Cisplatin-induced epigenetic activation of miR-34a sensitizes bladder cancer cells to chemotherapy

Non-coding RNA transcripts, incredible modulators of cisplatin chemo-resistance in bladder cancer through operating a broad spectrum of cellular processes and signaling mechanism

Bladder cancer (BC) is a highly frequent neoplasm in correlation with significant rate of morbidity, mortality, and cost. The onset of BC is predominantly triggered by environmental and/or occupational exposures to carcinogens, such as tobacco. There are two distinct pathways by which BC can be developed, including non-muscle-invasive papillary tumors (NMIBC) and non-papillary (or solid) muscle-invasive tumors (MIBC). The Cancer Genome Atlas project has further recognized key genetic drivers of MIBC along with its subtypes with particular properties and therapeutic responses; nonetheless, NMIBC is the predominant BC presentation among the suffering individuals. Radical cystoprostatectomy, radiotherapy, and chemotherapy have been verified to be the common therapeutic interventions in metastatic tumors, among which chemotherapeutics are more conventionally utilized. Although multiple chemo drugs have been broadly administered for BC treatment, cisplatin is reportedly the most effective chemo drug against the corresponding malignancy. Notwithstanding, tumor recurrence is usually occurred following the consumption of cisplatin regimens, particularly due to the progression of chemo-resistant trait. In this framework, non-coding RNAs (ncRNAs), as abundant RNA transcripts arise from the human genome, are introduced to serve as crucial contributors to tumor expansion and cisplatin chemo-resistance in bladder neoplasm. In the current review, we first investigated the best-known ncRNAs, i.e. microRNAs (miRNAs), long ncRNAs (lncRNAs), and circular RNAs (circRNAs), correlated with cisplatin chemo-resistance in BC cells and tissues. We noticed that these ncRNAs could mediate the BC-related cisplatin-resistant phenotype through diverse cellular processes and signaling mechanisms, reviewed here. Eventually, diagnostic and prognostic potential of ncRNAs, as well as their therapeutic capabilities were highlighted in regard to BC management.

Potential clinical application of microRNAs in bladder cancer

Bladder cancer (BC) is the tenth most prevalent malignancy globally, presenting significant clinical and societal challenges because of its high incidence, rapid progression, and frequent recurrence. Presently, cystoscopy and urine cytology serve as the established diagnostic methods for BC. However, their efficacy is limited by their invasive nature and low sensitivity. Therefore, the development of highly specific biomarkers and effective non-invasive detection strategies is imperative for achieving a precise and timely diagnosis of BC, as well as for facilitating an optimal tumor treatment and an improved prognosis. microRNAs (miRNAs), short noncoding RNA molecules spanning around 20-25 nucleotides, are implicated in the regulation of diverse carcinogenic pathways. Substantially altered miRNAs form robust functional regulatory networks that exert a notable influence on the tumorigenesis and progression of BC. Investigations into aberrant miRNAs derived from blood, urine, or extracellular vesicles indicate their potential roles as diagnostic biomarkers and prognostic indicators in BC, enabling miRNAs to monitor the progression and predict the recurrence of the disease. Simultaneously, the investigation centered on miRNA as a potential therapeutic agent presents a novel approach for the treatment of BC. This review comprehensively analyzes biological roles of miRNAs in tumorigenesis and progression, and systematically summarizes their potential as diagnostic and prognostic biomarkers, as well as therapeutic targets for BC. Additionally, we evaluate the progress made in laboratory techniques within this field and discuss the prospects.

Epigenetic Regulation in Urothelial Carcinoma

Urothelial carcinoma (UC) is a common malignancy that remains a clinical challenge: Non-muscle-invasive urothelial carcinoma (NMIUC) has a high rate of recurrence and risk of progression, while muscle-invasive urothelial carcinoma (MIUC) has a high mortality. Although some new treatments, such as immunotherapies, have shown potential effects on some patients, most cases of advanced UC remain incurable. While treatments based on epigenetic mechanisms, whether combined with traditional platinum-based chemotherapy or emerging immunotherapy, show therapeutic advantages. With the advancement of sequencing and bioinformatics, the study of epigenomics, containing DNA methylation, histone modifications, chromatin remodeling, and non-coding RNA, is increasingly linked with the occurrence and progression of UC. Since the epigenetics of UC is a constantly developing field of medicine, this review aims to summarize the latest research on epigenetic regulation of UC, generalize the mechanism of epigenetics in UC, and reveal the potential epigenetic therapies in the clinical setting, in order to provide some new clues on the discovery of new drugs based on the epigenetics.

Regulation of cisplatin resistance in bladder cancer by epigenetic mechanisms

Bladder cancer is one of the most common malignancies in the world. Cisplatin is one of the most potent and widely used anticancer drugs and has been employed in several malignancies. Cisplatin-based combination chemotherapies have become important adjuvant therapies for bladder cancer patients. Cisplatin-based treatment often results in the development of chemoresistance, leading to therapeutic failure and limiting its application and effectiveness in bladder cancer. To develop improved and more effective cancer therapy, research has been conducted to elucidate the underlying mechanism of cisplatin resistance. Epigenetic modifications have been demonstrated involved in drug resistance to chemotherapy, and epigenetic biomarkers, such as urine tumor DNA methylation assay, have been applied in patients screening or monitoring. Here, we provide a systematic description of epigenetic mechanisms, including DNA methylation, noncoding RNA regulation, m6A modification and posttranslational modifications, related to cisplatin resistance in bladder cancer.

Non-coding RNA and autophagy: Finding novel ways to improve the diagnostic management of bladder cancer

Major fraction of the human genome is transcribed in to the RNA but is not translated in to any specific functional protein. These transcribed but not translated RNA molecules are called as non-coding RNA (ncRNA). There are thousands of different non-coding RNAs present inside the cells, each regulating different cellular pathway/pathways. Over the last few decades non-coding RNAs have been found to be involved in various diseases including cancer. Non-coding RNAs are reported to function both as tumor enhancer and/or tumor suppressor in almost each type of cancer. Urothelial carcinoma of the urinary bladder is the second most common urogenital malignancy in the world. Over the last few decades, non-coding RNAs were demonstrated to be linked with bladder cancer progression by modulating different signalling pathways and cellular processes such as autophagy, metastasis, drug resistance and tumor proliferation. Due to the heterogeneity of bladder cancer cells more in-depth molecular characterization is needed to identify new diagnostic and treatment options. This review emphasizes the current findings on non-coding RNAs and their relationship with various oncological processes such as autophagy, and their applicability to the pathophysiology of bladder cancer. This may offer an understanding of evolving non-coding RNA-targeted diagnostic tools and new therapeutic approaches for bladder cancer management in the future.

The Roles of miRNAs in Predicting Bladder Cancer Recurrence and Resistance to Treatment

Bladder cancer (BCa) is associated with significant morbidity, with development linked to environmental, lifestyle, and genetic causes. Recurrence presents a significant issue and is managed in the clinical setting with intravesical chemotherapy or immunotherapy. In order to address challenges such as a limited supply of BCG and identifying cases likely to recur, it would be advantageous to use molecular biomarkers to determine likelihood of recurrence and treatment response. Here, we review microRNAs (miRNAs) that have shown promise as predictors of BCa recurrence. MiRNAs are also discussed in the context of predicting resistance or susceptibility to BCa treatment.

