A nonlinear model with competition between prostate tumor cells and its application to intermittent androgen suppression therapy of prostate cancer

The recurrence of a tumor is a crucial problem in hormonal therapy of prostate cancer. Recent studies suggest that intermittent androgen suppression administration may prolong or hopefully prevent the progression to the recurrence. It was shown that a simple mathematical model is useful to understand how and why intermittent administration can be effective and to seek a better medication scheme. In this paper, we propose a new model for the intermittent androgen suppression therapy. What is central in the new model is that the competitive effect between androgen-dependent and independent cancer cells is assumed to be essential for the decrease of androgen-independent cells under a normal androgen level. In the newly proposed model, the separatrix in the phase space for a normal androgen level plays an important role. There is crucial difference between the previous model and the new one in the phase diagram of success and failure of the permanent tumor control by intermittent androgen suppression administration. That means that the suggestions from the models for clinical problems can be different. We also consider the combined model of the previous and newly proposed models, which can smoothly bridge two models.     

Development of a mathematical model that predicts the outcome of hormone therapy for prostate cancer

We propose a mathematical model that quantitatively reproduces the dynamics of the serum prostate-specific antigen (PSA) level under intermittent androgen suppression (IAS) for prostate cancer. Taking into account the biological knowledge that there are reversible and irreversible changes in a malignant cell, we constructed a piecewise-linear dynamical model where the testosterone dynamics are modelled with rapid shifts between two levels, namely the normal and castrate concentrations of the male hormone. The validity of the model was supported by patient data obtained from a clinical trial of IAS. It accurately reproduced the kinetics of the therapeutic reduction of PSA and predicted the future nadir level correctly. The coexistence of reversible and irreversible changes within the malignant cell provided the best explanation of early progression to androgen independence. Finally, since the model identified patients for whom IAS was effective, it potentially offers a novel approach to individualized therapy requiring the input of time sequence values of PSA only.     

The androgen receptor: a potential target for therapy of prostate cancer

The androgen receptor plays a pivotal role in the prostate. Its primary function is to provide responsive gene products for differentiation and growth, but under abnormal conditions it contributes to the development of prostate cancer. The goal of this review is to elucidate the molecular functions of the androgen receptor and its role in prostate cancer. Initially the function of the androgen receptor will be described. Next, the clinical diagnosis, epidemiological impact, and treatments of androgen-dependent and -independent prostate cancer will be discussed. Finally we will examine how the mechanism of androgen action has played a role in the translation of new therapies and how this may influence future treatment modalities of prostate cancer.     

Treatment outcomes and late toxicities of intensity-modulated radiation therapy for 1091 Japanese patients with localized prostate cancer

Aim

This study aimed to evaluate the treatment result of intensity-modulated radiation therapy (IMRT) in a large number of Japanese patients with prostate cancer.

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.     

SIMBOSPROST: Prevalence of metabolic syndrome and osteoporosis in prostate cancer patients treated with radiotherapy and androgen deprivation therapy: A multicentre,cross-sectional study

AimTo assess the prevalence of metabolic syndrome (MetS) and osteoporosis in patients with prostate cancer (PCa) treated with radical radiotherapy (RT) with or without androgen deprivation therapy (ADT).BackgroundWorldwide, the prevalence of MetS is estimated to range from 20% to 25% of the adult population. However, prevalence rates are much higher in PCa patients (pts) who undergo ADT.Materials and methodsMulticentre cross-sectional study of 270 pts in Spain with PCa. Patients were divided into 3 groups based on the duration of ADT (6, 12–18, ≥24 months) and compared to a control group without ADT. MetS was defined according to NCEP ATP III criteria. Osteoporosis was assessed by DEXA.ResultsA total of 270 pts, treated from November 2011 to October 2012, were included. Of these, 122 pts (47%) fulfilled the criteria for MetS. The median age of this group was significantly higher (71.3 vs. 69.38 years, p = 0.028). MetS prevalence was 50% in the control group. In pts who received ADT, prevalence was 44.8% after 6 months of ADT, 45.3% after 12–18 months, and 50% after ≥24 months (pns). Most pts (168/270; 62%) underwent DEXA. Of those tested, 78 (46.4%) had osteopenia and only 11 (6.5%) had osteoporosis.ConclusionsThe prevalence of MetS in pts with PCa treated with radical RT was higher (47%) than in the general population. However, there were no significant differences in the duration of ADT administration. The prevalence of osteoporosis was low. These findings suggest that the prevalence of MetS in PCa patients may be higher than previously reported.     

