UNIPROT:P04155 - FACTA Search

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Query: UNIPROT:P04155 (pS2)
1,234 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We have conducted a clinical trial of a novel pure antiestrogen, 7 alpha-[9-(4,4,5,5,5-pentafluoropentylsulfinyl)nonyl]estra-1,3,5,(1 0)-triene-3,17 beta-diol (ICI 182780), to assess its tolerance, pharmacokinetics, and short term biological effects in women with primary breast cancer. Fifty-six patients were randomized to either a control group (n = 19), in which they received no preoperative treatment, or a treatment group (n = 37), in which they received daily i.m. injections of ICI 182780 at doses of 6 mg (n = 21) or 18 mg (n = 16) for 7 days prior to primary breast surgery. Serum drug concentrations, gonadotropin levels, and sex hormone-binding globulin levels were measured during the study period by radioimmunoassay. Expression of estrogen receptors (ER), progesterone receptors, the estrogen-induced protein pS2, and the cell proliferation-related antigen Ki67 was determined immunocytochemically in pre- and poststudy tumor samples. Treatment with ICI 182780 caused no serious drug-related adverse events and had no effect on serum gonadotropin or sex hormone-binding globulin levels. Minor adverse events occurred in 5 patients receiving the 6-mg dose and 3 patients receiving the 18-mg dose. The serum concentration of ICI 182780 was dose dependent but showed variation between individuals. There was evidence of an approximately 3-fold drug accumulation over the short treatment period but steady state levels were not reached by the end of the 7 days. In patients with ER-positive tumors, treatment with ICI 182780 was associated with significant reductions in the tumor expression of ER (median ER index, 0.72 before versus 0.02 after treatment; P < 0.001), progesterone receptor (median progesterone receptor index, 0.50 before versus 0.01 after treatment; P < 0.05), and Ki67 (median Ki67 labeling index, 3.2 before versus 1.1 after treatment; P < 0.05). Treatment with ICI 182780 also resulted in a significant reduction in pS2 expression (P < 0.05) but this appeared unrelated to tumor ER status. In conclusion, ICI 182780 was well tolerated after short term administration and produced demonstrable antiestrogenic effects in human breast tumors in vivo, without showing evidence of agonist activity. These properties identify ICI 182780 as a candidate agent with which to evaluate whether a pure estrogen antagonist offers any additional benefit in the treatment of human breast cancer over conventional nonsteroidal antiestrogens, typified by tamoxifen, which exhibit variable degrees of agonist activity.
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PMID:Investigation of a new pure antiestrogen (ICI 182780) in women with primary breast cancer. 827 77

The effects of the anti-estrogens 4-hydroxytamoxifen (OHTam), ICI 164,384 and ICI 182,780 were tested on the MCF-7/LCC2 breast-carcinoma cell line, which grows significantly in the presence of OHTam and serves as a model for studying anti-estrogen resistance of estrogen-receptor-positive breast cancer. Cell proliferation and cathepsin-D secretion were strongly inhibited by either ICI 182,780 or ICI 164,384 alone or ICI 164,384 in combination with 17-beta-estradiol (E2) or OHTam. ICI 164,384 alone did not affect the cathepsin-D and pS2 mRNA levels, but antagonized the stimulatory effects of E2 or OHTam on these 2 mRNAs. OHTam was more effective than E2 in increasing cathepsin-D mRNA levels, supporting the idea that anti-estrogen-resistant breast cancer continues to overexpress cathepsin-D. These data show that the steroidal anti-estrogens ICI 164,384 and ICI 182,780 retain their ability to inhibit cell proliferation and the estrogen-responsiveness of cathepsin-D and pS2 genes in the OHTam-resistant MCF-7/LCC2 cell lines. These pure anti-estrogens may thus be efficient second-line treatments of some Tamoxifen-resistant tumors.
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PMID:Anti-proliferative and anti-estrogenic effects of ICI 164,384 and ICI 182,780 in 4-OH-tamoxifen-resistant human breast-cancer cells. 831 14

