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At least 289 records · Page 16Linked to original sources
PubMed1987

Enhancement of tumorigenicity with morphological progression in a BALB/c preneoplastic outgrowth line.

Four newly established mammary hyperplastic outgrowth lines were analyzed for their tumorigenic, morphological, and ovarian hormone-dependent growth properties in BALB/cMed mice. The mammary outgrowth lines were designated DIM-1, DIM-2, DIM-3, and DIM-4 to indicate their origin from the mammary cell line COMMA-D. DIM-1, DIM-2, and DIM-3 were classical hyperplastic alveolar outgrowth lines that possessed high tumor-producing capabilities and rapidly evolved by transplant generation (TG) 6 into ovarian hormone-independent populations. DIM-3 was also characterized by extensive formation of dilated (cystic) alveoli. This characteristic did not correlate either positively or negatively with the tumor-producing capabilities of these lines. DIM-4 was a ductal outgrowth line that exhibited a progression in several biological properties. This line progressed morphologically from a ductal outgrowth to a mixed outgrowth of small ducts (ductules) with scattered alveoli and then in subsequent passages to a uniform alveolar outgrowth. Concurrent with these morphological changes, the tumor-producing capabilities of DIM-4 increased from low [40% with the time for 50% of the transplants to produce mammary tumors (TE50) greater than 12 mo] to high (71% with a TE50 of 7.1 mo). The ductal outgrowth line (TG 4) was totally dependent on ovarian hormones for growth; however, later passages (TG 8) of DIM-4 were only partially ovarian hormone dependent for growth and ovarian hormone independent for maintenance of alveolar morphology. In addition, the tumorigenic response to 7,12-dimethylbenz[a]anthracene (CAS: 57-97-6) was low in the ductal stage (TG 4) and high in the alveolar stage (TG 7). The results demonstrate an enhancement of tumorigenicity with morphological and biological progression in a preneoplastic mammary cell population and support the hypothesis that the cells at high risk for tumorigenesis in the BALB/c mammary gland appear to be the alveolar cell type.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1980

Correlation between the detection of specific mouse mammary tumor proviral sequences and the presence of pulmonary metastases in mice bearing spontaneous mammary tumors.

Pulmonary metastases in C3H/He mice bearing spontaneous mammary tumors were detected and characterized by histological criteria and immunocytochemical staining for mouse mammary tumor virus antigens. The same lungs containing metastases were also positive when assayed for a specific subset of mouse mammary tumor virus proviral DNA sequences. These sequences, termed tumor-associated sequences, have previously been shown to be present in the DNA of spontaneous mammary tumors that arise before 1 yr of age in C3H/He mice but are absent in DNA's of apparently normal tissues of C3H/He mice. Reconstruction experiments demonstrated that the nucleic acid hybridization method will detect at least one mammary tumor cell/250 cells. While DNA from 13 lungs of apparently normal C3H/He mice did not contain sequences homologous to mouse mammary tumor virus tumor-associated-sequence RNA, DNA from lungs of 9 of 12 C3H/He mice bearing spontaneous mammary tumors did contain these sequences. Since the entire DNA content of the lung can be assayed as one sample, the hybridization method minimizes false negatives resulting from histological analysis of random biopsy sampling. The hybridization procedure described here thus represents a sensitive and quantitative element as an adjunct for the detection of micrometastatic lesions in mice bearing viral-mediated spontaneous mammary carcinomas.

Animals↗
PubMed1980

Reevaluation of the effect of mouse mammary tumor virus infection on the BALB/c mouse hyperplastic outgrowth.

The BALB/c (C-) mouse hyperplastic outgrowth line (D1) was used to study murine mammary tumor virus (MuMTV) expression in both D1 and tumors derived from D1. D1 was transplanted into virus-infected BALB/cfC3H (C+) and virus-uninfected C- animals. In duplicate studies, tumor incidence was the same in both groups. However, the tumor latency period was longer for D1 transplanted into C+ mice (D1/C+) than for D1 transplanted into C- mice (D1/C-). MuMTV was detected in 85% of D1/C+ outgrowths and in 29% of D1/C+ tumors but was never detected in D1/C- outgrowths or tumors. D1/C- outgrowth and tumors and most of the D1/C+ tissues expressed little or no MuMTV RNA. Some D1/C+ tumors expressed substantial levels of MuMTV RNA. These same tumors also had MuMTV antigen and contained the exogenously acquired C3H-MuMTV provirus in the cellular DNA as shown by DNA fragment patterns following cleavage with Pst I and Eco RI endonucleases. D1/C+ tumors containing no viral RNA were also antigen-negative and lacked the acquired C3H provirus. These studies indicate that D1 has substantially changed in its incidence and in its response to MuMTV. MuMTV infection was not tumorigenic in the traditional sense, a finding that has led to a reevaluation of our current models of virus-host relationships and the biology of precancerous conditions.

