Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UNIPROT:P06889 (Mol)
 630,302 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The IGFs may be important autocrine, paracrine or endocrine growth factors for human breast cancer. IGF-I and II stimulate growth of cultured human breast cancer cells. IGF-I is slightly more potent, paralleling its higher affinity for the IGF-I receptor. Antibody blockade of the IGF-I receptor inhibits growth stimulation induced by both IGFs, suggesting that this receptor mediates the growth effects of both peptides. However, IGF-I receptor blockade does not inhibit estrogen (E2)-induced growth suggesting that secreted IGFs are not the major mediators of E2 action. Several breast cancer cell lines express IGF-II mRNA by both Northern analysis and RNase protection assay. IGF-II activity is found in conditioned medium by radioimmuno and radioreceptor assay, after removal of somatomedin binding proteins (BP) which are secreted in abundance. IGF-I is undetectable. BPs of congruent to 25 and 40 K predominate in ER-negative cell lines while BPs of 36 K predominate in ER-positive cells. Blockade of the IGF-I receptor inhibits anchorage-independent and monolayer growth in serum of a panel of breast cancer cell lines. Growth of one line (MDA-231) was also inhibited in vivo by receptor antibody treatment of nude mice. The antibody had no effect on growth of MCF-7 tumors. These data suggest that IGFs are important regulators of breast cancer cell proliferation and that antagonism of this pathway may offer a new treatment strategy.
J Steroid Biochem Mol Biol 1990 Dec 20
PMID:Regulation of breast cancer growth by insulin-like growth factors. 217 63

Racemic gossypol has been shown to have antitumor properties that may be due to its ability to uncouple tumor mitochondria or to its inhibitory effects on a variety of nonmitochondrial enzymes. We have studied the antimitochondrial and enzyme-inhibiting properties of gossypol in human carcinoma cell lines of breast (MCF-7, T47-D), ovarian (OVCAR-3) colon (HCT-8), and pancreatic (MiaPaCa) origin by comparing the effects of its purified (+)- and (-)-enantiomers. (-)-Gossypol shows up to 10-fold greater antiproliferative activity than (+)-gossypol in the cancer cell lines and in normal hematopoietic stem cells grown in vitro, with IC50 values ranging from 1.5 to 4.0 microM for the cancer cells and from 10 to 20 microM for the human marrow stem cells. As well, multidrug-resistant MCF/Adr cells appear more resistant to (-)-gossypol than their parental cell line. Electron microscopy indicates that the earliest ultrastructural change in tumor cells exposed to a cytotoxic (10 microM) concentration of (-)-gossypol is the selective destruction of their mitochondria. Consistent with this observation, 31P magnetic resonance spectroscopy detects pronounced changes in tumor cell high energy phosphate metabolism within 24 hr of (-)-gossypol treatment, manifest by 1.6- to greater than 50-fold differential reductions in the intracellular ratios of ATP/Pi, relative to (+)-gossypol-treated cell lines; the magnitude of these antimitochondrial effects correlates with the antiproliferative activity of (-)-gossypol. Northern blot RNA analyses suggest that treatment with a 5-10 microM dose of (-)-gossypol induces a transient increase in the expression of heat shock gene products, particularly hsp-70 transcripts. The mean 5-fold increase in (-)-gossypol-induced hsp-70 mRNA appears coincident with a comparable heat-stimulated increase in transcript levels, as compared with control or (+)-gossypol-treated cells. The enzyme-inhibiting properties of gossypol enantiomers were compared in cell-free assays measuring glutathione-S-transferase-alpha, -mu, and pi activities, calmodulin stimulation of cyclic nucleotide phosphodiesterase, and protein kinase C activity. Both enantiomers are near equivalent antagonists of calmodulin stimulation and protein kinase C activity, exceeding the potency of known inhibitors such as phenothiazines by as much as 50-fold. In contrast, (-)-gossypol is a 3-fold more potent inhibitor of glutathione-S-transferase-alpha and -pi isozyme activity, resulting in IC50 values of 1.6 and 7.0 microM, respectively, for these two isozymes.(ABSTRACT TRUNCATED AT 400 WORDS)
Mol Pharmacol 1990 Jun
PMID:Biochemical correlates of the antitumor and antimitochondrial properties of gossypol enantiomers. 219 25

