Prostate cancer epigenetics and its clinical implications

Epigenetic mechanism of therapeutic resistance and potential of epigenetic therapeutics in chemorefractory prostate cancer

Prostate cancer is the second leading cause of cancer death among men in the United States. Depending upon the histopathological subtypes of prostate cancers, various therapeutic options, such as androgen deprivation therapy (ADT), androgen receptor signaling inhibitors (ARSI), immunotherapy, and chemotherapy, are available to treat prostate cancer. While these therapeutics are effective in the initial stages during treatments, the tumors subsequently develop resistance to these therapies. Despite all the progress made so far, therapeutic resistance remains a major challenge in the treatment of prostate cancer. Although various mechanisms have been reported for the resistance development in prostate cancer, altered expression of genes either directly or indirectly involved in drug response pathways is a common event. In addition to the genetic basis of gene regulation such as mutations and gene amplifications, epigenetic alterations involved in the aberrant expression of genes have frequently been shown to be associated not only with cancer initiation and progression but also with therapeutic resistance development. There are several review articles compiling reports on genetic mechanisms involved in therapeutic resistance in prostate cancer. However, epigenetic mechanisms for the therapeutic resistance development in prostate cancer have not yet been summarized in a review article. Therefore, the objective of this article is to compile various reports and provide a comprehensive review of the epigenetic aberrations, and aberrant expression of genes by epigenetic mechanisms involved in CRPCs and therapeutic resistance development in prostate cancer. Additionally, the potential of epigenetic-based therapeutics in the treatment of chemorefractory prostate cancer as evidenced by clinical trials has also been discussed.

Epigenetics in cancer development, diagnosis and therapy

Cancer is a dangerous disease and one of the leading causes of death in the world. In 2020, there were nearly 10 million cancer deaths and approximately 20 million new cases. New cases and deaths from cancer are expected to increase further in the coming years. To have a deeper insight into the mechanism of carcinogenesis, epigenetics studies have been published and received much attention from scientists, doctors, and patients. Among alterations in epigenetics, DNA methylation and histone modification are studied by many scientists. They have been reported to be a major contributor in tumor formation and are involved in metastasis. From the understanding of DNA methylation and histone modification, effective, accurate and cost-effective methods for diagnosis and screening of cancer patients have been introduced. Furthermore, therapeutic approaches and drugs targeting altered epigenetics have also been clinically studied and have shown positive results in combating tumor progression. Several cancer drugs that rely on DNA methylation inactivation or histone modification have been approved by the FDA for the treatment of cancer patients. In summary, epigenetics changes such as DNA methylation or histone modification are take part in tumor growth, and they also have great prospect to study diagnostic and therapeutic methods of this dangerous disease.

Early Cell Cultures from Prostate Cancer Tissue Express Tissue Specific Epithelial and Cancer Markers

Prostate cancer (PCa) is a widespread oncological disease that proceeds in the indolent form in most patients. However, in some cases, the indolent form can transform into aggressive metastatic incurable cancer. The most important task of PCa diagnostics is to search for early markers that can be used for predicting the transition of indolent cancer into its aggressive form. Currently, there are two effective preclinical models to study PCa pathogenesis: patients derived xenografts (PDXs) and patients derived organoids (PDOs). Both models have limitations that restrict their use in research. In this work, we investigated the ability of the primary 2D prostate cell cultures (PCCs) from PCa patients to express epithelial and cancer markers. Early PCCs were formed by epithelial cells that were progressively replaced with the fibroblast-like cells. Early PCCs contained tissue-specific stem cells that could grow in a 3D culture and form PDOs similar to those produced from the prostate tissue. Early PCCs and PDOs derived from the tissues of PCa patients expressed prostate basal and luminal epithelial markers, as well as cancer markers AMACR, TMPRSS2-ERG, and EZH2, the latter being a promising candidate to mark the transition from the indolent to aggressive PCa. We also identified various TMPRSS2-ERG fusion transcripts in PCCs and PDOs, including new chimeric variants resulting from the intra- and interchromosomal translocations. The results suggest that early PCCs derived from cancerous and normal prostate tissues sustain the phenotype of prostate cells and can be used as a preclinical model to study the pathogenesis of PCa.

