MicroRNA signature of malignant mesothelioma with potential diagnostic and prognostic implications

Melodic maestros: Unraveling the role of miRNAs in the diagnosis, progression, and drug resistance of malignant pleural mesothelioma

Malignant pleural mesothelioma (MPM) is a highly lethal form of pleural cancer characterized by a scarcity of effective therapeutic interventions, resulting in unfavorable prognoses for afflicted individuals. Besides, many patients experience substantial consequences from being diagnosed in advanced stages. The available diagnostic, prognostic, and therapeutic options for MPM are restricted in scope. MicroRNAs (miRNAs) are a subset of small, noncoding RNA molecules that exert significant regulatory influence over several cellular processes within cell biology. A wide range of miRNAs have atypical expression patterns in cancer, serving specific functions as either tumor suppressors or oncomiRs. This review aims to collate, epitomize, and analyze the latest scholarly investigations on miRNAs that are believed to be implicated in the dysregulation leading to MPM. miRNAs are also discussed concerning their potential clinical usefulness as diagnostic and prognostic biomarkers for MPM. The future holds promising prospects for enhancing diagnostic, prognostic, and therapeutic modalities for MPM, with miRNAs emerging as a potential trigger for such advancements.

High Expression of SMO and GLI1 Genes with Poor Prognosis in Malignant Mesothelioma

Background

To investigate the value of SMO and GLI1 genes in the hedgehog pathway in malignant mesothelioma specimens. Further study on the expression and prognosis of SMO and GLI1 in malignant mesothelioma tissues and the relationship between the two and the molecular mechanisms of mesothelioma immunity and to further investigate the prognostic value of mesothelioma expression.

Materials and Methods

Immunohistochemistry and RT-qPCR were applied to detect the expression of SMO and GLI1 proteins and mRNA in biopsy specimens and plasma cavity effusion specimens from malignant mesothelioma (n = 130) and benign mesothelial tissues (n = 50) and to analyze the clinicopathological significance and survival risk factors of SMO and GLI1 protein expression in mesothelioma. The mechanisms of mesothelioma cell expression and immune cell infiltration were investigated using bioinformatics methods.

Results

SMO and GLI1 in mesothelioma tissues detected high concordance between the diagnostic results of mesothelioma biopsy specimens and plasma cavity effusion specimens. The expression levels of SMO and GLI1 protein and mRNA in mesothelioma tissues were higher than those in benign mesothelioma tissues. The expression levels of SMO and GLI1 protein were correlated with the age, site, and asbestos exposure history of patients with mesothelioma. The expression levels of SMO and GLI1 protein were correlated with the expressions of ki67 and p53 (P < 0.05). SMO and GLI1 gene expression levels were negatively correlated with good prognosis in mesothelioma patients (P < 0.05). Cox proportional risk model indicated that protein expressions of invasion, lymph node metastasis, distant metastasis, staging, and genes were independent prognostic factors of mesothelioma. The GEPIA database showed the overall survival rate and the disease-free survival rate of mesothelioma patients in the high SMO and GLI1 expression groups; the UALCAN database analysis showed lower SMO expression levels in mesothelioma patients with more pronounced TP53 mutations (P = 0.001); GLI1 gene expression levels were strongly correlated with lymph node metastasis in mesothelioma patients (P = 0.009). Timer database analysis showed that the mechanism of immune cell infiltration was closely related to SMO and GLI1 expression. The degree of immune cell infiltration was strongly correlated with the prognosis of mesothelioma patients (P < 0.05).

Conclusion

The expression levels of both SMO and GLI1 proteins were higher than those of normal mesothelial tissues, and the mRNA expression levels also changed in the same direction. SMO and GLI1 gene expressions in mesothelioma were negatively correlated with age, site of occurrence, and history of asbestos exposure. Positive expression of SMO and GLI1 was negatively correlated with patient survival. The Cox proportional risk model showed that gender, history of asbestos exposure, site of occurrence, SMO, and GLI1 were independent prognostic factors for mesothelioma. The mechanism of immune cell infiltration in mesothelioma is closely related to the gene expression of both and the survival prognosis of mesothelioma patients.

Hepatocyte-specific Prominin-1 protects against liver injury-induced fibrosis by stabilizing SMAD7

Prominin-1 (PROM1), also known as CD133, is expressed in hepatic progenitor cells (HPCs) and cholangiocytes of the fibrotic liver. In this study, we show that PROM1 is upregulated in the plasma membrane of fibrotic hepatocytes. Hepatocellular expression of PROM1 was also demonstrated in mice (Prom1^CreER; R26^TdTom) in which cells expressed TdTom under control of the Prom1 promoter. To understand the role of hepatocellular PROM1 in liver fibrosis, global and liver-specific Prom1-deficient mice were analyzed after bile duct ligation (BDL). BDL-induced liver fibrosis was aggravated with increased phosphorylation of SMAD2/3 and decreased levels of SMAD7 by global or liver-specific Prom1 deficiency but not by cholangiocyte-specific Prom1 deficiency. Indeed, PROM1 prevented SMURF2-induced SMAD7 ubiquitination and degradation by interfering with the molecular association of SMAD7 with SMURF2. We also demonstrated that hepatocyte-specific overexpression of SMAD7 ameliorated BDL-induced liver fibrosis in liver-specific Prom1-deficient mice. Thus, we conclude that PROM1 is necessary for the negative regulation of TGFβ signaling during liver fibrosis.

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.

Double-Stranded RNA Structural Elements Holding the Key to Translational Regulation in Cancer: The Case of Editing in RNA-Binding Motif Protein 8A

Mesothelioma is an aggressive cancer associated with asbestos exposure. RNA-binding motif protein 8a (RBM8A) mRNA editing increases in mouse tissues upon asbestos exposure. The aim of this study was to further characterize the role of RBM8A in mesothelioma and the consequences of its mRNA editing. RBM8A protein expression was higher in mesothelioma compared to mesothelial cells. Silencing RBM8A changed splicing patterns in mesothelial and mesothelioma cells but drastically reduced viability only in mesothelioma cells. In the tissues of asbestos-exposed mice, editing of Rbm8a mRNA was associated with increased protein immunoreactivity, with no change in mRNA levels. Increased adenosine deaminase acting on dsRNA (ADAR)-dependent editing of Alu elements in the RBM8A 3′UTR was observed in mesothelioma cells compared to mesothelial cells. Editing stabilized protein expression. The unedited RBM8A 3′UTR had a stronger interaction with Musashi (MSI) compared to the edited form. The silencing of MSI2 in mesothelioma or overexpression of Adar2 in mesothelial cells resulted in increased RBM8A protein levels. Therefore, ADAR-dependent editing contributes to maintaining elevated RBM8A protein levels in mesothelioma by counteracting MSI2-driven downregulation. A wider implication of this mechanism for the translational control of protein expression is suggested by the editing of similarly structured Alu elements in several other transcripts.

Effects and prognostic values of miR-30c-5p target genes in gastric cancer via a comprehensive analysis using bioinformatics

Gastric cancer (GC) is a common cancer and the leading cause of cancer-related death worldwide. To improve the diagnosis and treatment of GC, it is necessary to identify new biomarkers by investigating the cellular and molecular mechanisms. In this study, miR-30c-5p expression was significantly down-regulated in GC tissues by comprehensive analysis using multiple databases. The target genes of miR-30c-5p with up-regulated expression level in GC were identified, including ADAM12 (a disintegrin and metalloproteinase12), EDNRA (the Endothelin receptor type A), STC1 (stanniocalcin 1), and CPNE8 (the calcium-dependent protein, copine 8). The expression level of ADAM12 was significantly related to depth of invasion (p = 0.036) in GC patients. The expression level of EDNRA was significantly related to grade (P = 0.003), depth of invasion (P = 0.019), and lymphatic metastasis (P = 0.001). The expression level of CPNE8 was significantly related to grade (P = 0.043) and TNM stage (P = 0.027).Gene set enrichment analysis showed that they might participate in GC progression through cancer-related pathways. CIBERSORT algorithm analysis showed that their expressions were related to a variety of tumor-infiltrating immune cells. The higher expression of those target genes might be the independent risk factor for poor survival of GC patients, and they might be potential prognostic markers in GC patients.

