Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:3.1.6.1 (sulfatase)
3,205 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The activities of aromatase and estrone sulfatase which are important enzymes involved in the local production of estrogen in breast cancer tissue were measured to examine their availability in endocrine therapy and their clinical significance. The materials obtained were breast cancer tissue, noncancerous mammary gland and breast fat tissue from twenty eight patients with breast cancer, and mammary gland tissue from eight patients with benign breast disease. After centrifugation of homogenized tissue at 1000 X g, the supernatant of breast cancer tissue or mammary gland and the subnatant of breast fat tissue were used as enzyme sources. Aromatase activity was measured by 3H2O release assay using (1 beta-3H) androstenedione as the substrate, while estrone sulfatase activity was estimated from the conversion rate of (6,7-3H)estrone-3-sulfate to estrone. Aromatase activities were 25.1 +/- 12.4 (mean +/- S.D.) fmol/mg protein/h in twenty seven breast cancer tissue specimens, 11.0 +/- 6.1 fmol/mg protein/h in sixteen noncancerous mammary gland tissue specimens, 9.3 +/- 10.0 fmol/mg protein/h in twenty seven breast fat tissue specimens, and 7.7 +/- 5.5 fmol/mg protein/h in eight mammary gland tissue specimens from patients with benign breast disease. The aromatase activity in breast cancer tissue was significantly higher than that in noncancerous mammary gland, breast fat tissue and benign breast lesions (p less than 0.001). Estrone sulfatase activity was 4.0 +/- 3.5 nmol/mg protein/h in nineteen breast cancer tissue specimens, but was almost undetectable in eleven noncancerous mammary tissue specimens and eight benign breast lesions. These results suggest the relatively high local production of estrogen, mediated by aromatase or estrone sulfatase in breast cancer tissue.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:[Local production of estrogen via aromatase and estrone sulfatase in breast cancer tissue]. 279 62

Aromatase has been identified in the telostean, avian, and mammalian pituitaries, although its cellular location(s) is not yet certain. To address this question, experiments were performed in tilapia (Oreochromis mossambicus), a species which has been well characterized with respect to the intraglandular distribution of the different pituitary cell types. To estimate aromatase, glands were microdissected into rostral pars distalis (RPD), proximal pars distalis (PPD), and neurointermediate lobe (NIL) and organs were cultured in the presence of [3H]androstenedione for 16-24 hr. [3H]Estrogen products were isolated and quantified after ether extraction, hydrolysis with glucuronidase-sulfatase, thin-layer chromatography, and phenolic partition. Authentic estrone or estradiol-17 beta were produced by all pituitary regions and also by the urophyseal region of the spinal cord. Aromatase was two to five times higher in PPD than in RPD or NIL and similar to activity in adjacent hypothalamus-preoptic area (HPOA). Much lower estrogen yields were obtained in cultures of cerebellum, urophysis, and other cord regions. Since the PPD contains most of the somatotropes, these data are consistent with earlier studies implicating GH3/GH4 cell strains as an enriched enzyme source, although its presence in other cell types cannot be ruled out. The unusually high and localized aromatase in tilapia pituitary renders this species a useful model for studying the targets and functional importance of estrogen as a parahormone in the pituitary.
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PMID:Aromatase is concentrated in the proximal pars distalis of tilapia pituitary. 341 Feb 99

