A high-content morphological screen identifies novel microRNAs that regulate neuroblastoma cell differentiation

Restricting Colorectal Cancer Cell Metabolism with Metformin: An Integrated Transcriptomics Study

BACKGROUND

Metformin is a first-line therapy for type 2 diabetes as it disrupts cellular metabolism. Despite the association between metformin and lower cancer incidence, the anti-tumour activity of the drug in colorectal cancer (CRC) is incompletely understood. This study identifies underlying molecular mechanisms by which metformin slows colorectal cancer cell proliferation by investigating metformin-associated microRNA (miRNA) and target gene pairs implicated in signalling pathways.

METHODS

The present study analysed changes in miRNAs and the coding transcriptome in CRC cells treated with a sublethal dose of metformin, followed by the contextual validation of potential miRNA-target gene pairs.

RESULTS

Analyses of small RNA and transcriptome sequencing data revealed 104 miRNAs and 1221 mRNAs to be differentially expressed in CRC cells treated with metformin for 72 h. Interaction networks between differentially expressed miRNAs and putative target mRNAs were identified. Differentially expressed genes were mainly implicated in metabolism and signalling processes, such as the PI3K-Akt and MAPK/ERK pathways. Further validation of potential miRNA-target mRNA pairs revealed that metformin induced miR-2110 and miR-132-3p to target PIK3R3 and, consequently, regulate CRC cell proliferation, cell cycle progression and the PI3K-Akt signalling pathway. Metformin also induced miR-222-3p and miR-589-3p, which directly target STMN1 to inhibit CRC cell proliferation and cell cycle progression.

CONCLUSIONS

This study identified novel changes in the coding transcriptome and small non-coding RNAs associated with metformin treatment of CRC cells. Integration of these datasets highlighted underlying mechanisms by which metformin impedes cell proliferation in CRC. Importantly, it identified the post-transcriptional regulation of specific genes that impact both metabolism and cell proliferation.

Stable Dual miR-143 and miR-506 Upregulation Inhibits Proliferation and Cell Cycle Progression

The mainstays of lung cancer pathogenesis are cell cycle progression dysregulation, impaired apoptosis, and unregulated cell proliferation. While individual microRNA (miR) targeting or delivering is a promising approach that has been extensively studied, combination of miR targeting can enhance therapeutic efficacy and overcome limitations present in individual miR regulations. We previously reported on the use of a miR-143 and miR-506 combination via transient transfections against lung cancer. In this study, we evaluated the effect of miR-143 and miR-506 under stable deregulations in A549 lung cancer cells. We used lentiviral transductions to either up- or downregulate the two miRs individually or in combination. The cells were sorted and analyzed for miR deregulation via qPCR. We determined the miR deregulations' effects on the cell cycle, cell proliferation, cancer cell morphology, and cell motility. Compared to the individual miR deregulations, the combined miR upregulation demonstrated a miR-expression-dependent G2 cell cycle arrest and a significant increase in the cell doubling time, whereas the miR-143/506 dual downregulation demonstrated increased cellular motility. Furthermore, the individual miR-143 and miR-506 up- and downregulations exhibited cellular responses lacking an apparent miR-expression-dependent response in the respective analyses. Our work here indicates that, unlike the individual miR upregulations, the combinatorial miR treatment remained advantageous, even under prolonged miR upregulation. Finally, our findings demonstrate potential advantages of miR combinations vs. individual miR treatments.

Identification of CDKN3 as a Key Gene that Regulates Neuroblastoma Cell Differentiation

We conducted a high-content screening (HCS) in neuroblastoma BE(2)-C cells to identify cell cycle regulators that control cell differentiation using a library of siRNAs against cell cycle-regulatory genes. We discovered that knocking down expression of cyclin dependent kinase inhibitor 3 (CDKN3) showed the most potent effect in inducing neurite outgrowth, the morphological cell differentiation marker of neuroblastoma cells. We then demonstrated that CDKN3 knockdown increased expression of neuroblastoma molecular differentiation markers, neuron specific enolase (NSE), βIII-tubulin and growth associated protein 43 (GAP43). We further showed that CDKN3 knockdown reduced expression of cell proliferation markers Ki67 and proliferating cell nuclear antigen (PCNA), and reduced colony formation of neuroblastoma cells. More importantly, we observed a correlation of high tumor CDKN3 mRNA levels with poor patient survival in the investigation of public neuroblastoma patient datasets. In exploring the mechanisms that regulate CDKN3 expression, we found that multiple strong differentiation-inducing molecules, including miR-506-3p and retinoic acid, down-regulated CDKN3 expression. In addition, we found that N-Myc promoted CDKN3 expression at the transcriptional level by directly binding to the CDKN3 promoter. Furthermore, we found that CDKN3 and two additional differentiation-regulating cell cycle proteins identified in our HCS, CDC6 and CDK4, form an interactive network to promote expression of each other. In summary, we for the first time discovered the function of CDKN3 in regulating neuroblastoma cell differentiation and characterized the transcriptional regulation of CDKN3 expression by N-Myc in neuroblastoma cells. Our findings support that CDKN3 plays a role in modulating neuroblastoma cell differentiation and that overexpression of CDKN3 may contribute to neuroblastoma progression.

