MicroRNA-dependent regulation of PTEN after arsenic trioxide treatment in bladder cancer cell line T24

Epigenetic and Immunological Features of Bladder Cancer

Bladder cancer (BLCA) is one of the most common types of malignant tumors of the urogenital system in adults. Globally, the incidence of BLCA is more than 500,000 new cases worldwide annually, and every year, the number of registered cases of BLCA increases noticeably. Currently, the diagnosis of BLCA is based on cystoscopy and cytological examination of urine and additional laboratory and instrumental studies. However, cystoscopy is an invasive study, and voided urine cytology has a low level of sensitivity, so there is a clear need to develop more reliable markers and test systems for detecting the disease with high sensitivity and specificity. Human body fluids (urine, serum, and plasma) are known to contain significant amounts of tumorigenic nucleic acids, circulating immune cells and proinflammatory mediators that can serve as noninvasive biomarkers, particularly useful for early cancer detection, follow-up of patients, and personalization of their treatment. The review describes the most significant advances in epigenetics of BLCA.

Particulate hexavalent chromium alters microRNAs in human lung cells that target key carcinogenic pathways

Hexavalent chromium [Cr(VI)] is a global environmental pollutant and human lung carcinogen. However, the mechanisms of Cr(VI) carcinogenesis are not well defined. Cr(VI)-altered gene expression has been reported in the literature and is implicated in numerous mechanisms of Cr(VI) carcinogenesis. MicroRNAs (miRNAs) play a key role in controlling gene expression and are associated with carcinogenic mechanisms. To date no studies have evaluated global changes in miRNA expression in human cells after Cr(VI) exposure. We used RNA sequencing to evaluate how a particulate Cr(VI) compound (zinc chromate), the most potent form of Cr(VI), alters global miRNA expression after acute (24 h) or prolonged (72 and 120 h) exposure to 0.1, 0.2 and 0.3 μg/cm² zinc chromate in an immortalized, non-cancerous human lung cell line (WTHBF-6). Particulate Cr(VI) significantly affected expression of miRNAs at all time points and concentrations tested. We also found the number of significantly downregulated miRNAs increased in a time- and concentration-dependent manner and many miRNAs were upregulated after 24 h exposure at the intermediate concentration tested. Pathway analyses of the differentially expressed miRNAs predicted miRNAs target pathways of Cr(VI) carcinogenesis in a time- and concentration-dependent manner. These data are the first to evaluate global changes in miRNA expression in human lung cells after Cr(VI) exposure and indicate miRNAs may play a key role in pathways of Cr(VI) carcinogenesis.

Arsenic co-carcinogenesis: Inhibition of DNA repair and interaction with zinc finger proteins

Arsenic is widely present in the environment and is associated with various population health risks including cancers. Arsenic exposure at environmentally relevant levels enhances the mutagenic effect of other carcinogens such as ultraviolet radiation. Investigation on the molecular mechanisms could inform the prevention and intervention strategies of arsenic carcinogenesis and co-carcinogenesis. Arsenic inhibition of DNA repair has been demonstrated to be an important mechanism, and certain DNA repair proteins have been identified to be extremely sensitive to arsenic exposure. This review will summarize the recent advances in understanding the mechanisms of arsenic carcinogenesis and co-carcinogenesis, including DNA damage induction and ROS generation, particularly how arsenic inhibits DNA repair through an integrated molecular mechanism which includes its interactions with sensitive zinc finger DNA repair proteins.

Arsenic: A Global Environmental Challenge

Arsenic is a naturally occurring metalloid and one of the few metals that can be metabolized inside the human body. The pervasive presence of arsenic in nature and anthropogenic sources from agricultural and medical use have perpetuated human exposure to this toxic and carcinogenic element. Highly exposed individuals are susceptible to various illnesses, including skin disorders; cognitive impairment; and cancers of the lung, liver, and kidneys. In fact, across the globe, approximately 200 million people are exposed to potentially toxic levels of arsenic, which has prompted substantial research and mitigation efforts to combat this extensive public health issue. This review provides an up-to-date look at arsenic-related challenges facing the global community, including current sources of arsenic, global disease burden, arsenic resistance, and shortcomings of ongoing mitigation measures, and discusses potential next steps.

Does Arsenic Contamination Affect DNA Methylation Patterns in a Wild Bird Population? An Experimental Approach

Pollutants, such as toxic metals, negatively influence organismal health and performance, even leading to population collapses. Studies in model organisms have shown that epigenetic marks, such as DNA methylation, can be modulated by various environmental factors, including pollutants, influencing gene expression, and various organismal traits. Yet experimental data on the effects of pollution on DNA methylation from wild animal populations are largely lacking. We here experimentally investigated for the first time the effects of early-life exposure to environmentally relevant levels of a key pollutant, arsenic (As), on genome-wide DNA methylation in a wild bird population. We experimentally exposed nestlings of great tits (Parus major) to arsenic during their postnatal developmental period (3 to 14 days post-hatching) and compared their erythrocyte DNA methylation levels to those of respective controls. In contrast to predictions, we found no overall hypomethylation in the arsenic group. We found evidence for loci to be differentially methylated between the treatment groups, but for five CpG sites only. Three of the sites were located in gene bodies of zinc finger and BTB domain containing 47 (ZBTB47), HIVEP zinc finger 3 (HIVEP3), and insulin-like growth factor 2 mRNA binding protein 1 (IGF2BP1). Further studies are needed to evaluate whether epigenetic dysregulation is a commonly observed phenomenon in polluted populations and what are the consequences for organism functioning and for population dynamics.

Does Arsenic Contamination Affect DNA Methylation Patterns in a Wild Bird Population? An Experimental Approach

Pollutants, such as toxic metals, negatively influence organismal health and performance, even leading to population collapses. Studies in model organisms have shown that epigenetic marks, such as DNA methylation, can be modulated by various environmental factors, including pollutants, influencing gene expression, and various organismal traits. Yet experimental data on the effects of pollution on DNA methylation from wild animal populations are largely lacking. We here experimentally investigated for the first time the effects of early-life exposure to environmentally relevant levels of a key pollutant, arsenic (As), on genome-wide DNA methylation in a wild bird population. We experimentally exposed nestlings of great tits (Parus major) to arsenic during their postnatal developmental period (3 to 14 days post-hatching) and compared their erythrocyte DNA methylation levels to those of respective controls. In contrast to predictions, we found no overall hypomethylation in the arsenic group. We found evidence for loci to be differentially methylated between the treatment groups, but for five CpG sites only. Three of the sites were located in gene bodies of zinc finger and BTB domain containing 47 (ZBTB47), HIVEP zinc finger 3 (HIVEP3), and insulin-like growth factor 2 mRNA binding protein 1 (IGF2BP1). Further studies are needed to evaluate whether epigenetic dysregulation is a commonly observed phenomenon in polluted populations and what are the consequences for organism functioning and for population dynamics.

