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At least 595 records · Page 33Linked to original sources
PubMed1994

Cloning in a plasmid of an MMTV from a wild Chinese mouse: sequencing of the viral LTR.

Plasmid subcloning by conventional techniques of full length exogenous mouse mammary viruses (MMTV) has not been realized because of the involvement of host-mediated structural changes in the viral gag gene. To circumvent this problem, an alternative subcloning method, excision of phagemid (pBluescript SK) from lambda ZAP II, was successfully used to subclone a novel exogenous MMTV (JYG-MMTV) provirus fragment containing an intact gag gene. Sequence analysis revealed that the LTR of this virus is significantly different from the LTR of C3H-MMTV in the U3 region.

Amino Acid Sequence↗
PubMed1982

Prostaglandin regulation of murine mammary tumor virus production: a basis for some of the glucocorticoid and prolactin actions on mammary tumor cell cultures.

Hormonal regulation of mouse mammary tumor virus (MuMTV) production has been studied in cell cultures derived from mammary carcinomas of GR mice. The purpose of this study was to define the role of prolactin in dexamethasone-induced MuMTV production and to evaluate the mechanism(s) of action of these hormones. Results of our investigations in vitro establish a central role for prostaglandins, in particular PGF2 alpha. Prolactin treatment up to 1000 ng/ml increased the MuMTV production only slightly when added alone but a maximal stimulatory response was expressed when prolactin was added simultaneously with dexamethasone 2 micrograms/ml. This prolactin-related enhancement of MuMTV production was probably mediated by PGs since it was inhibited by indomethacin, an inhibitor of prostaglandin synthesis. When higher concentrations of indomethacin were used in dexamethasone-treated cultures, MuMTV production, although inhibited, was restored in part by addition of exogeneous PGF2 alpha. PGF2 alpha added alone stimulated the MuMTV production and, in combination with dexamethasone, showed a synergistic effect on stimulation of MuMTV production. Two compounds, PGF2 alpha and TXA2 (measured as TXB2), were produced in significant concentrations by these cultures. These findings suggest that PGF2 alpha exerts a regulating role on production of MuMTV in GR cells and indicate that the actions of both dexamethasone and prolactin are mediated at least in part by prostaglandins.

Animals↗
PubMed1983

Tissue and organ distribution of mammary tumor virus antigens in low and high mammary cancer strain mice.

Expression of mammary tumor virus (MTV) antigen was measured in a wide variety of organs and tissues of a series of high (GR, SHN, SHNf, DD, SLN, SLNf) and low (DDf, DDD, DDDf, KF, KFf, ddY, C57BL, BALB/c) mammary cancer strain mice. Tests were carried out by microimmunodiffusion (micro-ID) and immunoperoxidase tests on formalin-fixed tissues and radioimmunoassays in extracts for 2 viral proteins, MTVp27 from the viral core and MTVgp52 from the viral envelope. Organs with exocrine function, i.e. the mammary gland, salivary gland, coagulating gland and prostate, were mostly positive. The secretory epithelial cells of these organs showed viral antigen expression. Less positivity was encountered in brain, pancreas, stomach, urinary bladder, epididymis, uterus, thymus, spleen, lymph nodes and kidney, plasma and blood cell pools. Unexpectedly the uterus extracts showed MTV antigen expression, occasionally even by immunodiffusion, especially in mice of various DD stocks, but also in the GR strain. Another striking observation was the detection of MTV antigen expression in salivary glands in C57BL strain mice; most other organs of this strain (including the mammary glands) were negative. The implications of results of this extensive survey for MTV antigen expression are discussed for tumorigenesis by MTV of mammary gland and perhaps other tissues in the mouse.

Animals↗
PubMed1990

DNA rearrangements of the int region in spontaneous mouse mammary tumors of SHN/S and SLN/S mice.

SHN and SLN mice originating from the same Swiss albino stock are genetically very close to each other. The incidence and latent period of mammary tumor development in SHN mice were higher and shorter than those in SLN. To elucidate these differences in the behavior of mammary tumorigenesis, the frequency of insertion of mammary tumor viral genes within the int-1 and int-2 regions in spontaneous mammary tumors from their two substrains, SHN/S and SLN/S, were compared. The frequency of provirus integration into either int-1 or int-2 in DNAs from mammary tumors was 52% (11/21) in SHN/S and 45% (5/11) in SLN/S. The frequency of insertion within int-1 or int-2 could not account for the different susceptibilities of SHN/S and SLN/S.

Animals↗
PubMed1980

Selenium-mediated inhibition of mouse mammary tumorigenesis.

The effects of selenium of mouse mammary tumorigenesis were examined in 2 systems. BALB/cfC3H (MuMTV-S positive) given 2 and 6 ppm selenium in the drinking water and maintained as breeding mice, had significantly lower incidences of mammary tumors (48% and 12%, respectively) than untreated control mice (82%). Selenium at 4 ppm inhibited the tumor-producing capabilities of only 1 of 4 preneoplastic outgrowth lines maintained in BALB/c (MuMTV-S negative) mice. Selenium at 2, 4 and 6 ppm had no effect on the growth rate of primary mammary tumors transplanted subcutaneously in BALB/c mice. Selenium inhibited mammary tumorigenesis without interference of normal reproductive function and weight gain.

