Loss of mir-146a function in hormone-refractory prostate cancer

MicroRNA-146a modulates TGF-β1-induced phenotypic differentiation in human dermal fibroblasts by targeting SMAD4

During wound healing and tissue repair the dermal fibroblast-to-myofibroblast transdifferentiation plays an important role, transforming growth factor-β1 (TGF-β1) is considered to be the main stimuli factor of transdifferentiation. MicroRNAs (miRNAs) have recently emerged as key post-transcriptional regulators of gene expression. The involvement of miRNAs and their roles in TGF-β1-induced myofibroblast transdifferentiation remains to be determined in detail. The current study found that the expression of miR-146a was upregulated in human dermal fibroblasts cells in response to TGF-β1 stimulation in dose-dependent manner by quantitative RT-PCR. Bioinformatic analyses predict that signaling effectors mothers against decapentaplegic protein 4 (SMAD4) is a miR-146a target gene. Luciferase assay demonstrated that miR-146a mimics suppressed SMAD4 3'-UTR reporter construct activity. Furthermore, miR-146a overexpression in dermal fibroblast did not decrease target mRNA levels, but significantly reduced target protein expression. In addition, dermal fibroblasts transfected with miR-146a mimics exhibited attenuated TGF-β1 -induced α-smooth muscle actin (α-SMA) expression compared with the control. This study demonstrated that miR-146a may function as a novel negative regulator to modulate myofibroblast transdifferentiation during TGF-β1 induction by targeting SMAD4.

MicroRNA-mediated breast cancer metastasis: from primary site to distant organs

The recent upsurge of interest in microRNA (miRNA) is partly attributed to the discovery of the novel roles of miRNAs in many physiological and pathological processes, including tumor development. Research on breast cancer metastasis has also focused on the concept of miRNA, which can act either as promoters or as suppressors of metastases. This review will focus on a series of recent studies that demonstrate the involvement of miRNAs in breast cancer metastasis and will briefly describe various pathways of miRNA-regulated metastasis. Finally, future prospects will be discussed for the potential role of miRNAs as predictive markers and therapeutic agents for patients with breast cancer metastases.

miR-146a suppresses the sensitivity to interferon-α in hepatocellular carcinoma cells

BACKGROUND

Interferon-based (IFN-based) therapy is effective in the treatment of advanced hepatocellular carcinoma (HCC). However, the issue of resistance to this therapy remains to be solved. The aim of this study was to identify microRNAs (miRNAs) that govern the sensitivity to IFN-α in HCC cells.

METHODS

miRNA microarray analysis using IFN-α-resistant clones of PLC/PRF/5 (PLC-Rs) and their parental cells (PLC-P) was conducted. Changes in the anti-cancer effects of IFN-α were studied after gain-of-function and loss-of-function of the candidate miRNA.

RESULTS

miR-146a expression was significantly higher in PLC-Rs than in PLC-P. miR-146a decreased the sensitivity to IFN-α through the suppression of apoptosis. Further experiments showed that miR-146a-related resistance to IFN-α was mediated through SMAD4.

CONCLUSIONS

The results indicated that miR-146a regulated the sensitivity of HCC cells to the cytotoxic effects of IFN-α through SMAD4, suggesting that this miRNA could be suitable for prediction of the clinical response and potential therapeutic target in HCC patients on IFN-based therapy.

Has-miR-146a polymorphism (rs2910164) and cancer risk: a meta-analysis of 19 case-control studies

Epidemiological studies have evaluated the association between has-miR-146a polymorphism (rs2910164) and cancer risk. However, published data are still inconclusive. Here, we performed a meta-analysis to assess the relationship between has-miR-146a polymorphism (rs2910164) and cancer susceptibility until May 8, 2010. Nineteen published case-control studies including a total of 10,496 cases and 12,885 controls were acquired. Overall, Increased cancer risk was found in domain model (OR = 1.18, 95% CI: 1.03-1.35) rather than in other genetic models when all studies were pooled into the meta-analysis. Stratified analysis shown that significant association between rs2910164 polymorphism and cancer susceptibility was present in Asians (OR = 1.14, 95% CI: 1.01-1.29 for CG vs. CC; OR = 1.19, 95% CI: 1.03-1.39 for GG + CG vs. CC), but not in Caucasian populations. In the subgroup analysis by cancer types, no significantly increased risk of breast, gastric, prostate or bladder cancer were found in any of the genetic models. In summary, this meta-analysis suggests that has-miR-146a polymorphism (rs2910164) is associated with increased cancer susceptibility in Asians. However, further well-designed studies with large sample size will be necessary to validate the risk identified in the current meta-analysis.

Regulation of microRNA expression and function by nuclear receptor signaling

MicroRNAs (miRNAs) are small non-coding RNA transcripts that affect various cellular pathways by serving as regulators of gene expression at the translational and transcriptional level. Nuclear receptors (NRs) are ligand-activated transcription factors that regulate gene transcription by binding to the promoter region or by interacting with other transcription factors. NRs can regulate miRNA expression either at the transcriptional level, or through posttranscriptional maturation by interacting with miRNA processing factors. This review will summarize recent advances in knowledge of the modulation of miRNA expression by NRs. Increased understanding of the molecular basis of miRNA expression may enable new therapeutic interventions that modulate miRNA activities through NR-mediated signaling.

MicroRNA expression profiles in the progression of prostate cancer--from high-grade prostate intraepithelial neoplasia to metastasis

INTRODUCTION

Models of the multistep process related to cancer progression have been designed for many cancers including prostate. The aim of this study is to propose a new model including a possible role for recently described micro RNAs in prostate cancer (CaP) progression.

METHODS

Sixty-three patients underwent radical prostatectomy to treat localized prostate carcinoma. The specimens of 15 patients were representative of high grade prostate intraepithelial neoplasia (HGPIN). Fourteen specimens represented localized favorable CaP, and 34 unfavorable, mostly non-organ-confined disease. Representing the advanced disease we studied 4 metastatic androgen-independent CaP and 2 cell lines. Micro RNAs were isolated using the mirVana miRNA Isolation kit and cDNA was obtained using the TaqMan miRNA Reverse Transcription kit to the miRNAs: hsa-miR-let7c, hsa-miR-15a, hsa-miR-16, hsa-miR-21, hsa-miR-25, hsa-miR-32, hsa-miR-100, hsa-miR-143, hsa-miR-145, hsa-miR-146a, hsa-miR-191, hsa-miR-199a, hsa-miR-206, and hsa-miR-218. Quantitative RT-PCR was carried out using the ABI 7500 Fast Real-Time PCR System and the TaqMan Universal PCR Master Mix. miRNA expression levels were measured by relative quantification, and fold expression changes were determined by the 2(-ΔΔCT) method. The small nucleolar RNA RNU43 was used as an endogenous control.

RESULTS

Except for miR-21 and miR-206, the expression levels of all miRNAs significantly changed during the progression of CaP. Interestingly, there was a significant global loss of miRNA expression between HGPIN and metastasis at 2 important steps. The first was related to the transition from HGPIN to invasive adenocarcinoma, and the second was related to the transition from localized to metastatic adenocarcinomas.