Epigenomic and Metabolomic Integration Reveals Dynamic Metabolic Regulation in Bladder Cancer

Bladder cancer (BC) represents a clinical, social, and economic challenge due to tumor-intrinsic characteristics, limitations of diagnostic techniques and a lack of personalized treatments. In the last decade, the use of liquid biopsy has grown as a non-invasive approach to characterize tumors. Moreover, the emergence of omics has increased our knowledge of cancer biology and identified critical BC biomarkers. The rewiring between epigenetics and metabolism has been closely linked to tumor phenotype. Chromatin remodelers interact with each other to control gene silencing in BC, but also with stress-inducible factors or oncogenic signaling cascades to regulate metabolic reprogramming towards glycolysis, the pentose phosphate pathway, and lipogenesis. Concurrently, one-carbon metabolism supplies methyl groups to histone and DNA methyltransferases, leading to the hypermethylation and silencing of suppressor genes in BC. Conversely, α-KG and acetyl-CoA enhance the activity of histone demethylases and acetyl transferases, increasing gene expression, while succinate and fumarate have an inhibitory role. This review is the first to analyze the interplay between epigenome, metabolome and cell signaling pathways in BC, and shows how their regulation contributes to tumor development and progression. Moreover, it summarizes non-invasive biomarkers that could be applied in clinical practice to improve diagnosis, monitoring, prognosis and the therapeutic options in BC.

Novel Mechanistic Insights into the Anti-cancer Mode of Arsenic Trioxide

Arsenic, a naturally-occurring toxic element, and a traditionally-used drug, has received a great deal of attention worldwide due to its curative anti-cancer properties in patients with acute promyelocytic leukemia. Among the arsenicals, arsenic trioxide has been most widely used as an anti-cancer drug. Recent advances in cancer therapeutics have led to a paradigm shift away from traditional cytotoxic drugs towards the targeting of proteins closely associated with driving the cancer phenotype. Due to the diverse anti-cancer effects of ATO on different types of malignancies, numerous studies have made efforts to uncover the mechanisms of ATO-induced tumor suppression. From in vitro cellular models to studies in clinical settings, ATO has been extensively studied. The outcomes of these studies have opened doors to establishing improved molecular-targeted therapies for cancer treatment. The efficacy of ATO has been augmented by combination with other drugs. In this review, we discuss recent arsenic-based cancer therapies and summarize the novel underlying molecular mechanisms of the anti-cancer effects of ATO.

Role of miRNA-19a in Cancer Diagnosis and Poor Prognosis

Cancer is a multifactorial disease that affects millions of people every year and is one of the most common causes of death in the world. The high mortality rate is very often linked to late diagnosis; in fact, nowadays there are a lack of efficient and specific markers for the early diagnosis and prognosis of cancer. In recent years, the discovery of new diagnostic markers, including microRNAs (miRNAs), has been an important turning point for cancer research. miRNAs are small, endogenous, non-coding RNAs that regulate gene expression. Compelling evidence has showed that many miRNAs are aberrantly expressed in human carcinomas and can act with either tumor-promoting or tumor-suppressing functions. miR-19a is one of the most investigated miRNAs, whose dysregulated expression is involved in different types of tumors and has been potentially associated with the prognosis of cancer patients. The aim of this review is to investigate the role of miR-19a in cancer, highlighting its involvement in cell proliferation, cell growth, cell death, tissue invasion and migration, as well as in angiogenesis. On these bases, miR-19a could prove to be truly useful as a potential diagnostic, prognostic, and therapeutic marker.

Arsenic induced epigenetic changes and relevance to treatment of acute promyelocytic leukemia and beyond

Epigenetic alterations regulate gene expression without changes in the DNA sequence. It is well-demonstrated that aberrant epigenetic changes contribute to the leukemogenesis of acute promyelocytic leukemia (APL). Arsenic trioxide (ATO) is one of the most common drugs used in the frontline treatment of APL that act through targeting and destabilizing the PML/RARα oncofusion protein. ATO together with all-trans retinoic acid (ATRA) lead to durable remission of more than 90% non-high-risk APL patients, turning APL treatment into a paradigm of oncoprotein targeted cure. Although relapse and drug resistance in APL are yet to be resolved in the clinic, epigenetic machineries might hold the key to address this issue. Further, ATO also showed promising anticancer activities against a variety of malignancies, but its application is particularly restricted due to limited understanding of the mechanism. Thus, a thorough understanding of epigenetic mechanism behind anti-leukemic effects of ATO would benefit the development of ATO-based anticancer strategy. Role of ATRA on APL associated epigenetic alterations has been extensively studied and reviewed. Recently, accumulating evidence suggest that ATO also induces some epigenetic changes that might favor APL eradication. In this article, we comprehensively discuss arsenic induced epigenetic changes and its relevance in APL treatment and beyond, so as to provide novel insights into overcoming arsenic resistance in APL and promote application of this drug to other malignancies.

PTEN: What we know of the function and regulation of this onco-suppressor factor in bladder cancer?

Bladder cancer accounts for high morbidity and mortality around the world and its incidence rate is suggested to be higher in following years. A number of factors involve in bladder cancer development such as lifestyle and drugs. However, it appears that genetic factors play a significant role in bladder cancer development and progression. Phosphatase and tensin homolog (PTEN) is a cancer-related transcription factor that is corelated with reduced proliferation and invasion of cancer cells by negatively targeting PI3K/Akt/mTOR signaling pathway. In the present review, we aimed to explore the role of PTEN in bladder cancer cells and how upstream modulators affect PTEN in this life-threatening disorder. Down-regulation of PTEN is associated with poor prognosis, chemoresistance and progression of cancer cells. Besides, microRNAs, long non-coding RNAs, circular RNAs and other molecular pathways such as NF-kB are able to target PTEN in bladder cancer cells. Notably, anti-tumor drugs such as kaempferol, β-elemene and sorafenib upregulate the expression of PTEN to exert their inhibitory effects on bladder cancer cells.

Non-coding RNA in bladder cancer

Bladder cancer is the tenth most common cancer worldwide and has been associated with high mortality and morbidity. Although the treatment of bladder cancer is based on well-defined tumor classifications and gradings, patients still experience different clinical response. The heterogeneity of this disease calls for substantial research with more in-depth molecular characterization, with the hope of identifying new diagnostic and treatment options. In recent years, non-coding RNAs (ncRNAs), particularly, microRNAs (miRNAs), long non-coding RNA (lncRNAs), and circular RNAs (circRNAs) were found to be associated with bladder cancer occurrence and development. This review highlights the recent findings concerning ncRNAs and their relevance to the pathogenesis of bladder cancer. This may provide a foundation for developing highly specific diagnostic tools and more robust therapeutic strategies in the future.