Animals↗
PubMed1984

Nucleocytoplasmic release of repetitive DNA transcripts in carcinogenesis correlates with a 60 kilodalton cytoplasmic protein.

Treatment of rats with the hepatocarcinogen 3'-methyl-4-dimethylamino-azobenzene (3'-MeDAB) causes the appearance in the liver cytosol of a 60 kilodalton oncofetal protein. The appearance of this factor occurs within 40 h of treatment and coincides with the increase in the amount of rapidly labeled RNA released from nuclei in a reconstituted cell-free system. Cross-over experiments show that this increase is due to an enhanced transport capacity of the cytosol. The 60 kilodalton RNA transport factor is also present in the cytosol of tumor cells. Addition of the 60 kilodalton factor to normal liver cytosol causes the transport of repetitive RNA sequences similar to those transported from liver nuclei to tumor cell cytosol and those transported to the tumor cell cytoplasm in vivo. This factor modifies nuclear RNA restriction, at least in part, by eliciting the transport of repetitive RNA normally retained within the nucleus of the normal cell.

Animals↗
PubMed1984

Selenium inhibition of the neoplastic transformation in preneoplastic mammary cell populations.

The effect of dietary selenium on the tumor-producing capabilities of primary hyperplastic alveolar nodules (HAN) of the mammary gland of BALB/c mice was examined directly using a transplantation assay. The tumor-producing capabilities of primary HAN exposed to 2.0 ppm dietary selenium was decreased 57% compared to the tumor-producing capabilities of HAN exposed to 0.2 ppm dietary selenium. This degree of inhibition compared well with the 60% inhibition of mammary tumorigenesis when the mice were exposed to supplemental selenium during the entire tumorigenic period. The examination of primary hyperplastic alveolar nodules was a more accurate assessment of the responsiveness of the preneoplastic state than using established nodule outgrowth lines since the latter exhibited a greater degree of variability in response to selenium-mediated inhibition of growth and the mean response of numerous nodule outgrowth lines was not as great as seen in the primary HAN. These results indicate that selenium is an effective inhibitor of the neoplastic transformation in preneoplastic cells as well as the formation of preneoplastic cells.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1987

Genetic resistance to mammary tumorigenesis in a mouse strain with high murine mammary tumor virus expression.

Although II-TES mice release large amounts of murine mammary tumor virus (MMTV) in milk, they are resistant to mammary tumorigenesis. High mammary tumor incidence was observed in (BALB/ca X II-TES)F1 and (C57BL/6N X II-TES)F1, whereas no mammary tumors developed in BALB/ca X OZ-F)F1. Mammary tumors developed in 68% of (OZ-F X (OZ-F X II-TES)F1 and 45% of (II-TES X (OZ-F X II-TES)F1). These results suggest that the II-TES mouse carries a recessive gene for mammary tumor resistance which does not inhibit MMTV release, and two independent dominant mammary tumor promoting genes which are inhibited by the resistant gene.

Animals↗
PubMed1990

Establishment of DDD/1-Mtv-2/Mtv-2, nu/nu and DDD/1-Mtv-2/Mtv-2, nu/+ mice: preliminary characterization in relation to MTV antigen expression and mammary tumorigenesis.

To investigate the effects of the T-cell deprivation on viral mammary tumorigenesis, two double congenic mouse strains of the DDD genetic background, DDD/1-Mtv-2/Mtv-2, nu/nu and DDD/1-Mtv-2/Mtv-2, nu/+, were produced by the cross between DDD/1-Mtv-2/Mtv-2 (DDD-Mtv-2) and DDD/1-nu/nu mice, followed by repeated intercross breedings. Expression of the mouse mammary tumor virus (MTV)-gp52 antigen was demonstrated in the mammary glands of mice from 14 days on, in both -nu/nu and -nu/+ females. Mammary gland development was comparable in both strains, but, the incidence of mammary cancer was lower in the T-cell-deprived mice.

Animals↗
PubMed1992

Effects of alprazolam on the development of MTV-induced mammary tumors in female mice under stress.

Female C3H/He mice carrying the mammary tumor virus (MTV) were monitored for mammary tumor incidence and latent periods while subjected to a daily intraperitoneal (i.p.) injection of placebo or alprazolam (1 mg/kg per day). Although all of the mice were potential candidates for MTV-induced breast cancer, those injected with alprazolam were partially protected against adverse effects of stress induced by the daily administration of placebo.

Age Factors↗
PubMed1993

Lipids alter the level and distribution of mouse mammary tumor virus gp52 in vitro.

Linoleic acid, cholesterol, dexamethasone and progesterone were tested by immunocytochemistry and immunoprecipitation for their single and combined effects in vitro on mouse mammary tumor virus (MMTV) gp52 distribution among three compartments: cell-associated antigen, extracellular virus particles and extracellular shed antigen unassociated with virus particles. Results indicated that all additives significantly increased total MMTV gp52 levels and altered the distribution. Linoleic acid and dexamethasone induced the greatest relative proportion of extracellular gp52, whereas cholesterol and progesterone induced the greatest proportion of cell-associated gp52. The implications of these findings for the immune response to mammary tumors is discussed.