In MCF7 human breast cancer cells, the antiestrogens 4-hydroxy-tamoxifen and ICI 164,384 inhibit the mitogenic activity of epidermal growth factor (EGF) and insulin-like growth factor-I (IGF-I). These growth factors also stimulate the expression of cathepsin-D and pS2 genes. Therefore, we studied the effects of antiestrogens on growth factor induction of pS2 and cathepsin-D mRNA. The two antiestrogens strongly inhibited the transcriptional induction of pS2 by growth factors. On the contrary, estradiol and IGF-I or EGF had an additive effect on pS2 mRNA accumulation. Growth factor induction of cathepsin-D was also inhibited by ICI 164,384. By contrast, 4-hydroxytamoxifen had an agonist effect on cathepsin-D and an additive effect on IGF-I-induced mRNA. When 12-O-tetradecanoylphorbol-13-acetate or 8-bromo-cAMP (8-Br-cAMP) was used instead of growth factors, similar effects of 4-hydroxytamoxifen and ICI 164,384 were obtained on pS2 (12-O-tetradecanoylphorbol-13-acetate and 8-Br-cAMP) and cathepsin-D (8-Br-cAMP) induction. A mechanism based on the classical competitive inhibition by antiestrogens of estrogen binding and action on the estrogen receptor was very unlikely, as 1) no antigrowth factor activity was obtained with R5020, which was a potent inhibitor of estrogen induction of pS2 and cathepsin-D mRNA; 2) in the Ishikawa endometrial cancer cell line, the cathepsin-D gene is unresponsive to estrogen, but was inhibited by antiestrogen after its induction by EGF or 8-Br-cAMP; and 3) the residual estrogen concentration in cells was too low to induce the expression of estrogen-specific genes. However, antiestrogens did not inhibit the expression of all genes induced by growth factors, as they were without effect on IGF-I induction of glyceraldehyde-3-phosphate dehydrogenase mRNA. These results demonstrate that antiestrogens can modulate the transcription of some growth factor-induced genes and strongly suggest that this effect is not due to interference with residual estrogens.
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PMID:Synthetic antiestrogens modulate induction of pS2 and cathepsin-D messenger ribonucleic acid by growth factors and adenosine 3',5'-monophosphate in MCF7 cells. 834 99

The estrogen receptor gene gives rise to variant mRNAs, generated by alternative mRNA splicing, as well as the full-length mRNA containing eight coding exons. It has been postulated that one of these, the exon 5 variant, may be important in the development of hormone-independent and anti-estrogen-resistant breast cancer since it has the potential to encode a truncated receptor that retains the N-terminal activation domain AF-1, but lacks the hormone-binding domain. We have expressed the variant using an inducible promoter in estrogen receptor-positive MCF-7 cells and analyzed the effect of the variant protein on gene expression and cell growth. Inducible expression was validated using a specific antiserum that recognized a novel epitope on the exon 5 variant. The variant was able to stimulate transcription of a reporter gene in transiently transfected chicken embryo fibroblasts in the absence of hormone but showed weak constitutive activity when it was stably expressed in MCF-7 cells. The variant had no effect on the expression of the estrogen target genes, pS2, and the progesterone receptor. Finally, we analyzed whether the proliferation of MCF-7 cells was altered by the expression of the exon 5 variant and found that the stimulatory effects of estrogen and growth inhibitory effects of tamoxifen and ICI 182780 were unchanged. We therefore conclude that expression of the variant alone is not sufficient to give rise to hormone independence or tamoxifen resistance of breast cancers.
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PMID:Effects of an exon 5 variant of the estrogen receptor in MCF-7 breast cancer cells. 860 2

Tamoxifen, although widely used in the treatment of estrogen-dependent tumors, is a partial estrogen agonist producing undesirable effects in breast cancer patients. ICI 182,780 a steroidal antiestrogen displays pure antagonist activity which is due to its ability to prevent dimerization of the estrogen receptor (ER). Our previous studies have shown that 1,1-dichloro-cis-2,3-diaryl cyclopropane (Analog II), a diarylcyclopropyl compound is devoid of estrogenic activity, has a weak binding affinity for the estrogen receptor in the mouse uterine tissue and inhibits the growth of breast cancer cells in culture. These findings suggest that Analog II may not inhibit tumor cell growth at the cellular level by an ER-mediated mechanism of action. Since these three antiestrogens appear to have different mechanisms of antiestrogenic activity, the purpose of this study was to compare the influence of the three antiestrogens on estradiol-induced expression of pS2 and cathepsin D (cath-D). These genes are known to be primarily under the influence of estrogen in ER positive MCF-7 human breast cancer cells. The results of this study demonstrate different mechanisms of regulation of the cath-D and pS2 genes by antiestrogens in MCF-7 cells. This study indicates that ICI 182,780 is a pure antagonist at the levels of gene regulation and cell proliferation. The relative order of inhibitory action was found to be ICI 182,780 > tamoxifen > Analog II.
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PMID:The influence of antiestrogens on pS2 and cathepsin D mRNA induction in MCF-7 breast cancer cells. 868 38

