Glucocorticoids can promote androgen-independent growth of prostate cancer cells through a mutated androgen receptor

The androgen receptor (AR) is involved in the development, growth and progression of prostate cancer (CaP). CaP often progresses from an androgen-dependent to an androgen-independent tumor, making androgen ablation therapy ineffective. However, the mechanisms for the development of androgen-independent CaP are unclear. More than 80% of clinically androgen-independent prostate tumors show high levels of AR expression. In some CaPs, AR levels are increased because of gene amplification and/or overexpression, whereas in others, the AR is mutated. Nonetheless, the involvement of the AR in the transition of CaP to androgen-independent growth and the subsequent failure of endocrine therapy are not fully understood. Here we show that in CaP cells from a patient who failed androgen ablation therapy, a doubly mutated AR functioned as a high-affinity cortisol/cortisone receptor (ARccr). Cortisol, the main circulating glucocorticoid, and its metabolite, cortisone, both equally stimulate the growth of these CaP cells and increase the secretion of prostate-specific antigen in the absence of androgens. The physiological concentrations of free cortisol and total cortisone in men greatly exceed the binding affinity of the ARccr and would activate the receptor, promoting CaP cell proliferation. Our data demonstrate a previously unknown mechanism for the androgen-independent growth of advanced CaP. Understanding this mechanism and recognizing the presence of glucocorticoid-responsive AR mutants are important for the development of new forms of therapy for the treatment of this subset of CaP.     

Quantifying the Evidence for the Risk of Metabolic Syndrome and Its Components following Androgen Deprivation Therapy for Prostate Cancer: A Meta-Analysis

Background

No meta-analysis is yet available for the risk of metabolic syndrome (MetS) following androgen deprivation therapy (ADT) for men with prostate cancer. To summarize the evidence for the link between ADT and MetS or its components quantitatively with a meta-analysis including all studies published to date.

Methods

PubMed and Embase were searched using predefined inclusion criteria to perform meta-analyses on the association between metabolic syndrome, hyperglycemia, diabetes, hypertension, dyslipidemia or obesity and androgen deprivation therapy in patients with prostate cancer. Random effects methods were used to estimate pooled relative risks (RRs) and 95% confidence intervals (CI).

Results

A total of nine studies was included. There was a positive association between ADT and risk of MetS (RR: 1.75 (95% CI: 1.27–2.41)). Diabetes was the only MetS component present in more than 3 studies, and also showed an increased risk following ADT (RR: 1.36 (95% CI: 1.17–1.58)).

Conclusion

This is the first quantitative summary addressing the potential risk of MetS following ADT in men with PCa. The positive RRs indicate that there is a need to further elucidate how type and duration of ADT affect these increased risks of MetS and diabetes as the number of men with PCa treated with ADT is increasing.     

Dominant-negative androgen receptor inhibition of intracrine androgen-dependent growth of castration-recurrent prostate cancer

Background

Prostate cancer (CaP) is the second leading cause of cancer death in American men. Androgen deprivation therapy is initially effective in CaP treatment, but CaP recurs despite castrate levels of circulating androgen. Continued expression of the androgen receptor (AR) and its ligands has been linked to castration-recurrent CaP growth.

Principal Finding

In this report, the ligand-dependent dominant-negative ARΔ142–337 (ARΔTR) was expressed in castration-recurrent CWR-R1 cell and tumor models to elucidate the role of AR signaling. Expression of ARΔTR decreased CWR-R1 tumor growth in the presence and absence of exogenous testosterone (T) and improved survival in the presence of exogenous T. There was evidence for negative selection of ARΔTR transgene in T-treated mice. Mass spectrometry revealed castration-recurrent CaP dihydrotestosterone (DHT) levels sufficient to activate AR and ARΔTR. In the absence of exogenous testosterone, CWR-R1-ARΔTR and control cells exhibited altered androgen profiles that implicated epithelial CaP cells as a source of intratumoral AR ligands.

