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

Testicular androgens are known to influence not only the secretion but also the bioactivity and molecular composition of pituitary FSH. In the present study, we investigated the effects of chronic androgen blockade and castration on the molecular heterogeneity of the gonadotrophin. Groups of male adult rats (five animals per group) received one of the following treatments: vehicle, the non-steroidal anti-androgens casodex (20 mg/kg per day) or flutamide (20 mg/kg per day), or castration. After 8 weeks, the animals were killed and individual pituitary homogenates fractionated by isoelectric focusing (IEF) on sucrose density gradients in the pH range 2.5-8. FSH was measured by radioimmunoassay (RIA) in the individual fractions and by invitro bioassay (Sertoli cell aromatase bioassay) in pools of fractions which were combined according to pH intervals of 0.5 units. Bioactive and immunoreactive FSH were also measured in sera and unfractionated pituitary extracts. Testosterone and inhibin were assayed in sera by RIA. A significant increase in serum immunoreactive and bioactive FSH was demonstrated in flutamide-treated and castrated animals, whereas the pituitary content of bioactive FSH remained unchanged in the four groups. Serum testosterone and inhibin were undetectable in castrated animals and significantly increased in those treated with flutamide. By RIA, the IEF profiles of the flutamide-treated and castrated rats showed a significant reduction of the FSH isoforms with 3.5 < pI < 4, with a significant increase in the isoforms with pI > 4 only in the castrated group.(ABSTRACT TRUNCATED AT 250 WORDS)
J Mol Endocrinol 1992 Oct
PMID:Microheterogeneity of pituitary follicle-stimulating hormone in male rats: differential effects of the chronic androgen deprivation induced by castration or androgen blockade. 141 88

NADPH cytochrome c (P-450) reductase was purified from human placental microsomes using a combination of affinity and gel filtration chromatography. Affinity chromatography using agarose-hexane-adenosine 2'5 diphosphate resulted in two protein bands being detected by SDS-PAGE of approximate MwS 68 and 75 kDa. Fractions containing the two proteins were pooled, and then resolved using Sephacryl S-200. Both of the purified proteins displayed enzyme activity, measured by their ability to reduce cytochrome c. The 75 kDa protein obtained was used to immunize three female New Zealand white rabbits. The IgG fraction was partly purified from rabbit sera which suppressed placental microsomal NADPH cytochrome c reductase activity by > 80% using 33% ammonium sulphate. The procured antibody suppressed androstenedione aromatase activity in microsomal preparations of human placental and breast adipose tissue, and NADPH cytochrome c reductase activity in prostate (benign and malignant), MDA-MB-231 breast cancer cells, breast adipose, Hep G2 hepatoma cells and placental microsomal preparations. The extent of NADPH cytochrome c reductase inhibition varied in the order of malignant prostate < benign prostate < MDA < breast adipose < Hep G2 < placenta. The results suggest that human placental NADPH cytochrome c (P-450) reductase shares common antigenic epitopes pertinent to its capability of reducing cytochrome c in all of the above-mentioned tissues. In attempting to associate possible changes in NADPH cytochrome c reductase activity imposed by neoplasia to the obtained immunochemical cross reactivity and enzyme activity results, it was noted that microsomes obtained from MDA cells exhibited enzyme activity significantly less than that of breast adipose microsomes (1.6 and 8.1 nmol/min/mg protein, respectively) and by comparison showed 6% less homology towards the placental antibody. The results obtained for benign and malignant prostate showed no significant difference between the neoplastic states as adjudged by enzyme activity and immunochemical assays.
J Steroid Biochem Mol Biol 1992 Nov
PMID:Immunochemical specificity of placental NADPH cytochrome c (P-450) reductase in neoplastic and non-neoplastic human tissue. 141 86

