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F Labrie

Publications and source records attributed to F Labrie.

At least 19 recordsLinked to original sources
PubMed1992

Subunit identity of the dimeric 17 beta-hydroxysteroid dehydrogenase from human placenta.

Human placental 17 beta-hydroxysteroid dehydrogenase has been purified with a new rapid procedure based on fast protein liquid chromatography, yielding quantitatively a homogeneous preparation with high specific activity catalyzing the oxidation of 7.2 mumol of estradiol/min/mg of enzyme protein at 23 degrees C, pH 9.2. This preparation was shown to have a subunit mass of 34.5 kDa by sodium dodecyl sulfate-polyacrylamide gel electrophoresis while having a molecular mass of 68 kDa by both Superose-12 gel-filtration and native pore gradient gel electrophoresis. When 17 beta-hydroxysteroid dehydrogenase was expressed in HeLa cells or overproduced in insect cells using the baculovirus expression system, both from its cDNA encoding a protein of 34 kDa, the enzyme had the same migration in native and sodium dodecyl sulfate-gel electrophoresis as the purified one from human placenta and eluted from the Superose-12 column at the same elution volume. Moreover, all the above forms of this enzyme have similar specific activity. These results clearly demonstrate the identity of the three enzyme forms. The enzyme produced from the cDNA is expressed as a dimer, and its two subunits are identical. 17 beta-Hydroxysteroid dehydrogenase subunit identity is thus proved. The NH2-terminal analysis revealed a unique sequence of Ala-Arg-Thr-Val-Val-Leu-Ile for the purified enzyme from placenta, further confirming the above conclusion.

17-Hydroxysteroid Dehydrogenases↗
PubMed1992

Expression of liver-specific member of the 3 beta-hydroxysteroid dehydrogenase family, an isoform possessing an almost exclusive 3-ketosteroid reductase activity.

We have recently characterized two types of rat 3 beta-hydroxysteroid dehydrogenase/delta 5-delta 4 isomerase (3 beta-HSD) isoenzymes expressed in adrenals and gonads. In addition, we have cloned a third type of cDNA encoding a predicted type III 3 beta-HSD protein specifically expressed in the male rat liver which shares 80% similarity with the two other isoenzymes. Transient expression in human HeLa cells of the cDNAs reveals that the type III 3 beta-HSD protein does not display oxidative activity for the classical substrates of 3 beta-HSD, in contrast to the type I 3 beta-HSD isoenzyme. However, in the presence of NADH, type III isoenzyme, in common with the type I isoform, converts 5 alpha-androstane-3,17-dione (A-dione) and 5 alpha-dihydrotestosterone (DHT) to the corresponding 3 beta-hydroxysteroids. In fact, the type I and the type III isoenzymes have the same affinity for DHT with Km values of 5.05 and 6.16 microM, respectively. When NADPH is used as cofactor, the affinity for DHT of the type III isoform becomes higher than that of the type I isoform with Km values of 0.12 and 1.18 microM, respectively. The type III isoform is thus a 3-ketoreductase using NADPH as preferred cofactor which is responsible for the conversion of 3-keto-saturated steroids such as DHT and A-dione into less active steroids.

3-Hydroxysteroid Dehydrogenases↗
PubMed1992

Novel compounds inhibit estrogen formation and action.

Estrogens are well known to play a predominant role in human breast cancer. The current endocrine therapy of breast cancer consists in administering an antiestrogen which blocks the action of estrogens at the receptor level. However, the currently available antiestrogens possess mixed estrogenic and antiestrogenic activity, thus limiting their potential therapeutic efficacy. The present data show that a series of new estrogen derivatives demonstrate not only pure antiestrogenic activity in the sensitive in vivo mouse uterus assay, but simultaneously exert potent inhibitory effects on 17 beta-hydroxysteroid dehydrogenase activity, the enzyme responsible for the formation of 17 beta-estradiol from estrone, the last step in estrogen formation. Such compounds having a dual site of inhibitory action, namely on estrogen formation and on the estrogen receptor, could well lead to an improved endocrine therapy of breast and other estrogen-sensitive cancers as well as other nonmalignant estrogen-sensitive diseases.

17-Hydroxysteroid Dehydrogenases↗
PubMed1992

Incidence of liver toxicity associated with the use of flutamide in prostate cancer patients.