MicroRNA profiling identifies biomarkers in head kidneys of common carp exposed to cadmium

Cadmium (Cd) is an increasingly important environmental pollutant due to its high toxicity to fish and aquatic animals. In the present study, we cultured common carp (Cyprinus carpio L.) in two groups, a control group and a Cd group, with the Cd group being exposed to Cd for 30 d. The antioxidant enzyme activities of T-AOC and CAT and the GSH content were differentially decreased during Cd exposure. miRNAome profiling indicated that 23 differentially expressed miRNAs were potential biomarkers for Cd exposure; 7 miRNAs were up-regulated, and 16 miRNAs were down-regulated. The expression levels of miR-122, novel-miR6, miR-193a-3p and miR-27a-5p in the Cd group were 0.43-fold, 0.47-fold, 0.49-fold and 2.4-fold greater than in the control group, respectively. qRT-PCR further detected that the expression levels of apoptosis-related genes, including BAX, BAD, BAK, CASPASE9 and PIDD, were differentially increased, while BCL2 was decreased. Western blot analysis showed that the protein expression levels of BAX and BAD were increased and that of BCL2 was differentially decreased during Cd exposure. Alterations in the levels of miR-122, novel-miR6, miR-193a-3p and miR-27a-5p expression may play an important role in diagnosing oxidative stress-induced apoptosis during Cd exposure in the head kidney. These markers may contribute to diagnosing the early stage of Cd exposure in common carp.

The 14q32 maternally imprinted locus is a major source of longitudinally stable circulating microRNAs as measured by small RNA sequencing

Understanding the normal temporal variation of serum molecules is a critical factor for identifying useful candidate biomarkers for the diagnosis and prognosis of chronic disease. Using small RNA sequencing in a longitudinal study of 66 women with no history of cancer, we determined the distribution and dynamics (via intraclass correlation coefficients, ICCs) of the miRNA profile over 3 time points sampled across 2-5 years in the course of the screening trial, UKCTOCS. We were able to define a subset of longitudinally stable miRNAs (ICC >0.75) that were individually discriminating of women who had no cancer over the study period. These miRNAs were dominated by those originating from the C14MC cluster that is subject to maternal imprinting. This assessment was not significantly affected by common confounders such as age, BMI or time to centrifugation nor alternative methods to data normalisation. Our analysis provides important benchmark data supporting the development of miRNA biomarkers for the impact of life-course exposure as well as diagnosis and prognostication of chronic disease.

Utility of Circulating Cell-Free RNA Analysis for the Characterization of Global Transcriptome Profiles of Multiple Myeloma Patients

In this study, we evaluated the utility of extracellular RNA (exRNA) derived from the plasma of multiple myeloma (MM) patients for whole transcriptome characterization. exRNA from 10 healthy controls (HC), five newly diagnosed (NDMM), and 12 relapsed and refractory (RRMM) MM patients were analyzed and compared. We showed that ~45% of the exRNA genes were protein-coding genes and ~85% of the identified genes were covered >70%. Compared to HC, we identified 632 differentially expressed genes (DEGs) in MM patients, of which 26 were common to NDMM and RRMM. We further identified 54 and 191 genes specific to NDMM and RRMM, respectively, and these included potential biomarkers such as LINC00863, MIR6754, CHRNE, ITPKA, and RGS18 in NDMM, and LINC00462, PPBP, RPL5, IER3, and MIR425 in RRMM, that were subsequently validated using droplet digital PCR. Moreover, single nucleotide polymorphisms and small indels were identified in the exRNA, including mucin family genes that demonstrated different rates of mutations between NDMM and RRMM. This is the first whole transcriptome study of exRNA in hematological malignancy and has provided the basis for the utilization of exRNA to enhance our understanding of the MM biology and to identify potential biomarkers relevant to the diagnosis and prognosis of MM patients.

MicroRNAs and their role in environmental chemical carcinogenesis

MicroRNAs (miRNAs) are a class of small, noncoding RNA species that play crucial roles across many biological processes and in the pathogenesis of major diseases, including cancer. Recent studies suggest that the expression of miRNA is altered by certain environmental chemicals, including metals, organic pollutants, cigarette smoke, pesticides and carcinogenic drugs. In addition, extensive studies have indicated the existence and importance of miRNA in different cancers, suggesting that cancer-related miRNAs could serve as potential markers for chemically induced cancers. The altered expression of miRNA was considered to be a vital pathogenic role in xenobiotic-induced cancer development. However, the significance of miRNA in the etiology of cancer and the exact mechanisms by which environmental factors alter miRNA expression remain relatively unexplored. Hence, understanding the interaction of miRNAs with environmental chemicals will provide important information on mechanisms underlying the pathogenesis of chemically induced cancers, and effectively diagnose and treat human cancers resulting from chronic or acute carcinogen exposure. This study presents the current evidence that the miRNA deregulation induced by various chemical carcinogens, different cancers caused by environmental carcinogens and the potentially related genes in the onset or progression of cancer. For each carcinogen, the specifically expressed miRNA may be considered as the early biomarkers of the cancer process. In this review, we also summarize various target genes of the altered miRNA, oncogenes or anti-oncogenes, and the existing evidence regarding the gene regulation mechanisms of cancer caused by environmentally induced miRNA alteration. The future perspective of miRNA may become attractive targets for the diagnosis and treatment of carcinogen-induced cancer.

miR-21-5p, miR-141-3p, and miR-205-5p levels in urine-promising biomarkers for the identification of prostate and bladder cancer

BACKGROUND

Early detection of cancers improves patients' survival and decreases the treatment cost. Unfortunately, the current methods for diagnosis of bladder and prostate cancers, two most common urothelial malignancies, suffer from a low sensitivity and specificity. MicroRNAs, as a group of endogenously produced non-coding RNAs, regulate gene expression and their expression is observed to be altered in many cancers and cancer progression phenomena. The remarkable stability of microRNAs in biofluids and their unique expression pattern in different pathological conditions make them an appealing, noninvasive diagnostic method in cancer diagnosis. Our objective is to identify microRNAs as biomarkers in urine samples of bladder and prostate cancers to improve the existing diagnostic methods in this field.

MATERIALS AND METHODS

In this study, urine samples from 110 men with either bladder (n = 45) or prostate (n = 23) cancer, benign prostatic hyperplasia (n = 22) and healthy controls (n = 20) were collected. qPCR was used to evaluate the expression level of miR-21-5p, miR-141-3p, and miR-205-5p in these samples. The sensitivity and specificity of these microRNAs were determined using ROC curve analysis.

RESULTS

The analysis of the data revealed that miR-21-5p, miR-141-3p, and miR-205-5p are differentially expressed in urine of bladder and prostate cancer patients. All these three microRNAs were upregulated in these samples and they were also able to differentiate benign prostatic hyperplasia from malignant cases. The statistical analyses revealed a good specificity for each individual microRNA.