To understand better the antiestrogen-resistant phenotype that frequently develops in breast cancer patients receiving tamoxifen, we cultured MCF-7 breast cancer cells long-term (>1 yr) in the presence of the antiestrogen trans-hydroxytamoxifen (TOT) to generate a subline refractory to the growth-suppressive effects of TOT. This subline (designated MCF/TOT) showed growth stimulation, rather than inhibition, with TOT and diminished growth stimulation with estradiol (E2), yet remained as sensitive as the parental cells to growth suppression by another antiestrogen, ICI 164,384. Estrogen receptor (ER) levels were maintained at 40% of that in parent MCF-7 cells, but MCF/TOT cells failed to show an increase in progesterone receptor content in response to E2 or TOT treatment. In contrast, the MCF/TOT subline behaved like parental cells in terms of E2 and TOT regulation of ER and pS2 expression and transactivation of a transiently transfected estrogen-responsive gene construct. DNA sequencing of the hormone binding domain of the ER from both MCF-7 and MCF/TOT cells confirmed the presence of wild-type ER and exon 5 and exon 7 deletion splice variants, but showed no point mutations. Compared to the parental cells, the MCF/TOT subline showed reduced sensitivity to the growth-suppressive effects of retinoic acid and complete resistance to exogenous TGF-beta1. The altered growth responsiveness of MCF/TOT cells to TOT and TGF-beta1 was partly to fully reversible following TOT withdrawal for 16 weeks. Our findings underscore the fact that antiestrogen resistance is response-specific; that loss of growth suppression by TOT appears to be due to the acquisition of weak growth stimulation; and that resistance to TOT does not mean global resistance to other more pure antiestrogens such as ICI 164,384, implying that these antiestrogens must act by somewhat different mechanisms. The association of reduced retinoic acid responsiveness and insensitivity to exogenous TGF-beta with antiestrogen growth resistance in these cells supports the increasing evidence for interrelationships among cell regulatory pathways utilized by these three growth-suppressive agents in breast cancer cells. In addition, our findings indicate that one mechanism of antiestrogen resistance, as seen in MCF/TOT cells, may involve alterations in growth factor and other hormonal pathways that affect the ER response pathway.
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PMID:Response-specific antiestrogen resistance in a newly characterized MCF-7 human breast cancer cell line resulting from long-term exposure to trans-hydroxytamoxifen. 901 Mar 27

The mRNA levels of LIV-1 and pS2, two estrogen-responsive genes, are increased by the agents, cholera toxin (CT) plus 3-isobutyl-l-methylxanthine (IBMX), which cause an increase in cAMP in MCF-7 human breast cancer cells. The simultaneous addition of estradiol and CT/IBMX results in a synergistic induction of the two mRNAs. The changes in mRNA reflect changes in transcription of the two genes. Interestingly, the addition of CT/IBMX to estradiol not only causes a greater increase in transcription rate but the increase is longer-lasting that seen with the hormone alone. Stimulation of mRNA levels by CT/IBMX, but not by estradiol, was prevented by cycloheximide. Stimulation by both estradiol and by CT/IBMX was prevented by the antiestrogen, ICI 164387. Transcription of LIV-1 and pS2 genes is by both estradiol and cAMP, via separate mechanisms both requiring the estrogen receptor.
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PMID:Interaction between estradiol and cAMP in the regulation of specific gene expression. 902 26

To elucidate the mechanisms responsible for the development of anti-estrogen resistance, we have cloned and established 3 stable ICI-182,780-resistant sub-lines, MCF-7/182R-1, MCF-7/182R-6 and MCF-7/182R-7 from the estrogen-receptor(ER)-positive and estrogen-responsive human breast-cancer MCF-7 cell line by long-term treatment with 10(-7) M ICI 182,780. The ICI-182,780-resistant MCF-7 sub-lines express ER, but compared with MCF-7 cells the level is significantly lower in all 3 sub-lines. In the MCF-7 cell line we find that ER expression is regulated by estrogen and anti-estrogens at the transcriptional and post-transcriptional level. This is in contrast to the ICI-182,780-resistant sub-lines, in which we find very little hormonal effects on the ER mRNA expression level. The resistant sub-lines also deviate from parent characteristics by the complete lack of expression of progesterone receptor even when grown in the presence of estradiol. All 3 resistant sub-lines have a lower basal expression of cathepsin-D mRNA comparable with the lower ER expression, but, in contrast, they have higher basal expression of the pS2 mRNA than the parent MCF-7 cell line. Although there are different basal expression levels of the pS2 and cathepsin-D genes, the resistant sub-lines behave like the parent MCF-7 cell line with respect to the hormonal regulation of both genes. The estrogen receptors in the resistant sub-lines have also maintained wild-type characteristics with respect to estrogen and anti-estrogen regulation of the estrogen-regulated proteins procathepsin D, alpha1-antitrypsin and a 42-kDa protein. The resistant cells require estrogen for growth in athymic nude mice. Our results clearly demonstrate that the ER in the resistant sub-lines have a normal function for most parameters investigated, supporting our earlier observation that only wild-type ER protein is expressed in these cells. The few observed differences in ER function between the parent MCF-7 cell line and the resistant sub-lines are not likely to be responsible for the ICI-182,780-resistant phenotype.
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PMID:Resistance of human breast-cancer cells to the pure steroidal anti-estrogen ICI 182,780 is not associated with a general loss of estrogen-receptor expression or lack of estrogen responsiveness. 937 50

