CAG polymorphic repeat lengths in androgen receptor gene among Japanese prostate cancer patients: potential predictor of prognosis after endocrine therapy

Comparative analysis of novel hormonal agents in non-metastatic castration-resistant prostate cancer: A Taiwanese perspective

BACKGROUND

Non-metastatic castration-resistant prostate cancer (nmCRPC) is an asymptomatic condition with the potential to progress to metastasis. Novel hormonal agents (NHAs) are currently considered the gold standard treatment for nmCRPC, offering significant survival benefits. However, further evidence is needed to determine whether there are differences in the performance of these drugs among Asian populations.

METHODS

This retrospective analysis of nmCRPC patients aims to compare the efficacy and safety of three NHAs-apalutamide, darolutamide, and enzalutamide. Data were collected from two prominent prostate care centers in Taichung, Taiwan. Patient characteristics, treatment details, PSA responses, and adverse events were analyzed. Statistical comparisons were performed, and the study received Institutional Review Board approval.

RESULTS

Total of 64 patients were recruited in this study, including 29 darolutamide, 26 apalutamide, and 9 enzalutamide patients. Baseline characteristics varied between the three patient groups, but the treatment response still revealed similar results. The apalutamide group experienced more adverse events, notably skin rash. Discontinuation rates due to adverse events differed among the groups, and patients receiving darolutamide were less likely to discontinue treatment.

CONCLUSION

This real-world study provides insights into NHA utilization in nmCRPC within the Taiwanese population. Adverse event profiles varied, emphasizing the need for individualized treatment decisions. The study underscores the importance of regional considerations and contributes valuable data for optimizing treatment outcomes in nmCRPC.

Prostate cancer therapy outcome prediction: are miRNAs a suitable guide for therapeutic decisions?

BACKGROUND

Radical prostatectomy, radiotherapy, chemotherapy, and androgen-deprivation therapy are among the most common treatment options for different forms of prostate cancer (PCa). However, making therapeutic decisions is difficult due to the lack of reliable prediction markers indicating therapy outcomes in clinical practice. The involvement of miRNAs in all mechanisms of the PCa development and their easy detection characterize them as attractive PCa biomarkers. Although there are extensive data on the role of miRNAs in PCa therapy resistance and sensitivity development, the issues of whether they could be used as a guide for therapy choice and, if so, how we can progress toward this goal, remain unclear. Thus, generalizable reviews and studies which summarize, compare, and analyze data on miRNA involvement in responses to different types of PCa therapies are required.

OBJECTIVES

Data on the involvement of miRNAs in therapy responses, on the role of cross-miRNA expression in different therapies, and on miRNA targets were analyzed in order to determine the miRNA-related factors which can lend perspective to the future development of personalized predictors of PCa sensitivity/resistance to therapies.

MATERIALS AND METHODS

The data available on the miRNAs associated with different PCa therapies (resistance and sensitivity therapies) are summarized and analyzed in this study, including analyses using bioinformatics resources. Special attention was dedicated to the mechanisms of the development of therapy resistance.

RESULTS AND DISCUSSION

A comprehensive combined analysis of the current data revealed a panel of miRNAs that were shown to be most closely associated with the PCa therapy response and were found to regulate the genes involved in PCa development via cell proliferation regulation, epithelial-mesenchymal transition (EMT), apoptosis, cell-cycle progression, angiogenesis, metastasis and invasion regulation, androgen-independent development, and colony formation.

CONCLUSION

The selected miRNA-based panel has the potential to be a guide for therapeutic decision making in the effective treatment of PCa.

miRNAs and androgen deprivation therapy for prostate cancer

Androgen deprivation therapy (ADT) is mainly used for the treatment of advanced, metastatic or recurrent prostate cancer (PCa). However, patients progress to ADT resistance and castration-resistant prostate cancer (CRPC) with a poor prognosis. Reliable validated markers of ADT resistance with proven clinical utility are necessary for timely correction of the therapy as well as for improvement of patient quality of life. MiRNAs involved in the ADT response and CRPC development via multiple mechanisms may act as biomarkers for patient outcomes. Available data on miRNAs associated with the ADT response (resistance and sensitivity) are summarized and analyzed in the manuscript, including analyses using bioinformatics resources. Molecular targets of miRNAs, as well as reciprocal relations between miRNAs and their targets, were studied using different databases. Special attention was dedicated to the mechanisms of ADT resistance and CRPC development, including testosterone, PI3K-AKT, VEGF pathways and associated genes. Several different approaches can be used to search for miRNAs associated with the ADT response, each of which focuses on the associated set of miRNAs - potential markers of ADT. The intersection of these approaches and combined analysis allowed us to select the most promising miRNA markers of the ADT response. Meta-analysis of the current data indicated that the selected 5 miRNAs (miRNAs - 125b, miR-21, miR-23b, miR-27b and miR-221) and 14 genes are involved in the regulation of key processes of CRPC development and represent the most promising predictors of the ADT response, further demonstrating their potential in combination therapy for advanced PCa.