Tumor Immune Microenvironment and Genetic Alterations in Mesothelioma

Malignant pleural mesothelioma (MPM) is a rare and fatal disease of the pleural lining. Up to 80% of the MPM cases are linked to asbestos exposure. Even though its use has been banned in the industrialized countries, the cases continue to increase. MPM is a lethal cancer, with very little survival improvements in the last years, mirroring very limited therapeutic advances. Platinum-based chemotherapy in combination with pemetrexed and surgery are the standard of care, but prognosis is still unacceptably poor with median overall survival of approximately 12 months. The genomic landscape of MPM has been widely characterized showing a low mutational burden and the impairment of tumor suppressor genes. Among them, BAP1 and BLM are present as a germline inactivation in a small subset of patients and increases predisposition to tumorigenesis. Other studies have demonstrated a high frequency of mutations in DNA repair genes. Many therapy approaches targeting these alterations have emerged and are under evaluation in the clinic. High-throughput technologies have allowed the detection of more complex molecular events, like chromotripsis and revealed different transcriptional programs for each histological subtype. Transcriptional analysis has also paved the way to the study of tumor-infiltrating cells, thus shedding lights on the crosstalk between tumor cells and the microenvironment. The tumor microenvironment of MPM is indeed crucial for the pathogenesis and outcome of this disease; it is characterized by an inflammatory response to asbestos exposure, involving a variety of chemokines and suppressive immune cells such as M2-like macrophages and regulatory T cells. Another important feature of MPM is the dysregulation of microRNA expression, being frequently linked to cancer development and drug resistance. This review will give a detailed overview of all the above mentioned features of MPM in order to improve the understanding of this disease and the development of new therapeutic strategies.

The Evolving Landscape of the Molecular Epidemiology of Malignant Pleural Mesothelioma

Malignant pleural mesothelioma (MPM) is a rare and aggressive malignancy that most commonly affects the pleural lining of the lungs. It has a strong association with exposure to biopersistent fibers, mainly asbestos (80% of cases) and—in specific geographic regions—erionite, zeolites, ophiolites, and fluoro-edenite. Individuals with a chronic exposure to asbestos generally have a long latency with no or few symptoms. Then, when patients do become symptomatic, they present with advanced disease and a worse overall survival (about 13/15 months). The fibers from industrial production not only pose a substantial risk to workers, but also to their relatives and to the surrounding community. Modern targeted therapies that have shown benefit in other human tumors have thus far failed in MPM. Overall, MPM has been listed as orphan disease by the European Union. However, molecular high-throughput profiling is currently unveiling novel biomarkers and actionable targets. We here discuss the natural evolution, mainly focusing on the novel concept of molecular epidemiology. The application of innovative endpoints, quantification of genetic damages, and definition of genetic susceptibility are reviewed, with the ultimate goal to point out new tools for screening of exposed subject and for designing more efficient diagnostic and therapeutic strategies.

MicroRNA expression in lung tissues of asbestos-exposed mice: Upregulation of miR-21 and downregulation of tumor suppressor genes Pdcd4 and Reck

OBJECTIVES

Asbestos causes lung cancer and malignant mesothelioma in humans, but the precise mechanism has not been well understood. MicroRNA (miRNA) is a short non-coding RNA that suppresses gene expression and participates in human diseases including cancer. In this study, we examined the expression levels of miRNA and potential target genes in lung tissues of asbestos-exposed mice by microarray analysis.

METHODS

We intratracheally administered asbestos (chrysotile and crocidolite, 0.05 or 0.2 mg/instillation) to 6-week-old ICR male mice four times weekly. We extracted total RNA from lung tissues and performed microarray analysis for miRNA and gene expression. We also carried out real-time polymerase chain reaction (PCR), Western blotting, and immunohistochemistry to confirm the results of microarray analysis.

RESULTS

Microarray analysis revealed that the expression levels of 14 miRNAs were significantly changed by chrysotile and/or crocidolite (>2-fold, P < .05). Especially, miR-21, an oncogenic miRNA, was significantly upregulated by both chrysotile and crocidolite. In database analysis, miR-21 was predicted to target tumor suppressor genes programmed cell death 4 (Pdcd4) and reversion-inducing-cysteine-rich protein with kazal motifs (Reck). Although real-time PCR showed that Pdcd4 was not significantly downregulated by asbestos exposure, Western blotting and immunohistochemistry revealed that PDCD4 expression was reduced especially by chrysotile. Reck was significantly downregulated by chrysotile in real-time PCR and immunohistochemistry.

CONCLUSIONS

This is the first study demonstrating that miR-21 was upregulated and corresponding tumor suppressor genes were downregulated in lung tissues of asbestos-exposed animals. These molecular events are considered to be an early response to asbestos exposure and may contribute to pulmonary toxicity and carcinogenesis.

Diagnostic value of microRNAs for malignant pleural mesothelioma: A mini-review

Malignant pleural mesothelioma (MPM) is a type of cancer originating from the pleura with high aggressiveness and poor prognosis. A timely diagnosis is crucial to improve its prognosis. Laboratory biomarkers have significant advantages of reduced invasiveness, low cost, and are observer‐independent, and therefore represent a promising diagnostic tool for MPM. MicroRNA is a family of non‐coding RNA that regulates gene expression at the post‐transcriptional level. Accumulated studies showed that microRNA, either in tissue, circulating, and body fluid, has potential diagnostic value for various disorders. Here, we reviewed the diagnostic value of microRNA for MPM.

RNA editing in mesothelioma: a look forward

RNA editing is a post-transcriptional process increasing transcript diversity, thereby regulating different biological processes. We recently observed that mutations resulting from RNA editing due to hydrolytic deamination of adenosine increase during the development of mesothelioma, a rare cancer linked to chronic exposure to asbestos. This review gathers information from the published literature and public data mining to explore several aspects of RNA editing and their possible implications for cancer growth and therapy. We address possible links between RNA editing and particular types of mesothelioma genetic and epigenetic alterations and discuss the relevance of an edited substrate in the context of current chemotherapy or immunotherapy.

Mesothelioma Biomarkers: Discovery in Search of Validation

Malignant pleural mesothelioma (MPM) is an asbestos-related neoplasm that can only be treated successfully when correctly diagnosed and treated early. The asbestos-exposed population is a high-risk group that could benefit from sensitive and specific blood- or tissue-based biomarkers. We review recent work with biomarker development in MPM and literature of the last 20 years on the most promising blood- and tissue-based biomarkers. Proteomic, genomic, and epigenomic platforms are covered. SMRP is the only validated blood-based biomarker with diagnostic, monitoring and prognostic value. To strengthen development and testing of MPM biomarkers, cohorts for validation must be established by enlisting worldwide collaborations.