It has recently been suggested that mutation of a conserved tyrosine to asparagine within the ligand-binding domain of the estrogen receptor (ER) alpha confers hormone-independent activation and insensitivity to antiestrogens (Q. X. Zhang et al., Cancer Res., 57: 1244-1249, 1997). In view of the recent discovery of ERbeta and the development of the novel nonsteroidal antiestrogen EM-800 and its active metabolite EM-652, we decided to reexamine this issue by introducing a series of mutations at the conserved tyrosine 537 in ERalpha and 443 in ERbeta and measuring their transcriptional activity in the absence and presence of estradiol and the antiestrogens EM-652, ICI 182,780, and 4-hydroxytamoxifen. As demonstrated previously for ERalpha, we observed that substituting a serine or asparagine but not a phenylalanine for the conserved tyrosine 443 in ERbeta confers constitutive transcriptional activity to the receptor. This activity was apparent on both the vitA2-ERE and the pS2 promoters in Cos-1 and HeLa cell lines as well as the human breast cancer cell line MDA-MB-231. However, the ligand-independent transcriptional activity of all ERalpha and ERbeta mutants examined, including the tyrosine to asparagine substitutions, was completely abolished by the three antiestrogens tested in this system. Furthermore, hormone-independent interaction of ERalpha and ERbeta mutant receptors with the steroid receptor coactivator-1 was abrogated by these antiestrogens. Our report, therefore, indicates that antiestrogens would be effective agents against constitutively active tyrosine ERalpha and ERbeta mutants and suggests that this particular type of modified receptors are unlikely to contribute to resistance toward antiestrogens in breast cancer therapy.
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PMID:Ligand-independent activation of the estrogen receptors alpha and beta by mutations of a conserved tyrosine can be abolished by antiestrogens. 950 Apr 42

Alterations in the expression of the breast and ovarian cancer susceptibility gene BRCA1 may contribute to the development of mammary and ovarian neoplasia. The sex-steroid estrogen modulates cell proliferation of normal and neoplastic breast and ovarian epithelial cells, but the role of estrogen regulation on the expression of BRCA1 remains to be defined. In this study, estrogen-regulated BRCA1 expression was examined in breast and ovarian cancer cells. Estrogen stimulated the proliferation of estrogen receptor (ER)-positive breast MCF-7, C7-MCF-7, and ovarian BG-1 cells as well as the expression of the estrogen-inducible pS2 gene. This was concomitant with upregulation of BRCA1 mRNA (2.5- to 5.0-fold) and a 3- to 10-fold induction of BRCA1 protein (230 kDa). Cell fractionation studies localized the BRCA1 protein to the nucleus in both unstimulated and estrogen-stimulated cells. The antiestrogen ICI-182780 inhibited estrogen-induced cell proliferation, BRCA1 mRNA induction, and BRCA1 protein expression in ER-positive cells. Conversely, estrogen did not influence expression of BRCA1 in HBL-100 cells that lacked the estrogen receptor, although the constitutive levels of BRCA1 mRNA (but not protein) in these cells were 5- to 30-fold higher than in other breast and ovarian cancer cells. Secretion of the BRCA1 protein into the cell medium did not account for the discrepancy between the mRNA and protein levels in HBL-100 cells. Proliferation of HBL-100 cells was not affected by either estrogen or ICI-182780. Taken together, these data support a role for the steroid estrogen and the involvement of the estrogen receptor pathway in the modulation of expression of BRCA1. We therefore propose that stimulation of cell proliferation may be a prerequisite for upregulation of BRCA1 in breast and ovarian cancer cells.
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PMID:Estrogen upregulation of BRCA1 expression with no effect on localization. 965 54

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