Somatic Alterations Impact AR Transcriptional Activity and Efficacy of AR-Targeting Therapies in Prostate Cancer

Simple Summary

For patients whose prostate cancer spreads beyond the confines of the prostate, treatment options continue to increase. However, we are missing the information that is needed to choose for each patient the best treatment at each step of his cancer progression so we can ensure that maximal remissions and prolonged survival are achieved. In this review, we examine whether a better understanding of how the activity of the target for the default first treatment, the androgen receptor, is regulated in prostate cancer tissues can improve prostate cancer treatment plans. We consider the evidence for variability of androgen receptor activity among patients and examine the molecular basis for this variable action. We summarize clinical evidence supporting that information on a prostate cancer’s genomic composition may inform on its level of androgen receptor action, which may facilitate choice for the most effective first-line therapy and ultimately improve prostate cancer treatment plans overall.

Abstract

Inhibiting the activity of the ligand-activated transcription factor androgen receptor (AR) is the default first-line treatment for metastatic prostate cancer (CaP). Androgen deprivation therapy (ADT) induces remissions, however, their duration varies widely among patients. The reason for this heterogeneity is not known. A better understanding of its molecular basis may improve treatment plans and patient survival. AR’s transcriptional activity is regulated in a context-dependent manner and relies on an interplay between its associated transcriptional regulators, DNA recognition motifs, and ligands. Alterations in one or more of these factors induce shifts in the AR cistrome and transcriptional output. Significant variability in AR activity is seen in both castration-sensitive (CS) and castration-resistant CaP (CRPC). Several AR transcriptional regulators undergo somatic alterations that impact their function in clinical CaPs. Some alterations occur in a significant fraction of cases, resulting in CaP subtypes, while others affect only a few percent of CaPs. Evidence is emerging that these alterations may impact the response to CaP treatments such as ADT, radiation therapy, and chemotherapy. Here, we review the contribution of recurring somatic alterations on AR cistrome and transcriptional output and the efficacy of CaP treatments and explore strategies to use these insights to improve treatment plans and outcomes for CaP patients.

Skin rash following Administration of Apalutamide in Japanese patients with Advanced Prostate Cancer: an integrated analysis of the phase 3 SPARTAN and TITAN studies and a phase 1 open-label study

BACKGROUND

A higher incidence of apalutamide-related skin rash has been observed in Japanese patients with prostate cancer (PC).

METHODS

This integrated analysis of data of Japanese patients from 2 global Phase 3 studies, SPARTAN ( NCT01946204 ; patients with non-metastatic castration-resistant PC [nmCRPC]) and TITAN ( NCT02489318 ; patients with metastatic castration-sensitive PC [mCSPC]), and the Phase 1 study 56021927PCR1008 ( NCT02162836 ; patients with metastatic CRPC [mCRPC]), assessed clinical risk factors of apalutamide-related skin rash as well as the potential correlation with plasma exposure to apalutamide. Kaplan-Meier method was used for time-to-event analyses. Clinical risk factors for skin rash were assessed using odds ratio.

RESULTS

Data from 68 patients (SPARTAN: n = 34, TITAN: n = 28, 56021927PCR1008: n = 6) receiving apalutamide 240 mg orally once-daily were analyzed. Rash (13 [19.1%]) and maculo-papular rash (11 [16.2%]) were the most frequently reported skin rash. All Grade and Grade 3 skin rash occurred in 35 (51.5%) and 10 (14.7%) patients, respectively. Most (85.7%) skin rash occurred within 4 months of apalutamide initiation and resolved in a median time of 1 month following the use of antihistamines, topical or systemic corticosteroids, with/without apalutamide dose interruptions/reductions. Median time-to-remission of first incidence of rash and maximum grade incidence of rash were 1.0 month (IQR: 0.36-1.81) and 1.0 month (IQR: 0.30-2.43), respectively. No significant clinical risk factors for the incidence of skin rash were observed. Areas under the curve (0-24 h) (AUC0-24, ss) at steady-state of plasma apalutamide concentration were numerically slightly higher in patients with skin rash than those without.

CONCLUSIONS

No clinical risk factors for rash could be detected. There is a potential correlation between incidence of skin rash and plasma exposure to apalutamide. In general, apalutamide-related skin rash is easily managed, with appropriate treatment with or without dose adjustment.

TRIAL REGISTRATION

Retrospective pooled analysis of NCT01946204 , NCT02489318 , and NCT02162836 .

Association of microRNA-21 expression with clinicopathological characteristics and the risk of progression in advanced prostate cancer patients receiving androgen deprivation therapy

BACKGROUND

Despite androgen deprivation therapy (ADT) remains the mainstay therapy for advanced prostate cancer (PCa), the patients have widely variable durations of response to ADT. Unfortunately, there is limited knowledge of pre-treatment prognostic factors for response to ADT. Recently, microRNA-21 (miR-21) has been reported to play an important role in development of castration resistance of CaP. However, little is known about the expression of miR-21 in advanced PCa biopsy tissues, and data on its potential predictive value in advanced PCa are completely lacking.