Current advances in the application of nanomedicine in bladder cancer

Bladder cancer is the most common malignant tumor of the urinary system, however there are several shortcomings in current diagnostic and therapeutic measures. In terms of diagnosis, the diagnostic tools currently available are not sufficiently sensitive and specific, and imaging is poor, leading to misdiagnosis and missed diagnoses, which can delay treatment. In terms of treatment, current treatment options include surgery, chemotherapy, immunotherapy, gene therapy, and other emerging treatments, as well as combination therapies. However, the main reasons for poor efficacy and side effects during treatment are the lack of specificity and targeting, improper dose control of drugs and photosensitizers, damage to normal cells while attacking cancer cells, and difficulty in delivering siRNA to cancer cells. Nanomedicine is an emerging approach. Among the many nanotechnologies applied in the medical field, nanocarrier-assisted drug delivery systems have attracted extensive research interest due to their great translational value. Well-designed nanoparticles can deliver agents or drugs to specific cell types within target organs through active targeting or passive targeting (enhanced permeability and retention), which allows for imaging, diagnosis, as well as treatment of cancer. This paper reviews advances in the application of various nanocarriers and their advantages and drawbacks, with a focus on their use in the diagnosis and treatment of bladder cancer.

Multicomponent siRNA/miRNA-loaded modified mesoporous silica nanoparticles targeted bladder cancer for a highly effective combination therapy

Bladder cancer is one of the concerning urological malignant diseases in the world, which has a clinical need for effective targeted therapy. The development of nanotechnology-based gene delivery to bladder tumor sites is an effective strategy for targeted cancer therapy with low/no toxicity. With this view, in the present work, the mesoporous silica nanoparticles (MSNs) modified with c(RGDfK)-PLGA-PEG [c(RGDfK)-MSN NPs] were constructed for co-delivery of miR-34a and siPD-L1 within bladder cancer cells and tissues. Our findings showed that miR-34a is downregulated while PD-L1 is up-regulated in cell lines and animal studies. This nano-carrier is biocompatible in the serum environment and effectively protects miR-34a and siPD-L1 against serum degradation. However, we showed that c(RGDfK)-MSN NPs could simultaneously downregulate PD-L1 expression and up-regulate miR-34a in the T24 cells and T24 mice model and enhance anti-tumor effects both in vivo and in vitro. In conclusion, these findings presented new suggestions for improving targeted therapeutic strategies with specified molecular objectives for bladder cancer treatment.

Splicing deregulation, microRNA and Notch aberrations: fighting the three-headed dog to overcome drug resistance in malignant mesothelioma

INTRODUCTION

Malignant mesothelioma (MMe) is an aggressive rare cancer of the mesothelium, associated with asbestos exposure. MMe is currently an incurable disease at all stages mainly due to resistance to treatments. It is therefore necessary to elucidate key mechanisms underlying chemoresistance, in an effort to exploit them as novel therapeutic targets.

AREAS COVERED

Chemoresistance is frequently elicited by microRNA (miRNA) alterations and splicing deregulations. Indeed, several miRNAs, such as miR-29c, have been shown to exert oncogenic or oncosuppressive activity. Alterations in the splicing machinery might also be involved in chemoresistance. Moreover, the Notch signaling pathway, often deregulated in MMe, plays a key role in cancer stem cells formation and self-renewal, leading to drug resistance and relapses.

EXPERT OPINION

The prognosis of MMe in patients varies among different tumors and patient characteristics, and novel biomarkers and therapies are warranted. This work aims at giving an overview of MMe, with a special focus on state-of-the-art treatments and new therapeutic strategies against vulnerabilities emerging from studies on epigenetics factors. Besides, this review is also the first to discuss the interplay between miRNAs and alternative splicing as well as the role of Notch as new promising frontiers to overcome drug resistance in MMe.

Clinical Potential of Fruit in Bladder Cancer Prevention and Treatment

Bladder cancer (BC) is the most common tumor of the urinary system in the world. Moreover, despite using anticancer therapies, BC is also characterized by a high recurrence risk. Among numerous risk factors, cigarette smoking, occupational exposure to certain aromatic compounds, and genetic factors contribute most strongly to BC development. However, the epidemiological data to date suggests that diet quality may influence some carcinogenic factors of BC and, therefore, might have a preventative effect. Adequate consumption of selected fruits with scientifically proven properties, including pomegranates and cranberries, can significantly reduce the risk of developing BC, even in those at risk. Therefore, in this article, we aim to elucidate, using available literature, the role of fruits, including pomegranates, cranberries, citrus fruits, cactus pears, and apples, in BC prevention and treatment. Previous data indicate the role of compounds in the above-mentioned fruits in the modulation of the signaling pathways, including cell proliferation, cell growth, cell survival, and cell death.

The crosstalk between reactive oxygen species and noncoding RNAs: from cancer code to drug role

Oxidative stress (OS), characterized by the excessive accumulation of reactive oxygen species (ROS), is an emerging hallmark of cancer. Tumorigenesis and development driven by ROS require an aberrant redox homeostasis, that activates onco-signaling and avoids ROS-induced programmed death by orchestrating antioxidant systems. These processes are revealed to closely associate with noncoding RNAs (ncRNAs). On the basis of the available evidence, ncRNAs have been widely identified as multifarious modulators with the involvement of several key redox sensing pathways, such as NF-κB and Nrf2 signaling, therefore potentially becoming effective targets for cancer therapy. Furthermore, the vast majority of ncRNAs with property of easy detected in fluid samples (e.g., blood and urine) facilitate clinicians to monitor redox homeostasis, indicating a novel method for cancer diagnosis. Herein, focusing on carcinoma initiation, metastasis and chemoradiotherapy resistance, we aimed to discuss the ncRNAs-ROS network involved in cancer progression, and the potential clinical application as biomarkers and therapeutic targets.

The Emerging Roles and Therapeutic Implications of Epigenetic Modifications in Ovarian Cancer

Ovarian cancer (OC) is one of the most lethal gynecologic malignancies globally. In spite of positive responses to initial therapy, the overall survival rates of OC patients remain poor due to the development of drug resistance and consequent cancer recurrence. Indeed, intensive studies have been conducted to unravel the molecular mechanisms underlying OC therapeutic resistance. Besides, emerging evidence suggests a crucial role for epigenetic modifications, namely, DNA methylation, histone modifications, and non-coding RNA regulation, in the drug resistance of OC. These epigenetic modifications contribute to chemoresistance through various mechanisms, namely, upregulating the expression of multidrug resistance proteins (MRPs), remodeling of the tumor microenvironment, and deregulated immune response. Therefore, an in-depth understanding of the role of epigenetic mechanisms in clinical therapeutic resistance may improve the outcome of OC patients. In this review, we will discuss the epigenetic regulation of OC drug resistance and propose the potential clinical implications of epigenetic therapies to prevent or reverse OC drug resistance, which may inspire novel treatment options by targeting resistance mechanisms for drug-resistant OC patients.

Metformin Increases Sensitivity of Melanoma Cells to Cisplatin by Blocking Exosomal-Mediated miR-34a Secretion

Melanoma, also known as malignant melanoma, is a type of cancer derived from the pigment-containing cells known as melanocytes. Cisplatin (CDDP) is widely used in the treatment of different types of tumors with high response rates, but it generally has low efficiency in melanoma. This study aimed to investigate whether metformin could sensitize the melanoma cell line A375 to cisplatin. Our results for the first time indicated that CDDP increased the miR-34a secretion by exosomes in melanoma A375 cells, which was, at least partially, related to the cisplatin resistance of melanoma cells. Moreover, metformin significantly sensitized A375 cells to cisplatin. Mechanistically, metformin significantly blocked the exosome-mediated miR-34a secretion induced by cisplatin. Our study not only reveals a novel mechanism that exosomal secretion of miR-34a is involved in the cisplatin resistance of melanoma cells but also provides a promising therapeutic strategy by synergistic addition of metformin.

