MicroRNA-31 Regulates Chemosensitivity in Malignant Pleural Mesothelioma

Malignant Pleural Mesothelioma: From Pathophysiology to Innovative Actionable Targets

BACKGROUND

Pleural mesothelioma (PM) is a rare and highly aggressive cancer which arises from mesothelial layer and primarily linked to asbestos exposure, genetic predispositions, and specific mutations. Despite current treatment modalities, including chemotherapy, antiangiogenic therapy and more recently immunotherapy, the prognosis remains dismal, with a median survival time of 6-18 months.

OBJECTIVES

The urgent need for novel therapeutic strategies has prompted research into molecular targets and precision medicine approaches. At present, many potential targets for therapeutic strategies have been identified, and emerging clinical trials are demonstrating certain clinical efficacy.

METHODS

This review examines advancements in understanding PM's genetic and epigenetic landscape, signaling pathways, and promising therapeutic targets.

RESULTS

We also discuss the results of recent clinical trials and their potential implications for future treatment paradigms.

MicroRNAs and lysosomal membrane proteins: Critical interactions in tumor progression and therapy

Cancer development is influenced by genetic and epigenetic variations, with the interactions between microRNAs (miRNAs) and lysosomal membrane proteins (LMPs) representing key regulatory mechanisms with potential as therapeutic targets. This review focuses on the complex regulatory mechanisms of miRNAs and LMPs in tumor progression, specifically highlighting their roles in tumor suppression, tumor promotion, tumor therapy, and drug resistance and their future application in treatment strategies. Overall, the interactions of LMPs with miRNAs have critical roles in tumor regulation, and studies of these interactions will further highlight their molecular contributions to cancer development.

An Overview of Cellular and Molecular Determinants Regulating Chemoresistance in Pleural Mesothelioma

Malignant pleural mesothelioma (PM) is a highly aggressive disease of the lung pleura associated with poor prognosis. Despite advances in improving the clinical management of this malignancy, there is no effective chemotherapy for refractory or relapsing PM. The acquisition of resistance to standard and targeted therapy in this disease is a foremost concern; therefore, a deeper understanding of the complex factors surrounding the emergence of drug resistance is deemed necessary. In this review, we will present broad insights into various cellular and molecular concepts, accounting for the recalcitrance of PM to chemotherapy, including signaling networks regulating drug tolerance, drug resistance-associated proteins, genes, and miRNAs, as well as the critical role of cancer stem cells. Identification of the biological determinants and their associated mechanisms may provide a framework for the development of appropriate treatment.

miRNA-503 inhibition exerts anticancer effects and reduces tumor growth in mesothelioma

BACKGROUND

Malignant mesothelioma (MM) is a rare and aggressive form of cancer that affects the mesothelial surfaces, associated with exposure to asbestos fibres. To date, no cure is available for MM and therapeutically approved treatments are based on the use of platinum compounds often used in combination with other drugs. We have previously analysed the efficacy of a cisplatin/piroxicam (CDDP/P) combined treatment showing that this treatment was able to reduce in vivo tumor growth. Several studies reported that platinum-drug sensitivity in cancer is connected to modulation of the expression of non-coding RNAs. In this study we analysed if the CDDP/P treatment was able to modulate miRNAs expression in MM.

METHODS

miRNA sequencing performed on MSTO-211 H cells treated with CDDP with CDDP/P led us to identify miRNA-503 - downregulated by CDDP/P - as a novel miRNA that acts as an oncomiR in MM. The effect of miRNA-503 inhibition was evaluated in vitro in mesothelioma cells analysing apoptosis induction and reduction of cancer properties. Inhibition of miR-503 expression in vivo, was analysed in ectopic mouse model of MM by using LNP encapsulating anti-mir-503 and miR-503 expression was evaluated in human MM samples.

RESULTS

In vitro and in vivo analysis confirmed miR-503 acts as oncogene in MM since its inhibition was able to reduce cell cancer properties and tumor growth in ectopic mouse model of MM. Its expression was found upregulated in human MM patients compared to normal pleura. Bioinformatic analysis indicated BTG1, CCNG1, EDG1, and TIMP2 as putative target genes of miRNA-503. These genes showed an opposite expression compared to miR-503 levels both in cells and in MM samples. Finally, microarray analysis indicated that miR-503 inhibition affected the expression of the well-known MM biomarkers: CXCL8, SERPINE1 and Osteopontin.

CONCLUSIONS

Our study is the first reporting an oncomiR role for miR-503 in MM and suggests that its inactivation could have a clinical value in MM patients. This study reveals that miRNA-503 acts as an oncomiR in MM suggesting that its inhibition, through LNP delivery, has the potential to be considered as a novel therapeutic strategy in MM.

Dual role of microRNA-31 in human cancers; focusing on cancer pathogenesis and signaling pathways

Widespread changes in the expression of microRNAs in cancer result in abnormal gene expression for the miRNAs that control those genes, which in turn causes changes to entire molecular networks and pathways. The frequently altered miR-31, which is found in a wide range of cancers, is one cancer-related miRNA that is particularly intriguing. MiR-31 has a very complicated set of biological functions, and depending on the type of tumor, it may act both as a tumor suppressor and an oncogene. The endogenous expression levels of miR-31 appear to be a key determinant of the phenotype brought on by aberrant expression. Varied expression levels of miR-31 could affect cell growth, metastasis, drug resistance, and other process by several mechanisms like targeting BRCA1-associated protein-1 (BAP1), large tumor suppressor kinase 1 (LATS1) and protein phosphatase 2 (PP2A). This review highlights the current understanding of the genes that miR-31 targets while summarizing the complex expression patterns of miR-31 in human cancers and the diverse phenotypes brought on by altered miR-31 expression.