CONCLUSION

Through the analysis of 14 miRNAs in 4 groups of prostate lesions, which reproduced the progression of CaP, we showed that there is a global loss of miRNA expression at 2 distinct steps. The first related to the transition between HGPIN and localized invasive carcinoma, and the second associated with the transition from localized to metastatic CaP. The importance of our study is in the identification of possible miRNAs and miRNA-targeted genes involved in the progression of prostate carcinogenesis that may help the development of potential diagnostic or prognostic markers as well as the design of new target therapies.

miR 488* inhibits androgen receptor expression in prostate carcinoma cells

Androgen receptor (AR) is a ligand-dependent transcription factor, which plays a significant role in prostate carcinogenesis. Blockade of AR and its ligand, androgen is the basis for the treatment of prostate cancer (PCa). Nevertheless, a modest increase in the critical levels of AR mRNA and corresponding protein is sufficient for the development of resistance to antiandrogen therapy. A strategy to further downregulate AR mRNA and protein expression in combination with antiandrogen therapy may prevent or delay the development of androgen-independent PCa. Recent studies show that microRNAs (miRNAs) perform tumor suppressor functions in various cancers. In this study, we demonstrate that the overexpression of miR 488* downregulates the transcriptional activity of AR and inhibits the endogenous AR protein production in both androgen-dependent and androgen-independent PCa cells. In addition, miR 488* blocks the proliferation and enhances the apoptosis of PCa cells. Our data indicate that miR 488* targets AR and is a potential modulator of AR mediated signaling. Our findings provide insight for utilizing miRNAs as novel therapeutics to target AR in PCa.

Resveratrol, MicroRNAs, Inflammation, and Cancer

MicroRNAs are short noncoding RNAs that regulate the expression of many target genes posttranscriptionally and are thus implicated in a wide array of cellular and developmental processes. The expression of miR-155 or miR-21 is upregulated during the course of the inflammatory response, but these microRNAs are also considered oncogenes due to their upregulation of expression in several types of tumors. Furthermore, it is now well established that inflammation is associated with the induction or the aggravation of nearly 25% of cancers. Therefore, the above microRNAs are thought to link inflammation and cancer. Recently, resveratrol (trans-3,4′,5-trihydroxystilbene), a natural polyphenol with antioxidant, anti-inflammatory, and anticancer properties, currently at the stage of preclinical studies for human cancer prevention, has been shown to induce the expression of miR-663, a tumor-suppressor and anti-inflammatory microRNA, while downregulating miR-155 and miR-21. In this paper we will discuss how the use of resveratrol in therapeutics may benefit from the preanalyses on the status of expression of miR-155 or miR-21 as well as of TGFβ1. In addition, we will discuss how resveratrol activity might possibly be enhanced by simultaneously manipulating the levels of its key target microRNAs, such as miR-663.

Inhibitory effects of miR-146b-5p on cell migration and invasion of pancreatic cancer by targeting MMP16

Previous studies have shown that miRNAs participate in a wide range of biological functions and play important roles in various human diseases including cancer. We found miR-146b-5p significantly dysregulated in human pancreatic cancer cells by qRT-PCR. To demonstrate its function and regulation mechanism, we overexpressed miR-146-5p by transfecting the mimics. Our data showed that miR-146b-5p overexpression significantly reduced the abilities of migration and invasion of MIA PaCa-2 pancreatic cancer cells. Furthermore, we found that matrix metalloproteinase 16 (MMP16) was a downstream target of miR-146b-5p by dual-luciferase reporter assay. Altogether, our findings suggest that miR-146b-5p may be involved in pancreatic cancer cell migration and invasion by targeting MMP16, and miR-146b-5p may be a potential therapeutic target for the pancreatic cancer.

Carboxyl-terminal truncated HBx regulates a distinct microRNA transcription program in hepatocellular carcinoma development

BACKGROUND

The biological pathways and functional properties by which misexpressed microRNAs (miRNAs) contribute to liver carcinogenesis have been intensively investigated. However, little is known about the upstream mechanisms that deregulate miRNA expressions in this process. In hepatocellular carcinoma (HCC), hepatitis B virus (HBV) X protein (HBx), a transcriptional trans-activator, is frequently expressed in truncated form without carboxyl-terminus but its role in miRNA expression and HCC development is unclear.

METHODS

Human non-tumorigenic hepatocytes were infected with lentivirus-expressing full-length and carboxyl-terminal truncated HBx (Ct-HBx) for cell growth assay and miRNA profiling. Chromatin immunoprecipitation microarray was performed to identify the miRNA promoters directly associated with HBx. Direct transcriptional control was verified by luciferase reporter assay. The differential miRNA expressions were further validated in a cohort of HBV-associated HCC tissues using real-time PCR.

RESULTS

Hepatocytes expressing Ct-HBx grew significantly faster than the full-length HBx counterparts. Ct-HBx decreased while full-length HBx increased the expression of a set of miRNAs with growth-suppressive functions. Interestingly, Ct-HBx bound to and inhibited the transcriptional activity of some of these miRNA promoters. Notably, some of the examined repressed-miRNAs (miR-26a, -29c, -146a and -190) were also significantly down-regulated in a subset of HCC tissues with carboxyl-terminal HBx truncation compared to their matching non-tumor tissues, highlighting the clinical relevance of our data.

CONCLUSION

Our results suggest that Ct-HBx directly regulates miRNA transcription and in turn promotes hepatocellular proliferation, thus revealing a viral contribution of miRNA deregulation during hepatocarcinogenesis.

ROCK1 as a potential therapeutic target in osteosarcoma

Osteosarcoma is the most common primary malignancy of bone. Patients with localized disease are routinely treated with surgery and chemotherapy. Unfortunately, many of these patients eventually relapse even after high-dose pre- and postoperative chemotherapy. Upon recurrence of the tumor locally or distantly, they have limited treatment options that are usually unsuccessful. Our prior studies screening lentiviral shRNA libraries, searching for kinases involved in osteosarcoma cell growth and proliferation have identified the Rho-associated coiled-coil containing protein kinase 1 (ROCK1) as a possible hit. We show in this study that ROCK1 is highly expressed in various tumor cell lines and tumor tissues from osteosarcoma patients. ROCK1 knockdown by synthetic siRNA decreases cell proliferation, viability and induces apoptosis in osteosarcoma cell lines KHOS and U-2OS. Finally, we established the relationship between expression levels of ROCK1 and clinical prognosis in osteosarcoma patients by using immunohistochemistry. There were significant differences in overall survival between cohorts of patients with ROCK1 levels categorized as high-staining, moderate-staining, and low-staining. High levels of ROCK1 were associated with poor outcomes in clinical osteosarcoma. These findings suggest that knockdown of ROCK1 inhibits proliferation and induces apoptosis in osteosarcoma cell lines. ROCK1 may be a promising therapeutic target for the treatment of osteosarcoma patients.

No association of pre-microRNA-146a rs2910164 polymorphism and risk of hepatocellular carcinoma development in Turkish population: a case-control study

AIM

MicroRNAs (miRNAs) are an abundant class of small non-protein coding RNAs with posttranscriptional regulatory functions as tumor suppressors and oncogenes. Aberrant expression and structural alteration of miRNAs are considered to participate in tumorigenesis and cancer development. It has been suggested that the presence of single nucleotide polymorphisms in precursor miRNAs (pre-miRNAs) can alter miRNA processing, expression, and/or binding to target mRNA and represent another type of genetic variability that can contribute to the susceptibility of human cancers. A G/C polymorphism (rs2910164), which is located in the sequence of miR-146a precursor, results in a change from G:U to C:U in its stem region.

METHODS

To determine the association of the miR-146a rs2910164 polymorphism on the risk of hepatocellular carcinoma (HCC) development in Turkish population, a hospital-based case-control study was designed consisting of 222 subjects with HCC and 222 cancer-free control subjects matched on age, gender, smoking and alcohol status. The genotype frequency of miR-146a rs2910164 polymorphism was determined by using a polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) assay.

RESULTS

No statistically significant differences were found in the allele or genotype distributions of the miR-146a rs2910164 polymorphism among HCC and cancer-free control subjects (p>0.05).

CONCLUSION

Our results demonstrate that the miR-146a rs2910164 polymorphism has no major role in genetic susceptibility to hepatocellular carcinogenesis, at least in the population studied here. Independent studies are needed to validate our findings in a larger series, as well as in patients of different ethnic origins.