Evaluation of TET Family Gene Expression and 5-Hydroxymethylcytosine as Potential Epigenetic Markers in Non-small Cell Lung Cancer

BACKGROUND/AIM

DNA methylation is the most studied epigenetic modification in cancer. Ten-eleven translocation enzymes (TET) catalyze the oxidation of 5-methylcytosine (5-mC) to 5-hydroxymethylcytosine (5-hmC) in the DNA. In the current research, we aimed to evaluate the role of 5-hmC and TET enzymes in non-small cell lung cancer (NSCLC) patients and their possible association with outcomes.

PATIENTS AND METHODS

ELISA was used to measure the 5-hmC levels in genomic DNA and qRT-PCR was used to evaluate TET1, TET2, and TET3 mRNAs expression levels in NSCLC tissues and their paired normal controls.

RESULTS

The levels of 5-hmC were significantly lower in NSCLC tissues than in normal tissues, with a mean ±SD of 0.28±0.37 vs. 1.84±0.58, respectively (t=22.77, p<0.0001), and this reduction was correlated with adverse clinical features. In addition, all TET genes were significantly down-regulated in NSCLC tissues in comparison to their matched normal tissues. The mean±SD level of TET1-mRNA was 38.48±16.38 in NSCLC vs. 80.65±11.25 in normal tissues (t=21.33, p<0.0001), TET2-mRNA level in NSCLC was 5.25±2.78 vs. 9.52±1.01 in normal tissues (t=14.48, p<0.0001), and TET3-mRNA level in NSCLC was 5.21±2.8 vs. 9.51±0.86 in normal tissues (t=14.75, p<0.0001). Downregulation of TET genes was correlated with poor clinical features.

CONCLUSION

5-HmC levels as well as TET1, TET2, and TET3 mRNA levels were reduced in NSCLC tissues. The reduced levels of 5-hmC and TET mRNAs were associated with adverse clinical features, suggesting that the level of 5-hmC may serve as a valuable prognostic biomarker for NSCLC.

Investigating the Role of Obesity in Prostate Cancer and Identifying Biomarkers for Drug Discovery: Systems Biology and Deep Learning Approaches

Prostate cancer (PCa) is the second most frequently diagnosed cancer for men and is viewed as the fifth leading cause of death worldwide. The body mass index (BMI) is taken as a vital criterion to elucidate the association between obesity and PCa. In this study, systematic methods are employed to investigate how obesity influences the noncutaneous malignancies of PCa. By comparing the core signaling pathways of lean and obese patients with PCa, we are able to investigate the relationships between obesity and pathogenic mechanisms and identify significant biomarkers as drug targets for drug discovery. Regarding drug design specifications, we take drug–target interaction, drug regulation ability, and drug toxicity into account. One deep neural network (DNN)-based drug–target interaction (DTI) model is trained in advance for predicting drug candidates based on the identified biomarkers. In terms of the application of the DNN-based DTI model and the consideration of drug design specifications, we suggest two potential multiple-molecule drugs to prevent PCa (covering lean and obese PCa) and obesity-specific PCa, respectively. The proposed multiple-molecule drugs (apigenin, digoxin, and orlistat) not only help to prevent PCa, suppressing malignant metastasis, but also result in lower production of fatty acids and cholesterol, especially for obesity-specific PCa.

Histologically benign PI-RADS 4 and 5 lesions contain cancer-associated epigenetic alterations

BACKGROUND

The detection rate of clinically significant prostate cancer has improved with the use of multiparametric magnetic resonance imaging (mpMRI). Yet, even with MRI-guided biopsy 15%-35% of high-risk lesions (Prostate Imaging-Reporting and Data System [PI-RADS] 4 and 5) are histologically benign. It is unclear if these false positives are due to diagnostic/sampling errors or pathophysiological alterations. To better understand this, we tested histologically benign PI-RAD 4 and 5 lesions for common malignant epigenetic alterations.

MATERIALS AND METHODS

MRI-guided in-bore biopsy samples were collected from 45 patients with PI-RADS 4 (n = 31) or 5 (n = 14) lesions. Patients had a median clinical follow-up of 3.8 years. High-risk mpMRI patients were grouped based on their histology into biopsy positive for tumor (BPT; n = 28) or biopsy negative for tumor (BNT; n = 17). From these biopsy samples, DNA methylation of well-known tumor suppressor genes (APC, GSTP1, and RARβ2) was quantified.