Impact of Molecular Profiling on Therapy Management in Breast Cancer

Breast cancer (BC) remains the most prevalent cancer among women and the leading cause of cancer-related mortality worldwide. The heterogeneity of BC in terms of histopathological features, genetic polymorphisms, and response to therapies necessitates a personalized approach to treatment. This review focuses on the impact of molecular profiling on therapy management in breast cancer, emphasizing recent advancements in next-generation sequencing (NGS) and liquid biopsies. These technologies enable the identification of specific molecular subtypes and the detection of blood-based biomarkers such as circulating tumor cells (CTCs), circulating tumor DNA (ctDNA), and tumor-educated platelets (TEPs). The integration of molecular profiling with traditional clinical and pathological data allows for more tailored and effective treatment strategies, improving patient outcomes. This review also discusses the current challenges and prospects of implementing personalized cancer therapy, highlighting the potential of molecular profiling to revolutionize BC management through more precise prognostic and therapeutic interventions.

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.

Next-generation nanomaterials: advancing ocular anti-inflammatory drug therapy

Ophthalmic inflammatory diseases, including conjunctivitis, keratitis, uveitis, scleritis, and related conditions, pose considerable challenges to effective management and treatment. This review article investigates the potential of advanced nanomaterials in revolutionizing ocular anti-inflammatory drug interventions. By conducting an exhaustive analysis of recent advancements and assessing the potential benefits and limitations, this review aims to identify promising avenues for future research and clinical applications. The review commences with a detailed exploration of various nanomaterial categories, such as liposomes, dendrimers, nanoparticles (NPs), and hydrogels, emphasizing their unique properties and capabilities for accurate drug delivery. Subsequently, we explore the etiology and pathophysiology of ophthalmic inflammatory disorders, highlighting the urgent necessity for innovative therapeutic strategies and examining recent preclinical and clinical investigations employing nanomaterial-based drug delivery systems. We discuss the advantages of these cutting-edge systems, such as biocompatibility, bioavailability, controlled release, and targeted delivery, alongside potential challenges, which encompass immunogenicity, toxicity, and regulatory hurdles. Furthermore, we emphasize the significance of interdisciplinary collaborations among material scientists, pharmacologists, and clinicians in expediting the translation of these breakthroughs from laboratory environments to clinical practice. In summary, this review accentuates the remarkable potential of advanced nanomaterials in redefining ocular anti-inflammatory drug therapy. We fervently support continued research and development in this rapidly evolving field to overcome existing barriers and improve patient outcomes for ophthalmic inflammatory disorders.

Matrigel-based organoid culture of malignant mesothelioma reproduces cisplatin sensitivity through CTR1

Organoids are a three-dimensional (3D) culture system that simulate actual organs. Therefore, tumor organoids are expected to predict precise response to chemotherapy in patients. However, to date, few studies have studied the drug responses in organoids of malignant mesothelioma (MM). The poor prognosis of MM emphasizes the importance of establishing a protocol for generating MM-organoid for research and clinical use. Here, we established murine MM organoids from p53^+/- or wild-type C57BL/6 strain by intraperitoneal injection either with crocidolite or carbon nanotube. Established MM-organoids proliferated in Matrigel as spheroids. Subcutaneous injection assays revealed that the MM-organoids mimicked actual tissue architecture and maintained the original histological features of the primary MM. RNA sequencing and pathway analyses revealed that the significant expressional differences between the 2D- and 3D-culture systems were observed in receptor tyrosine kinases, including IGF1R and EGFR, glycosylation and cholesterol/steroid metabolism. MM-organoids exhibited a more sensitive response to cisplatin through stable plasma membrane localization of a major cisplatin transporter, copper transporter 1/Slc31A1 (Ctr1) in comparison to 2D-cultures, presumably through glycosylation and lipidation. The Matrigel culture system facilitated the localization of CTR1 on the plasma membrane, which simulated the original MMs and the subcutaneous xenografts. These results suggest that the newly developed protocol for MM-organoids is useful to study strategies to overcome chemotherapy resistance to cisplatin.