Identification of a Five-Gene Signature for Predicting Survival in Malignant Pleural Mesothelioma Patients

Malignant pleural mesothelioma (MPM), predominantly caused by asbestos exposure, is a highly aggressive cancer with poor prognosis. The staging systems currently used in clinics is inadequate in evaluating the prognosis of MPM. In this study, a five-gene signature was developed and enrolled into a prognostic risk score model by LASSO Cox regression analysis based on two expression profiling datasets (GSE2549 and GSE51024) from Gene Expression Omnibus (GEO). The five-gene signature was further validated using the Cancer Genome Atlas (TCGA) MPM dataset. Univariate and multivariate Cox analyses proved that the five-gene signature was an independent prognostic factor for MPM. The signature remained statistically significant upon stratification by Brigham stage, AJCC stage, gender, tumor size, and lymph node status. Time-dependent receiver operating characteristic (ROC) curve indicated good performance of our model in predicting 1- and 2-years overall survival in MPM patients. The C-index was 0.784 for GSE2549 and 0.753 for the TCGA dataset showing moderate predictive accuracy of our model. Furthermore, Gene Set Enrichment Analysis suggested that the five-gene signature was related to pathways resulting in MPM tumor progression. Together, we have established a five-gene signature significantly associated with prognosis in MPM patients. Hence, the five-genes signature may serve as a potentially useful prognostic tool for MPM patients.

Mesothelioma Biomarkers: A Review Highlighting Contributions from the Early Detection Research Network

Malignant pleural mesothelioma (MPM) is an asbestos-related neoplasm, which can be treated successfully only if correctly diagnosed and treated in early stages. The asbestos-exposed population serves as a high-risk group that could benefit from sensitive and specific blood- or tissue-based biomarkers. This review details the recent work with biomarker development in MPM and the contributions of the NCI Early Detection Research Network Biomarker Developmental Laboratory of NYU Langone Medical Center. The literature of the last 20 years was reviewed to comment on the most promising of the blood- and tissue-based biomarkers. Proteomic, genomic, and epigenomic platforms as well as novel studies such as "breath testing" are covered. Soluble mesothelin-related proteins (SMRP) have been characterized extensively and constitute an FDA-approved biomarker in plasma with diagnostic, monitoring, and prognostic value in MPM. Osteopontin is found to be a valuable prognostic biomarker for MPM, while its utility in diagnosis is slightly lower. Other biomarkers, such as calretinin, fibulin 3, and High-Mobility Group Box 1 (HMGB1), remain under study and need international validation trials with large cohorts of cases and controls to demonstrate any utility. The EDRN has played a key role in the development and testing of MPM biomarkers by enlisting collaborations all over the world. A comprehensive understanding of previously investigated biomarkers and their utility in screening and early diagnosis of MPM will provide guidance for further future research.See all articles in this CEBP Focus section, "NCI Early Detection Research Network: Making Cancer Detection Possible."

Overexpression of miR-199/214 is a distinctive feature of iron-induced and asbestos-induced sarcomatoid mesothelioma in rats

Malignant mesothelioma (MM) is one of the most lethal tumors in humans. The onset of MM is linked to exposure to asbestos, which generates reactive oxygen species (ROS). ROS are believed to be derived from the frustrated phagocytosis and the iron in asbestos. To explore the pathogenesis of MM, peritoneal MM was induced in rats by the repeated intraperitoneal injection of iron saccharate and nitrilotriacetate. In the present study, we used microarray techniques to screen the microRNA (miR) expression profiles of these MM. We observed that the histological subtype impacted the hierarchical clustering of miR expression profiles and determined that miR-199/214 is a distinctive feature of iron saccharate-induced sarcomatoid mesothelioma (SM). Twist1, a transcriptional regulator of the epithelial-mesenchymal transition, has been shown to activate miR-199/214 transcription; thus, the expression level of Twist1 was examined in iron-induced and asbestos-induced mesotheliomas in rats. Twist1 was exclusively expressed in iron saccharate-induced SM but not in the epithelioid subtype. The Twist1-miR-199/214 axis is activated in iron saccharate-induced and asbestos-induced SM. The expression levels of miR-214 and Twist1 were correlated in an asbestos-induced MM cell line, suggesting that the Twist1-miR-199/214 axis is preserved. MeT5A, an immortalized human mesothelial cell line, was used for the functional analysis of miR. The overexpression of miR-199/214 promoted cellular proliferation, mobility and phosphorylation of Akt and ERK in MeT5A cells. These results indicate that miR-199/214 may affect the aggressive biological behavior of SM.

MicroRNAs diagnostic and prognostic value as predictive markers for malignant mesothelioma

Malignant mesothelioma is an aggressive tumor resistant to current therapies with a latency period ranging between 20 and 60 years, caused by inhalation of asbestos fibers, that continues to represent a social and healthcare issue. The high percentage of people exposed to asbestos for professional or environmental reasons is associated with the high biopersistence of its fibers and with its widespread use in the last century. Approximately 20-40% of men report an occupational history that might have caused the workplace exposure (criteria Helsinki, 1997). Some authors are evaluating the possible use of bioindicators as a screening and early diagnosis tool. In this regard, the use of microRNAs has been proposed as powerful diagnostic and prognostic biomarkers for many tumors and human diseases. This review focuses on the current state of knowledge on the key role of microRNAs expression as new malignant mesothelioma biomarkers, in early clinical diagnostic applications.

Functional effects of differentially expressed microRNAs in A549 cells exposed to MWCNT-7 or crocidolite

Multi-walled carbon nanotubes (MWCNT) are engineered nanomaterials widely used in industrial and biomedical applications. Yet, MWCNT inhalation may induce pulmonary adverse effects, and the MWCNT-7 (Mitsui-7) has been classified as possibly carcinogenic to humans. However, its molecular mechanisms of action are poorly understood and there are no biomarkers of exposure for occupational monitoring. Several pulmonary diseases, including lung cancer, have been associated with alterations in microRNA expression that are used as biomarkers of disease progression, and differentially-expressed microRNAs (DE miRNAs) can also allow understanding the molecular effects induced by a toxicant. In this study, we identify DE miRNAs in A549 alveolar epithelial cells following 24 h exposure to MWCNT-7 or crocidolite, as well as their enriched cellular functional pathways. These indicate that both materials change cell survival, differentiation and proliferative properties under the influence of AMPK, FoxO, TGF-β and Hippo pathways, and their metabolic activity and cell-to-cell communication. In addition, MWCNT-7 affects the actin cytoskeleton, ubiquitin mediated proteolysis, and ECM-receptor interactions; crocidolite the PI3K-Akt and mTOR pathways, endocytosis, and central carbon metabolism. Since deregulation of these pathways may be related to carcinogenesis, an interaction network of DE miRNAs and corresponding target cancer-related genes was constructed, highlighting the carcinogenic potential of Mitsui-7.

Role of MicroRNA-30c in cancer progression

MicroRNAs (miRNAs or miRs) is a non-coding small RNA of a type of 18~24 nucleotide-regulated gene that has been discovered in recent years. It mainly degrades the target gene mRNA or inhibits its translation process through the complete or incomplete bindings with 3'UTR of target genes, followed by the regulation of individual development, apoptosis, proliferation, differentiation and other life activities through the post-transcriptional regulation. Among many miRNAs, the microRNA family, miR-30, plays diverse roles in these key process of neoplastic transformation, metastasis, and clinical outcomes in different cancer progression. As key member of miR-30, miR-30c is regulated by oncogenic transcription factors and cancer progression related genes. Recently, numerous studies have demonstrated that the aberrant expression of miR-30c was significantly associated with the majority of human cancer progression. In this review, the diverse roles of miR-30c in different cancer progression such as the cellular and molecular mechanisms, the potential applications in clinics were summarized to speculate the benefits of miR-30c over-expression in cancer treatment and prognosis.