One-third of the cases of breast cancer in postmenopausal women are hormone-dependent and the lesions regress upon treatment with antiestrogens or inhibition of estrogen biosynthesis. In these patients, estrogens are synthesized in extraglandular tissues from adrenal precursors and re-enter plasma to produce estrone levels of 52 +/- 6.5 pg/ml (mean +/- SEM) and estradiol concentrations of 13.1 +/- 0.7 pg/ml. However, the fact that the levels of estrogen in breast tumor tissue are an order of magnitude higher than plasma levels suggested the possibility of in situ estrogen production. To address this possibility, we measured several enzymes involved in estradiol biosynthesis in human tumors. Forty-eight of 61 tumors contained aromatase (estrogen synthetase) activity ranging from 5-80 pg/gm protein per hour. By comparison, the levels of estrone sulfatase were 10(6) higher, ranging from 0.8-125 micrograms/gm protein per hour. Because the sulfatase enzyme was of lower affinity (i.e., Km = 27 microM) than that of aromatase (i.e., 0.027 microM), the amount of estrogen formed under conditions of similar substrate concentrations was compared and found to be 10-fold higher via the sulfatase enzyme. In 41 additional tumors, the 17 beta-hydroxysteroid dehydrogenase enzyme, catalyzing the conversion of estrone to estradiol, was uniformly present. To test the biologic relevance of the estrone sulfate to estrone to estradiol pathway, estrogen-dependent nitrosomethylurea rat mammary tumors were grown in soft agar in the presence of estrone sulfate. Concentrations of estrone sulfate of 10(-6) microM significantly (p less than 0.01) stimulated colony formation in this system in which 75.5-98.6% of estrone sulfate was converted to estrone and 0.2 to 6% to estradiol. These data support the hypothesis that mammary carcinomas can synthesize estradiol in situ from circulating estrogen precursor and that local conversion is biologically important. On the basis of comparative data, the estrone sulfate to estrone to estradiol pathway is quantitatively more important than that involving androstenedione to estrone to estradiol.
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PMID:Enzymatic control of estrogen production in human breast cancer: relative significance of aromatase versus sulfatase pathways. 352 46

Estrogens provide the major hormonal support for endocrine-dependent human mammary neoplasms. In postmenopausal women, the extraglandular aromatization of the adrenal prehormone, androstenedione to estrone is the major pathway for estrogen biosynthesis. Estrone can then be converted into estradiol or into an inactive conjugate, estrone sulfate. Recent data suggest that the estrogens may also be synthesized in situ by human breast tumors, either from androstenedione via aromatase, or from estrone sulfate via the enzyme, sulfatase. Our enzyme kinetic studies support the predominance of the sulfatase pathway for in situ estrogen biosynthesis. The ability of estrone sulfate to stimulate colony formation of the nitrosomethylurea-induced rat mammary tumor in the clonogenic assay, suggests that this in situ pathway has biologic relevance. Aromatase inhibitors can be used to suppress the levels of circulating estrone, estrone sulfate, and estradiol in postmenopausal women. Aminoglutethimide, the major inhibitor currently used clinically, acts in a competitive fashion and blocks cholesterol side chain cleavage and 11 beta-hydroxylase as well as aromatase. Clinical studies indicate that the combination of aminoglutethimide plus replacement glucocorticoid causes breast tumor regression with the same frequency and for the same duration as surgical ablative therapies such as adrenalectomy or hypophysectomy. Aminoglutethimide also induces a similar rate of tumor regression as achieved with the antiestrogen, tamoxifen. However, because tamoxifen is associated with fewer side effects, this antiestrogen is to be preferred over use of aminoglutethimide as first-line hormonal treatment for women with breast cancer. Several specific suicide inhibitors of aminoglutethimide such as 4-hydroxy-androstenedione are being developed and have proven effective in early clinical trials with breast cancer patients. Further development of active aromatase inhibitors should allow precise control of estradiol levels in women with breast cancer. This ability to perform an 'estrogen clamp' may allow new strategies to be developed in which hormone depletion followed by repletion can produce a synchronization of tumor cell DNA synthesis. If achievable, such manipulations may allow potentiation of the effects of cytotoxic chemotherapy. This latter concept is currently being rigorously tested in basic and in clinical investigative studies.
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PMID:Aromatase inhibitors for treatment of breast cancer: current concepts and new perspectives. 352 4