Recent evidence indicates that the polyamine pathway may play a significant role in the autocrine/paracrine control of breast cancer cell proliferation by hormones. To directly test this hypothesis, in the present experiments, we evaluated the polyamine involvement in immunoactive insulin-like growth factor I (IGF-I) secretion and IGF-I action using MCF-7 breast cancer cells cultured in serum-free medium in the presence and absence of estradiol (E2). Administration of the polyamine biosynthetic inhibitor, alpha-difluoromethylornithine (DFMO) induced a marked suppression of cellular ornithine decarboxylase (ODC) activity and polyamine levels which was associated with significant, although partial, inhibition of E2-stimulated growth. Exogenous putrescine administration repleted cellular polyamine pools and completely reversed the growth-inhibitory effect of DFMO. Despite these parallel changes in polyamine levels and proliferative activity, basal as well as E2-stimulated levels of immunoactive IGF-I measured in the conditioned media were unaffected by DFMO with and without exogenous putrescine administration. On the other hand, induction of polyamine depletion and repletion by the same treatments significantly (although partially) affected the proliferative action of exogenously added IGF-I. These findings indicate that polyamines, while not involved in immunoactive IGF-I production, play an important role, at least in part, in IGF-I action in this experimental system. Furthermore, we observed that the administration of a monoclonal antibody directed against IGF-I was able to partially block basal as well as of a monoclonal antibody directed against IGF-I was able to partially block basal as well as E2-stimulated MCF-7 cell proliferation. We conclude that immunoactive IGF-I is an important but not sole mediator of MCF-7 breast cancer growth under our experimental conditions. The polyamine pathway plays an important role in the expression of its proliferative action.
J Steroid Biochem Mol Biol 1990 Sep
PMID:Polyamine involvement in basal and estradiol-stimulated insulin-like growth factor I secretion and action in breast cancer cells in culture. 224 41

Androstenedione analogs containing 7 alpha-substituents have proven to be potent inhibitors of aromatase both in vitro and in vivo. Several of these agents have exhibited higher affinity for the enzyme complex than the substrate. In order to examine further the interaction(s) of 7-substituted steroids with aromatase, biochemical and pharmacological studies were performed on 7 alpha-thiosubstituted androstenediones and 7-substituted 4,6-androstadiene-3,17-diones. Potent inhibition of aromatase activity in human placental microsomes has been observed with several new 7 alpha-thiosubstituted androstenediones. 7-Benzyl- and 7-phenethyl-4,6-androstadiene-3,17-diones effectively inhibited microsomal aromatase, with apparent Kis ranging from 61 to 174 nM. On the other hand, 7-phenyl-4,6-androstadiene-3,17-dione exhibited poor activity, with an apparent Ki of 1.42 microM. Similar inhibitory activity was observed with reconstituted, purified cytochrome P450Arom preparations. Additionally, these agents were evaluated for inhibition of aromatase activity in two human carcinoma cell lines, the MCF-7 human mammary cancer line and the JAr choriocarcinoma line. The 7 alpha-thiosubstituted androstenediones and 7-substituted 4,6-androstadiene-3,17-diones produced dose-dependent inhibitions of aromatase activity in the cell cultures. The most effective inhibitors were the 7 alpha-substituted androstenediones, with EC50 values ranging from 7.3 to 105 nM. Finally, the JAr cell culture system exhibited prolonged inhibition of aromatase activity following exposure to 7 alpha-APTADD, suggesting enzyme inactivation by this inhibitor. Thus, these agents are effective aromatase inhibitors, and the results encourage further development of this group of medicinal agents for the treatment of estrogen-dependent mammary carcinoma.
J Steroid Biochem Mol Biol 1990 Nov 20
PMID:Biochemical and pharmacological development of steroidal inhibitors of aromatase. 225 41

17 beta-Estradiol is a potent mitogen for hormone-dependent cell lines (MCF-7, T47D and ZR 75.1). However, the degree of hormone sensitivity is very much influenced by culture conditions. In order to understand which factors modulate estrogenic effects on cell growth, four different culture conditions were used: (a) medium with dextran-coated charcoal-treated fetal calf serum (DCC-FCS); (b) medium with dextran-coated charcoal-treated growth factor-inactivated serum (DCC-FCSd); (c) serum-free medium, after a 24-h incubation with serum to allow cell attachment; and (d) serum-free medium on collagen IV-treated plates. In all cell lines the highest cell growth stimulation was achieved when estradiol was added in the presence of 5% DCC-FCS, whereas reducing or removing serum from the culture medium resulted in a decrease in cell proliferation stimulation. We postulate that serum contains some still unknown components able to modulate the degree of estrogenic action in endocrine-dependent breast cancer cell lines.
J Steroid Biochem Mol Biol 1990 Oct
PMID:Influence of culture conditions on the estrogenic cell growth stimulation of human breast cancer cells. 226 50

