Cell proliferation and apoptosis in prostate tumors and adjacent non-malignant prostate tissue in patients at different time-points after castration treatment

Critical role of antioxidant programs in enzalutamide-resistant prostate cancer

Therapy resistance to second-generation androgen receptor (AR) antagonists, such as enzalutamide, is common in patients with advanced prostate cancer (PCa). To understand the metabolic alterations involved in enzalutamide resistance, we performed metabolomic, transcriptomic, and cistromic analyses of enzalutamide-sensitive and -resistant PCa cells, xenografts, patient-derived organoids, patient-derived explants, and tumors. We noted dramatically higher basal and inducible levels of reactive oxygen species (ROS) in enzalutamide-resistant PCa and castration-resistant PCa (CRPC), in comparison to enzalutamide-sensitive PCa cells or primary therapy-naive tumors respectively. Unbiased metabolomic evaluation identified that glutamine metabolism was consistently upregulated in enzalutamide-resistant PCa cells and CRPC tumors. Stable isotope tracing studies suggest that this enhanced glutamine metabolism drives an antioxidant program that allows these cells to tolerate higher basal levels of ROS. Inhibition of glutamine metabolism with either a small-molecule glutaminase inhibitor or genetic knockout of glutaminase enhanced ROS levels, and blocked the growth of enzalutamide-resistant PCa. The critical role of compensatory antioxidant pathways in maintaining enzalutamide-resistant PCa cells was validated by targeting another antioxidant program driver, ferredoxin 1. Taken together, our data identify a metabolic need to maintain antioxidant programs and a potentially targetable metabolic vulnerability in enzalutamide-resistant PCa.

Antagonistic Functions of Androgen Receptor and NF-κB in Prostate Cancer-Experimental and Computational Analyses

Prostate cancer is very frequent and is, in many countries, the third-leading cause of cancer related death in men. While early diagnosis and treatment by surgical removal is often curative, metastasizing prostate cancer has a very bad prognosis. Based on the androgen-dependence of prostate epithelial cells, the standard treatment is blockade of the androgen receptor (AR). However, nearly all patients suffer from a tumor relapse as the metastasizing cells become AR-independent. In our study we show a counter-regulatory link between AR and NF-κB both in human cells and in mouse models of prostate cancer, implying that inhibition of AR signaling results in induction of NF-κB-dependent inflammatory pathways, which may even foster the survival of metastasizing cells. This could be shown by reporter gene assays, DNA-binding measurements, and immune-fluorescence microscopy, and furthermore by a whole set of computational methods using a variety of datasets. Interestingly, loss of PTEN, a frequent genetic alteration in prostate cancer, also causes an upregulation of NF-κB and inflammatory activity. Finally, we present a mathematical model of a dynamic network between AR, NF-κB/IκB, PI3K/PTEN, and the oncogene c-Myc, which indicates that AR blockade may upregulate c-Myc together with NF-κB, and that combined anti-AR/anti-NF-κB and anti-PI3K treatment might be beneficial.

Prostate cancer cells demonstrate unique metabolism and substrate adaptability acutely after androgen deprivation therapy

BACKGROUND

Androgen deprivation therapy (ADT) has been the standard of care for advanced hormone-sensitive prostate cancer (PC), yet tumors invariably develop resistance resulting in castrate-resistant PC. The acute response of cancer cells to ADT includes apoptosis and cell death, but a large fraction remains arrested but viable. In this study, we focused on intensively characterizing the early metabolic changes that result after ADT to define potential metabolic targets for treatment.

METHODS

A combination of mass spectrometry, optical metabolic imaging which noninvasively measures drug responses in cells, oxygen consumption rate, and protein expression analysis was used to characterize and block metabolic pathways over several days in multiple PC cell lines with variable hormone response status including ADT sensitive lines LNCaP and VCaP, and resistant C4-2 and DU145.

RESULTS

Mass spectrometry analysis of LNCaP pre- and postexposure to ADT revealed an abundance of glycolytic intermediates after ADT. In LNCaP and VCaP, a reduction in the optical redox ratio [NAD(P)H/FAD], extracellular acidification rate, and a downregulation of key regulatory enzymes for fatty acid and glutamine utilization was acutely observed after ADT. Screening several metabolic inhibitors revealed that blocking fatty acid oxidation and synthesis reversed this stress response in the optical redox ratio seen with ADT alone in LNCaP and VCaP. In contrast, both cell lines demonstrated increased sensitivity to the glycolytic inhibitor 2-Deoxy- d-glucose(2-DG) and maintained sensitivity to electron transport chain inhibitor Malonate after ADT exposure. ADT followed by 2-DG results in synergistic cell death, a result not seen with simultaneous administration.

CONCLUSIONS

Hormone-sensitive PC cells displayed altered metabolic profiles early after ADT including an overall depression in energy metabolism, induction of a quiescent/senescent phenotype, and sensitivity to selected metabolic inhibitors. Glycolytic blocking agents (e.g., 2-DG) as a sequential treatment after ADT may be promising.

Androgens, aging, and prostate health

Due to late onset hypogonadism (LOH), there is an increased usage of testosterone replacement therapy (TRT) in the aging male population. Since prostate is a target organ for androgens and anti-androgenic strategies are used to treat and palliate benign prostate hyperplasia (BPH) and prostate cancer (PC), the prevalence of both increases with age, the possible influence of TRT on prostate health becomes highly relevant. The present review summarizes existing data on the associations between endogenous hormone concentrations and prostate growth and concludes that circulating concentrations of androgens do not appear to be associated with the risks of development of BPH or initiation or progression of PC. The explanation for these findings relates to an apparent insensitivity of prostatic tissue to changes of testosterone concentrations within the physiological range.

Targeting the Intrinsic Apoptosis Pathway: A Window of Opportunity for Prostate Cancer

Despite major improvements in the management of advanced prostate cancer over the last 20 years, the disease remains invariably fatal, and new effective therapies are required. The development of novel hormonal agents and taxane chemotherapy has improved outcomes, although primary and acquired resistance remains problematic. Inducing cancer cell death via apoptosis has long been an attractive goal in the treatment of cancer. Apoptosis, a form of regulated cell death, is a highly controlled process, split into two main pathways (intrinsic and extrinsic), and is stimulated by a multitude of factors, including cellular and genotoxic stress. Numerous therapeutic strategies targeting the intrinsic apoptosis pathway are in clinical development, and BH3 mimetics have shown promising efficacy for hematological malignancies. Utilizing these agents for solid malignancies has proved more challenging, though efforts are ongoing. Molecular characterization and the development of predictive biomarkers is likely to be critical for patient selection, by identifying tumors with a vulnerability in the intrinsic apoptosis pathway. This review provides an up-to-date overview of cell death and apoptosis, specifically focusing on the intrinsic pathway. It summarizes the latest approaches for targeting the intrinsic apoptosis pathway with BH3 mimetics and discusses how these strategies may be leveraged to treat prostate cancer.

Immune signature driven by ADT-induced immune microenvironment remodeling in prostate cancer is correlated with recurrence-free survival and immune infiltration

Androgen deprivation therapy (ADT) is a cornerstone treatment for locally advanced or metastatic prostate cancer (PCa). However, its potential effects on the tumor immune microenvironment (TIM) of PCa patients and the underlying mechanism remain largely unclear. To explore the effects of ADT on PCa TIM, RNA sequencing was performed on six paired pre-ADT biopsy and post-ADT PCa lesions, and five paired paracancerous benign tissues from patients receiving neoadjuvant ADT with locally advanced PCa. Bioinformatics methods including ESTIMATE and ssGSEA were used to evaluate the stromal immune score and immune cell infiltration in PCa and paracancerous tissues. Weighted correlation network analysis was used to screen hub genes in the ADT-induced immune remodeling process. The results showed differences exist between PCa and paracancerous tissues in response to ADT. Compared with paracancerous tissues, the immune remodeling effect of ADT in PCa was more intense. ZFP36, JUNB, and SOCS3 served as hub genes in the ADT-induced immune remodeling process and were associated with PSA recurrent-free survival in the TCGA and our neoadjuvant ADT cohort. To investigate the joint action of the above three hub genes, an immune signature score was constructed. The results showed that immune signature score-based immune subtypes reveal the heterogeneity of the immune microenvironment of PCa and showed significant differences in patient prognosis, tumor immune infiltration, mutation burden, and landscape.