PURPOSE: The incidence of flutamide-related liver toxicity was studied in 1,091 consecutive patients treated for stage C or D prostate cancer with the antiandrogen flutamide and the luteinizing hormone-releasing factor (LHRH) agonist [D-Trp6, des-Gly-NH2(10)] LHRH ethylamide. PATIENTS AND METHODS: Liver function tests, namely measurement of serum aspartate amino-transferase (AST) and alanine aminotransferase (ALT), total bilirubin, alkaline phosphatase, gamma-glutamyl transpeptidase (gamma-GT), and prothrombin and thromboplastin times, were performed at 4, 8, and 12 weeks and every 3 months thereafter. Clinical signs and symptoms of liver dysfunction were also sought. The causal link between the antiandrogen used and liver injury was assessed on the basis of the temporal relationship with the use of the drug in the absence of other possible causes and, in two patients, through rechallenge of the putative causative drug after a period of normalization of liver function. RESULTS: An increase in AST and ALT at fourfold or more above upper normal limits was observed in only four patients (0.36%). Total serum bilirubin and alkaline phosphatase were elevated in only one patient at 126 mmol/L and 640 IU/L, respectively. Among the four patients, only two developed clinical manifestations of liver disease (0.18%). Biopsy was performed in one patient, and the histopathologic findings showed a mixed pattern of cytotoxic and cholestatic changes. All clinical and biologic manifestations of liver toxicity rapidly disappeared upon discontinuation of flutamide alone. No sequelae were observed in the long-term follow-up at 18, 22, 31, and 62 months. The 1,087 remaining patients experienced no or mild (less than fourfold upper normal limit) and transient elevation in aminotransferase serum levels during the first 6 months of treatment, with normalization at later time intervals. CONCLUSION: Despite the fact that the cases reported so far, along with our large series, indicate that the incidence of flutamide-induced liver toxicity is very low, we recommend serial blood aminotransferase measurements at 2 and 4 weeks of treatment in order to detect early signs of possible flutamide-induced hepatic injury, thus avoiding the low potential risk of clinically significant liver toxicity.

Adenocarcinoma↗
PubMed1992

Simultaneous liver and lung toxicity related to the nonsteroidal antiandrogen nilutamide (Anandron): a case report.

We report the case of a 69-year-old patient treated for stage C adenocarcinoma of the prostate with the combination of the luteinizing hormone-releasing hormone agonist [D-Trp6, des-Gly-NH2(10)] LHRH ethylamide and the antiandrogen nilutamide (Anandron) who developed simultaneous liver and lung toxicity. Investigation revealed an abnormal chest radiograph accompanied by altered respiratory function tests, suggesting the diagnosis of interstitial lung disease. This diagnosis was confirmed by an open chest biopsy. At the same time, liver function tests yielded abnormal results. All toxic manifestations disappeared after cessation of treatment with Anandron.

Adenocarcinoma↗
PubMed1992

Transrectal ultrasound evaluation of local prostate cancer in patients treated with LHRH agonist and in combination with flutamide.

We followed total prostate and prostatic tumor volumes in patients who received combination endocrine therapy with the antiandrogen flutamide and the LHRH agonist [D-Trp6,des-Gly-NH2(10)]LHRH ethylamide. Twenty-three men with proved prostatic adenocarcinoma (Stages B1 to D2) were subjected to a transrectal ultrasound (TRUS) study before and after a three-month period of combination antihormonal therapy. A total prostatic volume reduction ranging from 17 percent to 70 percent (median 47%, p less than 0.0001) was observed. An even greater effect was observed on tumor volume which was reduced by 20 percent to 91 percent (median 81%, p less than 0.01). After treatment, the original suspicious zone became nonvisible in 4 cases. The TRUS measurements were confirmed by direct examination of the radical prostatectomy specimen in 7 cases. TRUS is thus a precise, sensitive, and valid method for evaluating the effect of combined antihormonal therapy on normal and tumoral prostatic tissues. These data indicate that combination therapy induces a rapid and marked reduction in glandular and tumoral prostatic volume which could well improve the success of radical prostatectomy and increase the changes of cure of localized prostatic cancer.

Adenocarcinoma↗
PubMed1992

Ontogeny and subcellular localization of 3 beta-hydroxysteroid dehydrogenase (3 beta-HSD) in the human and rat adrenal, ovary and testis.