RESULTS

Similar to previous work we observed high rates of promoter methylation at GSTP1 (92.7%), RARβ2 (57.3%), and APC (37.8%) in malignant BPT samples but no methylation in benign TURP chips. Interestingly, similar to the malignant samples the BNT biopsies also had increased methylation at the promoter of GSTP1 (78.8%) and RARβ2 (34.6%). However, despite these epigenetic alterations none of these BNT patients developed prostate cancer, and those who underwent repeat mpMRI (n = 8) demonstrated either radiological regression or stability.

CONCLUSIONS

Histologically benign PI-RADS 4 and 5 lesions harbor prostate cancer-associated epigenetic alterations.

Roles of Key Epigenetic Regulators in the Gene Transcription and Progression of Prostate Cancer

Prostate cancer (PCa) is a top-incidence malignancy, and the second most common cause of death amongst American men and the fifth leading cause of cancer death in men around the world. Androgen receptor (AR), the key transcription factor, is critical for the progression of PCa by regulating a series of target genes by androgen stimulation. A number of co-regulators of AR, including co-activators or co-repressors, have been implicated in AR-mediated gene transcription and PCa progression. Epigenetic regulators, by modifying chromatin integrity and accessibility for transcription regulation without altering DNA sequences, influence the transcriptional activity of AR and further regulate the gene expression of AR target genes in determining cell fate, PCa progression and therapeutic response. In this review, we summarized the structural interaction of AR and epigenetic regulators including histone or DNA methylation, histone acetylation or non-coding RNA, and functional synergy in PCa progression. Importantly, epigenetic regulators have been validated as diagnostic markers and therapeutic targets. A series of epigenetic target drugs have been developed, and have demonstrated the potential to treat PCa alone or in combination with antiandrogens.

Distinct DNA methylation patterns associated with treatment resistance in metastatic castration resistant prostate cancer

Androgens are a major driver of prostate cancer (PCa) and continue to be a critical treatment target for advanced disease, which includes castration therapy and antiandrogens. However, resistance to these therapies leading to metastatic castration-resistant prostate cancer (mCRPC), and the emergence of treatment-induced neuroendocrine disease (tNEPC) remains an ongoing challenge. Instability of the DNA methylome is well established as a major hallmark of PCa development and progression. Therefore, investigating the dynamics of the methylation changes going from the castration sensitive to the tNEPC state would provide insights into novel mechanisms of resistance. Using an established xenograft model of CRPC, genome-wide methylation analysis was performed on cell lines representing various stages of PCa progression. We confirmed extensive methylation changes with the development of CRPC and tNEPC using this model. This included key genes and pathways associated with cellular differentiation and neurodevelopment. Combined analysis of methylation and gene expression changes further highlighted genes that could potentially serve as therapeutic targets. Furthermore, tNEPC-related methylation signals from this model were detectable in circulating cell free DNA (cfDNA) from mCRPC patients undergoing androgen-targeting therapies and were associated with a faster time to clinical progression. These potential biomarkers could help with identifying patients with aggressive disease.

Long Noncoding RNA SNHG12 Promotes Prostate Tumor Occurrence and Progression via AKT Regulation

The small nucleolar RNA host gene 12 (SNHG12) has been reported to play an important role in the tumorigenesis and progression of PCa, but the functional underlying mechanism has not been studied clearly. We detected the expression level of SNHG12 in PCa tissues and matched adjacent normal tissues that were collected from 85 patients. Then, colony formation assays, MTT experiments, and flow cytometry were used to examine the effect of SNHG12 on proliferation, cell cycle distribution, and apoptosis of DU145 cells. Further, Transwell invasion assay was utilized to assess whether SNHG12 participates in PCa cell invasion and affects the secretion of VEGF secretion in DU145 cells. Finally, we investigated the effect of SNHG12 on tumor growth in vivo. We found that SNHG12 promoted cell proliferation and suppressed apoptosis in PCa cells, which suggests that SNHG12 is probably a novel PCa biomarker and therapy target of PCa.