Combination therapy with androgen deprivation for hormone sensitive prostate cancer: A new frontier

Androgen deprivation therapy (ADT) has been the standard of care for the last 75 years in metastatic hormone sensitive prostate cancer (PCa). However, this approach is rarely curative. Recent clinical trials have demonstrated that ADT combined with other agents, notably docetaxel and abiraterone, lead to improved survival. The mechanisms surrounding this improved cancer outcomes are incompletely defined. The response of cancer cells to ADT includes apoptosis and cell death, but a significant fraction remains viable. Our laboratory has demonstrated both in vitro and in vivo that cellular senescence occurs in a subset of these cells. Cellular senescence is a phenotype characterized by cell cycle arrest, senescence-associated β-galactosidase (SA-β-gal), and a hypermetabolic state. Positive features of cellular senescence include growth arrest and immune stimulation, although persistence may release cytokines and growth factors that are detrimental. Senescent tumor cells generate a catabolic state with increased glycolysis, protein turnover and other metabolic changes that represent targets for drugs, like metformin, to be applied in a synthetic lethal approach. This review examines the response to ADT and the putative role of cellular senescence as a biomarker and therapeutic target in this context.

Monitoring circulating prostate cancer cells by in vivo flow cytometry assesses androgen deprivation therapy on metastasis

It remains controversial whether surgical castration prolongs survival rate and improves therapy prospects in patients suffering from prostate cancer. We used PC3 cell line to establish prostate tumor models. In vivo flow cytometry and ultrasonic imaging were used to monitor the process of prostate cancer growth, development and metastasis. We found out that the number of circulating tumor cells (CTCs) in orthotopic tumor model was higher than that in subcutaneous tumor model. The CTC number in orthotopic tumor model was due to burst growth, while CTC number in subcutaneous tumor model showed a gradual increase with tumor size. After androgen deprivation therapy (ADT) through testicular extraction, we constructed GFP-PC3 subcutaneous tumor models and orthotopic tumor models. We found dramatically decreased CTC number, relieved symptoms caused by the tumor, and significantly prolonged survival time after testicular extraction in orthotopically transplanted prostate tumor model, while the carcinogenesis process and metastases were little influenced by ADT in subcutaneous tumor model. ADT treatment can restrict tumor growth, decrease the CTC number significantly and inhibit distant invasion through inhibition of tumor proliferation and tumor angiogenesis in orthotopical prostate tumor model. © 2018 International Society for Advancement of Cytometry.

Computer vision detects subtle histological effects of dutasteride on benign prostate

OBJECTIVE

To determine whether a computer vision-based approach applied to haematoxylin and eosin (H&E) prostate biopsy images can distinguish dutasteride-treated tissue from placebo, and identify features associated with degree of responsiveness to 5α-reductase inhibitor (5ARI) therapy.

SUBJECTS AND METHODS

Our study population comprised 100 treatment-adherent men without prostate cancer assigned to dutasteride or placebo in the REDUCE trial, who had slides available from mandatory year-4 biopsies. Half of the men also provided slides from a year-2 biopsy. We obtained 20× whole-slide images and used specialized software to generate a library of 1 300 epithelial and stromal features from objects comprising superpixels and several types of nuclei, including spatial relations among objects between and within each hierarchical level. We used penalized logistic regression and fivefold cross-validation to find optimal combinations of histological features in the year-4 biopsies. Feature data from the year-2 biopsies were fitted to a final model for independent validation. Two pathologists, blinded to treatment, scored each image for focal atrophy and histological features previously linked to 5AR1 treatment.

RESULTS

Consensus classification by pathologists obtained a discrimination accuracy equivalent to chance. A 21-feature computer vision model gave a cross-validation area under the curve of 0.97 (95% confidence interval [CI] 0.95-0.99) in the year-4 biopsies and 0.79 (95% CI: 0.65-0.92) in the set-aside year-2 biopsies. Histology scores were not correlated with change in prostate-specific antigen level, serum dihydrotestosterone level or gland volume. Key features associated with dutasteride treatment included greater shape and colour uniformity in stroma, irregular clustering of epithelial nuclei, and greater variation in lumen shape.

CONCLUSION

The present findings show that a computer vision approach can detect subtle histological effects attributable to dutasteride, resulting in a continuous measure of responsiveness to the drug that could eventually be used to predict individual patient response in the context of BPH treatment or cancer chemoprevention.

Intermediate PSA half-life after neoadjuvant hormone therapy predicts reduced risk of castration-resistant prostate cancer development after radical prostatectomy

Background

The magnitude and rapidity of the tumor response to androgen deprivation is known to predict the durability of the therapy. We have investigated the predictive value of categorizing patients by the half-life of PSA under neoadjuvant androgen deprivation therapy in patients with biochemical recurrence after radical prostatectomy.

Methods

Medical records of 317 patients who received neoadjuvant androgen deprivation therapy before radical prostatectomy and developed biochemical recurrence were analyzed. The patients were categorized into five groups according to PSA half-life. Risk of developing castration resistance was evaluated by Kaplan-Meier analysis and by Cox proportional risk regression analysis.

Results

The median follow-up duration was 50.1 months (IQR 31.8–68.7) and median PSA half-life was 22.1 days (IQR 12.7–38.4). Comparison of survival curves revealed that patients in the intermediate response group showed significantly lower 5-year castration-resistant prostate cancer rate (37.5%) compared to non-response and ultra-rapid response groups (63.6%, p = 0.007; 56.1%, p = 0.031; respectively). In the multivariate regression model, intermediate response compared to non-response was associated with significantly reduced risk of castration resistance development (hazard ratio 0.397, 95% confidence interval 0.191–0.823, p = 0.013) and overall mortality (hazard ratio 0.138, 95% confidence interval 0.033–0.584, p = 0.007). When subcategorized by Gleason score, Kaplan-Meier curve revealed that, in the high Gleason score stratum, 5-year castration-resistant prostate cancer rate for intermediate response group (44.0%) was exceptionally lower than that in non-response group (66.7%, p = 0.047), while castration resistance increased in other groups.

Conclusion

Short PSA half-life as well as no response after androgen deprivation is associated with increased risk of treatment failure compared to intermediate PSA half-life.

Electronic supplementary material

The online version of this article (10.1186/s12885-017-3775-6) contains supplementary material, which is available to authorized users.

Role of 20-Hydroxyeicosatetraenoic Acid (20-HETE) in Androgen-Mediated Cell Viability in Prostate Cancer Cells

20-Hydroxyeicosatetraenoic acid (20-HETE) is generated intracellularly through the ω-hydroxylation of arachidonic acid by the cytochrome P450 (in humans, CYP4A11 and CYP4F2). 20-HETE induces mitogenic responses in different cancer cells. The aim of this study was to analyze how 20-HETE impacts cell survival, proliferation, and apoptosis in prostate cancer cells. Incubation of the human androgen-sensitive cells (LNCaP) with 1-10 μM HET0016 (a selective inhibitor of 20-HETE synthesis) reduced cell viability by 49*-64%* (*p < 0.05 vs. control). This was explained by a reduction in cell proliferation (vehicle, 46 ± 3%; 1 μM, 23 ± 3%*; 10 μM, 28 ± 3%*) and by an increase in apoptosis (vehicle, 2.1 ± 0%; 1 μM, 16 ± 4%*; 10 μM, 31 ± 3%*). Furthermore, the increase in LNCaP cell viability induced by dihydrotestosterone (DHT, 0.1 nM) was abrogated by 30*-42%* by 1-10 μM HET0016. Incubation with 20-HETE (5-1000 nM) increased LNCaP cell viability up to 50%*, together with a 70%* reduction in apoptosis. PC-3 (androgen-insensitive) cell viability was not affected by either HET0016 or 20-HETE. In LNCaP cells, HET0016 (10 μM) diminished the expression of androgen receptors (AR): messenger RNA (mRNA) (40%*) and protein (50%*). DHT (10 nM) augmented CYP4F2 protein expression (1.9-fold*) and 20-HETE levels (50%*). Oppositely, enzalutamide (AR antagonist) reduced CYP4F2 mRNA and protein expressions by 30 and 25%, respectively. Thus, intracellular availability of 20-HETE is necessary to sustain LNCaP cell viability. 20-HETE may act as a signaling molecule in the pathways involved in LNCaP cell viability upon stimulation of the AR. This effect may be partially attributed to its role on securing normal AR expression levels that in turn contribute to maintain intracellular levels of 20-HETE.

