MicroRNA let-7c suppresses androgen receptor expression and activity via regulation of Myc expression in prostate cancer cells

Androgen Receptor Is Inactivated and Degraded in Bladder Cancer Cells by Phenyl Glucosamine via miR-449a Restoration

Background

Bladder cancer caused by exposure to aniline dyes, chronic cystitis, and smoking is detected in approximately 70 000 new cases annually. In the USA alone, it leads to 15 000 deaths every year. In the present study, we investigated the role of 3-((4′-amino-[1,1′-biphenyl]-4-yl)amino)-4-bromo-5-oxo-2,5-dihydrofuran-2-yl acetate (ABDHFA) in the inhibition of bladder cancer cell viability.

Material/Methods

Viability of cells was examined using MTT assay and distribution of cell cycle was assessed by flow cytometry. Expression of cyclin D1, androgen, prostate-specific antigen (PSA), and miR-449a was analyzed using Western blot and quantitative real-time polymerase chain reaction assays.

Results

The results demonstrated that ABDHFA treatment inhibited viability of UMUC3 and TCCSUP AR-positive bladder cancer cells. ABDHFA treatment led to break-down of AR in UMUC3 and TCCSUP cells after 48 h in a dose-dependent manner. Up-regulation of miR-449a by lentivirus transfection down-regulated the AR signalling pathway. In UMUC3 and TCCSUP cells, ABDHFA treatment led to inhibition of mRNA and protein expression corresponding to AR.

Conclusions

In summary, the present study demonstrates that proliferation of AR-positive bladder carcinoma cells is markedly reduced by ABDHFA treatment through arrest of cell cycle and degradation of AR protein. Thus, ABDHFA, a novel compound, can be used for the treatment of bladder cancer.

The potential of AR-V7 as a therapeutic target

INTRODUCTION

The androgen receptor variant AR-V7 is gaining attention as a potential predictive marker for as well as one of the resistance mechanisms to the most current anti-androgen receptor (AR) therapies in castration-resistant prostate cancer (CRPC). Accordingly, development of next-generation drugs that directly or indirectly target AR-V7 signaling is urgently needed. Areas covered: We review proposed mechanisms of drug resistance in relation to AR-V7 status, the mechanisms of generation of AR-V7, and its transcriptome, cistrome, and interactome. Pharmacological agents that interfere with these processes are being developed to counteract pan AR and AR-V7-specific signaling. Also, we address the current status of the preclinical and clinical studies targeting AR-V7 signaling. Expert opinion: AR-V7 is considered a true therapeutic target, however, it remains to be determined if AR-V7 is a principal driver or merely a bystander requiring heterodimerization with co-expressed full-length AR or other variants to drive CRPC progression. While untangling AR-V7 biology, multiple strategies are being developed to counteract drug resistance, including selective blockade of AR-V7 signaling as well as inhibition of pan-AR signaling. Ideally anti-AR therapies will be combined with agents preventing activation and enrichment of AR negative tumor cells that are otherwise depressed by AR activity axis.

Lin28A activates androgen receptor via regulation of c-myc and promotes malignancy of ER-/Her2+ breast cancer

Having previously demonstrated the co-expression status of the Lin28A and androgen receptor (AR) in ER−/Her2+ breast cancer, we tested the hypothesis that Lin28A can activate AR and promotes growth of ER−/Her2+ breast cancer. The expression of Lin28A and AR were examined after Lin28A siRNA and Lin28A plasmid were transfected into ER−/Her2+ breast cancer cells. Chromatin immune-precipitation (ChIP) analysis and Luciferase Assays were used to evaluate the effect of Lin28A and c-myc on AR promoter activity. MTT assays, Boyden chamber invasion assays, colony formation assays and flow cytometry analysis were performed. ER−/Her2+ breast cancer cells which transfected with Lin28A siRNAs and Lin28A plasmid were injected into nude mice, and tumorigenesis was monitored. Our data showed that Lin28A can induced AR expression in ER−/Her2+ breast cancer cells. ChIP analysis showed that Lin28A stimulates the recruitment of c-Myc to the promoter of the AR gene. Lin28A enhanced growth ability, colonies ability, cells proliferation activities, invasive ability and inhibited cells apoptosis of ER−/Her2+ breast cancer cells. Lin28A high expression cells exhibited significantly higher tumorigenic ability in vivo. Our study demonstrates that Lin28A can activates androgen receptor via regulation of c-myc and promotes malignancy of ER−/Her2+ breast cancer. Our findings underline a novel role for Lin28A in breast cancer development and activation of the AR axis.

microRNA involvement in the onset and progression of Barrett's esophagus: a systematic review

Esophageal adenocarcinoma (EAC) is a highly aggressive malignancy that develops from Barrett's esophagus (BE), an intestinal metaplasia of the distal esophagus. microRNAs (miRNAs), short non-coding regulatory RNAs, are frequently dysregulated in BE and are thought to play key roles in the onset of BE and its progression to EAC. miRNAs thus have potential diagnostic and prognostic value and are increasingly being used as cancer biomarkers. This review summarizes the current literature related to miRNAs that are dysregulated in BE within the context of Hedgehog, Notch, MAPK, NF kappa-B, Wnt and epithelial-mesenchymal transition (EMT) signaling which are thought to drive BE onset and progression. This comprehensive analysis of miRNAs and their associated signaling in the regulation of BE provides an overview of vital discoveries in this field and highlights gaps in our understanding of BE pathophysiology that warrant further investigation.

Let-7c inhibits migration and epithelial-mesenchymal transition in head and neck squamous cell carcinoma by targeting IGF1R and HMGA2

To elucidate the molecular mechanisms underlying the progression of head and neck squamous cell carcinoma (HNSCC), we investigated the function of let-7c as a tumor suppressor. Let-7c expression was significantly down-regulated in HNSCC tumor tissues and cell lines. In vitro and in vivo studies revealed that let-7c negatively regulated HNSCC proliferation, migration and epithelial–mesenchymal transition (EMT). To explore the underlying mechanisms that affect these molecular events achieved by let-7c, we predicted its target genes. We performed luciferase assay and confirmed that insulin-like growth factor 1 receptor (IGF1R) and high mobility group AT-hook 2 (HMGA2) were the direct targets of let-7c. Knocking down of IGF1R and HMGA2 inhibited HNSCC progression, including proliferation, migration and EMT in HNSCC cells. Re-expression of these genes overcame let-7c–mediated inhibition. Taken together, our finding suggests that let-7c inhibits HNSCC progression by targeting IGF1R and HMGA2 and might be a novel target for HNSCC treatment.