Dynamics of the cell-free DNA methylome of metastatic prostate cancer during androgen-targeting treatment

Aim: We examined methylation changes in cell-free DNA (cfDNA) in metastatic castration-resistant prostate cancer (mCRPC) during treatment. Patients & methods: Genome-wide methylation analysis of sequentially collected cfDNA samples derived from mCRPC patients undergoing androgen-targeting therapy was performed. Results: Alterations in methylation states of genes previously implicated in prostate cancer progression were observed and patients that maintained methylation changes throughout therapy tended to have a longer time to clinical progression. Importantly, we also report that markers associated with a highly aggressive form of the disease, neuroendocrine-CRPC, were associated with a faster time to clinical progression. Conclusion: Our findings highlight the potential of monitoring the cfDNA methylome during therapy in mCRPC, which may serve as predictive markers of response to androgen-targeting agents.

Urinary DNA methylation biomarkers for prediction of prostate cancer upgrading and upstaging

BACKGROUND

Significant numbers of prostate cancer (PCa) patients experience tumour upstaging and upgrading in surgical specimens that cause serious problems in timely and proper selection of the treatment strategy. This study was aimed at the evaluation of a set of established epigenetic biomarkers as a noninvasive tool for more accurate PCa categorization before radical prostatectomy (RP).

METHODS

Quantitative methylation-specific PCR was applied for the methylation analysis of RARB, RASSF1, and GSTP1 in 514 preoperatively collected voided or catheterized urine samples from the single-centre cohort of 1056 treatment-naïve PCa patients who underwent RP. The rates of biopsy upgrading and upstaging were analysed in the whole cohort.

RESULTS

Pathological examination of RP specimens revealed Gleason score upgrading in 27.2% and upstaging in 20.3% of the patients with a total misclassification rate of 39.0%. DNA methylation changes in at least one gene were detected in more than 80% of urine samples. Combination of the PSA test with the three-gene methylation analysis in urine was a significant predictor of pathological upstaging and upgrading (P < 0.050), however, with limited increase in overall accuracy. The PSA test or each gene alone was not informative enough.

CONCLUSIONS

The urinary DNA methylation assay in combination with serum PSA may predict tumour stage or grade migration post-RP aiding in improved individual risk assessment and appropriate treatment selection. Clinical utility of these biomarkers should be proven in larger multi-centre studies.

UNC5D, suppressed by promoter hypermethylation, inhibits cell metastasis by activating death-associated protein kinase 1 in prostate cancer

Prostate cancer (PCa) death primarily occurs due to metastasis of the cells, but little is known about the underlying molecular mechanisms. This study aimed to evaluate the expression of UNC5D, a newly identified tumor suppressor gene, analyze its epigenetic alterations, and elucidate its functional relevance to PCa metastasis. Meta‐analysis of publicly available microarray datasets revealed that UNC5D expression was frequently downregulated in PCa tissues and inversely associated with PCa metastasis. These results were verified in clinical specimens by real‐time PCR and immunohistochemistry assays. Through methylation analysis, the downregulated expression of UNC5D in PCa tissues and cell lines was found to be attributable to the hypermethylation of the promoter. A negative correlation was observed between methylation and UNC5D mRNA expression in PCa samples. The ectopic expression of UNC5D in PCa cells effectively reduced their ability to migrate and invade both in vitro and in vivo, and siRNA‐mediated knockdown of UNC5D yielded consistent results. UNC5D can recruit and activate death‐associated protein kinase 1, which remained to be essential for its metastatic suppressor function. In conclusion, these results suggested that UNC5D as a novel putative metastatic suppressor gene that is commonly down‐regulated by hypermethylation in PCa.

Comparing diagnostic and prognostic performance of two-gene promoter methylation panels in tissue biopsies and urines of prostate cancer patients

Background

Prostate cancer (PCa) is one of the most common cancers among men worldwide. Current screening methods for PCa display limited sensitivity and specificity, not stratifying for disease aggressiveness. Hence, development and validation of new molecular markers is needed. Aberrant gene promoter methylation is common in PCa and has shown promise as clinical biomarker. Herein, we assessed and compared the diagnostic and prognostic performance of two-gene panel promoter methylation in the same sample sets.