Testosterone Replacement Therapy and Risk of Favorable and Aggressive Prostate Cancer

Purpose The association between exposure to testosterone replacement therapy (TRT) and prostate cancer risk is controversial. The objective was to examine this association through nationwide, population-based registry data. Methods We performed a nested case-control study in the National Prostate Cancer Register of Sweden, which includes all 38,570 prostate cancer cases diagnosed from 2009 to 2012, and 192,838 age-matched men free of prostate cancer. Multivariable conditional logistic regression was used to examine associations between TRT and risk of prostate cancer (overall, favorable, and aggressive). Results Two hundred eighty-four patients with prostate cancer (1%) and 1,378 control cases (1%) filled prescriptions for TRT. In multivariable analysis, no association was found between TRT and overall prostate cancer risk (odds ratio [OR], 1.03; 95% CI, 0.90 to 1.17). However, patients who received TRT had more favorable-risk prostate cancer (OR, 1.35; 95% CI, 1.16 to 1.56) and a lower risk of aggressive prostate cancer (OR, 0.50; 95% CI, 0.37 to 0.67). The increase in favorable-risk prostate cancer was already observed within the first year of TRT (OR, 1.61; 95% CI, 1.10 to 2.34), whereas the lower risk of aggressive disease was observed after > 1 year of TRT (OR, 0.44; 95% CI, 0.32 to 0.61). After adjusting for previous biopsy findings as an indicator of diagnostic activity, TRT remained significantly associated with more favorable-risk prostate cancer and lower risk of aggressive prostate cancer. Conclusion The early increase in favorable-risk prostate cancer among patients who received TRT suggests a detection bias, whereas the decrease in risk of aggressive prostate cancer is a novel finding that warrants further investigation.

Inhibition of the insulin-like growth factor-1 receptor potentiates acute effects of castration in a rat model for prostate cancer growth in bone

Prostate cancer (PCa) patients with bone metastases are primarily treated with androgen deprivation therapy (ADT). Less pronounced ADT effects are seen in metastases than in primary tumors. To test if acute effects of ADT was enhanced by concurrent inhibition of pro-survival insulin-like growth factor 1 (IGF-1), rats were inoculated with Dunning R3327-G tumor cells into the tibial bone marrow cavity and established tumors were treated with castration in combination with IGF-1 receptor (IGF-1R) inhibitor NVP-AEW541, or by each treatment alone. Dunning R3327-G cells were stimulated by androgens and IGF-1 in vitro. In rat tibia, Dunning R3327-G cells induced bone remodeling, identified through increased immunoreactivity of osteoblast and osteoclast markers. Tumor cells occasionally grew outside the tibia, and proliferation and apoptotic rates a few days after treatment were evaluated by scoring BrdU- and caspase-3-positive tumor cells inside and outside the bone marrow cavity, separately. Apoptosis was significantly induced outside, but unaffected inside, the tibial bone by either castration or NVP-AEW541, and the maximum increase (2.7-fold) was obtained by the combined treatment. Proliferation was significantly reduced by NVP-AEW541, independently of growth site, although the maximum decrease (24%) was observed when NVP-AEW541 was combined with castration. Tumor cell IGF-1R immunoreactivity was evaluated in clinical PCa bone metastases (n = 61), and positive staining was observed in most cases (74%). In conclusion, IGF-1R inhibition may be evaluated in combination with ADT in patients with metastatic PCa, or in combination with therapies for the subsequent development of castration-resistant disease, although diverse responses could be anticipated depending on metastasis site.

Oestrogens and oestrogen receptors in prostate cancer

The role of androgens in prostate cancer is obvious due to the fact that androgen signalling is the main regulator of prostate growth and function. Androgen deprivation therapy is a mainstay treatment for advanced prostate cancer. However, prostate cancer often becomes androgen-independent, which in consequence leads to lethal and incurable disease. In addition, oestrogens play a crucial role in prostate cancer, especially in elder men in whom the overall ratio of oestrogens to androgens is increasing. This review summarizes the current knowledge on molecular mechanisms through which oestrogens are involved in prostate cancer development. We focused on commonly alternated molecular signalling pathways contributing to tumourgenesis in prostate cancer.

Androgen deprivation in LNCaP prostate tumour xenografts induces vascular changes and hypoxic stress, resulting in promotion of epithelial-to-mesenchymal transition

Background:

When single-agent androgen deprivation therapy (ADT) is administered for locally advanced prostate cancer, men usually relapse within 1–2 years with more malignant castrate-resistant disease. The reason for this is currently unknown. We now hypothesise that an initial treatment response that increases tumour hypoxia drives selection of more malignant tumours.

Methods:

The LNCaP prostate tumour xenografts were analysed for physiological (oxygen and vasculature) and genetic (PCR array) changes during longitudinal treatment with ADT (bicalutamide, 6 or 2 mg kg⁻¹ daily for 28 days).

Results:

Bicalutamide caused an immediate (within 24 h) dose-dependent fall in oxygenation in LNCaP-luc prostate tumours with a nadir of ≤0.1% oxygen within 3–7 days; this was attributed to a significant loss of tumour microvessels (window chamber study). The hypoxic nadir persisted for 10–14 days. During the next 7 days, tumours regrew, oxygenation improved and the vasculature recovered; this was inhibited by the VEGF inhibitor B20.4.1.1. Gene expression over 28 days showed marked fluctuations consistent with the physiological changes. Accompanying the angiogenic burst (day 21) was a particularly striking increase in expression of genes associated with epithelial-to-mesenchymal transition (EMT). In particular, insulin-like growth factor 1 (IGF-1) showed increases in mRNA and protein expression.

Conclusions:

Hypoxic stress caused by ADT promotes EMT, providing a mechanism for the cause of malignant progression in prostate cancer.

Histologic evaluation of human benign prostatic hyperplasia treated by dutasteride: a study by xenograft model with improved severe combined immunodeficient mice

OBJECTIVE

To evaluate histologic change in human prostate samples treated with dutasteride and to elucidate direct effects of dutasteride on human prostate tissue, the present study was conducted by using a xenograft model with improved severe combined immunodeficient (super-SCID) mice, although it is well known that dutasteride reduces prostate volume.

METHODS

After establishment of a xenograft model of human benign prostatic hyperplasia in morphology and function, samples implanted into super-SCID mice with and without dutasteride were evaluated pathohistologically at 2 and 6 months after initiation of dutasteride administration.

RESULTS

The proliferative index evaluated by Ki-67 staining was significantly lower in the dutasteride group than the control at 2 and 6 months after administration. Apoptotic index evaluated by the terminal transferase TdT-mediated dUTP-biotin nick end labeling staining was higher in the dutasteride group than the control at 2 and 6 months after administration. Quick scores in the dutasteride group for staining of both cyclooxygenase-2 (Cox-2) and Ras homolog gene family, member A (RhoA) were significantly lower than those in the control group at 2 and 6 months after administration.

CONCLUSION

Dutasteride inhibits cell proliferation and induces apoptosis of prostatic cells, causing a reduced prostate volume. Furthermore, decreased expression of Cox-2 and RhoA within benign prostatic hyperplasia tissue by dutasteride may induce an early effect on improvement of lower urinary tract symptoms, probably by attenuating inflammation reaction of the prostate and decreasing intraurethral pressure, other than the mechanism of reduced prostate volume.