Androgen receptor/let-7a signaling regulates breast tumor-initiating cells

Androgen receptor (AR) is an important transcriptional factor, which is frequently expressed in invasive breast cancer and correlates patients’ prognosis. Our previous results indicate AR activation may increase let-7a expression in breast cancer cells, while let-7, a tumor suppressor, is reported to inhibit breast tumor-initiating cells (T-IC). The study aims to explore the effects of AR/let-7a signaling on breast T-IC and its regulatory mechanism. The results revealed that the expression of AR was significantly associated with let-7a and CD44⁺/24^-/low especially in estrogen receptor positive (ER+) breast cancer tissues. The expression of AR and let-7a indicated better outcome, while patients with CD44⁺/24^-/low phenotype had worse prognosis. AR activation induced by dihydrotestosterone (DHT) prevented cells proliferation, migration, invasion and self-renewal capacities in ER+ breast cancer cells, via transcriptional up-regulation of let-7a. In addition, AR could inhibit tumorigenesis and metastasis of ER+ breast cancer cells in the serial xenotranplanted animal models. Our data suggested that AR/let-7a signaling could inhibit the biological behavior of tumor-initiating cells (T-IC) in ER+AR+ breast cancers, which might become a new therapeutic target.

The potential of microRNAs as human prostate cancer biomarkers: A meta-analysis of related studies

Prostate cancer (PC) is a very important kind of male malignancies. When PC evolves into a stage of hormone resistance or metastasis, the fatality rate is very high. Currently, discoveries and advances in miRNAs as biomarkers have opened the potential for the diagnosis of PC, especially early diagnosis. miRNAs not only can noninvasively or minimally invasively identify PC, but also can provide the data for optimization and personalization of therapy. Moreover, miRNAs have been shown to play an important role to predict prognosis of PC. The purpose of this meta‐analysis is to integrate the currently published expression profile data of miRNAs in PC, and evaluate the value of miRNAs as biomarkers for PC. All of relevant records were selected via electronic databases: Pubmed, Embase, Cochrane, and CNKI based on the assessment of title, abstract, and full text. we extracted mean ± SD or fold change of miRNAs expression levels in PC versus BPH or normal controls. Pooled hazard ratios (HRs) with 95% confidence intervals (CI) for overall survival (OS) and recurrence‐free survival (RFS), were also calculated to detect the relationship between high miRNAs expression and PC prognosis. Selected 104 articles were published in 2007‐2017. According to the inclusion criteria, 104 records were included for this meta‐analysis. The pooled or stratified analyze showed 10 up‐regulated miRNAs (miR‐18a, miR‐34a, miR‐106b, miR‐141, miR‐182, miR‐183, miR‐200a/b, miR‐301a, and miR‐375) and 14 down‐regulated miRNAs (miR‐1, miR‐23b/27b, miR‐30c, miR‐99b, miR‐139‐5p, miR‐152, miR‐187, miR‐204, miR‐205, miR‐224, miR‐452, miR‐505, and let‐7c) had relatively good diagnostic and predictive potential to discriminate PC from BPH/normal controls. Furthermore, high expression of miR‐32 and low expression of let‐7c could be used to differentiate metastatic PC from local/primary PC. Additional interesting findings were that the expression profiles of five miRNAs (miR‐21, miR‐30c, miR‐129, miR‐145, and let‐7c) could predict poor RFS of PC, while the evaluation of miR‐375 was associated with worse OS. miRNAs are important regulators in PC progression. Our results indicate that miRNAs are suitable for predicting the different stages of PC. The detection of miRNAs is an effective way to control patient's prognosis and evaluate therapeutic efficacy. However, large‐scale detections based on common clinical guidelines are still necessary to further validate our conclusions, due to the bias induced by molecular heterogeneity and differences in study design and detection methods.

Differential prognostic value of MYC immunohistochemistry in subtypes of papillary renal cell carcinoma

The histomorphological subtyping of papillary renal cell carcinomas (pRCCs) has improved the predictions of patients' long-term survival. Based on our previous results, we hypothesized that the MYC proto-oncogene would show differential expression in pRCC subtypes. Using a multi-institutional cohort of 204 pRCC patients we assessed the additional value of the immunohistochemical markers MYC, MINA53, and Ki67 in predicting patient's long-term survival. The clinical endpoints were overall survival (OS) and cancer-specific survival (CSS). Nomograms were constructed to predict each patient's risk of death (OS). The incorporation of the MYC staining patterns allowed the stratification of pRCC type 1 patients into better and worse prognostic groups. None of the patients with pRCC type 1 tumors and favorable MYC staining patterns died from tumor-related causes. This prognostic value was independent of the patient's age at surgery, the pathological tumor stage and presence of lymph node invasion. we could show that the immunohistochemical assessment of MYC and the histomorphological subtyping of pRCC stratifies pRCC type 1 tumors with regard to OS and CSS. The determination of the histomorphologic pRCC subtype in combination with the MYC immunohistochemical staining patterns allows a more accurate prediction of patients' individual risk of death.

Feedback circuitry via let-7c between lncRNA CCAT1 and c-Myc is involved in cigarette smoke extract-induced malignant transformation of HBE cells

Cigarette smoking is a primary risk factor for the development of lung cancer, which is regarded as the leading cause of cancer-related deaths. The process of malignant transformation of cells, however, is complex and elusive. The present study investigated the roles of an lncRNA, CCAT1, and a transcriptional factor, c-Myc, in human bronchial epithelial (HBE) cell transformation induced by cigarette smoke extract. With acute and chronic treatment of HBE cells, cigarette smoke extract induced increases of CCAT1 and c-Myc levels and decreases of levels of let-7c, a microRNA. Down-regulation of c-Myc reduced the degree of malignancy and the invasion/migration capacity of HBE cells transformed by cigarette smoke extract. ChIP assays established that c-Myc, increased by cigarette smoke extract, binds to the promoter of CCAT1, activating its transcription. Further, let-7c suppressed the expression of c-Myc through binding to its 3'-UTR. In turn, CCAT1 promoted the accumulation of c-Myc through binding to let-7c and decreasing free let-7c, which influenced the neoplastic capacity of HBE cells transformed by cigarette smoke extract. These results indicate that a positive feedback loop ensures expression of cigarette smoke extract-induced CCAT1 and c-Myc via let-7c, which is involved in cigarette smoke extract-induced malignant transformation of HBE cells. Thus, the present research establishes a new mechanism for the reciprocal regulation between CCAT1 and c-Myc and provides an understanding of cigarette smoke extract-induced lung carcinogenesis.

Implications of microRNA dysregulation in the development of prostate cancer

MicroRNAs (miRNAs) are non-coding small RNAs that target mRNA to reduce protein expression. They play fundamental roles in several diseases, including prostate cancer (PCa). A single miRNA can target hundreds of mRNAs and coordinately regulate them, which implicates them in nearly every biological pathway. Hence, miRNAs modulate proliferation, cell cycle, apoptosis, adhesion, migration, invasion and metastasis, most of them constituting crucial hallmarks of cancer. Due to these properties, miRNAs emerged as promising tools for diagnostic, prognosis and management of cancer patients. Moreover, they come out as potential targets for cancer treatment, and several efforts are being made to progress in the field of miRNA-based cancer therapy. In this review, we will summarize the recent information about miRNAs in PCa. We will recapitulate all the miRNAs involved in the androgen pathway and the biology of PCa, focusing in PCa initiation and progression. In particular, we will describe the miRNAs associated with cell proliferation, cell cycle and apoptosis in PCa, as well as invasion, adhesion and metastatic miRNAs. We will revise the recent progress made understanding the role of circulating miRNAs identified in PCa that might be useful for PCa patient stratification. Another key aspect to be discussed in this review is miRNAs’ role in PCa therapy, including the miRNAs delivery.