CONCLUSION

The results show that these three urine-based microRNAs might be a good choice to implement a specific and non-invasive diagnostic tool for bladder and prostate cancer. The expression pattern of all three microRNAs was particularly useful to distinguish benign and invasive tumors in prostate cases. From the patients' perspective the improvement of the diagnostic situation is awaited eagerly.

Use of Circulating and Cellular miRNAs Expression in Forensic Sciences

The current practice in the field of forensic medicine imposes the use of modern investigation techniques. The complexity of laboratory investigation methods needed for a final result of the investigation in forensic medicine needed new biomarkers of higher specificity and selectivity. Such biomarkers are the microRNAs (miRNAs), short, non-coding RNAs composed of 19–24 nucleotides. Their characteristics, such as high stability, selectivity, and specificity for biological fluids, differ from tissue to tissue and for certain pathologies, turning them into the ideal candidate for laboratory techniques used in forensic medicine. In this paper, we wish to highlight the biochemical properties and the usefulness of miRNAs in forensic medicine.

Arsenic Exposure and Type 2 Diabetes: MicroRNAs as Mechanistic Links?

PURPOSE OF REVIEW

The goal of this review is to delineate the following: (1) the primary means of inorganic arsenic (iAs) exposure for human populations, (2) the adverse public health outcomes associated with chronic iAs exposure, (3) the pathophysiological connection between arsenic and type 2 diabetes (T2D), and (4) the incipient evidence for microRNAs as candidate mechanistic links between iAs exposure and T2D.

RECENT FINDINGS

Exposure to iAs in animal models has been associated with the dysfunction of several different cell types and tissues, including liver and pancreatic islets. Many microRNAs that have been identified as responsive to iAs exposure under in vitro and/or in vivo conditions have also been shown in independent studies to regulate processes that underlie T2D etiology, such as glucose-stimulated insulin secretion from pancreatic beta cells. Defects in insulin secretion could be, in part, associated with aberrant microRNA expression and activity. Additional in vivo studies need to be performed with standardized concentrations and durations of arsenic exposure in order to evaluate rigorously microRNAs as molecular drivers of iAs-associated diabetes.

Induction of the mesenchymal to epithelial transition by demethylation-activated microRNA-125b is involved in the anti-migration/invasion effects of arsenic trioxide on human chondrosarcoma

Background

In addition to treating acute promyelocytic leukemia, arsenic trioxide (ATO) suppresses other solid tumors, including chondrosarcoma. However, the effects of ATO on metastasis in chondrosarcoma cells, and the underlying molecular mechanisms remain unclear.

Methods

The effects of ATO on the migratory and invasive capacities of chondrosarcoma cells were investigated by Wound healing, Transwell and EMT assays. The expression of miR-125b in human chondrosarcoma tissues and cell lines was detected by real-time PCR analysis. Bisulfite sequencing analysis (BSP) was used to detect the effects of ATO on the expression of miR-125b. The gain-of-function and loss-of-function experiments were performed on chondrosarcoma cell lines to investigate the effects of miR-125b on chondrosarcoma invasion, and to determine whether signal transducer and activator of transcription 3(Stat3) mediates these effects. Dual-luciferase reporter assay was used to identify whether Stat3 is a direct target of miR-125b.

Results

MiR-125b was significantly downregulated in human metastatic chondrosarcoma tissues and cell lines but not in non-metastatic chondrosarcoma tissues. ATO up-regulates the expression of miR-125b by the demethylation of DNA. ATO induces MET and attenuates the invasive capacities of chondrosarcoma cells through miR-125b. Stat3 was verified as a direct target of miR-125b, which is involved in ATO regulating EMT-associated traits.

Conclusions

These findings, for the first time, provides evidence that the miR-125b-mediated inhibition of Stat3 is involved in the ATO-induced attenuation of metastasis in chondrosarcoma cells.

The role of microRNAs in bladder cancer

Bladder cancer (BC) is the fifth most common cancer worldwide and is associated with significant morbidity and mortality. The prognosis of muscle invasive BC is poor, and recurrence is common after radical surgery or chemotherapy. Therefore, new diagnostic methods and treatment modalities are critical. MicroRNAs (miRNAs), a class of small noncoding RNAs, regulate the expression of protein-coding genes by repressing translation or cleaving RNA transcripts in a sequence-specific manner. miRNAs have important roles in the regulation of genes involved in cancer development, progression, and metastasis. The availability of genomewide miRNA expression profiles by deep sequencing technology has facilitated rapid and precise identification of aberrant miRNA expression in BC. Indeed, several miRNAs that are either upregulated or downregulated have been shown to have associations with significant cancer pathways. Furthermore, many miRNAs, including those that can be detected in urine and blood, have been studied as potential noninvasive tumor markers for diagnostic and prognostic purposes. Here, we searched PubMed for publications describing the role of miRNAs in BC by using the keywords "bladder cancer" and "microRNA" on March 1, 2016. We found 374 papers and selected articles written in English in which the level of scientific detail and reporting were sufficient and in which novel findings were demonstrated. In this review, we summarize these studies from the point of view of miRNA-related molecular networks (specific miRNAs and their targets) and miRNAs as tumor markers in BC. We also discuss future directions of miRNA studies in the context of therapeutic modalities.

Circulating miR-205: a promising biomarker for the detection and prognosis evaluation of bladder cancer

MicroRNA (miRNA) expression profile analysis indicated that miR-205 was upregulated in bladder cancer tissue compared to healthy tissue. The aim of this study is to analyze value of circulating miR-205 for the detection and prognosis evaluation of bladder cancer (BC). Eighty-nine patients with BC and 56 healthy controls (HC) were enrolled in the study. miR-205 expression was determined using TaqMan quantitative real-time polymerase chain reaction assay and further correlated with patients' clinicopathological parameters and follow-up data. The results indicated that plasma miR-205 was upregulated in BC compared with HC (P < 0.001) and in muscle invasive BC (MIBC) compared to nonmuscle invasive BC (NMIBC) (P = 0.016). miR-205 yielded an area under the receiver-operating characteristic curve of 0.950 with 76.4 % sensitivity and 96.4 % specificity in discriminating BC from HC, and 0.668 with 57.1 % sensitivity and 77.0 % specificity in distinguishing MIBC from NMIBC. Plasma miR-205 expression was significantly associated with tumor stage (P < 0.001) and pathological grade (P = 0.048). The results indicated that BC patients with high miR-205 expression experienced shorter disease-free survival and disease-specific survival (P = 0.022 and P = 0.026; P = 0.027 and P = 0.034; respectively), which was not proven by multivariate Cox regression analysis (multi-Cox) (P = 0.0765 and P = 0.279, respectively). Log-rank test showed that NMIBC patients with high miR-205 expression experienced shorter cancer-free survival (P = 0.044). Log-rank test and univariate and multivariate Cox regression analyses did not indicate that high miR-205 expression in NMIBC patients was associated with cancer-specific survival (P = 0.079, P = 0.089, and P = 0.201, respectively). In conclusion, miR-205 may be a promising biomarker for the detection and prognosis evaluation of BC.

