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Query: UMLS:C0027651 (tumor)
 685,946 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A complementary DNA (cDNA) probe to mouse mammary tumor virus (MMTV) RNA was synthesized using calf thymus DNA oligonucleotides as a random primer. This probe was then used to study the expression of MMTV RNA in cell lines from BALB/c tumors induced in vivo either spontaneously or in response to viral, chemical, or hormonal stimuli. The cDNA had a length of approximately 400 to 500 nucleotides and specifically hybridized to MMTV RNA and BALB/c lactating mammary gland RNA, but not to Moloney leukemia virus RNA. Calf thymus DNA-primed cDNA could protect 50% of iodinated MMTV RNA from S1 nuclease digestion at cDNA-RNA ratios of 1:1 and 90% of labeled viral RNA at ratios of 10:1. Thermal denaturation of MMTV RNA-cDNA hybrids yielded a T(m) of 88.5 degrees C, indicative of a well-base-paired duplex. Screening of mouse mammary tumor cells for MMTV sequences revealed that three out of five lines of BALB/c origin had undetectable levels of viral RNA (<three molecules per cell) by RNA excess hybridization. Two of the three "virus-negative" cell lines were derived from tumors induced by the chemical carcinogen 7,12-dimethylbenz(alpha)anthracene, whereas the third tumor occurred spontaneously. Two lines from tumors induced by either viral (mammary tumor virus) or hormonal (17-beta-estradiol) stimulus contained between three and nine molecules of MMTV RNA per cell by both RNA excess and cDNA excess hybridization. Clonal derivatives of these tumor lines had levels of viral RNA comparable to those of their parental lines. Therefore, it appears that the presence of detectable MMTV RNA sequences is not a necessary requirement for the maintenance of all murine mammary gland neoplasias.
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PMID:Detection of mouse mammary tumor virus RNA in BALB/c tumor cell lines of nonviral etiologies. 21 78

The effect of various tumor initiators and promoters on induction of persisting Epstein-Barr virus (EBV) in different lines of lymphoblastoid cells was analyzed. Neither five polycyclic aromatic hydrocarbons, amongst them potent tumor initiators (e.g., 7,12-dimethylbenz[a]anthracene), nor the potent (ultimate) liver carcinogen N-acetoxy-N-2-acetylamino-fluorene induced EBV. A series of compounds, representing three classes of tumor-promoting diterpene esters (e.g., 12-O-tetradecanoylphorbol-13-acetate), efficiently induced EBV in persistently infected cells. The concentration required for maximal induction ranged between 0.5 and 100 nM. Some nonpromoting diterpenes (phorbol, 4alpha-phorbol-12,13-didecanoate, and ingenol) did not induce EBV. However, the nonpromoters, resiniferatoxin and 12-deoxyphorbol-13-decatrienoate, were effective, whereas anthralin, a tumor promoter, did not induce EBV. In three lines of EBV genome-carrying cells (Raji, NC-37, and RPMI 64-10) only abortive induction was noted, leading exclusively to synthesis of early antigen. In cells of lines with low spontaneous virus release (P3HR-1, B95-8, and QIMR-Wil), upon treatment with tetradecanoylphorbol acetate, approximately 20-40 times more viral DNA was recovered as compared to untreated controls. Viral DNA from tetradeca-noylphorbol acetate-induced cultures revealed the same restriction endonuclease cleavage pattern as viral DNA obtained from noninduced cells. Within 10 days after induction, release of infectious virus increased approximately by one order of magnitude. Prostaglandins, reported to be released after treatment with tumor promoters, were ineffective in virus induction under the conditions tested.
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PMID:Tumor initiators and promoters in the induction of Epstein-Barr virus. 21 19

