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Although the role of androgens and AR in breast cancer genesis, development of breast cancer and tumor responsiveness to endocrine therapies is poorly understood, the widespread expression of AR suggests that it may be of biological and clinical importance in human breast cancer.
Although there have been several studies suggesting the involvement of growth factor receptor tyrosine kinases in ligand-independent activation of the androgen receptor (AR) and progression of prostate cancer, limited studies have been reported actually showing the enhancement of phosphorylation of the AR in vivo in response to growth factors or activation of their receptors in prostate cancer cells. In this study, we have demonstrated that overexpression of HER2/Neu enhanced in vivo phosphorylation of the AR and MAP kinase in DU-145 cells, and that the HER2/Neu inhibitor TAK165 reduced the HER2/Neu-enhanced phosphorylated AR and MAP kinase, indicating that the MAP kinase pathway seems to be involved in the phosphorylation of the AR by HER2/Neu. Both HER2/Neu inhibitor TAK165 and EGFR tyrosine kinase inhibitor gefitinib ('Iressa', ZD1839) successfully reduced the HER2/Neu-induced transactivation activity of the AR in PC-3 and DU-145 cells, suggesting that these inhibitors are possible therapeutic drugs for patients with hormone-refractory prostate cancer. The transactivation activity of the AF-1+DBD of the AR was enhanced by HER2/Neu overexpression while that of the AF-2+DBD was not, demonstrating that the enhancement of the AR activity by HER2/Neu was mainly mediated through the AF-1 of the AR.
Although sex hormones had been thought to be essential for normal skeletal development and maintenance of bone mass, the physiological role of androgen receptor (AR) in skeletal tissues was not well established. To reveal physiological function of AR on skeletal tissues, we generated AR deficient mice (AR KO) by means of the Cre-loxP system that was used to avoid the problem of male infertility and analyzed their phenotype in skeletal tissues. It was indicated that AR contributes to maintain bone mass in male, but not in female in mice. However, recent studies suggested the contribution of sex hormones to maintain bone mass is different not only between sexes but among species due to the difference of aromatase activity.
Testosterone propionate (TP) administration at the time of facial nerve injury in the adult hamster augments the regenerative properties of the injured facial motoneurons (FMN), with the androgen receptor (AR) playing a key role in mediating the actions of TP on facial nerve regeneration. The purpose of the present study was to determine the effects of axotomy on AR mRNA expression in FMN. This was accomplished using in situ hybridization in conjunction with a (35)S-labeled AR riboprobe. Gonadally intact adult male and gonadectomized (gdx) adult female hamsters were subjected to a right facial nerve axotomy, with the left side serving as internal, unoperated control. Half the animals were subcutaneously implanted with a 10-mm TP Silastic capsule, and the other half were sham-implanted. An additional group of nonaxotomized, gonadally intact males was also included. Postaxotomy survival times were 1, 4, and 7 days. At 1 postoperative day 1, there were no effects of axotomy on AR mRNA levels. By postoperative days 4 and 7, axotomy caused a significant decrease in AR mRNA levels in FMN of gonadally intact males, relative to either the contralateral control FMN of the same animals or FMN from the group of gonadally intact males that were not subjected to facial nerve axotomy. There were no significant differences between AR mRNA levels in contralateral control FMN and FMN from the gonadally intact group of nonaxotomized males. TP administration at the time of axotomy had no effect on AR mRNA levels in either the axotomized or contrala(teral control FMN of gonadally intact males, relative to the nonaxotomized, gonadally intact male group. Corroborating our previous work, AR mRNA levels were reduced in the contralateral control FMN of gdx females, relative to the nonaxotomized, gonadally intact male group, with axotomy having no additional effects. The data are discussed in a mechanistic framework suggesting how TP acts to augment facial nerve regeneration.
High affinity testosterone (T)-specific and dihydrotestosterone (DHT)-specific binding sites exist in a 1:2 ratio in the cytosol fractions of the caput epididymidis, prostate, seminal vesicles and the ductus deferens of the rhesus monkey. The number of androgen-binding sites in the caput epididymis is 3 times greater than that of the other 3 tissues.