High SPDEF may identify patients who will have a prolonged response to androgen deprivation therapy

BACKGROUND

Due to the indolent nature of prostate cancer, new prognostic measures are needed to identify patients with life threatening disease. SAM pointed domain-containing Ets transcription factor (SPDEF) has been associated with good prognosis and demonstrates an intimate relationship with the androgen receptor (AR), however its role in prostate cancer progression remains unclear.

METHODS

A tissue microarray constructed from cores of 713 consecutive radical prostatectomy specimens were immunohistochemically stained for SPDEF and correlated with progression free and metastatic free survival. In vitro studies assessed growth rate, migration, and sensitivity to bicalutamide to explore mechanisms behind the tissue microarray observations.

RESULTS

Patients with high SPDEF demonstrate longer metastases free survival after receiving the standard of care (HR = 9.80, P = 0.006). SPDEF expression corresponded with bicalutamide growth inhibition and apoptosis induction in all cell lines studied. In addition, a feedforward loop of AR-SPEF expression regulation is observed.

CONCLUSIONS

SPDEF may be clinically useful to identify patients who will have extended benefits from androgen deprivation therapy. In vitro observations suggest SPDEF mediates initial sensitivity to androgen deprivation therapy through both AR regulation and downstream events.

Metabolomic profiling identifies biochemical pathways associated with castration-resistant prostate cancer

Despite recent developments in treatment strategies, castration-resistant prostate cancer (CRPC) is still the second leading cause of cancer-associated mortality among American men, the biological underpinnings of which are not well understood. To this end, we measured levels of 150 metabolites and examined the rate of utilization of 184 metabolites in metastatic androgen-dependent prostate cancer (AD) and CRPC cell lines using a combination of targeted mass spectrometry and metabolic phenotyping. Metabolic data were used to derive biochemical pathways that were enriched in CRPC, using Oncomine concept maps (OCM). The enriched pathways were then examined in-silico for their association with treatment failure (i.e., prostate specific antigen (PSA) recurrence or biochemical recurrence) using published clinically annotated gene expression data sets. Our results indicate that a total of 19 metabolites were altered in CRPC compared to AD cell lines. These altered metabolites mapped to a highly interconnected network of biochemical pathways that describe UDP glucuronosyltransferase (UGT) activity. We observed an association with time to treatment failure in an analysis employing genes restricted to this pathway in three independent gene expression data sets. In summary, our studies highlight the value of employing metabolomic strategies in cell lines to derive potentially clinically useful predictive tools.

Inhibition of the insulin-like growth factor-1 receptor enhances effects of simvastatin on prostate cancer cells in co-culture with bone

Prostate cancer (PC) bone metastases show weak responses to conventional therapies. Bone matrix is rich in growth factors, with insulin-like growth factor-1 (IGF-1) being one of the most abundant. IGF-1 acts as a survival factor for tumor cells and we speculate that bone-derived IGF-1 counteracts effects of therapies aimed to target bone metastases and, consequently, that therapeutic effects could be enhanced if given in combination with IGF-1 receptor (IGF-1R) inhibitors. Simvastatin inhibits the mevalonate pathway and has been found to induce apoptosis of PC cells. The aims of this study were to confirm stimulating effects of bone-derived IGF-1 on PC cells and to test if IGF-1R inhibition enhances growth inhibitory effects of simvastatin on PC cells in a bone microenvironment. The PC-3 and 22Rv1 tumor cell lines showed significantly induced cell growth when co-cultured with neonatal mouse calvarial bones. The tumor cell IGF-1R was activated by calvariae-conditioned media and neutralization of bone-derived IGF-1 abolished the calvarium-induced PC-3 cell growth. Treatment of PC-3 and 22Rv1 cells with simvastatin, or the IGF-1R inhibitor NVP-AEW541, reduced tumor cell numbers and viability, and induced apoptosis. Combined simvastatin and NVP-AEW541 treatment resulted in enhanced growth inhibitory effects compared to either drug given alone. Effects of simvastatin involved down-regulation of IGF-1R in PC-3 and of constitutively active androgen receptor variants in 22Rv1 cells. In conclusion, we suggest that IGF-1 inhibition may be a way to strengthen effects of apoptosis-inducing therapies on PC bone metastases; a possibility that needs to be further tested in pre-clinical models.

A road map to comprehensive androgen receptor axis targeting for castration-resistant prostate cancer

Gonadal androgen suppression (castration via orchiectomy or gonadotropin-releasing hormone analogues) suppresses circulating testosterone levels but does not achieve adequate androgen ablation within the prostate cancer microenvironment because it does not address adrenal and intratumoral steroid contributions. These residual extragonadal sources of androgens allow prostate cancer cells to survive, adapt, and evolve into castration-resistant prostate cancer (CRPC). The persistent significance of the androgen receptor (AR) axis in CRPC was recently validated by the clinical efficacy of androgen synthesis inhibitors (abiraterone) and novel, second-generation AR antagonists (enzalutamide). The appreciation that conventional therapeutic approaches achieve a suboptimal ablation of intratumoral androgens and AR axis signaling output opens transformative therapeutic opportunities. A treatment paradigm of comprehensive AR axis targeting at multiple levels (androgen synthesis, metabolism, and action) and at all relevant sites (gonadal, adrenal, intratumoral) simultaneously at the time of initiation of endocrine therapy (instead of the current approach of sequentially adding one agent at a time and only after disease progression) deserves examination in clinical trials to explore whether maximal first-line AR axis suppression via combination therapy can achieve maximal induction of cancer cell apoptosis (before they have the chance to adapt and evolve into CRPC) and thus, improve patient outcomes. Cancer Res; 73(15); 4599-605. ©2013 AACR.

Androgen deprivation results in time-dependent hypoxia in LNCaP prostate tumours: informed scheduling of the bioreductive drug AQ4N improves treatment response

Androgen withdrawal induces hypoxia in androgen-sensitive tissue; this is important as in the tumour microenvironment, hypoxia is known to drive malignant progression. Our study examined the time-dependent effect of androgen deprivation therapy (ADT) on tumour oxygenation and investigated the role of ADT-induced hypoxia on malignant progression in prostate tumours. LNCaP xenografted tumours were treated with anti-androgens and tumour oxygenation measured. Dorsal skin fold (DSF) chambers were used to image tumour vasculature in vivo. Quantitative PCR (QPCR) identified differential gene expression following treatment with bicalutamide. Bicalutamide-treated and vehicle-only-treated tumours were re-established in vitro, and invasion and sensitivity to docetaxel were measured. Tumour growth delay was calculated following treatment with bicalutamide combined with the bioreductive drug AQ4N. Tumour oxygenation measurements showed a precipitate decrease following initiation of ADT. A clinically relevant dose of bicalutamide (2 mg/kg/day) decreased tumour oxygenation by 45% within 24 hr, reaching a nadir of 0.09% oxygen (0.67 ± 0.06 mmHg) by Day 7; this persisted until Day 14 when it increased up to Day 28. Using DSF chambers, LNCaP tumours treated with bicalutamide showed loss of small vessels at Days 7 and 14 with revascularisation occurring by Day 21. QPCR showed changes in gene expression consistent with the vascular changes and malignant progression. Cells from bicalutamide-treated tumours were more malignant than vehicle-treated controls. Combining bicalutamide with AQ4N (50 mg/kg, single dose) caused greater tumour growth delay than bicalutamide alone. Our study shows that bicalutamide-induced hypoxia selects for cells that show malignant progression; targeting hypoxic cells may provide greater clinical benefit.

The stroma-a key regulator in prostate function and malignancy

Prostate cancer is a very common and highly unpredictable form of cancer. Whereas many prostate cancers are slow growing and could be left without treatment, others are very aggressive. Additionally, today there is no curative treatment for prostate cancer patients with local or distant metastasis. Identification of new, improved prognostic and diagnostic biomarkers for prostate cancer and the finding of better treatment strategies for metastatic prostate cancer is therefore highly warranted. Interactions between epithelium and stroma are known to be important already during prostate development and this interplay is critical also in development, progression of primary tumors and growth of metastases. It is therefore reasonable to expect that future biomarkers and therapeutic targets can be identified in the prostate tumor and metastasis stroma and this possibility should be further explored.