In the war against solid tumors arsenic trioxide needs partners

In the past decade, the therapeutic potential of arsenic trioxide (ATO) in the treatment of acute promyelocytic leukemia (APL) was recognized. This encouraged other investigators to test the efficacy of ATO in the management of other hematological and solid tumor malignancies. Notably, as a single agent, arsenic trioxide did not benefit patients diagnosed with solid tumors. However, when it was combined with other agents, treatment benefit emerged. In this article, we have summarized the outcome of clinical trials that used arsenic trioxide as a single agent as well as in combination settings in patients diagnosed with solid tumors. We have also reviewed possible additional mechanisms by which ATO may be useful as a chemosensitizer in combination therapy. We hope that our review will encourage clinical investigators to rationally combine ATO with additional chemotherapeutic agents in treating patients diagnosed with solid tumors.

Regulation of growth of human bladder cancer by miR-192

The regulation of microRNA-192 (miR-192) is impaired in many cancers. Here, we investigated the role of miR-192 in the proliferation, cell cycle progression, and apoptosis of bladder cancer cells. Human bladder cancer cells were transfected with human miR-192 precursor or non-specific control miRNA. The effect of miR-192 on cell proliferation was assessed by a MTT assay. The effects of miR-192 on cell cycle regulation and apoptosis were evaluated by flow cytometry. Western blot was used to analyze the protein levels of cyclin D1, p21, p27, Bcl-2, Bax, and Mcl-1. We found that overexpression of miR-192 significantly decreased the proliferation of bladder cancer cells by 22 and 54 % at 48 and 72 h, respectively. MiR-192-overexpressing cells exhibited a significant increase in G0/G1 phase and a significant decrease in S phase compared to the control miRNA-transfected cells. Moreover, overexpression of miR-192 significantly induced apoptotic death in bladder cancer cells, increased the levels of p21, p27, and Bax, and decreased the levels of cyclin D1, Bcl-2, and Mcl-1. Taken together, these data suggest that miR-192 may be a suppressor for bladder cancer cells by cell cycle regulation.

Toxicoepigenomics and cancer: implications for screening

Scientists have long considered genetics to be the key mechanism that alters gene expression because of exposure to the environment and toxic substances (toxicants). Recently, epigenetic mechanisms have emerged as an alternative explanation for alterations in gene expression resulting from such exposure. The fact that certain toxic substances that contribute to tumor development do not induce mutations probably results from underlying epigenetic mechanisms. The field of toxicoepigenomics emerged from the combination of epigenetics and classical toxicology. High-throughput technologies now enable evaluation of altered epigenomic profiling in response to toxins and environmental pollutants. Furthermore, differences in the epigenomic backgrounds of individuals may explain why, although whole populations are exposed to toxicants, only a few people in a population develop cancer. Metals in the environment and toxic substances not only alter DNA methylation patterns and histone modifications but also affect enzymes involved in posttranslational modifications of proteins and epigenetic regulation, and thereby contribute to carcinogenesis. This article describes different toxic substances and environmental pollutants that alter epigenetic profiling and discusses how this information can be used in screening populations at high risk of developing cancer. Research opportunities and challengers in the field also are discussed.

Mannan-conjugated adenovirus enhanced gene therapy effects on murine hepatocellular carcinoma cells in vitro and in vivo

The incidence of advanced hepatocellular carcinoma (HCC) is increasing worldwide, and its prognosis is extremely poor. For some patients for whom surgical treatments are not appropriate, one can only rely on chemotherapy. In the conventional chemotherapy, side effects usually occurred in most cases due to high toxicity levels. Moreover, the development of drug resistance toward chemotherapeutic agents often prevents the successful long-term use of chemotherapy for HCC. Gene therapy represents the exciting biotechnological advance that may revolutionize the conventional fashion of cancer treatment. Overexpression of phosphatase and tensin homologue (PTEN) in cancer cells carrying deletion/mutant type of it can induce the apoptosis of cancer cells and inhibit cell proliferation. In this work, in order to make full use of the high transfectivity of adenovirus, we managed to conjugate the polysaccharide mannan (polymannose) to the surface of the adenovirus chemically under appropriate oxidizing conditions to prepare the mannan-modified adenovirus (Man-Ad5-PTEN). The cytotoxicity and anticancer activity of Man-Ad5-PTEN were assessed in vitro. Reporter gene expression of LacZ transferred by Man-Ad5-LacZ was verified on mannose receptor-deficient NIH/3T3 cells versus mannose receptor-efficient macrophages. Hepatocellular carcinoma cell lines transduced by mannan-modified adenovirus were assayed for cell cycle, apoptosis, invasion, and migration. Further, we detected the antitumor effect on intraperitoneal H22 tumor-bearing mice treated by Man-Ad5-PTEN alone or combined with chemotherapeutic agent of doxorubicin. The results demonstrated that cell growth suppression was not observed in Chang normal hepatocyte cells and the cell killing by Man-Ad5-PTEN is tumor selective. Further, the results showed that the strategy of mannan conjugation could enhance adenovirus-mediated PTEN gene therapy effects on murine hepatocellular carcinoma cells in vitro and in vivo.

Exosomes secreted from GATA-4 overexpressing mesenchymal stem cells serve as a reservoir of anti-apoptotic microRNAs for cardioprotection

BACKGROUND

Exosomes play an important role in intercellular signaling and exert regulatory function by carrying bioactive molecules. This study investigated (1) the cardioprotective capabilities of exosomes derived from mesenchymal stem cells (MSCs) overexpressing GATA-4 (MSC(GATA-4)) and (2) its underlying regulatory mechanisms for expression of target proteins in recipient cells.

METHODS AND RESULTS

Exosomes were isolated and purified from MSC(GATA-4) (Exo(GATA-4)) and control MSCs (Exo(Null)). Cell injury was investigated in primary cultured rat neonatal cardiomyocytes (CM) and in the rat heart. Exosomes contributed to increased CM survival, reduced CM apoptosis, and preserved mitochondrial membrane potential in CM cultured under a hypoxic environment. Direct intramyocardial transplantation of exosomes at the border of an ischemic region following ligation of the left anterior descending coronary artery significantly restored cardiac contractile function and reduced infarct size. Real-time PCR revealed that several anti-apoptotic miRs were highly expressed in Exo(GATA-4). Rapid internalization of Exo(GATA-4) by CM was documented using time-lapse imaging. Subsequent expression of these miRs, particularly miR-19a was higher in CM and in the myocardium treated with Exo(GATA-4) compared to those treated with Exo(Null). The enhanced protective effects observed in CM were diminished by the inhibition of miR-19a. The expression level of PTEN, a predicted target of miR-19a, was reduced in CM treated with Exo(GATA-4), which resulted in the activation of the Akt and ERK signaling pathways.