Animals↗
PubMed1982

A high-tumor-incidence subline of the D1 mouse mammary hyperplastic outgrowth line: effect of carcinogens.

Mammary tumorigenesis in some mouse strains is characterized by the appearance of a preneoplastic lesion, the hyperplastic alveolar nodule (HAN). The biology of the HAN has been characterized primarily through the study of stable outgrowth lines of serially transplanted HAN. One outgrowth line, Dl, which was developed and carried in female BALB/c mice, has been described as a low-tumor-incidence line that does not express murine mammary tumor virus (MuMTV) and is susceptible to hormonal, chemical, and viral carcinogens. In this report, a high-tumor-incidence subline of Dl, Dl/UCD, is described. Although Dl/UCD, like Dl, is susceptible to the chemical carcinogen 7,12-dimethylbenz[a]anthracene, an increase in tumor incidence was not observed when Dl/UCD outgrowth was exposed to hormones by means of pituitary isografts. Unlike Dl, Dl/UCD is refractory to the carcinogenic action of MuMTV. Both Dl and the Dl/UCD subline contained the endogenous MuMTV provirus but did not contain exogenous MuMTV provirus sequences. MuMTV antigen was not detected in Dl/UCD outgrowths or tumors. RNA hybridizable to MuMTV complementary DNA was detected in some Dl/UCD outgrowths and tumors but did not appear to correlate with tumorigenesis.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1973

Intracytoplasmic A particles: mouse mammary tumor virus nucleoprotein cores?

A rapid method for the isolation of intracytoplasmic A particles, the putative intracellular nucleoprotein cores of mouse mammary tumor virus (MTV), is presented. Spontaneous C3H/He mouse mammary tumors and transplantable mouse Leydig cell tumor were used as source material. Large aggregations of intracytoplasmic A particles were separated from cellular contaminants on discontinuous sucrose gradients and subsequently further purified by isopycnic banding in linear sucrose gradients. The purified particles were solubilized in sodium dodecyl sulfate, and the structural proteins were analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Purified mouse mammary tumor virions were solubilized, and their proteins were analyzed in the same way. Comparison of co-electrophoretic gels indicated a lack of correlation in the molecular size of the major structural proteins in intracytoplasmic A particles and MTV. The three major proteins of the A particles were calculated to be 80,000; 35,000; and 20,000 daltons. Five major polyacrylamide gel electrophoresis bands were obtained with purified MTV; these were 90,000; 69,000; 55,000; 37,000; and 27,500 daltons. These figures showed good correlation with those published for MTV by Nowinski et al. These results suggest the need for the reexamination of the current tenet that intracytoplasmic particles represent intracellular MTV nucleoprotein cores.

Animals↗
PubMed1995

Clonal variations among multiple primary mammary tumors and within a tumor of individual mice: insertion mutations of int oncogenes.

Laboratory mice infected with the mouse mammary tumor virus (MMTV) often develop multiple mammary tumors. However, no comprehensive studies have been done addressing the question of whether or not different primary tumors of individual mice are related ontogenetically to each other. Further, it is not known to what extent individual tumors vary in their cellular composition. We, therefore, examined intertumor and intratumor patterns of the rearrangements in int-1 (Wnt-1), int-2 (Fgf-3), and int-3 protooncogenes, since mutations in ints caused by MMTV result in the development of mammary tumors in mice and thus provide the most suitable genetic markers for the tumor cells. Our results show that, irrespective of the genetic background of the mice and/or the strain of MMTV, the pattern of MMTV integration in the different tumors of individual mice varies as widely as is found with the tumors of different mice. Of the 79 tumors obtained from 25 mice of different genetic backgrounds, 31 showed insertional mutations in int-1 (39%). By contrast only 9 of the 65 tumors tested had mutations in int-2 (14%). None of the tumors showed mutations in int-3. Interestingly, tumors from individual mice also showed variations in their pattern of int gene mutation, indicating that multiple tumors that develop in a mouse bear no ontogenetical link. The analysis of the pattern of intratumor MMTV integration, int mutation, and int expression revealed that several int mutational events as well as variations in int expression may occur in the same tumor. The diversity of int activation within individual tumors may suggest that the initiation and progression of most mammary tumors, if not all, occur through the concerted action of different mutational events in the same cell or through interactions of different cell populations, each of which acquired different int mutations.

