which has a mesenchymal phenotype, was determined. In addition, the effects of IGFs and all trans retinoic acid (RA) on DNA synthesis, and IGFBP secretion and distribution were examined. The IGFBPs secreted by CMT-U335 were characterized as IGFBP-2, -4, -5, and -6. Moreover, CMT-U335 appeared to be a suitable mammary mesenchymal cell line for study of the regulatory factors of IGFBP expression and the mechanism(s) involved. IGFs and RA enhanced IGFBP concentrations in cell-conditioned medium with IGF-I and RA having an additive effect. The IGF-I-stimulated DNA synthesis, however, was inhibited by RA. The difference between IGF-I and RA was an enhanced IGFBP-5 binding to the extracellular matrix (ECM) by RA, whereas IGF-I reduced binding to the ECM. Because high doses of insulin had no significant effects on IGFBP concentrations in the medium, it is concluded that IGF-I-induced changes in IGFBP concentrations are not mediated by type-IIGF receptors and may be the consequence of IGFBP redistribution.

A population-based case-control study of canine mammary tumours and clinical use of medroxyprogesterone acetate

We investigated whether or not an association could be found between mammary tumours and prior clinical use of medroxyprogesterone acetate (MPA) in bitches. A population-based retrospective age-matched case-control study was designed based on interviews with the owners of the bitches. The proportion of bitches with diagnosed mammary tumours (group MT+, n = 98) that had received progestin injections was compared with the proportion in a control group without mammary tumours (group MT-, n = 98). In the case group 39%, and in the control group 21% of the bitches had been treated with MPA. A significantly higher number of bitches with mammary tumours had been exposed to progestins, compared with the control group without mammary tumours (odds ratio = 2.32, Chi-square = 7.01, p = 0.008). Bitches treated clinically with low doses of MPA to avoid oestrus were at a greater risk of developing mammary tumours, the majority of which were histologically malignant (91%).

Diabetes mellitus in a dog with a growth hormone-producing acidophilic adenoma of the adenohypophysis

A 9-year-old male Doberman Pinscher was referred to the Department of Clinical Sciences of Companion Animals, Faculty of Veterinary Medicine, Utrecht University, for polyuria/polydipsia, anorexia, and vomiting. Laboratory examination of blood and urine revealed hyperglycemia, glucosuria, and acidosis. Diabetes mellitus was diagnosed but was very resistant to subsequent insulin treatment. At the owners' request, the dog was euthanatized and a postmortem examination was performed. In addition to hepatic, pancreatic, and renal changes compatible with diabetes mellitus, an acidophilic adenoma of the adenohypophysis was found. Immunohistochemical staining for growth hormone, adrenocorticotropic hormone, and prolactin showed a strong immunolabeling for growth hormone within the cytoplasm of the tumor cells. Although growth hormone level was not measured in the plasma, our findings suggest that the diabetes mellitus in this dog was caused by excess growth hormone secreted by the pituitary neoplasm.

Similarities and differences in the glucuronidation of estradiol and estrone by UDP-glucuronosyltransferase in liver microsomes from male and female rats

In this study, we evaluated the effects of pH, in vitro inhibitors, in vivo enzyme inducers, age, and sex on the glucuronidation of estradiol and estrone by rat liver microsomes. Although the pH dependence curves for the glucuronidation of estradiol and estrone were similar, the pH dependence curves for these estrogens by liver microsomes from adult male rats were very different from those by liver microsomes from adult female rats. These results suggest that liver microsomes from adult male and have different estrogen glucuronosyltransferases. Liver microsomes from immature or adult female rats catalyzed the glucuronidation of estrone and estradiol more rapidly than liver microsomes from age-matched male rats. Intraperitoneal injection of sodium phenobarbital (75 mg/kg/day) or dexamethasone (75 mg/kg/day) into immature or adult male or female rats for 3-4 days resulted in a 33-58% increase in liver microsomal glucuronosyltransferase activity for estradiol, but there was little or no stimulatory effect on glucuronosyltransferase activity for estrone. Treatment of immature or adult male or female rats with 3-methylcholanthrene (25 mg/kg/day) for 3-4 days did not stimulate liver microsomal glucuronosyltransferase activity for estradiol or estrone, but the glucuronidation of 4-nitrophenol was stimulated several-fold. The in vitro addition of testosterone had a strong inhibitory effect on the glucuronidation of estradiol and estrone by liver microsomes from both adult male and female rats, whereas the in vitro addition of 4-nitrophenol had a slightly greater inhibitory effect on the glucuronidation of estradiol and estrone by adult male liver microsomes than by adult female liver microsomes. In conclusion, our results suggest that male and female rat livers have different estrogen glucuronosyltransferases and that the glucuronidation of estradiol, estrone, and 4-nitrophenol is catalyzed by different glucuronosyltransferases that are under different regulatory control.