Epigenetic Regulation of miRNA Expression in Malignant Mesothelioma: miRNAs as Biomarkers of Early Diagnosis and Therapy

Asbestos exposure leads to epigenetic and epigenomic modifications that, in association with ROS-induced DNA damage, contribute to cancer onset. Few miRNAs epigenetically regulated in MM have been described in literature; miR-126, however, is one of them, and its expression is regulated by epigenetic mechanisms. Asbestos exposure induces early changes in the miRNAs, which are reversibly expressed as protective species, and their inability to reverse reflects the inability of the cells to restore the physiological miRNA levels despite the cessation of carcinogen exposure. Changes in miRNA expression, which results from genetic/epigenetic changes during tumor formation and evolution, can be detected in fluids and used as cancer biomarkers. This article has reviewed the epigenetic mechanisms involved in miRNA expression in MM, focusing on their role as biomarkers of early diagnosis and therapeutic effects.

MicroRNAs - novel biomarkers for malignant pleural effusions

Lung cancer is one of the most common causes of cancer death. Its poor prognosis can be attributed to the patients’ advanced or metastatic presentation at the time of diagnosis. To improve and accelerate the diagnosis, better therapeutic and diagnostic methods are constantly being sought. MicroRNAs (miRNAs) are short nucleotide sequences of single-stranded, non-coding RNA that function as critical post-transcriptional regulators of gene expression. They are identified not only intracellularly, but also in physiological and pathological body fluids. These molecules are responsible for the regulation of approximately 33% of human genes, either regulating the expression of both oncogenes and suppressor genes or acting directly as an oncogene or suppressor gene itself. MiRNAs can contribute to the formation of cancer. The high specificity and sensitivity of miRNAs have been demonstrated with various malignant diseases, and for this reason, they raise particular interest as new and perspective biomarkers of tumours. Our work summarises the available information from recent years regarding the possibility of using miRNAs as biomarkers in the diagnosis of neoplasms. In this review, we focused on malignant pleural effusions with an emphasis on non-small cell lung cancer (NSCLC).

miR-625-3p and lncRNA GAS5 in Liquid Biopsies for Predicting the Outcome of Malignant Pleural Mesothelioma Patients Treated with Neo-Adjuvant Chemotherapy and Surgery

Combining neo-adjuvant chemotherapy and surgery is part of multimodality treatment of malignant pleural mesothelioma (MPM), but not all patients benefit from this approach. In this exploratory analysis, we investigated the prognostic value of circulating miR-625-3p and lncRNA GAS5 after neo-adjuvant chemotherapy. 36 MPM patients from the SAKK 17/04 trial (NCT00334594), whose blood was available before and after chemotherapy were investigated. RNA was isolated from plasma and reverse transcribed into cDNA. miR-16-5p and β-actin were used as a reference gene for miR-625-3p and GAS5, respectively. After exclusion of samples due to hemolysis or RNA degradation, paired plasma samples from 32 patients before and after chemotherapy were further analyzed. Quantification of miR-625-3p levels in all 64 samples revealed a bimodal distribution and cloning and sequencing of miR-625-3p qPCR product revealed the presence of miR-625-3p isomiRs. Relative change of the circulating miR-625-3p and GAS5 levels after chemotherapy showed that increased circulating miR-625-3p and decreased GAS5 was significantly associated with disease progression (Fisher's test, p = 0.0393). In addition, decreased levels of circulating GAS5 were significantly associated with shorter overall and progression-free survival. Our exploratory analysis revealed a potential value of circulating non-coding RNA for selection of patients likely to benefit from surgery after platinum-based adjuvant chemotherapy.

Interplay of non-coding RNAs and approved antimetabolites such as gemcitabine and pemetrexed in mesothelioma

Gemcitabine and pemetrexed are clinically approved antimetabolites for the therapy of mesothelioma diseases. These drugs are often applied in combination with platinum complexes and other drugs. The activity of antimetabolites depended on the expression levels of certain non-coding RNAs, in particular, of small microRNAs (miRNAs) and long non-coding RNAs (lncRNAs). The development of tumor resistance towards antimetabolites was regulated by non-coding RNAs. An overview of the interplay between gemcitabine/pemetrexed antimetabolites and non-coding RNAs in mesothelioma is provided. Further to this, various non-coding RNA-modulating agents are discussed which displayed positive effects on gemcitabine or pemetrexed treatment of mesothelioma diseases. A detailed knowledge of the connections of non-coding RNAs with antimetabolites will be constructive for the design of improved therapies in future.

Development and Validation of a Prognostic Signature for Malignant Pleural Mesothelioma

Introduction: Dysregulated genes play a critical role in the development and progression of cancer, suggesting their potential as novel independent biomarkers for cancer diagnosis and prognosis. Prognostic model-based gene expression profiles are not widely utilized in clinical medicine. We investigated the prognostic significance of an expression profile-based gene signature for outcome prediction in patients with malignant pleural mesothelioma (MPM).

Methods: The gene expression profiles of a large cohort of patients with MPM were obtained and analyzed by repurposing publicly available microarray data. A gene-based risk score model was developed with the training dataset and then validated with the TCGA-MESO (mesothelioma) dataset. The time-dependent receiver operating characteristic (ROC) curve was used to evaluate the prognostic performance of survival prediction. The biological function of the prognostic genes was predicted using bioinformatics analysis.

Results: Three genes in the training dataset (GSE2549) were identified as significantly associated with the overall survival (OS) of patients with MPM and were combined to develop a three-gene prognostic signature to stratify patients into low-risk and high-risk groups. The MPM patients of the training dataset in the low-risk group exhibited longer OS than those in the high-risk group (HR = 0.25, 95% CI = 0.11–0.56, P < 0.001). Similar prognostic values for the three-gene signature were observed in the validated TCGA-MESO cohort (HR = 0.53 95% CI = 0.33–0.85, P = 0.008). ROC analysis also demonstrated the good performance in predicting 3-year OS in the GEO and TCGA cohorts (KM-AUC for GEO = 0.989, KM-AUC for TCGA = 0.618). The C-statistic for the 3-gene model was 0.761. Validation with TCGA-MESO confirmed the model's ability to discriminate between risk groups in an alternative data set with fair performance (C-statistic: 0.68). Functional enrichment analysis suggested that these three genes may be involved in genetic and epigenetic events with known links to MPM.

Conclusions: This study has identified and validated a novel 3-gene model to reliably discriminate patients at high and low risk of death in unselected populations of patients with MPM. Further larger, prospective multi-institutional cohort studies are necessary to validate this model.

MicroRNAs for the Diagnosis and Management of Malignant Pleural Mesothelioma: A Literature Review

Malignant pleural mesothelioma (MPM) is a rare and aggressive tumor with a variable incidence among different countries. Occupational asbestos exposure is the most important etiological factor and a very long latency period is widely reported. In the early phase of the disease, clinical signs are absent or not specific. For this reason, the diagnosis is frequently achieved only in the advanced stages. The histopathological diagnosis per se is also very complex, and no known factor can predict the prognosis with certainty. Nonetheless, current survival rates remain very low, despite the use of standard treatments, which include surgery, chemotherapy and radiotherapy. The identification of new prognostic and/or diagnostic biomarkers, and the discovery of therapeutic targets is a priority and could lead to a real significant impact on the management of malignant pleural mesothelioma. In this scenario, the role of microRNAs is becoming increasingly relevant, with the promise of a quick translation in the current clinical practice. Despite the relative novelty of this field, the number of works and candidate microRNAs that are present in literature is striking. Unfortunately, to date the microRNAs with the most clinical relevance for MPM are still matter of debate, probably due to the variety of approaches, techniques, and collected samples. Although specific microRNAs (e.g., let-7, miR-15 and miR-16, miR-21, miR-34a, and the miR-200 family) have been reported several times from different groups, the heterogeneity of published data reinforces the need of more comprehensive and unified studies on this topic. In this review we collect and discuss the studies focused on the involvement of microRNAs in different aspects of MPM, from their biological role in tumorigenesis and progression, to their possible application as diagnostic, prognostic and predictive biomarkers. Lastly, we examine their potential value as for the design of therapeutic approaches that could benefit MPM patients.