Animals↗
PubMed1989

Estrogen influence on maturational pathway of murine mammary tumor virus: an immunoelectron microscopy study.

Modifications induced by estrogens on hormone-independent murine mammary tumor (MMT) and its main etiological agent, the MMT virus (MMTV), are reported. High doses of estrogens released continuously from silastic capsules delay significantly the development of transplanted tumors into syngeneic hosts. Neoplastic cells present a striking cytoplasmic vacuolization and changes in the MMTV differentiation pattern. Mature virions are detected budding into cytoplasmic vacuoles instead of the extracellular space as in spontaneous and untreated transplanted tumors. This phenomenon is reversed after estrogen withdrawal at the first sign of tumor development. Application of electron microscope immunocytochemistry with colloidal gold-protein A complex and multiple monospecific antibodies reveals several interesting features. In spontaneous and untreated tumor grafts, structural viral proteins p14 and p25 appear in both intracytoplasmic capsids and mature extracellular viruses. By contrast glycoprotein gp55 labels only the envelope of mature virus. In estrogen-treated tumors this antigenic pattern is modified and the gp55 is detected in those atypical virions maturing into the intracytoplasmic vacuoles. These observations led to the conclusions that the delay in the development of hormone-independent mammary tumors caused by estrogen is due to an abnormal maturational viral process and that estrogens induce alterations of polarity in the translocation process of viral envelope glycoproteins.

Animals↗
PubMed1991

The mouse biliary glycoprotein gene (Bgp): partial nucleotide sequence, expression, and chromosomal assignment.

Transcripts related to the human carcinoembryonic antigen were found in mRNA isolated from both dimethylbenzanthracene-induced and mouse mammary tumor virus-induced mammary tumors. A cDNA library was prepared from a dimethylbenzanthracene-induced tumor, and a clone was isolated by hybridization with a human carcinoembryonic antigen cDNA probe. Its sequence, when compared to those of members of the human carcinoembryonic antigen gene family, was most homologous to the sequence of the human biliary glycoprotein (BGP) gene. Thus, this clone appears to encode a portion of the mouse biliary glycoprotein gene. Southern blot analysis of EcoRI-digested mouse cellular DNA with this probe detected four restriction fragments, all of which appear to be located on mouse chromosome 7, Northern blot analysis using the mouse probe demonstrated that related mRNA species were expressed in some normal adult mouse tissues.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed2001

Expression of the androgen-dependent MMTV-specific orf gene in Shionogi 115 mouse mammary tumor cells.

The Shionogi 115 (S115) mouse mammary tumor cells express the MMTV-specific 1.7 kb mRNA (orf) at a high level in the presence of androgens. In lymphoid cells the orf-gene encodes a superantigen which has an important role in establishing self-tolerance but in mammary and breast cancer cells the function of the orf gene is unclear. In the present work we studied the expression of the S115 mammary tumor cell orf sequence and its role in the androgen regulated growth of S115 cells. The cloning and sequencing of the cDNA specific for the 1.7 kb mRNA from the S115 mouse mammary tumor cells revealed a 990 bp DNA sequence with a 99.8% homology to the Mtv-17 proviral strain. There was a difference of only one amino acid (isoleu-tyr) in the coding region. A peptide was synthesized according to the hypervariable C-terminal part of the predicted protein and used to raise a rabbit antiserum. The anti-S115-orf antiserum immunoprecipitated an approximately 45 kDa protein from the metabolically labeled S115 cell lysates. In order to analyze the putative functions of the protein, the orf-sequence was linked to MoMLV-LTR and to the human ss-actin promoter in the mammalian expression vectors pLTRpoly and pHssAPr-1-neo, respectively, and transfected into NIH3T3 and S115 cells. NIH3T3 transfectants expressing orf mRNA did not show a transformed phenotype in vitro. The S115 orf transfectants proliferated somewhat more slowly than the vector transfected control cells in cell culture, both in the presence or absence of androgen, but there was no obvious change in the phenotype of S115 cells or in expression of the fibroblast growth factor 8 (FGF-8). This factor is activated by Mtv-6 integration and mediates androgen effects in these cells. Unexpectedly, however, the formation of tumors by S115 orf cells in nude mice was considerably prolonged and tumor growth retarded when compared with vector transfected control or parent S115 cells. The results suggest that MMTV-orf can be functional in breast cancer cells but the mechanism of the growth repressive effect in mammary tumor remains to be analyzed.