Interplay between DNA Methyltransferase 1 and microRNAs During Tumorigenesis

Cancer is a genetic disease resulting from genomic changes; however, epigenetic alterations act synergistically with these changes during tumorigenesis and cancer progression. Epigenetic variations are gaining more attention as an important regulator in tumor progression, metastasis and therapy resistance. Aberrant DNA methylation at CpG islands is a central event in epigeneticmediated gene silencing of various tumor suppressor genes. DNA methyltransferase 1 (DNMT1) predominately methylates at CpG islands on hemimethylated DNA substrates in proliferation of cells. DNMT1 has been shown to be overexpressed in various cancer types and exhibits tumor-promoting potential. The major drawbacks to DNMT1-targeted cancer therapy are the adverse effects arising from nucleoside and non-nucleoside based DNMT1 inhibitors. This paper focuses on the regulation of DNMT1 by various microRNAs (miRNAs), which may be assigned as future DNMT1 modulators, and highlights how DNMT1 regulates various miRNAs involved in tumor suppression. Importantly, the role of reciprocal inhibition between DNMT1 and certain miRNAs in tumorigenic potential is approached in this review. Hence, this review seeks to project an efficient and strategic approach using certain miRNAs in conjunction with conventional DNMT1 inhibitors as a novel cancer therapy. It has also been pinpointed to select miRNA candidates associated with DNMT1 regulation that may not only serve as potential biomarkers for cancer diagnosis and prognosis, but may also predict the existence of aberrant methylation activity in cancer cells.

Emerging strategies for sensitization of therapy resistant tumors toward cancer therapeutics by targeting the Bcl-2 family, TGF-β, Wnt/β-Catenin, RASSF and miRNA regulated signaling pathways

Conventional chemotherapy relies on the cytotoxicity of chemo-drugs to inflict destructive effects on tumor cells. However, as most tumor cells develop resistance to chemo-drugs, small doses of chemo-drugs are unlikely to provide significant clinical benefits in cancer treatment while high doses of chemo-drugs have been shown to impact normal human cells negatively due to the non-specific nature and cytotoxicity associated with chemo-drugs. To overcome this challenge, sensitizations of tumor cells with bioactive molecules that specifically target the pro-survival and pro-apoptosis signaling pathways of the tumor cells are likely to increase the therapeutic impacts and improve the clinical outcomes by reducing the dependency and adverse effects associated with using high doses of chemo-drugs in cancer treatment. This review focuses on emerging strategies to enhance the sensitization of tumor cells toward cancer therapies based on our understanding of tumor cell biology and underlying signaling pathways.

Comprehensive Analysis of Correlations in the Expression of miRNA Genes and Immune Checkpoint Genes in Bladder Cancer Cells

Personalised medicine is the future and hope for many patients, including those with cancers. Early detection, as well as rapid, well-selected treatment, are key factors leading to a good prognosis. MicroRNA mediated gene regulation is a promising area of development for new diagnostic and therapeutic methods, crucial for better prospects for patients. Bladder cancer is a frequent neoplasm, with high lethality and lacking modern, advanced therapeutic modalities, such as immunotherapy. MicroRNAs are involved in bladder cancer pathogenesis, proliferation, control and response to treatment, which we summarise in this perspective in response to lack of recent review publications in this field. We further performed a correlation-based analysis of microRNA and gene expression data in bladder cancer (BLCA) TCGA dataset. We identified 27 microRNAs hits with opposite expression profiles to genes involved in immune response in bladder cancer, and 24 microRNAs hits with similar expression profiles. We discuss previous studies linking the functions of these microRNAs to bladder cancer and assess if they are good candidates for personalised medicine therapeutics and diagnostics. The discussed functions include regulation of gene expression, interplay with transcription factors, response to treatment, apoptosis, cell proliferation and angiogenesis, initiation and development of cancer, genome instability and tumour-associated inflammatory reaction.

MicroRNA-34a: the bad guy in age-related vascular diseases

The age-related vasculature alteration is the prominent risk factor for vascular diseases (VD), namely, atherosclerosis, abdominal aortic aneurysm, vascular calcification (VC) and pulmonary arterial hypertension (PAH). The chronic sterile low-grade inflammation state, alias inflammaging, characterizes elderly people and participates in VD development. MicroRNA34-a (miR-34a) is emerging as an important mediator of inflammaging and VD. miR-34a increases with aging in vessels and induces senescence and the acquisition of the senescence-associated secretory phenotype (SASP) in vascular smooth muscle (VSMCs) and endothelial (ECs) cells. Similarly, other VD risk factors, including dyslipidemia, hyperglycemia and hypertension, modify miR-34a expression to promote vascular senescence and inflammation. miR-34a upregulation causes endothelial dysfunction by affecting ECs nitric oxide bioavailability, adhesion molecules expression and inflammatory cells recruitment. miR-34a-induced senescence facilitates VSMCs osteoblastic switch and VC development in hyperphosphatemia conditions. Conversely, atherogenic and hypoxic stimuli downregulate miR-34a levels and promote VSMCs proliferation and migration during atherosclerosis and PAH. MiR34a genetic ablation or miR-34a inhibition by anti-miR-34a molecules in different experimental models of VD reduce vascular inflammation, senescence and apoptosis through sirtuin 1 Notch1, and B-cell lymphoma 2 modulation. Notably, pleiotropic drugs, like statins, liraglutide and metformin, affect miR-34a expression. Finally, human studies report that miR-34a levels associate to atherosclerosis and diabetes and correlate with inflammatory factors during aging. Herein, we comprehensively review the current knowledge about miR-34a-dependent molecular and cellular mechanisms activated by VD risk factors and highlight the diagnostic and therapeutic potential of modulating its expression in order to reduce inflammaging and VD burn and extend healthy lifespan.

Non coding RNAs as the critical factors in chemo resistance of bladder tumor cells

BACKGROUND

Bladder cancer (BCa) is the ninth frequent and 13th leading cause of cancer related deaths in the world which is mainly observed among men. There is a declining mortality rates in developed countries. Although, the majority of BCa patients present Non-Muscle-Invasive Bladder Cancer (NMIBC) tumors, only 30% of patients suffer from muscle invasion and distant metastases. Radical cystoprostatectomy, radiation, and chemotherapy have proven to be efficient in metastatic tumors. However, tumor relapse is observed in a noticeable ratio of patients following the chemotherapeutic treatment. Non-coding RNAs (ncRNAs) are important factors during tumor progression and chemo resistance which can be used as diagnostic and prognostic biomarkers of BCa.

MAIN BODY

In present review we summarized all of the lncRNAs and miRNAs associated with chemotherapeutic resistance in bladder tumor cells.

CONCLUSIONS

This review paves the way of introducing a prognostic panel of ncRNAs for the BCa patients which can be useful to select a proper drug based on the lncRNA profiles of patients to reduce the cytotoxic effects of chemotherapy in such patients.