Clinical significance of serum DRAM1 mRNA, ARSA mRNA, hsa-miR-2053 and lncRNA-RP1-86D1.3 axis expression in malignant pleural mesothelioma

AIM AND BACKGROUND

Malignant pleural mesothelioma (MPM) is a lethal cancer mainly caused by chronic exposure of asbestos. In this pilot study, we aimed to assess the expression of serum RNA-based biomarker panel exploring their clinical utility as diagnostic and prognostic biomarkers for MPM.

METHODS

We have selected an MPM-specific RNA-based biomarker panel through bioinformatics analysis based on the integration of DNA damage regulated autophagy modulator 1 (DRAM1) and arylsulfatase A ( ARSA) gene expression with their epigenetic regulators microRNA ( miR-2053) and long noncoding RNA ( lncRNA-RP1-86D1.3). Then, quantitative real-time polymerase chain reaction (qPCR) validation in sera of 60 MPM patients, 20 chronic asbestos exposure patients, and 20 healthy volunteers was done. Lastly, the prognostic power of the selected panel was assessed.

RESULTS

The expression of serum DRAM1 messenger RNA (mRNA), ARSA mRNA, hsa-miR-2053 and lncRNA-RP1-86D1.3 were positive in 78.3%, 90%, 85%, and 83.3% of MPM patients, respectively. The RNA-based biomarker panel was able to discriminate between MPM patients and controls with high accuracy and their combined sensitivity reached 100% for the diagnosis of MPM. Kaplan-Meier analysis showed that hsa-miR-2053 is an independent prognostic factor of MPM.

CONCLUSION

Our preliminary data revealed that the chosen RNAs play an important role in driving MPM development and progression.

Prognostic value of miR-17-5 p in gastrointestinal cancers: a systematic review and meta-analysis

BACKGROUND

There are accumulating studies investigating the aberrant expression of microRNAs in tumor patients. As an important member of miR-17/92 cluster, miR-17-5 p has been identified as a potential prognostic factor for survival in tumor patients. We conducted this meta-analysis aimed to assess the effect of miR-17-5 p as a prognostic biomarker for gastrointestinal tumor patients.

MATERIALS AND METHODS

Eligible studies were enrolled by searching the online databases of PubMed, Embase, Web of Science, China National Knowledge Infrastructure, and WanFang Data until September 2017. We calculated pooled hazard ratios (HRs) and 95% CI of miR-17-5 p for overall survival and disease-free survival.

RESULTS

In the categorical variable analysis, we identified 11 studies with 1,279 patients. The pooled analyses suggested that overexpression of miR-17-5 p may predict poor overall survival (HR = 1.86, 95% CI: 1.55-2.25, P<0.001) and disease-free survival (HR = 1.43, 95% CI: 1.01-2.03, P=0.046) in patients with gastrointestinal tumors. Subgroup analysis showed the pooled HR of overall survival was more significant in tissue specimen, Asian patients, and digestive tract tumors. But there was no correlation between the outcomes and European patients.

CONCLUSIONS

This meta-analysis suggested that miR-17-5 p has predictive effects on overall survival and disease-free survival of patients with gastrointestinal tumors.

Mesotheliomas in Genetically Engineered Mice Unravel Mechanism of Mesothelial Carcinogenesis

Malignant mesothelioma (MM), a rare and severe cancer, mainly caused as a result of past-asbestos exposure, is presently a public health concern. Current molecular studies aim to improve the outcome of the disease, providing efficient therapies based on the principles of precision medicine. To model the molecular profile of human malignant mesothelioma, animal models have been developed in rodents, wild type animals and genetically engineered mice harbouring mutations in tumour suppressor genes, especially selecting genes known to be inactivated in human malignant mesothelioma. Animals were either exposed or not exposed to asbestos or to other carcinogenic fibres, to understand the mechanism of action of fibres at the molecular level, and the role of the selected genes in mesothelial carcinogenesis. The aim of the manuscript was to compare mesothelioma models to human malignant mesothelioma and to specify the clue genes playing a role in mesothelial carcinogenesis. Collectively, MM models recapitulate the clinical features of human MM. At least two altered genes are needed to induce malignant mesothelioma in mice. Two pathways regulated by Cdkn2a and Trp53 seem independent key players in mesothelial carcinogenesis. Other genes and pathways appear as bona fide modulators of the neoplastic transformation.

Genomics and Epigenetics of Malignant Mesothelioma

Malignant mesothelioma is an aggressive and lethal asbestos-related disease. Diagnosis of malignant mesothelioma is particularly challenging and is further complicated by the lack of disease subtype-specific markers. As a result, it is especially difficult to distinguish malignant mesothelioma from benign reactive mesothelial proliferations or reactive fibrosis. Additionally, mesothelioma diagnoses can be confounded by other anatomically related tumors that can invade the pleural or peritoneal cavities, collectively resulting in delayed diagnoses and greatly affecting patient management. High-throughput analyses have uncovered key genomic and epigenomic alterations driving malignant mesothelioma. These molecular features have the potential to better our understanding of malignant mesothelioma biology as well as to improve disease diagnosis and patient prognosis. Genomic approaches have been instrumental in identifying molecular events frequently occurring in mesothelioma. As such, we review the discoveries made using high-throughput technologies, including novel insights obtained from the analysis of the non-coding transcriptome, and the clinical potential of these genetic and epigenetic findings in mesothelioma. Furthermore, we aim to highlight the potential of these technologies in the future clinical applications of the novel molecular features in malignant mesothelioma.

Quantifying the prognostic significance of microRNA-17/17-5P in cancers: a meta-analysis based on published studies

Objective

The aim of this study was to investigate the prognostic value of mircoRNA-17 and mircoRNA-17-5P (miR-17/17-5P) in patients with cancer.

Materials and methods

We conducted a comprehensive search on published literature following the guidelines of the meta-analysis of observational studies in epidemiology group for design, implementation, and reporting. The methodological qualities for included studies were assessed using the quality in prognosis studies. The pooled hazard ratios (HRs) with 95% CIs for overall survival (OS) and progression-free survival/recurrence-free survival/disease-free survival (PFS/RFS/DFS) were calculated to appraise the associations between miR-17/17-5P expression and cancer prognosis.

Results

A total of 21 studies involving 2099 subjects were analyzed in evidence synthesis. The results showed that high expression of miR-17 was associated with poor OS (HR=2.14; 95% CI: 1.69-2.71, P<0.001) in patients with cancer, especially in Caucasian (HR=2.23; 95% CI: 1.58-3.14, P<0.001) and digestive tract cancer (HR=1.29, 95% CI: 1.03-1.63, P=0.03), and miR-17 expression was significantly correlated with PFS/RFS in cancer patients (HR=1.69, 95% CI: 1.29-2.22, P<0.001). miR-17-5P overexpression was significantly linked with poor OS in cancer patients (HR=1.66; 95% CI: 1.31-2.09, P=0.00), especially in Asian (HR=1.81; 95% CI: 1.37-2.40, P<0.001), digestive tract cancer (HR=1.80; 95% CI: 1.29-2.50, P<0.001), and serum sample (HR=1.76; 95% CI: 1.29-2.41, P<0.001). miR-17-5P expression was significantly associated with DFS in cancer patients (HR=1.58, 95% CI: 1.07-2.35, P=0.02).

Conclusion

High expression of miR-17 and miR-17-5P are significantly associated with poor survival in patients with cancer. This indicated that miR-17/17-5P may be a novel prognostic indicator in cancer.