CONCLUSIONS

Exo(GATA-4) upon transplantation in the damaged tissue mediate protection by releasing multiple miRs responsible for activation of the cell survival signaling pathway.

Increased miR-141 expression is associated with diagnosis and favorable prognosis of patients with bladder cancer

The aims of this study are to analyze the association of microRNA-141 (miR-141) with the clinicopathological parameters of bladder cancer and evaluate the value of miR-141 in predicting the prognosis of bladder cancer. In this study, 114 patients with bladder cancer were enrolled in the study, and tissue specimens were obtained from the tumor zone and from adjacent normal area. miR-141 expression was determined using SYRB Green quantitative real-time polymerase chain reaction assay and was further correlated with patients' clinicopathological parameters and the follow-up data. The results indicated that miR-141 was upregulated in malignant bladder specimens compared with normal ones (P < 0.001). miR-141 expression was significantly associated with tumor stage (P < 0.001), tumor grade (P < 0.001), and muscle invasion status (P < 0.001). Log-rank test showed that the higher miR-141 expression was associated with longer disease-specific survival of the patients with bladder cancer (P < 0.001), which was also proven by univariate and multivariate Cox regression analysis (P < 0.001 and P = 0.039, respectively). Focusing on patients with non-muscle invasive bladder cancer, univariate analysis using log-rank test and Cox regression analysis found that patients with high miR-141 expression experienced longer disease-free survival (P = 0.031 and P = 0.040, respectively) and disease-specific survival (P = 0.028 and P = 0.038, respectively), which was confirmed by multivariate Cox regression analysis (P = 0.036 and P = 0.042, respectively). In conclusion, this study showed that miR-141 may contribute to the progression of bladder cancer and its upregulation may be independently associated with favorable prognosis of bladder cancer, suggesting that miR-141 might serve as a promising biological marker for further risk stratification in the management of bladder cancer.

The antileukemia activity of natural product HQ17(3) is possibly associated with downregulation of miR-17-92 cluster

The compound 10′(Z),13′(E),15′(E)-heptadecatrienylhydroquinone [HQ17(3)] was purified from the sap of the lacquer tree Rhus succedanea. HQ17(3) has cytotoxic effect on cancer cells and can inhibit topoisomerase (topo) IIα activity. We treated various cancer cells with different doses of HQ17(3) and found that leukemia cells were most sensitive to HQ17(3). After analysis of microRNA (miRNA) profiling, we found that treatment with HQ17(3) caused downregulation of miR-17-92 cluster in some leukemia cells. These changes partially restored the normal levels from leukemia-specific miRNA expression signature. Messenger RNAs of tumor suppressor proteins, such as pRB, PTEN, and Dicer, are targets of miR-17-92 cluster. Their protein levels were increased after the treatment. c-Myc is a regulatory protein for miR-17-92 gene. Similar to topo IIα, we found that c-Myc decreased its activity after the HQ17(3) treatment, which may explain the downregulation of miR-17-92 cluster. Combined with 5-fluorouracil, NaAsO₂, or ABT-737, HQ17(3) elicited additive inhibitory effects on leukemia cells. In conclusion, the high sensitivity of leukemia cells to HQ17(3) may be associated with the reduction of topo IIα and c-Myc activities, as well as with the downregulation of the miR-17-92 cluster expression.

Incorporating epigenetic data into the risk assessment process for the toxic metals arsenic, cadmium, chromium, lead, and mercury: strategies and challenges

Exposure to toxic metals poses a serious human health hazard based on ubiquitous environmental presence, the extent of exposure, and the toxicity and disease states associated with exposure. This global health issue warrants accurate and reliable models derived from the risk assessment process to predict disease risk in populations. There has been considerable interest recently in the impact of environmental toxicants such as toxic metals on the epigenome. Epigenetic modifications are alterations to an individual's genome without a change in the DNA sequence, and include, but are not limited to, three commonly studied alterations: DNA methylation, histone modification, and non-coding RNA expression. Given the role of epigenetic alterations in regulating gene and thus protein expression, there is the potential for the integration of toxic metal-induced epigenetic alterations as informative factors in the risk assessment process. In the present review, epigenetic alterations induced by five high priority toxic metals/metalloids are prioritized for analysis and their possible inclusion into the risk assessment process is discussed.

miRNA panels as biomarkers for bladder cancer

Aim: Specific miRNA profiles have been identified for several samples from patients with bladder cancer. The results are not always congruent and partly contradictory. A comparison of published data was performed to select potential markers. Materials & methods: A literature search in PubMed identified 79 articles published prior to June 2013. Reports regarding the detection of miRNAs in urine and blood have rarely been published; to date, nine respectively three articles are available. Results: The comparison of published data proved the utility of miRNAs as diagnostic and prognostic indicators of bladder cancer. In urine samples from bladder cancer patients, seven miRNAs were concordantly expressed with tumor tissues. Conclusion: Standardization is strictly required in pre-analytics and methods of miRNA measurements.

Genotoxic and epigenetic mechanisms in arsenic carcinogenicity

Arsenic is a human carcinogen with weak mutagenic properties that induces tumors through mechanisms not yet completely understood. People worldwide are exposed to arsenic-contaminated drinking water, and epidemiological studies showed a high percentage of lung, bladder, liver, and kidney cancer in these populations. Several mechanisms by which arsenical compounds induce tumorigenesis were proposed including genotoxic damage and chromosomal abnormalities. Over the past decade, a growing body of evidence indicated that epigenetic modifications have a role in arsenic-inducing adverse effects on human health. The main epigenetic mechanisms are DNA methylation in gene promoter regions that regulate gene expression, histone tail modifications that regulate the accessibility of transcriptional machinery to genes, and microRNA activity (noncoding RNA able to modulate mRNA translation). The "double capacity" of arsenic to induce mutations and epimutations could be the main cause of arsenic-induced carcinogenesis. The aim of this review is to better clarify the mechanisms of the initiation and/or the promotion of arsenic-induced carcinogenesis in order to understand the best way to perform an early diagnosis and a prompt prevention that is the key point for protecting arsenic-exposed population. Studies on arsenic-exposed population should be designed in order to examine more comprehensively the presence and consequences of these genetic/epigenetic alterations.

MicroRNAs as potential biomarkers in diseases and toxicology

MiRNAs (microRNAs) are single-stranded non-coding RNAs of approximately 21-23 nucleotides in length whose main function is to inhibit gene expression by interfering with mRNA processes. MicroRNAs suppress gene expression by affecting mRNA (messenger RNAs) stability, targeting the mRNA for degradation, or both. In this review, we have examined how microRNA expression could be altered following exposure to chemicals and how they could represent appropriate tissue and more interestingly circulating biomarkers. Among the key questions before using the microRNA for evaluation of risk toxicity, it remains still to clarify how they could be causally involved in the adverse effects and how stable their changes are.