A functional polymorphism in the pre-miR-146a gene is associated with risk and prognosis in adult glioma

MicroRNAs (miRNAs) are non-coding RNAs that function as post-transcriptional regulators of tumor suppressors and oncogenes. Single nucleotide polymorphisms (SNPs) in miRNAs may contribute to carcinogenesis by altering expression of miRNAs and their targets. A G>C polymorphism (rs2910164) in the miR-146a precursor sequence leads to a functional change associated with the risk for numerous malignancies. A role for this SNP in glioma pathogenesis has not yet been examined. We investigated whether rs2910164 genotypes influence glioma risk and prognosis in a multi-center case-control study comprised of 593 Caucasian glioma cases and 614 community-based controls. Unconditional logistic regression was used to estimate odds ratios (OR) and 95% confidence intervals (CI) for rs2910164 genotypes according to case status. Cox proportional hazards regression modeling was used to estimate hazards ratios (HR) and 95% CIs according to genotype among glioblastomas, the most lethal glioma subtype. An increased glioma risk was observed among rs2910164 minor allele (C) carriers (per allele OR (95% CI) = 1.22 (1.01-1.46, p (trend) = 0.039)). The association was stronger among older subjects carrying at least one copy of the C allele (OR (95% CI) = 1.38 (1.04-1.83, P = 0.026). Mortality was increased among minor allele carriers (HR (95% CI) = 1.33 (1.03-1.72, P = 0.029)), with the association largely restricted to females (HR (95% CI) = 2.02 (1.28-3.17, P = 0.002)). We provide novel data suggesting rs2910164 genotype may contribute to glioma susceptibility and outcome. Future studies are warranted to replicate these findings and characterize mechanisms underlying these associations.

Genome-wide profiling of chromatin signatures reveals epigenetic regulation of MicroRNA genes in colorectal cancer

Altered expression of microRNAs (miRNA) occurs commonly in human cancer, but the mechanisms are generally poorly understood. In this study, we examined the contribution of epigenetic mechanisms to miRNA dysregulation in colorectal cancer by carrying out high-resolution ChIP-seq. Specifically, we conducted genome-wide profiling of trimethylated histone H3 lysine 4 (H3K4me3), trimethylated histone H3 lysine 27 (H3K27me3), and dimethylated histone H3 lysine 79 (H3K79me2) in colorectal cancer cell lines. Combining miRNA expression profiles with chromatin signatures enabled us to predict the active promoters of 233 miRNAs encoded in 174 putative primary transcription units. By then comparing miRNA expression and histone modification before and after DNA demethylation, we identified 47 miRNAs encoded in 37 primary transcription units as potential targets of epigenetic silencing. The promoters of 22 transcription units were associated with CpG islands (CGI), all of which were hypermethylated in colorectal cancer cells. DNA demethylation led to increased H3K4me3 marking at silenced miRNA genes, whereas no restoration of H3K79me2 was detected in CGI-methylated miRNA genes. DNA demethylation also led to upregulation of H3K4me3 and H3K27me3 in a number of CGI-methylated miRNA genes. Among the miRNAs we found to be dysregulated, many of which are implicated in human cancer, miR-1-1 was methylated frequently in early and advanced colorectal cancer in which it may act as a tumor suppressor. Our findings offer insight into the association between chromatin signatures and miRNA dysregulation in cancer, and they also suggest that miRNA reexpression may contribute to the effects of epigenetic therapy.

MicroRNA-146a inhibits glioma development by targeting Notch1

Dysregulated epidermal growth factor receptor (EGFR) signaling through either genomic amplification or dominant-active mutation (EGFR(vIII)), in combination with the dual inactivation of INK4A/ARF and PTEN, is a leading cause of gliomagenesis. Our global expression analysis for microRNAs revealed that EGFR activation induces miR-146a expression, which is further potentiated by inactivation of PTEN. Unexpectedly, overexpression of miR-146a attenuates the proliferation, migration, and tumorigenic potential of Ink4a/Arf(-/-) Pten(-/-) Egfr(vIII) murine astrocytes. Its ectopic expression also inhibits the glioma development of a human glioblastoma cell line in an orthotopic xenograft model. Such an inhibitory function of miR-146a on gliomas is largely through downregulation of Notch1, which plays a key role in neural stem cell maintenance and is a direct target of miR-146a. Accordingly, miR-146a modulates neural stem cell proliferation and differentiation and reduces the formation and migration of glioma stem-like cells. Conversely, knockdown of miR-146a by microRNA sponge upregulates Notch1 and promotes tumorigenesis of malignant astrocytes. These findings indicate that, in response to oncogenic cues, miR-146a is induced as a negative-feedback mechanism to restrict tumor growth by repressing Notch1. Our results provide novel insights into the signaling pathways that link neural stem cells to gliomagenesis and may lead to new strategies for treating brain tumors.

MicroRNAs in Development and Disease

MicroRNAs (miRNAs) are a class of posttranscriptional regulators that have recently introduced an additional level of intricacy to our understanding of gene regulation. There are currently over 10,000 miRNAs that have been identified in a range of species including metazoa, mycetozoa, viridiplantae, and viruses, of which 940, to date, are found in humans. It is estimated that more than 60% of human protein-coding genes harbor miRNA target sites in their 3′ untranslated region and, thus, are potentially regulated by these molecules in health and disease. This review will first briefly describe the discovery, structure, and mode of function of miRNAs in mammalian cells, before elaborating on their roles and significance during development and pathogenesis in the various mammalian organs, while attempting to reconcile their functions with our existing knowledge of their targets. Finally, we will summarize some of the advances made in utilizing miRNAs in therapeutics.

Human papillomavirus 16 E5 modulates the expression of host microRNAs

Human papillomavirus (HPV) infection is a prerequisite of developing cervical cancer, approximately half of which are associated with HPV type 16. HPV 16 encodes three oncogenes, E5, E6, and E7, of which E5 is the least studied so far. Its roles in regulating replication and pathogenesis of HPV are not fully understood. Here we utilize high-throughput screening to coordinately investigate the effect of E5 on the expression of host protein-coding and microRNA genes. MicroRNAs form a class of 22nt long noncoding RNAs with regulatory activity. Among the altered cellular microRNAs we focus on the alteration in the expression of miR-146a, miR-203 and miR-324-5p and their target genes in a time interval of 96 hours of E5 induction. Our results indicate that HPV infection and subsequent transformation take place through complex regulatory patterns of gene expression in the host cells, part of which are regulated by the E5 protein.

MicroRNAs as regulators of signal transduction in urological tumors

BACKGROUND

MicroRNAs (miRNAs) are short noncoding RNAs that have been shown to play pivotal roles in carcinogenesis. In the past decade, miRNAs have been the focus of much research in oncology, and there are great expectations for their utility as cancer biomarkers and therapeutic targets.

CONTENT

In this review we examine how miRNAs can regulate signal transduction pathways in urological tumors. We performed in silico target prediction using TargetScan 5.1 to identify the signal transduction targets of miRNA, and we summarize the experimental evidence detailing miRNA regulation of pathways analyzed herein.

SUMMARY

miRNAs, which have been shown to be dysregulated in bladder, prostate, and renal cell cancer, are predicted to target key proteins in signal transduction. Because androgen receptor signaling is a major regulator of prostate cancer growth, its regulation by miRNAs has been well described. In addition, members of the phosphatidylinositol 3-kinase/Akt (RAC-alpha serine/threonine-protein kinase) signaling pathway have been shown to be susceptible to miRNA regulation. In contrast, there are very few studies on the impact of miRNA regulation on signaling by VHL (von Hippel-Lindau tumor suppressor) and vascular endothelial growth factor in renal cell carcinoma or by fibroblast growth factor receptor 3 and p53 in bladder cancer. Many miRNAs are predicted to target important signaling pathways in urological tumors and are dysregulated in their respective cancer types; a systematic overview of miRNA regulation of signal transduction in urological tumors is pending. The identification of these regulatory networks might lead to novel targeted cancer therapies. In general, the targeting of miRNAs is a valuable approach to cancer therapy, as has been shown recently for various types of cancer.