Methods

Promoter methylation of panel #1 (singleplex-miR-34b/c and miR-193b) and panel #2 (multiplex-APC, GSTP1, and RARβ2) was evaluated using MethyLight methodology in two different cohorts [prostate biopsy (#1) and urine sediment (#2)]. Biomarkers’ diagnostic (validity estimates) and prognostic (disease-specific survival, disease-free survival, and progression-free survival) performance was assessed.

Results

Promoter methylation levels of both panels showed the highest levels in PCa samples in both cohorts. In tissue samples, methylation panel #1 and panel #2 detected PCa with AUC of 0.9775 and 1.0, respectively, whereas in urine samples, panel #2 demonstrated superior performance although a combination of miR-34b/c, miR-193b, APC, and RARβ2 disclosed the best results (AUC = 0.9817). Furthermore, higher mir-34b/c and panel #2 methylation independently predicted for shorter DSS. Furthermore, time-dependent ROC curves showed that both miR-34b/c and GSTP1 methylation levels identify with impressive performance patients that relapse up to 15 years after diagnosis (AUC = 0.751 and AUC = 0.765, respectively).

Conclusions

We concluded that quantitative gene panel promoter methylation might be a clinically useful tool for PCa non-invasive detection and risk stratification for disease aggressiveness in both tissue biopsies and urines.

Electronic supplementary material

The online version of this article (10.1186/s13148-018-0564-2) contains supplementary material, which is available to authorized users.

Genetics and biology of prostate cancer

Despite the high long-term survival in localized prostate cancer, metastatic prostate cancer remains largely incurable even after intensive multimodal therapy. The lethality of advanced disease is driven by the lack of therapeutic regimens capable of generating durable responses in the setting of extreme tumor heterogeneity on the genetic and cell biological levels. Here, we review available prostate cancer model systems, the prostate cancer genome atlas, cellular and functional heterogeneity in the tumor microenvironment, tumor-intrinsic and tumor-extrinsic mechanisms underlying therapeutic resistance, and technological advances focused on disease detection and management. These advances, along with an improved understanding of the adaptive responses to conventional cancer therapies, anti-androgen therapy, and immunotherapy, are catalyzing development of more effective therapeutic strategies for advanced disease. In particular, knowledge of the heterotypic interactions between and coevolution of cancer and host cells in the tumor microenvironment has illuminated novel therapeutic combinations with a strong potential for more durable therapeutic responses and eventual cures for advanced disease. Improved disease management will also benefit from artificial intelligence-based expert decision support systems for proper standard of care, prognostic determinant biomarkers to minimize overtreatment of localized disease, and new standards of care accelerated by next-generation adaptive clinical trials.

Combinatorial strategy of epigenetic and hormonal therapies: A novel promising approach for treating advanced prostate cancer

AIMS

Estrogens act as key factors in prostate biology, cellular proliferation and differentiation as well as cancer development and progression. The expression of estrogen receptor (ER)-β appears to be lost during prostate cancer progression through hypermethylation mechanism. Epigenetic drugs such as 5-aza-2'-deoxycytidine (5-AZAC) and Trichostatin A (TSA) showed efficacy in restoring ERβ expression in prostate cancer cells. This study was designed to explore the potential anti-carcinogenic effects resulting from re-expressing ERβ1 using 5-AZAC and/or TSA, followed by its stimulation with Diarylpropionitrile (DPN), a selective ERβ1 agonist, in prostate cancer cell line PC-3.

MAIN METHODS

Cells were treated with 5-AZAC, TSA, DPN and their combination. Subsequently, they were subjected to proliferation assays, determinations of ERβ1 expression, protein levels of active caspase-3, cyclin D1, β-catenin and VEGF.

KEY FINDINGS

Treatment with these drugs exhibited an increase in ERβ1 expression to different extents as well as active caspase-3 levels. Meanwhile, a significant reduction in cyclin D1, VEGF and β-catenin levels was achieved as compared to the vehicle control group (p < 0.05). Interestingly, the triple combination regimen led to the most prominent anti-tumor responses in terms of increased apoptosis, reduced proliferation as well as angiogenesis.

SIGNIFICANCE

The results support the notion that ERβ1 acts as a tumor suppressor protein and suggest that sequential ERβ1 expression and activation can offer significant anti-tumor responses. The study highlights that the strategy of merging epigenetic and hormonal therapies may be beneficial in treating advanced prostate cancer.