The use of different techniques for assay of oestrogen receptors (ER) in breast cancer raises the question of their relative effectiveness in measuring concentrations of functional receptors. Data were obtained on soluble receptors from supernatants from 58 primary breast tumour homogenates, using the ligand ([3H]oestradiol) binding assay with dextran-coated charcoal (DCC) separation, either at a single saturating ligand dose, or by Scatchard analysis, and by using the Abbott enzyme immunoassay (EIA) kit. As previous reports have shown, the two methods gave reasonably good correlation (r = 0.8), but EIA values were systematically higher than DCC (slope = 3.0). Similar values were obtained when the ER + ve/progesterone receptor (PR) + ve subgroup were examined separately (n = 34, r = 0.86, slope = 3.0). However the two sets of data were in much better agreement in the ER + ve/PR - ve subgroup (n = 10, r = 0.98, slope = 1.24). When analysed by isoelectric focusing on polyacrylamide gels (IEF), two major specific binding components were identified, at pI 6.1 and at pI 6.6. Both isoforms were present in 50/66 ER + ve PR + ve breast tumour samples, but only the pI 6.6 (4S) was present in most ER + ve/PR - ve samples (13/20). It appears that, compared with DCC, the EIA method gives much higher values for the 8S isoform, whereas the two methods detect the 4S isoform with similar sensitivity. In assays on the tumour cell lines, T47D and MCF-7, still greater discrepancies, at least 10-fold, were found between EIA and DCC data.
J Steroid Biochem Mol Biol 1990 Dec 10
PMID:Discrepancies between antibody (EIA) and saturation analysis of oestrogen receptor content in breast tumour samples. 227 49

The effects of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) on the growth of estrogen-responsive MCF-7 human breast cancer cells in the presence of 17 beta-estradiol was determined. After treatment with 17 beta-estradiol (1 nM), TCDD (10 nM) and 17 beta-estradiol (1 nM) plus TCDD (10 nM) the cells were monitored daily for cell growth and DNA content for 7 days. The results showed that TCDD inhibited cell proliferation and DNA content of untreated cells and inhibited the 17 beta-estradiol-stimulated cell proliferation and increase in cellular DNA content. In contrast, TCDD did not effect the growth of estrogen non-responsive MDA-MB-231 human breast cancer cells. TCDD (0.1-10 nM) also caused a concentration-dependent decrease in the 17 beta-estradiol-induced proliferation in MCF-7 cells. The effects of TCDD on the 17 beta-estradiol-induced secretion of the 52-kDa protein (i.e. procathepsin D), the 34-kDa (cathepsin D) and 160-kDa proteins were also determined in the MCF-7 and MDA-MB-231 human breast cancer cell lines. The levels of the proteins were determined by autoradiographic analysis of the incorporation of [35S]methionine into the secreted proteins which were separated by denaturing sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Treatment of MCF-7 cells with 17 beta-estradiol (1 nM), TCDD (10 and 100 nM) and 17 beta-estradiol (1 nM) plus TCDD (10 nM) resulted in levels of the 52-kDa protein which were 497, 63.6, 98.1 and 66.3%, respectively, of the corresponding levels observed in control (untreated) cells. Using the same concentrations, the levels of the 34-kDa protein secreted into the media were 372, 42.3, 64.0 and 43.8% of control values, respectively, and the corresponding levels of the 160-kDa protein were 381, 52.9, 71.2 and 76.6% of the control values, respectively. In contrast, treatment of MDA-MB-231 cells with 17 beta-estradiol (1 nM), TCDD (10 and 100 nM) and 17 beta-estradiol (1 nM) plus TCDD (10 nM) resulted in a 31-39% reduction in the secretion of the 52-kDa protein however these effects were not statistically different from the control values. In addition, the treatments did not cause any significant effects on the secretion of the 34- and 160-kDa proteins by MDA-MB-231 cells. These results clearly confirm and extend the range of antiestrogenic effects caused by TCDD in estrogen-responsive MCF-7 cells and indicate that the MDA-MB-231 cells are not responsive to the antiestrogenic effects of TCDD.
J Steroid Biochem Mol Biol 1990 Dec 10
PMID:Effects of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) on cell growth and the secretion of the estrogen-induced 34-, 52- and 160-kDa proteins in human breast cancer cells. 227 56