Clinical significance of miR-146a in gastric cancer cases

PURPOSE

The profiles of microRNAs change significantly in gastric cancer. MiR-146a is reported to be a tumor suppressor in pancreatic cancer, breast cancer, and prostate cancer. We investigated the clinical significance of miR-146a in gastric cancer, in particular focusing on hypothetical miR-146a target genes, such as epidermal growth factor receptor (EGFR) and interleukin-1 receptor-associated kinase (IRAK1).

EXPERIMENTAL DESIGN

We examined miR-146a levels in 90 gastric cancer samples by q-real-time (qRT)-PCR and analyzed the association between miR-146a levels and clinicopathologic factors and prognosis. The regulation of EGFR and IRAK1 by miR-146a was examined with miR-146a-transfected gastric cancer cells. Moreover, we analyzed the association between miR-146a levels and the G/C single nucleotide polymorphism (SNP) within pre-miR-146a seed sequences in 76 gastric cancer samples, using direct sequencing of genomic DNA.

RESULTS

In 90 clinical samples of gastric cancer, miR-146a levels in cancer tissues were significantly lower than those in the corresponding noncancerous tissue (P < 0.001). Lower levels of miR-146a were associated with lymph node metastasis and venous invasion (P < 0.05). Moreover, a lower level of miR-146a was an independent prognostic factor for overall survival (P = 0.003). Ectopic expression of miR-146a inhibited migration and invasion and downregulated EGFR and IRAK1 expression in gastric cancer cells. In addition, G/C SNP within the pre-miR-146a seed sequence significantly reduced miR-146a levels in the GG genotype compared with the CC genotype.

CONCLUSIONS

MiR-146a contains an SNP, which is associated with mature miR-146a expression. MiR-146a targeting of EGFR and IRAK1 is an independent prognostic factor in gastric cancer cases.

Identification of miRs-143 and -145 that is associated with bone metastasis of prostate cancer and involved in the regulation of EMT

The principal problem arising from prostate cancer (PCa) is its propensity to metastasize to bone. MicroRNAs (miRNAs) play a crucial role in many tumor metastases. The importance of miRNAs in bone metastasis of PCa has not been elucidated to date. We investigated whether the expression of certain miRNAs was associated with bone metastasis of PCa. We examined the miRNA expression profiles of 6 primary and 7 bone metastatic PCa samples by miRNA microarray analysis. The expression of 5 miRNAs significantly decreased in bone metastasis compared with primary PCa, including miRs-508-5p, -145, -143, -33a and -100. We further examined other samples of 16 primary PCa and 13 bone metastases using real-time PCR analysis. The expressions of miRs-143 and -145 were verified to down-regulate significantly in metastasis samples. By investigating relationship of the levels of miRs-143 and -145 with clinicopathological features of PCa patients, we found down-regulations of miRs-143 and -145 were negatively correlated to bone metastasis, the Gleason score and level of free PSA in primary PCa. Over-expression miR-143 and -145 by retrovirus transfection reduced the ability of migration and invasion in vitro, and tumor development and bone invasion in vivo of PC-3 cells, a human PCa cell line originated from a bone metastatic PCa specimen. Their upregulation also increased E-cadherin expression and reduced fibronectin expression of PC-3 cells which revealed a less invasive morphologic phenotype. These findings indicate that miRs-143 and -145 are associated with bone metastasis of PCa and suggest that they may play important roles in the bone metastasis and be involved in the regulation of EMT Both of them may also be clinically used as novel biomarkers in discriminating different stages of human PCa and predicting bone metastasis.

Effects of 1α,25 dihydroxyvitamin D3 and testosterone on miRNA and mRNA expression in LNCaP cells

Background

There is evidence from epidemiological and in vitro studies that the biological effects of testosterone (T) on cell cycle and survival are modulated by 1,25-dihydroxyvitamin D₃ (1,25(OH)₂D₃) in prostate cancer. To investigate the cross talk between androgen- and vitamin D-mediated intracellular signaling pathways, the individual and combined effects of T and 1,25(OH)₂D₃ on global gene expression in LNCaP prostate cancer cells were assessed.

Results

Stringent statistical analysis identifies a cohort of genes that lack one or both androgen response elements (AREs) or vitamin D response elements (VDREs) in their promoters, which are nevertheless differentially regulated by both steroids (either additively or synergistically). This suggests that mechanisms in addition to VDR- and AR-mediated transcription are responsible for the modulation of gene expression. Microarray analysis shows that fifteen miRNAs are also differentially regulated by 1,25(OH)₂D₃ and T. Among these miR-22, miR-29ab, miR-134, miR-1207-5p and miR-371-5p are up regulated, while miR-17 and miR-20a, members of the miR-17/92 cluster are down regulated. A number of genes implicated in cell cycle progression, lipid synthesis and accumulation and calcium homeostasis are among the mRNA targets of these miRNAs. Thus, in addition to their well characterized effects on transcription, mediated by either or both cognate nuclear receptors, 1,25(OH)₂D₃ and T regulate the steady state mRNA levels by modulating miRNA-mediated mRNA degradation, generating attenuation feedback loops that result in global changes in mRNA and protein levels. Changes in genes involved in calcium homeostasis may have specific clinical importance since the second messenger Ca²⁺ is known to modulate various cellular processes, including cell proliferation, cell death and cell motility, which affects prostate cancer tumor progression and responsiveness to therapy.

Conclusions

These data indicate that these two hormones combine to drive a differentiated phenotype, and reinforce the idea that the age dependent decline in both hormones results in the de-differentiation of prostate tumor cells, which results in increased proliferation, motility and invasion common to aggressive tumors. These studies also reinforce the potential importance of miRNAs in prostate cancer progression and therapeutic outcomes.

miR-146a is a significant brake on autoimmunity, myeloproliferation, and cancer in mice

Excessive or inappropriate activation of the immune system can be deleterious to the organism, warranting multiple molecular mechanisms to control and properly terminate immune responses. MicroRNAs (miRNAs), ∼22-nt-long noncoding RNAs, have recently emerged as key posttranscriptional regulators, controlling diverse biological processes, including responses to non-self. In this study, we examine the biological role of miR-146a using genetically engineered mice and show that targeted deletion of this gene, whose expression is strongly up-regulated after immune cell maturation and/or activation, results in several immune defects. Collectively, our findings suggest that miR-146a plays a key role as a molecular brake on inflammation, myeloid cell proliferation, and oncogenic transformation.

Polymorphism of the pre-miR-146a is associated with risk of cervical cancer in a Chinese population

OBJECTIVE

MicroRNAs are tiny non-coding RNAs that reportedly play an important role in numerous physiological processes. A G>C polymorphism (rs2910164) is located on the passenger strand of the precursor of miR-146a, which could alter mature miR-146a expression. We hypothesized that a possible association exists between miR-146a gene polymorphisms and cervical cancer risk in a population-based control study of female residents in Jiangsu Province.

METHODS

The subjects included 447 cervical cancer cases and 443 cancer-free controls with frequency matched by age. We genotyped the functional polymorphism of miR-146a (rs2910164) by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) method, and used a sample of 24 cervical cancer tissue to test the expression of miR-146a by real-time quantitative reverse transcription.

RESULTS

Our study indicated that the subjects carrying GG homozygote had a 1.496-fold increased risk than those carrying CG/CC genotypes (95% CI=1.068-2.095). Moreover, miR-146a quantification showed that the carriers of GG genotype had obviously more reduced miR-146a expression level compared with the carriers of CC genotype.