Approximately 70% of primary 7,12-dimethylbenz(alpha)-anthracene-induced mammary tumors regressed when (tumor-bearing) rats were made diabetic after treatment with streptozotocin. In the intact animal, cyclic adenosine 3':5"-monophosphate (cAMP) levels of tumors that regressed following the induction of diabetes were initially 4-fold lower than in unresponsive tumors but increased 4-fold during regression. The insulin-independent tumors showed no statistically significant changes. cAMP binding in cytosol of regressing tumors was about 80% above the initial values at 36 hr after therapy but decreased to about 45% 1 week later. On the contrary, the binding capacity of the nuclei showed a 56% increase at 36 hr and increased gradually to about 3-fold 1 week later. Within 36 hr after treatment, total histone kinase activity increased 127% in the cytosol and 153% in the nuclei of regressing tumors. The increment of histone kinase activity was almost totally in the cAMP-dependent component of the enzyme. These changes were not apparent in insulin-independent tumors. The results are interpreted to indicate that mammary tumor regression due to diabetes involves the cAMP system and occurs through a sequence of events similar to those observed during regression induced by either ovariectomy or dibutyryl cAMP (cyclic adenosine 3':5'-monophosphate) treatment.
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PMID:Cyclic adenosine 3':5'-monophosphate and protein kinase activity in insulin-dependent and -independent mammary tumors. 22 Nov 6

Adenosine 3',5'-monophosphate (cyclic AMP) receptor protein of 56,000 daltons increases markedly in mammary tumors induced by 7,12-dimethylbenz[a]anthracene (DMBA) after incubation of tumor slices with cyclic AMP, benzamide, and arginine. Incubation of cytosol from these tumor slices with nuclei from unincubated tumors results in nuclear uptake of the 56,000-dalton cyclic AMP receptor and in phosphorylation of the 76,000-dalton nuclear protein. Binding of the 56,000-dalton receptor and phosphorylation of the 76,000-dalton protein also occur in DMBA tumor nuclei when protein kinase type II of bovine heart is used. The results suggest that cyclic AMP receptor is involved in the nuclear events of a hormone-dependent mammary tumor.
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PMID:Cyclic AMP receptor triggers nuclear protein phosphorylation in a hormone-dependent mammary tumor cell-free system. 22 63

Involvement of mouse mammary tumor virus (MMTV) in 7,12-dimethylbenz[a]anthracene (DMBA)-induced mammary tumorigenesis was investigated in low- (BALB/c) and high- (BALB/cfC3H) mammary-tumor-incidence mouse strains. Both strains contain endogenous MMTV integrated into the cellular genome. Additionally, BALB/cfC3H mice are infected with exogenous MMTV-S which is responsible for a higher incidence of mammary tumors in breeding females. Administration of DMBA to virgin mice of both strains resulted in a moderate frequency of mammary tumors within 40 wk after treatment. No differences were found in DMBA-induced tumor incidences at 18 wk (6% and 7%) or at 38 wk (29% and 36%) after treatment of BALB/c and BALB/cfC3H mice, respectively. Expression of MMTV in these tumors was examined by assaying for the presence of MMTV RNA by hybridization using MMTV-specific cDNA and by immunohistochemical staining utilizing antibodies against MMTV 52,000-dalton glycoprotein, gp52, and 28,000-dalton internal protein, p28. Of 16 BALB/c tumors assayed, 11 did not contain detectable levels of MMTV RNA and the remaining 5 tumors contained only low levels (0.0005-0.0010%) of viral RNA. Importantly, MMTV RNA was not detected in 5 of 27 BALB/cfC3H tumors. The other BALB/cfC3H tumors contained quantities of MMTV RNA ranging from 0.0006 to 0.4170%. Most BALB/cfC3H tumors with detectable levels of MMTV RNA also synthesized viral proteins gp52 and p28. Thus, expression of the complete MMTV genome is not requisite for maintenance of the tumor phenotype in DMBA-induced mammary tumors in either BALB/c or BALB/cfC3H virgin mice under 1 year of age.
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PMID:Mouse mammary tumor virus genome expression in chemical carcinogen-induced mammary tumors in low- and high-tumor-incidence mouse strains. 22 89