Genetic architecture of acne vulgaris

Acne vulgaris is a ubiquitary skin disease characterized by chronic inflammation of the pilosebaceous unit resulting from bacterial colonization of hair follicles by Propionibacterium acnes, androgen-induced increased sebum production, altered keratinization and inflammation. Here, we review our current understanding of the genetic architecture of this intriguing disease. We analysed genomewide association studies (GWAS) and candidate genes studies for acne vulgaris. Moreover, we included GWAS studies for the associated disease polycystic ovary syndrome (PCOS). Overall, the available data revealed sixteen genetic loci flagged by single nucleotide polymorphisms (SNPs), none of which has been confirmed yet by independent studies. Moreover, a GWAS for PCOS identified 21 susceptible loci. The genetic architecture is complex which has been revealed by GWAS. Further and larger studies in different populations are required to confirm or disprove results from candidate gene studies as well to identify signals that may overlap between different populations. Finally, studies on rare genetic variants in acne and associated diseases like PCOS may deepen our understanding of its pathogenesis.

Tissue-Based MicroRNAs as Predictors of Biochemical Recurrence after Radical Prostatectomy: What Can We Learn from Past Studies?

With the increasing understanding of the molecular mechanism of the microRNAs (miRNAs) in prostate cancer (PCa), the predictive potential of miRNAs has received more attention by clinicians and laboratory scientists. Compared with the traditional prognostic tools based on clinicopathological variables, including the prostate-specific antigen, miRNAs may be helpful novel molecular biomarkers of biochemical recurrence for a more accurate risk stratification of PCa patients after radical prostatectomy and may contribute to personalized treatment. Tissue samples from prostatectomy specimens are easily available for miRNA isolation. Numerous studies from different countries have investigated the role of tissue-miRNAs as independent predictors of disease recurrence, either alone or in combination with other clinicopathological factors. For this purpose, a PubMed search was performed for articles published between 2008 and 2017. We compiled a profile of dysregulated miRNAs as potential predictors of biochemical recurrence and discussed their current clinical relevance. Because of differences in analytics, insufficient power and the heterogeneity of studies, and different statistical evaluation methods, limited consistency in results was obvious. Prospective multi-institutional studies with larger sample sizes, harmonized analytics, well-structured external validations, and reasonable study designs are necessary to assess the real prognostic information of miRNAs, in combination with conventional clinicopathological factors, as predictors of biochemical recurrence.

Significance of microRNAs in Androgen Signaling and Prostate Cancer Progression

The androgen receptor (AR) plays important roles in prostate cancer development and prostate tumor growth. After binding to androgens, AR functions as a nuclear receptor and translocates to the nucleus to bind to specific AR-binding sites (ARBSs). AR regulates epigenetic factor recruitments to activate its downstream signaling. Although androgen deprivation therapy (ADT) is initially useful for prostate cancer patients, most patients eventually show resistance with hormone-refractory prostate cancers (HRPCs) or castration-resistant prostate cancers (CRPCs). Thus, new therapeutic strategies targeting HRPCs/CRPCs should be very important for clinical medicine as well as prostate cancer biology. Past studies have shown that mechanisms such as AR overexpression, hypersensitivity, variants and reprograming are responsible for developing HRPCs/CRPCs. These findings suggest that AR target genes will be major key factors. In this review article, we focus mainly on the androgen-regulated microRNAs (miRNAs) to summarize the contribution of miRNA-mediated pathways for prostate cancer progression.

Downregulation of miR-99a/let-7c/miR-125b miRNA cluster predicts clinical outcome in patients with unresected malignant pleural mesothelioma

Malignant pleural mesothelioma (MPM) is an aggressive tumor with a dismal overall survival (OS) and to date no molecular markers are available to guide patient management. This study aimed to identify a prognostic miRNA signature in MPM patients who did not undergo tumor resection. Whole miRNA profiling using a microarray platform was performed using biopsies on 27 unresected MPM patients with distinct clinical outcome: 15 patients had short survival (OS<12 months) and 12 patients had long survival (OS>36 months). Three prognostic miRNAs (mir-99a, let-7c, and miR-125b) encoded at the same cluster (21q21) were selected for further validation and tested on publicly available miRNA sequencing data from 72 MPM patients with survival data. A risk model was built based on these 3 miRNAs that was validated by quantitative PCR in an independent set of 30 MPM patients. High-risk patients had shorter median OS (7.6 months) as compared with low-risk patients (median not reached). In the multivariate Cox model, a high-risk score was independently associated with shorter OS (HR=3.14; 95% CI, 1.18–8.34; P=0.022). Our study identified that the downregulation of the miR-99a/let-7/miR-125b miRNA cluster predicts poor outcome in unresected MPM.

Resveratrol and pterostilbene as a microRNA-mediated chemopreventive and therapeutic strategy in prostate cancer

Growing evidence indicates that deregulation of the epigenetic machinery comprising the microRNA (miRNA) network is a critical factor in the progression of various diseases, including cancer. Concurrently, dietary phytochemicals are being intensively studied for their miRNA-mediated health-beneficial properties, such as anti-inflammatory, cardioprotective, antioxidative, and anticancer properties. Available experimental data have suggested that dietary polyphenols may be effective miRNA-modulating chemopreventive and therapeutic agents. Moreover, noninvasive detection of changes in miRNA expression in liquid biopsies opens enormous possibilities for their clinical utilization as novel prognostic and predictive biomarkers. In our published studies, we identified resveratrol-regulated miRNA profiles in prostate cancer. Resveratrol downregulated the phosphatase and tensin homolog (PTEN)-targeting members of the oncogenic miR-17 family of miRNAs, which are overexpressed in prostate cancer. We have functionally validated the miRNA-mediated ability of resveratrol and its potent analog pterostilbene to rescue the tumor suppressor activity of PTEN in vitro and in vivo. Taken together, our findings implicate the use of resveratrol and its analogs as an attractive miRNA-mediated chemopreventive and therapeutic strategy in prostate cancer and the use of circulating miRNAs as potential predictive biomarkers for clinical development.

A Downmodulated MicroRNA Profiling in Patients with Gastric Cancer

Objective. Here, we aim to investigate the microRNA (miR) profiling in human gastric cancer (GC). Methods. Tumoral and matched peritumoral gastric specimens were collected from 12 GC patients who underwent routine surgery. A high-throughput miR sequencing method was applied to detect the aberrantly expressed miRs in a subset of 6 paired samples. The stem-loop quantitative real-time polymerase chain reaction (qRT-PCR) assay was subsequently performed to confirm the sequencing results in the remaining 6 paired samples. The profiling results were also validated in vitro in three human GC cell lines (BGC-823, MGC-803, and GTL-16) and a normal gastric epithelial cell line (GES-1). Results. The miR sequencing approach detected 5 differentially expressed miRs, hsa-miR-132-3p, hsa-miR-155-5p, hsa-miR-19b-3p, hsa-miR-204-5p, and hsa-miR-30a-3p, which were significantly downmodulated between the tumoral and peritumoral GC tissues. Most of the results were further confirmed by qRT-PCR, while no change was observed for hsa-miR-30a-3p. The in vitro finding also agreed with the results of both miR sequencing and qRT-PCR for hsa-miR-204-5p, hsa-miR-155-5p, and hsa-miR-132-3p. Conclusion. Together, our findings may serve to identify new molecular alterations as well as to enrich the miR profiling in human GC.