MiR-21 over-expression and Programmed Cell Death 4 down-regulation features malignant pleural mesothelioma

Background

Differential diagnosis between malignant pleural mesothelioma (MPM) and benign mesothelial conditions is still challenging and there is a lack of useful markers. Programmed cell death 4 (PDCD4) is a well-known tumor suppressor gene in several cancers, its post-transcriptional activity is directly controlled by miR-21, whose over-expression has been recently reported in MPM compared to normal mesothelium. Aim of this study was to test this suppressor gene as a possible new marker of malignant transformation in mesothelial cells, as well as a new prognostic marker.

Methods

PDCD4 nuclear expression was assessed by immunohistochemistry (IHC) in 40 non-neoplastic pleural (NNP) and 40 MPM formalin-fixed and paraffin-embedded specimens. PDCD4 and miR-21 expressions were analyzed by qRT-PCR in all cases. In situ hybridization (ISH) of miR-21 was performed in 5 representative cases of both groups. The prognostic relevance of PDCD4 was assessed in a public available gene expression dataset.

Results

IHC showed that PDCD4 nuclear expression was significantly lower in MPM than in NNP. PDCD4 was down-regulated, whereas miR-21 was over-expressed in MPM cases compared to NNP ones. ISH detected miR-21 only in MPM specimens. Down-expression of PDCD4 was found significantly associated with short overall survival in publicly available data.

Conclusions

These findings highlighted a switch between PDCD4 and miR-21 expression in MPM. Further studies should assess the diagnostic reliability of these two markers for MPM in biopsy and effusion specimens.

RBL2/p130 is a direct AKT target and is required to induce apoptosis upon AKT inhibition in lung cancer and mesothelioma cell lines

The retinoblastoma (RB) protein family includes RB1/p105, RBL1/p107, and RBL2/p130, which are key factors in cell-cycle regulation and stand at the crossroads of multiple pathways dictating cell fate decisions. The role of RB proteins in apoptosis is controversial because they can inhibit or promote apoptosis depending on the context, on the apoptotic stimuli and on their intrinsic status, impacting on the response to antitumoral treatments. Here we identified RBL2/p130 as a direct substrate of the AKT kinase, a key antiapoptotic factor hyperactive in multiple cancer types. We showed that RBL2/p130 and AKT1 physically interact and AKT phosphorylates RBL2/p130 Ser941, located in the pocket domain, but not when this residue is mutated into Ala. We found that pharmacological inhibition of AKT, through the highly selective AKT inhibitor VIII (AKTiVIII), impairs RBL2/p130 Ser941 phosphorylation and increases RBL2/p130 stability, mRNA expression and nuclear levels in both lung cancer and mesothelioma cell lines, mirroring the more extensively studied effects on the p27 cell-cycle inhibitor. Consistently, AKT inhibition reduced cell viability, induced cell accumulation in G0/G1, and triggered apoptosis, which proved to be largely dependent on RBL2/p130 itself, as shown upon RBL2/p130 silencing. AKT inhibition induced RBL2/p130-dependent apoptosis also in HEK-293 cells, in which re-expression of a short hairpin-resistant RBL2/p130 was able to rescue AKTiVIII-induced apoptosis upon RBL2/p130 silencing. Our data also showed that the combination of AKT and cyclin-dependent kinases (CDK) inhibitors, which converge on the re-activation of RBL2/p130 antitumoral potential, could be a promising anticancer strategy.

Epithelioid peritoneal mesothelioma: a hybrid phenotype within a mesenchymal-epithelial/epithelial-mesenchymal transition framework

The aim of this study was to reconsider the biological characteristics of epithelioid malignant peritoneal mesothelioma (E-MpM) in the light of new concepts about epithelial mesenchymal transition and mesenchymal epithelial reverse transition (EMT/MErT) and the role of epigenetic reprogramming in this context. To this end we profiled surgical specimens and derived cells cultures by a number of complementary approaches i.e. immunohistochemistry, immunofluorescence, in situ hybridization, biochemistry, pluripotent stem cell arrays, treatments with cytokines, growth factors and specific inhibitors.The analyses of the surgical specimens showed that i) EZH2 is expressed throughout the spectrum of MpM, ii) that E-MpM (including the high-grade undifferentiated form) are characterised by c-MYC and miRNA 17-5p expression, and iii) that progression to sarcomatoid MpM is dictated by EMT regulators. They also showed that E-MpM expressed c-MET and are enriched in E- and P-cadherins- and VEGFR2-expressing CSCs, thus strongly supporting a role for MErT reprogramming in endowing E-MpM tumour cells with stemness and plasticity, and hence with a drug resistant phenotype. The cell culture-based experiments confirmed the stemness traits and plasticity of E-MpM, and support the view that EZH2 is a druggable target in this tumor.

Diagnostic value of microRNAs in asbestos exposure and malignant mesothelioma: systematic review and qualitative meta-analysis

Background

Asbestos is a harmful and exceptionally persistent natural material. Malignant mesothelioma (MM), an asbestos-related disease, is an insidious, lethal cancer that is poorly responsive to current treatments. Minimally invasive, specific, and sensitive biomarkers providing early and effective diagnosis in high-risk patients are urgently needed. MicroRNAs (miRNAs, miRs) are endogenous, non-coding, small RNAs with established diagnostic value in cancer and pollution exposure. A systematic review and a qualitative meta-analysis were conducted to identify high-confidence miRNAs that can serve as biomarkers of asbestos exposure and MM.

Methods

The major biomedical databases were systematically searched for miRNA expression signatures related to asbestos exposure and MM. The qualitative meta-analysis applied a novel vote-counting method that takes into account multiple parameters. The most significant miRNAs thus identified were then subjected to functional and bioinformatic analysis to assess their biomarker potential.

Results

A pool of deregulated circulating and tissue miRNAs with biomarker potential for MM was identified and designated as “mesomiRs” (MM-associated miRNAs). Comparison of data from asbestos-exposed and MM subjects found that the most promising candidates for a multimarker signature were circulating miR-126-3p, miR-103a-3p, and miR-625-3p in combination with mesothelin. The most consistently described tissue miRNAs, miR-16-5p, miR-126-3p, miR-143-3p, miR-145-5p, miR-192-5p, miR-193a-3p, miR-200b-3p, miR-203a-3p, and miR-652-3p, were also found to provide a diagnostic signature and should be further investigated as possible therapeutic targets.

Conclusion

The qualitative meta-analysis and functional investigation confirmed the early diagnostic value of two miRNA signatures for MM. Large-scale, standardized validation studies are needed to assess their clinical relevance, so as to move from the workbench to the clinic.

Circulating microRNAs found dysregulated in ex-exposed asbestos workers and pleural mesothelioma patients as potential new biomarkers

Malignant pleural mesothelioma (MPM), a fatal cancer, is an occupational disease mostly affecting workers ex-exposed to asbestos fibers. The asbestos, a cancerogenic mineral of different chemical composition, was widely employed in western Countries in industrial manufactures of different types. MPM may arise after a long latency period, up to five decades. MPM is resistant to conventional chemo- and radio-therapies. Altogether, these data indicate that the identification of new and specific markers are of a paramount importance for an early diagnosis and treatment of MPM. In recent years, microRNAs expression was found dysregulated in patients, both in cancer cells and sera, affected by tumors of different histotypes, including MPM. Cell and circulanting microRNAs, found to be dysregulated in this neoplasia, were proposed as new biomarkers. It has been reported that circulating microRNAs are stable in biological fluids and could be employed as potential MPM biomarkers. In this investigation, circulating microRNAs (miR) from serum samples of MPM patients and workers ex-exposed to asbestos fibers (WEA) and healthy subjects (HS) were comparatively analyzed by microarray and RT-qPCR technologies. Our results allowed (i) to select MiR-3665, an endogenous stable microRNA, as the internal control to quantify in our analyses circulating miRNAs; to detect (ii) miR-197-3p, miR-1281 and miR 32-3p up-regulated in MPM compared to HS; (iii) miR-197-3p and miR-32-3p up-regulated in MPM compared to WEA; (iv) miR-1281 up-regulated in both MPM and WEA compared to HS. In conclusion, three circulating up-regulated microRNAs, i.e. miR-197-3p, miR-1281 and miR-32-3p are proposed as potential new MPM biomarkers.