The Role of microRNAs in Regulating Cancer Cell Response to Oxaliplatin-Containing Regimens

Oxaliplatin (cyclohexane-1,2-diamine; oxalate; platinum [2+]) is a third-generation chemotherapeutic drug with anticancer effects. Oxaliplatin has a role in the treatment of several cancers. It is one of the few drugs which can eliminate the neoplastic cells of colorectal cancer. Also, it has an influential role in breast cancer, lung cancer, bladder cancer, prostate cancer, and gastric cancer. Although oxaliplatin has many beneficial effects in cancer treatment, resistance to this drug is in the way to cure neoplastic cells and reduce treatment efficacy. microRNAs are a subtype of small noncoding RNAs with ∼22 nucleotides that exist among species. They have diverse roles in physiological processes, including cellular proliferation and cell death. Moreover, miRNAs have essential roles in resistance to cancer treatment and can strengthen sensitivity to chemotherapeutic drugs and regimens. In colorectal cancer, the co-treatment of oxaliplatin with anti-miR-19a can partially reverse the oxaliplatin resistance through the upregulation of phosphatase and tensin homolog (PTEN). Moreover, by preventing the spread of gastric cancer cells and downregulating glypican-3 (GPC3), MiR-4510 may modify immunosuppressive signals in the tumor microenvironment. Treatment with oxaliplatin may develop into a specialized therapeutic drug for patients with miR-4510 inhibition and glypican-3-expressing gastric cancer. Eventually, miR-122 upregulation or Wnt/β-catenin signaling suppression boosted the death of HCC cells and made them more sensitive to oxaliplatin. Herein, we have reviewed the role of microRNAs in regulating cancer cells' response to oxaliplatin, with particular attention to gastrointestinal cancers. We also discussed the role of these noncoding RNAs in the pathophysiology of oxaliplatin-induced neuropathic pain.

Exploring MicroRNA and Exosome Involvement in Malignant Pleural Mesothelioma Drug Response

Malignant pleural mesothelioma (MPM) is a deadly thoracic malignancy and existing treatment options are limited. Chemotherapy remains the most widely used first-line treatment regimen for patients with unresectable MPM, but is hampered by drug resistance issues. The current study demonstrated a modest enhancement of MPM cell sensitivity to chemotherapy drug treatment following microRNA (miRNA) transfection in MPM cell lines, albeit not for all tested miRNAs. This effect was more pronounced for FAK (PND-1186) small molecule inhibitor treatment; consistent with previously published data. We previously established that MPM response to survivin (YM155) small molecule inhibitor treatment is unrelated to basal survivin expression. Here, we showed that MPM response to YM155 treatment is enhanced following miRNA transfection of YM155-resistant MPM cells. We determined that YM155-resistant MPM cells secrete a higher level of exosomes in comparison to YM155-sensitive MPM cells. Despite this, an exosome inhibitor (GW4896) did not enhance MPM cell sensitivity to YM155. Additionally, our study showed no evidence of a correlation between the mRNA expression of inhibitor of apoptosis (IAP) gene family members and MPM cell sensitivity to YM155. However, two drug transporter genes, ABCA6 and ABCA10, were upregulated in the MPM cell lines and correlated with poor sensitivity to YM155.

The Influence of MicroRNA-31 on Oxidative Stress and Radiosensitivity in Pancreatic Ductal Adenocarcinoma

Radioresistance remains a significant challenge in treating pancreatic ductal adenocarcinoma (PDAC), contributing to the poor survival rates of this cancer. MicroRNAs (miRs) are small non-coding RNA molecules that may play an essential role in regulating radioresistance by altering the levels of oxidative stress. In this study, we investigated the role and potential mechanisms linking miR-31 to PDAC radioresistance. A pCMV-miR vector containing a miR-31 mimic was stably expressed into a miR-31-deficient PDAC cell line, BxPC-3. Additionally, a pmiRZip lentivector suppressing miR-31 was stably expressed in a miR-31 abundant PDAC cell line, Panc-1. Clonogenic assays were conducted to explore the role of miR-31 manipulation on radiosensitivity. Fluorometric ROS assays were performed to quantify ROS levels. The expression of potential miR-31 targets was measured by Western blot analysis. It was found that the manipulation of miR-31 altered the radiosensitivity in PDAC cells by regulating oxidative stress. Using online bioinformatics tools, we identified the 3'UTR of GPx8 as a predicted target of miR-31. Our study demonstrates, for the first time, that manipulating miR-31 alters GPx8 expression, regulating ROS detoxification and promoting either a radioresistant or radiosensitive phenotype. MiR-31 may represent a promising therapeutic target for altering radiosensitivity in PDAC cells.

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.

Comprehensive analysis of negatively correlated miRNA-mRNA regulatory pairs associated with microsatellite instability in colorectal cancer

BACKGROUND: Several studies have demonstrated that microRNAs (miRNAs) and target mRNAs are associated with different frequencies of microsatellite instability. OBJECTIVE: The study aimed to elucidate the profiles of miRNAs and target mRNAs expression and their associations with the phenotypic hallmarks of microsatellite instability in colorectal cancers (CRC) by integrating transcriptomic, immunophenotype, methylation, mutation, and survival data. METHODS: Differentially expressed miRNAs (DEmiRNAs) and mRNAs (DEmRNAs) were screened out and then the miRNA-mRNA regulatory pairs were identified through two databases. We verified that the expression levels were detected in 40 microsatellite instable (MSI) and 40 microsatellite stable (MSS) CRC samples and used the logistic regression and the Cox regression method to evaluate the diagnostic and prognostic value of negative regulatory pairs respectively. RESULTS: The best diagnostic model that combines miR-31-5p, PLAGL2, miR-361-5p, and RAB27B, which were associated with immune microenvironment, tumor mutation burden (TMB), and overall DNA methylation, could significantly predict microsatellite instability in colon tissues. MiR-31-5p and RAB27B could also predict the overall survival of MSS CRCs. CONCLUSION: This study generated a predictive model of the combination of miRNAs and mRNAs to distinguish MSI versus MSS CRCs and elaborated their potential molecular mechanisms and biological functions.