CONCLUSION

Our study suggests that the risk of cervical cancer in a Chinese population partly results from miRNA-146a expression deviation in vivo, being caused by common polymorphism in miR-146a. This is an initial study to indicate that miR-146a (rs2910164) might contribute to cervical cancer susceptibility.

Metastasis suppressor genes at the interface between the environment and tumor cell growth

The molecular mechanisms and genetic programs required for cancer metastasis are sometimes overlapping, but components are clearly distinct from those promoting growth of a primary tumor. Every sequential, rate-limiting step in the sequence of events leading to metastasis requires coordinated expression of multiple genes, necessary signaling events, and favorable environmental conditions or the ability to escape negative selection pressures. Metastasis suppressors are molecules that inhibit the process of metastasis without preventing growth of the primary tumor. The cellular processes regulated by metastasis suppressors are diverse and function at every step in the metastatic cascade. As we gain knowledge into the molecular mechanisms of metastasis suppressors and cofactors with which they interact, we learn more about the process, including appreciation that some are potential targets for therapy of metastasis, the most lethal aspect of cancer. Until now, metastasis suppressors have been described largely by their function. With greater appreciation of their biochemical mechanisms of action, the importance of context is increasingly recognized especially since tumor cells exist in myriad microenvironments. In this chapter, we assemble the evidence that selected molecules are indeed suppressors of metastasis, collate the data defining the biochemical mechanisms of action, and glean insights regarding how metastasis suppressors regulate tumor cell communication to-from microenvironments.

MiR-146a in Immunity and Disease

MicroRNAs (miRNAs) are regulatory molecules able to influence all aspects of the biology of a cell. They have been associated with diseases such as cancer, viral infections, and autoimmune diseases, and in recent years, they also emerged as important regulators of immune responses. MiR-146a in particular is rapidly gaining importance as a modulator of differentiation and function of cells of the innate as well as adaptive immunity. Given its importance in regulating key cellular functions, it is not surprising that miR-146a expression was also found dysregulated in different types of tumors. In this paper, we summarize recent progress in understanding the role of miR-146a in innate and adaptive immune responses, as well as in disease.

Down-regulation of BRCA1 expression by miR-146a and miR-146b-5p in triple negative sporadic breast cancers

Germ-line mutations in the BRCA1 gene strongly predispose women to breast cancer (lifetime risk up to 80%). Furthermore, the BRCA1 protein is absent or present at very low levels in about one third of sporadic breast cancers. However, the mechanisms underlying BRCA1 somatic inactivation appear multiple and are still not fully understood. We report here the involvement of miR-146a and miR-146b-5p that bind to the same site in the 3′UTR of BRCA1 and down-regulate its expression as demonstrated using reporter assays. This was further confirmed with the endogenous BRCA1 gene by transfecting microRNA (miRNA) precursors or inhibitors in mammary cell lines. This down-regulation was accompanied by an increased proliferation and a reduced homologous recombination rate, two processes controlled by BRCA1. Furthermore, we showed that the highest levels of miR-146a and/or miR-146b-5p are found in basal-like mammary tumour epithelial cell lines and in triple negative breast tumours, which are the closest to tumours arising in carriers of BRCA1 mutations. This work provides further evidence for the involvement of miRNAs in sporadic breast cancer through down-regulation of BRCA1.

Downregulation of miR-195 correlates with lymph node metastasis and poor prognosis in colorectal cancer

miR-195, one of the miR-16/15/195/424/497 family members, has been shown to play an important role in tumorigenesis, as a tumor suppressor. Here, we assess miR-195 expression in colorectal cancer, which has not been investigated before, and its clinical significance including survival analysis. The in vivo significance of expression of miR-16/15/195/424/497 in matched normal and tumor tissues of colorectal cancers was evaluated using a quantitative real-time RT-PCR. Two colorectal cancer cell lines and 85 colorectal cancer and paired normal patient samples with detailed clinical follow-up information were selected. The statistical significance of these markers for disease prognosis was evaluated using a two-tailed, paired Wilcoxon test. A Kaplan-Meier survival curve was generated following a logrank test. As a result, miR-424 was significantly over-expressed, while miR-15a, miR-15b, miR-16, and miR-195 were downregulated in tumors compared with normal colorectal samples (all P < 0.01). Reduced expression of miR-195 occurred more often in patients with lymph node metastasis and advanced tumor stage (all P < 0.01). Kaplan-Meier survival analysis indicated that patients with reduced miR-195 had a poor overall survival (P < 0.01). Moreover, the multivariate analysis showed that reduced expression of miR-195 was an independent predictor of overall survival. Our data indicate the potential of miR-195 as a novel diagnostic or prognostic biomarker for CRC.

TGF-β1 mediated activation of Rho kinase induces TGF-β2 and endothelin-1 expression in human hepatic stellate cells

BACKGROUND & AIMS

TGF-β1 a key pro-fibrotic factor activates signaling via the canonical ALK/SMAD as well as the Rho GTPase pathways. Rho kinase is a major downstream effector of Rho GTPase signaling. To understand the contribution of Rho kinase activation towards the synthesis of fibrotic mediators by hepatic stellate cells (HSC), we first profiled activated HSC and fibrotic liver tissues to identify common transcripts that were most significantly up-regulated across all samples. We then applied a pharmacologic as well as a genomics approach in a TGF-β1 activated human HSC line (LX-2) to study the involvement of Rho kinase signaling in the expression of a subset of these up-regulated fibrotic genes.

METHODS

Total RNA was profiled using microarray chips. Data analysis was performed using Ingenuity Pathway Analysis software. LX-2 cells were activated with 10 ng/ml of TGF-β1 for 24 h. Activation of downstream pathways was assessed by Western blotting with phospho-specific target biomarker antibodies. Targeted knockdown of Rho kinase isoforms 1 and 2 was achieved with RNAi. Secreted levels of endothelin-1, TGF-β2, and thrombospondin-1 were measured by ELISA.

RESULTS

TGF-β1 activated Rho kinase and Smad pathways in LX-2 cells. The syntheses of endothelin-1 and TGF-β2 were significantly inhibited in TGF-β1 treated LX-2 cells, by isoform non-selective Rho kinase inhibitors. siRNA knockdown of each isoform suggested that endothelin-1 synthesis was largely mediated by the Rho kinase-1 isoform, while both isoforms contributed to the synthesis of TGF-β2.

CONCLUSIONS

The TGF-β1 mediated secretion of endothelin-1 and TGF-β2 is mediated by Rho kinase activation in human HSC.

MicroRNA-146a is down-regulated in gastric cancer and regulates cell proliferation and apoptosis

Aberrant expression of microRNA-146a (miR-146a) has been reported to be involved in development and progression in various types of cancers, but its role in gastric cancer has not been fully elucidated. The purpose of this study was to investigate the levels of miR-146a expression and its function in human gastric cancer. Quantitative real-time polymerase chain reaction was used to detect the levels of miR-146a expression in gastric cancer tissue samples and cell lines. The cell growth rate of MKN-45 gastric cancer cells transfected with miR-146a mimics was examined by MTT assay. The effects of miR-146a on cell cycle and apoptosis were assessed by FACS analyses in MKN-45 cells. Thirty-six of 43 gastric cancer tissue samples (84%) showed decreased expression of miR-146a. We found low expression of miR-146a was correlated with increased tumor size (P = 0.006) and poor differentiation (P = 0.010) in gastric cancer. Overall survival time of patients with high miR-146a expression was significantly longer than that of patients with low expression of miR-146a (P = 0.011). The MTT assay showed that introduction of miR-146a inhibited cell proliferation in MKN-45 cells (P < 0.05). The proportion of apoptotic cells induced by transfection of miR-146a mimics were greater than that induced by transfection of the negative control mimics (11.9 vs. 5.9%). Our results suggested that miR-146a has potential as a novel suppressor gene in gastric cancer and its down-regulation may promote the progression of gastric cancer.