Prognostic Stratification of Bladder Cancer Patients with a MicroRNA-based Approach

Robust non-invasive tests for prognostic stratification of bladder cancer (BCa) patients are in high demand. Following a comprehensive analysis of studies on BCa, we selected a panel of 29 microRNAs (miRNAs) and analyzed their levels in urine and plasma samples in a prospective cohort of 63 BCa patients (32 at high risk of recurrence and 31 low-risk cases) and 37 healthy controls using RT-qPCR. To design an assay suitable for large-scale testing, we applied a hierarchical pipeline to select the miRNAs that were not affected by confounding factors such as haematuria and urine specific gravity, and exceeded stringent cut-off criteria (fold change >2.5 and p-value < 0.005). Using a two-step decision tree based on the urine levels of miR-34a-5p, miR-200a-3p and miR-193a-5p, normalized against miR-125b-5p, patients could be classified as high- or low-risk with a sensitivity of 0.844, specificity of 0.806 and accuracy of 0.825. Furthermore, univariate Cox proportional hazards regression analyses indicated that increased urine levels of miR-29a-3p, miR-34a-5p, miR-193a-5p, miR-200c-3p, miR-205-5p and miR-532-5p were associated with a shorter event-free survival (hazard ratios > 3.1, p-value < 0.05). Taken together, our findings suggest that measuring the urine levels of these miRNAs could provide a novel cost-effective, noninvasive test for risk assessment of BCa patients.

The role of miR-34 in cancer drug resistance

Resistance to conventional chemotherapy remains a major cause of cancer relapse and cancer-related deaths. Therefore, there is an urgent need to overcome resistance barriers. To improve cancer treatment approaches, it is critical to elucidate the basic mechanisms underlying drug resistance. Increasingly, the mechanisms involving micro-RNAs (miRNAs) are studied because miRNAs are also considered practical therapeutic options due to high degrees of specificity, efficacy, and accuracy, as well as their ability to target multiple genes at the same time. Years of research have firmly established miR-34 as a key tumor suppressor miRNA whose target genes are involved in drug resistance mechanisms. Indeed, numerous articles show that low levels of circulating miR-34 or tumor-specific miR-34 expression are associated with poor response to chemotherapy. In addition, elevation of inherently low miR-34 levels in resistant cancer cells effectively restores sensitivity to chemotherapeutic agents. Here, we review this literature, also highlighting some contradictory observations. In addition, we discuss the potential utility of miR-34 expression as a predictive biomarker for chemotherapeutic drug response. Although caution needs to be exercised, miR-34 is emerging as a biomarker that could improve cancer precision medicine.

miRNAs: A Promising Target in the Chemoresistance of Bladder Cancer

Chemotherapy is an important cancer treatment method. Tumor chemotherapy resistance is one of the main factors leading to tumor progression. Like other malignancies, bladder cancer, especially muscle-invasive bladder cancer, is prone to chemotherapy resistance. Additionally, only approximately 50% of muscle-invasive bladder cancer responds to cisplatin-based chemotherapy. miRNAs are a class of small, endogenous, noncoding RNAs that regulate gene expression at the posttranscriptional level, which results in the inhibition of translation or the degradation of mRNA. In the study of miRNAs and cancer, including gastric cancer, prostate cancer, liver cancer, and colorectal cancer, it has been found that miRNAs can regulate the expression of genes related to tumor resistance, thereby promoting the progression of tumors. In bladder cancer, miRNAs are also closely related to chemotherapy resistance, suggesting that miRNAs can be a new therapeutic target for the chemotherapy resistance of bladder cancer. Therefore, understanding the mechanisms of miRNAs in the chemotherapy resistance of bladder cancer is an important foundation for restoring the chemotherapy sensitivity of bladder cancer and improving the efficacy of chemotherapy and patient survival. In this article, we review the role of miRNAs in the development of chemotherapy-resistant bladder cancer and the various resistance mechanisms that involve apoptosis, the cell cycle, epithelial-mesenchymal transition (EMT), and cancer stem cells (CSCs).

c-Myc Acts as a Competing Endogenous RNA to Sponge miR-34a, in the Upregulation of CD44, in Urothelial Carcinoma

MicroRNAs (miRNAs) have been shown to play a crucial role in the progression of human cancers, including urothelial carcinoma (UC), the sixth-most common cancer in the world. Among them, miR-34a has been implicated in the regulation of cancer stem cells (CSCs); however, its role in UC has yet to be fully elucidated. In this study, bioinformatics and experimental analysis confirmed that miR-34a targets CD44 (a CSC surface marker) and c-Myc (a well-known cell cycle regulator) in UC. We found that, surprisingly, most UC cell lines and patient samples did express miR-34a, although epigenetic silencing by promoter hypermethylation of miR-34a expression was observed only in UMUC3 cells, and a subset of patient samples. Importantly, overexpression of c-Myc, a frequently amplified oncogene in UC, was shown to upregulate CD44 expression through a competing endogenous RNA (ceRNA) mechanism, such that overexpression of the c-Myc 3'UTR upregulated CD44, and vice versa. Importantly, we observed a positive correlation between the expression of c-Myc and CD44 in clinical samples obtained from UC patients. Moreover, overexpression of a dominant-negative p53 mutant downregulated miR-34a, but upregulated c-Myc and CD44, in UC cell lines. Functionally, the ectopic expression of miR-34a was shown to significantly suppress CD44 expression, and subsequently, suppression of cell growth and invasion capability, while also reducing chemoresistance. In conclusion, it appears that aberrant promoter methylation, and c-Myc-mediated ceRNA mechanisms, may attenuate the function of miR-34a, in UC. The tumor suppressive role of miR-34a in controlling CSC phenotypes in UC deserves further investigation.

Obatoclax, a BH3 Mimetic, Enhances Cisplatin-Induced Apoptosis and Decreases the Clonogenicity of Muscle Invasive Bladder Cancer Cells via Mechanisms That Involve the Inhibition of Pro-Survival Molecules as Well as Cell Cycle Regulators

Several studies by our group and others have determined that expression levels of Bcl-2 and/or Bcl-xL, pro-survival molecules which are associated with chemoresistance, are elevated in patients with muscle invasive bladder cancer (MI-BC). The goal of this study was to determine whether combining Obatoclax, a BH3 mimetic which inhibits pro-survival Bcl-2 family members, can improve responses to cisplatin chemotherapy, the standard of care treatment for MI-BC. Three MI-BC cell lines (T24, TCCSuP, 5637) were treated with Obatoclax alone or in combination with cisplatin and/or pre-miR-34a, a molecule which we have previously shown to inhibit MI-BC cell proliferation via decreasing Cdk6 expression. Proliferation, clonogenic, and apoptosis assays confirmed that Obatoclax can decrease cell proliferation and promote apoptosis in a dose-dependent manner. Combination treatment experiments identified Obatoclax + cisplatin as the most effective treatment. Immunoprecipitation and Western analyses indicate that, in addition to being able to inhibit Bcl-2 and Bcl-xL, Obatoclax can also decrease cyclin D1 and Cdk4/6 expression levels. This has not previously been reported. The combined data demonstrate that Obatoclax can inhibit cell proliferation, promote apoptosis, and significantly enhance the effectiveness of cisplatin in MI-BC cells via mechanisms that likely involve the inhibition of both pro-survival molecules and cell cycle regulators.

lncRNA TUG1 Promotes Cisplatin Resistance by Regulating CCND2 via Epigenetically Silencing miR-194-5p in Bladder Cancer