Accumulating evidence suggests that vasoactive intestinal peptide (VIP) may be a physiological PRL-releasing factor. In the present study, we examined a possible involvement of VIP in the neonatal androgenization (NA)-induced hyperprolactinemia. Twenty-four hours after birth, newborn female rats were injected sc with 1,000 micrograms of testosterone (NA) or with oil vehicle only (control). Both groups were sacrificed at 8 weeks of age. Compared to controls, NA rats showed significantly higher plasma PRL levels (7.3 fold), anterior pituitary (AP) PRL content (2.1 fold) and plasma estradiol levels (2.1 fold). AP VIP content was extremely higher (61 fold) in NA rats than in controls. However, NA did not affect VIP content in the suprachiasmatic nucleus, paraventricular nucleus or median eminence. These results suggest that the NA-induced hyperprolactinemia may be mediated, at least in part, by paracrine and/or autocrine effects of the increased AP VIP on PRL secretion. However, since the potentiation by NA of the AP VIP content was extremely marked compared to those of the other parameters, the possibility was also raised that the increased AP VIP may be involved in other endocrine and/or nonendocrine events occurring in the AP.
The plasma concentrations of total testosterone, free testosterone index, androstenedione, 17 beta-estradiol, luteinizing hormone, follicle-stimulating hormone, prolactin, and urinary 17-ketosteroid and 17-ketogenic steroid excretion were measured in 48 nonhirsute and 119 hirsute patients. Hormone data were compared within and between groups according to whether the menstrual cycles were eumenorrheic, amenorrheic, or oligomenorrheic. Eleven hirsute women treated with prednisone were followed for 6 months. It was concluded that: (1) androstenedione, testosterone, free testosterone index, and adrenal androgens alone or in combination play a role in the pathogenesis of the hirsutism observed in eumenorrheic women and in the amenorrhea and oligomenorrhea of both hirsute and nonhirsute women; (2) body weight correlated with adrenal adrogens (17-ketosteroids) in nonhirsute women and with androstenedione in hirsute women; (3) prednisone significantly suppressed androstenedione and 17-ketosteroids (p less than 0.05), with a decline of testosterone to 65% and luteinizing hormone to 51% of pretreatment values, with favorable clinical effects on the hirsutism, menstrual dysfunction, and infertility; (4) concentrations of 17 beta-estradiol were lower in amenorrheic than in eumenorrheic and oligomenorrheic women of both groups.
The comparison of normal and androgen receptor (AR) deficient Tfm-mice allows distinction between AR mediated and estrogen receptor (ER) mediated effects of testosterone (T)--the latter after aromatization of T to estrogens--on serum and pituitary FSH. Normal male and female as well as Tfm mice were gonadectomized after 8 days and treated for 11 days with either T, estradiol (E2) or vehicle. Serum and pituitary FSH was determined by RIA for rat FSH. In Tfm mice T caused a suppression of serum FSH, indicating an ER mediated effect. Lower serum FSH levels after T in normal mice than Tfm mice indicate an additional AR mediated suppression. Lower serum FSH values in E2 treated Tfm than in T treated Tfm mice--where T acts only through ER--suggest two classes of estrophilic cells: one which aromatizes, thus being susceptible for both T and E2, and the other which does not aromatize. Only AR but not ER mediated T effects on pituitary FSH could be demonstrated.