Beyond the androgen receptor II: New approaches to understanding and treating metastatic prostate cancer; Report from the 2017 Coffey-Holden Prostate Cancer Academy Meeting

INTRODUCTION

The 2017 Coffey-Holden Prostate Cancer Academy (CHPCA) Meeting, "Beyond the Androgen Receptor II: New Approaches to Understanding and Treating Metastatic Prostate Cancer," was held in Carlsbad, California from June 14-17, 2017.

METHODS

The CHPCA is an annual scientific conference hosted by the Prostate Cancer Foundation (PCF) that is uniquely designed to produce extensive and constructive discussions on the most urgent and impactful topics concerning research into the biology and treatment of metastatic prostate cancer. The 2017 CHPCA Meeting was the 5th meeting in this annual series and was attended by 71 investigators focused on prostate cancer and a variety of other fields including breast and ovarian cancer.

RESULTS

The discussions at the meeting were concentrated on topics areas including: mechanisms and therapeutic approaches for molecular subclasses of castrate resistant prostate cancer (CRPC), the epigenetic landscape of prostate cancer, the role of DNA repair gene mutations, advancing the use of germline genetics in clinical practice, radionuclides for imaging and therapy, advances in molecular imaging, and therapeutic strategies for successful use of immunotherapy in advanced prostate cancer.

DISCUSSION

This article reviews the presentations and discussions from the 2017 CHPCA Meeting in order to disseminate this knowledge and accelerate new biological understandings and advances in the treatment of patients with metastatic prostate cancer.

Prostate cancer immunotherapy, particularly in combination with androgen deprivation or radiation treatment. Customized pharmacogenomic approaches to overcome immunotherapy cancer resistance

Conventional therapeutic approaches for advanced prostate cancer - such as androgen deprivation, chemotherapy, radiation - come up often against lack of effectiveness because of possible arising of correlative cancer cell resistance and/or inadequate anti-tumor immune conditions. Whence the timeliness of resorting to immune-based treatment strategies including either therapeutic vaccination-based active immunotherapy or anti-tumor monoclonal antibody-mediated passive immunotherapy. Particularly attractive, as for research studies and clinical applications, results to be the cytotoxic T-lymphocyte check point blockade by the use of anti-CTLA-4 and PD-1 monoclonal antibodies, particularly when combined with androgen deprivation therapy or radiation. Unlike afore said immune check point inhibitors, both cell-based (by the use of prostate specific antigen carriers autologous dendritic cells or even whole cancer cells) and recombinant viral vector vaccines are able to induce immune-mediated focused killing of specific antigen-presenting prostate cancer cells. Such vaccines, either used alone or concurrently/sequentially combined with above-mentioned conventional therapies, led to generally reach, in the field of various clinical trials, reasonable results particularly as regards the patient's overall survival. Adoptive trasferred T-cells, as adoptive T-cell passive immunotherapy, and monoclonal antibodies against specific antigen-endowed prostate cancer cells can improve immune micro-environmental conditions. On the basis of a preliminary survey about various immunotherapy strategies, are here also outlined their effects when combined with androgen deprivation therapy or radiation. What's more, as regard the immune-based treatment effectiveness, it has to be pointed out that suitable personalized epigenetic/gene profile-achieved pharmacogenomic approaches to target identified gene aberrations, may lead to overcome - as well as for conventional therapies - possible prostate cancer resistance to immunotherapy.

Cardiovascular assessment for non-cardiac surgery: European guidelines

In 2014, a joint task force involving the European Society of Cardiology and European Society of Anaesthesiology assembled 'Guidelines on non-cardiac surgery: cardiovascular assessment and management'. The guidelines, subsequently published in the European Heart Journal, are intended for physicians and collaborators involved in the perioperative care of patients undergoing non-cardiac surgery, in whom heart disease is a potential source of complications. While the guidelines are an extremely relevant and useful aid for most, if not all, medics within the hospital environment, the sheer size of the document (49 pages) renders it a feat to read and digest. Given the importance of the document for optimizing patient care, this article condenses the guidelines down to help highlight the important details.