3T3 Cells↗
PubMed1998

MMTV-Fgf8 transgenic mice develop mammary and salivary gland neoplasia and ovarian stromal hyperplasia.

Prior studies have identified Fibroblast Growth Factor-8 (Fgf8) as a possible proto-oncogene in mouse mammary tumorigenesis. We now report on the generation of two types of Fgf8 transgenic mice that each utilize the mouse mammary tumor virus (MMTV) promoter. The first transgene (MMTV-Fgf8b) results in the overexpression of the FGF8b isoform exclusively. Male and female MMTV-Fgf8b transgenic mice are viable and fertile. RNA for FGF8b is detected in mammary gland and salivary gland tissues of transgenic mice by Northern blot analysis. Nearly 85% of breeding transgenic female mice developed mammary lobular adenocarcinomas by 12 months of age, while no tumors developed in non-transgenic littermates. Salivary gland tumors occurred in some animals, always in association with mammary tumors. Several MMTV-Fgf8b transgenic mice had lung metastases at necropsy. The second transgene (MMTV-Fgf8) uses the entire Fgf8 gene and potentially encodes all FGF8 isoforms. Fgf8 is expressed by this transgene in several tissues in addition to those described above, notably the ovaries. The two MMTV-Fgf8 founders developed mammary ductal adenocarcinomas at five and eight months of age, and both displayed ovarian stromal hyperplasia. The founders expressing either transgene did not successfully nurse their pups. These results demonstrate that production of FGF8b, and possibly other FGF8 isoforms, in the mammary and salivary glands contributes to oncogenesis, and that ovarian expression results in stromal hyperplasia.

Adenocarcinoma↗
PubMed1995

Dietary lipids and calorie restriction affect mammary tumor incidence and gene expression in mouse mammary tumor virus/v-Ha-ras transgenic mice.

We have studied the effects of food restriction (FR) and substitution of fish oil (FO; omega 3) for corn oil (CO; omega 6) on breast tumor incidence and survival in mouse mammary tumor virus/v-Ha-ras transgenic (Onco) mice. The diets were as follows: group 1, 5% (wt/wt) CO fed ad libitum (AL); group 2, 5% CO, restricted calories (40% fewer calories than AL; FR); group 3, 20% CO fed AL; and group 4, 20% FO fed AL. After 3 years, 40% of FR Onco (group 2) mice were alive, whereas there were no survivors in the other three groups. Similarly, tumor incidence was reduced to 27% (5 out of 18) in FR animals (group 2), whereas it was 83% (11 out of 13) in group 1 mice, 89% (16 out of 18) in group 3 mice, and 71% (10 out of 14) in group 4 mice. These protective effects of FR on survival and tumor incidence were paralleled by higher expression of the tumor suppressor gene p53 (wild type) and free-radical scavenging enzymes (catalase and superoxide dismutase) in breast tumors. Immunoblotting showed less ras gene product, p21, and increased p53 levels in the tumors of FR mice. In addition, FR decreased RNA levels of c-erbB-2, interleukin 6, and the transgene v-Ha-ras in tumors. In contrast, analysis of hepatic mRNA from tumor-bearing FR mice revealed higher expression of catalase, glutathione peroxidase, and superoxide dismutase. Survival and tumor incidence were not influenced significantly by dietary supplementation with FO in place of CO. Taken together, our studies suggest that moderate restriction of energy intake significantly inhibited the development of mammary tumors and altered expression of cytokines, oncogenes, and free-radical scavenging enzymes.

Animals↗