Mammary Cancer In Mice Research Articles

Stem Cells and Mammary Cancer in Mice

I have used the paradigm of mammary cancer induction by the mouse mammary tumor virus (MMTV) to illustrate the body of evidence that supports the hypothesis that mammary epithelial stem/progenitor cells represent targets for oncogenic transformation. Further, it is argued that this is not a special case applicable only to MMTV-induced mammary cancer, because MMTV acts as an environmental mutagen producing random interruptions in the somatic DNA of infected cells by insertion of proviral DNA copies. In addition to disrupting the host genome, the proviral DNA also influences gene expression through its associated enhancer sequences over significant inter-genome distances. Genes commonly affected by MMTV insertion in multiple individual tumors include the Wnt genes, the fibroblast growth factor (FGF) gene family, and the Notch gene family. All of these gene families are known to play essential roles in stem cell maintenance and behavior in a variety of organs. The MMTV-induced mutations accumulate in cells that are long-lived and possess the properties of stem cells, namely, self-renewal and the capacity to produce divergent epithelial progeny through asymmetric division. The evidence shows that epithelial cells with these properties are present in normal mammary glands, may be infected with MMTV, and become transformed to produce epithelial hyperplasia through MMTV-induced mutagenesis and progress to frank mammary malignancy. Retroviral marking via MMTV proviral insertion demonstrates that this process progresses from a single mammary epithelial cell that possesses all the features ascribed to tissue-specific stem cells.

Cyclin D1 and mammary carcinoma: new insights from transgenic mouse models

Cyclin D1 is one of the most commonly overexpressed oncogenes in breast cancer, with 45–50% of primary ductal carcinomas overexpressing this oncoprotein. Targeted deletion of the gene encoding cyclin D1 demonstrates an essential role in normal mammary gland development while transgenic studies provide evidence that cyclin D1 is a weak oncogene in mammary epithelium. In a recent exciting development, Yu et al. demonstrate that cyclin D1-deficient mice are resistant to mammary carcinomas induced by c-neu and v-Ha-ras, but not those induced by c-myc or Wnt-1. These findings define a pivotal role for cyclin D1 in a subset of mammary cancers in mice and imply a functional role for cyclin D1 overexpression in human breast cancer.

Ah receptor agonists as endocrine disruptors: antiestrogenic activity and mechanisms

2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) and related compounds induce a broad spectrum of biochemical and toxic responses and disrupt multiple endocrine pathways. Research in this laboratory has focused on characterizing aryl hydrocarbon receptor (AhR)-mediated antiestrogenicity in the rodent uterus and mammary and in human breast cancer cells. TCDD inhibits multiple estrogen (E2)-induced responses in these tissues including development or growth of human mammary and endometrial cancer cells, carcinogen-induced mammary cancer in rats, and mammary cancer in mice bearing breast cancer cell xenografts. The mechanisms of AhR-mediated antiestrogenicity are complex; however, studies on the molecular biology of cross-talk between the AhR and estrogen-receptor (ER) signaling pathways have been initiated using several E2-regulated genes as models. The results indicate that the nuclear AhR complex targets specific genomic core inhibitory dioxin responsive elements (iDREs) in promoter regions of some E2-responsive target genes to inhibit hormone-induced transactivation. The pS2, cathepsin and c-fos genes have functional iDREs, whereas the iDRE in the progesterone receptor gene promoter was not functional. Research has also focused on development of AhR-based antiestrogens which inhibit mammary tumor development and growth but do not exhibit prototypical AhR-induced toxic responses.

Enlargement of the ampullary gland and seminal vesicle, but not the prostate in int-2/Fgf-3 transgenic mice

Expression of the int2/Fgf-3 gene occurs during normal embryonic development and is associated with mammary cancer in mice. Overexpression of this gene under the control of the mouse mammary tumor virus long terminal repeat (MMTV-LTR) in males was reported to result in prostatic enlargement. In this report male Fgf-3-overexpressing mice were shown to have enlarged ampullary glands, seminal vesicles, and ductus deferens; there was extensive epithelial hyperplasia in the ampullary glands and seminal vesicles. The prostates of these animals were of normal size and histology. The transgene was expressed in all of the enlarged organs, which are derived exclusively from the Wolffian duct. Male secondary sex organs derived from the urogenital sinus, e.g., the ventral prostate, coagulating gland, and bulbourethral glands, were normal and did not express the MMTV-LTR-driven Fgf-3 transgene. A dorsolateral prostate was also morphologically normal but did express the transgene. This study underscores the importance of careful organ identification in transgenic models in which gross organ enlargement or distortion occurs. It also highlights the heterogeneity of the response to Fgf-3 among the secondary sex organs and even within the prostate itself.