Epigenetic Signature: A New Player as Predictor of Clinically Significant Prostate Cancer (PCa) in Patients on Active Surveillance (AS)

Widespread prostate-specific antigen (PSA) testing notably increased the number of prostate cancer (PCa) diagnoses. However, about 30% of these patients have low-risk tumors that are not lethal and remain asymptomatic during their lifetime. Overtreatment of such patients may reduce quality of life and increase healthcare costs. Active surveillance (AS) has become an accepted alternative to immediate treatment in selected men with low-risk PCa. Despite much progress in recent years toward identifying the best candidates for AS in recent years, the greatest risk remains the possibility of misclassification of the cancer or missing a high-risk cancer. This is particularly worrisome in men with a life expectancy of greater than 10–15 years. The Prostate Cancer Research International Active Surveillance (PRIAS) study showed that, in addition to age and PSA at diagnosis, both PSA density (PSA-D) and the number of positive cores at diagnosis (two compared with one) are the strongest predictors for reclassification biopsy or switching to deferred treatment. However, there is still no consensus upon guidelines for placing patients on AS. Each institution has its own protocol for AS that is based on PRIAS criteria. Many different variables have been proposed as tools to enrol patients in AS: PSA-D, the percentage of freePSA, and the extent of cancer on biopsy (number of positive cores or percentage of core involvement). More recently, the Prostate Health Index (PHI), the 4 Kallikrein (4K) score, and other patient factors, such as age, race, and family history, have been investigated as tools able to predict clinically significant PCa. Recently, some reports suggested that epigenetic mapping differs significantly between cancer patients and healthy subjects. These findings indicated as future prospect the use of epigenetic markers to identify PCa patients with low-grade disease, who are likely candidates for AS. This review explores literature data about the potential of epigenetic markers as predictors of clinically significant disease.

Biological function and mechanism of miR-33a in prostate cancer survival and metastasis: via downregulating Engrailed-2

OBJECTIVE

Recent studies have identified Engrailed-2 (EN-2), a homeobox-containing transcription factor, as a candidate oncogene in prostate cancer (PC). Therapeutic targeting on EN-2, however, is limited because the mechanism underlying EN-2 overexpression in prostatic cancer cells is unknown. This study was to investigate the potential regulatory role of miR-33a on EN-2 expression and explore this signaling axis in ability of prostate cancer survival and metastasis.

METHODS

The relative expression of miR-33a and EN-2 in paired prostate cancer tissue and adjacent normal tissue as well as in prostate cancer cell lines, PC3 and DU145, was determined using quantitative real-time PCR or western blot, respectively. Cells survival, migration and invasion were evaluated by assays of MTT, TUNEL and Boyden chamber assays, respectively. Direct regulation of EN-2 by miR-33a was examined by luciferase reporter assay.

RESULTS

The data showed that miR-33a was upregulated and EN-2 was downregulated in both prostate cancer tissue and prostate cancer cells. miR-33a overexpression suppresses prostate cancer cell survival and metastasis. miR-33a can directly act on EN-2 expression by binding to 3'UTR of its mRNA. Also, miR-33a negatively regulated EN-2 mRNA and protein expression. In pcDNA-EN-2 and miR-33a mimic co-transfected PC3 and DU145 cells, EN-2 overexpression reverses the anti-cell survival and metastasis actions of miR-33a overexpression. The pivotal role of miR-33a in inhibiting prostate tumor growth was confirmed in xenograft models of prostate cancer.

CONCLUSION

Our data suggest that the functional interaction of miR-33a and EN-2 is involved in tumorigenesis of prostate cancer. Also in this process EN-2 serves as a negative responder for miR-33a.

Translation of genomics and epigenomics in prostate cancer: progress and promising directions

During the last several years, exciting discoveries have been made in prostate cancer (PCa) as a result of significant advances in genomic technology and information. For example, using genome-wide association studies, more than 100 inherited genetic variants associated with PCa risk have been identified. Similarly, with the use of next-generation sequencing, various types of recurrent somatic DNA alterations in prostate tumors have been revealed. Some of these discoveries have potential clinical application to supplement existing tools for better decision-making regarding the need for screening, biopsy, and treatment of PCa. However, because of the complexity of these genomic findings and incomplete understanding of the genetics of this multifactorial disease, this potential has not yet been fully realized.