Kinetic and molecular properties of components binding [3H]triamcinolone acetonide were studied using 105,000g supernatants of lactating mammary gland, R3230AC, and dimethylbenz[a]anthracene (DMBA) induced mammary tumors of the rat. Using a dextran-coated charcoal adsorption procedure, the relationship between specific glucocorticoid binding and protein concentration was linear in the range of 0.5-4.0 mg/reaction. These cytoplasmic macromolecules bound [3H]triamcinolone acetonide with limited capacity (50-400 fmol/mg of cytosol protein) and high affinity, Kd approximately 10(-8)-10(-9) M. Optimal binding was obtained when homogenizations were made in Tris buffers, at pH 7.4, containing monothioglycerol. Time course of association of [3H]triamcinolone acetonide and its binding sites showed maximal binding by 6-8 hr at 3 degrees which remained unchanged up to 24 hr. The rate constant of association at 3 degrees was in the range of 2-4 x 10(5) M-1 min-1. The rate constant of dissociation of bound [3H]triamcinolone acetonide could not be calculated accurately since the reaction was essentially irreversible for 5 hr at 3 degrees. Estimation of the half-life of the steroid-binding protein complexes from the Kd and the rate constant for association gave a value of 11-12 hr. From ligand specificity studies, the glucocorticoids, triamcinolone acetonide, corticosterone, cortisol, and dexamethasone competed well for [3H]triamcinolone acetonide binding sites. Progesterone, aldosterone, and the anti-glucocorticoid, cortexolone, were also good competitors while androgens and estrogens were weak inhibitors of binding. The binding compenents sedimented at 7-8 S in sucrose gradients of low ionic strength and dissociated into lower molecular weight components sedimenting at 4-5S in high ionic strength gradients. Studies in vivo using animals bearing the DMBA-induced tumor demonstrated that [3H]triamcinolone acetonide binding complexes were present in cytoplasmic and nuclear compartments. Sedimentation coefficients of the cytoplasmic and nuclear forms of these receptors labeled in vivo were 7-8S and 4-5S, respectively. These studies suggest that the molecular and kinetic binding properties of glucocorticoid receptors in neoplastic mammary tissues are similar to those of the normal mammary gland.
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PMID:Comparison of glucocorticoid-binding proteins in normal and neoplastic mammary tissues of the rat. 23 78

Benz[a]anthracene and the five metabolically possible vicinal trans dihydrodiols of benz[a]anthracene were tested for ability to initiate skin tumors in CD-1 female mice. A single topical application of 0.4-2.0 mumol of hydrocarbon was followed 18 days later by twice weekly applications of the skin promoter 12-O-tetradecanoylphorbol-13-acetate. Comparisons of latency period, percent of mice with tumors, and number of papillomas observed per mouse indicated that benz[a]anthracene 1,2-, 5,6-, 8,9-, and 10, 11-dihydrodiols were all less active tumor initiators than was benz[a]anthracene. The high tumorigenicity of benz[a]anthracene 3,4-dihydrodiol, presumably the result of metabolism to either or both of the diastereomeric benz[a]anthracene 3,4-diol-1,2-epoxides, supports the bay region theory of polycyclic hydrocarbon carcinogenicity and provides the first example of a proximate carcinogenic metabolite that is much more active than the parent hydrocarbon on mouse skin.
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PMID:Tumorigenicity of five dihydrodiols of benz(a)anthracene on mouse skin: exceptional activity of benz(a)anthracene 3,4-dihydrodiol. 26 81