BRCA-associated protein 1 (BAP1) and miR-31 combination predicts outcomes in epithelioid malignant pleural mesothelioma

Background

Malignant pleural mesothelioma (MPM) is an aggressive disease, with few available treatment options. Identification of novel prognostic and predictive biomarkers is a priority. In MPM patients, BRCA-associated protein 1 (BAP1) alterations are detected in about 60% of cases and miR-31 seems to be involved in BAP1 regulation at post-transcriptional level. The aim of this study was to evaluate the interaction between BAP1 and miR-31 in MPM and their prognostic role in MPM.

Methods

The expression of BAP1 and miR-31 was analyzed in tissues of 55 MPM patients treated with first-line chemotherapy. Overall survival (OS) and progression-free survival (PFS) were assessed by Kaplan-Meier method and Log-rank test was used to investigate differences among subgroups. Multivariate Cox regression analysis was used to evaluate independent predictors of survival.

Results

In the whole cohort, loss of BAP1 was associated with a significant improvement in OS, but not in PFS. Lower miR-31 levels were detected in epithelioid MPM (e-MPM) compared to the non-epithelioid subtypes and resulted associated with BAP1 loss. By looking at the e-MPM subgroup, loss of BAP1 was not able to predict clinical outcome. Conversely, miR-31 levels were significantly associated with PFS (P=0.028), but not with OS (P=0.059). By combining the two biomarkers, e-MPM patients with BAP1 loss/low miR-31 levels showed a better prognosis compared to the ones with BAP1 retained/high miR-31 levels (median OS 22.6 vs. 17.0 months, P=0.017 and median PFS 8.7 vs. 5.1 months, P=0.020). The BAP1 and miR-31 combination was confirmed at multivariate analysis as an independent prognostic factor for e-MPM patients.

Conclusions

In this preliminary study, we found that the prognostic stratification of e-MPM patients may be improved by simultaneously assessing of BAP1 status and miR-31 levels. The two-biomarker score is useful to identify a subgroup of e-MPM tumors characterized by BAP1 retained and high miR-31 levels with worse clinical outcome.

HSD17B6 downregulation predicts poor prognosis and drives tumor progression via activating Akt signaling pathway in lung adenocarcinoma

Lung adenocarcinoma is one of the most frequent tumor subtypes, involving changes in a variety of oncogenes and tumor suppressor genes. Hydroxysteroid 17-Beta Dehydrogenase 6 (HSD17B6) could synthetize dihydrotestosterone, abnormal levels of which are associated with progression of multiple tumors. Previously, we showed that HSD17B6 inhibits malignant progression of hepatocellular carcinoma. However, the mechanisms underlying inhibiting tumor development by HSD17B6 are not clear. Moreover, its role in lung adenocarcinoma (LUAD) is yet unknown. Here, we investigated its expression profile and biological functions in LUAD. Analysis of data from the LUAD datasets of TCGA, CPTAC, Oncomine, and GEO revealed that HSD17B6 mRNA and protein expression was frequently lower in LUAD than in non-neoplastic lung tissues, and its low expression correlated significantly with advanced tumor stage, large tumor size, poor tumor differentiation, high tumor grade, smoking, and poor prognosis in LUAD. In addition, its expression was negatively regulated by miR-31-5p in LUAD. HSD17B6 suppressed LUAD cell proliferation, migration, invasion, epithelial-mesenchymal transition (EMT), and radioresistance. Furthermore, HSD17B6 overexpression in LUAD cell lines enhanced PTEN expression and inhibited AKT phosphorylation, inactivating downstream oncogenes like GSK3β, β-catenin, and Cyclin-D independent of dihydrotestosterone, revealing an underlying antitumor mechanism of HSD17B6 in LUAD. Our findings indicate that HSD17B6 may function as a tumor suppressor in LUAD and could be a promising prognostic indicator for LUAD patients, especially for those receiving radiotherapy.

MicroRNAs as a clue to overcome breast cancer treatment resistance

Breast cancer is the most frequent cancer in women worldwide. Despite the improvement in diagnosis and treatments, the rates of cancer relapse and resistance to therapies remain higher than desirable. Alterations in microRNAs have been linked to changes in critical processes related to cancer development and progression. Their involvement in resistance or sensitivity to breast cancer treatments has been documented by different in vivo and in vitro experiments. The most significant microRNAs implicated in modulating resistance to breast cancer therapies are summarized in this review. Resistance to therapy has been linked to cellular processes such as cell cycle, apoptosis, epithelial-to-mesenchymal transition, stemness phenotype, or receptor signaling pathways, and the role of microRNAs in their regulation has already been described. The modulation of specific microRNAs may modify treatment response and improve survival rates and cancer patients' quality of life. As a result, a greater understanding of microRNAs, their targets, and the signaling pathways through which they act is needed. This information could be useful to design new therapeutic strategies, to reduce resistance to the available treatments, and to open the door to possible new clinical approaches.

Involvement of the M-CSF/IL-34/CSF-1R pathway in malignant pleural mesothelioma

Background

Malignant pleural mesothelioma (MPM) is a rare and aggressive cancer related to asbestos exposure. The tumor microenvironment content, particularly the presence of macrophages, was described as crucial for the development of the disease. This work aimed at studying the involvement of the M-CSF (CSF-1)/IL-34/CSF-1R pathway in the formation of macrophages in MPM, using samples from patients.

