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Query: UNIPROT:P06889 (Mol)
 630,302 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Transforming growth factor-beta (TGF beta) is a potent growth inhibitor in most epithelial cells. We evaluated the effects of norethindrone (which in combination with estrogen is commonly used in oral contraceptives) and other progestins [medioxyprogesterone acetate (MPA) and R5020, which are not used in oral contraceptives] on cell growth and the expression of TGF beta 1, TGF beta 2, and TGF beta 3 mRNAs in MCF-7 human breast cancer cells. Growth of MCF-7 cells was stimulated by norethindrone (10(-8)-10(-5) M), with maximal growth stimulation at 10(-7) M norethindrone after 7 days of treatment. However, the growth of MCF-7 cells was not affected by MPA (10(-8) M) or R5020 (10(-8) M). Treatment with the antiestrogen 4-hydroxytamoxifen at a concentration of 10(-7) M blocked the growth stimulation induced by norethindrone. The norethindrone-induced growth stimulation was accompanied by a dramatic decrease in TGF beta 2 and TGF beta 3 mRNA levels, whereas the level of TGF beta 1 mRNA was not affected by any of the compounds tested. In addition, treatment with MPA or R5020 did not affect TGF beta 2 and TGF beta 3 mRNA levels. The inhibitory effect of norethindrone on TGF beta 2 and TGF beta 3 mRNA levels could be blocked by the addition of 10(-7) M 4-hydroxytamoxifen. Norethindrone as well as estradiol decreased estrogen receptor mRNA levels and increased progesterone receptor mRNA levels. This is the first report which demonstrates that norethindrone stimulates estrogen-responsive human breast cancer cell growth and inhibits the expression of TGF beta 2 and TGF beta 3 mRNAs. These results suggest that the differential regulation of TGF beta expression by norethindrone may be at least partly responsible for the growth stimulation induced by norethindrone. Thus, the norethindrone component of some oral contraceptives may be sufficiently estrogenic to facilitate the development of breast cancer.
Mol Endocrinol 1991 Aug
PMID:Growth stimulation and differential regulation of transforming growth factor-beta 1 (TGF beta 1), TGF beta 2, and TGF beta 3 messenger RNA levels by norethindrone in MCF-7 human breast cancer cells. 183 33

Phosphorylation of ribosomal protein S6 of mammals precedes activation of cell growth in numerous biological systems. We have cloned a cDNA for ribosomal protein S6 from T-47D human breast cancer cells by immunoscreening a lambda gt11 expression library with antibody raised against the mitochondrial Ca(2+)-binding ATPase inhibitor protein (CaBI) of bovine heart mitochondria (Yamada & Huzel: J Biol Chem 263: 11498-11503, 1988). Similar clones were obtained by the immunoscreening of a rat heart expression library. In agreement with others, the open reading frames of the cDNAs from the two species coded for the same amino acid sequence. No difference in S6 of the human neoplastic cells compared to that of non-neoplastic cells was found. However, common antigenic determinants in S6 and CaBI were indicated. Accordingly, S6 was purified from rat liver ribosomes and antiserum prepared. Immuno-dot blot and Western blot analyses showed high specific reactivity between S6, the cloned chimeric beta-galactosidase fusion protein from a cDNA clone, and CaBI with anti-S6 and anti-CaBI antibodies. The antibodies also showed a high degree of discrimination for S6 and CaBI. Neither interacted with the other ribosomal proteins nor with another ATPase inhibitor protein from bovine heart mitochondria. Neither interacted with the Ca(2+)-binding proteins, calmodulin, oncomodulin, Protein C, or Factor X. Prothrombin was weakly reactive with anti-CaBI but not with anti-S6. Thus, the results fulfill the specific criteria for the concept and operational definition of common protein epitopes in S6 and CaBI. However, neither prothrombin nor S6 fusion protein inhibited mitochondrial ATPase activity even at 20 times the concentrations at which CaBI gave 97% inhibition.
Mol Cell Biochem 1991 Nov 13
PMID:Antigenic reactivity of ribosomal protein S6 and the calcium-binding ATPase inhibitor protein of mammalian mitochondria. 183 89