METHODS

In this study, paraffin-embedded prostate carcinoma tissues obtained by needle biopsy from 85 advanced PCa patients were evaluated for the expression levels of miR-21 by quantitative real-time PCR (qRT-PCR). In situ hybridization (ISH) analysis was performed to further confirm the qRT-PCR results. Kaplan-Meier analysis and Cox proportional hazards regression models were performed to investigate the correlation between miR-21 expression and time to progression of advanced PCa patients.

RESULTS

Compared with adjacent non-cancerous prostate tissues, the expression level of miR-21 was significantly increased in PCa tissues (PCa vs. non-cancerous prostate: 1.3273 ± 0.3207 vs. 0.9970 ± 0.2054, P < 0.001). By and large, in ISH analysis miR-21 was expressed at a higher level in tumor areas than in adjacent non-cancerous areas. Additionally, PCa patients with higher expression of miR-21 were significantly more likely to be of high Gleason score and high clinical stage (P < 0.05). There was no significant association between miR-21 expression and the initial prostate-specific antigen (PSA) level or age at diagnosis. Moreover, Kaplan-Meier survival analysis found that PCa patients with high miR-21 expression have shorter progression-free survival than those with low miR-21 expression. Furthermore, Multivariate Cox analysis revealed both miR-21 expression status (P = 0.040) and clinical stage (P = 0.042) were all independent predictive factor for progression-free survival for advanced PCa.

CONCLUSION

These findings suggest for the first time that the up-regulation of miR-21 may serve as an independent predictor of progress-free survival in patients with advanced PCa. Prostate 76:986-993, 2016. © 2016 Wiley Periodicals, Inc.

DJ-1 and androgen receptor immunohistochemical expression in prostatic carcinoma: a possible role in carcinogenesis

BACKGROUND AND AIM

Androgen plays a fundamental role in the growth and differentiation of prostate. Androgen receptor (AR) expression may represent a potential marker of prognosis in prostate cancer. However, there have been variable results regarding its ability to predict clinical progression. Despite the oncogenic properties of DJ-1, its significance in prostate cancer development and progression is not well understood. This research shed some light on the possible role of immunohistochemical expression of DJ-1 in clinically localized prostatic carcinoma in relation to the established role of AR and other clinicopathologic parameters.

MATERIALS AND METHODS

The immunohistochemical expression of AR and DJ-1 was evaluated in 129 samples including benign hyperplasia (n = 60) and prostatic carcinoma (n = 69).

RESULTS

The mean value of AR immunostaining was significantly higher in prostatic carcinomas than in benign hyperplasia (P = 0.001). A significant inverse correlation was found between AR immunostaining and the grade of prostatic carcinomas. A significantly higher median DJ-1 score was found in prostatic carcinoma than in benign hyperplasia (P = 0.0001). There was a significant direct correlation between AR and DJ-1 score (P = 0.0001). AR is more sensitive in predicting prostatic carcinoma than DJ-1 but DJ-1 is more specific than AR.

CONCLUSION

AR nuclear expression was consistently present in benign and adenocarcinoma epithelium. But, there may be limited clinical use for AR expression in localized carcinoma due to its constant heterogeneity. DJ-1 with its oncogenic properties, specificity for prostatic carcinoma and homogenous expression gives an ideal complementary role to AR in the detection and treatment of prostatic carcinomas.

Molecular markers in sex hormone pathway genes associated with the efficacy of androgen-deprivation therapy for prostate cancer

Although most advanced prostate cancer patients respond to androgen-deprivation therapy (ADT), the efficacy is widely variable. We investigated whether the host genetic variations in sex hormone pathway genes are associated with the efficacy of ADT. A cohort of 645 patients with advanced prostate cancer treated with ADT was genotyped for 18 polymorphisms across 12 key genes involved in androgen and estrogen metabolism. We found that after adjusting for known risk factors in multivariate Cox regression models, AKR1C3 rs12529 and AR-CAG repeat length remained significantly associated with prostate cancer-specific mortality (PCSM) after ADT (P ≤ 0.041). Furthermore, individuals carrying two unfavorable genotypes at these loci presented a 13.7-fold increased risk of PCSM compared with individuals carrying zero (P<0.001). Our results identify two candidate molecular markers in key genes of androgen and estrogen pathways associated with PCSM after ADT, establishing the role of pharmacogenomics in this therapy.

Prostate cancer: germline prediction for a commonly variable malignancy

What's known on the subject? and What does the study add? Prostate cancer is a heterogeneous disease and biomarkers to predict its incidence and subsequent clinical behaviour are needed to tailor screening, prevention and therapeutic strategies. Rare mutations in genes such as BRCA1, BRCA2 and HOXB13 can affect prostate cancer incidence and/or clinical behaviour. Genome wide association studies (GWAS) have identified more common genetic variations that explain an estimated 20% of familial prostate cancer risk. In this review, we focus on the potential of germline genetic variation to provide biomarkers for prostate cancer screening, prevention and management. We discuss how germline genetics may have a role in treatment selection if reliable pharmacogenetic predictors of efficacy and toxicity can be identified. We have outlined possible mechanisms for including germline investigation in future prostate cancer clinical trials.