Methods

Pleural effusions (PEs), frozen tumors, primary MPM cells and MPM cell lines used in this study belong to biocollections associated with clinical databases. Cytokine expressions were studied using real-time PCR and ELISA. The Cancer Genome Atlas database was used to confirm our results on an independent cohort. An original three-dimensional (3D) coculture model including MPM cells, monocytes from healthy donors and a tumor antigen-specific cytotoxic CD8 T cell clone was used.

Results

We observed that high interleukin (IL)-34 levels in PE were significantly associated with a shorter survival of patients. In tumors, expression of CSF1 was correlated with ‘M2-like macrophages’ markers, whereas this was not the case with IL34 expression, suggesting two distinct modes of action of these cytokines. Expression of IL34 was higher in MPM cells compared with primary mesothelial cells. Particularly, high expression of IL34 was observed in MPM cells with an alteration of CDKN2A. Finally, using 3D coculture model, we demonstrated the direct involvement of MPM cells in the formation of immunosuppressive macrophages, through activation of the colony stimulating factor-1 receptor (CSF1-R) pathway, causing the inhibition of cytotoxicity of tumor antigen-specific CD8⁺ T cells.

Conclusions

The M-CSF/IL-34/CSF-1R pathway seems strongly implicated in MPM and could constitute a therapeutic target to act on immunosuppression and to support immunotherapeutic strategies.

Alterations in BAP1 Are Associated with Cisplatin Resistance through Inhibition of Apoptosis in Malignant Pleural Mesothelioma

PURPOSE

The clinical standard treatment for patients with malignant pleural mesothelioma (MPM) includes a cisplatin-based chemotherapy, leading to reduction of tumor size in only a minority of patients. Predicting response to chemotherapy in patients with MPM by using a genetic marker would, therefore, enable patient stratification.

EXPERIMENTAL DESIGN

In this retrospective biomarker study, eligible patients had resectable MPM, measurable disease, and available primary MPM tissue. All patients underwent first-line treatment with cisplatin and pemetrexed, followed by surgery. Thorough molecular analysis was performed (whole-exome and targeted deep sequencing, and copy-number analyses), and also mechanistic in vitro data (viability assays, Western blots, and immunoprecipitation) using mesothelioma cell lines with and without siRNA-mediated BRCA1-associated protein 1 (BAP1) knockdown were provided.

RESULTS

In a training cohort of patients with MPM (n = 28), mutations or deletions of BAP1 each predicted resistance to chemotherapy in patients with primary MPM. The negative predictive value of BAP1 loss in patients with MPM was confirmed by amplicon sequencing and copy-number array technology in an independent test cohort (n = 39). Preliminary mechanistic studies using siRNA-based knockdown of BAP1 in MPM cell culture models along with immunoprecipitation assays confirmed chemoresistance in vitro, possibly through inhibition of apoptosis and transcriptional regulation of the BAP1/HCF1/E2F1 axis.

CONCLUSIONS

Alterations in BAP1 in MPM were a negative predictor for response to chemotherapy and could possibly be used as a companion biomarker for treatment decision.

Impact of metallothionein-knockdown on cisplatin resistance in malignant pleural mesothelioma

Malignant pleural mesothelioma (MPM) is a rare, but aggressive tumor with dismal prognosis. Platinum-based chemotherapy is regularly used as part of multimodality therapy. The expression of metallothioneins (MT) has been identified as a reason for cisplatin resistance, which often leads to early therapy failure or relapse. Thus, knockdown of MT expression may improve response to cisplatin treatment. The MT gene- and protein expression of the MPM-cell lines MSTO-211H, NCI-H2052 and NCI-H2452 and the human fibroblast cell line MRC-5, as well as their sensitivity to cisplatin treatment have been evaluated. Knockdown of MT1A, 1B and 2A expression was induced by RNA interference. MT expression was measured using quantitative real-time PCR. An in vitro Assay based on enzyme activity was used to detect cell viability, necrosis and apoptosis before and after incubation with cisplatin. MT2A gene expression could be detected in all MPM cell lines, showing the highest expression in NCI-H2452 and NCI-H2052, whereas gene expression levels of MT1A and MT1B were low or absent. The immunohistochemically protein expression of MT-I/II reflect MT2A gene expression levels. Especially for MSTO-211H cell presenting low initial MT2A levels, a strong induction of MT2A expression could be observed during cisplatin treatment, indicating a cell line-specific and platin-dependent adaption mechanism. Additionally, a MT2A-dependent cellular evasion of apoptosis during cisplatin could be observed, leading to three different MT based phenotypes. MSTO-211H cells showed lower apoptosis rates at an increased expression level of MT2A after cisplatin treatment (from sixfold to fourfold). NCI-H2052 cells showed no changes in MT2A expression, while apoptosis rate is the highest (8-12-fold). NCI-H2452 cells showed neither changes in alteration rate of MT2A expression nor changes in apoptosis rates, indicating an MT2A-independent resistance mechanism. Knockdown of MT2A expression levels resulted in significantly induced apoptotic rates during cisplatin treatment with strongest induction of apoptosis in each of the MPM cell lines, but in different markedness. A therapeutic meaningful effect of MT2A knockdown and subsequent cisplatin treatment could be observed in MSTO-211H cells. The present study showed MT2A to be part of the underlying mechanism of cisplatin resistance in MPM. Especially in MSTO-211H cells we could demonstrate major effects by knockdown of MT2A expression, verifying our hypothesis of an MT driven resistance mechanism. We could prove the inhibition of MT2A as a powerful tool to boost response rates to cisplatin-based therapy in vitro. These data carry the potential to enhance the clinical outcome and management of MPM in the future.