MicroRNA expression and function in prostate cancer: a review of current knowledge and opportunities for discovery

MicroRNAs (miRNAs) are well-conserved noncoding RNAs that broadly regulate gene expression through posttranscriptional silencing of coding genes. Dysregulated miRNA expression in prostate and other cancers implicates their role in cancer biology. Moreover, functional studies provide support for the contribution of miRNAs to several key pathways in cancer initiation and progression. Comparative analyses of miRNA gene expression between malignant and nonmalignant prostate tissues, healthy controls and prostate cancer (PCa) patients, as well as less aggressive versus more aggressive disease indicate that miRNAs may be future diagnostic or prognostic biomarkers in tumor tissue, blood, or urine. Further, miRNAs may be future therapeutics or therapeutic targets. In this review, we examine the miRNAs most commonly observed to be de-regulated in PCa gene expression analyses and review the potential contribution of these miRNAs to important pathways in PCa initiation and progression.

p62/SQSTM1 enhances breast cancer stem-like properties by stabilizing MYC mRNA

Aberrant p62 overexpression has been implicated in breast cancer development. Here, we found that p62 expression was elevated in breast cancer stem cells (BCSCs), including CD44⁺CD24^- fractions, mammospheres, ALDH1⁺ populations and side population cells. Indeed, short-hairpin RNA (shRNA)-mediated knockdown of p62 impaired breast cancer cells from self-renewing under anchorage-independent conditions, whereas ectopic overexpression of p62 enhanced the self-renewal ability of breast cancer cells in vitro. Genetic depletion of p62 robustly inhibited tumor-initiating frequencies, as well as growth rates of BCSC-derived tumor xenografts in immunodeficient mice. Consistently, immunohistochemical analysis of clinical breast tumor tissues showed that high p62 expression levels were linked to poorer clinical outcome. Further gene expression profiling analysis revealed that p62 was positively correlated with MYC expression level, which mediated the function of p62 in promoting breast cancer stem-like properties. MYC mRNA level was reduced upon p62 deletion by siRNA and increased with p62 overexpression in breast cancer cells, suggesting that p62 positively regulated MYC mRNA. Interestingly, p62 did not transactivate MYC promoter. Instead, p62 delayed the degradation of MYC mRNA by repressing the expression of let-7a and let-7b, thus promoting MYC mRNA stabilization at the post-transcriptional level. Consistently, let-7a and let-7b mimics attenuated p62-mediated MYC mRNA stabilization. Together, these findings unveiled a previously unappreciated role of p62 in the regulation of BCSCs, assigning p62 as a promising therapeutic target for breast cancer treatments.

Epigenomic Regulation of Androgen Receptor Signaling: Potential Role in Prostate Cancer Therapy

Androgen receptor (AR) signaling remains the major oncogenic pathway in prostate cancer (PCa). Androgen-deprivation therapy (ADT) is the principle treatment for locally advanced and metastatic disease. However, a significant number of patients acquire treatment resistance leading to castration resistant prostate cancer (CRPC). Epigenetics, the study of heritable and reversible changes in gene expression without alterations in DNA sequences, is a crucial regulatory step in AR signaling. We and others, recently described the technological advance Chem-seq, a method to identify the interaction between a drug and the genome. This has permitted better understanding of the underlying regulatory mechanisms of AR during carcinogenesis and revealed the importance of epigenetic modifiers. In screening for new epigenomic modifiying drugs, we identified SD-70, and found that this demethylase inhibitor is effective in CRPC cells in combination with current therapies. The aim of this review is to explore the role of epigenetic modifications as biomarkers for detection, prognosis, and risk evaluation of PCa. Furthermore, we also provide an update of the recent findings on the epigenetic key processes (DNA methylation, chromatin modifications and alterations in noncoding RNA profiles) involved in AR expression and their possible role as therapeutic targets.

Defining Transcriptional Regulatory Mechanisms for Primary let-7 miRNAs

The let-7 family of miRNAs have been shown to control developmental timing in organisms from C. elegans to humans; their function in several essential cell processes throughout development is also well conserved. Numerous studies have defined several steps of post-transcriptional regulation of let-7 production; from pri-miRNA through pre-miRNA, to the mature miRNA that targets endogenous mRNAs for degradation or translational inhibition. Less-well defined are modes of transcriptional regulation of the pri-miRNAs for let-7. let-7 pri-miRNAs are expressed in polycistronic fashion, in long transcripts newly annotated based on chromatin-associated RNA-sequencing. Upon differentiation, we found that some let-7 pri-miRNAs are regulated at the transcriptional level, while others appear to be constitutively transcribed. Using the Epigenetic Roadmap database, we further annotated regulatory elements of each polycistron identified putative promoters and enhancers. Probing these regulatory elements for transcription factor binding sites identified factors that regulate transcription of let-7 in both promoter and enhancer regions, and identified novel regulatory mechanisms for this important class of miRNAs.

Different levels of serum microRNAs in prostate cancer and benign prostatic hyperplasia: evaluation of potential diagnostic and prognostic role

Introduction

Diagnosis of prostate cancer (PCa) is based on prostate biopsy that is performed when prostate specific antigen (PSA) is persistently altered over time and/or abnormal digital rectal examination is found. Serum PSA levels increase in both PCa and benign prostatic hyperplasia, leading to an increased number of unnecessary biopsies. There is an urgent need to unravel PCa-specific molecular signatures.

Patients and methods

This study aimed at characterizing a panel of circulating micro RNAs (miRNAs) that could distinguish PCa from benign prostatic hyperplasia in a population of age-matched patients with increased PSA levels. Both miRNAs targeting genes involved in PCa onset and miRNAs whose role in PCa has been highlighted in other studies were included. For this purpose, let-7c, let-7e, let-7i, miR-26a-5p, miR-26b-5p, miR-24-3p, miR-23b-3p, miR-27-b-3p, miR-106a-5p, miR-20b-5p, miR-18b-5p, miR-19b-2-5p, miR-363-3p, miR-497, miR-195, miR-25-3p, miR-30c-5p, miR-622, miR-874-3p, miR-346 and miR-940 were assayed through real-time PCR in 64 patients with PCa and compared with 60 patients with benign prostatic hyperplasia. The ability of miRNAs to predict the stage of disease was also analyzed.