Conclusion

The study provides in vivo evidence that activation of AR signaling by intratumoral AR ligands is required for castration-recurrent CaP growth and that epithelial CaP cells produce sufficient active androgens for CaP recurrence during androgen deprivation therapy. Targeting intracrine T and DHT synthesis should provide a mechanism to inhibit AR and growth of castration-recurrent CaP.     

前列腺癌雄激素受体和PI3K/Akt 信号通路相互作用研究进展

前列腺癌的发生、进展依赖于雄激素,因此去势手术成为治疗晚期前列腺癌的标准疗法。但是去势后大多前列腺癌最终将转化为雄激素非依赖性前列腺癌,甚至进展为激素难治性前列腺癌,使得肿瘤的进展不受低水平雄激素的影响。即使如此,大多数激素非依赖性前列腺癌,依然阳性表达雄激素受体。因而雄激素受体在前列腺癌发生发展中起着重要作用。而PI3K/Akt信号通路能够通过维持细胞生存、抑制细胞凋亡、促进细胞代谢及血管生成等促进前列腺癌进展。本综述旨在总结前人研究,阐述雄激素受体和PI3K/Akt信号通路之间相互作用关系。研究表明Akt信号通路能够正性或者负性调控AR蛋白表达、蛋白的稳定性及其转录活性,从而维持细胞的生存、代谢。而AR即可以通过基因转录途径抑制Akt活化又能通过非转录基因途径激活Akt及其下游蛋白。因此,AR和Akt信号通路相互协同促进前列腺癌的发生及其向雄激素非依赖性前列腺癌进展。     

Somatostatin Derivative (smsDX) Targets Cellular Metabolism in Prostate Cancer Cells after Androgen Deprivation Therapy

Cancer cell metabolism responsive to androgen deprivation therapy (ADT) may be involved in the development and progression of prostate cancer and the ultimate failure of androgen-deprivation therapy. To investigate the metabolism regulation effects on androgen-independent growth of prostate cancer, an established LNCaP-s cell model that resembles the clinical scenario of castration-resistant prostate cancer (CRPC), was used in this current study. This cell line was cultured from androgen-sensitive LNCaP parental cells, in an androgen-reduced condition, resembling clinical androgen deprivation therapy. To assess the effects of smsDX on the invasiveness of prostate cancer cells we used wound healing assay and Matrigel™ invasion assay. We evaluated differentially expressed proteins of the parental LNCaP cells and LNCaP-s cells after ADT by means of two-dimensional gel electrophoresis (2-DE) followed by MALDI-TOF mass spectrometric analysis. The covered area in the wound and the number of cells invading through a Matrigel chamber were significantly smaller for cells treated with smsDX than they were for control cells treated with vehicle. 56 proteins were found differentially expressed in LNCaP-s cells compared to LNCaP cells, majority of them were down-regulated after ADT treatment. 104 proteins of LNCaP cells and 86 in LNCaP-s cells, separately, were found differentially expressed after treatment with smsDX, When we explored these protein functions within the website UniProtKB/Swiss-Prot, surprisingly, most of the proteins were found to be involved in the cellular metabolism and mitochondrial function regulation. LNCaP-s as potential metastatic androgen-independent cancer cells, its metabolism and mitochondrial functions could be altered by a new somatostatin derivative smsDX, the smsDX regulatory effects on metabolism in LNCaP-s deliver more therapeutic information with the treatment of CRPC.     

Selective targeting of bioengineered platelets to prostate cancer vasculature: new paradigm for therapeutic modalities

Androgen deprivation therapy (ADT) provides palliation for most patients with advanced prostate cancer (CaP); however, greater than 80% subsequently fail ADT. ADT has been indicated to induce an acute but transient destabilization of the prostate vasculature in animal models and humans. Human re‐hydrated lyophilized platelets (hRL‐P) were investigated as a prototype for therapeutic agents designed to target selectively the tumour‐associated vasculature in CaP. The ability of hRL‐P to bind the perturbed endothelial cells was tested using thrombin‐ and ADP‐activated human umbilical vein endothelial cells (HUVEC), as well as primary xenografts of human prostate tissue undergoing acute vascular involution in response to ADT. hRL‐P adhered to activated HUVEC in a dose‐responsive manner. Systemically administered hRL‐P, and hRL‐P loaded with super‐paramagnetic iron oxide (SPIO) nanoparticles, selectively targeted the ADT‐damaged human microvasculature in primary xenografts of human prostate tissue. This study demonstrated that hRL‐P pre‐loaded with chemo‐therapeutics or nanoparticles could provide a new paradigm for therapeutic modalities to prevent the rebound/increase in prostate vasculature after ADT, inhibiting the transition to castration‐recurrent growth.     