BACKGROUND: Estrogen-receptor (ER)-, progesterone-receptor (PR)-, and androgen-receptor (AR)-negative breast cancer cells are unaffected by treatment with dehydroepiandrosterone-sulfate (DHEAS) and an aromatase inhibitor (AI). We hypothesized that cell growth would be inhibited with DHEAS/AI treatment after successful transfection of an AR expression vector. METHODS: ER/PR/AR-negative breast cancer cells were transfected with an AR expression vector and treated with DHEAS/AI for 2 days. Growth inhibition of these cells was compared with that of transfected cells treated with only AI or with nontransfected cells treated with DHEAS/AI. Mann-Whitney U test was used to determine statistical significance. RESULTS: Cell death rates of 53.5% (P = .001) and 40.1% (P = .006) were seen in transfected cells treated with DHEAS/AI compared with controls for days 1 and 2, respectively. Nontransfected cells were unaffected by treatment. COMMENTS: ER/PR/AR-negative cells transfected with AR were killed by DHEAS/AI treatment, providing evidence that AR is responsible for this effect. This provides the first AR-targeted hormonal therapy for ER breast cancer.
OBJECTIVES: To explore whether less than 120 days of an antiandrogen plus a luteinizing hormone-releasing hormone agonist resulted in a different survival outcome than 120 days or more of combined treatment in patients with Stage D2 prostate cancer. METHODS: Survival data were available from a previously published controlled trial that had evaluated the efficacy and tolerability of two antiandrogens, bicalutamide and flutamide, each combined with a monthly depot preparation of leuprolide or goserelin, in 813 patients with Stage D2 prostate cancer. Cox's proportional hazards regression model assessed the relative effects of the length of combined androgen blockade (CAB) therapy on survival. This analysis was repeated in the subset of patients who lived at least 2 years beyond the date of randomization. Data were obtained at a median follow-up of 160 weeks. RESULTS: A survival benefit was demonstrated for patients receiving prolonged CAB therapy, with a hazard ratio of 0.275 (95% confidence interval 0.213 to 0.355, P = 0.0001) in favor of patients who received 120 days or more of CAB therapy (median survival 1035 days versus 302 days for less than 120 days of therapy). This result was confirmed in the patients who lived at least 2 years, in whom the median survival time was increased by 35%. The hazard ratio for 120 days or more of CAB therapy versus less than 120 days was 0.415 (95% confidence interval 0.246 to 0.702, P = 0.001). CONCLUSIONS: The results of the present exploratory analysis suggest that prolonged (120 days or more) antiandrogen treatment as part of CAB therapy may result in a better survival outcome.
The androgen receptor (AR) is a ligand-dependent transcription activator responsible for male sexual development. In order to specifically inhibit the AR pathway, dominant negative ARs were constructed by inactivation of the major transactivation domains of the wild type AR and fusing this mutant (AR122) to the Krüppel-associated box (KRAB) repressor domain and/or histone deacetylase (HDAC1). The HDAC1-KRAB-AR122 protein was the most successful dominant negative AR, capable of repressing the wild type AR ninefold when co-expressed at a 1:1 plasmid ratio. A maximal repression of 41-fold was achieved when HDAC1-KRAB-AR122 was cotransfected with the wild type AR at a 4:1 plasmid ratio. HDAC1-KRAB-AR122 repressed transcription in a ligand-dependent manner since it inhibited a constitutively active AR mutant (AR5) only in the presence of agonists. High concentrations of partial agonists such as RU486, cyproterone acetate, and estradiol were also capable of triggering repression by HDAC1-KRAB-AR122. The potent dominant negative AR proteins might prove useful tools to inhibit AR function in vitro and in vivo.
Translation of androgen receptor (AR) cRNA in a reticulocyte lysate and subsequent analysis of the translation products by SDS/PAGE showed a protein with an apparent molecular mass of 108 kDa. Scatchard-plot analysis revealed a single binding component with high affinity for R1881 (Kd = 0.3 nM). All AR molecules synthesized specifically bound steroid. No evidence for AR phosphorylation during in vitro synthesis was found. When AR was labelled with [3H]R1881 and analysed on sucrose-density gradients, a complex of approx. 6 S was observed. The complex was shifted to a higher sedimentation coefficient after incubation with a monoclonal AR antibody directed against an epitope in the DNA-binding domain. In the presence as well as the absence of hormone, AR molecules were able to bind to DNA-cellulose without an activation step. Gel retardation assays revealed that the AR forms complexes with a DNA element containing glucocorticoid-responsive element/androgen-responsive element sequences. Receptor-DNA interactions were stabilized by different polyclonal antibodies directed against either the N- or C-terminal part of the AR and were abolished by an antibody directed against the DNA-binding domain of the receptor. In conclusion, translation of AR cRNA in vitro yields an activated AR protein which binds steroid with high affinity. It is proposed that AR antibodies enhance AR-DNA binding by stabilizing AR dimers when bound to DNA.