Targeting the epigenome of cancer stem cells in pediatric nervous system tumors

Medulloblastoma, neuroblastoma, and pediatric glioma account for almost 30% of all cases of pediatric cancers. Recent evidence indicates that pediatric nervous system tumors originate from stem or progenitor cells and present a subpopulation of cells with highly tumorigenic and stem cell-like features. These cancer stem cells play a role in initiation, progression, and resistance to treatment of pediatric nervous system tumors. Histone modification, DNA methylation, chromatin remodeling, and microRNA regulation display a range of regulatory activities involved in cancer origin and progression, and cellular identity, especially those associated with stem cell features, such as self-renewal and pluripotent differentiation potential. Here, we review the contribution of different epigenetic mechanisms in pediatric nervous system tumor cancer stem cells. The choice between a differentiated and undifferentiated state can be modulated by alterations in the epigenome through the regulation of stemness genes such as CD133, SOX2, and BMI1 and the activation neuronal of differentiation markers, RBFOX3, GFAP, and S100B. Additionally, we highlighted the stage of development of epigenetic drugs and the clinical benefits and efficacy of epigenetic modulators in pediatric nervous system tumors.

Discovery of 5-sulfonyltetrazoles as neuroblastoma differentiation agents

Previously, we developed an innovative high-content screening (HCS) approach to quantify neuroblastoma cell differentiation based on neurite outgrowth, a morphological differentiation marker of neuroblastoma cells. Here, we report the utilization of this platform to identify 1-methyl-5-(ethylsulfonyl)-1H-tetrazole (3a) as a new neuroblastoma differentiation agent using the ChemBridge DiversetTM commercial synthetic small molecule compound library. We show that this activity can be extended to a group of analogues, which can be accessed via a short two-step synthetic sequence. A new analogue, 5-(allylsulfonyl)-1-methyl-1H-tetrazole (3c) was identified in this synthetic effort as a compound that has even more pronounced differentiation and cytotoxic activities than the original hit compound 3a.

Development of Shortened miR-506-3p Mimics Exhibiting Strong Differentiation-Inducing Activity in Neuroblastoma Cells

microRNA mimics are synthetic RNA molecules that imitate the mature miRNA duplexes and their functions. These mimics have shown promise in treating cancers. Nucleotide chemical modifications of microRNA mimics have been investigated and have improved the stability of miRNA mimics. However, the potential therapeutic benefit of mimic analogs based on sequence modifications has not been explored. miR-506-3p was identified as a differentiation-inducing microRNA in neuroblastoma cells, suggesting the potential of applying the miR-506-3p mimic in neuroblastoma differentiation therapy. In this study, we explored the possibility of developing shortened miR-506-3p analogs that can maintain differentiation-inducing activities comparable to the wild-type miR-506-3p mimic. We found that deleting up to two nucleotides at either the 3' end or within the middle region of the miR-506-3p sequence fully maintained the differentiation-inducing activity when compared to the wild-type mimic. Deleting up to four nucleotides from the 3' end or deleting three nucleotides in the middle positions diminished the differentiation-inducing activity, but the analogs still maintained differentiation-inducing activities that were significantly higher than the negative control oligo. The shortened analog designs potentially benefit patients from two perspectives: (1) the reduced cost of manufacturing shortened analogs, and (2) the reduced non-specific toxicity due to their smaller molecular sizes.

MicroRNAs as prospective biomarkers, therapeutic targets and pharmaceuticals in neuroblastoma

Neuroblastomas, the most prevalent malignant solid neoplasms of childhood, originate from progenitor cells of the sympathetic nervous system. Their genetic causation is diverse and involves multiple molecular mechanisms. This review highlights multiple roles of microRNA in neuroblastoma pathogenesis and discusses the prospects of harnessing these important natural regulator molecules as biomarkers, therapeutic targets and pharmaceuticals in neuroblastoma.

Differentiation of two human neuroblastoma cell lines alters SV2 expression patterns

BACKGROUND

The synaptic vesicle glycoprotein 2 (SV2) family is essential to the synaptic machinery involved in neurotransmission and vesicle recycling. The isoforms SV2A, SV2B and SV2C are implicated in neurological diseases such as epilepsy, Alzheimer's and Parkinson's disease. Suitable cell systems for studying regulation of these proteins are essential. Here we present gene expression data of SV2A, SV2B and SV2C in two human neuroblastoma cell lines after differentiation.

METHODS

Human neuroblastoma cell lines SiMa and IMR-32 were treated for seven days with growth supplements (B-27 and N-2), all-trans-retinoic acid (ATRA) or vasoactive intestinal peptide (VIP) and gene expression levels of SV2 and neuronal targets were analyzed.

RESULTS

The two cell lines reacted differently to the treatments, and only one of the three SV2 isoforms was affected at a time. SV2B and choline O-acetyltransferase (CHAT) expression was changed in concert after growth supplement treatment, decreasing in SiMa cells while increasing in IMR-32. ATRA treatment resulted in no detected changes in SV2 expression in either cell line while VIP increased both SV2C and dopamine transporter (DAT) in IMR-32 cells.

CONCLUSION

The synergistic expression patterns between SV2B and CHAT as well as between SV2C and DAT mirror the connectivity between these targets found in disease models and knock-out animals, although here no genetic alteration was made. These cell lines and differentiation treatments could possibly be used to study SV2 regulation and function.

Synergism of Proneurogenic miRNAs Provides a More Effective Strategy to Target Glioma Stem Cells

Simple Summary

miRNAs function as critical regulators of gene expression and have been defined as contributors of cancer phenotypes by acting as oncogenes or tumor suppressors. Based on these findings, miRNA-based therapies have been explored in the treatment of many different malignancies. The use of single miRNAs has faced some challenges and showed limited success. miRNAs cooperate to regulate distinct biological processes and pathways and, therefore, combination of related miRNAs could amplify the repression of oncogenic factors and the effect on cancer relevant pathways. We established that the combination of tumor suppressor miRNAs miR-124, miR-128, and miR-137 is much more effective than single miRNAs in disrupting proliferation and survival of glioma stem cells and neuroblastoma lines and promoting differentiation and response to radiation. Subsequent genomic analyses showed that other combinations of tumor suppressor miRNAs could be equally effective, and its use could provide new routes to target in special cancer-initiating cell populations.