Effect of acupuncture on immunologic function and histopathology of transplanted mammary cancer in mice

This experiment mainly describes the effects of acupuncture on immunologic function and histopathology of transplanted mammary cancer in mice. The results were as follows: in acupuncture group, NK cell activity and T-lymphocyte positive rate of acid alpha-naphthyl acetate esterase (ANAE) and lymphocyte transformation rate were all increased. Compared with the control group, there was a significant difference (P < 0.01). The difference was insignificant, when compared with normal group (P > 0.05). Comparing the pathology grading of acupuncture group with control group, it showed marked difference in pathological section (P < 0.01). Adenoid structure and the degree of lymphocytic infiltration also have marked difference between acupuncture and control group (P < 0.05). Less tumour volume in acupuncture than control group were observed (P < 0.01). This indicated that acupuncture might increase the immunologic function of transplanted mammary cancer in mice and inhibit the growth of mammary cancer and enhance both differentiation level of mammary cancer cells and lymphocytic infiltration. Possibly acupuncture mightt reduce the malignancy of mammary cancer cells.

Experimental control of neoplastic progression in cell populations: Foulds' rules revisited.

Foulds introduced six rules of tumor progression based on his observations of spontaneous mammary cancer in mice and generalized them to all forms of neoplasia [Foulds, L. (1954) Cancer Res. 14, 327-339 and Foulds, L. (1969) Neoplastic Development (Academic, New York), Vol. 1, preface and pp. 72-74.] Rules III, IV, and V are considered controversial, and research in animals seems inadequate to resolve the controversies. A subline of NIH 3T3 cells undergoes progressive transformation to produce foci of increasing population density when repeatedly constrained by sequential rounds of growth to and maintenance at confluence. Analysis of the results provides a cellular basis for rules III, IV, and V. Rule III states that progression is independent of the growth of the tumor and occurs in tumors that are arrested. Cell culture shows that progression is actually favored by constraint of growth, a result inconsistent with a major role for point mutations in progression. Indeed, there is a suggestion that the transformation may arise from chromatin changes preceding apoptosis. Rule IV states that progression can be gradual or abrupt but the latter conclusion has been frequently criticized. Cell culture exhibits both forms of progression but, in particular, eliminates the doubt about the abrupt form. Rule V, which is in a sense an extension of rule IV, states that progression follows one of alternative paths of development. The results in culture indicate that every independent transforming event gives rise to foci of unique morphology. Thus, even for the single characteristic of transformed focus morphology, many alternative paths to neoplasia are available to cells. In addition to clarifying the rules of progression, a method is described for pinpointing the time of the occurrence of events that are only expressed as dense foci after a variable lag time. The results in culture reinforce Foulds' conclusion that neoplastic development is primarily an epigenetically driven process and identify some of the cellular interactions that underlie that process.

Growth inhibition of estrogen-dependent and estrogen-independent MXT mammary cancers in mice by the bombesin and gastrin-releasing peptide antagonist RC-3095.

Many breast cancers are estrogen independent, and even in patients who initially respond to estrogen suppression therapy, the regression is often temporary. We have recently shown that antagonists of bombesin and gastrin-releasing peptide, including RC-3095, inhibit the growth of pancreatic, colonic, and prostatic cancers in experimental animals. This effect was associated with a substantial decrease in epidermal growth factor (EGF) receptor levels in pancreatic and colon cancers. In view of these findings, we investigated the effects of our synthetic bombesin and gastrin-releasing peptide receptor antagonist D-Tpi6,Leu13 psi (CH2NH)-Leu14 bombesin(6-14) (RC-3095) on the growth of hormone-dependent and hormone-independent MXT mouse mammary cancers in vivo. Female (C57BL x DBA/2)F1 mice bearing estrogen-dependent or estrogen-independent MXT mammary carcinomas were treated with small doses (20 micrograms/d) of RC-3095 administered from osmotic minipumps. Separate groups of mice with estrogen-independent tumors received RC-3095, bombesin, or gastrin-releasing peptide(14-27) at 20 micrograms/d. We determined tumor volume and weight, mitotic index, apoptosis (programmed cell death), and argyrophilic nucleolar organizer regions, an indicator of tumor cell proliferation. Levels of receptors for EGF and bombesin were measured in tumor membrane fractions. Growth of both estrogen-dependent and estrogen-independent MXT breast cancers was significantly inhibited by RC-3095. Bombesin or gastrin-releasing peptide had no effect on the growth of estrogen-independent tumors. Inhibition of tumor cell proliferation was indicated by a 45%-65% reduction in tumor volume, a 35%-58% reduction in tumor weight, and statistically significant decreases in argyrophilic nucleolar organizer region counts after treatment with RC-3095. In estrogen-independent cancers, tumor inhibition was associated with a decrease in the capacity of EGF receptors from 0.21 +/- 0.016 pmol/mg membrane protein in controls to 0.03 +/- 0.003 pmol/mg membrane protein in the RC-3095-treated group. This is the first demonstration of inhibitory effects of bombesin and gastrin-releasing peptide antagonists on the growth of breast cancers in vivo. These findings suggest that bombesin antagonists should be considered for breast cancer therapy.