ARyl hydrocarbon hydroxylase (AHH) in mouse epidermis was inducible by topical application of several tumor-initiating polycylic aromatic hydrocarbons. The weak tumor initiator 1,2,3,4-dibenazanthracene (1,2,3,4-DBA), at dose level of 200 nmoles, increased AHH activity more than 10-fold over that of the acetone controls at 12 hr after treatment. Administration of the same quantity of the potent initiator 7,12-dimethylbenz(a)anthracene (DMBA) increased AHH activity approximately 4-fold over that of the control at 12 hr after treatment. Simultaneous treatment with 200 or 100 nmoles of DMBA and 1,2,3,4-DBA resulted in AHH activity that was 546 and 732% that of the controls, respectively, 12 hr after treatment: this was less AHH activity than was observed when 1,2,3,4-DBA was administered alone. Doses of 20 nmoles or more of 1,2,3,4-DBA, when given at about the same time as DMBA, effectively inhibited DMBA initiation of skin tumors in a two stage system of tumorigenesis. The results suggest that the weak initiator 1,2,3,4-DBA may program the epidermal AHH system to metabolize the strong carcinogen DMBA to noncarcinogenic intermediate(s).
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PMID:Inhibition of the tumor-initiating ability of the potent carcinogen 7,12-dimethylbenz(a)anthracene by the weak tumor initiator 1,2,3,4-dibenzanthracene. 40 69

The increase in interfollicular epidermal ribosomes on the backs of mice initiated with 7,12-dimethylbenz(a)-anthracene and promoted with 12-0-tetradecanoyl-phorbol-13-acetate was disproportionate to the increase in epidermal wet weight, protein, and DNA. Whereas ribosome numbers increased five- to sixfold 48 hr after the first, fourth, or eight application of 12-3-tetradecanoyl-phorbol-13-acetate, epidermal tissue increased only two- to threefold at these times. This disproportionate increase was due to the fact that, concurrent with the increased amount of interfollicular epidermal tissue and cells, ribosomes per g epidermis and per mg DNA increased two to three times normal. The tissue concentration and cellular content of ribosomes were also increased in the epidermal component of induced squamous papillomas. The work of others has demonstrated that, during growth of other tissues and organs, ribosome accumulation is proportionate to accumulation of tissue and/or cells. The results of our study indicate that the epidermis may have unique kinetics of ribosome accumulation during induced growth. Furthermore, these findings suggest the interesting possibility that other tumor-prone surface epithelia, such as the linings of the respiratory and gastrointestinal tracts, have similar kinetics of ribosome accumulation during induced growth.
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PMID:Epidermal ribosome accumulation during two-stage skin tumorigenesis. 40 79

The new antiestrogen RU 16117, at doses of 8 or 24 mcg daily, had been shown to completely prevent the development of rat mammary cancer when given from the day after 7,12-dimethylbenz(a)anthracene (DMBA) administration. This study was undertaken to investigate the effect of this compound on the growth of DMBA-induced tumors which had already developed in Sprague-Dawley rats. The effect was compared with that of castration. Levels of receptors for 17beta-estradiol (E2), progesterone, and prolactin (PRL) were correlated with the response. At about 3 months after DMBA administration animals with palpable tumors were selected. The rats were then treated daily for 4 weeks with .1, .5, 2.5, or 12.5 mcg E2 or with 2, 8, or 24 mcg RU 16117 injected in .1 ml of 1% gelatin in .9% NaCl. Controls were injected with the vehicle alone. For comparison, a group of rats were ovariectomized. After 4 weeks' treatment rats were killed, blood collected, and a cytosol was prepared from tumor tissues. Binding assays and radioimmunoassays were done. 8 and 24 mcg doses of RU 16117 led to 45 and 65% inhibition of tumor number, respectively, and tumor size was markedly reduced. Lower doses had less effect. Ovariectomy had an effect similar to that of 24 mcg RU 16117. E2 doses did not change the number or size of tumors. Decreased levels of receptors for E2, progesterone, and PRL were found in the tumors remaining after ovariectomy. The 24 mcg dose of RU 16117 had a similar effect on levels of E2 and PRL receptors. It was considered likely that RU 16117 exerts its inhibitory activity at both the hypothalamic-pituitary and tumor levels.
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PMID:Potent inhibitory effect of a new antiestrogen (RU 16117) on the growth of 7,12-dimethylbenz[a]anthracene-induced rat mammary tumors. 40 79


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