The guardians of the genome (p53, TA-p73, and TA-p63) are regulators of tumor suppressor miRNAs network

The tumor suppressor p53 homologues, TA-p73, and p63 have been shown to function as tumor suppressors. However, how they function as tumor suppressors remains elusive. Here, I propose a number of tumor suppressor pathways that illustrate how the TA-p73 and p63 could function as negative regulators of invasion, metastasis, and cancer stem cells (CSCs) proliferation. Furthermore, I provide molecular insights into how TA-p73 and p63 could function as tumor suppressors. Remarkably, the guardians--p53, p73, and p63--of the genome are in control of most of the known tumor suppressor miRNAs, tumor suppressor genes, and metastasis suppressors by suppressing c-myc through miR-145/let-7/miR-34/TRIM32/PTEN/FBXW7. In particular, p53 and TA-p73/p63 appear to upregulate the expression of (1) tumor suppressor miRNAs, such as let-7, miR-34, miR-15/16a, miR-145, miR-29, miR-26, miR-30, and miR-146a; (2) tumor suppressor genes, such as PTEN, RBs, CDKN1a/b/c, and CDKN2a/b/c/d; (3) metastasis suppressors, such as Raf kinase inhibitory protein, CycG2, and DEC2, and thereby they enlarge their tumor suppressor network to inhibit tumorigenesis, invasion, angiogenesis, migration, metastasis, and CSCs proliferation.

MicroRNA in prostate, bladder, and kidney cancer: a systematic review

CONTEXT

MicroRNAs (miRNA) are noncoding RNAs that post-transcriptionally regulate gene expression. Their altered expression and function have been observed in most urologic cancers. MiRNAs represent potential disease biomarkers and novel therapeutic targets.

OBJECTIVE

To review and evaluate the evidence implicating miRNAs in the pathogenesis of prostate cancer (PCa), bladder cancer (BCa), and renal cancer.

EVIDENCE ACQUISITION

A systematic review was performed using PubMed and Embase to search for reports using strings for microRNA, non-coding RNA, cancer, prostate, bladder, and renal cancer. Identified manuscripts were retrieved and references searched. Selected studies were required to concentrate on the role of miRNA in these urologic cancers.

EVIDENCE SYNTHESIS

We reviewed articles that focus on this topic. More than 40 miRNAs have been implicated in urologic cancer and many target common carcinogenic pathways. In particular, apoptosis avoidance, cell proliferation, epithelial-to-mesenchymal transition, angiogenic signalling, and the generation of androgen independence are targeted or facilitated by more than one miRNA. Little work has been done to evaluate the translational applications for this knowledge to date. Novel therapeutic strategies have been developed and are under investigation to selectively modulate miRNAs; such work would potentially enable personalised tumour therapy.

CONCLUSIONS

MiRNAs appear to be important modulators of urologic cancer. Their expression is frequently altered in these tumours, and many are functionally implicated in their pathogenesis. They require evaluation to determine the translational role and therapeutic potential for this knowledge.

MicroRNA-100 expression is independently related to biochemical recurrence of prostate cancer

PURPOSE

Abnormal miRNA expression has emerged as crucial factors in carcinogenesis and is important in the comprehension of prostate cancer behavior. We determined the correlation of miRNA expression profiles with prostate cancer progression.

MATERIALS AND METHODS

We studied frozen specimens from 49 patients treated for prostate cancer with radical prostatectomy. We intentionally chose 28 men without and 21 with biochemical recurrence, defined as prostate specific antigen greater than 0.2 ng/ml. The expression of 14 miRNAs was determined by quantitative reverse transcriptase-polymerase chain reaction. All radical prostatectomy specimens were studied in toto to determine tumor volume, Gleason score and 2002 TNM pathological stage. Benign prostate tissue from benign prostatic hyperplasia served as a control.

RESULTS

Four miRNAs were related to tumor recurrence. Using the Cox regression test the risk of recurrence was 3.0, 3.3, 2.7 and 3.4 for high levels of miR-100, miR-145, miR-191 and miR-let7c, respectively. When considering statistically significant clinical variables on univariate analysis of biochemical-free survival, prostate specific antigen and tumor volume, results revealed that miR-100 and tumor volume were independently related to tumor recurrence.

CONCLUSIONS

A high level of miR-100 is related to biochemical recurrence of localized prostate cancer in patients treated with radical prostatectomy. The role of miR-100 during carcinogenesis must be resolved in future studies to better understand the molecular pathways in which miR-100 is involved. This may open the possibility of using it as a prognostic marker and inspire the development of a target drug.

Impaired miR-146a expression links subclinical inflammation and insulin resistance in Type 2 diabetes

Type 2 diabetes patients exhibit subclinical inflammation but the regulatory mechanisms are poorly understood. We sought to evaluate the role of miR-146a expression along with its downstream proinflammatory signals in relation to glycemic control and insulin resistance. Study subjects (n = 20 each) comprised of clinically well characterized Type 2 diabetes patients and control non-diabetic subjects. miRNA and mRNA expression levels were probed in peripheral blood mononuclear cells (PBMC) by Real-time RT-PCR and plasma levels of TNFα and IL-6 were measured by ELISA. The miR-146a expression levels were significantly decreased in PBMCs from patients with Type 2 diabetes compared to control subjects. Among the target genes of miR-146a, TRAF-6 mRNA expression was significantly increased in patients with Type 2 diabetes while there was no significant difference in the mRNA levels of IRAK1 in the study groups. In contrast, there were significantly increased levels of NFκB expression in patients with Type 2 diabetes. There was an increased trend in the levels of TNFα and IL-6 mRNA in patients with type 2 diabetes. While SOCS-3 mRNA levels increased, plasma TNFα and IL-6 levels were also significantly higher in patients with type 2 diabetes. miR-146a expression was negatively correlated to glycated hemoglobin, insulin resistance, TRAF6, and NFκB mRNA levels and circulatory levels of TNFα and IL-6. Reduced miR-146a levels are associated with insulin resistance, poor glycemic control, and several proinflammatory cytokine genes and circulatory levels of TNFα and IL-6 in Asian Indian Type 2 diabetic patients.

Metastasis suppressors in human benign prostate, intraepithelial neoplasia, and invasive cancer: their prospects as therapeutic agents

Despite advances in diagnosis and treatment of prostate cancer, development of metastases remains a major clinical challenge. Research efforts are dedicated to overcome this problem by understanding the molecular basis of the transition from benign cells to prostatic intraepithelial neoplasia (PIN), localized carcinoma, and metastatic cancer. Identification of proteins that inhibit dissemination of cancer cells will provide new perspectives to define novel therapeutics. Development of antimetastatic drugs that trigger or mimic the effect of metastasis suppressors represents new therapeutic approaches to improve patient survival. This review focuses on different biochemical and cellular functions of metastasis suppressors known to play a role in prostate carcinogenesis and progression. Ten putative metastasis suppressors implicated in prostate cancer are discussed. CD44s is decreased in both PIN and cancer; Drg-1, E-cadherin, KAI-1, RKIP, and SSeCKS show similar expression between benign epithelia and PIN, but are downregulated in invasive cancer; whereas, maspin, MKK4, Nm23 and PTEN are upregulated in PIN and downregulated in cancer. Moreover, the potential role of microRNA in prostate cancer progression, the understanding of the cellular distribution and localization of metastasis suppressors, their mechanism of action, their effect on prostate invasion and metastasis, and their potential use as therapeutics are addressed.