Results

Let-7c, let-7e, let-7i, miR-26a-5p, miR-26b-5p, miR-18b-5p and miR-25-3p were able to discriminate patients with PCa from those harboring benign prostatic hyperplasia, both presenting altered PSA levels (>3 ng/mL). MiR-25-3p and miR-18b-5p showed the highest sensitivity and specificity to predict PCa, respectively. The combination of these two miRNAs improved the overall sensitivity. A correlation between pathological Gleason score and miRNA expression levels was reported; miR-363-3p, miR-26a-5p, miR-26b-5p, miR-106a-5p, miR-18b-5p, miR-25-3p and let-7i decreased in expression concomitantly with an increase in malignancy.

Conclusion

This study confirms serum miRNAs to be reliable candidates for the development of minimally invasive biomarkers for the diagnosis and prognosis of PCa, particularly in those cases where PSA acts as a flawed marker.

The roles of microRNAs in the progression of castration-resistant prostate cancer

Prostate cancer (PCa) is one of the leading causes of cancer-related death in men. PCa is androgen-dependent, and androgen-deprivation therapy is effective for first-line hormonal treatment, but the androgen-independent phenotype of PCa eventually develops, which is difficult to treat and has no effective cure. Recently, microRNAs have been discovered to have important roles in the initiation and progression of PCa, suggesting their use in diagnosis, predicting prognosis and development of treatment for castration-resistant PCa (CRPC). Understanding the networks of microRNAs and their target genes is necessary to ascertain their roles and importance in the development and progression of PCa. This review summarizes the current knowledge about microRNAs regulating PCa progression and elucidates the mechanism of progression to CRPC.

Let-7c miRNA Inhibits the Proliferation and Migration of Heat-Denatured Dermal Fibroblasts Through Down-Regulating HSP70

Wound healing is a complex physiological process necessitating the coordinated action of various cell types, signals and microRNAs (miRNAs). However, little is known regarding the role of miRNAs in mediating this process. In the present study, we show that let-7c miRNA is decreased in heat-denatured fibroblasts and that inhibiting let-7c expression leads to the increased proliferation and migration of dermal fibroblasts, whereas the overexpression of let-7c exerts an opposite effect. Further investigation has identified heat shock protein 70 as a direct target of let-7c and has demonstrated that the expression of HSP70 in fibroblasts is negatively correlated with let-7c levels. Moreover, down-regulation of let-7c expression is accompanied by up-regulation of Bcl-2 expression and down-regulation of Bax expression, both of which are the downstream genes of HSP70. Notably, the knockdown of HSP70 by HSP70 siRNA apparently abrogates the stimulatory effect of let-7c inhibitor on heat-denatured fibroblasts proliferation and migration. Overall, we have identified let-7c as a key regulator that inhibits fibroblasts proliferation and migration during wound healing.

The insights of Let-7 miRNAs in oncogenesis and stem cell potency

The ability of the classic tumour‐suppressive let‐7 family to inhibit carcinogenesis, tumour progression, recurrence and pluripotency of cancer stem cells has generated significant interest in the field of cancer research. Through suppressing and degrading downstream‐targeted mRNAs, let‐7 affected most aspects of cell biology. It is perplexing how let‐7 affects oncogenesis, as the large influx of new miRNAs and other kinds of non‐coding RNAs are continuously defined. In this review, we delineate the complex functions of let‐7 and discuss the future direction of let‐7 research.

Lin28 induces resistance to anti-androgens via promotion of AR splice variant generation

BACKGROUND

Prostate cancer (PCa) is androgen-dependent initially and progresses to a castration-resistant state after androgen deprivation therapy. Treatment options for castration-resistant PCa include the potent second-generation anti-androgen enzalutamide or CYP17A1 inhibitor abiraterone. Recent clinical observations point to the development of resistance to these therapies which may be mediated by constitutively active alternative splice variants of the androgen receptor (AR).

METHODS

Sensitivity of LNCaP cells overexpressing Lin28 (LN-Lin28) to enzalutamide, abiraterone, or bicalutamide was compared to that of control LN-neo cells using cell growth assays, proliferation assays using MTT, anchorage-dependent clonogenic ability assays and soft agar assays. Ability of LN-Lin28 cells to maintain AR activation after treatment with enzalutamide, abiraterone, or bicalutamide was tested using immunofluorescence, Western blotting, ChIP assays, and qRT-PCR. Importance of Lin28 in enzalutamide resistance was assessed by the downregulation of Lin28 expression in C4-2B and 22Rv1 cells chronically treated with enzalutamide. Requirement for sustained AR signaling in LN-Lin28 cells was examined by the downregulation of either full length AR or AR-V7 using siRNA.

RESULTS

We show that Lin28 promotes the development of resistance to currently used targeted therapeutics by enhancing the expression of AR splice variants such as AR-V7. PCa cells overexpressing Lin28 exhibit resistance to treatment with enzalutamide, abiraterone, or bicalutamide. Downregulation of Lin28 resensitizes enzalutamide-resistant PCa cells to enzalutamide treatment. We also show that the upregulation of splicing factors such as hnRNPA1 by Lin28 may mediate the enhanced generation of AR splice variants in Lin28-expressing cells.

CONCLUSIONS

Our findings suggest that Lin28 plays a key role in the acquisition of resistance to AR-targeted therapies by PCa cells and establish the importance of Lin28 in PCa progression.

Disrupting LIN28 in atypical teratoid rhabdoid tumors reveals the importance of the mitogen activated protein kinase pathway as a therapeutic target

Atypical teratoid rhabdoid tumor (AT/RT) is among the most fatal of all pediatric brain tumors. Aside from loss of function mutations in the SMARCB1 (BAF47/INI1/SNF5) chromatin remodeling gene, little is known of other molecular drivers of AT/RT. LIN28A and LIN28B are stem cell factors that regulate thousands of RNAs and are expressed in aggressive cancers. We identified high-levels of LIN28A and LIN28B in AT/RT primary tumors and cell lines, with corresponding low levels of the LIN28-regulated microRNAs of the let-7 family. Knockdown of LIN28A by lentiviral shRNA in the AT/RT cell lines CHLA-06-ATRT and BT37 inhibited growth, cell proliferation and colony formation and induced apoptosis. Suppression of LIN28A in orthotopic xenograft models led to a more than doubling of median survival compared to empty vector controls (48 vs 115 days). LIN28A knockdown led to increased expression of let-7b and let-7g microRNAs and a down-regulation of KRAS mRNA. AT/RT primary tumors expressed increased mitogen activated protein (MAP) kinase pathway activity, and the MEK inhibitor selumetinib (AZD6244) decreased AT/RT growth and increased apoptosis. These data implicate LIN28/RAS/MAP kinase as key drivers of AT/RT tumorigenesis and indicate that targeting this pathway may be a therapeutic option in this aggressive pediatric malignancy.