Growth hormone mRNA in mammary gland tumors of dogs and cats

We have shown recently that in the dog progestin administration results in mammary production of immunoreactive growth hormone (GH). At present we demonstrate the expression of the gene encoding GH in the mammary gland of dogs and cats using reverse-transcriptase PCR. GH mRNA was found in the great majority of normal mammary tissues as well as benign and malignant mammary tumors of the dog and was associated with the presence of immunoreactive GH in cryostat sections. The mammary PCR product proved to be identical to that of the pituitary. The highest expression levels were found after prolonged treatment with progestins. In carcinomas GH mRNA was also found in progesterone receptor-negative tissue samples, indicating that after malignant transformation GH gene expression may become progestin independent. GH mRNA was also present in mammary tissues of cats with progestin-induced fibroadenomatous changes. It is concluded that GH gene expression occurs in normal, hyperplastic, and neoplastic mammary tissue of the dog. The expression in normal tissue is stimulated by progestins and might mediate the progestin-stimulated development of canine mammary tumors. The demonstration of progestin-stimulated GH expression in mammary tissue of cats indicates that the phenomenon is more generalized among mammals.

Neoplastic lesions of questionable significance to humans

Many compounds giving a positive result in animal carcinogenicity studies through mechanisms involving secondary carcinogenesis pose little or no risk to humans. This article provides an overview of current understanding, with particular reference to renal tumors in male rats with alpha 2mu-globulin nephropathy, urinary bladder neoplasia in rodents, mesovarian leiomyomas induced in rats by beta 2-receptor stimulants, carcinoid tumors in the rodent stomach induced by prolonged suppression of acid secretion, thyroid follicular cell tumors in rodents, canine mammary neoplasia due to administration of progestagens, rodent mammary neoplasia induced by estrogens, uterine endometrial carcinomas of rats induced by dopamine agonists, Leydig cell tumors in the testis of rats, and ovarian tubulostromal adenomas in mice. A positive result on a rodent carcinogenicity study should not automatically preclude further development of a compound; future progress in this field should increase the accuracy of the rodent carcinogenicity study as a tool in human safety assessment.

Contraceptive steroids and the mammary gland: is there a hazard?--Insights from animal studies

The safety of synthetic steroid hormones to be used for contraception in the human female is tested in rats, beagle dogs, and (once marketing starts) in monkeys. Because early studies did not show a mammary tumor stimulating effect in the human, in contrast to findings in the dog, many objections have been raised to the use of the dog for these toxicity studies. It has been claimed that the dog is unique in its sensitivity to the mammary tumor promoting effect of progestins and that this tumorigenic effect results from progestin-induced growth hormone (GH) induction. A thorough review of the literature does not support these claims. Tumor stimulatory effects of progesterone or synthetic progestins can be observed under some conditions in rodents as well as in cats and monkeys. In addition, recent evidence suggests a role for progesterone in mammary tumorigenesis in the human, and contraceptive steroids may also not be completely without risk. While the suggested role for GH in dog mammary tumorigenesis is far from proven, such a role cannot be excluded in the other species. Whether tumor stimulatory effects of sex steroids are based upon induction of proliferation in target cells or upon genotoxic effects or both is not yet certain.

Endocrine pathology of estrogens: species differences

The clinical uses of estrogens are associated with serious adverse effects, so the experimental toxicology of these compounds is under continuous review. Structurally different estrogens have qualitatively similar effects in animals when given in amounts way above the rodent uterotrophic dose. Toxicity still tends, however, to be related to estrogenic potency. Carnivores are more susceptible than rodents. Changes in reproductive, mammary and endocrine tissues are consistent with hyperestrogenism. Growth rate is decreased in rats and mice, but weight gains have been reported in other species. The weights of the liver, spleen, thymus and other organs are changed. Liver damage can occur. Susceptibility declines in the order cat, ferret, rat and mouse, dog. Clotting changes seen in the rat are secondary to liver damage. Moderate doses elicit anemia in rats, but lethal bone marrow depression in dogs and ferrets. Death is associated with hemorrhage. Antiestrogens modify aspects of estrogen toxicity in the rat, but not in the ferret. The predictive value of animal studies for humans has been disappointing. Interspecies variations at the hypothalamic-pituitary axis appear to have an important bearing on the differential activities of estrogens and antiestrogens across the species.