Prostate cancer: Re-focusing on androgen receptor signaling

Prostate cancer is the most common, non-dermatologic cancer in men. Since prostate cancer is highly associated with increased age, the incidence of this disease is expected to increase as the population ages. In its initial stages prostate cancer depends upon the actions of androgen, and androgen deprivation therapy induces tumor regression. Currently, androgen deprivation is achieved by either surgical or chemical androgen blockade. Unfortunately, nearly all prostate cancer patients develop tumors that grow despite androgen blockade and ultimately relapse. Many alterations in prostate cancer cells contribute to this state. Although chemotherapy induces short remissions in some patients, there are no curative therapies for metastatic disease. This review summarizes our current understanding in androgen signaling and the mechanisms that allow tumor cells to bypass androgen manipulation therapy. The identification of novel survival pathways and effector molecules that drive androgen independent growth is necessary to develop effective therapies for advanced prostate cancers.     

Absence of nuclear receptors LXRs impairs immune response to androgen deprivation and leads to prostate neoplasia

Chronic inflammation is now a well-known precursor for cancer development. Infectious prostatitis are the most common causes of prostate inflammation, but emerging evidence points the role of metabolic disorders as a potential source of cancer-related inflammation. Although the widely used treatment for prostate cancer based on androgen deprivation therapy (ADT) effectively decreases tumor size, it also causes profound alterations in immune tumor microenvironment within the prostate. Here, we demonstrate that prostates of a mouse model invalidated for nuclear receptors liver X receptors (LXRs), crucial lipid metabolism and inflammation integrators, respond in an unexpected way to androgen deprivation. Indeed, we observed profound alterations in immune cells composition, which was associated with chronic inflammation of the prostate. This was explained by the recruitment of phagocytosis-deficient macrophages leading to aberrant hyporesponse to castration. This phenotypic alteration was sufficient to allow prostatic neoplasia. Altogether, these data suggest that ADT and inflammation resulting from metabolic alterations interact to promote aberrant proliferation of epithelial prostate cells and development of neoplasia. This raises the question of the benefit of ADT for patients with metabolic disorders.

Mice lacking the liver X nuclear receptors (LXRs), crucial integrators of lipid metabolism, were used to study the response of the prostate to androgen deprivation. This reveals that lack of androgens leads to chronic inflammation due to impaired clearance of castration-induced apoptotic cells, allowing production of pro-inflammatory cytokines and promoting prostate neoplasia.     

Estrogenic side effects of androgen deprivation therapy

Androgen deprivation therapy (ADT) is part of standard therapy for locally advanced or metastatic prostate cancer and is frequently used in men with a rising prostate-specific antigen following radical prostatectomy or radiation therapy. In some men, ADT may be administered for years or even decades. The intended therapeutic effect of ADT is testosterone deficiency. Because estrogen is a normal metabolite of testosterone, ADT also results in estrogen deficiency. ADT has a variety of adverse effects, many of which are primarily related to estrogen deficiency. Bone mineral density may decrease by 4% to 13% per year in men receiving ADT. The fracture rate for patients on ADT averages 5% to 8% per year of therapy. Hot flashes, gynecomastia, and breast tenderness are common side effects associated with ADT. In the clinic, minimum baseline testing should include weight measurement, blood pressure reading, and fasting lipid panel and serum glucose tests. Currently, there are no large outcome trials in men on ADT testing the available therapies for adverse effects. No therapies are specifically approved for treatment of adverse effects in men on ADT. Although some therapies can be used for a single indication (based upon small studies), there is currently no agent to treat the multiple estrogenic side effects of ADT.     