Toxicogenomics and cancer susceptibility: advances with next-generation sequencing

The aim of this review is to comprehensively summarize the recent achievements in the field of toxicogenomics and cancer research regarding genetic-environmental interactions in carcinogenesis and detection of genetic aberrations in cancer genomes by next-generation sequencing technology. Cancer is primarily a genetic disease in which genetic factors and environmental stimuli interact to cause genetic and epigenetic aberrations in human cells. Mutations in the germline act as either high-penetrance alleles that strongly increase the risk of cancer development, or as low-penetrance alleles that mildly change an individual's susceptibility to cancer. Somatic mutations, resulting from either DNA damage induced by exposure to environmental mutagens or from spontaneous errors in DNA replication or repair are involved in the development or progression of the cancer. Induced or spontaneous changes in the epigenome may also drive carcinogenesis. Advances in next-generation sequencing technology provide us opportunities to accurately, economically, and rapidly identify genetic variants, somatic mutations, gene expression profiles, and epigenetic alterations with single-base resolution. Whole genome sequencing, whole exome sequencing, and RNA sequencing of paired cancer and adjacent normal tissue present a comprehensive picture of the cancer genome. These new findings should benefit public health by providing insights in understanding cancer biology, and in improving cancer diagnosis and therapy.

Molecular functions of small regulatory noncoding RNA

Recently, using large-scale genomic sequencing, a great number of small noncoding RNAs (ncRNA) has been discovered. Short ncRNAs can be classified into three major classes--small interfering RNA (siRNA), microRNA (miRNA), and piwi-interacting RNA (piRNA). These short ncRNAs ranging from 20 to 300 nt in size are now recognized as a new paradigm of gene regulation for controlling many biological processes. In this paper, we review the biogenesis and recent research on the functions of small regulatory non-coding RNAs and aim at understanding their important functions in living organisms.

MRNA and miRNA expression patterns associated to pathways linked to metal mixture health effects

Metals are a threat to human health by increasing disease risk. Experimental data have linked altered miRNA expression with exposure to some metals. MiRNAs comprise a large family of non-coding single-stranded molecules that primarily function to negatively regulate gene expression post-transcriptionally. Although several human populations are exposed to low concentrations of As, Cd and Pb as a mixture, most toxicology research focuses on the individual effects that these metals exert. Thus, this study aims to evaluate global miRNA and mRNA expression changes induced by a metal mixture containing NaAsO2, CdCl2, Pb(C2H3O2)2·3H2O and to predict possible metal-associated disease development under these conditions. Our results show that this metal mixture results in a miRNA expression profile that may be responsible for the mRNA expression changes observed under experimental conditions in which coding proteins are involved in cellular processes, including cell death, growth and proliferation related to the metal-associated inflammatory response and cancer.

The evolving understanding of microRNA in bladder cancer

PURPOSE

Micro ribonucleic acid (miR) expression is altered in urologic malignancies, including bladder cancer (BC). Individual miRs have been shown to modulate multiple signaling pathways that contribute to BC. We reviewed the primary literature on the role of miRs in BC; we provide a general introduction to the processing, regulation, and function of miRs as tumor suppressors and oncogenes and critically evaluate the literature on the implications of altered miR expression in BC.

MATERIALS AND METHODS

We searched the English language literature for original and review articles in PubMed from 1993 to March 2013, using the terms "microRNA" and "bladder cancer," "transitional cell carcinoma," or "urothelial carcinoma." This search yielded 133 unique articles with more than 85% of them published within the last 3 years.

RESULTS

To date, the majority of miR studies in BC use profiling to describe dynamic changes in miR expression across stage and grade. Generalized down-regulation of miRs, including those that target the fibroblast growth factor 3 pathway, such as miR-145, miR-101, miR-100, and miR-99a, has been observed in low-grade, non-muscle invasive BC. In contrast, generalized increased expression of miRs is observed in high-grade, muscle-invasive BC compared with adjacent normal bladder urothelium, including miRs predicted to target p53, such as miR-21 and miR-373. Furthermore, p53 suppresses transcriptional factors that promote mesenchymal differentiation, ZEB-1 and ZEB-2, through regulation of the miR200 family.

CONCLUSIONS

Aberrations in miR expression identified between non-muscle invasive BC and muscle-invasive BC provide insight into the molecular alterations known to distinguish the two parallel pathways of bladder carcinogenesis. The heterogeneity of tumor specimens and research methods limits the reproducibility of changes in miR expression profiles between studies and underscores the importance of in vivo validation in a field that utilizes in silico miR target-prediction models.

Analysis of the transcriptome in molecular epidemiology studies

The human transcriptome is complex, comprising multiple transcript types, mostly in the form of non-coding RNA (ncRNA). The majority of ncRNA is of the long form (lncRNA, ≥ 200 bp), which plays an important role in gene regulation through multiple mechanisms including epigenetics, chromatin modification, control of transcription factor binding, and regulation of alternative splicing. Both mRNA and ncRNA exhibit additional variability in the form of alternative splicing and RNA editing. All aspects of the human transcriptome can potentially be dysregulated by environmental exposures. Next-generation RNA sequencing (RNA-Seq) is the best available methodology to measure this although it has limitations, including experimental bias. The third phase of the MicroArray Quality Control Consortium project (MAQC-III), also called Sequencing Quality Control (SeQC), aims to address these limitations through standardization of experimental and bioinformatic methodologies. A limited number of toxicogenomic studies have been conducted to date using RNA-Seq. This review describes the complexity of the human transcriptome, the application of transcriptomics by RNA-Seq or microarray in molecular epidemiology studies, and limitations of these approaches including the type of cell or tissue analyzed, experimental variation, and confounding. By using good study designs with precise, individual exposure measurements, sufficient power and incorporation of phenotypic anchors, studies in human populations can identify biomarkers of exposure and/or early effect and elucidate mechanisms of action underlying associated diseases, even at low doses. Analysis of datasets at the pathway level can compensate for some of the limitations of RNA-Seq and, as more datasets become available, will increasingly elucidate the exposure-disease continuum.

Serum miR-19a expression correlates with worse prognosis of patients with non-small cell lung cancer

OBJECTIVES

The aim of this study was to investigate the expression levels of miR-19a in non-small cell lung cancer (NSCLC) tissue and serum, and to clarify the relationships of serum miR-19a expression with clinical factors and prognosis of NSCLC patients.

METHODS

Expression levels of miR-19a in 25 paired NSCLC, paracancerous tissues and serum, and sera from 103 controls and 201 NSCLC patients were respectively detected using real-time quantitative PCR.