Guidelines and requirements for the evaluation of contraceptive steroids

Since their introduction in the early 1960s, the oral contraceptive (OCs) steroids have been subjected to preclinical and clinical investigations unprecedented in medical history. As a result of such extensive studies, it is now possible to make a comprehensive review of preclinical and clinical data on oral contraceptives. The OCs were introduced at a time when the Food and Drug Administration (FDA) was undergoing drastic changes as a result of the thalidomide tragedy, the introduction of the Kefauver-Harris Amendment, and the desire for greater control over the pharmaceutical industry. The initial requirements for the safety evaluation of OCs were identical to those of other drugs. There were no explicit requirements for OCs although it was generally felt that the requirements should be more stringent because the OCs were being used in otherwise healthy women for long periods of time and with minimal medical supervision. In the 1960s when it became apparent from ongoing studies that there was an increased incidence of mammary tumors in dogs treated with some progestins, the FDA made the decision to terminate clinical studies and established the requirement for 7- and 10-yr studies in dogs and monkeys, respectively. The primary purpose of this paper is to present an historical perspective of the evolution of the preclinical requirements for the evaluation of the safety of OCs prior to their use in the various phases (I, II, III) of clinical trials. Some proposed changes in the requirements are discussed. This information will form the basis for other presentations dealing with the safety assessment of OCs in rats, dogs, and monkeys.

Studies of three canine mammary carcinoma cell lines--I. In vitro properties

Three cells lines, REM 134, 111 and 367, have been derived from canine mammary carcinomas and their morphological characteristics in vitro are described. They are tumorigenic in athymic nude mice, have no demonstrable fibronectin on their cell surfaces and exhibit a varied pattern of lectin binding. They can be cloned in semi-solid agar. One line, REM 134, responds to oestrogen and luteotropic hormone in vitro, although none of the three had demonstrable oestrogen receptors.

Ten-year oral toxicity study with Norlestrin in rhesus monkeys

The long term effects of the oral contraceptive, Norlestrin, were evaluated in sexually mature female rhesus (Macaca mulatta) monkeys over a 10 year period. Norlestrin, a combination of norethindrone acetate and ethinylestradiol (50:1) was given orally on a continuous cyclic regimen of 21 d of dosing followed by 7 d without treatment. Groups of 16 monkeys each received the drug at dose levels of 0.05, 0.51, and 2.55 mg/kg representing multiples of 1, 10, and 50 times the human dose, respectively. A comparable group of 16 animals remained untreated and served as controls. Selected clinical and laboratory parameters were monitored throughout the study and all animals were necropsied and evaluated for gross and histopathologic changes. All dose levels were well tolerated and survival was not affected. There were no consistent treatment-related alterations in coagulation or other clinical laboratory parameters. Ophthalmologically, macular pigmentary anomalies were observed in all groups. Treatment-associated pathologic findings, representing exaggerated pharmacological responses with superimposed senile changes, including ovarian and uterine atrophy and dilatation of acini and ducts in the mammary gland. Periodic vaginal cytologic examination and mammary gland palpation did not demonstrate drug related changes. A small number of neoplasms was seen in all groups and a granulosa cell carcinoma of the ovary occurred in a control animal. The benign tumors consisted of three cutaneous papillomas: one in a low dose and one in a high dose animal, a uterine leiomyoma in one high dose animal, and a pancreatic duct adenoma in one low dose animal. The results of this study indicate that Norlestrin had no significant toxic manifestations or tumorigenic potential when administered on a cyclic regimen to female rhesus monkeys at levels up to 50 times the human dose for ten yr.

The characteristics of a canine mammary carcinoma cell line, REM 134

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Immunocytochemical technique for detection of prolactin (PRL) and growth hormone (GH) in hyperplastic and neoplastic lesions of dog prostate and mammary gland

An immunocytochemical technique was described to test for immunoreactive prolactin (PRL) and growth hormone (GH) in spontaneous and experimentally induced hyperplastic and neoplastic lesions of the prostate and mammary gland. The dog was used as an animal model. The specificity and validity of the immunocytochemical staining procedure and of the antisera to canine PRL and canine GH can be regarded as established for the demonstration of PRL- and GH-dependent staining respectively. In mammary and prostatic tissues, both endogenous PRL and GH as well as intracellular free binding sites (for exogenous PRL and GH) were detected immunocytochemically. The technique presented seems to be an important tool to localize putative target sites for pituitary hormones in hormone-dependent hyperplasia and neoplasia.