Inhibition of miR-18a-3p reduces proliferation of mesothelioma cells and sensitizes them to cisplatin

Malignant pleural mesothelioma is a notorious human malignancy. Despite combination chemotherapy with cisplatin and pemetrexed, the majority of patients with advanced malignant pleural mesothelioma have a poor prognosis. MicroRNAs (miRNAs/miRs) are short non-coding RNAs that regulate various biological processes by binding to the 3'-untranslated region of target gene mRNAs and suppressing their expression. Since abnormal expression patterns of miRNAs are a common feature in human malignancies, a number of them have been researched as potential therapeutic targets. Our previous study demonstrated that microRNA-18a (miR-18a) is upregulated in mesothelioma cell lines compared with in non-neoplastic mesothelial tissues, but its function remains unclear. In the present study, miRNA inhibitor was transfected into mesothelioma cell lines and then analyzed various cellular functions. Mesothelioma cells transfected with the miR-18a inhibitor exhibited lower proliferation and migration rates compared with cells transfected with a negative control inhibitor in proliferation and wound scratch assays, respectively. Additionally, the present study revealed that downregulation of miR-18a increased mesothelioma cell apoptosis. In a chemosensitivity assay, transfection of the miR-18a inhibitor significantly increased the sensitivity of mesothelioma cells to cisplatin but not to pemetrexed. Therefore, miR-18a may be a potential therapeutic target for mesothelioma resistant to cisplatin.

Manipulating microRNAs for the Treatment of Malignant Pleural Mesothelioma: Past, Present and Future

microRNAs (miRNAs) are an important class of non-coding RNA that post-transcriptionally regulate the expression of most protein-coding genes. Their aberrant expression in tumors contributes to each of the hallmarks of cancer. In malignant pleural mesothelioma (MPM), in common with other tumor types, changes in miRNA expression are characterized by a global downregulation, although elevated levels of some miRNAs are also found. While an increasing number of miRNAs exhibit altered expression in MPM, relatively few have been functionally characterized. Of a growing number with tumor suppressor activity in vitro, miR-16, miR-193a, and miR-215 were also shown to have tumor suppressor activity in vivo. In the case of miR-16, the significant inhibitory effects on tumor growth following targeted delivery of miR-16-based mimics in a xenograft model was the basis for a successful phase I clinical trial. More recently overexpressed miRNAs with oncogenic activity have been described. Many of these changes in miRNA expression are related to the characteristic loss of tumor suppressor pathways in MPM tumors. In this review we will highlight the studies providing evidence for therapeutic effects of modulating microRNA levels in MPM, and discuss these results in the context of emerging approaches to miRNA-based therapy.

Tumour suppressor microRNAs contribute to drug resistance in malignant pleural mesothelioma by targeting anti-apoptotic pathways

Aim: Aberrant microRNA expression is a common event in cancer drug resistance, however its involvement in malignant pleural mesothelioma (MPM) drug resistance is largely unexplored. We aimed to investigate the contribution of microRNAs to the resistance to drugs commonly used in the treatment of MPM. Methods: Drug resistant MPM cell lines were generated by treatment with cisplatin, gemcitabine or vinorelbine. Expression of microRNAs was quantified using RT-qPCR. Apoptosis and drug sensitivity assays were carried out following transfection with microRNA mimics or BCL2 siRNAs combined with drugs. Results: Expression of miR-15a, miR-16 and miR-34a was downregulated in MPM cells with acquired drug resistance. Transfection with miR-15a or miR-16 mimics reversed the resistance to cisplatin, gemcitabine or vinorelbine, whereas miR-34a reversed cisplatin and vinorelbine resistance only. Similarly, in parental cell lines, miR-15a or miR-16 mimics sensitised cells to all drugs, whereas miR-34a increased response to cisplatin and vinorelbine. Increased microRNA expression increased drug-induced apoptosis and caused BCL2 mRNA and protein reduction. RNAi-mediated knockdown of BCL2 partly recapitulated the increase in drug sensitivity in cisplatin and vinorelbine treated cells. Conclusion: Drug-resistant MPM cell lines exhibited reduced expression of tumour suppressor microRNAs. Increasing tumour suppressor of microRNA expression sensitised both drug resistant and parental cell lines to chemotherapeutic agents, in part through targeting of BCL2. Taken together, these data suggest that miR-15a, miR-16 and miR-34a are involved in the acquired and intrinsic drug resistance phenotype of MPM cells.