Persistent, biologically meaningful prostate cancer after 1 year of androgen ablation and docetaxel treatment

PURPOSE

Clinicians are increasingly willing to treat prostate cancer within the primary site in the presence of regional lymph node or even limited distant metastases. However, no formal study on the merits of this approach has been reported. We used a preoperative clinical discovery platform to prioritize pathways for assessment as therapeutic targets and to test the hypothesis that the primary site harbors potentially lethal tumors after aggressive treatment.

PATIENTS AND METHODS

Patients with locally advanced or lymph node-metastatic prostate cancer underwent 1 year of androgen ablation and three cycles of docetaxel therapy, followed by prostatectomy. All specimens were characterized for stage by accepted criteria. Expression of select molecular markers implicated in disease progression and therapy resistance was determined immunohistochemically and compared with that in 30 archived specimens from untreated patients with high-grade prostate cancer. Marker expression was divided into three groups: intracellular signaling pathways, stromal-epithelial interaction pathways, and angiogenesis.

RESULTS

Forty patients were enrolled, 30 (75%) of whom underwent prostatectomy and two (5%) who underwent cystoprostatectomy. Twenty-nine specimens contained sufficient residual tumor for inclusion in a tissue microarray. Immunohistochemical analysis showed increased epithelial and stromal expression of CYP17, SRD5A1, and Hedgehog pathway components, and modulations of the insulin-like growth factor I pathway.

CONCLUSION

A network of molecular pathways reportedly linked to prostate cancer progression is activated after 1 year of therapy; biomarker expression suggests that potentially lethal cancers persist in the primary tumor and may contribute to progression.

MDM2 antagonists boost antitumor effect of androgen withdrawal: implications for therapy of prostate cancer

BACKGROUND

Hormone therapy is the standard of care for newly diagnosed or recurrent prostate cancers. It uses anti-androgen agents, castration, or both to eliminate cancer promoting effect of testicular androgen. The p53 tumor suppressor controls a major pathway that can block cell proliferation or induce apoptosis in response to diverse forms of oncogenic stress. Activation of the p53 pathway in cancer cells expressing wild-type p53 has been proposed as a novel therapeutic strategy and recently developed MDM2 antagonists, the nutlins, have validated this in preclinical models of cancer. The crosstalk between p53 and androgen receptor (AR) signaling suggest that p53 activation could augment antitumor outcome of androgen ablation in prostate cancer. Here, we test this hypothesis in vitro and in vivo using the MDM2 antagonist, nutlin-3 and the p53 wild-type prostate cancer cell line, LNCaP.

RESULTS

Using charcoal-stripped serum as a cellular model of androgen deprivation, we show an increased apoptotic effect of p53 activation by nutlin-3a in the androgen-dependent LNCaP cells and to a lesser extent in androgen-independent but responsive 22Rv1 cell line. This effect is due, at least in part, to an enhanced downregulation of AR expression by activated p53. In vivo, androgen deprivation followed by two weeks of nutlin administration in LNCaP-bearing nude mice led to a greater tumor regression and dramatically increased survival.

CONCLUSIONS

Since majority of prostate tumors express wild-type p53, its activation by MDM2 antagonists in combination with androgen depletion may offer an efficacious new approach to prostate cancer therapy.

TNF is necessary for castration-induced prostate regression, whereas TRAIL and FasL are dispensable

TNF, a proinflammatory and immune-regulatory cytokine, is a potent apoptotic stimulus in vitro. However, there have been few examples of a physiologic role for TNF-induced apoptosis in vivo. Here, we describe a novel role for TNF in prostate epithelial cell apoptosis after androgen withdrawal. Employing high-resolution serial magnetic resonance imaging to measure mouse prostate volume changes over time, we demonstrate that the extent of castration-induced prostate regression is significantly reduced in mice null for either the Tnf or Tnfr1 genes but not mice deficient for TNF-related apoptosis-inducing ligand or Fas signaling. Wild-type mice receiving soluble TNF (sTNF) receptor 2 (to bind TNF and block signaling) before castration exhibit an identical reduction of prostate regression. Together, these data indicate that uniquely among known extrinsic death signals, TNF is required for castration-induced prostate regression. Additionally, membrane-bound TNF protein and stromal cell specific TNF mRNA levels increase in rat prostate after castration. This is consistent with a paracrine role for TNF in prostate regression. When injected into the peritoneum of Tnf(-/-) mice at the time of castration, sTNF restores normal levels of prostate regression. However, wild-type mice receiving sTNF in the absence of castration do not exhibit prostate regression, indicating that TNF alone is not sufficient but acts in the context of additional castration-induced signals. These findings support a physiologic role for TNF in prostate regression after androgen withdrawal. Understanding this role may lead to novel therapies for prostate cancer.

Targeting castration-induced tumour hypoxia enhances the acute effects of castration therapy in a rat prostate cancer model

What's known on the subject? and What does the study add? Castration therapy has rather modest effects on cell death in tumours but can be enhanced by other treatments targeting tumour stroma and vasculature. This study shows that the prostate becomes hypoxic following castration and that targeting hypoxic cells during castration therapy potently enhances the effects of castration.

OBJECTIVE

To explore the effects of castration therapy, the standard treatment for advanced prostate cancer, in relation to tumour hypoxia and to elicit its importance for the short- and long-term therapeutic response.

MATERIAL AND METHODS

We used the androgen-sensitive rat Dunning H prostate tumour model that transiently responds to castration treatment followed by a subsequent relapse, much like the scenario in human patients. Tumour tissues were analysed using stereological methods in intact, 1 and 7 days after castration therapy.

RESULTS

Hypoxia was transiently up-regulated after castration therapy and correlated with the induction of tumour cell apoptosis. When castration therapy was combined with tirapazamine (TPZ), a drug that targets hypoxic cells and the vasculature, the effects on tumour cell apoptosis and tumour volume were enhanced in comparison to either castration or TPZ alone.

CONCLUSION

The present study suggests that castration-induced tumour hypoxia is a novel target for therapy.

Characterization of the intra-prostatic immune cell infiltration in androgen-deprived prostate cancer patients

INTRODUCTION

Our goal was to study the hormonal regulation of immune cell infiltration in prostate cancer patients treated by androgen deprivation therapy (ADT) using an optimized computer-assistance quantification approach.

METHODS

The relative density of immune cell subtypes (CD3(+), CD8(+), CD20(+), CD56(+), CD68(+) and Foxp3(+)) was analyzed by immunohistochemistry in archived prostate specimens from control patients (radical prostatectomy only, n=40) and ADT-treated patients (ADT prior to radical prostatectomy, n=35) using an image analysis software and a whole-slide scanner.

RESULTS

ADT-treated patients had significantly increased relative density of CD3(+) (p<0.001) and CD8(+) T lymphocytes (p<0.001) as well as CD68(+) macrophages (p<0.001). Elevated abundance of CD56(+) Natural Killer (NK) cells was associated with a lower risk of prostate cancer progression (p=0.044), while a high density of CD68(+) macrophages was related to an increased risk of biochemical recurrence (p=0.011).

CONCLUSIONS

Our results demonstrate that the infiltration of specific immune cell subtypes is modulated by ADT. Furthermore our data confirm that NK cells have a protective role against tumor progression while macrophages seem to favor the development of advanced prostate cancer.

Low stroma androgen receptor level in normal and tumor prostate tissue is related to poor outcome in prostate cancer patients

BACKGROUND

The role of androgen receptors (ARs) in the prostate tumor cell environment is largely unknown.

METHODS

AR immunostaining was evaluated in relation to stroma morphology, expression of AR co-activator ARA55, tumor characteristics and clinical outcome in normal and prostate cancer (PCa) tissue obtained at transurethral resection in men treated with expectancy, and in diagnostic transrectal core biopsies in men treated with surgical castration. Stroma composition was studied by Masson-trichrome and desmin staining. Levels of AR and ARA55 mRNA were quantified by laser micro-dissection and RT-PCR.