OBJECTIVES

• Prostate cancer is a heterogeneous disease and biomarkers to predict its incidence and subsequent clinical behaviour are needed to tailor screening, prevention and therapeutic strategies. • In this review we focus on the potential of germline genetic variation to provide these biomarkers.

METHODS

• We review the published literature on germline genetics in prostate cancer and examine the possibility of including germline genetic biomarkers in future prostate cancer clinical trials.

RESULTS

• Rare mutations in genes such as BRCA1, BRCA2 and HOXB13 can affect prostate cancer incidence and/or clinical behaviour. • Genome-wide association studies (GWAS) have identified more common genetic variations that explain an estimated 20% of familial prostate cancer risk. • Germline genetics may have a role in treatment selection, if reliable pharmacogenetic predictors of efficacy and toxicity can be identified.

CONCLUSION

• This rapidly emerging area of prostate cancer research may provide answers to current clinical conundrums in the prostate cancer treatment paradigm. We have outlined possible mechanisms for including germline investigation in future prostate cancer clinical trial design.

Racial differences in clinical outcome after prostate cancer treatment

Prostate cancer is the number one killer in the United States. A comparison of US and Japanese population is discussed in this chapter to identify risk factors for prostate cancer. Screening of prostate cancer is common among Americans, but not among Japanese. A comparison of survival in different populations is also presented; and prognosis after hormonal treatment in different populations is included.

Glutamine tract length of human androgen receptors affects hormone-dependent and -independent prostate cancer in mice

The androgen receptor (AR) is involved in the initiation and progression of prostate cancer and its transition to androgen independence. Genetic variation in AR may contribute to disease risk and has been studied for a polymorphic N-terminal glutamine (Q) tract that shows population heterogeneity. While the length of this tract is known to affect AR in vitro, association with disease is complicated by genetic and environmental factors that have led to discordant epidemiological findings. To clarify the effect of Q tract polymorphism on prostate cancer, we created mice bearing humanized AR genes (h/mAr) varying in Q tract length. ARs with short Q tracts (12Q), which are transcriptionally more active, induce earlier disease in the transgene-induced TRAMP prostate cancer model than alleles with median (21Q) or long (48Q) tracts. Disease length varies within each genotype, with greater differentiation and AR expression in slower growing tumors. Remarkably, following androgen ablation, Q tract length has effects that are also allele-dependent and in directions opposite to those in hormone intact mice. Differences in AR activity conferred by Q tract length thus appear to direct distinct pathways of androgen-independent as well as androgen-dependent progression, and highlight substantial risk that may be associated with alterations in the androgen axis. This AR allelic series in humanized mice provides an experimental paradigm to dissect the role of AR in prostate cancer initiation and progression, to model response to treatment and to test therapies targeted specifically to the human AR.

Inherited variation in hormone-regulating genes and prostate cancer survival

PURPOSE

Hormonal manipulation is the mainstay treatment of prostate cancer, notably in advanced stages. Despite initial favorably response, the cancer eventually develops hormone resistance resulting in disease progression and death. However, little is known about genetic determinants of disease progression and prostate cancer-specific death.

EXPERIMENTAL DESIGN

We analyzed a population-based cohort comprising 2,761 men diagnosed with prostate cancer from March 2001 to October 2003 and with complete follow-up through July 2006. During a median follow-up time of 3.8 years, a total of 300 men had died from prostate cancer. We genotyped 23 haplotype tagging single nucleotide polymorphisms in the genes AR, CYP17, and SRD5A2 and used Cox proportional hazards analyses to quantify associations between genotype and risk of dying from prostate cancer.

RESULTS

The variant 'A' allele of an AR promoter single nucleotide polymorphism, rs17302090, was borderline associated with a 50% increased risk of dying from prostate cancer (95% confidence interval, 1.0-2.3; P = 0.07). This finding was more pronounced in patients who received hormonal therapy as primary treatment at diagnosis (hazard ratio, 1.9; 95% confidence interval, 1.3-2.9; P = 0.007). We did not identify any associations between CYP17 or SRD5A2 variation and prostate cancer-specific death.

CONCLUSIONS

Our results suggest that inherited genetic variation in the androgen receptor gene affects hormonal treatment response and ultimately prostate cancer death.