Mechanisms of resistance in castration-resistant prostate cancer (CRPC)

Despite advances in prostate cancer diagnosis and management, morbidity from prostate cancer remains high. Approximately 20% of men present with advanced or metastatic disease, while 29,000 men continue to die of prostate cancer each year. Androgen deprivation therapy (ADT) has been the standard of care for initial management of advanced or metastatic prostate cancer since Huggins and Hodges first introduced the concept of androgen-dependence in 1972, but progression to castration-resistant prostate cancer (CRPC) occurs within 2-3 years of initiation of ADT. CRPC, previously defined as hormone-refractory prostate cancer, is now understood to still be androgen dependent. Multiple mechanisms of resistance help contribute to the progression to castration resistant disease, and the androgen receptor (AR) remains an important driver in this progression. These mechanisms include AR amplification and hypersensitivity, AR mutations leading to promiscuity, mutations in coactivators/corepressors, androgen-independent AR activation, and intratumoral and alternative androgen production. More recently, identification of AR variants (ARVs) has been established as another mechanism of progression to CRPC. Docetaxel chemotherapy has historically been the first-line treatment for CRPC, but in recent years, newer agents have been introduced that target some of these mechanisms of resistance, thereby providing additional survival benefit. These include AR signaling inhibitors such as enzalutamide (Xtandi, ENZA, MDV-3100) and CYP17A1 inhibitors such as abiraterone acetate (Zytiga). Ultimately, these agents will also fail to suppress CRPC. While some of the mechanisms by which these agents fail are unique, many share similarities to the mechanisms contributing to CRPC progression. Understanding these mechanisms of resistance to ADT and currently approved CRPC treatments will help guide future research into targeted therapies.

The role of microRNAs in prostate cancer progression

Prostate cancer (PCa) is the most common male malignancy and the second highest cause of cancer-related mortality in United States. MicroRNAs (miRNAs) are small non-coding RNAs that represent a new mechanism to regulate mRNA post-transcriptionally. It is involved in diverse physiological and pathophysiological process. Dysregulation of miRNAs has been associated with the multistep progression of PCa from prostatic intraepithelial neoplasia (PIN), localized adenocarcinoma to metastatic castration-resistance PCa (CRPC). Identification of unique miRNA could provide new biomarkers for PCa and develop into therapeutic strategies. In this review, we will summarize a broad spectrum of both tumor suppressive and oncogenic miRNAs, and their mechanisms contribute to prostate carcinogenesis.

Lin28: an emerging important oncogene connecting several aspects of cancer

RNA-binding protein Lin28 was originally found as a heterochronic gene which played a significant role in the development of Caenorhabditis elegans. The tumor suppressor let-7 is a downstream target of Lin28, which has a wide variety of target genes which are involved in many aspects of cellular activities. By inhibition of let-7 and directly binding the target RNAs, Lin28 plays an important role in different biological and pathological processes including differentiation, metabolism, proliferation, pluripotency, and tumorigenesis. Overexpression of Lin28 has been reported in several kinds of cancers and is correlated with poor outcomes. It has been shown that Lin28 could affect the progression of cancers in several ways, such as promoting proliferation, increasing glucose metabolism, and inducing epithelial-mesenchymal transition (EMT) and cancer stem cells. Decrease of Lin28 expression or reactivation of let-7 in cancer cells could induce a reverse effect, indicating their therapeutic values in developing novel strategies for cancer treatment. Here, we will overview the regulatory mechanisms and functions of Lin28 in cancers.

Role of microRNAs in the resistance of prostate cancer to docetaxel and paclitaxel

Taxanes, a group of cancer drugs that includes docetaxel and paclitaxel, have become a front-line therapy for a variety of metastatic cancers, but resistance can develop.

There are several docetaxel resistance mechanisms in prostate cancer: unfavorable tumor microenvironment, drug efflux pump, alterations in microtubule structure and/or function, and apoptotic defects (e.g. up regulation of Bcl-2 and clusterin or activation of the PTEN/PI3K/mTOR pathway or activation of the MAPK/ERK pathway).

MicroRNAs (miRNAs), small regulatory molecules, could also function as a contributor to the resistance of cancer cells to commonly used anti-cancer drugs.

Aberrant expressions of miRNAs that can act as tumor suppressors or oncogenes are closely associated with the development, invasion and metastasis of various cancers including prostate cancer. Nearly 50 miRNAs have been reported to be differentially expressed in human prostate cancer so far, but knowledge concerning the effects of miRNAs on the sensitivity to anti-cancer drugs is still limited. The author of the review focus on probable impact of miRNAs on the resistance to docetaxel and paclitaxel.

Overexpression of miR-21 increased the resistance of prostate cancer cells to docetaxel by targeting PDCD4, PTEN, RECK, and BTG2. Nevertheless, decreased expressions of tumor suppressors: miR-34a, miR-143, miR-148a and miR-200 family are involved in resistance of anti-cancer drugs by inhibition of apoptosis and activation of signaling pathways. Conclude miRNAs become very attractive target for potential therapeutic interventions.

Deep sequencing of small RNA libraries from human prostate epithelial and stromal cells reveal distinct pattern of microRNAs primarily predicted to target growth factors

Complex epithelial and stromal cell interactions are required during the development and progression of prostate cancer. Regulatory small non-coding microRNAs (miRNAs) participate in the spatiotemporal regulation of messenger RNA (mRNA) and regulation of translation affecting a large number of genes involved in prostate carcinogenesis. In this study, through deep-sequencing of size fractionated small RNA libraries we profiled the miRNAs of prostate epithelial (PrEC) and stromal (PrSC) cells. Over 50 million reads were obtained for PrEC in which 860,468 were unique sequences. Similarly, nearly 76 million reads for PrSC were obtained in which over 1 million were unique reads. Expression of many miRNAs of broadly conserved and poorly conserved miRNA families were identified. Sixteen highly expressed miRNAs with significant change in expression in PrSC than PrEC were further analyzed in silico. ConsensusPathDB showed the target genes of these miRNAs were significantly involved in adherence junction, cell adhesion, EGRF, TGF-β and androgen signaling. Let-7 family of tumor-suppressor miRNAs expression was highly pervasive in both, PrEC and PrSC cells. In addition, we have also identified several miRNAs that are unique to PrEC or PrSC cells and their predicted putative targets are a group of transcription factors. This study provides perspective on the miRNA expression in PrEC and PrSC, and reveals a global trend in miRNA interactome. We conclude that the most abundant miRNAs are potential regulators of development and differentiation of the prostate gland by targeting a set of growth factors. Additionally, high level expression of the most members of let-7 family miRNAs suggests their role in the fine tuning of the growth and proliferation of prostate epithelial and stromal cells.

Oxidative stress response and Nrf2 signaling in aging

Increasing oxidative stress, a major characteristic of aging, has been implicated in a variety of age-related pathologies. In aging, oxidant production from several sources is increased, whereas antioxidant enzymes, the primary lines of defense, are decreased. Repair systems, including the proteasomal degradation of damaged proteins, also decline. Importantly, the adaptive response to oxidative stress declines with aging. Nrf2/EpRE signaling regulates the basal and inducible expression of many antioxidant enzymes and the proteasome. Nrf2/EpRE activity is regulated at several levels, including transcription, posttranslation, and interactions with other proteins. This review summarizes current studies on age-related impairment of Nrf2/EpRE function and discusses the changes in Nrf2 regulatory mechanisms with aging.