Uroncor consensus statement: Management of biochemical recurrence after radical radiotherapy for prostate cancer: From biochemical failure to castration resistance

Management of patients who experience biochemical failure after radical radiotherapy with or without hormonal therapy is highly challenging. The clinician must not only choose the type of treatment, but also the timing and optimal sequence of treatment administration. When biochemical failure occurs, numerous treatment scenarios are possible, thus making it more difficult to select the optimal approach. Moreover, rapid and ongoing advances in treatment options require that physicians make decisions that could impact both survival and quality of life.The aim of the present consensus statement, developed by the Urological Tumour Working Group (URONCOR) of the Spanish Society of Radiation Oncology (SEOR), is to provide cancer specialists with the latest, evidence-based information needed to make the best decisions for the patient under all possible treatment scenarios.The structure of this consensus statement follows the typical development of disease progression after biochemical failure, with the most appropriate treatment recommendations given for each stage. The consensus statement is organized into three separate chapters, as follows: biochemical failure with or without local recurrence and/or metastasis; progression after salvage therapy; and treatment of castration-resistant patients.     

5alpha-androstane-3alpha,17beta-diol supports human prostate cancer cell survival and proliferation through androgen receptor-independent signaling pathways: implication of androgen-independent prostate cancer progression

Androgen and androgen receptor (AR) are involved in growth of normal prostate and development of prostatic diseases including prostate cancer. Androgen deprivation therapy is used for treating advanced prostate cancer. This therapeutic approach focuses on suppressing the accumulation of potent androgens, testosterone and 5alpha-dihydrotestosterone (5alpha-DHT), or inactivating the AR. Unfortunately, the majority of patients with prostate cancer eventually advance to androgen-independent states and no longer respond to the therapy. In addition to the potent androgens, 5alpha-androstane-3alpha,17beta-diol (3alpha-diol), reduced from 5alpha-DHT through 3alpha-hydroxysteroid dehydrogenases (3alpha-HSDs), activated signaling may represent a novel pathway responsible for the progression to androgen-independent prostate cancer. Androgen sensitive human prostate cancer LNCaP cells were used to compare 5alpha-DHT and 3alpha-diol activated androgenic effects. In contrast to 5alpha-DHT, 3alpha-diol regulated unique patterns of beta-catenin and Akt expression as well as Akt phosphorylation in parental and in AR-silenced LNCaP cells. More significantly, 3alpha-diol, but not 5alpha-DHT, supported AR-silenced LNCaP cells and AR negative prostate cancer PC-3 cell proliferation. 3alpha-diol-activated androgenic effects in prostate cells cannot be attributed to the accumulation of 5alpha-DHT, since 5alpha-DHT formation was not detected following 3alpha-diol administration. Potential accumulation of 3alpha-diol, as a result of elevated 3alpha-HSD expression in cancerous prostate, may continue to support prostate cancer growth in the presence of androgen deprivation. Future therapeutic strategies for treating advanced prostate cancer might need to target reductive 3alpha-HSD to block intraprostatic 3alpha-diol accumulation.     

Current status of androgen suppression and radiotherapy for patients with prostate cancer

Analogous to the impact of anti-estrogen therapy in breast cancer, anti-androgen therapy may have a greater impact on the castrate male with non-metastatic disease. The use of castration or a LHRH drug alone, does not appear to adequately suppress intra-prostatic DHT (Dihydrotestosterone) levels. Normal prostate elements appear to be more efficient than metastatic elements at converting DHT precursors to active DHT. Thus, blocking this step may be more critical for clinically localized disease. Laverdiere et al. reported a 2 year positive (+) biopsy rate of 65% with XRT alone compared to 28% when 3 months of NHT preceded radiotherapy, but 5% if NHT was continued for a total of 10.5 months of combined androgen blockade (CAB). Bolla et al. incorporated one month of NHT prior to XRT followed by 3 years of an LHRH drug. An improvement in local control, disease free survival and overall survival of nearly 20% was noted at 5 years. Thus far, these important studies demonstrate that a survival benefit may require long term adjuvant hormonal therapy. There is a need for further studies to define the optimal timing and duration of CAB and the role of XRT. Long term data recently provided by the Radiation Therapy Oncology Group (RTOG) may provide insights into criteria for defining which patients are likely to benefit the most from long term CAB.     

DU-145 and PC-3 human prostate cancer cell lines express androgen receptor: implications for the androgen receptor functions and regulation

The majority of human prostate cancer cell lines, including the two "classical" cell lines DU-145 and PC-3, are reported to be androgen receptor (AR)-negative. However, other studies have provided evidence that the DU-145 and PC-3 cell lines express AR mRNA. These contradictory observations prompted us to investigate whether DU-145 and PC-3 cell lines express the androgen receptor. Using antipeptide antibodies directed against three distinct regions of the human AR protein and an improved method to detect AR protein in immunoblotting, we report that DU-145 and PC-3 cell lines express AR protein. We found that the relative levels of the AR mRNA and protein that were detected in DU-145 and PC-3 cell lines were lower than the LNCaP, an AR-positive cell line. Moreover, the antibody directed against the non-variant region (amino acids 299-315), but not the variant N- or C-terminal region (amino acids 1-20 and 900-919, respectively) of the human AR protein, detected the expression of AR in all prostate cancer cell lines. Notably, treatment of these cell lines with dihydrotestosterone (DHT) resulted in measurable increases in the AR protein levels and considerable nuclear accumulation. Although, treatment of DU-145 and PC-3 cells with DHT did not result in stimulation of the activity of an AR-responsive reporter, knockdown of AR expression in PC-3 cells resulted in decreases in p21(CIP1) protein levels, and a measurable decrease in the activity of the p21-luc-reporter. Our observations demonstrate the expression of AR protein in DU-145 and PC-3 prostate cancer cell lines.     