Clinical evaluation of circulating miR-548a-3p and -20a expression in malignant pleural mesothelioma patients

AIM

miRNAs may act as promising diagnostic and prognostic biomarkers of mesothelioma. This study integrates serum  miR-548a-3p and miR-20a expression based on in silico data analysis followed by clinical validation in malignant mesothelioma patients (malignant pleural mesothelioma [MPM]).

PATIENTS & METHODS

Serum miR-548a-3p and  miR-20a level was assessed in the serum of patients with MPM, chronic asbestos exposure and healthy volunteers by quantitative real-time PCR.

RESULTS

The expression of serum miR-548a-3p and  miR-20a was positive in 91.6 and 96.7% MPM patients, respectively. Both miRNAs were able to segregate between cases and controls. The sensitivity of the combined chosen serum miRNAs reached 100% in the diagnosis of MPM.

CONCLUSION

The current work revealed that sera miR-548a-3p and miR-20a may serve as promising novel diagnostic tools for MPM.

Serum mesothelin and other biomarkers: what have we learned in the last decade?

In the last decade there is been much interest in noninvasive, economic and well-accepted diagnostic tests for screening of subjects exposed to asbestos, and in patients with malignant pleuric mesothelioma (MPM) for diagnosis or monitoring response to treatment. Several biomarkers have been suggested as tools for screening and early diagnosis of MPM. Currently, in patients with MPM, have been reported high levels of soluble mesothelin-related peptides (SMRP), plasmatic osteopontin (pOPN), vimentin, fibulin-3 and many others as promising marker for diagnosis, even their use in prevention monitoring is still discussed. In this type of disease, a key role could be played by miRNAs, which expression has been investigated in a large series of MPM to examine new pathways useful in diagnosis, prognosis and therapy. An altered expression of some proteins has been reported, useful as biomarkers, in comparative proteomic analysis of malignant pleural mesothelioma. New promising markers are nowadays under study and alone or better in combination, they'll be very helpful in diagnosing, monitoring mesothelioma patients or for screening of risk groups.

Biomarkers in the prevention and follow-up of workers exposed to asbestos

Although in most developed countries the use of asbestos is banned, there is still a consistent portion of the world where asbestos extraction, trading and manufacturing of asbestos-made products is largely diffuse. Worldwide, hundreds of millions of people are at risk of developing an asbestos caused disease because of occupational, environmental or domestic exposure. The WHO estimates that asbestos is responsible for more than 100,000 deaths yearly. This scenario has prompted the research on biomarkers potentially useful for early diagnosis, prognosis and preventive programs on exposed population as well. Here we reviewed the up-to-date literature on this field of research highlighting that along with mesothelin and osteopontin (OPN), some more recently investigated molecules, such as high mobility group box 1 (HMGB1) protein, fibulin-3 and some miRNAs showed very promising. Most of the carried-out studies showed an interesting diagnostic and prognostic performance of some biomarkers, but since they usually lack adequate either specificity or sensitivity, their use in screening or in preventive programs is still not recommended on a routine basis. However, this review suggests the need for more reliable experimental design involving larger population and preferring longitudinal screening of asbestos exposed individuals rather than a single baseline assessment investigation. In addition, given their better diagnostic accuracy, the use of panels including several biomarkers is highly recommended.

Translational applications of microRNAs in cancer, and therapeutic implications

The search for targeted novel therapies for cancer is ongoing. MicroRNAs (miRNAs) display a number of characteristics making them an attractive and realisable option. In this review, we explore these applications, ranging from diagnostics, prognostics, disease surveillance, to being a primary therapy or a tool to sensitise patients to treatment modalities such as chemotherapy and radiotherapy. We take a particular perspective towards miRNAs and their impact on rare cancers. Advancement in the delivery of miRNAs, from viral vectors and liposomal delivery to nanoparticle based, has led to a number of pre-clinical and clinical applications for microRNA cancer therapeutics. This is promising, especially in the setting of rare cancers.

miR-30d is related to asbestos exposure and inhibits migration and invasion in NCI-H2452 cells

Pleural malignant mesothelioma (MM) is a highly aggressive tumor that is typically related to asbestos exposure and has a latency of 20-60 years. Several microRNA contribute to MM initiation and progression, but the mechanisms are not clear. Here, we found that miR-30d is downregulated in the pleural MM cell line NCI-H2452, in the plasma of asbestos-exposed individuals, and in asbestos-exposed mesothelial cells. Furthermore, we investigated the influence of the overexpression of miR-30d in pleural MM cells. We demonstrated that miR-30d overexpression could suppress pleural MM cell proliferation, migration, and invasion in vitro and could promote cell apoptosis but could not significantly influence cell cycle. The mRNA and protein expression of vimentin and TWIST1 decreased, and the mRNA expression of CDH1 increased in NCI-H2452 cells that overexpressed miR-30d. We therefore conclude that miR-30d is related to asbestos exposure and inhibits cell migration and invasion by regulating the epithelial-mesenchymal transition in NCI-H2452 cells.

Targeting microRNA to improve diagnostic and therapeutic approaches for malignant mesothelioma

Malignant mesothelioma is an aggressive and often fatal cancer associated with asbestos exposure. The disease originates in the mesothelial lining of the serosal cavities, most commonly affecting the pleura. Survival rates are low as diagnosis often occurs at an advanced stage and current treatments are limited. Identifying new diagnostic and therapeutic targets for mesothelioma remains a priority, particularly for the new wave of victims exposed to asbestos through do-it-yourself renovations and in countries where asbestos is still mined and used. Recent advances have demonstrated a biological role for the small but powerful gene regulators microRNA (miRNA) in mesothelioma. A number of potential therapeutic targets have been identified. MiRNA have also become popular as potential biomarkers for mesothelioma due to their stable expression in bodily fluid and tissues. In this review, we highlight the current challenges associated with the diagnosis and treatment of mesothelioma and discuss how targeting miRNA may improve diagnostic, prognostic and therapeutic approaches.

Clinical staging of malignant pleural mesothelioma: current perspectives

Malignant pleural mesothelioma (MPM) is a disease with limited therapeutic options, the management of which is still controversial. Diagnosis is usually made by thoracoscopy, which allows multiple biopsies with histological subtyping and is indicated for staging purposes in surgical candidates. The recommended and recently updated classification for clinical use is the TNM staging system established by the International Mesothelioma Interest Group and the International Association for the Study of Lung Cancer, which is based mainly on surgical and pathological variables, as well as on cross-sectional imaging. Contrast-enhanced computed tomography is the primary imaging procedure. Currently, the most used measurement system for MPM is the modified Response Evaluation Criteria in Solid Tumors (RECIST) method, which is based on unidimensional measurements of tumor thickness perpendicular to the chest wall or mediastinum. Magnetic resonance imaging and functional imaging with ¹⁸F-fluoro-2-deoxy-D-glucose positron-emission tomography can provide additional staging information in selected cases, although the usefulness of this method is limited in patients undergoing pleurodesis. Molecular reclassification of MPM and gene expression or miRNA prognostic models have the potential to improve prognostication and patient selection for a proper treatment algorithm; however, they await prospective validation to be introduced in clinical practice.