Recent treatment strategies have been directed toward blockade of estrogen action or inhibition of estrogen biosynthesis as a means of inducing regression of hormone-dependent breast cancer. The major source of estrogen in postmenopausal women is the peripheral conversion of androstenedione to estrone through the enzyme aromatase. It is known that aromatase activity increases proportionately with degree of obesity in women. To test the importance of this modulatory factor, we correlated body weight with estrogen excretion in our population of patients with breast cancer and found significant relationships. In situ production of estradiol from plasma precursors within breast cancer tissue may provide another source of estrogen. Major enzymes mediating estrogen biosynthesis were found to be present in tumor biopsy specimens. Aromatase activity was found to be present in 48/61 human tumors, sulfatase in 35/35, and 17 beta -hydroxysteroid dehydrogenase in 41/41. One inhibitor of aromatase, aminoglutethimide, has been extensively studied in patients with breast cancer. The additional effects of this drug on cholesterol side-chain cleavage and on 11-hydroxylase activity require coadministration of replacement glucocorticoid in treatment regimens. In pilot trials, 37% of patients experienced objective tumor regression with a combination of 1000 mg aminoglutethimide and 40 mg hydrocortisone daily. In randomized clinical trials with this regimen, aromatase inhibition with aminoglutethimide produced tumor regression with similar frequency as did surgical hypophysectomy, surgical adrenalectomy, or tamoxifen administration. The side effects of aminoglutethimide, including lethargy, skin rash, and ataxia complicate its use even though these problems are generally transient. Regimens of low-dose aminoglutethimide are being developed to reduce these side effects. Low-dose aminoglutethimide appears to block aromatase effectively and to have limited side effects, and is undergoing extensive clinical trial. A more specific aromatase inhibitor, 4-hydroxyandrostenedione, is now also being tested clinically, whereas MDL 18962, another new selective inhibitor, is undergoing study in animals.
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PMID:Inhibition of aromatase as treatment of breast carcinoma in postmenopausal women. 354 61

Clinical and biochemical data of 16 typical cases of placental sulfatase deficiency have been observed. In vivo loading tests with DHA-S allowed us to make a prenatal diagnosis. In vitro experiments gave confirmation, showing zero or virtually zero placental sulfatase activity towards delta 5P or DHA sulfates Aromatase activities, when tested, were normal or more often less than standard values, the latter showing themselves rather large individual variations. All pregnancies were associated with the delivery of male neonates in good health but 3. The 15 living babies have been developing normally since then. These results, together with those reported in the literature, suggest that placental sulfatase deficiency is under control of an X-linked recessive character, this being supported by the recent observation of such a disorder in two sisters simultaneously pregnant. As to the high frequency problem of cesarian section, pointed out by several authors, we cannot conclude, from our own observations, that the defect has an obvious influence on the good outcome of labor, as 10 out of the 16 women delivered vaginally near term.
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PMID:Placental sulfatase deficiency: clinical and biochemical study of 16 cases. 644 1

Aromatase, estrone (E1) sulfatase and E1 sulfotransferase activities were examined in endometrium and endometrial cancer tissue preparations. Aromatase and E1 sulfatase activities in endometrial cancer tissues were found to be significantly higher than in normal endometrial tissues. However, E1 sulfotransferase activity did not differ between benign and malignant tissue. We also examined the effect of testosterone (T) on aromatase activity and tritiated thymidine uptake (DNA synthesis) in various cultured cervical or corpus endometrial cancer cell lines (OMC-4, HHUA, Ishikawa, HEC-59). The results demonstrated that only the HEC-59 cell line had high aromatase activity and increased its DNA synthesis in response to T. This increase of DNA synthesis by T was not suppressed by simultaneous addition of cyproterone acetate, but was by tamoxifen. These data suggest that in situ estrogen production in endometrial cancer tissue is biologically important and that aromatase in cancer cells may contribute partially to cell proliferation if androgen substrate is provided.
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PMID:Estrogen productivity of endometrium and endometrial cancer tissue; influence of aromatase on proliferation of endometrial cancer cells. 847 61