The binding affinity and relative estrogenic potency of 2-bromo-, 4-bromo-, 2-methyl- and 4-methylestradiol was evaluated in MCF-7 breast cancer cells. The relative binding affinities compared to estradiol were 47% for 2-methyl-, 25% for 4-methyl-, 37% for 4-bromo- and 17% for 2-bromoestradiol. However, both 2- and 4-methyl- as well as 2- and 4-bromoestradiol were able (a) to translocate the cytosolic estrogen receptor into the nucleus and (b) to induce the progesterone receptor in a concentration dependent manner. Finally, all ring-A substituted estrogens used in this study induced the pS2 mRNA as demonstrated by Northern-blotting. From these findings we conclude that 2-bromo-, 4-bromo-, 2-methyl- and 4-methylestradiol are agonistic ligands for the estrogen receptor in MCF-7 breast cancer cells.
J Steroid Biochem Mol Biol 1991 Sep
PMID:Methyl and bromo derivatives of estradiol are agonistic ligands for the estrogen receptor of MCF-7 breast cancer cells. 191 26

Estrone sulfatase is an important mechanism of local synthesis of biologically active estrogens in human breast cancer. The human placental microsome and breast carcinoma mitochondrial/microsomal estrone sulfatase activity were characterized and inhibition studies performed. The Km of the placental tissue enzyme was 6.83 microM, Vmax 0.015 nmol/min/mg, and for the breast carcinoma tissue Km was 8.91 microM and Vmax 0.022 nmol/min/mg. Danazol produced a significant inhibition of estrone sulfatase (20% with 50 microM danazol). No significant inhibition was seen in the presence of aminoglutethimide, rogletimide, tamoxifen, 4-hydroxyandrostenedione, stilboestrol, or any metabolites of danazol or tamoxifen. Studies with synthetic and naturally occurring steroids demonstrated that the presence of a sulfate group at the 3 position to be the most important factor in determining inhibition, and the most potent inhibitor was 5 alpha-androstene-3 beta,17 beta-diol-3-sulfate (Ki of 2.0 microM). The naturally occurring 3-sulfated steroids all demonstrated competitive inhibition. These studies could form the basis for the design of a potent estrone sulfatase inhibitor which would have potential therapeutic activity in the management of breast cancer.
J Steroid Biochem Mol Biol 1991 Oct
PMID:Inhibition of estrone sulfatase enzyme in human placenta and human breast carcinoma. 191 38

From 1984 to 1990, human breast cancer estrogen receptors have been measured both by a radioligand assay (RLA[3H]estradiol) and by an enzyme immunoassay (Abbott ER-EIA kit). The ratio EIA/RLA results increased continuously from 1.04 (1984) to 1.87 (1990), and this evolution was consistent with the last trial of the E.O.R.T.C. receptor study group (Trial 1989-II, EIA/RLA = 2.5). Dilution studies of cytosols with the current ER-EIA kits showed an important parallelism defect of the standard curve, the final result of cytosols (fmol/mg protein) obtained from the upper part of the curve (between 100 and 500 fmol/ml) being 1.5 to 2 times higher than the results obtained from readings of the lower part of the standard curve (between 0 and 50 fmol/ml). Chromatographic experiments were carried out during 1986 and the measures of binding sites by RLA and of immunoreactive sites by EIA on chromatographic fractions were compared. Identical results were obtained with EIA and RLA, either on polymeric forms of the estrogen receptor, or on monomeric forms obtained after dissociation by 0.4 M KCl. The same experiments performed during 1990 showed that, in the chromatographic fractions, the concentration of immunoreactive sites was twice as large as that of ligand-binding sites, detected by tritiated estradiol. Furthermore, the detection of polymeric and monomeric receptor isoforms by monoclonal antibodies varied, and was increased by the presence of KCl (0.4 M) and/or bovine serum albumin (BSA) (1 mg/ml) in the cytosol. These findings showed that the large differences between enzyme immunoassay and ligand-binding assay results currently observed were due to differential reactivity of monoclonal antibodies for the estrogen receptor standard provided in the ER-EIA kits and for the estrogen receptor present in cytosols from human breast cancers, suggesting modifications of immunoreactivity of the monoclonal antibodies actually provided in the ER-EIA kits.
J Steroid Biochem Mol Biol 1991 Oct
PMID:Evolution of immunoreactivity of monoclonal antibodies H222 and/or D547 used in the detection of breast cancer estrogen receptors. Varying reactivity of receptor isoforms. 191 41