Testicular expression of the Lin28/let-7 system: Hormonal regulation and changes during postnatal maturation and after manipulations of puberty

The Lin28/let-7 system, which includes the RNA-binding proteins, Lin28a/Lin28b, and let-7 miRNAs, has emerged as putative regulator of puberty and male gametogenesis; yet, its expression pattern and regulation in postnatal testis remain ill defined. We report herein expression profiles of Lin28 and let-7 members, and related mir-145 and mir-132, in rat testis during postnatal maturation and in models of altered puberty and hormonal deregulation. Neonatal expression of Lin28a and Lin28b was low and rose markedly during the infantile period; yet, expression patterns diverged thereafter, with persistently elevated levels only for Lin28b, which peaked at puberty. Let-7a, let-7b, mir-132 and mir-145 showed profiles opposite to Lin28b. In fact, let-7b and mir-145 were abundant in pachytene spermatocytes, but absent in elongating spermatids, where high expression of Lin28b was previously reported. Perturbation of puberty by neonatal estrogenization reverted the Lin28/let-7 expression ratio; expression changes were also detected in other models of delayed puberty, due to early photoperiod or nutritional manipulations. In addition, hypophysectomy or growth hormone (GH) deficiency revealed regulation of this system by gonadotropins and GH. Our data document the expression profiles of the Lin28/let-7 system in rat testis along postnatal/pubertal maturation, and their perturbation in models of pubertal and hormonal manipulation.

Next Generation Sequencing Analysis Reveals Segmental Patterns of microRNA Expression in Mouse Epididymal Epithelial Cells

The functional maturation of mammalian spermatozoa is accomplished as the cells descend through the highly specialized microenvironment of the epididymis. This dynamic environment is, in turn, created by the combined secretory and absorptive activity of the surrounding epithelium and displays an extraordinary level of regionalization. Although the regulatory network responsible for spatial coordination of epididymal function remains unclear, recent evidence has highlighted a novel role for the RNA interference pathway. Indeed, as noncanonical regulators of gene expression, small noncoding RNAs have emerged as key elements of the circuitry involved in regulating epididymal function and hence sperm maturation. Herein we have employed next generation sequencing technology to profile the genome-wide miRNA signatures of mouse epididymal cells and characterize segmental patterns of expression. An impressive profile of some 370 miRNAs were detected in the mouse epididymis, with a subset of these specifically identified within the epithelial cells that line the tubule (218). A majority of the latter miRNAs (75%) were detected at equivalent levels along the entire length of the mouse epididymis. We did however identify a small cohort of miRNAs that displayed highly regionalized patterns of expression, including miR-204-5p and miR-196b-5p, which were down- and up-regulated by approximately 39- and 45-fold between the caput/caudal regions, respectively. In addition we identified 79 miRNAs (representing ~ 21% of all miRNAs) as displaying conserved expression within all regions of the mouse, rat and human epididymal tissue. These included 8/14 members of let-7 family of miRNAs that have been widely implicated in the control of androgen signaling and the repression of cell proliferation and oncogenic pathways. Overall these data provide novel insights into the sophistication of the miRNA network that regulates the function of the male reproductive tract.

Gene interference strategies as a new tool for the treatment of prostate cancer

Prostate cancer (PCa) is one of the most common cancer in men. It affects older men and the incidence increases with age; the median age at diagnosis is 67 years. The diagnosis of PCa is essentially based on three tools: digital rectal exam, serum concentration of prostate specific antigen, and transrectal ultrasound-guided biopsy. Currently, the therapeutic treatments of this cancer are different and range from the prostatectomy to hormonal therapy, to radiation therapy, to immunotherapy, and to chemotherapy. However, additional efforts are required in order to find new weapons for the treatment of metastatic setting of disease. The purpose of this review is to highlight new therapeutic strategies based on gene interference; in fact, numerous siRNA and miRNA in the therapeutic treatment of PCa are reported below.

The role of Myc and let-7a in glioblastoma, glucose metabolism and response to therapy

Glioblastoma multiforme (GBM) is thought to result from an imbalance between glucose metabolism and tumor growth. The Myc oncogene and lethal-7a microRNA (let-7a miRNA) have been suggested to cooperatively regulate multiple downstream targets leading to changes in chromosome stability, gene mutations, and/or modulation of tumor growth. Here, we review the roles of Myc and let-7a in glucose metabolism and tumor growth and addresses their future potential as prognostic markers and therapeutic tools in GBM. We focus on the functions of Myc and let-7a in glucose uptake, tumor survival, proliferation, and mobility of glioma cells. In addition, we discuss how regulation of different pathways by Myc or let-7a may be useful for future GBM therapies. A large body of evidence suggests that targeting Myc and let-7a may provide a selective mechanism for the deregulation of glucose metabolic pathways in glioma cells. Indeed, Myc and let-7a are aberrantly expressed in GBM and have been linked to the regulation of cell growth and glucose metabolism in GBM. This article is part of a Special Issue entitled "Targeting alternative glucose metabolism and regulate pathways in GBM cells for future glioblastoma therapies".

Capsaicin causes inactivation and degradation of the androgen receptor by inducing the restoration of miR-449a in prostate cancer

Capsaicin, a novel antitumor agent extracted from chili peppers, has been proven to induce growth inhibition in various types of cancer including prostate cancer. However, the detailed mechanisms remain largely undiscovered. In the present study, we explored the regulation of the androgen receptor (AR) by capsaicin and further researched the mechanisms of their interaction in AR-positive prostate cancer cells. In the present study, cell viability was assessed by MTT assay. Cell cycle distribution was determined using flow cytometry. Expression levels of cyclin D1, miR-449a, AR and prostate-specific antigen (PSA) were assessed by quantitative real-time polymerase chain reaction or western blot analysis. To further confirm the relationship among miR-449a, AR and prostate cancer proliferation, miR-449a was overexpressed by a lentivirus in prostate cancer cells. We discovered that capsaicin prevented tumor proliferation and cell cycle progression through inactivation and degradation of AR. We also found that restoration of miR-449a induced by capsaicin treatment resulted in the inhibition of AR signaling. Finally, we demonstrated that increased expression of miR-449a sensitized prostate cancer to capsaicin treatment. Finally, our experimental results indicated that capsaicin negatively modulates the activity of AR at the mRNA and protein levels by restoring miR-449a profiling in prostate cancer. In addition, increased expression of miR-449a may facilitate the sensitivity of prostate cancer to capsaicin treatment. Thus, capsaicin may be developed as a novel anti-AR drug for the therapy of prostate cancer.