Primates are unique in having adrenals that secrete large amounts of the precursor sex steroids (PSS) dehydroepiandrosterone (DHEA) and especially DHEA-sulfate. The adrenal PSS require the action of 3 beta-hydroxysteroid dehydrogenase/5-ene-4 ene isomerase (3 beta-HSD), 17 beta-hydroxysteroid dehydrogenase (17 beta-HSD), 5 alpha-reductase and/or aromatase to form the androgen dihydrotestosterone (DHT) or the estrogens 17 beta-estradiol and androst-5-ene-diol. Knowing the crucial role of 3 beta-HSD and 17 beta-HSD in sex steroid biosynthesis both in classical as well as in peripheral steroidogenic tissues, we have concentrated our efforts on the elucidation of the molecular structure of these enzyme families. We have thus characterized two types of human 3 beta-HSD cDNA clones and their corresponding genes which encode deduced proteins of 371 and 372 amino acids and share 93.5% homology. Human type I 3 beta-HSD is the almost exclusive mRNA species expressed in the placenta and skin, while human type II is the predominant mRNA species in the adrenals, ovaries and testes. We have also recently elucidated the structure of three types of rat 3 beta-HSD cDNAs which all encode a 372 amino acid protein. The predicted rat type I and II 3 beta-HSD proteins expressed adrenals, gonads and adipose tissue share 94% homology while they share 80% similarity with the liver-specific type III 3 beta-HSD. Transient expression of human type I and II as well as rat type I and II 3 beta-HSD cDNAs in HeLa human cervical carcinoma cells reveals that 3 beta-ol dehydrogenase and 5-ene-4-ene isomerase activities reside within a single protein and that these cDNAs encode functional 3 beta-HSD proteins. The expressed rat type III protein possesses a unique property catalyzing selectively the reduction of 3 beta-androstane 5 alpha-steroids such as DHT. Furthermore, we have also demonstrated by site-directed mutagenesis that the lower activity of expressed rat type II compared to rat type I 3 beta-HSD protein is due to a change of four amino acid residues potentially involved in a membrane-spanning domain. In parallel, we have characterized the complete nucleotide sequence of human 17 beta-HSD cDNA clones encoding a 327 amino acid protein as well as two in tandem 17 beta-HSD genes. Two major 17 beta-HSD mRNA species have been detected in several tissues due to a tissue-specific alternative site of initiation of transcription.(ABSTRACT TRUNCATED AT 400 WORDS)

Adrenal Glands↗
PubMed1992

Structure and tissue-specific expression of 3 beta-hydroxysteroid dehydrogenase/5-ene-4-ene isomerase genes in human and rat classical and peripheral steroidogenic tissues.

The enzyme 3 beta-hydroxysteroid dehydrogenase/5-ene-4-ene isomerase (3 beta-HSD) catalyzes the oxidation and isomerization of 5-ene-3 beta-hydroxypregnene and 5-ene-hydroxyandrostene steroid precursors into the corresponding 4-ene-ketosteroids necessary for the formation of all classes of steroid hormones. We have recently characterized two types of human 3 beta-HSD cDNA clones and the corresponding genes which encode deduced proteins of 371 and 372 amino acids, respectively, and share 93.5% homology. The human 3 beta-HSD genes containing 4 exons were assigned by in situ hybridization to the p11-p13 region of the short arm of chromosome 1. We have also recently elucidated the structure of three types of rat 3 beta-HSD cDNAs as well as that of one type of 3 beta-HSD from bovine and macaque ovary lambda gt11 cDNA libraries which all encode 372 amino acid proteins. The human type I 3 beta-HSD is the almost exclusive mRNA species detected in the placenta and skin, while the human type II is the predominant mRNA species in the adrenals, ovaries and testes. The predicted rat type I and type II 3 beta-HSD proteins expressed in adrenals, gonads and adipose tissue share 94% homology while they share 80% similarity with the liver-specific type III 3 beta-HSD. Transient expression of human type I and type II as well as rat type I and type II 3 beta-HSD cDNAs in HeLa human cervical carcinoma cells reveals that 3 beta-ol dehydrogenase and 5-ene-4-ene isomerase activities reside within a single protein and these cDNAs encode functional 3 beta-HSD proteins that are capable of converting 3 beta-hydroxy-5-ene-steroids into 3-keto-4-ene derivatives as well as the interconversion of 3 beta-hydroxy and 3-keto-5 alpha-androstane steroids. We have found that the rat type III mRNA species was below the detection limit in intact female liver while, following hypophysectomy, its accumulation increased to 55% of the levels measured in intact or HYPOX male rats, an increase which can be blocked by administration of ovine prolactin (oPRL). In addition, in female rats, treatment with oPRL for 10 days starting 15 days after HYPOX, markedly decreased ovarian 3 beta-HSD mRNA accumulation accompanied by a similar decrease in 3 beta-HSD activity and protein levels. Treatment with the gonadotropin hCG reversed the potent inhibitory effect of oPRL on these parameters and stimulated 3 beta-HSD mRNA levels in ovarian interstitial cells.(ABSTRACT TRUNCATED AT 400 WORDS)

Amino Acid Sequence↗
PubMed1992

Estrogen-stimulated glucuronidation of dihydrotestosterone in MCF-7 human breast cancer cells.