To investigate the effect of ligand (be it hormone, antihormone, or no hormone) on the interaction between estrogen receptor (ER) and chromatin, we have used formaldehyde as a cross-linking agent in intact MCF-7 human breast cancer cells. After a 1- to 2-h hormone treatment, the cells are exposed for 8 min to formaldehyde, which is added directly to their culture medium to minimize environmental perturbation. Nuclei are prepared from formaldehyde-treated cells and their contents are fractionated on CsCl density gradients to separate DNA-protein complexes from free protein. Peak gradient fractions are assayed for the presence of specific proteins by immunoblot of sodium dodecyl sulfate-polyacrylamide gel patterns. Using this approach, we find that 0.15% formaldehyde is optimal for cross-linking ER to chromatin. We detect ER and the large subunit of RNA polymerase II with DNA from formaldehyde-treated, but not from untreated cells. On the other hand, actin (a cytoplasmic protein) and small nuclear ribonucleoprotein particle proteins (nuclear RNA binding proteins) are not cross-linked to DNA. Therefore, cross-linking appears to be selective and fractionation is efficient. Interestingly, we detect similar levels of ER (as well as RNA polymerase II) with DNA from formaldehyde-treated cells, regardless of whether the cells are preexposed to estrogen (17 beta-estradiol at 10(-8) M), antiestrogen (ICI 164,384 at 10(-7) or 10(-6) M), or no hormone. These results, using covalent cross-linking in intact cells, indicate that both ligand-occupied and unoccupied ER are associated with chromatin.
Mol Endocrinol 1990 Nov
PMID:Cross-linking of estrogen receptor to chromatin in intact MCF-7 human breast cancer cells: optimization and effect of ligand. 228 Jul 70

MCF-7 human breast cancer cells were submitted to the tritiated antiestrogen tamoxifen aziridine, frozen at -170 degrees C, stored and irradiated at -78 degrees C in a calibrated Gammacell 60Co irradiator. A three-step protein extraction procedure provided protein samples for the determination of the target size (TS) of the covalently labelled estrogen receptor (ER). From the TS it is shown that ER bound to an antiestrogen was, in whole cells, part of a 265 kDa polypeptide structure if measured in MCF-7 cells at subconfluency, or of a 360 kDa species in superconfluent cells.
Mol Cell Endocrinol 1990 Aug 20
PMID:Target size analysis of estrogen receptor in cultured intact cells: change in receptor structure between subconfluency and superconfluency in culture. 228 75

Experimentally, a portion of the detectable cellular estrogen receptor (ER) is seen to disappear in human breast cancer cells submitted to estradiol treatment. In this study, we have applied several detection methods to analyze the loss (processing) then the replenishment of ER in the MCF-7 cell line. Radioligand exchange assay and enzyme immunoassay revealed an accumulation of ER in the nuclei with a concomitant depletion in cytosol shortly after the addition of estradiol in cell culture. Then, a time-dependent decrease of ER level in the nuclear compartment without rescue in the cytosol was observed. When an immunocytochemical assay was performed on whole cells treated with estradiol, a similar decrease of ER number was shown, indicating that a decrease in the extractability of estradiol-filled ER was not involved in the processing. Analysis of ER mRNA also indicated that the estrogen treatment induces a time-dependent decrease of its expression. Measurement of [35S]methionine-labeled ER following the arrest of the hormone treatment suggested that ER replenishment was due to newly synthesized receptors. Sucrose gradient experiments confirmed the generation of small molecular forms of ER, following its binding with estradiol. All these data are indicative of estrogen-receptor complex degradation. We also confirm that estrogen regulates ER level through the decrease of its mRNA expression.
Mol Cell Endocrinol 1990 Nov 12
PMID:Expression of estrogen receptor and its messenger ribonucleic acid in the MCF-7 cell line: multiparametric analysis of its processing and regulation by estrogen. 228 76


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>