Human breast cancer cells are used extensively for the study of steroid hormone action. It is known that in both receptor positive and receptor negative cell lines there is considerable metabolism of the natural estrogens, estradiol (E2) and estrone (E1) with interconversion of the two steroids and formation of sulphate and glucuronide conjugates. The aim of the present work was to see if the commonly used oral contraceptive steroids (OCS) ethynylestradiol (EE2) and norgestimate (Ngmate) were metabolized in human breast cancer cell lines (MCF-7 and ZR-75-1) and a normal breast cell line (Huma 7). MCF-7, ZR-75-1 and Huma 7 cells were maintained in Dulbeccos Modified Eagles Medium (DMEM) containing foetal calf serum (FCS) insulin and hydrocortisone. In addition, ZR-75-1 cells required epidermal growth factor (EGF) and E2 while MCF-7 cells required only EGF. On reaching confluence cells were transferred to DMEM containing charcoal-stripped FCS, insulin and hydrocortisone. 48 h later this medium was renewed, radiolabelled steroid ([3H]E1; [3H]E2; [3H]EE2, [3H]Ngmate; [3H]E1-SO4; 1 nM; 0.2 microCi) was added and incubation was for 24 or 48 h. Following incubation, the medium was removed and radioactive steroid extracted with ether. Metabolites were analysed by on-line radiometric HPLC. All the cell lines were able to interconvert E1 and E2; the equilibrium favouring the formation of E2 in MCF-7 and ZR-75-1 and E1 in Huma 7 cells. E1 and E2 also underwent phase II metabolism to form their respective estrogen sulphates, this activity being most marked in the Huma 7 cell line. In addition to sulphotransferase activity, the study with E1 sulphate demonstrated sulphatase activity in both normal and cancer cells. There appeared to be no difference in extent of hydrolysis, with both E1 and E2 formed. With EE2 as substrate there was no evidence of phase I metabolism in any of the cell lines but there was conversion to the presumed 3-sulphate conjugate. The percentage formation of this metabolite was very much greater in Human 7 cells (64.1 +/- 9.6% after 24 h) than in MCF-7 and ZR-75-1 cells (7.4 +/- 5.3% and 10.6 +/- 4.1%, respectively after 24 h). In all the cell lines deacetylation of the progestogen Ngmate to norgestrel oxime was complete within 24 h. In addition there was evidence of loss of the oxime moiety to give norgestrel.(ABSTRACT TRUNCATED AT 400 WORDS)
J Steroid Biochem Mol Biol 1991 Oct
PMID:Metabolism of the oral contraceptive steroids ethynylestradiol and norgestimate by normal (Huma 7) and malignant (MCF-7 and ZR-75-1) human breast cells in culture. 191 42

This study documents a biphasic change in the rate of cell cycle progression and proliferation of T-47D human breast cancer cells treated with synthetic progestins, consisting of an initial transient acceleration in transit through G1, followed by cell cycle arrest and growth inhibition. Both components of the response were mediated via the progesterone receptor. The data are consistent with a model in which the action of progestins is to accelerate cells already progressing through G1, which are then arrested early in G1 after completing a round of replication, as are cells initially in other phases of the cell cycle. Such acceleration implies that progestins act on genes or gene products which are rate limiting for cell cycle progression. Increased production of epidermal growth factor and transforming growth factor alpha, putative autocrine growth factors in breast cancer cells, does not appear to account for the initial response to progestins, since although the mRNA abundance for these growth factors is rapidly induced by progestins, cells treated with epidermal growth factor or transforming growth factor alpha did not enter S phase until 5 to 6 h later than those stimulated by progestin. The proto-oncogenes c-fos and c-myc were rapidly but transiently induced by progestin treatment, paralleling the well-known response of these genes to mitogenic signals in other cell types. The progestin antagonist RU 486 inhibited progestin regulation of both cell cycle progression and c-myc expression, suggesting that this proto-oncogene may participate in growth modulation by progestins.
Mol Cell Biol 1991 Oct
PMID:Progestins both stimulate and inhibit breast cancer cell cycle progression while increasing expression of transforming growth factor alpha, epidermal growth factor receptor, c-fos, and c-myc genes. 192 31