Taurine-upregulated gene 1 (TUG1) has been involved in tumorigenesis of several human cancers, but its precise biological role in bladder cancer remains largely elusive. In this study, we found that TUG1 was upregulated in bladder cancer and the expression of TUG1 was positively and negatively correlated with CCND2 and miR-194-5p, respectively. MiR-194-5p expression was frequently decreased through promoter hypermethylation, while it was epigenetically increased following cisplatin and 5-aza-2′-deoxycytidine (5-Aza-DC) treatment. Furthermore, knockdown of TUG1 attenuated the expression of epigenetic regulator Enhancer of zeste homolog 2 (EZH2), and it alleviated the promoter hypermethylation of miR-194-5p and induced its expression. Increased miR-194-5p expression or decreased TUG1 expression significantly sensitized bladder cancer cells to cisplatin, inhibited the proliferation, and induced apoptosis. Besides, CCND2 was a direct target of miR-194-5p, while miR-194-5p was regulated by TUG1. CCND2 could partially restore the tumor-suppressive effects on cell proliferation and cisplatin resistance following TUG1 silencing. Additionally, TUG1 expression was correlated with clinical stage, lymphatic metastasis, and patient prognosis. In conclusion, TUG1 promotes bladder cancer cell growth and chemoresistance by regulating CCND2 via EZH2-associated silencing of miR-194-5p. Our study may be conducive to elucidating the molecular mechanism of and providing novel therapeutic target and biomarker for bladder cancer.

Deduction of Novel Genes Potentially Involved in Upper Tract Urothelial Carcinoma Using Next-Generation Sequencing and Bioinformatics Approaches

Upper tract urothelial carcinoma (UTUC) is a relatively uncommon cancer worldwide, however it accounts for approximately 30% of urothelial cancer in the Taiwanese population. The aim of the current study is to identify differential molecular signatures and novel miRNA regulations in UTUC, using next-generation sequencing and bioinformatics approaches. Two pairs of UTUC tumor and non-tumor tissues were collected during surgical resection, and RNAs extracted for deep sequencing. There were 317 differentially expressed genes identified in UTUC tissues, and the systematic bioinformatics analyses indicated dysregulated genes were enriched in biological processes related to aberration in cell cycle and matrisome-related genes. Additionally, 15 candidate genes with potential miRNA-mRNA interactions were identified. Using the clinical outcome prediction database, low expression of SLIT3 was found to be a prognostic predictor of poor survival in urothelial cancer, and a novel miRNA, miR-34a-5p, was a potential regulator of SLIT3, which may infer the potential role of miR-34a-5p-SLIT3 regulation in the altered tumor microenvironment in UTUC. Our findings suggested novel miRNA target with SLIT3 regulation exerts potential prognostic value in UTUC, and future investigation is necessary to explore the role of SLIT3 in the tumor development and progression of UTUC.

Relations between approved platinum drugs and non-coding RNAs in mesothelioma

Malignant mesothelioma diseases feature an increasing risk due to their severe forms and their association with asbestos exposure. Platinum(II) complexes such as cisplatin and carboplatin are clinically approved for the therapy of mesothelioma often in combination with antimetabolites such as pemetrexed or gemcitabine. It was observed that pathogenic properties of mesothelioma cells and the response of mesothelioma tumors towards platinum-based drugs are strongly influenced by non-coding RNAs, in particular, by small microRNAs (miRNAs) and long non-coding RNAs (lncRNAs). These non-coding RNAs controlled drug sensitivity and the development of tumor resistance towards platinum drugs. An overview of the interactions between platinum drugs and non-coding RNAs is given and the influence of non-coding RNAs on platinum drug efficacy in mesothelioma is discussed. Suitable non-coding RNA-modulating agents with potentially beneficial effects on cisplatin treatment of mesothelioma diseases are mentioned. The understanding of mesothelioma diseases concerning the interactions of non-coding RNAs and platinum drugs will optimize existing therapy schemes and pave the way to new treatment options in future.

Epigenetic silencing of miR-200b is associated with cisplatin resistance in bladder cancer

In this study, we identified microRNAs (miRNAs) involved in cisplatin (CDDP) resistance in bladder cancer (BCa). After establishing CDDP-resistant BCa cell lines (T24RC and EJ138RC), TaqMan arrays revealed that members of the miR-200 family (miR-200b, miR-200a and miR-429) were downregulated in T24RC as compared to parental T24 cells. miR-200b was associated with CDDP sensitivity in BCa cells, and its downregulation was associated with CpG island hypermethylation. Pharmacological demethylation using 5-aza-2’-deoxycytidine restored miR-200b expression, and the combination of 5-aza-2’-deoxycytidine + CDDP strongly inhibited T24RC cell proliferation. Microarray analysis revealed that miR-200b + CDDP induced genes involved in CDDP sensitivity or cytotoxicity, including IGFBP3, ICAM1 and TNFSF10, in the resistant cells. Expression and DNA methylation of miR-200b were inversely associated in primary BCa, and low expression/high methylation was associated with poor overall survival. These results suggest downregulation of miR-200b is associated with CDDP resistance in BCa. Epigenetic silencing of miR-200b may be a marker of CDDP resistance and a useful therapeutic target for overcoming CDDP resistance in BCa.

Dysregulation of miRNAs in bladder cancer: altered expression with aberrant biogenesis procedure

Aberrant expression profiles of miRNAs are widely observed in the clinical tissue specimens and urine samples as well as the blood samples of bladder cancer patients. These profiles are closely related to the pathological features of bladder cancer, such as the tumour stage/grade, metastasis, recurrence and chemo-sensitivity. MiRNA biogenesis forms the basis of miRNA expression and function, and its dysregulation has been shown to be essential for variations in miRNA expression profiles as well as tumourigenesis and cancer progression. In this review, we summarize the up-to-date and widely reported miRNAs in bladder cancer that display significantly altered expression. We then compare the miRNA expression profiles among three different sample types (tissue, urine and blood) from patients with bladder cancer. Moreover, for the first time, we outline the dysregulated miRNA biogenesis network in bladder cancer from different levels and analyse its possible relationship with aberrant miRNA expression and the pathological characteristics of the disease.

MicroRNA-31 functions as a tumor suppressor and increases sensitivity to mitomycin-C in urothelial bladder cancer by targeting integrin α5

Urothelial bladder cancer (UBC) is a common genitourinary malignancy. MiR-31, a well-identified miRNA, exhibits diverse properties in different cancers. However, the specific functions and mechanisms of miR-31 in UBC have not been investigated. In this study, tumor samples, especially invasive UBC, showed significantly reduced level of miR-31, as compared with normal urothelium. Prognostic analysis using the EORTC model showed that down-regulation of miR-31 correlated with higher risks of recurrence and progression in noninvasive UBC cases. Remarkably, overexpression of miR-31 mimics in UBC cell lines inhibited cell proliferation, migration and invasion. Integrin α5 (ITGA5), an integrin family member, was subsequently identified as a direct target of miR-31 in UBC cells. When treated with mitomycin-C (MMC), miR-31-expressing UBC cells displayed lower survival and higher apoptotic rates, and deactivated Akt and ERK. These effects arising from miR-31 overexpression were abrogated by ITGA5 restoration. Furthermore, miR-31 markedly inhibited tumor growth and increased the effectiveness of MMC in UBC xenografts. In summary, our data suggest that miR-31 is a prognostic predictor and can serve as a potential therapeutic target of UBC.