Several functional domains, especially the active site regions, in aromatase cytochrome P450 were inferred by alignment of amino acid sequences of the enzyme from five species, human, rat, mouse, chicken, and trout, and that of Pseudomonas putida cytochrome P450cam, whose x-ray structure has been determined (Poulos, T.L., Finzel, B.C., and Howard, A.J. (1987) J. Mol. Biol. 195, 687-700). The predicted functions of these domains have been evaluated by site-directed mutagenesis. Eighteen mutants, including seven new mutants, have been generated in this laboratory. The seven newly prepared mutants are Q123E, Q123H, T310S, T310C, R365K, R365A, and N delta 20 (a mutant without the first 20 amino acids). The preparation and characterization of these new mutants are described. The structural model described in this paper should be very useful for future structure-function studies of aromatase by site-directed mutagenesis.
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PMID:Functional domains of aromatase cytochrome P450 inferred from comparative analyses of amino acid sequences and substantiated by site-directed mutagenesis experiments. 828 24

Breast cancer is the most common malignant tumor among women, comprising an estimated 24% of all cancer cases and 18% of all cancer deaths. At least half of the patients with primary breast cancer will ultimately die by metastatic disease. The tumor characteristics, the natural course of the disease and the response to therapy vary strongly. A number of recently detected cell biological parameters such as oncogenes/suppressor genes, growth factors and secretory proteins are more or less important prognostic factors, because they influence the characteristics and behavior of a tumor with respect to metastatic pattern, extent of cellular differentiation, growth rate and response to treatment. However, there is no clear consensus how best to identify patients at high or low risk. In our experience c-myc amplification and pS2 protein are strong prognosticators for relapse rate, while in advanced disease (apart from a negative estrogen/progesterone receptor/pS2 status) amplification of HER2/neu is a good prognosticator for failure to endocrine therapy. In the diagnosis of breast cancer, in vivo imaging of tumors by labeled hormones or other factors also forms a new development which might have implications for treatment too. With respect to treatment both endocrine and chemotherapy can cure a minority of patients with micrometastases, but in patients with advanced disease only a prolongation of (progression-free) survival can be reached. Response rates decrease with increasing tumor load. In the past decade a number of interesting new endocrine agents has been developed such as new (pure) (anti)steroidal agents, vitamins, aromatase inhibitors, analogs of peptide hormones, prolactin inhibitors and growth factor antagonists. However, less is known on the (potential) interaction between hormones, chemotherapeutic agents, retinoids, cytokins, growth factor antagonists and irradiation. Rapid detection of new powerful combination therapies are needed to improve treatment results during the nineties.
J Steroid Biochem Mol Biol 1992 Sep
PMID:Clinical breast cancer, new developments in selection and endocrine treatment of patients. 144 97

Compound 1 [3-(4-aminophenyl)-3-cyclohexylpiperidine-2,6-dione] is a highly potent nonsteroidal aromatase inhibitor of the aminoglutethimide (AG)-type containing an asymmetric carbon atom. 1 and its enantiomers (+)-1 and (-)-1 inhibited human placental aromatase by 50% at 0.3, 0.15, and 4.6 microM, respectively (IC50 AG = 37 microM). A competitive type of inhibition was observed for 1 and (+)-1 (Ki 1 = 3.9 nM, Ki (+)-1 = 2.0 nM, Ki AG = 408 nM). Using solubilized high spin aromatase, 1 showed a type II difference spectrum indicating the interaction of the amino nitrogen with the central Fe(III)-ion of the cytochrome P450 heme component. 1 and (+)-1 inhibited cholesterol side chain cleavage enzyme (desmolase) by 50% at 67 and 82 microM, respectively (IC50 AG = 29 microM). In ACTH-stimulated rat adrenal tissue in vitro, 1 was less active in inhibiting aldosterone and corticosterone production compared to AG (IC50s, 1, 130 and 140 microM, AG, 80 and 50 microM, respectively). In vivo, 1 was superior to AG, too: it showed a stronger inhibition of the plasma estradiol concentration of pregnant mares' serum gonadotropin-primed SD rats, the activity residing mainly in the (+)-enantiomer [ovarian vein: (+)-1, 0.31 mg/kg: 81% inhibition, (-)-1, 0.31 mg/kg: 6%, AG, 1.25 mg/kg: 35%]. Furthermore 1 was much more active in inhibiting the testosterone-stimulated tumor growth of the ovariectomized 9,10-dimethyl-1,2-benzanthracene tumor-bearing SD rat (postmenopausal model). Up to a dose of 600 mg/kg of 1 no central nervous symptom depressive effects were observed in the motility test and the rotarod experiment, whereas AG exhibited ED50s of 62 and 164 mg/kg, respectively.
J Steroid Biochem Mol Biol 1992 Dec
PMID:Evaluation of the racemate and the enantiomers of a new highly active and selective aromatase inhibitor of the aminoglutethimide type. 147 56