The androgen receptor (AR), like other steroid receptors, modulates the activity of the general transcription machinery on the core promoter to exert its function as a regulator. Co-immunoprecipitation of prostate cancer LNCaP cell extract using protein A-Sepharose coupled with anti-AR antibody indicates that the AR interacts with the general transcription factor TFIIH in a physiological condition. Co-transfection of cdk activating kinase (CAK), the kinase moiety of TFIIH, enhanced AR-mediated transcription in a ligand-dependent manner in human prostate cancer PC-3 and LNCaP cells, and in a ligand-independent manner in human prostate cancer DU145 cells. Detailed interaction studies further revealed that the AR NH(2)-terminal domain interacting with CAK was essential for the CAK-induced AR transactivation. Together, our data suggest that the AR may interact with TFIIH for efficient communication with the general transcription factors/RNA polymerase II on the core promoter.
The androgen receptor (AR) has been shown to be modified by SUMO-1, a ubiquitin-like protein. Recently we showed that PIAS family proteins function as SUMO-E3 ligases. Here we provide evidence that PIAS1 and PIASxalpha act as specific SUMO-E3 ligases for the AR. PIAS1 and PIASxalpha but not PIAS3 or PIASxbeta enhanced the sumoylation of AR in intact cells and in vitro. PIAS1 and PIASxalpha bound Ubc9, the E2 enzyme for SUMO-1, in a RING finger-like domain-dependent manner. Consistent with previous studies (Kahyo, T., Nishida, T., and Yasuda, H. (2001) Mol. Cell 8, 713-718), the RING finger-like domain of the SUMO-E3 was required for ligase activity. The binding of a ligand, e.g. testosterone, to the AR was required for the sumoylation of AR in intact cells. Although AR-dependent transcription was enhanced by PIAS proteins without sumoylation of the receptor, PIAS1 and PIASxalpha repressed AR-dependent transcription in a manner dependent on the ectopic expression of SUMO-1 and their RING finger-like domain. Furthermore, the sumoylation sites of the AR were necessary for the full repressive effect on AR-dependent transactivation, indicating that the sumoylation of AR was crucial for the repression of transactivation of the AR. Thus, PIAS1 and PIASxalpha modulate the AR-dependent transactivation, which, at least in part, can be attributed to their SUMO-E3 activity toward AR.
Nuclear receptors, including the androgen receptor (AR), regulate target cell transcription through interaction with auxiliary proteins to modify chromatin structure. We describe herein a novel AR-interacting protein, termed ARIP4, that has structural features typical of the SNF2-like protein family. With regard to the Snf2 domain, the closest homolog of ARIP4 is the ATRX protein. ARIP4 is a nuclear protein and comprises 1466 amino acids. It interacts with AR in vitro and in cultured yeast and mammalian cells. ARIP4 can be labeled with 8-azido-[gamma-32P]ATP and exhibits DNA-dependent ATPase activity. Like several ATP-dependent chromatin remodeling proteins, ARIP4 generates superhelical torsion within linear DNA fragments in an ATP-dependent manner. With a stably integrated target promoter, ARIP4 elicits a modest enhancement of AR-dependent transactivation. In transient cotransfection assays, ARIP4 modulates AR function in a promoter-dependent manner; it enhances receptor activity on minimal promoters, but does not activate more complex promoters. ARIP4 mutants devoid of ATPase activity fail to alter DNA topology and behave as trans-dominant negative regulators of AR function in transient assays.