Analysis of Variance↗
PubMed1994

Dietary regulation of mammary tumorigenesis in RIII/Sa mice: investigation of a possible mechanism.

The effects of caloric restriction on the incidence of mammary tumor development, the levels of the expression of mouse mammary tumor virus (MMTV)- and prolactin-RNA, as well as the levels of serum prolactin, were investigated in virgin RIII/Sa mice, a strain known to display a high incidence of spontaneous mammary tumor development. Of the 54 mice fed a low-calorie (LC; 10 kcal/day) diet containing low fat (LF; 5% corn oil) for a period of 72 weeks, only seven mice were found to develop mammary tumors, an incidence of 13%. By contrast, the cumulative tumor incidence in a similar sized group of mice, fed a high-calorie (HC; 16 kcal/day) low fat-containing diet was 73%. Estimation of the relative levels of MMTV-RNA, as determined by Northern and slot blot hybridizations, in the mammary glands of mice fed LCLF and HCLF diets for 8, 10, 16, 28, and 36 weeks revealed that the LCLF diet-fed mice expressed 4-15-fold less RNA than the HCLF diet-fed mice. Interestingly, however, the LCLF diet did not appear to exert any effect on the expression of prolactin RNA even though it reduced the levels of serum prolactin. We suggest that in RII/Sa mice the modulation of MMTV-induced mammary tumors by dietary calorie is linked to the secretion of serum prolactin which, in turn, affects the replication of MMTV required for mammary cell transformation.

Animals↗
PubMed1979

The cause of species differences in mammary tumourigenesis: significance of mammary gland DNA synthesis.

The causes of species differences in mammary tumourigenesis are briefly discussed from the genetical and environmental points of view, although no firm conclusions can be drawn. Distinct differences in mammary gland DNA synthesis were found between female mice and rats, which behave very differently in mammary tumourigenesis. Based on the importance of mammary gland DNA synthesis in mammary tumourigenesis, the differences in mammary gland DNA synthesis between species is hypothesized to be a major cause of the species differences in mammary tumourigenesis.

Aging↗
PubMed1989

Localizing efficiency of [48V]vanadyl-pheophorbide in tumor as a new tumor imaging agent.

[48V]vanadyl-pheophorbide (48V-Pheo) was synthesized by insertion of 48V into pheophorbide (Pheo), a decomposition product from chlorophyll. At 24 h after injection, 48V-Pheo showed a clearer image of an FM3A tumor than inorganic 48V. This agent also accumulated in MH 134 and S 180 tumors as well as in FM3A tumors. The imaging efficiency was dependent on the affinity of Pheo for tumors. 48V-Pheo seems to be suitable as a tumor imaging agent in conjunction with photodynamic therapy.

Animals↗
PubMed1986

Purification of antigens of mammary tumor of the mouse by gel filtration.

This study was designed to isolate the biologically active components from a perchloric acid (PCA) extract of mammary tumor virus (MTV)-induced mouse mammary tumors (AMMT) previously shown to be capable of inducing DNA synthesis in spleen cells of mice presensitized by inoculation of viable syngeneic mammary tumor cells. AMMT (450 mg) was eluted fom an Ultrogel AcA54 column with separation range of 5-70K in a buffer containing Tris-sodium chloride and EDTA. Two fractions were separated with estimated molecular weights of 68-70K (AMMT I) and 35-40K (AMMT II). AMMT I and AMMT II exhibited DNA synthetic activity 78-fold and 35-fold, respectively, greater than AMMT. The feasibility of further purification of AMMT I by isoelectric focusing was also demonstrated. These components provide the opportunity for further investigation into the molecular basis of tumor-host relationship in this animal model.

Animals↗
PubMed2006

Gene expression array analyses predict increased proto-oncogene expression in MMTV induced mammary tumors.

Exogenous infection by milk-borne mouse mammary tumor viruses (MMTV) typically induce mouse mammary tumors in genetically susceptible mice at a rate of 90-95% by 1 year of age. In contrast to other transforming retroviruses, MMTV acts as an insertional mutagen and under the influence of steroid hormones induces oncogenic transformation after insertion into the host genome. As these events correspond with increases in adjacent proto-oncogene transcription, we used expression array profiling to determine which commonly associated MMTV insertion site proto-oncogenes were transcriptionally active in MMTV induced mouse mammary tumors. To verify our gene expression array results we developed real-time quantitative RT-PCR assays for the common MMTV insertion site genes found in RIII/Sa mice (int-1/wnt-1, int-2/fgf-3, int-3/Notch 4, and fgf8/AIGF) as well as two genes that were consistently up regulated (CCND1, and MAT-8) and two genes that were consistently down regulated (FN1 and MAT-8) in the MMTV induced tumors as compared to normal mammary gland. Finally, each tumor was also examined histopathologically. Our expression array findings support a model whereby just one or a few common MMTV insertions into the host genome sets up a dominant cascade of events that leave a characteristic molecular signature.

Animals↗