MicroRNA-34a suppresses invasion and metastatic in esophageal squamous cell carcinoma by regulating CD44

In human esophageal squamous cell carcinoma (ESCC), miR-34a was downregulated and could inhibit in vitro cell proliferation and migration. However, the underlying mechanism was not clear yet. The expression levels of mRNA and protein were detected by quantitative real-time PCR or western blotting, respectively. MiR-34a was knocked down or overexpressed and transfected into human ESCC cell lines ECA109 and TE-13, respectively. Cell migration and wound healing assays were used to examine the effect on migration and invasion in vitro. Animal models were used to examine the role of miR-34a in metastasis in vivo. Luciferase assay was carried out to validate the potential target of miR-34a. CD44 was upregulated and miR-34a was downregulated in ESCC tissues and cell lines. The linear regression analysis showed that CD44 expression was negatively correlated with the level of miR-34a. Luciferase assay showed that miR-34a interacted with a putative binding site in the CD44 3'UTR. MiR-34a was found to negatively regulate the expression of CD44. In vitro experiment showed that miR-34a overexpression inhibited ESCC cell invasion and migration; whereas miR-34a knockdown showed reversed results. MiR-34a also inhibited esophagus tumor growth and metastasis in vivo; whereas miR-34a knockdown showed reversed results. Finally, we found that CD44 knockdown reversed the effects of miR-34a knockdown on ESCC cell invasion and migration in vitro. MiRNA-34a suppresses invasion and metastatic in ESCC by regulating CD44.

An Oncofetal Glycosaminoglycan Modification Provides Therapeutic Access to Cisplatin-resistant Bladder Cancer

BACKGROUND

Although cisplatin-based neoadjuvant chemotherapy (NAC) improves survival of unselected patients with muscle-invasive bladder cancer (MIBC), only a minority responds to therapy and chemoresistance remains a major challenge in this disease setting.

OBJECTIVE

To investigate the clinical significance of oncofetal chondroitin sulfate (ofCS) glycosaminoglycan chains in cisplatin-resistant MIBC and to evaluate these as targets for second-line therapy.

DESIGN, SETTING, AND PARTICIPANTS

An ofCS-binding recombinant VAR2CSA protein derived from the malaria parasite Plasmodium falciparum (rVAR2) was used as an in situ, in vitro, and in vivo ofCS-targeting reagent in cisplatin-resistant MIBC. The ofCS expression landscape was analyzed in two independent cohorts of matched pre- and post-NAC-treated MIBC patients.

INTERVENTION

An rVAR2 protein armed with cytotoxic hemiasterlin compounds (rVAR2 drug conjugate [VDC] 886) was evaluated as a novel therapeutic strategy in a xenograft model of cisplatin-resistant MIBC.

OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS

Antineoplastic effects of targeting ofCS.

RESULTS AND LIMITATIONS

In situ, ofCS was significantly overexpressed in residual tumors after NAC in two independent patient cohorts (p<0.02). Global gene-expression profiling and biochemical analysis of primary tumors and cell lines revealed syndican-1 and chondroitin sulfate proteoglycan 4 as ofCS-modified proteoglycans in MIBC. In vitro, ofCS was expressed on all MIBC cell lines tested, and VDC886 eliminated these cells in the low-nanomolar IC₅₀ concentration range. In vivo, VDC886 effectively retarded growth of chemoresistant orthotopic bladder cancer xenografts and prolonged survival (p=0.005). The use of cisplatin only for the generation of chemoresistant xenografts are limitations of our animal model design.

CONCLUSIONS

Targeting ofCS provides a promising second-line treatment strategy in cisplatin-resistant MIBC.

PATIENT SUMMARY

Cisplatin-resistant bladder cancer overexpresses particular sugar chains compared with chemotherapy-naïve bladder cancer. Using a recombinant protein from the malaria parasite Plasmodium falciparum, we can target these sugar chains, and our results showed a significant antitumor effect in cisplatin-resistant bladder cancer. This novel treatment paradigm provides therapeutic access to bladder cancers not responding to cisplatin.

Interactions between anticancer active platinum complexes and non-coding RNAs/microRNAs

Platinum(II) complexes such as cisplatin, carboplatin and oxaliplatin are clinically approved for the therapy of various solid tumors. Challenging pathogenic properties of cancer cells and the response of cancers towards platinum-based drugs are strongly influenced by non-coding small RNA molecules, the microRNAs (miRNAs). Both increased platinum activity and formation of tumor resistance towards platinum drugs are controlled by miRNAs. This review gives an overview of the interactions between platinum-based drugs and miRNAs, and their influence on platinum activity in various cancer types is discussed.

Antitumor activity of miR-34a in peritoneal mesothelioma relies on c-MET and AXL inhibition: persistent activation of ERK and AKT signaling as a possible cytoprotective mechanism

Background

The value of microRNAs (miRNAs) as novel targets for cancer therapy is now widely recognized. However, no information is currently available on the expression/functional role of miRNAs in diffuse malignant peritoneal mesothelioma (DMPM), a rapidly lethal disease, poorly responsive to conventional treatments, for which the development of new therapeutic strategies is urgently needed. Here, we evaluated the expression and biological effects of miR-34a—one of the most widely deregulated miRNAs in cancer and for which a lipid-formulated mimic is already clinically available—in a large cohort of DMPM clinical samples and a unique collection of in house-developed preclinical models, with the aim to assess the potential of a miR-34a-based approach for disease treatment.

Methods

miR-34a expression was determined by qRT-PCR in 45 DMPM and 7 normal peritoneum specimens as well as in 5 DMPM cell lines. Following transfection with miR-34a mimic, the effects on DMPM cell phenotype, in terms of proliferative potential, apoptotic rate, invasion ability, and cell cycle distribution, were assessed. In addition, three subcutaneous and orthotopic DMPM xenograft models were used to examine the effect of miR-34a on tumorigenicity. The expression of miRNA targets and the activation status of relevant pathways were investigated by western blot.

Results

miR-34a was found to be down-regulated in DMPM clinical specimens and cell lines compared to normal peritoneal samples. miR-34a reconstitution in DMPM cells significantly inhibited proliferation and tumorigenicity, induced an apoptotic response, and declined invasion ability, mainly through the down-regulation of c-MET and AXL and the interference with the activation of downstream signaling. Interestingly, a persistent activation of ERK1/2 and AKT in miR-34a-reconstituted cells was found to counteract the antiproliferative and proapoptotic effects of miRNA, yet not affecting its anti-invasive activity.

Conclusions

Our preclinical data showing impressive inhibitory effects induced by miR-34a on DMPM cell proliferation, invasion, and growth in immunodeficient mice strongly suggest the potential clinical utility of a miR-34a-replacement therapy for the treatment of such a still incurable disease. On the other hand, we provide the first evidence of a potential cytoprotective/resistance mechanism that may arise towards miRNA-based therapies through the persistent activation of RTK downstream signaling.

Electronic supplementary material

The online version of this article (doi:10.1186/s13045-016-0387-6) contains supplementary material, which is available to authorized users.

Long non-coding RNA NEAT1 contributes to docetaxel resistance of prostate cancer through inducing RET expression by sponging miR-34a

Nuclear paraspeckle assembly transcript 1 (NEAT1) was demonstrated to serve as a carcinogenic long non-coding RNA (lncRNA) in multiple tumors including prostate cancer (PC).