前列腺癌雄激素受体和PI3K/Akt信号通路相互作用研究进展

前列腺癌的发生、进展依赖于雄激素,因此去势手术成为治疗晚期前列腺癌的标准疗法。但是去势后大多前列腺癌最终将转化为雄激素非依赖性前列腺癌,甚至进展为激素难治性前列腺癌,使得肿瘤的进展不受低水平雄激素的影响。即使如此,大多数激素非依赖性前列腺癌,依然阳性表达雄激素受体。因而雄激素受体在前列腺癌发生发展中起着重要作用。而PI3K/Akt信号通路能够通过维持细胞生存、抑制细胞凋亡、促进细胞代谢及血管生成等促进前列腺癌进展。本综述旨在总结前人研究,阐述雄激素受体和PI3K/Akt信号通路之间相互作用关系。研究表明Akt信号通路能够正性或者负性调控AR蛋白表达、蛋白的稳定性及其转录活性,从而维持细胞的生存、代谢。而AR即可以通过基因转录途径抑制Akt活化又能通过非转录基因途径激活Akt及其下游蛋白。因此,AR和Akt信号通路相互协同促进前列腺癌的发生及其向雄激素非依赖性前列腺癌进展。     

Epithelial cell adhesion molecule (EpCAM) is associated with prostate cancer metastasis and chemo/radioresistance via the PI3K/Akt/mTOR signaling pathway

Prostate cancer (CaP) is the second leading malignancy in men. The role of epithelial cell adhesion molecule (EpCAM), also known as CD326, in CaP progression and therapeutic resistance is still uncertain. Here, we aimed to investigate the roles of EpCAM in CaP metastasis and chemo/radioresistance. Expression of EpCAM in CaP cell lines and human CaP tissues was assessed using immunofluorescence and immunohistochemistry, respectively. EpCAM was knocked down (KD) in PC-3, DU145 and LNCaP-C4-2B cells using small interfering RNA (siRNA), and KD results were confirmed by confocal microscope, Western blotting and quantitative real time polymerase chain reaction (qRT-PCR). Cell growth was evaluated by proliferation and colony formation assays. The invasive potential was assessed using a matrigel chamber assay. Tumorigenesis potential was measured by a sphere formation assay. Chemo-/radiosensitivity were measured using a colony formation assay. Over-expression of EpCAM was found in primary CaP tissues and lymph node metastases including cancer cells and surrounding stromal cells. KD of EpCAM suppressed CaP proliferation and invasive ability, reduced sphere formation, enhanced chemo-/radiosensitivity, and down-regulated E-cadherin, p-Akt, p-mTOR, p-4EBP1 and p-S6K expression in CaP cells. Our findings suggest that EpCAM plays an important role in CaP proliferation, invasion, metastasis and chemo-/radioresistance associated with the activation of the PI3K/Akt/mTOR signaling pathway and is a novel therapeutic target to sensitize CaP cells to chemo-/radiotherapy.     

Androgen Receptor as a Driver of Therapeutic Resistance in Advanced Prostate Cancer

The role of the androgen receptor (AR) signaling axis in the progression of prostate cancer is a cornerstone to our understanding of the molecular mechanisms causing castration-resistant prostate cancer (CRPC). Resistance of advanced prostate cancer to available treatment options makes it a clinical challenge that results in approximately 30,000 deaths of American men every year. Since the historic discovery by Dr. Huggins more than 70 years ago, androgen deprivation therapy (ADT) has been the principal treatment for advanced prostate cancer. Initially, ADT induces apoptosis of androgen-dependent prostate cancer epithelial cells and regression of androgen-dependent tumors. However, the majority of patients with advanced prostate cancer progress and become refractory to ADT due to emergence of androgen-independent prostate cancer cells driven by aberrant AR activation. Microtubule-targeting agents such as taxanes, docetaxel and paclitaxel, have enjoyed success in the treatment of metastatic prostate cancer; although new, recently designed mitosis-specific agents, such as the polo-kinase and kinesin-inhibitors, have yielded clinically disappointing results. Docetaxel, as a first-line chemotherapy, improves prostate cancer patient survival by months, but tumor resistance to these therapeutic agents inevitably develops. On a molecular level, progression to CRPC is characterized by aberrant AR expression, de novo intraprostatic androgen production, and cross talk with other oncogenic pathways. Emerging evidence suggests that reactivation of epithelial-mesenchymal-transition (EMT) processes may facilitate the development of not only prostate cancer but also prostate cancer metastases. EMT is characterized by gain of mesenchymal characteristics and invasiveness accompanied by loss of cell polarity, with an increasing number of studies focusing on the direct involvement of androgen-AR signaling axis in EMT, tumor progression, and therapeutic resistance. In this article, we discuss the current knowledge of mechanisms via which the AR signaling drives therapeutic resistance in prostate cancer metastatic progression and the novel therapeutic interventions targeting AR in CRPC.     

