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Biochemical and Biophysical Research... Aug 1997Ligand-dependent chimeric Cre recombinases are powerful tools to induce specific DNA rearrangements in cultured cells and in mice. We report here the construction and...
Ligand-dependent chimeric Cre recombinases are powerful tools to induce specific DNA rearrangements in cultured cells and in mice. We report here the construction and characterization of a series of chimeric recombinases, each consisting of Cre fused to a mutated human oestrogen receptor (ER) ligand-binding domain (LBD). Two new ligand-dependent recombinases which contain either the G400V/M543A/L544A or the G400V/L539A/L540A triple mutation of the human ER LBD are efficiently induced by the synthetic ER antagonists 4-hydroxytamoxifen (OHT) and ICI 182,780 (ICI), respectively, but are insensitive to 17 beta-oestradiol (E2). Both chimeric recombinases should be useful for efficient spatio-temporally controlled site-directed somatic mutagenesis.
Topics: Amino Acid Sequence; Animals; Base Sequence; Binding Sites; Enzyme Induction; Estradiol; Estrogen Antagonists; Fulvestrant; Humans; Integrases; Kinetics; Mice; Molecular Sequence Data; Mutagenesis, Insertional; Mutagenesis, Site-Directed; Oligodeoxyribonucleotides; Point Mutation; Receptors, Estrogen; Recombinant Fusion Proteins; Tamoxifen; Teratoma; Tumor Cells, Cultured; Viral Proteins
PubMed: 9299439
DOI: 10.1006/bbrc.1997.7124 -
Journal of Pharmacological Sciences Jul 2015Previous studies demonstrated that sulfate conjugation is involved in the metabolism of three commonly used breast cancer drugs, tamoxifen, raloxifene and fulvestrant....
Previous studies demonstrated that sulfate conjugation is involved in the metabolism of three commonly used breast cancer drugs, tamoxifen, raloxifene and fulvestrant. The current study was designed to systematically identify the human cytosolic sulfotransferases (SULTs) that are capable of sulfating raloxifene, fulvestrant, and two active metabolites of tamoxifen, afimoxifene and endoxifen. A systematic analysis using 13 known human SULTs revealed SULT1A1 and SULT1C4 as the major SULTs responsible for the sulfation of afimoxifene, endoxifen, raloxifene and fulvestrant. Kinetic parameters of these two human SULTs in catalyzing the sulfation of these drug compounds were determined. Sulfation of afimoxifene, endoxifen, raloxifene and fulvestrant under metabolic conditions was examined using HepG2 human hepatoma cells and MCF-7 breast cancer cells. Moreover, human intestine, kidney, liver, and lung cytosols were examined to verify the presence of afimoxifene/endoxifen/raloxifene/fulvestrant-sulfating activity.
Topics: Catalysis; Cytosol; Estradiol; Fulvestrant; Hep G2 Cells; Humans; MCF-7 Cells; Raloxifene Hydrochloride; Sulfates; Sulfotransferases; Tamoxifen
PubMed: 26169578
DOI: 10.1016/j.jphs.2015.06.004 -
Nucleic Acids Research Nov 1999Conditional DNA excision between two LoxP sites can be achieved in the mouse using Cre-ER(T), a fusion protein between a mutated ligand binding domain of the human... (Comparative Study)
Comparative Study
Temporally-controlled site-specific mutagenesis in the basal layer of the epidermis: comparison of the recombinase activity of the tamoxifen-inducible Cre-ER(T) and Cre-ER(T2) recombinases.