MicroRNAs as Potential Biomarkers for Chemoresistance in Adenocarcinomas of the Esophagogastric Junction

Concerning adenocarcinomas of the esophagogastric junction, neoadjuvant chemotherapy is regularly implemented, but patients' response varies greatly, with some cases showing no therapeutic effect, being deemed as chemoresistant. Small, noncoding RNAs (miRNAs) have evolved as key players in biological processes, including malignant diseases, often promoting tumor growth and expansion. In addition, specific miRNAs have been implicated in the development of chemoresistance through evasion of apoptosis, cell cycle alterations, and drug target modification. We performed a retrospective study of 33 patients receiving neoadjuvant chemotherapy by measuring their miRNA expression profiles. Histologic tumor regression was evaluated using resection specimens, while miRNA profiles were prepared using preoperative biopsies without prior therapy. A preselected panel of 96 miRNAs, known to be of importance in various malignancies, was used to test for significant differences between responsive (chemosensitive) and nonresponsive (chemoresistant) cases. The cohort consisted of 12 nonresponsive and 21 responsive cases with the following 4 miRNAs differentially expressed between both the groups: hsa-let-7f-5p, hsa-miRNA-221-3p, hsa-miRNA-31-5p, and hsa-miRNA-191-5p. The former 3 showed upregulation in chemoresistant cases, while the latter showed upregulation in chemosensitive cases. In addition, significant correlation between high expression of hsa-miRNA-194-5p and prolonged survival could be demonstrated (p value <0.0001). In conclusion, we identified a panel of 3 miRNAs predicting chemoresistance and a single miRNA contributing to chemosensitivity. These miRNAs might function as prognostic biomarkers and enable clinicians to better predict the effect of one or more reliably select patients benefitting from (neoadjuvant) chemotherapy.

What can independent research for mesothelioma achieve to treat this orphan disease?

Introduction: Malignant pleural mesothelioma (MPM) is a rare neoplasm with a poor prognosis, as current therapies are ineffective. Despite the increased understanding of the molecular biology of mesothelioma, there is still a lack of drugs that dramatically enhance patient survival. Area Covered: This review discusses recent and complete clinical trials supported by the NIH, other U.S. Federal agencies, universities and organizations found on clinicaltrials.gov. Firstly, chemotherapy-based trials are described, followed by immunotherapy and multitargeted therapy. Then we introduce drug repositioning and the use of drug docking as tools to find new interesting molecules. Finally, we highlight potential molecular pathways that may play a role in mesothelioma biology and therapy. Expert Opinion: Numerous biases are present in the clinical trials due to a restricted number of cases, inappropriate endpoints and inaccurate stratification of patients which delay the finding of a treatment for MPM. The most crucial issue of independent research for MPM is the lack of more substantive funding to translate these findings to the clinical setting. However, this approach is not necessarily scientific given the low mutational load of mesothelioma relative to other cancers, and therefore patients need a more solid rationale to have a good chance of successful treatment.

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.

Co-delivery of miR-181a and melphalan by lipid nanoparticles for treatment of seeded retinoblastoma

Melphalan is an efficient chemotherapeutic agent that is currently used to treat retinoblastoma (Rb); however, the inherent risk of immunogenicity and the hazardous integration of this drug in healthy cells is inevitable. MicroRNAs are short non-coding single-stranded RNAs that affect a vast range of biological processes. Previously, we focused on the regulatory role of miR-181a during cancer development and progression. In this manuscript, 171 nm switchable lipid nanoparticles (LNP) co-delivered melphalan and miR-181a with encapsulation efficiencies of 93%. Encapsulation of melphalan in LNP significantly improved its therapeutic efficiency. Gene analysis shows that miR-181a decreases the expression of anti-proliferative gene MAPK1 and anti-apoptotic gene Bcl-2, but significantly increased the expression of pro-apoptotic gene BAX. Our results suggest that the two agents have a complementary effect in reducing the viability of cultured Rb cells (primary and cell line) and decreasing Rb cell counts in an in-vivo xenograft Rb model in rats. Our results suggest that the proposed co-delivery technique significantly increases the therapeutic impact, allows for lower administration of melphalan, and consequently, could minimize the cytotoxic side-effects of this drug.

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.

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.

MicroRNA-31-5p regulates chemosensitivity by preventing the nuclear location of PARP1 in hepatocellular carcinoma

BACKGROUND

MicroRNAs (miRNAs) posttranscriptionally regulate gene expression and thereby contribute to the modulation of numerous complex and disease-relevant cellular processes, including cell proliferation, cell motility, apoptosis and stress response. miRNA-31-5p is encoded on a genomic fragile site, 9p21.3, which is reportedly lost in many hepatocellular carcinoma (HCC) tumors. Based on previous findings, we hypothesized that miR-31-5p alters chemosensitivity and that miR-31-5p mimics may influence sensitivity to chemotherapeutics in HCC as well as in a variety of other cancers.

METHODS

MiR-31-5p and PARP1 in HCC tissues were tested by RT-PCR and histological analysis, respectively. Next, clonogenic assay and western blot were used to detect miR-31-5p and PARP1 to modulate sensitivity to OXA-based chemotherapy. The distribution of OXA in the nuclear and intracellular was detected by ICP-MS. Coimmunoprecipitation was used to characterize the protein-protein interaction between PARP1 and ABCB9. A xenograft nude mouse model was used to examine the in vivo effects of miR-31-5p.