Mutant forms of aromatase cytochrome P-450 bearing modifications of amino acid residues Pro308 and Asp309 and expressed in transfected Chinese hamster ovary cells were subjected to kinetic analysis and inhibition studies. The Km for androstenedione for expressed wild type (11.0 +/- 0.3 nM SEM, n = 3) increased 4-, 25- and 31-fold for mutants Pro308Phe, Asp309Asn and Asp309Ala, respectively. There were significant differences in sensitivity among wild type and mutants to highly selective inhibitors of estrogen biosynthesis. 4-Hydroxyandrostenedione (4-OHA) a strong inhibitor of wild type aromatase activity (IC50 = 21 nM and Ki = 10 nM), was even more effective against mutant Pro308Phe (IC50 = 13 nM and Ki = 2.8 nM), but inhibition of mutants Asp309Asn and Asp309Ala was considerably less (IC50 = 345 and 330 nM and Ki = 55 and 79 nM, respectively). Expressed wild type aromatase and Pro308Phe aromatase were strongly inhibited by CGS 16949A (IC50 = 4.0 and 4.6 nM, respectively) whereas mutants Asp309Asn and Asp309Ala were markedly less sensitive (IC50 = 140 and 150 nM, respectively). CGS 18320B produced similar inhibition. Kinetic analyses produced Ki = 0.4 nM for CGS 16949A inhibition of wild type versus 1.1, 37 and 58 nM, respectively, against Pro308Phe, Asp309Asn and Asp309Ala. The results demonstrate significant changes in function resulting from single amino acid modifications of the aromatase enzyme. Our data indicate that mutation in Asp309 creates a major distortion in the substrate binding site, rendering the enzyme much less efficient for androstenedione aromatization. The substitution of Pro308 with Phe produces weaker affinity for androstenedione in the substrate pocket, but this alteration favors 4-OHA binding. Similarly, mutant Pro308Phe exhibits a slightly greater sensitivity to inhibition by CGS 18320B than does the wild type. These results indicate that residues Pro308 and Asp309 play critical roles in determining substrate specificity and catalytic capability in aromatase.
J Steroid Biochem Mol Biol 1992 Dec
PMID:Kinetic properties of aromatase mutants Pro308Phe, Asp309Asn, and Asp309Ala and their interactions with aromatase inhibitors. 147 61

Exemestane (FCE 24304; 6-methylenandrosta-1,4-diene-3,17-dione) is a novel orally active irreversible aromatase inhibitor. Its in vitro and in vivo pharmacological properties have been compared to 4-hydroxyandrostenedione (4-OHA). In preincubation studies with human placental aromatase, exemestane, like 4-OHA, showed enzyme inactivating properties with a similar affinity (Ki 26 vs 29 nM) and a lower rate of inactivation (t1/2 13.9 vs 2.1 min). Conversely, when tested in pregnant mares' serum gonadotropin-treated rats, exemestane was more potent in reducing microsomal ovarian aromatase activity than 4-OHA, after both subcutaneous (ED50 1.8 vs 3.1 mg/kg) and oral dosing (ED50 3.7 vs greater than 100 mg/kg). No interference of exemestane on desmolase or 5 alpha-reductase activity was found. The compound did not show any relevant binding affinity to steroidal receptors, but slight binding to the androgen receptor (approximately 0.2% of dihydrotestosterone), like 4-OHA. In the first phase I trial, healthy postmenopausal volunteers were given single oral doses of exemestane, ranging from 0.5 to 800 mg, and plasma [estrone (E1), estradiol (E2) and estrone sulphate (E1S)] and urinary estrogens (E1 and E2) were measured up to 5-8 days. The minimal effective dose in decreasing estrogens was 5 mg. At 25 mg the maximal suppression was observed at day 3: plasma estrogens fell to 35 (E1), 39 (E2) and 28% (E1S), and urinary estrogens fell to 20 (E1) and 25% (E2) of basal values, these effects still persisting on day 5. No effects on plasma levels of cortisol, aldosterone, 17-hydroxyprogesterone, DHEAS, LH and FSH, and no significant adverse events were observed up to the highest tested dose of 800 mg exemestane.
J Steroid Biochem Mol Biol 1992 Sep
PMID:Exemestane (FCE 24304), a new steroidal aromatase inhibitor. 152 55