NF-κB2/p52:c-Myc:hnRNPA1 Pathway Regulates Expression of Androgen Receptor Splice Variants and Enzalutamide Sensitivity in Prostate Cancer

Castration-resistant prostate cancer (CRPC) remains dependent on androgen receptor (AR) signaling. Alternative splicing of the AR to generate constitutively active, ligand-independent variants is one of the principal mechanisms that promote the development of resistance to next-generation antiandrogens such as enzalutamide. Here, we demonstrate that the splicing factor heterogeneous nuclear RNA-binding protein A1 (hnRNPA1) plays a pivotal role in the generation of AR splice variants such as AR-V7. hnRNPA1 is overexpressed in prostate tumors compared with benign prostates, and its expression is regulated by NF-κB2/p52 and c-Myc. CRPC cells resistant to enzalutamide exhibit higher levels of NF-κB2/p52, c-Myc, hnRNPA1, and AR-V7. Levels of hnRNPA1 and AR-V7 are positively correlated with each other in prostate cancer. The regulatory circuit involving NF-κB2/p52, c-Myc, and hnRNPA1 plays a central role in the generation of AR splice variants. Downregulation of hnRNPA1 and consequently of AR-V7 resensitizes enzalutamide-resistant cells to enzalutamide, indicating that enhanced expression of hnRNPA1 may confer resistance to AR-targeted therapies by promoting the generation of splice variants. These findings may provide a rationale for cotargeting these pathways to achieve better efficacy through AR blockade.

miR-145 suppress the androgen receptor in prostate cancer cells and correlates to prostate cancer prognosis

Androgen signalling through the androgen receptor (AR) is essential for prostate cancer initiation, progression and transformation to the lethal castration-resistant state. The aim of this study was to characterize the mechanisms by which miR-145 deregulation contribute to prostate cancer progression. The miR-145 levels, measured by quantitative reverse transcription-polymerase chain reaction, were found to inversely correlate with occurrence of metastases, survival and androgen deprivation therapy response in a well-characterized prostate cancer cohort. Introduction of ectopic miR-145 in prostate cancer cells generated an inhibitory effect on the AR at both transcript and protein levels as well as its activity and downstream targets prostate-specific antigen (PSA), kallikrein-related peptidase 2 and TMPRSS2. The regulation was shown to be mediated by direct binding using Ago2-specific immunoprecipitation, but there was also indication of synergetic AR activation. These findings were verified in clinical prostate specimens by demonstrating inverse correlations between miR-145 and AR expression as well as serum PSA levels. In addition, miR-145 was found to regulate androgen-dependent cell growth in vitro. Our findings put forward novel possibilities of therapeutic intervention, as miR-145 potentially could decrease both the stem cells and the AR expressing bulk of the tumour and hence reduce the transformation to the deadly castration-resistant form of prostate cancer.

Grouping Pentylenetetrazol-Induced Epileptic Rats According to Memory Impairment and MicroRNA Expression Profiles in the Hippocampus

Previous studies have demonstrated a close relationship between abnormal regulation of microRNA (miRNA) and various types of diseases, including epilepsy and other neurological disorders of memory. However, the role of miRNA in the memory impairment observed in epilepsy remains unknown. In this study, a model of temporal lobe epilepsy (TLE) was induced via pentylenetetrazol (PTZ) kindling in Sprague-Dawley rats. First, the TLE rats were subjected to Morris water maze to identify those with memory impairment (TLE-MI) compared with TLE control rats (TLE-C), which presented normal memory. Both groups were analyzed to detect dysregulated miRNAs in the hippocampus; four up-regulated miRNAs (miR-34c, miR-374, miR-181a, and miR-let-7c-1) and seven down-regulated miRNAs (miR-1188, miR-770-5p, miR-127-5p, miR-375, miR-331, miR-873-5p, and miR-328a) were found. Some of the dysregulated miRNAs (miR-34c, miR-1188a, miR-328a, and miR-331) were confirmed using qRT-PCR, and their blood expression patterns were identical to those of their counterparts in the rat hippocampus. The targets of these dysregulated miRNAs and other potentially enriched biological signaling pathways were analyzed using bioinformatics. Following these results, the MAPK, apoptosis and hippocampal signaling pathways might be involved in the molecular mechanisms underlying the memory disorders of TLE.

Androgen receptor signaling in prostate cancer

The androgen receptor (AR), ligand-induced transcription factor, is expressed in primary prostate cancer and in metastases. AR regulates multiple cellular events, proliferation, apoptosis, migration, invasion, and differentiation. Its expression in prostate cancer cells is regulated by steroid and peptide hormones. AR downregulation by various compounds which are contained in fruits and vegetables is considered a chemopreventive strategy for prostate cancer. There is a bidirectional interaction between the AR and micro-RNA (miRNA) in prostate cancer; androgens may upregulate or downregulate the selected miRNA, whereas the AR itself is a target of miRNA. AR mutations have been discovered in prostate cancer, and their incidence may increase with tumor progression. AR mutations and increased expression of selected coactivators contribute to the acquisition of agonistic properties of anti-androgens. Expression of some of the coactivators is enhanced during androgen ablation. AR activity is regulated by peptides such as cytokines or growth factors which reduce the concentration of androgen required for maximal stimulation of the receptor. In prostate cancer, variant ARs which exhibit constitutive activity were detected. Novel therapies which interfere with intracrine synthesis of androgens or inhibit nuclear translocation of the AR have been introduced in the clinic.

Microdissecting the role of microRNAs in the pathogenesis of prostate cancer

MicroRNAs (miRNAs) are naturally occurring, small, non-coding RNA molecules that post-transcriptionally regulate the expression of a large number of genes involved in various biological processes, either through mRNA degradation or through translation inhibition. Since the discovery of miRNAs, a vast amount of research has implicated the deregulated expression of miRNAs in different malignancies, including prostate cancer (PCa). Different miRNA expression profiles are reportedly associated with the development, progression, and emergence of castration-resistant PCa (CRPC), suggesting their use in the diagnosis, prognosis, and development of anti-cancer treatment models directed against this disease. However, before their exploitation in terms of therapeutics, a thorough understanding and in-depth mechanistic studies of these miRNAs and the gene networks they orchestrate are necessary for ascertaining their definitive role in the development and progression of PCa. This review attempts to extensively summarize the current knowledge of aberrantly expressed miRNAs and their mode of action in PCa, while highlighting the existing discrepancies and future research warranted.

The role of microRNA in castration-resistant prostate cancer

INTRODUCTION

Castration-resistant prostate cancer (CRPC) has a historically low median survival rate, but recent advances and discoveries in microRNAs (miRNAs) have opened the potential for new prognostication modalities to enhance therapeutic success. As new chemotherapies and immunotherapies are developed, there is an increasing need for precision and stratification of CRPC to allow for optimization and personalization of therapy.

METHODS

A systematic literature review was conducted via electronic database resulting in the selection of 42 articles based on title, abstract, study format, and content by a consensus of all participating authors. Most selected articles were published between 2002 and 2013. In this review, we discuss the robustness of miRNAs as a biomarker platform, miRNAs associated with prostate cancer, and recent discoveries of miRNA associations with CRPC.

RESULTS

The associations discovered have been of interest owing to the ability to differentiate between CRPC and localized prostate cancer. With the evaluation of multiple miRNAs, it is possible to provide a profile regarding tumor characteristics. Furthermore, actions of miRNAs on CRPC tumor cells have the ability to suppress metastatic phenotypes.

CONCLUSION

miRNAs may have a growing role in CRPC prognostication and may potentially transform into a therapeutic potential.