Mir-449a, a potential diagnostic biomarker for WNT group of medulloblastoma

Medulloblastoma (MB) is the most common malignant brain tumor in childhood. The 5 year disease-free survival rate is rather low. There is a consensus that MB can be divided into at least four clinically, transcriptionally, and genetically distinct molecular variants, being designated as wingless (WNT), sonic hedgehog (SHH), Group 3 and Group 4. It poses a great challenge to the design of therapeutic strategy for MB patients. Intensive clinical intervention, including high dose radiotherapy, is commonly used in treatment of high risk MB, most of which are considered to be Group 3 patients. But such intensive therapy should be avoided to protect neurologic function of patients in the lower risk WNT group. In present study, MB subgroup assignment in formalin-fixed paraffin embedded (FFPE) specimens from 45 Chinese patients were performed by Nanostring platform using 22 well-known signature genes. Based on comparative expression profiles of miRNA real-time PCR microarray in MB cells with and without treatment of demethylation reagent, as well as MSP assay, miR-449a was demonstrated to be significantly silenced by aberrant DNA methylation in tumor cells. Real-time PCR showed that expression level of miR-449a in WNT group was significantly different from other subgroups, although it was down-regulated in most of the MB samples. In conclusion, current study demonstrates for the first time the feasibility of using the Nanostring assay for subgrouping of MBs in Chinese patients. In addition, MiR-449a, a candidate tumor suppressor regulated by hypermethylation, is a novel potential diagnostic marker for WNT group of MBs.

Meta-analysis of microRNAs as biomarkers for muscle-invasive bladder cancer

Bladder cancer is the most common cancer of the urinary tract. A quarter of bladder cancer patients presenting with muscle-invasive bladder cancer (MIBC) suffer significant morbidity and succumb to the disease. MicroRNA (miRNA) from tissue, urine or blood samples of MIBC patients have been demonstrated to differ from healthy individuals, and possibly have diagnostic value. The aim of the present meta-analysis was to access the overall diagnostic accuracy comprehensively and quantitatively. Systematic searching in PubMed, Web of Science, Embase and Chinese National Knowledge Infrastructure database was conducted. The pooled sensitivity, specificity, positive and negative likelihood ratios (PLR and NLR) and diagnostic odds ratio (DOR) were calculated via the random effects model to evaluate the overall test performance. Deeks' funnel plot asymmetry test was used to test the publication bias. A total of 10 studies were included in the meta-analysis, with a total of 577 patients and 412 controls. The pooled sensitivity and specificity were 0.78 [95% confidence interval (CI), 0.69–0.86] and 0.77 (95% CI, 0.72–0.81), respectively. The pooled PLR was 2.9 (95% CI, 2.1–3.8), the NLR was 0.31 (95% CI, 0.27–0.35), the DOR was 7 (95% CI, 4–13) and the pooled AUC was 0.80 (95% CI, 0.69–0.87). In conclusion, the current miRNA assays support their use as markers for MIBC diagnosis.

MiR-1 downregulation correlates with poor survival in clear cell renal cell carcinoma where it interferes with cell cycle regulation and metastasis

MicroRNAs (miRNA) that are strongly implicated in carcinogenesis have recently reshaped our understanding of the role of noncoding RNAs. Here, we focused on the function and molecular mechanism of miR-1 and its potential clinical application in clear cell renal cell carcinoma (ccRCC). First, miR-1 was significantly downregulated in 87.8% renal cancer samples compared with corresponding noncancerous tissues (NCT), which was significantly associated with clinical stage, T classification and poor overall survival. Functional study demonstrated that enforced overexpression of miR-1 in renal cancer cells inhibited proliferation and metastasis in vitro and in vivo. Conversely, miR-1 inhibitor silencing miR-1 expression promoted cell proliferation and metastasis in ccRCC. CDK4, CDK6, Caprin1 and Slug were each directly targeted for inhibition by miR-1 and restoring their expression reversed miR-1-mediated inhibition of cell cycle progression and metastasis. Taken together, our findings established a tumor suppressive role for miR-1 in the progression of ccRCC by targeting CDK4, CDK6, Caprin1 and Slug and suggested miR-1 can be served as a novel potential therapeutic target for ccRCC.

miR-206 functions as a novel cell cycle regulator and tumor suppressor in clear-cell renal cell carcinoma

PURPOSE

In this study we tried to systematically investigate the tumor suppressing microRNAs in ccRCC.

MATERIALS AND METHODS

The MTS cell viability and colony formation assay were used to systematically detect the tumor suppressing ability of down-regulated miRNAs in ccRCC. Then miR-206 expression was detected by RT-qPCR and in situ hybridization in ccRCC cell lines and clinical samples. Oligonucleotides were used to overexpress or down-regulate miR-206. MTS cell viability, EdU cell proliferation, colony formation assay, flow cytometry, Xenograft subcutaneously and orthotopic implantations were done to examine tumor suppressing effects of miR-206 in vitro and in vivo. Luciferase assay was performed to verify the precise target of miR-206.

RESULTS

We reviewed and experimentally analyzed the currently available miRNA expression profiles data of ccRCC and identified miR-206 as one of the most critical tumor-suppressing microRNAs in ccRCC. In addition, miR-206 inhibited ccRCC cell proliferation through inducing cell cycle arrest by directly targeting cell cycle related gene CDK4, CDK9 and CCND1.

CONCLUSIONS

All these results suggested that miR-206 functioned as a novel cell cycle regulator and tumor suppressor in ccRCC and could be considered as a potential target for ccRCC therapy.

HIF-1α/MDR1 pathway confers chemoresistance to cisplatin in bladder cancer

Bladder cancer (BCa) is the 9th most common malignant tumor and the 13th leading cause of death due to cancer. The development of surgery and target drugs bring new challenges for the traditional concept for BCa therapy, and chemotherapy is still the final option for many BCa patients, and cisplatin-containing regimen the most effective one. However, the ubiquitous application of cisplatin-containing regimen in BCa results in the cisplatin-resistance, in addition, the cisplatin‑resistant BCa manifests enhanced malignant behavior, the mechanism of which is unclear. In the present study, we used BCa cell lines to to clarify this point. BCa cell lines T24/J82 were pretreated with cisplatin >3 months to construct stable cisplatin-resistant cell lines (tagged T24(Cis-R) and J82(Cis-R)), which manifested as enhanced capacity of proliferation and malignant behavior in vivo and in vitro, accompanied by cisplatin, and even doxorubicin resistance. The following mechanism dissection revealed that prolonged treatment time of T24/J82 cells led to elevated expression of HIF-1α, which targeted the increased expression of MDR1 on the one hand, and contributed to BCa cell proliferation, migration/invasion on the other hand. Finally, IHC staining of human BCa tissue supported our conclusion that the expression of HIF-1α and MDR1 was higher in chemoresistant tissue vs. chemosensitive tissue. Our results provided a new view of HIF-1α in chemotherapy.