Abstract

Tumor suppressor microRNAs (miRNAs) have been explored as agents to target cancer stem cells. Most strategies use a single miRNA mimic and present many disadvantages, such as the amount of reagent required and the diluted effect on target genes. miRNAs work in a cooperative fashion to regulate distinct biological processes and pathways. Therefore, we propose that miRNA combinations could provide more efficient ways to target cancer stem cells. We have previously shown that miR-124, miR-128, and miR-137 function synergistically to regulate neurogenesis. We used a combination of these three miRNAs to treat glioma stem cells and showed that this treatment was much more effective than single miRNAs in disrupting cell proliferation and survival and promoting differentiation and response to radiation. Transcriptomic analyses indicated that transcription regulation, angiogenesis, metabolism, and neuronal differentiation are among the main biological processes affected by transfection of this miRNA combination. In conclusion, we demonstrated the value of using combinations of neurogenic miRNAs to disrupt cancer phenotypes and glioma stem cell growth. The synergistic effect of these three miRNA amplified the repression of oncogenic factors and the effect on cancer relevant pathways. Future therapeutic approaches would benefit from utilizing miRNA combinations, especially when targeting cancer-initiating cell populations.

Downregulation of miR-506-3p Facilitates EGFR-TKI Resistance through Induction of Sonic Hedgehog Signaling in Non-Small-Cell Lung Cancer Cell Lines

Non-small-cell lung cancer (NSCLC) patients with epidermal growth factor receptor (EGFR) mutation eventually develop resistance to EGFR-targeted tyrosine kinase inhibitors (TKIs). Treatment resistance remains the primary obstacle to the successful treatment of NSCLC. Although drug resistance mechanisms have been studied extensively in NSCLC, the regulation of these mechanisms has not been completely understood. Recently, increasing numbers of microRNAs (miRNAs) are implicated in EGFR-TKI resistance, indicating that miRNAs may serve as novel targets and may hold promise as predictive biomarkers for anti-EGFR therapy. MicroRNA-506 (miR-506) has been identified as a tumor suppressor in many cancers, including lung cancer; however, the role of miR-506 in lung cancer chemoresistance has not yet been addressed. Here we report that miR-506-3p expression was markedly reduced in erlotinib-resistant (ER) cells. We identified Sonic Hedgehog (SHH) as a novel target of miR-506-3p, aberrantly activated in ER cells. The ectopic overexpression of miR-506-3p in ER cells downregulates SHH signaling, increases E-cadherin expression, and inhibits the expression of vimentin, thus counteracting the epithelial-mesenchymal transition (EMT)-mediated chemoresistance. Our results advanced our understanding of the molecular mechanisms underlying EGFR-TKI resistance and indicated that the miR-506/SHH axis might represent a novel therapeutic target for future EGFR mutated lung cancer treatment.

Nitroalkanes as electrophiles: synthesis of triazole-fused heterocycles with neuroblastoma differentiation activity

We discovered a reaction of nitroalkanes with 2-hydrazinylquinolines, 2-hydrazinylpyridines and bis-2,4-dihydrazinylpyrimidines in polyphosphoric acid (PPA) affording 1,2,4-triazolo[4,3-a]quinolines, 1,2,4-triazolo[4,3-a]pyridines and bis[1,2,4]triazolo[4,3-a:4',3'-c]pyrimidines, respectively. The reaction expands the scope of heterocyclic annulations involving phosphorylated nitronates, believed to be the electrophilic intermediates formed from nitroalkanes in PPA. Several of the synthesized triazoles showed promising anticancer activity by inducing differentiation in neuroblastoma cancer cells. Due to the urgent need for novel differentiation agents for neuroblastoma therapy, this finding warrants further evaluation of this class of compounds against neuroblastoma.

High-Throughput Fluorescence-Based Screen Identifies the Neuronal MicroRNA miR-124 as a Positive Regulator of Alphavirus Infection

MicroRNAs (miRNAs) are small regulatory RNAs which act by modulating the expression of target genes. In addition to their role in maintaining essential physiological functions in the cell, miRNAs can also regulate viral infections. They can do so directly by targeting RNAs of viral origin or indirectly by targeting host mRNAs, and this can result in a positive or negative outcome for the virus. Here, we performed a fluorescence-based miRNA genome-wide screen in order to identify cellular miRNAs involved in the regulation of arbovirus infection in human cells. We identified 16 miRNAs showing a positive effect on Sindbis virus (SINV) expressing green fluorescent protein (GFP), among which were a number of neuron-specific ones such as miR-124. We confirmed that overexpression of miR-124 increases both SINV structural protein translation and viral production and that this effect is mediated by its seed sequence. We further demonstrated that the SINV genome possesses a binding site for miR-124. Both inhibition of miR-124 and silent mutations to disrupt this binding site in the viral RNA abolished positive regulation. We also proved that miR-124 inhibition reduces SINV infection in human differentiated neuronal cells. Finally, we showed that the proviral effect of miR-124 is conserved in other alphaviruses, as its inhibition reduces chikungunya virus (CHIKV) production in human cells. Altogether, our work expands the panel of positive regulation of the viral cycle by direct binding of host miRNAs to the viral RNA and provides new insights into the role of cellular miRNAs as regulators of alphavirus infection.IMPORTANCE Arthropod-borne (arbo) viruses are part of a class of pathogens that are transmitted to their final hosts by insects. Because of climate change, the habitat of some of these insects, such as mosquitoes, is shifting, thereby facilitating the emergence of viral epidemics. Among the pathologies associated with arbovirus infection, neurological diseases such as meningitis and encephalitis represent a significant health burden. Using a genome-wide miRNA screen, we identified neuronal miR-124 as a positive regulator of the Sindbis and chikungunya alphaviruses. We also showed that this effect was in part direct, thereby opening novel avenues to treat alphavirus infections.