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

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

MicroRNA Expression in Malignant Pleural Mesothelioma and Asbestosis: A Pilot Study

Background

The identification of diagnostic/prognostic biomarkers for asbestos-related diseases is relevant for early diagnosis and patient survival and may contribute to understanding the molecular mechanisms underlying the disease development and progression.

Aims

To identify a pattern of miRNAs as possible diagnostic biomarkers for patients with malignant pleural mesothelioma (MPM) and asbestosis (ASB) and as prognostic biomarkers for MPM patients.

Methods

miRNA-16, miRNA-17, miRNA-126, and miRNA-486 were quantified in plasma and formalin-fixed paraffin-embedded samples to evaluate their diagnostic and prognostic roles compared to patients with other noncancerous pulmonary diseases (controls). Results. The expression of all the miRNAs was significantly lower in patients with MPM and ASB than that in controls. miRNA-16, miRNA-17, and miRNA-486 in plasma and tissue of MPM patients were significantly correlated. Furthermore, the expression of miRNA-16 in plasma and tissue, and miRNA-486 only in tissue, was positively related with cumulative survival in MPM patients.

Conclusions

All the miRNA levels were decreased in patients with MPM or ASB, supporting the role of circulating miRNAs as a potential tool for diseases associated with exposure to asbestos fibers. miRNA-16 was directly related to MPM patient prognosis, suggesting its possible use as a prognostic marker in MPM patients.

Deregulation of miRNAs in malignant pleural mesothelioma is associated with prognosis and suggests an alteration of cell metabolism

Malignant pleural mesothelioma (MPM) is an aggressive human cancer and miRNAs can play a key role for this disease. In order to broaden the knowledge in this field, the miRNA expression was investigated in a large series of MPM to discover new pathways helpful in diagnosis, prognosis and therapy. We employed nanoString nCounter system for miRNA profiling on 105 MPM samples and 10 healthy pleura. The analysis was followed by the validation of the most significantly deregulated miRNAs by RT-qPCR in an independent sample set. We identified 63 miRNAs deregulated in a statistically significant way. MiR-185, miR-197, and miR-299 were confirmed differentially expressed, after validation study. In addition, the results of the microarray analysis corroborated previous findings concerning miR-15b-5p, miR-126-3p, and miR-145-5p. Kaplan-Meier curves were used to explore the association between miRNA expression and overall survival (OS) and identified a 2-miRNA prognostic signature (Let-7c-5p and miR-151a-5p) related to hypoxia and energy metabolism respectively. In silico analyses with DIANA-microT-CDS highlighted 5 putative targets in common between two miRNAs. With the present work we showed that the pattern of miRNAs expression is highly deregulated in MPM and that a 2-miRNA signature can be a new useful tool for prognosis in MPM.

Diagnostic and prognostic biomarkers for malignant mesothelioma: an update

Malignant mesothelioma (MM) is an aggressive and lethal cancer, mostly related to inhalation of asbestos and erionite fibers. MM is associated with poor prognosis, because of its resistance to current therapies, even if higher survival occurs in patients diagnosed and treated when at stage I of the disease. However, these do not exceed 5% of the total number of cases, due to the inadequacy of the existing biomarkers for early and accurate diagnosis. Therefore, new effective biomarkers are needed for MM detection at earlier stages and to develop tailored therapies. Here we review the most promising biomarkers in MM to date: mesothelin, soluble mesothelin-related peptides (SMRPs), megakaryocyte potentiating factor (MPF), Osteopontin (OPN), Fibulin-3, high mobility group B1 (HMGB1), microRNAs (miRNAs), multiplex protein signatures. The validation of these biomarkers will allow their use, alone or in combination, for monitoring individuals from cohorts at risk of MM and attaining early detection of MM that is instrumental in improving patient survival.

Posttranscriptional Regulation Controls Calretinin Expression in Malignant Pleural Mesothelioma

Calretinin (CALB2) is a diagnostic and prognostic marker in malignant pleural mesothelioma (MPM). We previously reported that calretinin expression is regulated at the mRNA level. The presence of a medium-sized (573 nucleotide) 3' untranslated region (3'UTR) predicted to contain binding sites for miR-30a/b/c/d/e and miR-9 as well as an adenine/uridine-rich element (ARE) in all three transcripts arising from the CALB2 gene, suggests that calretinin expression is regulated via posttranscriptional mechanisms. Our aim was to investigate the role of the CALB2-3'UTR in the posttranscriptional regulation of calretinin expression in MPM. CALB2-3'UTR was inserted downstream of the luciferase reporter gene using pmiRGLO vector and reporter expression was determined after transfection into MPM cells. Targeted mutagenesis was used to generate variants harboring mutated miR-30 family and ARE binding sites. Electrophoretic mobility shift assay was used to test for the presence of ARE binding proteins. CALB2-3'UTR significantly decreased luciferase activity in MPM cells. Analysis of mutation in the ARE site revealed a further destabilization of the reporter and human antigen R (HuR) binding to the ARE sequence was detected. The mutation of two miR-30 binding sites abolished CALB2-3'UTR destabilization effect; a transient delivery of miR-30e-5p mimics or anti-miR into MPM cells resulted in a significant decrease/increase of the luciferase reporter expression and calretinin protein, respectively. Moreover, overexpression of CALB2-3'UTR quenched the effect of miR-30e-5p mimics on calretinin protein levels, possibly by sequestering the mimics, thereby suggesting a competitive endogenous RNA network. Finally, by data mining we observed that expression of miR-30e-5p was negatively correlated with the calretinin expression in a cohort of MPM patient samples. Our data show the role of (1) adenine-uridine (AU)-binding proteins in calretinin stabilization and (2) miR-30e-5p in the posttranscriptional negative regulation of calretinin expression via interaction with its 3'UTR. Furthermore, our study demonstrates a possible physiological role of calretinin's alternatively spliced transcripts.

Plasmatic extracellular vesicle microRNAs in malignant pleural mesothelioma and asbestos-exposed subjects suggest a 2-miRNA signature as potential biomarker of disease

Background

Malignant Pleural Mesothelioma (MPM) is an aggressive cancer mainly caused by asbestos exposure and refractory to current therapies. Specific diagnostic markers for early MPM diagnosis are needed. Changes in miRNA expression have been implicated in several diseases and cancers, including MPM. We examined if a specific miRNA signature in plasmatic extracellular vesicles (EV) may help to discriminate between malignant pleural mesothelioma patients (MPM) and subjects with Past Asbestos Exposure (PAE).

Methodology/Principal findings

We investigated 23 MPM patients and 19 cancer-free subjects with past asbestos exposure (PAE). We screened 754 miRNAs in plasmatic EVs by OpenArray and found 55 differential miRNAs using logistic regression models adjusted for age, sex, BMI, and smoking. Among the top-20 differential miRNAs chosen for validation by Real time PCR, 16 were confirmed. Using receiver operating characteristic (ROC) curve analysis, the most discriminating miRNA combination was given by miR-103a-3p + miR-30e-3p, which generated an AUC of 0.942 (95% CI 0.87–1.00), with a sensitivity of 95.5% and a specificity of 80.0%. Using multivariate Cox regression analysis including gender, age, BMI and smoking we found a Hazard Ratio for miR-103a-3p above the median of 0.37 (95%CI 0.13–1.13) and of 0.51 (95%CI 0.17–1.52) for miR-30e-3p.

Conclusions

This study suggests EV-associated miR-103a-3p and miR-30e-3p are able to discriminate MPM from PAE subjects. Larger and prospective studies are needed to confirm these two-miRNA signature alone or in combination with other biomarkers as diagnostic tools for MPM.