Conditional DNA excision between two LoxP sites can be achieved in the mouse using Cre-ER(T), a fusion protein between a mutated ligand binding domain of the human estrogen receptor (ER) and the Cre recombinase, the activity of which can be induced by 4-hydroxy-tamoxifen (OHT), but not natural ER ligands. We have recently characterized a new ligand-dependent recombinase, Cre-ER(T2), which was approximately 4-fold more efficiently induced by OHT than Cre-ER(T) in cultured cells. In order to compare the in vivo efficiency of these two ligand-inducible recombinases to generate temporally-controlled somatic mutations, we have engineered transgenic mice expressing a LoxP-flanked (floxed) transgene reporter and either Cre-ER(T) or Cre-ER(T2) under the control of the bovine keratin 5 promoter that is specifically active in the epidermis basal cell layer. No background recombinase activity could be detected, while recombination was induced in basal keratinocytes upon OHT administration. Interestingly, a dose-response study showed that Cre-ER(T2) was approximately 10-fold more sensitive to OHT induction than Cre-ER(T).
Topics: Animals; Enzyme Induction; Epidermis; Estrogen Receptor Modulators; Genes, Reporter; Humans; Integrases; Keratinocytes; Mice; Mice, Transgenic; Mutagenesis, Site-Directed; Receptors, Estrogen; Recombinant Fusion Proteins; Tamoxifen; Viral Proteins
PubMed: 10536138
DOI: 10.1093/nar/27.22.4324 -
Breast Cancer Research and Treatment Dec 2007Many women experience symptoms of cyclical mastalgia, such as breast pain, tenderness, and nodularity. Tamoxifen and other drugs have been used to alleviate cyclical... (Randomized Controlled Trial)
Randomized Controlled Trial
BACKGROUND
Many women experience symptoms of cyclical mastalgia, such as breast pain, tenderness, and nodularity. Tamoxifen and other drugs have been used to alleviate cyclical mastalgia symptoms; however, their use is associated with potentially serious side effects. The current study compared the safety and efficacy of two doses of a topical gel containing 4-hydroxytamoxifen (Afimoxifene, formerly known as 4-OHT) with placebo gel for the treatment of moderate to severe cyclical mastalgia.
METHODS
Premenopausal women aged at least 18 years experiencing moderate to severe symptoms were randomized to receive placebo, 2 mg, or 4 mg of Afimoxifene daily delivered as a transdermal hydroalcoholic gel for 4 menstrual cycles. The primary efficacy parameter was change in mean pain intensity as measured by the Visual Analog Scale (VAS) for the seven worst pain score days within a cycle from baseline to the fourth cycle.
RESULTS
After 4 cycles of treatment, statistically significant improvements relative to placebo were measured in mean VAS score in the 4-mg Afimoxifene group (-12.71 mm [95% confidence interval, -0.96 to -24.47; P = 0.034]). Patient global assessment of pain, physician's assessment of pain, tenderness on palpation, and nodularity following 4 cycles of treatment were significantly more likely to show improvements in the 4-mg group, compared with placebo (P = 0.010 [pain]; P = 0.012 [tenderness]; P = 0.017 [nodularity]). Overall, Afimoxifene was well tolerated with few adverse events and no drug-related SAE occurred in any group. There were no changes in menstrual pattern or plasma hormone levels and no breakthrough vaginal bleeding in patients treated with Afimoxifene.
CONCLUSION
After 4 months of treatment, daily topical breast application of Afimoxifene resulted in statistically significant improvements in signs and symptoms of cyclical mastalgia across patient- and physician-rated scales with excellent tolerability and safety.
Topics: Adult; Breast Diseases; Double-Blind Method; Estrogen Antagonists; Female; Gels; Humans; Menstrual Cycle; Middle Aged; Pain Measurement; Tamoxifen
PubMed: 17351746
DOI: 10.1007/s10549-007-9507-x -
Journal of the National Cancer Institute Dec 2003
Review
Topics: Antidepressive Agents, Second-Generation; Antineoplastic Agents, Hormonal; Breast Neoplasms; Cyclohexanols; Cytochrome P-450 CYP2D6; Estrogen Receptor Modulators; Estrogen Replacement Therapy; Female; Fluoxetine; Hot Flashes; Humans; Hydroxylation; Paroxetine; Randomized Controlled Trials as Topic; Selective Estrogen Receptor Modulators; Tamoxifen; Venlafaxine Hydrochloride
PubMed: 14652227
DOI: 10.1093/jnci/djg129 -
Journal of Biochemical and Molecular... 2002Tamoxifen (TAM) is an important chemotherapeutic agent for the treatment of breast cancer. It has also been shown to decrease breast cancer incidence in healthy women at...