miR-99 family of MicroRNAs suppresses the expression of prostate-specific antigen and prostate cancer cell proliferation

MicroRNAs (miRNA) have been globally profiled in cancers but there tends to be poor agreement between studies including in the same cancers. In addition, few putative miRNA targets have been validated. To overcome the lack of reproducibility, we profiled miRNAs by next generation sequencing and locked nucleic acid miRNA microarrays and verified concordant changes by quantitative RT-PCR. Notably, miR-125b and the miR-99 family members miR-99a, -99b, and -100 were downregulated in all assays in advanced prostate cancer cell lines relative to the parental cell lines from which they were derived. All four miRNAs were also downregulated in human prostate tumor tissue compared with normal prostate. Transfection of miR-99a, -99b, or -100 inhibited the growth of prostate cancer cells and decreased the expression of prostate-specific antigen (PSA), suggesting potential roles as tumor suppressors in this setting. To identify targets of these miRNAs, we combined computational prediction of potential targets with experimental validation by microarray and polyribosomal loading analysis. Three direct targets of the miR-99 family that were validated in this manner were the chromatin-remodeling factors SMARCA5 and SMARCD1 and the growth regulatory kinase mTOR. We determined that PSA is posttranscriptionally regulated by the miR-99 family members, at least partially, by repression of SMARCA5. Together, our findings suggest key functions and targets of miR-99 family members in prostate cancer suppression and prognosis.

The microRNA miR-139 suppresses metastasis and progression of hepatocellular carcinoma by down-regulating Rho-kinase 2

BACKGROUND & AIMS

We investigated mechanisms of hepatocellular carcinoma (HCC) metastasis and identified an antimetastatic microRNA (miRNA), miR-139, that is down-regulated in human HCC samples.

METHODS

Effects of stable and transient expression of miRNA-139 and its inhibitors were studied in the human HCC cell lines SMMC-7721 and BEL7402; cells were analyzed for migration and invasion. Liver samples from patients with metastatic HCC were analyzed for levels of miRNA-139; data were compared with survival data using the Kaplan-Meier method and compared between groups by the log-rank test. Tumor formation and metastasis from human HCC MHCC97L cells that did or did not express miR-139 were analyzed in mice.

RESULTS

Down-regulation of miR-139 in HCC was associated significantly with poor prognosis of patients and features of metastatic tumors, including venous invasion, microsatellite formation, absence of tumor encapsulation, and reduced differentiation. miR-139 expression was reduced in metastatic HCC tumors compared with primary tumors. Overexpression of miR-139 in HCC cells significantly reduced cell migration and invasion in vitro and the incidence and severity of lung metastasis from orthotopic liver tumors in mice. miR-139 interacted with the 3' untranslated region of Rho-kinase 2 (ROCK2) and reduced its expression in HCC cells. Levels of miR-139 were correlated inversely with ROCK2 protein in human HCC samples. Overexpression of miR-139 did not inhibit HCC cell motility when ROCK2 was knocked down.

CONCLUSIONS

The microRNA miR-139 interacts with ROCK2 and reduces its expression in HCC cells. Down-regulation of miR-139 increased the invasive abilities of HCC cells in vitro and HCC metastasis in vivo. Expression of miR-139 is reduced in human metastatic HCC samples and correlates with prognosis.

Steroid receptors and microRNAs: relationships revealed

MicroRNAs (miRNAs) are small non-coding RNAs that serve as post-transcriptional regulators of gene expression. They work predominantly by binding to complementary sequences in target messenger RNA (mRNA) 3' untranslated regions (UTRs) where they prevent translation or cause degradation of the message. Steroid hormone receptors (SHRs) are ligand-activated transcription factors that regulate genes in steroid responsive tissues. Recent studies demonstrate that SHRs regulate miRNAs, and in turn, miRNAs can regulate SHR expression and function. Mounting evidence indicates that miRNAs are intimately involved with SHRs, as they are with other transcription factors, often in double negative feedback loops. Investigators are just beginning to expose the details of these complex relationships and reveal the extent to which miRNAs are involved with SHRs in normal physiology and the pathobiology of steroid hormone responsive tissues.

MicroRNAs and Androgen Receptor 3' Untranslated Region: A Missing Link in Castration-resistant Prostate Cancer?

The ligand-activated transcription factor, androgen receptor (AR) plays a central role in the development and progression of prostate cancer. Prostate cancer initiates as an androgen-dependent disease and further accumulation of multiple sequential genetic and epigenetic alterations transform it into an aggressive, castration-resistant prostate cancer (CRPC). The molecular basis of the transition from androgen-dependent prostate cancer to CRPC remains unclear. However, it is apparent that AR plays a pivotal role in this alteration. The recent discovery that microRNAs (miRNAs) can target the function of AR suggests a functional role of these non-coding RNAs in the pathogenesis of prostate cancer. miRNAs usually function by targeting the 3' untranslated region (UTR) of a mRNA by base-pairing interactions and modulate translation either by destabilizing the message or by repression of protein synthesis in actively translating ribosomes. Here, we discuss the potential molecular pathways through which AR targeting miRNAs may promote CRPC. Modulation of AR expression by miRNAs presents a novel therapeutic option for prostate cancer, albeit it will likely be used in combination with the existing therapies.

Regulation of HMGA1 expression by microRNA-296 affects prostate cancer growth and invasion

PURPOSE

High-motility group AT-hook gene 1 (HMGA1) is a non-histone nuclear binding protein that is developmentally regulated. HMGA1 is significantly overexpressed in and associated with high grade and advance stage of prostate cancer (PC). The oncogenic role of HMGA1 is at least mediated through chromosomal instability and structural aberrations. However, regulation of HMGA1 expression is not well understood. Identification of microRNA-mediated HMGA1 regulation will provide a promising therapeutic target in treating PC.

EXPERIMENTAL DESIGN

In this study, we examined the functional relation between miR-296 and HMGA1 expression in several PC cell lines and a large PC cohort. We further examined the oncogenic property of HMGA1 regulated by miR-296.

RESULTS

Here we report that miR-296, a microRNA predicted to target HMGA1, specifically represses HMGA1 expression by promoting degradation and inhibiting HMGA1translation. Repression of HMGA1 by miR-296 is direct and sequence specific. Importantly, ectopic miR-296 expression significantly reduced PC cell proliferation and invasion, in part through the downregulation of HMGA1. Examining PC patient samples, we found an inverse correlation between HMGA1 and miR-296 expression: high levels of HMGA1 were associated with low miR-296 expression and strongly linked to more advanced tumor grade and stage.

CONCLUSIONS

Our results indicate that miR-296 regulates HMGA1 expression and is associated with PC growth and invasion.

Tumour suppressor microRNA-584 directly targets oncogene Rock-1 and decreases invasion ability in human clear cell renal cell carcinoma

Background:

The purpose of this study was to identify new tumour suppressor microRNAs (miRs) in clear cell renal cell carcinoma (ccRCC), carry out functional analysis of their suppressive role and identify their specific target genes.

Methods:

To explore suppressor miRs in RCC, miR microarray and real-time PCR were performed using HK-2 and A-498 cells. Cell viability, invasion and wound healing assays were carried out for functional analysis after miR transfection. To determine target genes of miR, we used messenger RNA (mRNA) microarray and target scan algorithms to identify target oncogenes. A 3′UTR luciferase assay was also performed. Protein expression of target genes in ccRCC tissues was confirmed by immunohistochemistry and was compared with miR-584 expression in ccRCC tissues.

Results:

Expression of miR-584 in RCC (A-498 and 769-P) cells was downregulated compared with HK-2 cells. Transfection of miR-584 dramatically decreased cell motility. The ROCK-1 mRNA was inhibited by miR-584 and predicted to be target gene. The miR-584 decreased 3′UTR luciferase activity of ROCK-1 and ROCK-1 protein expression. Low expression of miR-584 in ccRCC tissues was correlated with high expression of ROCK-1 protein. The knockdown of ROCK-1 by siRNA inhibited cell motility.