Patients (186) with locally advanced or metastatic breast cancer were treated with the aromatase inhibitor 4-hydroxyandrostenedione given parenterally at 3 different doses. 21% of patients responded to treatment, 93% of objective responders whose oestrogen receptor (ER) status was known had ER positive tumours. The drug was well-tolerated particularly at a dose of 250 mg i.m. every fortnight. At this dose, only 4/96 (4%) patients had to discontinue treatment. We conclude that 4-hydroxyandrostenedione is a well-tolerated form of endocrine treatment for postmenopausal patients with breast cancer.
J Steroid Biochem Mol Biol 1992 Sep
PMID:4-Hydroxyandrostenedione treatment for postmenopausal patients with breast cancer. 152 56

The effectiveness in reducing oestrogen exposure, of an aromatase inhibitor, and a sulphatase inhibitor, as measured by in vivo studies in breast cancer patients, has been investigated. 4-Hydroxyandrostenedione (4HA) was shown to diminish plasma oestrogen levels, to inhibit peripheral and local aromatization and to cause a concomitant decrease in the activity of DNA-polymerase-alpha, measured as an indicator of cellular proliferation. The source of oestrone sulphate in breast tissues was examined, and it was shown that the tissue content of this conjugate derived from circulating oestrone, but no evidence could be found for the direct accumulation of conjugate from the plasma. Administration of Danazol was found to cause a fall in plasma oestrone levels, and to diminish the conversion ratio of oestrone sulphate to oestrone in some patients. It also inhibited tissue sulphatase activity. Although it is concluded that this drug is only a weak sulphatase inhibitor, these observations indicate the potential value of developing more efficient sulphatase inhibitors. Enzyme inhibition is now a proven effective treatment for breast cancer and the development of more efficient inhibitors is an important objective.
J Steroid Biochem Mol Biol 1992 Sep
PMID:Inhibition of oestrogen synthesis in postmenopausal women with breast cancer. 152 57

Of the gonadal steroids in the male, testosterone is the most important regulator of gonadotrophin secretion. However, whether testosterone affects gonadotrophin secretion directly or whether it must first be aromatized to estrogens is controversial. We have reported extensively on the endocrine and anti-tumor effects of the non-steroidal aromatase inhibitors CGS 16949A and CGS 20267 in adult female rats. In these animals, both inhibitors potently and selectively inhibit estrogen biosynthesis. Thus these agents can be effectively used in studying estrogen-dependent processes. CGS 16949A was administered for 14 days to adult male rats, over a dose range which in females suppresses estradiol and elevates LH. In male rats a suppression of estradiol was seen, however, there was no significant effect on either serum LH or on the weights of androgen-dependent organs. CGS 16949A, when administered to healthy men at a dose of 1 mg b.i.d. for 10 days, causes a significant fall in plasma estradiol and significant elevations of plasma FSH and testosterone. Dose-dependent suppression of serum estradiol and an increase in serum testosterone and LH are seen after administration of single oral doses of CGS 20267. These results indicate that in the male rat, inhibition of aromatization of testosterone to estrogens does not influence gonadotrophin secretion whereas in men the negative feedback exerted by testosterone on gonadotrophin secretion is dependent on the aromatization of testosterone to estrogens.
J Steroid Biochem Mol Biol 1992 Mar
PMID:Inhibition of estrogen biosynthesis and its consequences on gonadotrophin secretion in the male. 153 3


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