Spontaneous progression of hyperplastic outgrowths of the D1 lineage to mammary tumors: Expression of mouse mammary tumor virus and cellular proto‐oncogenes

Mammary cancer in mice is characterized by progression through defined stages of preneoplasia, with the most common preneoplastic stage being the hyperplastic alveolar nodule (HAN). We determined the relative levels of RNA expression of various cellular proto-oncogenes and endogenous mouse mammary tumor virus genes in outgrowths and tumors of three sublines of the transplantable D1 HAN preneoplastic outgrowth line. The three sublines differed in relative tumor-producing capabilities. Subline D1B produced a high incidence of tumors with short latency periods, whereas sublines D1C and D1D produced low incidences of tumors with long latency periods. No consistent alteration in proto-oncogene expression correlated with relative tumorigenicity, although tumors frequently contained higher levels of one or more proto-oncogene transcripts as compared with preneoplastic tissue. Slightly elevated (2- to 6-fold) levels of different oncogene transcripts were detected in 13 of 17 tumors as compared with outgrowth tissue, including abl (2 tumors), fps (5 tumors), Ha-ras (6 tumors), and Ki-ras (8 tumors). One tumor contained 45 times more Ki-ras-specific RNA than outgrowth tissue because of a comparable amplification of Ki-ras DNA sequences. Elevated levels of Ha-ras occurred more frequently in tumors of a high-incidence subline than in a less-aggressive subline (5/10 vs 1/7), but this difference was not statistically significant. However, consistent changes in MMTV expression accompanied progression from preneoplastic tissues to mammary tumors. All 17 tumors displayed reduced levels of the MMTV-specific long terminal repeat (LTR) transcript (1.6 kb) as compared with HAN tissue; tumors with moderate levels of LTR transcript expressed the 3.8-kb envelope message as well, one not detected in HANs. Expression of the LTR transcript is apparently influenced by factors in addition to the methylation status of endogenous mouse mammary tumor virus genes, which was similar in outgrowths and tumors. As the survey of representative proto-oncogenes failed to identify a uniform change between HAN and tumors, it is likely that other genes are involved in tumor progression in the mammary gland.

On the Safety of Estrogenic Hormone Residues in Edible Animal Products

The Delaney clause or amendment (1969) of the Federal Food, Drug, and Cosmetic Act states, in essence, that if carcinogenic substances are used as feed additives no residues determined methods of examination prescribed or approved by the Secretary are allowable in edible products for human use. Everyone agrees that consumers should be protected from the involuntary ingestion of amounts of residues which might produce cancer. Involuntary is a key word because patients voluntarily may use prescribed estrogens, known to be carcinogens or cocarcinogens at high dosage levels as, for example, the use of the postcoital pill to prevent implantation of the conceptus (Morris and van Wagenen 1973). With many so-called chemical carcinogens such as 7-12-dimethylbenz [a] anthracene (DMBA), some of which are mutagenic (Miihlbock and Boot 1958, Hollaender 1971), no safe levels have been established. The situation with essential nutrients and natural hormones used as feed additives, which have been labeled as carcinogens or cocarcinogens, differs, however, in that these substances are normal body constituents and perform useful physiological functions. Means of preventing the involuntary consumption of harmful amounts of hormonal residues in edible animal products is our concern in this paper. In short, we are suggesting that low levels of residues of essential nutrients or of natural or synthetic hormones are noncarcinogenic and thus, that these low levels are not subject to the Delaney amendment. The problem, therefore, is in defining levels of residues of hormones in animal products which involve no risk to people consuming these food products. Distinctions between the so-called chemical carcinogens and hormones have been drawn by Miihlbock and Boot (1958): It is not possible to induce cancer with a single large hormone dose nor is the tumor-exciting effect of hormones irreversible before tumor formation actually occurs. The conclusion must be that other mechanisms are instrumental in the hormonal induction of cancer as compared with the so-called chemical carcinogens. On the basis of studies of mouse mammary cancer, Bern (1960) suggests, (1) hormonal factors involved in the evolution of a definite precancerous state may be no more than those factors in normal tissue development; (2) the tumorigenic role of the hormonal milieu may be no more than the continued maintenance of a degree of hyperplasia (the precancerous state); (3) the so-called tumorigenic hormone may be but one component of an essential milieu wherein no one hormone can be considered more essential than any other; (4) in general, the hormonal influence may be a 'permissive' one, essential for tumor appearance but not itself inductive. Gardner (1939) reviewed studies indicating that sufficiently large amounts of all natural estrogens tested would increase the incidence of mammary cancer in mice and synthetic estrogens were soon found to act similarly (Shimkin and Grady 1941). In all instances known to us, hormones are carcinogenic only when given in amounts greater than the amounts required to produce a physiological