RESULTS

The percentage of cells with positive nuclear AR immunostaining in the tumor and normal stroma was inversely related to Gleason score, tumor size, tumor stage, metastasis, response to castration therapy, and cancer-specific survival. The AR staining in the normal stroma provided independent prognostic information in Cox multiple linear regression analysis. Loss of stroma AR staining was linked to low expression of ARA55 in stroma smooth muscle cells, and in tumors also to gradual disappearance of this cell type.

CONCLUSIONS

PCa aggressiveness and efficacy of castration therapy are related to AR levels in the tumor stroma and importantly to AR levels in the surrounding normal prostate tissue stroma. .

Changes in the androgen levels in the ventral prostate of spontaneously hypertensive rats after castration

OBJECTIVE

To characterize the changes in androgen levels in the prostate after castration, as androgens are critical in the progression of prostate cancer after castration, but the time at which the androgen remaining in the prostatic cancer tissue after castration exerts its effects is poorly understood.

MATERIALS AND METHODS

The ventral prostate (VP) in adult male spontaneously hypertensive rats was excised at 2, 4 and 8 h, 1, 2, 4 and 7 days, and 2, 4 and 8 weeks after castration. The dihydrotestosterone (DHT), testosterone, dehydroepiandrosterone (DHEA) and androstenedione (4-dione) levels in the VP were measured simultaneously using gas chromatography/tandem mass spectrometry.

RESULTS

Within 2 days of castration, the DHT and testosterone levels in the VP decreased sharply, while there were no significant changes in the DHEA or 4-dione levels. From 2 days to 2 weeks after castration (2-7 days for 4-dione), there was a sharp peak in tissue androgen levels in the VP (P < 0.05 for all androgens); during the subsequent 6 weeks after castration, all of the tissue DHT, testosterone, DHEA and 4-dione levels gradually increased with time.

CONCLUSIONS

These data show the changes which occur in androgen levels in rat VP after castration and support the concept that the adrenal glands compensate for the loss of testicular androgen.

Androgen deprivation therapy: progress in understanding mechanisms of resistance and optimizing androgen depletion

Androgen deprivation therapy remains a critical component of treatment for men with advanced prostate cancer, and data support its use in metastatic disease and in conjunction with surgery or radiation in specific settings. Alternatives to standard androgen deprivation therapy, such as intermittent androgen suppression and estrogen therapy, hold the potential to improve toxicity profiles while maintaining clinical benefit. Current androgen deprivation strategies seem to incompletely suppress androgen levels and androgen-receptor-mediated effects at the tissue level. Advances in the understanding of mechanisms that contribute to castration-resistant prostate cancer are leading to rationally designed therapies targeting androgen metabolism and the androgen receptor. The results of large trials investigating the optimization of primary androgen deprivation therapy, including evaluation of intermittent androgen suppression and phase III studies of novel androgen synthesis inhibitors, such as abiraterone acetate, are eagerly awaited.

Phase II trial of docetaxel with rapid androgen cycling for progressive noncastrate prostate cancer

PURPOSE

We evaluated rapid androgen cycling in combination with docetaxel for men with progressive noncastrate prostate cancers.

PATIENTS AND METHODS

Noncastrate patients with 150 ng/dL) and an undetectable prostate-specific antigen (PSA;

RESULTS

A higher proportion of patients achieved the undetectable PSA outcome at 18 months in cohort 2 relative to cohort 1 (13% v 0%). The 16% incidence of febrile neutropenia was higher than that observed in patients was castration-resistant disease, which may have been related to a 50% reduction in overall docetaxel clearance in the noncastrate group. There was no alteration in CYP3A4 activity (P = .87) or docetaxel clearance (P = .88) between cycles.

CONCLUSION

The undetectable PSA end point allows for a rapid screening of interventions for further study. Increasing the number of docetaxel cycles after a shorter period of testosterone repletion, and a longer duration of testosterone depletion, increased the proportion of men who achieved an undetectable PSA. The higher-than-expected incidence of febrile neutropenia may have been related to the reduced overall docetaxel clearance in patients with noncastrate versus castrate testosterone levels.

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Key Words Collapse

MESH Headings

• Adult
• Aged
• Aged, 80 and over
• Antineoplastic Combined Chemotherapy Protocols/administration & dosage
• Cytochrome P-450 CYP3A
• Cytochrome P-450 Enzyme System/metabolism
• Docetaxel
• Humans
• Leuprolide/administration & dosage
• Male
• Middle Aged
• Prostate-Specific Antigen/blood
• Prostatic Neoplasms/drug therapy
• Prostatic Neoplasms/metabolism
• Taxoids/administration & dosage
• Taxoids/pharmacokinetics
• Testosterone/administration & dosage
• Testosterone/metabolism

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Grants

• P30 CA006973-48 NCI NIH HHS
• P30 CA006973 NCI NIH HHS
• P50-CA92629 NCI NIH HHS
• P50 CA092629 NCI NIH HHS
• PC051382 NCI NIH HHS

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Affiliation(s)

Dana Rathkopf Genitourinary Oncology Service, Department of Medicine, Memorial Sloan-Kettering Cancer Center, 1275 York Avenue, New York, New York, USA and Department of Medicine, Joan and Sanford Weill College of Medicine, New York, New York, USA
Michael A. Carducci Prostate Cancer Program, Sidney Kimmel Comprehensive Cancer Center at Johns Hopkins, Baltimore, MD, USA
Michael J. Morris Genitourinary Oncology Service, Department of Medicine, Memorial Sloan-Kettering Cancer Center, 1275 York Avenue, New York, New York, USA and Department of Medicine, Joan and Sanford Weill College of Medicine, New York, New York, USA
Susan F. Slovin Genitourinary Oncology Service, Department of Medicine, Memorial Sloan-Kettering Cancer Center, 1275 York Avenue, New York, New York, USA and Department of Medicine, Joan and Sanford Weill College of Medicine, New York, New York, USA
Mario A. Eisenberger Prostate Cancer Program, Sidney Kimmel Comprehensive Cancer Center at Johns Hopkins, Baltimore, MD, USA
Roberto Pili Prostate Cancer Program, Sidney Kimmel Comprehensive Cancer Center at Johns Hopkins, Baltimore, MD, USA
Samuel R. Denmeade Prostate Cancer Program, Sidney Kimmel Comprehensive Cancer Center at Johns Hopkins, Baltimore, MD, USA
Moshe Kelsen Genitourinary Oncology Service, Department of Medicine, Memorial Sloan-Kettering Cancer Center, 1275 York Avenue, New York, New York, USA and Department of Medicine, Joan and Sanford Weill College of Medicine, New York, New York, USA
Tracy Curley Genitourinary Oncology Service, Department of Medicine, Memorial Sloan-Kettering Cancer Center, 1275 York Avenue, New York, New York, USA and Department of Medicine, Joan and Sanford Weill College of Medicine, New York, New York, USA
Regina Priet Prostate Cancer Program, Sidney Kimmel Comprehensive Cancer Center at Johns Hopkins, Baltimore, MD, USA
Connie Collins Prostate Cancer Program, Sidney Kimmel Comprehensive Cancer Center at Johns Hopkins, Baltimore, MD, USA
Martin Fleisher Department of Epidemiology and Biostatistics, Memorial Sloan-Kettering Cancer Center, New York, New York, USA
Glenn Heller Department of Clinical Chemistry, Memorial Sloan-Kettering Cancer Center, New York, New York, USA
Sharyn D. Baker Pharmaceutical Sciences Department, St. Jude Children’s Research Hospital, Memphis, TN, USA
Howard I. Scher Genitourinary Oncology Service, Department of Medicine, Memorial Sloan-Kettering Cancer Center, 1275 York Avenue, New York, New York, USA and Department of Medicine, Joan and Sanford Weill College of Medicine, New York, New York, USA

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A novel tissue-slice culture model for non-malignant human prostate