The non-aromatizable androgen dihydrotestosterone (DHT) has been shown to exert a potent inhibitory effect on the proliferation of some human breast cancer cell lines. DHT, however, has little or no significant inhibition on MCF-7 cell proliferation in either the presence or absence of estradiol (E2). Since the metabolism of DHT into non-active compounds may be responsible for the observed lack of androgenic effect in this cell line, we have investigated the metabolic fate of labeled DHT in MCF-7 cells. A time course incubation was performed with 1 nM [3H]DHT and analysis of the various metabolites formed revealed a time-dependent increase in glucuronidated steroids which was stimulated more than 4-fold by 0.1 nM E2. The major glucuronidated steroid was androstane-3 alpha, 17 beta-diol in both control and E2-stimulated cells, comprising 22 +/- 1.2% and 30 +/- 0.6% of the total radioactivity in the medium, respectively. Other steroid glucuronides observed included DHT, androstane-3 beta,17 beta-diol, and androsterone, all of which were elevated in the E2-treated cells relative to control values. The present data show that E2 exerts a stimulatory effect on the glucuronidation of androgens and their metabolites in the estrogen-dependent breast cancer cell line MCF-7. Since glucuronidation is an effective means of cellular elimination of active steroids, such a pathway may be considered as a possible site of regulation of breast cancer cell growth by hormones.

Breast Neoplasms↗
PubMed1992

Distribution of 17 beta-hydroxysteroid dehydrogenase gene expression and activity in rat and human tissues.

The interconversion of estrone (E1) and 17 beta-estradiol (E2), androstenedione (4-ene-dione) and testosterone (T), as well as dehydroepiandrosterone and androst-5-ene-3 beta,17 beta-diol is catalyzed by 17 beta-hydroxysteroid dehydrogenase (17 beta-HSD). The enzyme 17 beta-HSD thus plays an essential role in the formation of all active androgens and estrogens in gonadal as well as extragonadal tissues. The present study investigates the tissue distribution of 17 beta-HSD activity in the male and female rat as well as in some human tissues and the distribution of 17 beta-HSD mRNA in some human tissues. Enzymatic activity was measured using 14C-labeled E1, E2, 4-ene-dione and T as substrates. Such enzymatic activity was demonstrated in all 17 rat tissues examined for both androgenic and estrogenic substrates. While the liver had the highest level of 17 beta-HSD activity, low but significant levels of E2 as well as T formation were found in rat brain, heart, pancreas and thymus. The oxidative pathway (E2----E1, T----4-ene-dione) was favored over the reverse reaction in almost all rat tissues while in the human, almost equal rates were found in most of the 15 tissues examined. The widespread distribution of 17 beta-HSD in rat and human tissues clearly indicates the importance of this enzyme in peripheral sex steroid formation or intracrinology.

17-Hydroxysteroid Dehydrogenases↗
PubMed1992

Expression of human 17 beta-hydroxysteroid dehydrogenase in mammalian cells.

The insert of 1278 bp containing the entire coding region of cDNA encoding human 17 beta-hydroxysteroid dehydrogenase (17 beta-HSD) was inserted into a pHS1 vector and expressed in HeLA human cervical carcinoma cells and COS-1 monkey kidney tumor cells. Western blot analysis indicated that the expressed protein migrates at the same position as the purified enzyme and is recognized by the antibody raised against purified human placental 17 beta-HSD. The expressed enzyme efficiently catalyzes the interconversion of estrone and estradiol while dehydroepiandrosterone and 5-androstene-3 beta,17 beta-diol are interconverted at a lower rate. The present data suggest the existence of two 17 beta-HSDs.

17-Hydroxysteroid Dehydrogenases↗
PubMed1992

Serum prostate specific antigen as pre-screening test for prostate cancer.