Context-dependent role of ATG4B as target for autophagy inhibition in prostate cancer therapy

ATG4B belongs to the autophagin family of cysteine proteases required for autophagy, an emerging target of cancer therapy. Developing pharmacological ATG4B inhibitors is a very active area of research. However, detailed studies on the role of ATG4B during anticancer therapy are lacking. By analyzing PC-3 and C4-2 prostate cancer cells overexpressing dominant negative ATG4B^C74Ain vitro and in vivo, we show that the effects of ATG4B^C74A are cell type, treatment, and context-dependent. ATG4B^C74A expression can either amplify the effects of cytotoxic therapies or contribute to treatment resistance. Thus, the successful clinical application of ATG4B inhibitors will depend on finding predictive markers of response.     

The androgen receptor (AR) in syndromes of androgen insensitivity and in prostate cancer

The actions of androgens, principally testosterone and 5alpha-dihydrotestosterone, are mediated by a specific receptor protein, the androgen receptor (AR), which is encoded by a single-copy gene located on the human X-chromosome. This receptor protein is a prototypical member of the nuclear receptor family and modulates a range of processes during embryogenesis and in the adult. During embryogenesis, normal AR function is critical to the development of the male phenotype and defects of the AR cause a range of phenotypic abnormalities of male sexual development. Complete loss of AR function has been traced to a number of distinct types of genetic events, including abnormalities of mRNA splicing, the introduction of premature termination codons, and amino acid substitution mutations. An interesting subset of mutations is that in which the AR is completely undetectable using sensitive immunoassays. In all instances, these functional abnormalities are associated with a phenotype of complete androgen insensitivity (complete testicular feminization). By contrast, partial defects of AR function are almost invariably caused by amino acid substitutions within the DNA- and hormone-binding domains of the receptor protein. Such partial defects of receptor function may be caused by changes in either receptor function or receptor abundance.The alterations of AR function and expression that have been characterized in clinical prostatic cancers and in prostate cancer cell lines differ in several important respects. A number of studies have documented the emergence of considerable heterogeneity of AR expression at early stages in the development of prostate cancer. Despite these early changes of AR expression, a substantial body of information suggests that the AR is expressed in advanced forms of prostate cancer, in some cases as the result of amplification events. While infrequent in localized tumors, mutations of the AR have been identified in a number of advanced prostatic cancers and in some instances appear to alter the ligand specificity of the AR. Finally, it appears that other signaling pathways can act to influence AR function.     

Selective gene therapy for prostate cancer cells using liposomes conjugated with IgM type monoclonal antibody against prostate-specific membrane antigen

Prostate cancer cells express prostate-specific membrane antigen (PSMA). We developed an IgM type monoclonal antibody against PSMA. The antibody was coupled to poly-L-lysine and thereafter this conjugate was mixed with cationic liposomes containing plasmid DNA. The antibody-liposome complex was tested whether it could deliver the gene of interest selectively to the PSMA positive cells. As assessed by beta-galactosidase reporter gene, the transfection efficiency was 13.2% with anti-PSMA-liposome complex as compared to 4% with control IgM liposome complex. In contrast, no such differences were observed in PSMA negative PC-3, DU145 and T24 cells. Furthermore, in the suicide gene therapy in vitro with thymidine kinase gene plus ganciclovir system, anti-PSMA liposome complex demonstrated a selective growth inhibitory effect on PSMA positive LNCaP cells but not on PSMA negative cell lines.     

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.     

Interaction of IGF signaling and the androgen receptor in prostate cancer progression

The insulin-like growth factor type I receptor (IGF-IR) has been suggested to play an important role in prostate cancer progression and possibly in the progression to androgen-independent (AI) disease. The term AI may not be entirely correct, in that recent data suggest that expression of androgen receptor (AR) and androgen-regulated genes is the primary association with prostate cancer progression after hormone ablation. Therefore, signaling through other growth factors has been thought to play a role in AR-mediated prostate cancer progression to AI disease in the absence of androgen ligand. However, existing data on how IGF-IR signaling interacts with AR activation in prostate cancer are conflicting. In this Prospect article, we review some of the published data on the mechanisms of IGF-IR/AR interaction and present new evidence that IGF-IR signaling may modulate AR compartmentation and thus alter AR activity in prostate cancer cells. Inhibition of IGF-IR signaling can result in cytoplasmic AR retention and a significant change in androgen-regulated gene expression. Translocation of AR from the cytoplasm to the nucleus may be associated with IGF-induced dephosphorylation. Since fully humanized antibodies targeting the IGF-IR are now in clinical trials, the current review is intended to reveal the mechanisms of potential therapeutic effects of these antibodies on AI prostate cancers.