Oestradiol-17 beta and tamoxifen regulate the synthesis of a gross cystic disease fluid protein (GCDFP-15) in T47D human breast cancer cells. Dose-response curves of GCDFP-15 mRNA contents and GCDFP-15 levels in culture media and cells versus hormone or antihormone concentration have been established. Production of GCDFP-15 was increased by oestradiol-17 beta, tamoxifen and 4-OH tamoxifen. The effect of tamoxifen and 4-OH tamoxifen was greater than the effect of oestradiol-17 beta. Moreover, oestradiol-17 beta and 4-OH tamoxifen acted synergystically in enhancing GCDFP-15 release. The strong oestrogenic effect of the antioestrogen tamoxifen in regulating GCDFP-15 may reflect an unusual interaction between the tamoxifen-oestrogen receptor complex and the DNA oestrogen-responsive elements. As oestrogen control of GCDFP-15 depends also on the cell line studied, investigation of GCDFP-15 could extend our knowledge of the possible mechanism of action of oestrogens or antioestrogens.
J Mol Endocrinol 1991 Oct
PMID:Stimulatory effect of oestradiol-17 beta and tamoxifen on gross cystic disease fluid protein 15,000 production and mRNA levels in T47D human breast cancer cells. 193 Jun 24

The antirheumatic gold salt aurothiomalate (AuTM) has cellular actions that are consistent with modulation of gene expression. We have tested the hypothesis that an important mode of action of AuTM is inhibition of binding of certain transcription factors to regulatory elements in DNA. The chemistry of transcription factors containing the zinc finger motif makes them candidates for such an interaction with AuTM. In this regard, the interaction of a steroid hormone receptor, the progesterone receptor (PR), with its DNA response element (PRE) was chosen as a suitable model. Nuclear extracts of T-47D human breast cancer cells rich in PR were incubated with radiolabeled PRE, and binding was determined by gel retardation assay. Preincubation of nuclear extract with AuTM caused a concentration-dependent inhibition of binding of PR to PRE (IC50, approximately 3 microM). Other metal ions inhibited binding at higher concentrations, in a rank order correlating with their binding affinity for thiols. Thiomalic acid had no effect in the absence of gold in this system. To test the effect of AuTM on PR-mediated transcription, we transfected the progestin-inducible expression vector pMSG-CAT into T-47D cells. Transfected cells were incubated in the absence or presence of AuTM and treated with the synthetic progestin ORG2058, to induce chloramphenicol acetyl transferase (CAT) activity. With 10 and 100 microM AuTM, there was inhibition to 67 +/- 3% (p = 0.012) and 42 +/- 8% (p = 0.008) of CAT specific activity, respectively, compared with controls. These results demonstrate that AuTM can regulate gene expression and that inhibition of binding of a transcription factor to its response element is a likely mechanism. This provides a molecular model for further study of the antirheumatic action of gold salts.
Mol Pharmacol 1991 Nov
PMID:Inhibition of DNA binding and transcriptional activity of a nuclear receptor transcription factor by aurothiomalate and other metal ions. 194 34

Aromatase activity may be detected both in breast adipose tissue and breast cancer in levels similar to or greater than those in other peripheral tissues. Factors influencing such local biosynthesis have been sought. Of 247 primary breast cancers investigated, 178 showed evidence of oestrogen biosynthesis. No significant relationships were found between either the presence or levels of activity and tumour histopathology, patient characteristics (such as age and menopausal status), disease stage and prognosis (determined by disease-free interval and survival after primary treatment). Aromatase was more likely to be found in cellular cancers and those which were oestrogen receptor-positive, but these were not absolute associations, activity being detected in tumours with all degrees of cellularity and both receptor-positive and receptor-negative cancers. However, in a small group of patients with metastatic oestrogen receptor-positive tumours, response to the aromatase inhibitor, aminoglutethimide, seemed confined to tumours with aromatase activity. Oestrogen biosynthesis was detected in all specimens of breast adipose tissue examined. Activities were higher in fat from breast cancer patients compared with that from women with benign breast disease. In breasts with cancer, levels were higher in quadrants bearing tumour compared with those without evidence of malignancy. It is suggested that either enhanced aromatase in breast fat promotes the appearance of overt cancer or tumour factors induce aromatase in surrounding fat. Finally, although no significant correlations were detected in postmenopausal women between local aromatase activity and endogenous oestrogens in breast cancer, perfusion studies show that in situ oestrogen biosynthesis is primarily responsible for oestrogen levels in the majority of breast tissues. These data suggest that local aromatase activity may influence events within the breast and may be associated with the natural history and progression of certain malignancies.
J Steroid Biochem Mol Biol 1991 Nov
PMID:Aromatase activity in breast tissue. 195 67


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