A novel tissue culture system was established for modeling the non-neoplastic human prostate in vitro. Precision-cut prostate slices were cultivated in culture plates with a gas-permeable base in a novel serum-free mixture. Cultivated specimens was evaluated by an immunohistochemical analysis of cytokeratins 18 and 14, androgen receptor (AR), prostate specific antigen (PSA), prostate acid phosphatase (PAP), and the endothelial cell marker von Willebrand factor. Epithelial viability in the presence and absence of dihydrotestosterone (DHT) was also assessed. Satisfactory maintenance of glandular cytoarchitecture was observed in the presence of DHT with approximately half of the glands displaying a columnar or cuboidal phenotype and an intact layer of basal cells. In the absence of DHT, the corresponding percentage was significantly lower. The occurrence of involutive changes and epithelial cell death was significantly higher in the absence of DHT. Glandular and stromal cells maintained their capacity to express AR. PSA and PAP were expressed throughout the culture period, albeit at a lower level than in uncultured tissue. The viability of endothelial cells differed markedly between individual samples. During culture, the tissue slices became covered with epithelial cells originating from glands that were cut open during tissue slicing. This cell layer consisted of a stratified basal compartment overlaid by cells with a luminal phenotype. The present culture system provides a novel in vitro setting in which to study normal human prostate biology and pathobiology and may help to obviate problems related to the use of established cancer cell lines and animal models.

5alpha-reductase inhibitors in benign prostatic hyperplasia and prostate cancer risk reduction

Androgens play an essential role in prostatic development and function, but are also involved in prostate disease pathogenesis. The primary prostatic androgen, dihydrotestosterone (DHT), is synthesized from testosterone by 5alpha-reductase types 1 and 2. Inhibition of the 5alpha-reductase isoenzymes therefore has potential therapeutic benefit in prostate disease. The two currently approved 5alpha-reductase inhibitors (5ARIs), finasteride and dutasteride, have demonstrated long-term efficacy and safety in the treatment of benign prostatic hyperplasia. Finasteride, a type-2 5ARI, has also been studied for its ability to reduce the incidence of biopsy-detectable prostate cancer in the Prostate Cancer Prevention Trial. Treatment with dutasteride, a dual 5ARI, has been shown to result in a greater degree and consistency of DHT suppression compared with finasteride. Two large-scale studies of dutasteride are currently investigating the role of near-maximal DHT suppression in the settings of prostate cancer risk reduction and expectant management of localized prostate cancer.

A stroma targeted therapy enhances castration effects in a transplantable rat prostate cancer model

BACKGROUND

Castration results in a major involution of the normal prostate gland. This process is initiated by effects in the prostate stroma and vasculature. Castration-induced regression of androgen sensitive prostate tumors is however less prominent and hypothetically this could be related to a limited stromal/vascular response. We therefore used animal tumor models to explore the importance of stroma and vascular effects, and if castration effects could be enhanced by a simultaneous therapy targeting the tumor stroma.

METHODS

Using rats with Dunning PAP and H tumors, stereological methods, immunohistochemistry, and Western blotting, we studied the tumor response 7 and 28 days after castration and after the addition of stroma targeted therapies.

RESULTS

In the normal ventral prostate (VP) nuclear androgen receptors (AR) were rapidly downregulated after castration. In contrast, the Dunning tumors downregulated the AR in the cancerous epithelium, but not in the surrounding stroma. Vascular regulators such as the angiopoietins, tie 2, and PDGF-Rbeta were not decreased in the stroma after castration, as observed in the VP, creating an environment that prevents vascular involution. When a tumor stroma targeted therapy inhibiting the tie 2 receptor and the PDGF-Rbeta simultaneously was added to castration it resulted in a decreased vascular density, increased tumor cell apoptosis and decreased tumor growth compared to castration alone.

CONCLUSIONS

The stroma in highly differentiated androgen sensitive Dunning tumors is apparently androgen insensitive. If this unresponsive stroma is targeted the effects of castration can be enhanced.

Nuclear androgen receptors recur in the epithelial and stromal compartments of malignant and non-malignant human prostate tissue several months after castration therapy

BACKGROUND

As changed paracrine support from androgen receptor (AR)-positive cells in the prostate stroma contribute to castration-induced glandular involution, we examined if the subsequent relapse to androgen-independent epithelial cell growth could be related to reactivation of AR signaling in the stroma.

MATERIALS AND METHODS

Human prostate tissue taken before, within 14 days, and at suspected local tumor relapse after surgical castration therapy was immunostained for AR.

RESULTS

Castration initially decreased nuclear AR staining in epithelial and stroma cells, in both tumor and non-malignant tissue, but after some months, it reappeared.

CONCLUSIONS

Local tumor relapse was associated with reappearance of nuclear AR not only in tumor epithelial cells but also in the tumor stroma. Reappearance of nuclear AR in non-malignant prostate cells may be a physiological response to long-term systemic androgen ablation that could influence tumor growth.

Cellular Changes in Prostate Cancer Cells Induced by Intermittent Androgen Suppression

OBJECTIVES

This study used tumour specimens from a clinical trial on intermittent androgen suppression (IAS) to study the effects of castration on tissue morphology, cell proliferation, apoptosis, and the expression of androgen receptor (AR).

METHODS

A total of 113 representative needle biopsy specimens were available from 29 patients for evaluation of the Gleason score as well as Ki-67, cleaved caspase-3, and AR immunostaining.

RESULTS

At 6 mo from the beginning of the first androgen withdrawal, cell proliferation activity was significantly (p = 0.002) reduced, whereas no effect on apoptosis was found. A nonsignificant trend to an increase in Gleason score after castration was found. Subsequent cycles of withdrawals had no significant effect on any of the measured parameters. The Gleason score, proliferation activity, and apoptosis rate showed only heterogeneous, nonsignificant changes after the first progression. Strong nuclear AR staining was evident in all cancer specimens.

CONCLUSIONS

The findings suggest that the long-term (months) effect of androgen withdrawal on tumour growth is due to the inhibition of proliferation. Because the tumours seem to become resistant to castration at the first cycle of treatment withheld, it is possible that IAS does not postpone the emergence of ablation-resistant tumours. There was no consistent sign of increased proliferation or Gleason score during the treatment, suggesting that the biologic aggressiveness of a particular tumour is defined already at an early stage of disease. The constant nuclear expression of AR in cancer cells indicates that the AR signalling remains active despite of the androgen withdrawal.

Intraprostatic androgens and androgen-regulated gene expression persist after testosterone suppression: therapeutic implications for castration-resistant prostate cancer

Androgen deprivation therapy (ADT) remains the primary treatment for advanced prostate cancer. The efficacy of ADT has not been rigorously evaluated by demonstrating suppression of prostatic androgen activity at the target tissue and molecular level. We determined the efficacy and consistency of medical castration in suppressing prostatic androgen levels and androgen-regulated gene expression. Androgen levels and androgen-regulated gene expression (by microarray profiling, quantitative reverse transcription-PCR, and immunohistochemistry) were measured in prostate samples from a clinical trial of short-term castration (1 month) using the gonadotropin-releasing hormone antagonist, Acyline, versus placebo in healthy men. To assess the effects of long-term ADT, gene expression measurements were evaluated at baseline and after 3, 6, and 9 months of neoadjuvant ADT in prostatectomy samples from men with localized prostate cancer. Medical castration reduced tissue androgens by 75% and reduced the expression of several androgen-regulated genes (NDRG1, FKBP5, and TMPRSS2). However, many androgen-responsive genes, including the androgen receptor (AR) and prostate-specific antigen (PSA), were not suppressed after short-term castration or after 9 months of neoadjuvant ADT. Significant heterogeneity in PSA and AR protein expression was observed in prostate cancer samples at each time point of ADT. Medical castration based on serum testosterone levels cannot be equated with androgen ablation in the prostate microenvironment. Standard androgen deprivation does not consistently suppress androgen-dependent gene expression. Suboptimal suppression of tumoral androgen activity may lead to adaptive cellular changes allowing prostate cancer cell survival in a low androgen environment. Optimal clinical efficacy will require testing of novel approaches targeting complete suppression of systemic and intracrine contributions to the prostatic androgen microenvironment.