MicroRNA dysregulation interplay with childhood abdominal tumors

Abdominal tumors (AT) in children account for approximately 17% of all pediatric solid tumor cases, and frequently exhibit embryonal histological features that differentiate them from adult cancers. Current molecular approaches have greatly improved the understanding of the distinctive pathology of each tumor type and enabled the characterization of novel tumor biomarkers. As seen in abdominal adult tumors, microRNAs (miRNAs) have been increasingly implicated in either the initiation or progression of childhood cancer. Moreover, besides predicting patient prognosis, they represent valuable diagnostic tools that may also assist the surveillance of tumor behavior and treatment response, as well as the identification of the primary metastatic sites. Thus, the present study was undertaken to compile up-to-date information regarding the role of dysregulated miRNAs in the most common histological variants of AT, including neuroblastoma, nephroblastoma, hepatoblastoma, hepatocarcinoma, and adrenal tumors. Additionally, the clinical implications of dysregulated miRNAs as potential diagnostic tools or indicators of prognosis were evaluated.

The PLAGL2/MYCN/miR-506-3p interplay regulates neuroblastoma cell fate and associates with neuroblastoma progression

Background

The oncogene MYCN is critical for tumorigenesis of several types of cancers including neuroblastoma. We previously reported that miR-506-3p repressed MYCN expression in neuroblastoma cells. However, the mechanism underlying such regulation was undetermined since there is no miR-506-3p target site in MYCN 3’UTR.

Methods

By a systematic investigation combining microarray, informatics and luciferase reporter assay, we identified that the transcriptional factor pleiomorphic adenoma gene-like 2 (PLAGL2) is a direct target of miR-506-3p that mediates its regulation on MYCN expression. Using CHIP-PCR and luciferase reporter assay, we validated the transcriptional regulation of MYCN by PLAGL2 and we further demonstrated the transcriptional regulation of PLAGL2 by MYCN. We examined the function of PLAGL2 in regulating neuroblastoma cell fate by cell viability assay, colony formation and Western blotting of differentiation markers. We examined the effect of retinoic acid, the differentiation agent used in neuroblastoma therapy, on miR-506-3p, PLAGL2 and MYCN expressions by quantitative PCR and Western blots. We investigated the clinical relevance of PLAGL2 expression by examining the correlation of tumor PLAGL2 mRNA levels with MYCN mRNA expression and patient survival using public neuroblastoma patient datasets.

Results

We found that miR-506-3p directly down-regulated PLAGL2 expression, and we validated a PLAGL2 binding site in the MYCN promoter region responsible for promoting MYCN transcription, thereby establishing a mechanism through which miR-506-3p regulates MYCN expression. Conversely, we discovered that MYCN regulated PLAGL2 transcription through five N-Myc-binding E-boxes in the PLAGL2 promoter region. We further confirmed the reciprocal regulation between endogenous PLAGL2 and MYCN in multiple neuroblastoma cell lines. Moreover, we found that PLAGL2 knockdown induced neuroblastoma cell differentiation and reduced cell proliferation, and combined knockdown of PLAGL2 and MYCN showed a synergistic effect. More strikingly, we found that high tumor PLAGL2 mRNA levels were significantly correlated with high MYCN mRNA levels and poor patient survival in neuroblastoma patients. Furthermore, we found that retinoic acid increased expression of miR-506-3p and repressed expression of MYCN and PLAGL2.

Conclusions

Our findings altogether suggest that the interplay network formed by PLAGL2, MYCN and miR-506-3p is an important mechanism in regulating neuroblastoma cell fate, determining neuroblastoma prognosis, and mediating the therapeutic function of retinoic acid.

ELF4 Is a Target of miR-124 and Promotes Neuroblastoma Proliferation and Undifferentiated State

13-Cis-retinoic acid (RA) is typically used in postremission maintenance therapy in patients with neuroblastoma. However, side effects and recurrence are often observed. We investigated the use of miRNAs as a strategy to replace RA as promoters of differentiation. miR-124 was identified as the top candidate in a functional screen. Genomic target analysis indicated that repression of a network of transcription factors (TF) could be mediating most of miR-124's effect in driving differentiation. To advance miR-124 mimic use in therapy and better define its mechanism of action, a high-throughput siRNA morphologic screen focusing on its TF targets was conducted and ELF4 was identified as a leading candidate for miR-124 repression. By altering its expression levels, we showed that ELF4 maintains neuroblastoma in an undifferentiated state and promotes proliferation. Moreover, ELF4 transgenic expression was able to counteract the neurogenic effect of miR-124 in neuroblastoma cells. With RNA sequencing, we established the main role of ELF4 to be regulation of cell-cycle progression, specifically through the DREAM complex. Interestingly, several cell-cycle genes activated by ELF4 are repressed by miR-124, suggesting that they might form a TF-miRNA regulatory loop. Finally, we showed that high ELF4 expression is often observed in neuroblastomas and is associated with poor survival. IMPLICATIONS: miR-124 induces neuroblastoma differentiation partially through the downregulation of TF ELF4, which drives neuroblastoma proliferation and its undifferentiated phenotype.