Androgen receptor (AR) activity is required for prostate cancer development and progression. Thus, there is a major impetus to understand the regulation of AR action. We and others have previously shown that AR transactivation potential is dependent on the presence of an active SWI/SNF chromatin remodeling complex. However, the mechanisms underlying SWI/SNF regulation of the AR remained unsolved. We show here that the BAF57 subunit, an accessory component of the remodeling complex, is a critical regulator of AR function. We show that BAF57 is expressed in the luminal epithelia of the prostate and is required for AR-dependent transactivation in prostatic adenocarcinoma cells. Our data reveal that BAF57 can directly bind to the AR and is recruited to endogenous AR targets upon ligand activation. Loss of BAF57 or inhibition of BAF57 function severely compromised AR activity, as observed with both exogenous and endogenous AR targets. Rescue of BAF57 function restored AR activity, thus demonstrating a specific requirement of BAF57 for AR activity. This action of BAF57 proved to be dependent on SWI/SNF ATPase function. BAF57 has previously been implicated in nuclear receptor coactivator function, and we show that, although BAF57 facilitated coactivator activity, only a selected subset required BAF57 for coactivator function. Lastly, we demonstrate that both BAF57 and BRM are required for the proliferation of AR-dependent prostatic adenocarcinoma cells. In summary, these findings identify BAF57 as a critical modulator of the AR that is capable of altering AR activity, coactivator function, and AR-dependent proliferation.
The amino terminus region of the androgen receptor (AR) gene in the X chromosome involves the cytosine, adenine, and guanine (CAG) repeats. Random X chromosome inactivation with AR alleles in individual cells occurs in females. Therefore, probably either paternal or maternal single dominant polymorphic AR mRNA must be expressed in neoplastic tissue originating from monoclone. This prompted us to determine the deviated numbers of CAG repeats in AR mRNA to understand the clonality of uterine leiomyoma. A solitary node of leiomyoma was macroscopically found in 7 cases, and multiple nodes were found in another 23 cases. Homozygous CAG repeats (22.0 +/- 2.3) in AR alleles were found in 5 of 30 cases, and either a large or small size of AR mRNA expression, were found in individual nodes of uterine leiomyoma, although paternal and maternal AR mRNAs from normal uterine myometrium were consistently expressed as AR alleles. There was no significant specificity in activated AR alleles related to CAG numbers in individual nodes. Therefore, an individual node of uterine leiomyoma might be formed from an independent monoclonal uterine leiomyoma cell.
PURPOSE: To evaluate the toxicity and efficacy of individualized neoadjuvant androgen deprivation (AD) to maximal response followed by external beam radiotherapy (RT) with continued AD for a total of 9 months in a prospective phase II trial. PATIENTS AND METHODS: One hundred twenty-three patients received a total of 9 months of flutamide and luprolide combined with RT. RT initiation was individualized to begin after maximum response to AD as assessed by monthly digital rectal examination and prostate-specific antigen (PSA). The neoadjuvant phase was restricted to no more than 6 months. RESULTS: Median time to initiation of RT was 4.7 months. Indications to begin RT (and their rates) were undetectable PSA (28%), PSA unchanged from one month to the next (46%), PSA rising from one month to the next (10%), 6 months of AD (14%), and other (2%). Five-year outcomes were biochemical disease-free survival, (DFS) 63% +/- 7%; clinical DFS, 75% +/- 5%; cancer-specific survival, 99% +/- 1%; and overall survival, 89% +/- 3%. Patients initiating RT after 6 months of AD had significantly lower biochemical and clinical DFS. Those patients whose testosterone recovered to normal after completion of AD had a significantly superior survival rate. Of those patients potent before treatment, 65% remained so at last follow-up. CONCLUSION: The combination of 9 months of AD and RT, with initiation of RT individualized on the basis of maximum response to AD, achieves disease control rates comparable with past studies, while preserving potency in many patients. Further studies are warranted to determine the optimal combination of AD and RT in this patient population.