AT‐101 (R‐(−)‐gossypol acetic acid) enhances the effectiveness of androgen deprivation therapy in the VCaP prostate cancer model

Prostate cancer remains a leading cause of cancer death in American men. Androgen deprivation therapy (ADT) is the most common treatment for advanced prostate cancer patients; however, ADT fails in nearly all cases resulting in castration resistant or androgen‐insensitive (AI) disease. In many cases, this progression results from dysregulation of the pro‐survival Bcl‐2 family proteins. Inhibition of pro‐survival Bcl‐2 family proteins, therefore, may be an effective strategy to delay the onset of AI disease. Gossypol, a small molecule inhibitor of pro‐survival Bcl‐2 family proteins, has been demonstrated to inhibit AI prostate cancer growth. The apoptotic effect of gossypol, however, has been demonstrated to be attenuated by the presence of androgen in a prostate cancer xenograft mouse model (Vertebral Cancer of Prostate [VCaP]) treated with AT‐101 (R‐(?)‐gossypol acetic acid). This study was undertaken to better understand the in vitro effects of androgen receptor (AR) on AT‐101‐induced apoptosis. VCaP cells treated with AT‐101 demonstrated an increase in apoptosis and downregulation of Bcl‐2 pro‐survival proteins. Upon AR activation in combination with AT‐101 treatment, apoptosis is reduced, cell survival increases, and caspase activation is attenuated. Akt and X inhibitor of apoptosis (XIAP) are downregulated in the presence of AT‐101, and AR stimulation rescues protein expression. Combination treatment of bicalutamide and AT‐101 increases apoptosis by reducing the expression of these pro‐survival proteins. These data suggest that combination therapy of AT‐101 and ADT may further delay the onset of AI disease, resulting in prolonged progression‐free survival of prostate cancer patients. J. Cell. Biochem. 110: 1187–1194, 2010. Published 2010 Wiley‐Liss, Inc.     

Survival and clinical metastases among prostate cancer patients treated with androgen deprivation therapy in Sweden

ObjectivesTo examine the incidence of metastases and clinical course of prostate cancer patients who are without confirmed metastasis when initiating androgen deprivation therapy (ADT).MethodsRetrospective cohort study conducted using electronic medical records from Swedish outpatient urology clinics linked to national mandatory registries to capture medical and demographic data. Prostate cancer patients initiating ADT between 2000 and 2010 were followed from initiation of ADT to metastasis, death, and/or end of follow-up.ResultsThe 5-year cumulative incidence (CI) of metastasis was 18%. Survival was 60% after 5 years; results were similar for bone metastasis-free survival. The 5-year CI of castration-resistant prostate cancer (CRPC) was 50% and the median survival from CRPC development was 2.7 years. Serum prostate-specific antigen (PSA) levels and PSA doubling time were strong predictors of bone metastasis, any metastasis, and death.ConclusionThis study provides understanding of the clinical course of prostate cancer patients without confirmed metastasis treated with ADT in Sweden. Greater PSA values and shorter PSA doubling time (particularly ≤ 6 months) were associated with increased risk of bone metastasis, any metastasis, and death.     