MicroRNAs in neuroblastoma tumorigenesis, therapy resistance, and disease evolution

Neuroblastoma (NB) deriving from neural crest cells is the most common extra-cranial solid cancer at infancy. NB originates within the peripheral sympathetic ganglia in adrenal medulla and along the midline of the body. Clinically, NB exhibits significant heterogeneity stretching from spontaneous regression to rapid progression to therapy resistance. MicroRNAs (miRNAs, miRs) are small (19-22 nt in length) non-coding RNAs that regulate human gene expression at the post-transcriptional level and are known to regulate cellular signaling, growth, differentiation, death, stemness, and maintenance. Consequently, the function of miRs in tumorigenesis, progression and resistance is of utmost importance for the understanding of dysfunctional cellular pathways that lead to disease evolution, therapy resistance, and poor clinical outcomes. Over the last two decades, much attention has been devoted to understanding the functional roles of miRs in NB biology. This review focuses on highlighting the important implications of miRs within the context of NB disease progression, particularly miRs’ influences on NB disease evolution and therapy resistance. In this review, we discuss the functions of both the “oncomiRs” and “tumor suppressor miRs” in NB progression/therapy resistance. These are the critical components to be considered during the development of novel miR-based therapeutic strategies to counter therapy resistance.

The miR-195 Axis Regulates Chemoresistance through TUBB and Lung Cancer Progression through BIRC5

Chemoresistance and metastasis are the major reasons for non-small cell lung cancer (NSCLC) treatment failure and patient deaths. We and others have shown that miR-195 regulates the sensitivity of NSCLC to microtubule-targeting agents (MTAs) in vitro and in vivo and that miR-195 represses the migration and invasion of NSCLC cells in vitro. However, the relationship between miR-195 and microtubule structure and function and whether miR-195 represses NSCLC metastasis in vivo remain unknown. We assessed the correlation between tumor levels of TUBB and patient survival, the effect of TUBB on drug response, and the effect of miR-195 on migration, invasion, and metastasis in vitro and in vivo. We found that miR-195 directly targets TUBB; knockdown of TUBB sensitizes cells to MTAs, while overexpression confers resistance; high expression of TUBB is correlated with worse survival of lung adenocarcinoma; TUBB is also regulated by CHEK1, which has been shown to regulate chemoresistance; and miR-195 targets BIRC5 to repress migration and invasion in vitro and metastasis in vivo. Our findings highlight the relevance of the miR-195/TUBB axis in regulating the response of NSCLC to MTAs and the importance of the miR-195/BIRC5 axis in regulating NSCLC metastasis.

Opportunities and challenges of circulating biomarkers in neuroblastoma

Molecular analysis of nucleic acid and protein biomarkers is becoming increasingly common in paediatric oncology for diagnosis, risk stratification and molecularly targeted therapeutics. However, many current and emerging biomarkers are based on analysis of tumour tissue, which is obtained through invasive surgical procedures and in some cases may not be accessible. Over the past decade, there has been growing interest in the utility of circulating biomarkers such as cell-free nucleic acids, circulating tumour cells and extracellular vesicles as a so-called liquid biopsy of cancer. Here, we review the potential of emerging circulating biomarkers in the management of neuroblastoma and highlight challenges to their implementation in the clinic.

Cancer Stem Cells and Neuroblastoma: Characteristics and Therapeutic Targeting Options

The majority of embryonal tumors or childhood blastomas derive from pluripotent progenitors or fetal stem cells that acquire cancer stem cell (CSC) properties: multipotency, self-renewal ability, metastatic potential, chemoresistance, more pronounced levels of drug transporters, enhanced DNA-damage repair mechanisms, and a quiescent state. Neuroblastoma (NB) is considered a neuroendocrine tumor and is the most common extracranial neoplasm in children. NB pathogenesis has frequently been associated with epigenetic dysregulation and a failure to implement a differentiation program. The origin, characteristics, and isolation of the CSC subpopulation in NB are still incompletely understood, despite the evidence that this cell subset contributes to disease recurrence and acquired resistance to standard therapies. Here, we summarize the literature regarding the isolation and characterization of CSCs in NB over the past decades, from the early recognition of the expression of stem cell factor (SCF) or its receptor c-KIT to more recent studies identifying the ability of G-CSF and STAT3 to support stem cell-like properties in NB cells. Additionally, we review the morphological variants of NB tumors whose recent epigenetic analyses have shed light on the tumor heterogeneity so common in NB. NB-derived mesenchymal stem cells have recently been isolated from primary tumors of NB patients and associated with a pro-tumorigenic role in the tumor microenvironment, enabling immune escape by tumors, and contributing to their invasive and metastatic capabilities. In particular, we will focus on epigenetic reprogramming in the CSC subpopulation in NB and strategies to target CSCs in NB.

microRNA-2110 functions as an onco-suppressor in neuroblastoma by directly targeting Tsukushi

microRNA-2110 (miR-2110) was previously identified as inducing neurite outgrowth in a neuroblastoma cell lines BE(2)-C, suggesting its differentiation-inducing and oncosuppressive function in neuroblastoma. In this study, we demonstrated that synthetic miR-2110 mimic had a generic effect on reducing cell survival in neuroblastoma cell lines with distinct genetic backgrounds, although the induction of cell differentiation traits varied between cell lines. In investigating the mechanisms underlying such functions of miR-2110, we identified that among its predicted target genes down-regulated by miR-2110, knockdown of Tsukushi (TSKU) expression showed the most potent effect in inducing cell differentiation and reducing cell survival, suggesting that TSKU protein plays a key role in mediating the functions of miR-2110. In investigating the clinical relevance of miR-2110 and TSKU expression in neuroblastoma patients, we found that low tumor miR-2110 levels were significantly correlated with high tumor TSKU mRNA levels, and that both low miR-2110 and high TSKU mRNA levels were significantly correlated with poor patient survival. These findings altogether support the oncosuppressive function of miR-2110 and suggest an important role for miR-2110 and its target TSKU in neuroblastoma tumorigenesis and in determining patient prognosis.