RESULTS

Reintroduction of miR-31-5p into miR-31-5p-null Hep3B cells significantly enhanced clonogenic resistance to oxaliplatin. Although miR-31-5p re-expression increased chemoresistance, it paradoxically increased the relative intracellular accumulation of oxaliplatin. This effect was coupled with a significantly decreased intranuclear concentration of oxaliplatin by ICP-MS. miR-31-5p prevents the nuclear location of PARP1 detected by immunofluorescence, histological analysis and Western blotting analysis. We subsequently identified an indirect miR-31-5p-mediated upregulation of ABCB9, which is a transporter associated with drug accumulation in lysosomes, along with an increased uptake of oxaliplatin to lysosomes; these phenomena were associated with a downregulation of PARP1, a bipotential transcriptional regulator with multiple miR-31-5p binding sites. However, the indirect overexpression of ABCB9 promoted cellular chemosensitivity, suggesting that miR-31-5p promotes chemoresistance largely via an ABCB9-independent mechanism.

CONCLUSIONS

Overall, our data suggest that the loss of miR-31-5p from HCC tumors promotes chemosensitivity, and this knowledge may be prognostically beneficial in the context of therapeutic sensitivity.

LncRNA PVT1 regulates growth, migration, and invasion of bladder cancer by miR-31/ CDK1

PURPOSE

The aim of our study was to validate the sway of long noncoding RNA (lncRNA) plasmacytoma variant translocation 1 (PVT1) on the metabolism and growth of bladder cancer cells by microRNA-31 (miR-31)/cyclin-dependent kinase 1 ( CDK1).

METHODS

The Gene Expression Omnibus database was used for analyzing the differentially expressed lncRNA and messenger RNA (mRNA) in bladder cancer tissues, with the highly expressed lncRNA PVT1 and mRNA CDK1 screened out. The expression level of PVT1 was detected by quantitative reverse-transcription polymerase chain reaction, cell viability by Cell Counting Kit-8 assay, cell proliferation and scratch by 5-bromo-2'-deoxyuridine assay, cell migration and invasion by transwell assays, the expression level of CDK1 by immunohistochemistry and western blot analysis, transcription factor targeting by dual-luciferase assay, and the effect of PVT1 on bladder cancer growth by nude mice tumor formation experiment.

RESULTS

LncRNA PVT1 and mRNA CDK1 had a higher expression in bladder cancer cells than that in neighboring tissues. Activity, proliferation, colony formation, migration, and invasion of bladder cancer cell were noticeably reduced by the PVT1 inhibitor than that of control group. PVT1 and CDK1 have binding sites with miR-31. When miR-31 decreased, CDK1 mRNA and protein levels increased in vivo experiments in nude mice. When PVT1 was downregulated, the tumor size was significantly reduced and tumor proliferation was curbed. Immunohistochemistry showed that the positive rate of CDK1 and Ki-67 decreased and the expression of miR-31 increased after PVT1 was inhibited.

CONCLUSIONS

LncRNA PVT1 was overexpressed in bladder cancer cells, and it was downregulated miR-31 to enhance CDK1 expression and facilitate bladder cancer cells proliferation, migration, and invasion.

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.

MicroRNA-125a-5p enhances the sensitivity of esophageal squamous cell carcinoma cells to cisplatin by suppressing the activation of the STAT3 signaling pathway

Increasing evidence has demonstrated that microRNAs (miRNAs or miRs) play a variety of roles in tumor development, progression and chemosensitivity in a wide range of tumors. In this study, we found that miR-125a-5p exhibited a low expression in esophageal squamous cell carcinoma (ESCC) tissues and cells, and that its low expression was associated with higher tumor staging and shorter a survival time of patients with ESCC. Moreover, miR-125a-5p overexpression contributed to the suppression of cell proliferation, cell cycle arrest, cell apoptosis and a decrease in cell migratory and invasive abilities, whereas the downregulation of miR-125a-5p promoted cell proliferation, accelerated cell cycle progression, suppressed apoptosis and enhanced the migratory and invasive abilities of ESCC EC1 and TE1 cells, which may be tightly associated with the epithelial-mesenchymal transition (EMT) process in ESCC. Importantly, miR-125a-5p enhanced the cytotoxic effects of cisplatin on EC1 and TE1 cells, and co-treatment with miR-125a-5p and cisplatin significantly induced cell apoptosis and reduced the cell migratory and invasive abilities of EC1 and TE1 cells, coupled with an increase in the E-cadherin level and a decrease in the N-cadherin and Vimentin levels. Most notably, signal transducer and activator of transcription-3 (STAT3) was found to be a direct target of miR-125a-5p in ESCC cells, and miR-125a-5p overexpression significantly reduced the protein levels of t-STAT3, p-STAT3 and vascular endothelial growth factor (VEGF) in EC1 and TE1 cells. Furthermore, the combination of miR-125a-5p and cisplatin markedly inactivated the STAT3 signaling pathway; however, interleukin (IL)-6, a widely reported activator of the STAT3 signaling pathway, reversed the suppressive effects of miR-125a-5p/cisplatin in ESCC cells on the activation of the STAT3 signaling pathway. Of note, we found that IL-6 markedly reversed the altered cell phenotype mediated by the combination of miR-125a-5p and cisplatin in ESCC cells. These findings suggest that miR-125a-5p may play a pivotal role in the development and progression of ESCC, which may be achieved via the manipulation of the STAT3 signaling pathway.