Inactivation by UDP-glucuronosyltransferase enzymes: the end of androgen signaling

Conjugation by UDP-Glucuronosyltransferase (UGT) is the major pathway of androgen metabolism and elimination in the human. High concentrations of glucuronide conjugates of androsterone (ADT) and androstane-3alpha,17beta-diol (3alpha-diol) are present in circulation and several studies over the last 30 years have concluded that the serum levels of these metabolites might reflect the androgen metabolism in several tissues, including the liver and androgen target tissues. Three UGT2B enzymes are responsible for the conjugation of DHT and its metabolites ADT and 3alpha-diol: UGT2B7, B15 and B17. UGT2B7 is expressed in the liver and skin whereas UGT2B15 and B17 were found in the liver, prostate and skin. Very specific antibodies against each UGT2B enzyme have been obtained and used for immunohistochemical studies in the human prostate. It was shown that UGT2B17 is expressed in basal cells whereas UGT2B15 is only localized in luminal cells, where it inactivates DHT. By using LNCaP cells, we have also demonstrated that the expression and activity of UGT2B15 and B17 are modulated by several endogenous prostate factors including androgen. Finally, to study the physiological role of UGT2B enzymes, transgenic mice bearing the human UGT2B15 gene were recently obtained. A decrease in reproductive tissue weight from transgenic animals compared to those from control animals was observed. In conclusion, the conjugation by UGT2B7, B15 and B17, which represents a non-reversible step in androgen metabolism, is an important means by which androgens are regulated locally. It is also postulated that UGT enzymes protect the tissue from deleteriously high concentrations of active androgen.     

Effect of castration monotherapy on the levels of adrenal androgens in cancerous prostatic tissues

The mechanism accounting for the development of castration-resistant prostate cancer (CRPC) remains unclear. Studies in CRPC tissues suggest that, after androgen deprivation therapy (ADT), the adrenal androgens may be an important source of testosterone (T) and 5-alpha dihydrotestosterone (DHT) in CRPC tissues. To clarify the role of adrenal androgens in the prostatic tissues (prostatic tissue adrenal androgens) during ADT, we developed a high sensitive and specific quantification method for the levels of androgens in prostatic tissue using liquid chromatography-tandem mass spectrometry (LC-MS/MS). Human prostatic tissues were purified using mixed-mode reversed-phase, strong anion exchange Oasis cartridges (Oasis MAX). Analysis of steroids was performed using LC-MS/MS after picolinic acid derivatization. The validation tests showed that our method of quantitative analysis was precise and sensitive enough for the quantification of dehydroepiandrosterone (DHEA), androstenedione, androstenediol, T, and DHT in the prostatic tissue. The levels of adrenal androgens in prostate cancer tissues after ADT were similar to those in untreated PCa. Especially, DHEA was the most existing androgen precursor in PCa tissues after ADT. The levels of DHEA were high in PCa tissues, irrespective of ADT. We assumed that DHEA played a significant role in the synthesis of T and DHT in PCa tissues after ADT.     

Association of HPC2/ELAC2 genotypes and prostate cancer

HPC2/ELAC2 has been identified as a prostate cancer (CaP) susceptibility gene. Two common missense variants in HPC2/ELAC2 have been identified: a Ser-->Leu change at amino acid 217, and an Ala-->Thr change at amino acid 541. Tavtigian et al. reported that these variants were associated with CaP in a sample of men drawn from families with hereditary CaP. To confirm this report in a sample unselected for family history, we studied 359 incident CaP case subjects and 266 male control subjects that were frequency matched for age and race and were identified from a large health-system population. Among control subjects, the Thr541 frequency was 2.9%, and the Leu217 frequency was 31.6%, with no significant differences in frequency across racial groups. Thr541 was only observed in men who also carried Leu217. The probability of having CaP was increased in men who carried the Leu217/Thr541 variants (odds ratio = 2.37; 95% CI 1.06-5.29). This risk did not differ significantly by family history or race. Genotypes at HPC2/ELAC2 were estimated to cause 5% of CaP in the general population of inference. These results suggest that common variants at HPC2/ELAC2 are associated with CaP risk in a sample unselected for family history or other factors associated with CaP risk.