Phenotypic miRNA Screen Identifies miR-26b to Promote the Growth and Survival of Endothelial Cells

Endothelial cell (EC) proliferation is a crucial event in physiological and pathological angiogenesis. MicroRNAs (miRNAs) have emerged as important modulators of the angiogenic switch. Here we conducted high-content screening of a human miRNA mimic library to identify novel regulators of EC growth systematically. Several miRNAs were nominated that enhanced or inhibited EC growth. Of these, we focused on miR-26b, which is a conserved candidate and expressed in multiple human EC types. miR-26b overexpression enhanced EC proliferation, migration, and tube formation, while inhibition of miR-26b suppressed the proliferative and angiogenic capacity of ECs. A combinatory functional small interfering RNA (siRNA) screening of 48 predicted gene targets revealed that miR-26b enhanced EC growth and survival through inhibiting PTEN expression. Local administration of miR-26b mimics promoted the growth of new microvessels in the Matrigel plug model. In the mouse model of hindlimb ischemia, miR-26b was found to be downregulated in endothelium in the first week following ischemia, and local overexpression of miR-26b improved the survival of capillaries and muscle fibers in ischemic muscles. Our findings suggest that miR-26b enhances EC proliferation, survival, and angiogenesis. miR-26b is a potential target for developing novel pro-angiogenic therapeutics in ischemic disease.

Induction of morphological and functional differentiation of human neuroblastoma cells by miR-124

Neuroblastoma is the most common extracranial solid tumour in children, and differentiation is considered its most appropriate therapy. In this work, we studied effects of miR-124 overexpression on differentiation in M17 cell line as a model of neuroblastoma cancer. Influence of miR-124 overexpression on differentiation in M17 cells was studied. M17 cells were infected with lentivirus that contained miR-124 precursor sequence and followed for 2 weeks to differentiate. Ectopic expression of miR-124 in M17 cells changed the shape of spherical undifferentiated cells to cells with extended neurites that formed neuronal networks. Overexpression of MiR-124 respectively increased the expression level of markers of β-Tubulin III, MAP2, SYN, NF-M and Nestin by 16-, 5-, 4-, 2.3- and 2-folds at the messenger RNA level. MiR-124 overexpression also increased the protein levels of β-Tubulin III and MAP2. Moreover, exogenous expression of miR-124 significantly increased the intracellular calcium in differentiated M17 cells. Since miR-124 is naturally expressed in neuronal cells and is downregulated in neuroblastoma cancer cells, differentiation with this type of microRNA can be a novel treatment for neuroblastoma cancer.

miR-195 potentiates the efficacy of microtubule-targeting agents in non-small cell lung cancer

Microtubule-targeting agents (MTAs) are widely used for the treatment of non-small cell lung cancer (NSCLC). The response rate is only ∼25%, mainly attributable to drug resistance. To identify determinants of resistance in NSCLC, we performed a high-throughput screen using a library of miRNA mimics. Here we report that miR-195 synergizes with MTAs to inhibit the growth of NSCLC cells in vitro, that increased expression of miR-195 sensitizes NSCLC cells to MTAs and that repression of miR-195 confers resistance to MTAs. We show that NSCLC tumors over-expressing miR-195 are more sensitive to MTA treatment and that induced expression of miR-195 in NSCLC tumors potentiates the anti-tumor effect of MTAs. Additionally, we demonstrate that miR-195 targets checkpoint kinase 1 (CHEK1) to regulate the response of NSCLC cells to MTAs, that over-expression of CHEK1 contributes to resistance to MTAs and that knock-down of CHEK1 synergizes with MTAs to repress cell growth. Our results highlight the importance of miR-195 in regulating the response of NSCLC cells to MTAs and underline the potential application of miR-195 as a biomarker for response to MTAs, and as a therapeutic adjuvant to MTA treatment.

The emerging role of miR-506 in cancer

MicroRNAs (miRNAs) are small non-coding RNAs that post-transcriptionally regulate gene expression. They are involved in almost all biological processes, and many have been identified as potential oncogenes or tumor suppressor genes. miR-506 was recently discovered to play pivotal roles in regulating cell proliferation, differentiation, migration and invasion. Dysregulation of miR-506 has been demonstrated in multiple types of cancers; however, whether it functions as an oncogene or a tumor suppressor seems to be context-dependent. Altered miR-506 expression in cancer is caused by promoter methylation and changes in upstream transcription factors. In this review, we summarize the current understanding of the diverse roles and underlying mechanisms of miR-506 and its involvement in cancer, and suggest the potential therapeutic strategy based on miR-506.

MicroRNA-194 Regulates the Development and Differentiation of Sensory Patches and Statoacoustic Ganglion of Inner Ear by Fgf4

Background

MicroRNA 194 is involved in the differentiation of various types of cells, such as adipose derived stem cells, human embryonic stem cells, and bone marrow mesenchymal stem cells. Previously, we found that miR-194 was highly expressed in the inner ear sensory patch and neurons in mice embryos. However, the role of miR-194 in the development of the inner ear and its underlying mechanism have not been elucidated yet.

Material/Methods

The expression level of miR-194 has been altered by using antisense morpholino oligonucleotides (MO) and synthesized miRNAs in zebrafish.

Results

We found that miR-194 was vastly expressed in the inner ear and central nervous system (CNS) in zebrafish. Loss of function of miR-194 could strongly affected the development of zebrafish embryos, including delayed embryonic development, edema of the pericardium, small head, axial deviation, delayed development of inner ear, closer location of two otoliths, delayed fusion of the semicircular canals, and abnormal otolith number in some cases. In addition, the behavior of zebrafish was also adversely affected with impaired balance and biased swimming route. Misexpression of miR-194 could strongly affected the development and differentiation of spiral ganglion neuron (SGN) in inner ear through Fgf4 in vitro. Similar results have also been observed that the overexpression and knockdown of miR-194 strongly disturbed the development and differentiation of the sensory patches and Statoacoustic ganglion (SAG) through Fgf4 in zebrafish in vivo. Our results indicated that miR-194 may regulate the development and differentiation of sensory patches and SAG through Fgf4.