Interactions Between Viral and Genetic Factors in the Origin of Mammary Tumors in Mice&lt;xref ref-type="fn" rid="FN1"&gt;1&lt;/xref&gt;

Resistance to the oncogenic effect of a murine mammary tumor is controlled by a few genes. It is associated with poor replication of the virus. A battery of tests, including electron microscopy, immunodiffusion, immunofluorescence, and bioassay, demonstrated the presence of a mammary tumor virus in 7 genetically diverse mouse strains. The virus was often expressed in an incomplete form and usually at a late age. Switching on of virus release correlated well with spontaneous tumor incidences. Carcinogens, such as X rays and urethan, induced the early appearance of viral antigens. These findings strongly suggest an all-viral etiology of mammary cancer in mice. It is theorized that every mouse contains genetic information for a mammary tumor virus, which is in the form of a DNA copy of the viral RNA integrated into one of its chromosomes. The transcription of this germinal provirus is regulated by a repressor, but other controlling mechanisms are also involved, leading sometimes to partial expression.

Studies on cellular regulations.

����� When I embarked on the study of the proteins of muscle, I was a revolutionary in that field. Twenty years ofwork turned me into a reactionary. Also, after looking at the same problem for two decades, my vision became blurred, and I could not see the forest for the trees. So I felt it was time to move to a different subject. Supported by J. McLaughlin, I set out to elucidate the mysterious interrelation between thymus and muscle. Some queer associations made us try the action ofthymus extracts on the growth of spontaneous mammary cancer in mice. So, willy-nilly, I found myself working on cell division, one of the most fundamental biological functions which involves most cellular activities. Some of our extracts retarded growth, others promoted it. We called the underlying retarding substance retine, the promoting one promine, and thought we had discovered thymus hormones. However, we soon found similar activities in the extracts of other tissues; retine and promine could thus not be hormones but were general tissue constituents. The evidence in hand was poor, but the idea that cell proliferation should be regulated by two antagonistic substances seemed attractive. To guide a horse, one needs reins and spurs. The isolation of these substances turned out to be a tough problem which could not be solved without some guessing. Such a guess was made when partially purified extracts showed a ketonic and aldehyde absorption in the infrared in the spectroscope of the Worcester Foundation for Experimental Biology. Could these substances, perhaps, be a-ketoaldehydes, derivatives ofglyoxal? This idea seemed exciting because living tissues contain an apparently ubiquitous and most active enzyme system, the glyoxalase, capable of transforming the reactive keto-aldehydes into

The mode of action of ovarian hormones in the induction of mammary cancer in mice

Abstract Prolactin seems to be the predominant agent in hormonal mammary gland carcinogenesis in mice. Oestrogens act mainly by promoting prolactin production. Progesterone is effective only in the presence of prolactin, acting synergistically with it.

Tumour incidence in mammary glands transplanted from the strains C3H and O20 into their mammectomized F1-hybrids.