MicroRNA-373 promotes migration and invasion in human esophageal squamous cell carcinoma by inhibiting TIMP3 expression

Esophageal squamous cell carcinoma (ESCC) is the predominant pathological type of esophageal carcinoma in Asia. MicroRNAs (miRNAs) are a class of 19-22-nucleotide non-coding RNAs acting on target mRNAs that function as either oncogenes or anti-oncogenes. It has been confirmed that miR-373 expression varies among different tumor types. However, its mechanism is still unclear in ESCC. In our current study, we found that miR-373 expression was upregulated in ESCC tissues compared with matched adjacent normal tissues, as well as in the plasma of ESCC patients compared with that of healthy volunteers. Overexpression of miR-373 in ECA109 cells enhanced proliferation, G1-phase cell proportion, migration, and invasion. On the other hand, suppression of miR-373 in KYSE410 cells decreased proliferation, G1-phase cell proportion, migration, and invasion and also improved cell apoptosis. Moreover, we found that TIMP3, which was reported to suppress invasion and metastasis of ESCC, was a direct target of miR-373. Overexpression of miR-373 in ECA109 caused a reduction of TIMP3 mRNA and protein, whereas suppression of miR-373 in KYSE410 led to an increase of TIMP3 mRNA and protein. Introducing TIMP3 in miR-373 over-expressed cells or knocking down TIMP3 in miR-373 suppressed cells could partially abrogate the effect of miR-373 on migration and invasion. Therefore, these results prove that as an oncogene, miRNA-373 would be an important and reliable biomarker for ESCC diagnosis and treatment by targeting TIMP3.

MicroRNA-203 Is a Prognostic Indicator in Bladder Cancer and Enhances Chemosensitivity to Cisplatin via Apoptosis by Targeting Bcl-w and Survivin

Resistance to cisplatin-based chemotherapy is a major cause of treatment failure in advanced bladder cancer (BC) patients. There is increasing evidence that microRNAs are involved in the development and progression of BC. However, little is known about the function of microRNAs in predicting the effect of adjuvant chemotherapy on BC survival and regulating response to cisplatin. To address this issue, we employed RT-qPCR to evaluate the clinical significance of miR-203 expression in 108 tissues of BC patients receiving cisplatin-based adjuvant chemotherapy, and performed in vitro studies to explore chemotherapeutic sensitivity to cisplatin in miR-203 overexpressing BC cells. We found miR-203 levels were significantly lower in BC progression group than non-progression group (P<0.001). ROC curve analysis illustrated miR-203 could significantly distinguish progressed patients from those without progression (P<0.001), yielding an area under the ROC curve of 0.839 (95% CI, 0.756-0.903). Moreover, low miR-203 expression correlated with shortened progression free survival (PFS) and overall survival (OS) of BC patients, and was an independent prognostic factor. Overexpression of miR-203 in 5637 and T24 BC cells could decrease cell viability, enhance cisplatin cytotoxicity, and promote apoptosis. Western blotting and luciferase reporter assay showed Bcl-w and Survivin were direct downstream targets of miR-203. There was also a significant inverse association between miR-203 and Bcl-w or Survivin expression in BC tissues (r = -0.781, -0.740, both P<0.001). In conclusion, decreased miR-203 predicts progression and poor prognosis for BC patients treated with cisplatin-based chemotherapy while miR-203 overexpression can enhance cisplatin sensitization by promoting apoptosis via directly targeting Bcl-w and Survivin.

miR-34a inhibits proliferation and invasion of bladder cancer cells by targeting orphan nuclear receptor HNF4G

miR-34a is a member of the miR-34 family and acts as a tumor suppressor in bladder cancer. This study explored the regulative role of miR-34a on an orphan nuclear receptor HNF4G, which has a well-confirmed role in bladder tumor growth and invasion. qRT-PCR analysis was applied to measure miR-34a expression in two tumorigenic bladder cancer cell lines 5637 and T24 and one normal human urothelial cell line SV-HUC-1. Luciferase assay was performed to verify the putative binding between miR-34a and HNF4G. The influence of miR-34a-HNF4G axis on cell viability, colony formation, and invasion was assessed with loss- and gain-of-function analysis. This study observed that the miR-34a expressions in 5637 and T24 cells were significantly lower than in SV-HUC-1, while the muscle invasive cell sublines 5637-M and T24-M had even lower miR-34a expression than in the nonmuscle invasive sublines. HNF4G has a 3'-UTR binding site with miR-34a and is a direct downstream target of miR-34a. miR-34a can directly downregulate the expression of HNF4G and thus inhibit tumor cell viability, colony formation, and invasion. Therefore, miR-34a-HNF4G axis is an important pathway modulating cell viability, proliferation, and invasion of bladder cancer cells.

Anti-proliferative effects of polyphenols from pomegranate rind (Punica granatum L.) on EJ bladder cancer cells via regulation of p53/miR-34a axis

miRNAs and their validated miRNA targets appear as novel effectors in biological activities of plant polyphenols; however, limited information is available on miR-34a mediated cytotoxicity of pomegranate rind polyphenols in cancer cell lines. For this purpose, cell viability assay, Realtime quantitative PCR for mRNA quantification, western blot for essential protein expression, p53 silencing by shRNA and miR-34a knockdown were performed in the present study. EJ cell treatment with 100 µg (GAE)/mL PRE for 48 h evoked poor cell viability and caspase-dependent pro-apoptosis appearance. PRE also elevated p53 protein and triggered miR-34a expression. The c-Myc and CD44 were confirmed as direct targets of miR-34a in EJ cell apoptosis induced by PRE. Our results provide sufficient evidence that polyphenols in PRE can be potential molecular clusters to suppress bladder cancer cell EJ proliferation via p53/miR-34a axis.

MicroRNA-34a functions as an anti-metastatic microRNA and suppresses angiogenesis in bladder cancer by directly targeting CD44

BACKGROUND

Metastasis have considered as an important clinical obstacle in the treatment of human cancer including bladder cancer. Post-transcriptional regulation has emerged as robust effectors of metastasis. MiRNAs are involved in cancer development and progression, acting as tumor suppressors or oncogenes. In this study, we focus on it that microRNA-34a functions as an anti-metastatic microRNA and suppress angiogenesis in bladder cancer by directly targeting CD44.

METHODS

The expression of mir-34a was detected by quantitative real-time PCR. Oligonucleotide and lentivirus were used to overexpress miR-34a. Tube formation assay and transwell assay were used to examine the effect on bladder cancer tube formation, migration and invasion in vitro. Animal models were used to examine the effect on metastasis and angiogenesis in vivo. Luciferase assay was carried out to verify the precise target of miR-34a.

RESULTS

We not only proved that mir-34a was significantly downregulated in bladder cancer tissues and cell lines but also that circulating miR-34a levels are reduced in bladder cancer, and their levels were positively relevance. Gain-of-function experiments investigated that increased mir-34a expression suppressed tube formation and reduced cell migration and invasion. In vivo metastasis, assays also demonstrated that overexpression of mir34a markedly inhibited bladder cancer metastasis. CD31, an endothelial cell-specific marker which stained in T24 tumors to evaluate for blood vessel density, the immunohistochemistry results showed that blood vessel quantification reduced dramatically in the T24 tumors over-expressing mir-34a. Combining with our previous studies and bioinformatics analysis, we expected that CD44 gene was a direct target of mir-34a, siRNA-mediated knockdown of CD44 partially phenocopied mir-34a overexpression suggesting that the pro-apoptotic role of mir-34a may be mediated primarily through CD44 regulation, whereas restoring the expression of CD44 attenuated the function of mir-34a in bladder cancer cells. Additionally, we identified that EMT (epithelial-mesenchymal transition) related proteins could be regulated by mir-34a which indicated that mir-34a could partially reserve EMT.

CONCLUSION

Our study defines a major metastasis and angiogenesis suppressive role for mir-34a, a microRNA functions as a tumor suppressor in bladder cancer by directly targeting CD44, which would be helpful as a therapeutic approach to block bladder cancer metastasis.