Genomic biomarkers, androgen pathway and prostate cancer

Prostate cancer is the most frequent male malignancy diagnosed in western countries and the second leading cause of cancer-related deaths. The growth and function of the prostate gland depends on androgens. Owing to the importance of androgens in prostate development, genes involved in androgen biosynthesis and metabolism have been extensively studied. In this review, we address recent progress toward the use of inherited and acquired genetic variants to predict susceptibility and clinical outcomes of prostate cancer patients. Many of these genetic variants involve several genes related to the biosynthesis and metabolism of androgens, such as steroid-5-α-reductase, α polypeptide 2 (SRD5A2), cytochrome P450 (CYP)19A1, CYP17A1, hydroxy-δ-5-steroid dehydrogenase, 3 β- and steroid δ-isomerase 2 (HSD3B2) and androgen receptor (AR). With increasing knowledge, it may be possible to distinguish indolent from aggressive prostate tumors by molecular fingerprinting. Furthermore, with the emergence of new investigative tools, such as microarray platforms and comparative genomic hybridization (CGH) array, a variety of new genomic biomarkers will be available in the future to provide accurate prognostic and monitoring solutions for individualized patient care.

Phenotypic heterogeneity of mutations in androgen receptor gene

Androgen receptor (AR) gene has been extensively studied in diverse clinical conditions. In addition to the point mutations, trinucleotide repeat (CAG and GGN) length polymorphisms have been an additional subject of interest and controversy among geneticists. The polymorphic variations in triplet repeats have been associated with a number of disorders, but at the same time contradictory findings have also been reported. Further, studies on the same disorder in different populations have generated different results. Therefore, combined analysis or review of the published studies has been of much value to extract information on the significance of variations in the gene in various clinical conditions. AR genetics has been reviewed extensively but until now review articles have focused on individual clinical categories such as androgen insensitivity, male infertility, prostate cancer, and so on. We have made the first effort to review most the aspects of AR genetics. The impact of androgens in various disorders and polymorphic variations in the AR gene is the main focus of this review. Additionally, the correlations observed in various studies have been discussed in the light of in vitro evidences available for the effect of AR gene variations on the action of androgens.

Androgen receptor CAG repeat length contraction in diseased and non-diseased prostatic tissues

To investigate contraction of CAG repeats within the androgen receptor gene (AR) as shorter CAG repeats have been implicated as a possible risk factor in prostate cancer (PCa). AR CAG repeat lengths were analyzed in DNA from microdissected diseased prostates, leukocytes from matched peripheral blood, and control non-diseased prostates. Consistently, all prostatic tissues, whether from benign or cancerous areas of diseased prostates, or from control prostates, showed multiple AR CAG repeat contractions. Germline DNA from blood leukocytes had single CAG repeat lengths in the normal range. AR CAG repeat length contraction may be involved in prostate carcinogenesis and may precede the pathological process.

Expression of human nuclear receptors in plants for the discovery of plant-derived ligands

Plants have the potential to produce a wide array of secondary metabolites that have utility as drugs to treat human diseases. To tap this potential, functional human nuclear receptors have been expressed in plants to create in planta screening assays as a tool to discover natural product ligands. Assays have been designed and validated using 3 nuclear receptors: the estrogen receptor (ER), the androgen receptor (AR), and the heterodimeric retinoid X receptor-alpha plus thyroid hormone receptor-beta (RXRA/THRB). Nuclear receptor-reporter constructs have been expressed in plants to detect the presence of natural ligands that are produced de novo in several plant species during different stages of development, in various tissues, and in response to different stress elicitors. Screening experiments with ER, AR, and RXRA/THRB have been conducted, leading to the identification of plant sources of natural product ligands of human nuclear receptors. This in planta screen has led to the identification of previously unreported ER ligands, providing evidence of the complementary value of this approach to current in vitro high-throughput screening assays.

Comparison of the clinical outcome after hormonal therapy for prostate cancer between Japanese and Caucasian men

OBJECTIVE

To investigate the impact of race on the effectiveness of hormonal therapy in patients with prostate cancer, by comparing the outcomes of Caucasian men (CM) and Japanese-American men (JAM) treated with hormonal therapy at one institution.

PATIENTS AND METHODS

Fifty-nine CM and 105 JAM with prostate cancer were treated with hormonal therapy at The Queen's Medical Center in Honolulu. Age, stage, Gleason score, race, and pretreatment PSA levels were abstracted. The Kaplan-Meier method was used to construct overall and cause-specific survival curves, which were compared using log-rank statistics. These factors were assessed as to their interdependence and correlation with the clinical course using a Cox proportional hazards regression model.

RESULTS

Although there were no statistical differences in patient background, JAM who had received hormonal treatment had a better outcome than CM for overall and cause-specific survival rate (P = 0.001 and 0.036, respectively). Race was one of the significant prognostic factors in the multivariate analysis (P = 0.03). The findings suggest a difference in the effectiveness of hormonal therapy for prostate cancer in JAM living in Hawaii compared to CM.

CONCLUSIONS

There were marked racial differences in clinical outcome after hormonal therapy between JAM and CM. A prospective study with more patients might be necessary to elucidate the differential effectiveness of hormonal therapy for prostate cancer in different races, especially between Japanese and Caucasians.