Tamoxifen (TAM) is an important chemotherapeutic agent for the treatment of breast cancer. It has also been shown to decrease breast cancer incidence in healthy women at high risk for the disease. The increased risk of endometrial cancer in women has raised concerns in the use of the drug. Tamoxifen has also been shown to be a potent hepatocarcinogen in rats. The oxidative metabolites of TAM include alpha-hydroxytamoxifen (alpha-OH-TAM) and 4-hydroxytamoxifen (4-OH-TAM). The studies on the sulfation of these metabolites are very limited. It has been reported that alpha-OH-TAM is a substrate for rat hydroxysteroid sulfotransferase a (STa). Our studies on the sulfation of 4-OH-TAM demonstrated that 4-hydroxytamoxifen can be sulfated by human liver and human intestinal cytosols. Human phenol-sulfating sulfotransferase and human estrogen sulfotransferase are the major enzymes for the sulfation of 4-OH-TAM. Human dopamine-sulfating sulfotransferase also has sulfation activity for 4-OH-TAM. In contrast, rat liver and intestine cytosols have no detectable sulfation activity for 4-OH-TAM. The results suggest that the alpha-OH-TAM sulfation pathway leads to bioactivation of TAM, and the 4-OH-TAM sulfation pathway leads to detoxification of TAM. This agrees with the fact that TAM is more toxic for rats than for human beings.
Topics: Animals; Caco-2 Cells; DNA Adducts; Female; Humans; Inactivation, Metabolic; Intestine, Small; Kinetics; Liver; Male; Rats; Rats, Sprague-Dawley; Sulfotransferases; Tamoxifen; Tritium; Tumor Cells, Cultured
PubMed: 12481303
DOI: 10.1002/jbt.10048 -
Cancer Treatment Reports 1980This paper reviews the recent laboratory findings about the nonsteroidal antiestrogen, tamoxifen, and its more potent major metabolite, monohydroxytamoxifen. Both... (Review)
Review
This paper reviews the recent laboratory findings about the nonsteroidal antiestrogen, tamoxifen, and its more potent major metabolite, monohydroxytamoxifen. Both compounds stimulate progesterone receptor synthesis in the rat uterus, and there is an inhibition of cell division in the uterine luminal epithelial cells. The effects of tamoxifen in vivo may be a result of the net effects of the parent compound and monohydroxytamoxifen. In rats with dimethylbenzanthracene (DMBA)-induced rat mammary carcinomata, young tumors that are estrogen receptor- and progesterone receptor-rich respond more favorably to tamoxifen that do older estrogen receptor- and progesterone receptor-poor tumors. However, the antitumor effect of tamoxifen in the DMBA-induced rat mammary carcinoma model is probably a result of the blockade of tumor estrogen receptors, a reduction in circulating gonadotropins, lower circulating estrogen levels, and lower circulating prolactin levels. The 30-days treatment of rats with tamoxifen 30 days after DMBA resulted in a dose-related decrease in the appearance and numbers of mammary tumors; however, only continuous therapy maintained animals in a tumor-free state. Monohydroxytamoxifen was a less-potent antitumor agent, probably because it is cleared from the rat more rapidly than tamoxifen. The present laboratory findings support the clinical use of tamoxifen as a treatment of endometrial carcinoma and the resultant metastases and as an adjuvant therapy after surgery for breast cancer.