Prostate cancer has become the most common cancer and the second cause of death due to cancer in men in North America. Since curative therapies are limited to early stages of the disease, the availability of an efficient, easy to perform, widely acceptable and cost-effective method of early detection of prostate cancer is particularly important. Thus, digital rectal examination, transrectal ultrasonography of the prostate as well as measurements of serum prostate specific antigen (PSA) were performed independently in a series of 1,002 men between 45 and 80 years old randomly selected from the electoral rolls of Quebec City and its vicinity as part of a screening program for prostate cancer. Using this population of randomly chosen men, various cutoff serum PSA values were selected in an attempt to find the optimal decision threshold that would indicate a much greater risk of having prostatic cancer. At a threshold value of 3.0 micrograms./l. the sensitivity and specificity of the test are 80.7 and 89.6%, respectively, while the area under the receiver operating characteristic curve reflecting the accuracy of the test is 87.8 +/- 3.3% (plus or minus standard deviation). Moreover, the negative predictive value was estimated at 98.6%, thus leaving only a 1.4% chance of missing cancer when the serum PSA value was 3.0 micrograms./l. or less. Most importantly, such a threshold level of serum PSA retains only 19% of the whole cohort as candidates for transrectal ultrasonography and expensive diagnostic procedures, thus leading to the finding of 1 prostate cancer of 4 such examinations. The present data indicate that simple measurement of serum PSA can be used efficiently as a pre-screening test for prostate cancer in the general population to identify, at a low cost, the subpopulation of men at a much greater risk of having prostate cancer, and who should then be submitted to the more elaborate and expensive diagnostic procedures.

Age Factors↗
PubMed1992

Congenital adrenal hyperplasia due to point mutations in the type II 3 beta-hydroxysteroid dehydrogenase gene.

Classical 3 beta-hydroxysteroid dehydrogenase/delta 5-delta 4-isomerase (3 beta-HSD) deficiency is an autosomal recessive form of congenital adrenal hyperplasia characterized by a severe impairment of steroid biosynthesis in both the adrenals and the gonads. We describe the nucleotide sequence of the two highly homologous genes encoding 3 beta-HSD isoenzymes in three classic 3 beta-HSD deficient patients belonging to two apparently unrelated pedigrees. No mutation was detected in the type I 3 beta-HSD gene, which is mainly expressed in the placenta and peripheral tissues. Both nonsense and frameshift mutations, however, were found in the type II 3 beta-HSD gene, which is the predominant 3 beta-HSD gene expressed in the adrenals and gonads, thus providing the first elucidation of the molecular basis of this disorder.

3-Hydroxysteroid Dehydrogenases↗
PubMed1992

Characterization, expression, and immunohistochemical localization of 3 beta-hydroxysteroid dehydrogenase/delta 5-delta 4 isomerase in human skin.

Three beta-hydroxysteroid dehydrogenase/delta 5-delta 4 isomerase (3 beta-HSD) catalyses an obligatory step in the biosynthesis of all classes of hormonal steroids, namely, the oxidation/isomerization of 3 beta-hydroxy-5-ene steroids into the corresponding 3-keto-4-ene steroids in gonadal as well as in peripheral tissues. Because humans are unique with some primates in having adrenals that secrete large amounts of the steroid precursors dehydropiandrosterone (DHEA) and its sulfate (DHEA-S) and its exceptionally large volume makes the skin an important site of steroid biosynthesis, we have isolated and characterized cDNA clones encoding 3 beta-hydroxysteroid dehydrogenase/delta 5-delta 4 isomerase from a human skin lambda gt11 library. The longest clone obtained contains the entire coding sequence for type I 3 beta-HSD (372 amino acids) as well as an additional 131 nucleotides in the 5'-untranslated region. The insert of 1647 bp containing the entire coding region has been inserted in a pCMV expression vector and transfected into human cervical carcinoma cells (HeLa). The expressed enzyme efficiently catalyzes the transformation of pregnenolone, DHEA, and dihydrotestosterone into progesterone, 4-androstenedione, and 5 alpha-androstane-3 beta, 17 beta-diol, respectively. Using the enzyme expressed in HeLa cells, we have shown cyproterone acetate, a progestin used in the treatment of acne and hirsutism, as well as norgestrel and norethindrone, two steroids widely used as oral contraceptives, to be relatively potent inhibitors, with Ki values of 0.38 microM, 1.3 microM, and 1.2 microM, respectively. Immunohistochemical localization of 3 beta-HSD, illustrated by using an antibody raised against human placental 3 beta-HSD, shows that the enzyme is localized in sebaceous glands.