RESULTS

Compared with the paracancerous tissue, miR-19a was overexpressed in NSCLC tissue (P = 0.006), and there was a strong correlation between expression levels of miR-19 in 25 paired sera and tissues (P = 0.001). Serum miR-19a expression in NSCLC patients was significantly upregulated compared with those in healthy individuals (P = 0.001). High serum miR-19a expression was significantly correlated with TNM stage and lymph node metastasis (P = 0.004 and 0.017, respectively). Survival analysis revealed that overall survival rate of patients with high serum miR-19a expression was significantly worse than those of patients with low serum miR-19a expression (hazard ratio = 1.438, 95% confidence interval 1.007-2.052, P = 0.046).

CONCLUSION

High serum miR-19a expression may be an independent poor prognostic factor for survival in NSCLC patients.

Toxicogenomic approaches for understanding molecular mechanisms of heavy metal mutagenicity and carcinogenicity

Heavy metals that are harmful to humans include arsenic, cadmium, chromium, lead, mercury, and nickel. Some metals or their related compounds may even cause cancer. However, the mechanism underlying heavy metal-induced cancer remains unclear. Increasing data show a link between heavy metal exposure and aberrant changes in both genetic and epigenetic factors via non-targeted multiple toxicogenomic technologies of the transcriptome, proteome, metabolome, and epigenome. These modifications due to heavy metal exposure might provide a better understanding of environmental disorders. Such informative changes following heavy metal exposure might also be useful for screening of biomarker-monitored exposure to environmental pollutants and/or predicting the risk of disease. We summarize advances in high-throughput toxicogenomic-based technologies and studies related to exposure to individual heavy metal and/or mixtures and propose the underlying mechanism of action and toxicant signatures. Integrative multi-level expression analysis of the toxicity of heavy metals via system toxicology-based methodologies combined with statistical and computational tools might clarify the biological pathways involved in carcinogenic processes. Although standard in vitro and in vivo endpoint testing of mutagenicity and carcinogenicity are considered a complementary approach linked to disease, we also suggest that further evaluation of prominent biomarkers reflecting effects, responses, and disease susceptibility might be diagnostic. Furthermore, we discuss challenges in toxicogenomic applications for toxicological studies of metal mixtures and epidemiological research. Taken together, this review presents toxicogenomic data that will be useful for improvement of the knowledge of carcinogenesis and the development of better strategies for health risk assessment.

Pre-analytical variables in miRNA analysis

MicroRNAs (miRNAs) are short non-coding RNAs that are involved in the regulation of cellular processes and have been shown to be differentially expressed in neoplasia and other disease states. This renders miRNAs promising diagnostic and prognostic biomarkers in tissues and body fluids, especially in blood. However, numerous variables can influence the detection of miRNAs in the pre-analytical phase and lead to erroneous results. This is of particular concern when miRNA profiles are used clinically and alter diagnosis and patient treatment. Since miRNAs have been discovered relatively recently, systematic studies examining pre-analytical variables are rare. Therefore, this review comprehensively summarizes the current knowledge of pre-analytical variables that influence miRNA analysis in general, as well as pre-analytical variables that are specific to the detection of circulating miRNAs and tissue miRNAs.

Altered expression profiles of microRNAs upon arsenic exposure of human umbilical vein endothelial cells

Recent studies in our laboratory indicated that arsenite at 20μM significantly induces the apoptosis of HUVECs. In this study we analyzed miRNAs expression profiles upon arsenic exposure of these cells to explore the molecular mechanisms of arsenic-induced vascular toxicity. The expression of miRNAs was examined by Exiqon miRCURY™ LNA microRNA chips. We found that 85 miRNAs were up-regulated and 52 were down-regulated by arsenic treatment as compared to the control group. The expression of altered miRNAs was validated by quantitative reverse-transcription PCR (qRT-PCR). A number of DNA motifs were identified in the promoters of the perturbed miRNAs by promoter analysis using MEME software. Analysis of cellular functions by using DAVID Bioinformatics Resources revealed that phosphoproteins and genes involved in alternative splicing are among the top categories targeted by both up- and down-regulated miRNAs. In conclusion, the results show that the alteration of miRNAs expression might play crucial roles in arsenic-induced vascular injury.

Reference miRNAs for miRNAome analysis of urothelial carcinomas

BACKGROUND/OBJECTIVE

Reverse transcription quantitative real-time PCR (RT-qPCR) is widely used in microRNA (miRNA) expression studies on cancer. To compensate for the analytical variability produced by the multiple steps of the method, relative quantification of the measured miRNAs is required, which is based on normalization to endogenous reference genes. No study has been performed so far on reference miRNAs for normalization of miRNA expression in urothelial carcinoma. The aim of this study was to identify suitable reference miRNAs for miRNA expression studies by RT-qPCR in urothelial carcinoma.

METHODS

Candidate reference miRNAs were selected from 24 urothelial carcinoma and normal bladder tissue samples by miRNA microarrays. The usefulness of these candidate reference miRNAs together with the commonly for normalization purposes used small nuclear RNAs RNU6B, RNU48, and Z30 were thereafter validated by RT-qPCR in 58 tissue samples and analyzed by the algorithms geNorm, NormFinder, and BestKeeper.

PRINCIPAL FINDINGS

Based on the miRNA microarray data, a total of 16 miRNAs were identified as putative reference genes. After validation by RT-qPCR, miR-101, miR-125a-5p, miR-148b, miR-151-5p, miR-181a, miR-181b, miR-29c, miR-324-3p, miR-424, miR-874, RNU6B, RNU48, and Z30 were used for geNorm, NormFinder, and BestKeeper analyses that gave different combinations of recommended reference genes for normalization.

CONCLUSIONS

The present study provided the first systematic analysis for identifying suitable reference miRNAs for miRNA expression studies of urothelial carcinoma by RT-qPCR. Different combinations of reference genes resulted in reliable expression data for both strongly and less strongly altered miRNAs. Notably, RNU6B, which is the most frequently used reference gene for miRNA studies, gave inaccurate normalization. The combination of four (miR-101, miR-125a-5p, miR-148b, and miR-151-5p) or three (miR-148b, miR-181b, and miR-874,) reference miRNAs is recommended for normalization.

Global epigenetic profiling in bladder cancer

Urothelial carcinoma of the bladder is a common disease that arises from two distinct molecular pathways, and is one of the most expensive malignancies to manage. Accurate biomarkers that could detect tumor recurrence or predict future progression would improve the care of patients and reduce the cost of managing the disease. DNA methylation, histone modification and ncRNA expression are important epigenetic mechanisms that regulate the expression of genes. These regulatory mechanisms are altered with bladder cancer, and therefore, represent potential biomarkers and therapeutic targets owing to the reversible nature of their modification. In this article, we will discuss these epigenetic changes in bladder cancer and assess their clinical potential.