Conclusions

Our data revealed a vital role of miR-194 in regulating the development and differentiation of the inner ear.

A combined gene expression and functional study reveals the crosstalk between N-Myc and differentiation-inducing microRNAs in neuroblastoma cells

MYCN amplification is the most common genetic alteration in neuroblastoma and plays a critical role in neuroblastoma tumorigenesis. MYCN regulates neuroblastoma cell differentiation, which is one of the mechanisms underlying its oncogenic function. We recently identified a group of differentiation-inducing microRNAs. Given the demonstrated inter-regulation between MYCN and microRNAs, we speculated that MYCN and the differentiation-inducing microRNAs might form an interaction network to control the differentiation of neuroblastoma cells. In this study, we found that eight of the thirteen differentiation-inducing microRNAs, miR-506-3p, miR-124-3p, miR-449a, miR-34a-5p, miR-449b-5p, miR-103a-3p, miR-2110 and miR-34b-5p, inhibit N-Myc expression by either directly targeting the MYCN 3'UTR or through indirect regulations. Further investigation showed that both MYCN-dependent and MYCN-independent pathways play roles in mediating the differentiation-inducing function of miR-506-3p and miR-449a, two microRNAs that dramatically down-regulate MYCN expression. On the other hand, we found that N-Myc inhibits the expression of multiple differentiation-inducing microRNAs, suggesting that these miRNAs play a role in mediating the function of MYCN. In examining the published dataset collected from clinical neuroblastoma specimens, we found that expressions of two miRNAs, miR-137 and miR-2110, were significantly anti-correlated with MYCN mRNA levels, suggesting their interactions with MYCN play a clinically-relevant role in maintaining the MYCN and miRNA expression levels in neuroblastoma. Our findings altogether suggest that MYCN and differentiation-inducing miRNAs form an interaction network that play an important role in neuroblastoma tumorigenesis through regulating cell differentiation.

Differential expression of microRNAs in the normal skin of the Han and Uyghur populations in Xinjiang Province

In this study, we investigated the expression of microRNAs (miRNAs) in the skin samples from the Han and Uyghur populations in Xinjiang, China. The miRNA levels of the normal skin samples from 10 individuals of Uyghur or Han were tested by microarray and the expression differentiations were compared. Among the 3100 probes for microarray, a total of 247 miRNAs were differentially expressed in the Han versus Uyghur population, including 76 upregulated miRNAs and 171 downregulated miRNAs. The most significantly upregulated miRNAs were miR-141-3p, miR-1915-5p, kshv-miR-K12-2-5p, and miR-222-3p. And the most significantly downregulated miRNAs included miR-1207-3p and miR-625-3p. We have confirmed the upregulation of miR-141-3p and miR-1915-5p by qRT-PCR. There were no statistical correlations in the expression of miR-141-3p or miR-1915-5p with the age or gender within each group. Interestingly, the differentially expressed miRNAs were enriched in some cancer-related pathways, such as p53, mitogen-activated protein kinase, and WNT signal pathways. Collectively, these dysregulated expressions of the miRNAs may provide a better understanding of the differences in the incidence and mortality of skin-related carcinoma between the Uyghur and Han populations in Xinjiang.

Unveiling MYCN regulatory networks in neuroblastoma via integrative analysis of heterogeneous genomics data

MYCN, an oncogenic transcription factor of the Myc family, is a major driver of neuroblastoma tumorigenesis. Due to the difficulty in drugging MYCN directly, revealing the molecules in MYCN regulatory networks will help to identify effective therapeutic targets for neuroblastoma therapy. Here we perform ChIP-sequencing and small RNA-sequencing of neuroblastoma cells to determine the MYCN-binding sites and MYCN-associated microRNAs, and integrate various types of genomic data to construct MYCN regulatory networks. The overall analysis indicated that MYCN-regulated genes were involved in a wide range of biological processes and could be used as signatures to identify poor-prognosis MYCN-non-amplified patients. Analysis of the MYCN binding sites showed that MYCN principally served as an activator. Using a computational approach, we identified 32 MYCN co-regulators, and some of these findings are supported by previous studies. Moreover, we investigated the interplay between MYCN transcriptional and microRNA post-transcriptional regulations and identified several microRNAs, such as miR-124-3p and miR-93-5p, which may significantly contribute to neuroblastoma pathogenesis. We also found MYCN and its regulated microRNAs acted together to repress the tumor suppressor genes. This work provides a comprehensive view of MYCN regulations for exploring therapeutic targets in neuroblastoma, as well as insights into the mechanism of neuroblastoma tumorigenesis.

Unveiling massive numbers of cancer-related urinary-microRNA candidates via nanowires

Analyzing microRNAs (miRNAs) within urine extracellular vesicles (EVs) is important for realizing miRNA-based, simple, and noninvasive early disease diagnoses and timely medical checkups. However, the inherent difficulty in collecting dilute concentrations of EVs (<0.01 volume %) from urine has hindered the development of these diagnoses and medical checkups. We propose a device composed of nanowires anchored into a microfluidic substrate. This device enables EV collections at high efficiency and in situ extractions of various miRNAs of different sequences (around 1000 types) that significantly exceed the number of species being extracted by the conventional ultracentrifugation method. The mechanical stability of nanowires anchored into substrates during buffer flow and the electrostatic collection of EVs onto the nanowires are the two key mechanisms that ensure the success of the proposed device. In addition, we use our methodology to identify urinary miRNAs that could potentially serve as biomarkers for cancer not only for urologic malignancies (bladder and prostate) but also for nonurologic ones (lung, pancreas, and liver). The present device concept will provide a foundation for work toward the long-term goal of urine-based early diagnoses and medical checkups for cancer.