AbstractIt has been demonstrated that genetic factors play an important role in the genesis of mammary cancer in mice but it was not known if the genetic action is localized in the mammary gland tissues or if the genetic influence is effective through some systemic mechanism. In this investigation the mammary glands from the inbred strains C3Hf and O20, differing in the incidence of mammary tumours, were transplanted into a common host, the F1 hybrid, so that systemic influences would be equal. A difference in susceptibility to tumour development was found between the transplanted C3Hf and O20 mammary glands. In the group of animals free of the agent there is a difference in tumour frequency. In the animals carrying the mammary tumour agent this difference is expressed in the average tumour age at which the tumours develop. The genetic susceptibility in these two strains is, therefore, retained in the transplanted mammary glands.Transplantation per se has no influence on tumour development.Transplanted mammary glands react in the same manner as mammary glands in situ. All transplantations have been done into completely mammectomized hosts to avoid interference with tumours developing in the glands of the host. Investigations with partly mammectomized animals have shown that the mammary tumour frequency and the average tumour age are related to the amount of mammary gland tissue present. A reduction of the mammary gland tissue also reduces the tumour frequency or delays the appearance of mammary tumours.

Studies on Trypanosoma cruzi isolated in the United States : A Review.

Studies on Trypanosoma cruzi isolated in the United States are reviewed. In the United States, nine species of triatomids and 14 species of mammals have been found infected with T. cruzi . Serologic studies for antibodies against T. cruzi in human beings are discussed. The epidemiology of T. cruzi infections in the United States differs from the classical pattern encountered in South America since infected insed hosts are found in trees and do not always defecate while feeding on the mammalian host. The infectivity and pathogenicity of animal strains of T. cruzi have been studied and are reviewed. Most strains are avirulent for mice. The cultural charaeteristics of several straii1s have been studied and the course of infection in mice examined. Differences among strains have been found. Immunologic studies have shown that avirulent North American strains of T. cruzi proteet mice against a virulent lethal South American strain. Attempts to differentiate strains serologically by the indireet hemagglutination test were not successful. Experiments to demonstrate that an infection with T. cruzi suppressed the development of mammary cancers in mice indicate that statistically significant differences between infected and uninfected groups of female mice were obtained. The basis for the protective relationship was not determined. T. cruzi in the United States is found in animals in the southern part of the country. Whether or not clinical disease in man takes place has not been demonstrated.

GENETIC CONCEPTS IN MAMMARY CANCER IN MICE

GENETIC CONCEPTS IN MAMMARY CANCER IN MICE

Genetic concepts in mammary cancer in mice.

Genetic concepts in mammary cancer in mice.

The influence of stress on mammary cancer in mice

The influence of stress on mammary cancer in mice

ReviewsBreast Cancer and its Diagnosis and Treatment. By LewisonEdward F., B.S., M.D., F.A.C.S., pp. xii + 478, 181 illus. with 4 coloured plates, 1st ed. (London, Bailliere, Tindall &amp; Cox), 114s.

In this book Professor Lewison and eight contributors sift the vast literature on breast cancer, combining this information with their own experience, thus providing mature conclusions and advice for all who are concerned with total care of the disease. Apart from usual chapters on history, anatomy, physiology, pathology, etc., Dr. Bittner writes on experimental aspects of mammary cancer in mice, Professor Huseby on hormonal alterations in palliative treatment, Dr. Urban on the extended radical operation, and Dr. Vincent Collins writes on radiotherapy. Some other chapter headings are Psychological Aspects, A Review of the Surgical Treatment, The Statistics of Breast Cancer There is also a chapter on cancer of the breast in the male.

CANCER BIOLOGY: COMPARATIVE and GENETIC*

CANCER BIOLOGY: COMPARATIVE and GENETIC*

The effects of oestrogens and progesterone on the chemical induction of mammary cancer in mice of the IF strain.

This experiment tests the hypothesis that progesterone may be necessary in addition to estrogen for the induction of mammary cancer in mice treated with the carcinogen 20-methylcholanthrene. Groups of IF strain (a low breast cancer strain) mice receiving hormonal treatments (estradiol dipropionate progesterone in varying dose schedules) were given a standard limited dose of 20-methylcholanthrene applied to the skin. Breast tumors occurred in 38% of normal virgin females but in only 3% of normal males and 10% of ovariectomized females receiving estrogen as the only hormonal treatment. The progesterone-estrogen combination treatment significantly increased the incidence of mammary cancer in normal males (30%) and in ovariectomized females (82%). In the groups of mice with a high incidence of mammary cancer histological changes reported as precancerous were frequent even when the individual mouse had no tumor; these precancerous changes were rare or absent in groups with a low incidence of breast cancer even in the few animals with breast cancer. The findings suggest that progesterone when combined with estradiol dipropionate acts as a promoting agent in mammary carcinogenesis induced by 20-methylcholanthrene. It is also possible that progesterone is important in the development of breast tumors in mice possessing the genetic agent.