Common genetic polymorphisms and prognosis of sporadic cancers: prostate cancer as a model

To date, most molecular epidemiological studies on gene polymorphisms in cancer have focused on the risk of development and susceptibility to cancer. However, interindividual genetic variation may contribute greatly to the treatment outcome and prognosis of cancer by affecting the interaction between cancer cells and hormones, growth factors and factors influencing the tumor microenvironment. In prostate cancer, several recent molecular epidemiological studies suggested the possibility of predicting treatment outcome and prognosis using genetic polymorphisms. Candidate genes are hormone-related, oncogenes, tumor-suppressor and cell cycle-growth control-related genes, as well as genes related to immune response, inflammatory change, neovasculization, and the extracellular matrix, genes involved in drug and xenobiotic metabolism and genes involved in DNA repair and genome stability. There remain a huge number of candidate genes whose polymorphisms may affect the progression and treatment outcome of various kinds of cancer, including that of prostate cancer.

Influence of Number of CAG Repeats on Local Control in the RTOG 86-10 Protocol

OBJECTIVES

The number of CAG repeats on the androgen receptor (AR) gene is inversely proportional to transcriptional activity. The purpose of this study was to determine if short-term androgen deprivation therapy (RT + HT) can improve outcome in patients with tumors with short CAG repeats (<19).

MATERIALS AND METHODS

Prostate cancer patients were randomized to receive either radiotherapy (RT) alone or (RT + HT) in the RTOG 86-10 study. CAG repeats were measured in 94 tumor specimens (21%; test cohort) of the 456 (parent cohort) analyzable cases. AR flow cytometry measurements were done on 13 patients. The effect on local failure (LF), distant metastases (DM), prostate cancer survival (PSS), and overall survival (OS) was studied.

RESULTS

Pretreatment characteristics and assigned treatment arm were not significantly different between the parent and test groups except for a significantly higher risk of death (P = 0.049) in the test group. The median CAG repeat was 19. There were no significant differences in stage, or Gleason score between high (19 or greater) and low CAG (<19) patients within each treatment group. Number of CAG repeats alone did not significantly influence LF, DM, PSS, and OS. However, when the CAG repeat outcome was studied in conjunction with androgen deprivation therapy, patients with CAG <19 who received H + RT had improved local control as compared with patients who received RT alone (P = 0.026, 5-year rates 4.6% versus 36.4%) and improved local control over patients with CAG > or =19 that received H + RT (P = 0.028).

CONCLUSIONS

Patients with short CAG repeats show a local control benefit with short-term androgen deprivation therapy, but no improvement in survival.

Polymorphic forms of prostate specific antigen and their interaction with androgen receptor trinucleotide repeats in prostate cancer

BACKGROUND

Recent data has suggested that polymorphisms in the prostate specific antigen (PSA) may increase prostate cancer (PC) risk. The PSA gene contains a G/A substitution in the androgen response element (ARE) 1 region. The androgen receptor (AR) gene has polymorphic regions containing variable length glutamine and glycine repeats and these are believed to be associated with PC risk. The effect on PC risks from PSA polymorphisms alone and synergistically with the AR gene was examined in this report.

METHODS

One hundred PC patients and an age matched cohort of 79 benign prostate hyperplasia and 67 population controls were entered in this study. DNA was extracted from blood and PSA/ARE promoter region amplified by PCR. PCR products were cut with Nhe 1 restriction enzyme to distinguish G/A alleles. AR/CAG and GGC repeat length was detected by automated fluorescence from PCR products.

RESULTS

We found a significantly higher PSA/GG distribution in PC (30%) than either benign prostatic hyperplasia (BPH) (18%) or population controls (16%) (P = 0.025). Furthermore the GG distribution within cases was even greater in younger men (< 65 years; 42%; P = 0.012). Additionally, when PSA genotype was cross classified with CAG repeat, significantly more cases than both BPH and population controls were observed to have a short (< 22) CAG/GG genotype (P = 0.006).

CONCLUSIONS

Our results indicate that the PSA/ARE GG genotype confers an increased risk of PC especially among younger men. Moreover, we confirm previous results that a short glutamine repeat in conjunction with GG genotype significantly increases the risk of malignant disease.

The relationship between the androgen receptor CAG repeat polymorphism length and the response to intermittent androgen suppression therapy for advanced prostate cancer

OBJECTIVE

To determine whether the duration of the off-treatment interval in patients being treated with intermittent androgen deprivation therapy can be predicted by the length of the CAG trinucleotide repeat polymorphism in the androgen receptor.

METHODS

This is a companion study to a prospective randomized trial, NCIC CTG PR-7, comparing intermittent to continuous androgen deprivation therapy in men with PSA progression after radiation therapy. The duration of the first off-treatment interval was established for 76 participants randomized to the intermittent therapy arm of the trial. Androgen receptor CAG repeat polymorphism lengths were determined for these 76 participants. Statistical analysis was completed to determine a relationship between CAG repeat length and the duration of the off-treatment interval.