Conclusion:

miR-584 is a new tumour suppressor miR in ccRCC and inhibits cell motility through downregulation of ROCK-1.

microRNAs: tiny RNA molecules, huge driving forces to move the cell

Cell migration or movement is a highly dynamic cellular process, requiring precise regulation that is essential for a variety of biological processes. microRNAs (miRNAs) are a class of tiny non-coding RNA molecules that function as critical post-transcriptional regulators of gene expression. Emerging evidence demonstrates that miRNAs play important roles in cell migration and directly contribute to extracellular matrix (ECM) remodeling, cell adhesion, and cell signalling that controls cell migration by targeting a large number of protein-coding genes. Accordingly, the dysregulation of these miRNAs has been linked to several migration-related diseases. In this review, we summarize and highlight the recent advances concerning the roles and validated targets of miRNAs in the control of cell movement.

Metastamirs: a stepping stone towards improved cancer management

MicroRNAs (miRNAs) are non-coding RNAs that regulate protein expression. Aberrant miRNA expression in cancer has been well documented; miRNAs can act as oncogenes or tumor-suppressor genes, depending on the cellular context and target genes that they regulate, and are involved in tumor progression and metastasis. The potential mechanisms by which miRNAs are involved in tumor aggressiveness include migration, invasion, cell proliferation, epithelial-to-mesenchymal transition, angiogenesis and apoptosis. MiRNAs are involved in various cellular pathways and an miRNA can elicit more than one biological effect in a given cell. Existing data show the potential clinical utility of miRNAs as prognostic and predictive markers for aggressive and metastatic cancers. The stability of miRNAs in formalin-fixed, paraffin-embedded tissues and body fluids is advantageous for biomarker discovery and validation. In addition, miRNAs can be extracted from small biopsy specimens, which is a further advantage. Finally, miRNAs are potential therapeutic agents for personalized cancer management.

miRNAs in the pathogenesis of oncogenic human viruses

Tumor viruses are a class of pathogens with well established roles in the development of malignant diseases. Numerous bodies of work have highlighted miRNAs (microRNAs) as critical regulators of tumor pathways and it is clear that the dysregulation of cellular miRNA expression can promote tumor formation. Tumor viruses encode their own miRNAs and/or manipulate the expression of cellular miRNAs to modulate their host cell environment, thereby facilitating their respective infection cycles. The modulation of these miRNA responsive pathways, however, often influences certain signal transduction cascades in ways that favor tumorigenesis. In this review, we discuss the roles of virally-encoded and virally-regulated cellular miRNAs in the respective viral life cycles and in virus associated pathogenesis.

MicroRNA Expression Profiling of Oral Carcinoma Identifies New Markers of Tumor Progression

Oral squamous cell carcinoma, the most frequently occurring malignant head and neck tumour, generally exhibits poor prognosis and metastases are the main cause of death. The discovery of reliable prognostic indicators of tumour progression could greatly improve clinical practice. MicroRNAs are involved in the regulation of basic cellular processes such as cell proliferation, differentiation, and apoptosis. Since miRNAs have been shown to be abnormally expressed in different tumours their importance as potential cancer prognostic indicators is increasing. To define the role of miRNA in OSCC tumours we investigated the expression profile of 15 OSCC (8 without metastasis and 7 with lymph node metastasis) using microarray analysis. Thirteen miRNA were significantly overexpressed (miR-489, miR-129, miR-23a, miR-214, miR-23b, miR-92, miR-25, miR-210, miR-212, miR-515, miR-146b, miR-21, miR-338) and 6 miRNA were underexpressed (miR-520h, miR-197, miR-378, miR-135b, miR-224, miR-34a) in oral tumours. Underexpression of mir-155, let-7i, mir-146a was found to characterize progression to metastastatic tumours. Further investigations will elucidate whether differentially expressed miRNAs will help to better classify OSCCs, thus improving diagnoses and patient care.

Genetic variation in microRNA genes and prostate cancer risk in North Indian population

Recent evidence indicates the involvement of microRNAs (miRNAs), in cell growth control, differentiation, and apoptosis, thus playing a role in tumorigenesis. Single-nucleotide polymorphisms (SNPs) located at miRNA-binding sites (miRNA-binding SNPs) are likely to affect the expression of the miRNA target and may contribute to the susceptibility of humans to common diseases. We genotyped SNPs hsa-mir196a2 (rs11614913), hsa-mir146a (rs2910164), and hsa-mir499 (rs3746444) in a case-control study including 159 prostate cancer patients and 230 matched controls. Patients with heterozygous genotype in hsa-mir196a2 and hsa-mir499, showed significant risk for developing prostate cancer (P = 0.01; OR = 1.70 and P ≤ 0.001; OR = 2.27, respectively). Similarly, the variant allele carrier was also associated with prostate cancer, (P = 0.01; OR = 1.66 and P ≤ 0.001; OR = 1.97, respectively) whereas, hsa-mir146a revealed no association in prostate cancer. None of the miRNA polymorphisms were associated with Gleason grade and bone metastasis. This is the first study on Indian population substantially presenting that individual as well as combined genotypes of miRNA-related variants may be used to predict the risk of prostate cancer and may be useful for identifying patients at high risk.

Resveratrol decreases the levels of miR-155 by upregulating miR-663, a microRNA targeting JunB and JunD

An inflammatory component is present in the microenvironment of most neoplastic tissues, including those not causally related to an obvious inflammatory process. Several microRNAs, and especially miR-155, play an essential role in both the innate and adaptative immune response. Resveratrol (trans-3,4',5-trihydroxystilbene) is a natural antioxidant with anti-inflammatory properties that is currently at the stage of preclinical studies for human cancer prevention. Here, we establish that, in human THP-1 monocytic cells as well as in human blood monocytes, resveratrol upregulates miR-663, a microRNA potentially targeting multiple genes implicated in the immune response. In THP-1 cells, miR-663 decreases endogenous activator protein-1 (AP-1) activity and impairs its upregulation by lipopolysaccharides (LPS), at least in part by directly targeting JunB and JunD transcripts. We further establish that the downregulation of AP-1 activity by resveratrol is miR-663 dependent and that the effects of resveratrol on both AP-1 activity and JunB levels are dose dependent. Finally, we show that resveratrol impairs the upregulation of miR-155 by LPS in a miR-663-dependent manner. Given the role of miR-155 in the innate immune response and the fact that it is upregulated in many cancers, our results suggest that manipulating miR-663 levels may help to optimize the use of resveratrol as both an anti-inflammatory and anticancer agent against malignancies associated with high levels of miR-155.

Pro-oncogenic and anti-oncogenic pathways: opportunities and challenges of cancer therapy

Carcinogenesis is the uncontrolled growth of cells gaining the potential to invade and disrupt vital tissue functions. This malignant process includes the occurrence of 'unwanted' gene mutations that induce the transformation of normal cells, for example, by overactivation of pro-oncogenic pathways and inactivation of tumor-suppressive or anti-oncogenic pathways. It is now recognized that the number of major signaling pathways that control oncogenesis is not unlimited; therefore, suppressing these pathways can conceivably lead to a cancer cure. However, the clinical application of cancer intervention has not matched up to scientific expectations. Increasing numbers of studies have revealed that many oncogenic-signaling elements show double faces, in which they can promote or suppress cancer pathogenesis depending on tissue type, cancer stage, gene dosage and their interaction with other players in carcinogenesis. This complexity of oncogenic signaling poses challenges to traditional cancer therapy and calls for considerable caution when designing an anticancer drug strategy. We propose future oncology interventions with the concept of integrative cancer therapy.