The importance of estrogens in bone metabolism is illustrated by the accelerated bone loss and increase in osteoporotic fractures associated with postmenopausal estrogen deficiency. In this study, the expression and activity of the enzymes involved in estrogen metabolism in human osteoblastic cells were investigated in relation to differentiation of these cells. PCR reactions using mRNA from an in vitro differentiating human cell line (SV-HFO) were performed to assess mRNA expression of the enzymes aromatase, different subtypes of 17beta-hydroxysteroid dehydrogenase (17beta-HSD), and steroid sulfatase. Aromatase, sulfatase, and 17beta-HSD type 2 and 4 were found to be expressed throughout differentiation. Expression of 17beta-HSD type 3, however, was relatively weak, except for early time points in differentiation. Type 1 17beta-HSD expression was not detected. Aromatase activity decreased during differentiation, as was demonstrated by the conversion of androstenedione (A) and testosterone (T) into estrone (E(1)) and estradiol (E(2)), respectively. The 17beta-HSD isozymes catalysing a reductive reaction convert androstenedione and estrone into testosterone and estradiol, respectively. Their activity declined with differentiation. Analysis of 17beta-HSD activity indicated both oxidative (E(2) to E(1); T to A) and reductive (E(1) to E(2); A to T) metabolism at all stages of osteoblast differentiation. Both activities declined as cells moved toward a differentiating mineralizing phenotype. However, the oxidative reaction was increasingly in favor of the reductive reaction at all times during differentiation. Sulfatase activity, as demonstrated by the conversion of estrone-sulfate into estrone, was constant during differentiation. In conclusion, we have demonstrated that all enzymes necessary for estrogen metabolism are expressed and biologically active in differentiating human osteoblasts. The activity of aromatase and 17beta-HSD was found to be dependent on the stage of cell differentiation. In addition, human osteoblasts effectively convert estradiol into estrone. The efficacy of osteoblasts to synthesize estradiol may determine the ultimate change in rate of bone turnover after menopause, as well as the development of osteoporosis. Moreover, the enzymes involved in the metabolism of estradiol may form a target for intervention.
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PMID:Estradiol formation by human osteoblasts via multiple pathways: relation with osteoblast function. 1053 74

Aromatase inhibitors in clinical use block the biosynthesis of estrogens. Hydrolysis of estrone 3-sulfate by steroid sulfatase is an important additional source of tumor estrogen, and blockade of both enzymes should provide a more effective endocrine therapy. Sulfamoylated derivatives of the aromatase inhibitor YM511 inhibited sulfatase and aromatase in JEG-3 cells with respective IC(50) values of 20-227 and 0.82-100 nM (cf. letrozole, 0.89 nM). One dual inhibitor was potent against both enzymes in vivo, validating the concept.
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PMID:First dual aromatase-steroid sulfatase inhibitors. 1285 49

Despite the dramatic fall in plasma estrogen levels at menopause, only minor differences in breast tissue estrogen levels have been reported comparing pre- and postmenopausal women. Thus, postmenopausal breast tissue has the ability to maintain concentrations of estrone (E1) and estradiol (E2) that are 2-10- and 10-20-fold higher than the corresponding plasma estrogen levels. This finding may be explained by uptake of estrogens from the circulation and/or local estrogen production. Local aromatase activity in breast tissue seems to be of crucial importance for the local estrogen production in some patients while uptake from the circulation may be more important in other patients. Beside aromatase, breast tissue expresses estrogen sulfotransferase and sulfatase as well as dehydrogenase activity, allowing estrogen storage and release in the cells as well as conversions between estrone and estradiol. The activity of the enzyme network in breast cancer tissue is modified by a variety of factors like growth factors and cytokines. Aromatase inhibitors have been used for more than two decades in the treatment of postmenopausal metastatic breast cancer and are currently investigated in the adjuvant treatment and even prevention of breast cancer. Novel aromatase inhibitors and inactivators have been shown to suppress plasma estrogen levels effectively in postmenopausal breast cancer patients. However, knowledge about the influence of these drugs on estrogen levels in breast cancer tissue is limited. Using a novel HPLC-RIA method developed for the determination of breast tissue estrogen concentrations, we measured tissue E1, E2 and estrone sulfate (E1S) levels in postmenopausal breast cancer patients before and during treatment with anastrozole. Our findings revealed high breast tumor tissue estrogen concentrations that were effectively decreased by anastrozole. While E1S was the dominating estrogen fraction in the plasma, estradiol was the estrogen fraction with the highest concentration in tumor tissue. Moreover, plasma estrogen levels did not correlate with tissue estrogen concentrations. The overall experience with aromatase inhibitors and inactivators concerning their influences on breast tissue estrogen concentrations is summarized.
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PMID:Breast cancer tissue estrogens and their manipulation with aromatase inhibitors and inactivators. 1462 18


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