Topics: 9,10-Dimethyl-1,2-benzanthracene; Animals; Antineoplastic Agents; Estrogen Antagonists; Female; Hydroxylation; Mammary Neoplasms, Experimental; Rats; Receptors, Estrogen; Receptors, Progesterone; Tamoxifen
PubMed: 6775807
DOI: No ID Found -
Annual Review of Genetics 1991
Review
Topics: Amino Acid Sequence; Animals; Carrier Proteins; Gene Expression Regulation; Humans; Ligands; Mifepristone; Molecular Sequence Data; Phosphorylation; Promoter Regions, Genetic; Receptors, Estrogen; Receptors, Glucocorticoid; Receptors, Progesterone; Receptors, Retinoic Acid; Receptors, Thyroid Hormone; Regulatory Sequences, Nucleic Acid; Tamoxifen; Transcription Factors; Transcription, Genetic; Zinc Fingers
PubMed: 1667464
DOI: 10.1146/annurev.ge.25.120191.000513 -
Yao Xue Xue Bao = Acta Pharmaceutica... Sep 2016Tamoxifen (TAM) is the most common nonsteroidal antiestrogen agent, which has been widely used in the prevention of recurrence of estrogen or progesterone... (Review)
Review
Tamoxifen (TAM) is the most common nonsteroidal antiestrogen agent, which has been widely used in the prevention of recurrence of estrogen or progesterone receptor-positive breast cancer in patients. It is metabolized by cytochrome P450 oxidases to its active metabolite (4-hydroxytamoxifen, 4-OH-TAM) and endoxifen (EDF), which played a critical role in the therapy. 4-OH-TAM and EDF have 30- to 100-fold more potency than TAM in the suppression of estrogen-dependent breast cancer cell proliferation. CYP3A4 and CYP2D6, as the key drug-metabolizing enzymes in those metabolic actions, are known to have several alleles. Genetic polymorphisms of CYP2D6 and CYP3A4 will influence the plasma concentrations of active TAM metabolites and clinical outcomes for breast cancer patients treated with TAM. The genetic polymorphisms of drug transporters, involved in the disposition of active TAM metabolites, also have the potential to influence the plasma concentrations of active TAM metabolites and clinical outcome for the treatment of breast cancer. In this review, we summarized the association of the genetic polymorphisms in the metabolic enzymes and transporters involved in the metabolism and disposition of TAM with the metabolite concentration, efficacy and adverse effects of TAM, which provides a fundamental reference for further pharmacogenomic study and clinical use of TAM.
Topics: Antineoplastic Agents, Hormonal; Breast Neoplasms; Cytochrome P-450 CYP2D6; Cytochrome P-450 CYP3A; Estrogen Antagonists; Humans; Pharmacogenetics; Polymorphism, Genetic; Tamoxifen
PubMed: 29924509
DOI: No ID Found -
Environmental Science and Pollution... Jul 2018The estrogen agonistic/antagonistic activity of 16 brominated by-products of parabens was assessed by using a yeast two-hybrid assay transfected with the human estrogen...
The estrogen agonistic/antagonistic activity of 16 brominated by-products of parabens was assessed by using a yeast two-hybrid assay transfected with the human estrogen receptor α. Characterization of synthetic compounds including novel brominated parabens was performed using H-NMR spectroscopy and high-resolution mass spectrometry. For the agonist assay, five C-C alkylparabens exhibited significant activity (P < 0.05) relative to that of 17β-estradiol, ranging from 3.7 × 10 to 7.1 × 10. In contrast, none of the brominated alkyl parabens exhibited agonistic activity. In the antagonist assay, 12 brominated alkylparabens and butylparaben exhibited significant antagonistic activity (P < 0.05). Their antagonistic activity relative to 4-hydroxytamoxifen ranged from 0.11 to 2.5. The antagonist activity of C-C alkylparabens increased with the number of bromine substitutions. Benzylparaben exhibited both agonistic and antagonistic activity, and these activities dissipated or were weakened with increased bromination. Thus, increased bromination appeared to attenuate the estrogen agonistic activity of most parabens such that it resulted in increased antagonistic activity, a feature of parabens that had not been previously described.
Topics: Estrogen Receptor alpha; Estrogens; Halogenation; Humans; Parabens; Protein Binding; Tamoxifen; Two-Hybrid System Techniques
PubMed: 29946845
DOI: 10.1007/s11356-018-2600-3