RESULTS

A significant correlation was not established (P = 0.424) between androgen receptor CAG repeat length and the duration of the first off-treatment interval. Categorical analysis of CAG repeat lengths using 18 and 22 as cutoff points did not find any significant difference in the mean duration of the off-treatment interval between categories (P = 0.672 and 0.774, respectively).

CONCLUSION

No relationship was established between the duration of the first off-treatment interval and the CAG repeat length.

Alterations of androgen receptor in prostate cancer

The significance of androgens in the development of prostate cancer has been known for more than half century. During the last decade, a lot of effort has been put to study the significance of the specific nuclear receptor of the hormone, androgen receptor (AR). It has been suggested that polymorphisms, especially the length of CAG repeat in exon 1 of the gene, are associated with the risk of prostate cancer. However, not all studies have confirmed the association. Most surprisingly, it has now become clear that prostate carcinomas emerging during the androgen withdrawal therapy (i.e. hormone-refractory tumors) are capable of reactivating the AR-mediated signalling despite of the low levels of androgens. In addition, it has been shown that AR gene itself is genetically targeted. One-third of the hormone-refractory prostate carcinomas contains amplification of the gene. In addition, 10-30% of prostate carcinomas treated by antiandrogens acquire point mutation in the AR gene. The genetic alterations in AR indicate that receptor should be considered as putative treatment target. Evidently, the currently available antiandrogens are not capable to abolish the AR-mediated signalling efficiently enough.

How Strong Is the Association Between CAG and GGN Repeat Length Polymorphisms in the Androgen Receptor Gene and Prostate Cancer Risk?

Objective: Although narrative reviews have suggested an association between (CAG)n and (GGN)n polymorphisms in the AR gene and prostate cancer, it has never been quantified systematically. The purpose of this meta-analysis was to provide relative and absolute quantitative summary estimates with sufficient power.

Method: Publications were identified through database searches for epidemiologic studies published until February 2004. For each study, mean differences in repeat length between cases and controls were calculated as well as continuous odds ratios (OR) per one CAG or GGN repeat decrement and discrete ORs to compare prostate cancer risk in men with short CAG repeats (≤21 repeats) versus long CAG repeats (&gt;21 repeats) and short GGN repeats (≤16 repeats) versus long GGN repeats (&gt;16 repeats). The study-specific estimates were combined by random effects metaregression analyses.

Results: Nineteen case-control studies were included in this review comprising a total of 4,274 cases and 5,275 controls. Prostate cancer cases had on average 0.26 fewer CAG repeats and 0.09 fewer GGN repeats than controls. The continuous ORs of prostate cancer per one repeat decrement were 1.02 and 1.01 for CAG and GGN repeats, respectively. The summary discrete OR (95% confidence interval) were 1.19 (1.07-1.31) and 1.31 (1.06-1.61) for CAG and GGN repeat polymorphisms, respectively.

Conclusion: Although the presence of shorter repeats seemed to be modestly associated with prostate cancer risk, the absolute difference in number of repeats between cases and controls is &lt;1 repeat. We question whether such a small difference is enough to yield measurable biological impact in prostate carcinogenesis.

The androgen receptor mRNA

Androgens (testosterone), acting via the androgen receptor (AR) a nuclear transcription factor, regulate male sexual development and body composition. In addition, AR expression plays an important role in the proliferation of human prostate cancer and confers a better prognosis in breast cancer. AR mRNA stability is central to the regulation of AR expression in prostate and breast cancer cells, and recent studies have demonstrated binding by members of the ELAV/Hu and poly(C) RNA-binding protein families to a highly conserved UC-rich element in the 3'-untranslated region of AR mRNA, with functional impact on AR protein expression. Remarkably, a CAG trinucleotide repeat in exon 1 of the AR, the length of which has been linked to prostate cancer survival, is also a target for multiple RNA-binding proteins from a variety of human and murine tissues. In this review, we will detail the current knowledge of the mechanisms involved in regulating AR mRNA stability, the nature, potential role and structural biology of several novel AR mRNA-protein interactions, and the implications for novel therapeutics in human prostate cancer.

Changing trends of prostate cancer in Asia

Although Asian people have the lowest incidence and mortality rates of prostate cancer in the world, these rates have risen rapidly in the past two decades in most Asian countries. Prostate cancer has become one of the leading male cancers in some Asian countries. In 2000, the age-adjusted incidence was over 10 per 100000 men in Japan, Taiwan, Singapore, Malaysia, the Philippines and Israel. Although some of the increases may result from enhanced detection, much of the increased incidence may be associated with westernization of the lifestyle, with increasing obesity and increased consumption of fat. The differences in incidences between native Americans and Asian immigrants are getting smaller, reflecting a possible improvement of diagnostic efforts and changes of environmental risk factors in Asian immigrants. Nevertheless, the huge variations in incidences among ethnic groups imply that there are important genetic risk factors. The stage distributions of prostate cancer in Asian populations are still unfavorable compared to those of Western developed countries. However, a trend towards diagnosing cancer with more favorable prognosis is seen in most Asian countries. Both genetic and environmental risk factors responsible for elevated risks in Asian people are being identified, which may help to reduce prostate cancer incidence in a chemopreventive setting.