Amino Acid Sequence↗
PubMed1992

Androgenic 17 beta-hydroxysteroid dehydrogenase activity of expressed rat type I 3 beta-hydroxysteroid dehydrogenase/delta 5-delta 4 isomerase.

Transient expression in nonsteroidogenic mammalian cells of the rat wild type I and type II 3 beta-hydroxysteroid dehydrogenase/delta 5-delta 4-isomerase (3 beta-HSD) cDNAs shows that the encoded proteins, in addition to being able to catalyze the oxidation and isomerization of delta 5-3 beta-hydroxysteroid precursors into the corresponding delta 4-3-ketosteroids, interconvert 5 alpha-dihydrotestosterone (DHT) and 5 alpha-androstane-3 beta,17 beta-diol (3 beta-diol). When homogenate from cells transfected with a plasmid vector containing type I 3 beta-HSD is incubated in the presence of DHT using NAD+ as cofactor, a somewhat unexpected metabolite is formed, namely 5 alpha-androstanedione (A-dione), thus indicating an intrinsic androgenic 17 beta-hydroxysteroid dehydrogenase (17 beta-HSD) activity of this 3 beta-HSD isoform. Although the relative Vmax of 17 beta-HSD activity is 14.9-fold lower than that of 3 beta-HSD activity, the Km value for the 17 beta-HSD activity of type I 3 beta-HSD is 7.97 microM, a value which is in the same range as the conversion of DHT into 3 beta-diol which shows a Km value of 4.02 microM. Interestingly, this 17 beta-HSD activity is highly predominant in unbroken cells in culture, thus supporting the physiological relevance of this "secondary" activity. Such 17 beta-HSD activity is inhibited by the classical substrates of 3 beta-HSD, namely pregnenolone (PREG), dehydroepiandrosterone (DHEA), delta 5-androstene-3 beta,17 beta-diol (delta 5-diol), 5 alpha-androstane-3 beta,17 beta-diol (3 beta-diol) and DHT, with IC50 values of 2.7, 1.0, 3.2, 6.2, and 6.3 microM, respectively. Although dual enzymatic activities have been previously reported for purified preparations of other steroidogenic enzymes, the present data demonstrate the multifunctional enzymatic activities associated with a recombinant oxidoreductase enzyme. In addition to its well known 3 beta-HSD activity, this enzyme possesses the ability to catalyze DHT into A-dione thus potentially controlling the level of the active androgen DHT in classical steroidogenic as well as peripheral intracrine tissues.

17-Hydroxysteroid Dehydrogenases↗
PubMed1992

Additive stimulatory action of glucocorticoids and androgens on basal and estrogen-repressed apolipoprotein-D messenger ribonucleic acid levels and secretion in human breast cancer cells.

Recent elucidation of the amino acid sequence of the progesterone-binding protein GCDFP-24, the major protein found in human breast gross cystic disease fluid, reveals that this glycoprotein corresponds to apolipoprotein-D (apo-D), a member of the alpha 2-microglobulin superfamily which binds small hydrophobic ligands. The present study describes the multiple hormonal control of apo-D mRNA levels, intracellular protein content, as well as secretion compared to cell proliferation in human ZR-75-1 breast cancer cells. In these cells, exposure to the synthetic glucocorticoid dexamethasone (DEX) markedly decreases basal as well as 17 beta-estradiol (E2)-induced cell proliferation while causing a maximal 10-fold stimulation of apo-D secretion in the presence or absence of E2. Incubation with 500 nM DEX or 10 nM dihydrotestosterone (DHT), alone and in combination, markedly increased apo-D mRNA/actin mRNA ratios by 16-, 22-, and 28-fold, respectively. Exposure to 1 nM E2 decreased the apo-D mRNA/actin mRNA ratio by 65%. In E2-treated cells, simultaneous exposure to DHT, DEX, and DHT plus DEX markedly increased the apo-D mRNA/actin mRNA ratios by 50-, 35-, and 105-fold, respectively. The stimulatory effect of DEX on intracellular apo-D content and secretion was also additive to that of the androgen DHT in the presence or absence of E2. The present study provides the first data describing the hormonal regulation of apo-D mRNA levels and intracellular protein content and demonstrates the effect of glucocorticoids alone as well as their interaction with androgens and estrogens on these parameters as well as on apo-D secretion. As shown in the present data, the effects of steroids on apo-D gene expression, intracellular apo-D protein content, and secretion are opposite their respective specific effects on cell proliferation in human ZR-75-1 breast cancer cells.

Actins↗