The basic biochemistry and molecular events of hormone therapy

Data regarding the molecular response of prostate cancer to hormone therapy continue to emerge, identifying a complex network of autocrine and paracrine signaling events mediating the tumor response to androgen suppression. Emerging data provide insight into cellular pathways important in the apoptotic response to therapy, including the transforming growth factor-beta, insulin-like growth factor-1, and vascular endothelial growth factor signaling axes. They also reveal mechanisms of direct antitumor cytotoxicity mediated by various hormonal agents and highlight the importance of developing antiandrogens capable of irreversibly inhibiting the androgen receptor. Accumulated data emphasize the presence of residual androgens and persistent activation of androgen receptor signaling in advanced prostate tumors despite castration. These factors suggest that a multitargeted treatment approach designed to ablate all contributions to the androgen receptor signaling axis within the prostate tumor microenvironment will be required in order for hormonal therapy to achieve optimal antitumor efficacy.

Rapid androgen cycling as treatment for patients with prostate cancer

PURPOSE

To investigate the safety and feasibility of rapid androgen cycling for men with progressive prostate cancer.

EXPERIMENTAL DESIGN

Schedule 1 included a 4-week induction of androgen depletion, followed by 4-week treatment cycles of a monthly gonadotropin-releasing hormone agonist, testosterone on days 1 to 7, and an estrogen patch on days 8 to 21. Schedule 2 included a 12-week induction of androgen depletion followed by 4-week cycles of gonadotropin-releasing hormone agonist and testosterone, but no estrogens for patients with a prostate-specific antigen (PSA) nadir <1 ng/mL after induction. The primary end point was serially declining PSA trough values over six treatment cycles.

RESULTS

Thirty-six patients were treated; 27 were evaluable after cycling, of whom 8 of 12 (67%) and 9 of 15 (60%) on schedules 1 and 2, respectively, reached the end point. Five patients with PSA >1 ng/mL following induction did not cycle. No patient progressed radiographically or clinically during cycling. Three posttherapy PSA patterns were observed: a decline followed by a rapid increase in trough levels, a sustained decline with a plateau at a detectable nadir, and a decline to an undetectable nadir. Mean testosterone levels were castrate at the time of trough and in the normal physiologic range following androgen repletion. Major toxicities included grades 1 and 2 fatigue, hepatitis, gynecomastia, and hot flashes.

CONCLUSIONS

Rapid hormonal cycling is feasible and well tolerated, and successive declines in PSA troughs are achievable. Although the sample size was small, the proportion of patients achieving declining PSA at the end of six cycles was comparable with that reached with continuous androgen depletion therapy.

Androgen-insensitive prostate cancer cells transiently respond to castration treatment when growing in an androgen-dependent prostate environment

BACKGROUND

Castration-induced involution of the normal prostate is caused by primary effects in the prostate stroma and vasculature, but if this is the case also in tumors is unknown.

METHODS

Androgen-independent AT-1 prostate tumor cells were therefore injected into the ventral prostate (VP) in Copenhagen rats. Seven days later when the growing tumor was surrounded by normal VP tissue the rats were castrated and the effect examined 3 and 7 days later.

RESULTS

Castration reduced vascular density in the surrounding VP tissue and this was accompanied by tumor cell hypoxia, apoptosis, and temporarily retarded tumor growth. Castration-induced VP tissue regression occurred more rapidly in the contra-lateral than in the tumor-bearing lobe.

CONCLUSIONS

Androgen-independent tumor cell respond to castration when growing in an androgen-dependent environment. The presence of a tumor influences the castration response in the surrounding normal tissue. The microenvironment determines how prostate epithelial cells respond to castration.

Early effects of pharmacological androgen deprivation in human prostate cancer

OBJECTIVES

To assess the early histological effects of pharmacological androgen deprivation (AD), which have been assessed only over longer periods, as surgical castration leads rapidly to diminished cell proliferation and enhanced cell death within the prostate.

PATIENTS AND METHODS

With Institutional Review Board approval, 35 patients were randomly assigned (seven in each group) to receive 0, 7, 14, 21 and 28 days of AD (flutamide, 250 mg orally three times/day, and one injection with leuprolide acetate 7.5 mg) before radical prostatectomy. The surgical specimens were assessed by conventional histology and immunohistochemistry, while macroarray analysis and quantitative real-time polymerase chain reaction (QRT-PCR) were used to examine gene expression.

RESULTS

There were morphological changes within the prostatic tissues as early as 7 days after initiating AD, similar to the response to castration. There was tumour cell vacuolization indicating cellular injury, glandular atrophy and mononuclear cell infiltration as prominent and progressive effects but, by contrast with castration studies, there were no changes in epithelial proliferation or apoptosis. Macroarray analysis, validated by QRT-PCR and immunohistochemistry, showed up-regulation of numerous and potentially counter-effective genes involved in the cell cycle and apoptosis.

CONCLUSIONS

Pharmacological AD induces significant involution within prostatic tissues over 7-28 days, but allows the persistence of some viable tumour cells capable of proliferation.

Castration-induced epithelial cell death in human prostate tissue is related to locally reduced IGF-1 levels

BACKGROUND

Castration rapidly reduces stroma insulin-like growth factor (IGF)-1 synthesis and action in mouse prostate epithelium. We explore if similar changes are of importance for castration-induced prostate regression in humans.

METHODS

Epithelial and surrounding stroma cells were micro-dissected from patient biopsies obtained before and shortly after castration. IGF-1 mRNA levels were quantified by RT-PCR and related to epithelial apoptosis and IGF-1, IGF-1 receptor, and androgen receptor (AR) immunoreactivity.

RESULTS

IGF-1 mRNA was principally produced in the stroma and IGF-R1 in the epithelium. Stroma IGF-1 mRNA levels were significantly decreased after castration in non-malignant but not malignant tissue. Lack of stroma IGF-1 reduction after castration was associated with low stroma AR expression before therapy. Reduction of IGF-1 mRNA levels in the tumor stroma and/or epithelium was associated with epithelial apoptosis after therapy.

CONCLUSIONS

Low AR expression and maintained stroma IGF-1 synthesis may result in limited tumor cell death after castration therapy.

Inhibitory Effects of Castration in an Orthotopic Model of Androgen-Independent Prostate Cancer Can Be Mimicked and Enhanced by Angiogenesis Inhibition

PURPOSE

Today, the most important treatment of advanced prostate cancer is castration; unfortunately, however, the long-term effect of this therapy is insufficient. Recent studies suggest that castration-induced prostate involution could be caused by primary effects in the prostate vasculature; therefore, we examined if antivascular treatments could mimic the effects of castration.

EXPERIMENTAL DESIGN

Androgen-independent AT-1 prostate cancer cells were grown inside the ventral prostate in adult rats. Tumor-bearing animals were treated with an inhibitor of vascular endothelial growth factor receptor 2 and epidermal growth factor receptor signaling, N-(4-bromo-2-fluorophenyl)-6-methoxy-7-[(1-methylpiperidin-4-yl)methoxy]quinazolin-4-amine (ZD6474, AstraZeneca, Södertälje, Sweden), and short-term effects (after 3 days) were compared with those induced by castration.

RESULTS

Castration caused decreased vascular density in the normal tissue surrounding the tumor and consequently increased tumor hypoxia and apoptosis, and moderately decreased tumor growth. ZD6474 treatment resulted in decreased tumor vascular density accompanied by increased tumor hypoxia, apoptosis, and decreased tumor growth, suggesting that castration and antiangiogenic therapy work through similar mechanisms. Interestingly, castration or ZD6474 alone worked by reducing vascular density in the surrounding normal tissue and ZD6474 also in the tumor. Combined treatment with castration + ZD6474 was more effective than castration and ZD6474 alone in inducing tumor hypoxia, apoptosis, necrosis, and decreasing tumor vascular density.

CONCLUSION

These findings show that a drug that targets the vasculature in the tumor and in the surrounding ventral prostate lobe could mimic and even enhance the effects of castration. Our present findings thus suggest that castration + ZD6474 could be a particularly effective way to treat prostate tumors.