In situ shortening of CAG repeat length within the androgen receptor gene in prostatic cancer and its possible precursors

BACKGROUND

The amino-terminal transcriptional activation domain of the androgen receptor (AR) gene contains two polymorphic trinucleotide repeat segments that encode polyglutamine (CAG)n and polyglycine (GGC)n tracts. Shorter CAG repeat lengths are associated with higher transcriptional activity. The previous studies using peripheral blood leukocytes showed the relationship between shorter CAG repeat length and risk for prostate cancer (PCA).

METHODS

Prostatic cancer (PCA), its possible precursors [high grade prostatic intraepithelial neoplasia (HGPIN) and postatrophic hyperplasia (PAH)], and non-neoplastic epithelium were microdissected from a whole-mount prostatectomy specimen from 34 cases with PCA. DNA extracted from each lesion was processed for PCR-based electrophoresis on 6% denaturing polyacrylamide gels, followed by direct sequencing. To examine whether the in situ shortening of CAG repeat was confined to the CAG repeat or was a part of phenomenon induced by microsatelite instability (MSI), BAT-25 and BAT-26, effective markers for detection of MSI, were also examined.

RESULTS

All non-neoplastic epithelial lesions had identical numbers of CAG repeat in the same prostate. CAG repeat lengths were identical in lesions in 25 cases. Two distinct products were found in 9 of 34 cases (26.5%); one product identical to that of non-neoplastic epithelium and another smaller one. In situ shortening of CAG repeat lengths in PCA, HGPIN, and PAH was found in 3 of 34 (8.8%), 6 of 34 (17.6%), and 3 of 10 (30%) cases, respectively. Frequency of CAG shortening was significantly higher in PAH than in PCA lesions (P < 0.05). The length of GGC repeats, BAT-25 and -26 was identical among all lesions in the same case. There was no significant correlation between shortening of CAG repeat length and the clinicopathologic parameters.

CONCLUSION

Shortening of CAG repeat length was found in in situ lesions of PCA and its possible precursors.

Human prostate cancer risk factors

Prostate cancer has the highest prevalence of any nonskin cancer in the human body, with similar likelihood of neoplastic foci found within the prostates of men around the world regardless of diet, occupation, lifestyle, or other factors. Essentially all men with circulating androgens will develop microscopic prostate cancer if they live long enough. This review is a contemporary and comprehensive, literature-based analysis of the putative risk factors for human prostate cancer, and the results were presented at a multidisciplinary consensus conference held in Crystal City, Virginia, in the fall of 2002. The objectives were to evaluate known environmental factors and mechanisms of prostatic carcinogenesis and to identify existing data gaps and future research needs. The review is divided into four sections, including 1) epidemiology (endogenous factors [family history, hormones, race, aging and oxidative stress] and exogenous factors [diet, environmental agents, occupation and other factors, including lifestyle factors]); 2) animal and cell culture models for prediction of human risk (rodent models, transgenic models, mouse reconstitution models, severe combined immunodeficiency syndrome mouse models, canine models, xenograft models, and cell culture models); 3) biomarkers in prostate cancer, most of which have been tested only as predictive factors for patient outcome after treatment rather than as risk factors; and 4) genotoxic and nongenotoxic mechanisms of carcinogenesis. The authors conclude that most of the data regarding risk relies, of necessity, on epidemiologic studies, but animal and cell culture models offer promise in confirming some important findings. The current understanding of biomarkers of disease and risk factors is limited. An understanding of the risk factors for prostate cancer has practical importance for public health research and policy, genetic and nutritional education and chemoprevention, and prevention strategies.

Length and somatic mosaicism of CAG and GGN repeats in the androgen receptor gene and the risk of prostate cancer in men with benign prostatic hyperplasia

BACKGROUND

The most common malignancy in men worldwide is cancer of the prostate and determinants of prostate cancer (PRCa) risk remain largely unidentified. Many candidate genes may be involved in PRCa, such as those that are central to cellular growth and differentiation in the prostate gland. We analysed the polymorphic CAG and GGN repeats sequence in exon 1 of the AR gene to determine if the number of repeats might be an indicator of PRCa risk in patients with BPH.

METHODS

The study evaluated 28 patients who presented with PRCa at least 6 years after the diagnosis of BPH and 56 matched patients with BPH who did not progress to PRCa over a comparable period.

RESULTS

This study showed no evidence for association between the size of AR CAG and GGN repeats and the risk of the development of PRCa in patients with BPH. However, BPH patients with AR CAG instability had a 12-fold increased risk in development of PRCa.

CONCLUSIONS

While independent confirmation is required in further studies, these results provide a potential tool to assist prediction strategies for this important disease.