Real-time live-cell analysis system for screening single tumor cell clones and analyzing their colony-forming ability

AIM

To screen single tumor cell clones and evaluating their colony-forming ability by IncuCyte ZOOM.

METHODS

Primary tumor cells were isolated by differential digestion and differential adherence method. On the basis of limited dilution, dynamic real-time tracking technology and full aperture imaging technology were used to track single cell clones and evaluate their colony-formation ability.

RESULTS

Six lines of primary tumor cells (TJ3ZX-02 to 07) were isolated from 30 tumor tissues, and 89 persistently proliferative tumor cell clones were screened from five primary tumor cell lines (TJ3ZX-03 to 07), of which 67 were expanded and cryopreserved. Eighteen monoclonal cell lines were excluded due to the lack of expansion ability, and 28 polyclonal cell lines were excluded because of consisting of two or more cell types as revealed by the Sequence Diagram. The analysis of clone-forming ability of two monoclonal cell strains (TJ3ZX-06-B11, TJ3ZX-07-H11) showed that the clone-forming rates for the plate method (35.17%, 13.17%) were significantly higher than those for IncuCyte ZOOM (23.13%, 5.51%) at 14 d (P < 0.05), although there was no significant difference at 21 d (35.63% and 13.22% for IncuCyte ZOOM).

CONCLUSION

IncuCyte ZOOM is simple, accurate and time-saving for screening single clones and measuring their colony-forming ability.

Induction of Mesenchymal-Epithelial Transitions in Sarcoma Cells

Phenotypic plasticity refers to a phenomenon in which cells transiently gain traits of another lineage. During carcinoma progression, phenotypic plasticity drives invasion, dissemination and metastasis. Indeed, while most of the studies of phenotypic plasticity have been in the context of epithelial-derived carcinomas, it turns out sarcomas, which are mesenchymal in origin, also exhibit phenotypic plasticity, with a subset of sarcomas undergoing a phenomenon that resembles a mesenchymal-epithelial transition (MET). Here, we developed a method comprising the miR-200 family and grainyhead-like 2 (GRHL2) to mimic this MET-like phenomenon observed in sarcoma patient samples.We sequentially express GRHL2 and the miR-200 family using cell transduction and transfection, respectively, to better understand the molecular underpinnings of these phenotypic transitions in sarcoma cells. Sarcoma cells expressing miR-200s and GRHL2 demonstrated enhanced epithelial characteristics in cell morphology and alteration of epithelial and mesenchymal biomarkers. Future studies using these methods can be used to better understand the phenotypic consequences of MET-like processes on sarcoma cells, such as migration, invasion, metastatic propensity, and therapy resistance.

miR-506 suppresses neuroblastoma metastasis by targeting ROCK1

Neuroblastoma is a complex form of cancer with highly heterogeneous clinical behavior that arises during childhood from precursor cells of the sympathetic nervous system. In patients with neuroblastoma, mortality often occurs as a result of metastasis. The disease predominantly spreads to bone marrow, with a survival rate of ~40%. The current study demonstrates that microRNA (miR)-506 directly targets and downregulates Rho-associated, coiled-coil containing protein kinase 1 (ROCK1) in transforming growth factor (TGF)-β non-canonical pathways. It may be concluded that ROCK1 contributes to the invasion and migration of neuroblastoma cells by directly downregulating miR-506; thus, leading to the upregulation of ROCK1, which promotes cell invasion and migration. The present results provide a novel understanding of how miR-506 directly regulates TGF-β non-canonical signaling.

Action of HMGB1 on miR-221/222 cluster in neuroblastoma cell lines

microRNA (miR/miRNA) are small non-coding RNAs that control gene expression at the post-transcriptional level by targeting mRNAs. Aberrant expression of miRNAs is often observed in different types of cancer. Specific miRNAs function as tumor suppressors or oncogenes and interfere with various aspects of carcinogenesis, including differentiation, proliferation and invasion. Upregulation of miRNAs 221 and 222 has been shown to induce a malignant phenotype in numerous human cancers via inhibition of phosphatase and tensin homolog (PTEN) expression. Neuroblastoma is the most common extracranial solid malignancy in children, which is characterized by cellular heterogeneity that corresponds to different clinical outcomes. The different cellular phenotypes are associated with different gene mutations and miRs that control genetic and epigenetic factors. For this reason miRs are considered a potential therapeutic target in neuroblastoma. The aim of the present study was to investigate the mechanisms by which extracellular high mobility group box 1 (HMGB1) promotes cell growth in neuroblastoma. SK-N-BE(2) and SH-SY5Y neuroblastoma derived cell lines were transfected with the antisense oligonucleotides, anti-miR-221 and -222, followed by treatment with HMGB1 to investigate the expression of the oncosuppressor PTEN. In this study, it was demonstrated that HMGB1, which is released by damaged cells and tumor cells, upregulates miR-221/222 oncogenic clusters in the two human neuroblastoma derived cell lines. The results revealed that the oncogenic cluster miRs 221/222 were more highly expressed by the most undifferentiated cell line [SK-N-BE(2)] compared with the the less tumorigenic cell line (SH-SY5Y) and that exogenous HMGB1 increases this expression. In addition, HMGB1 modulates PTEN expression via miR-221/222, as demonstrated by transiently blocking miR-221/222 with anti-sense oligonucleotides. These results may lead to the development of novel therapeutic strategies for neuroblastoma.

Long noncoding RNAs and neuroblastoma

Neuroblastoma is a disease that affects infants and despite intense multimodal therapy, high-risk patients have low survival rates (<50%). In recent years long noncoding RNAs (lncRNAs) have become the cutting edge of cancer research with inroads made in understanding their roles in multiple cancer types, including prostate and breast cancers. The roles of lncRNAs in neuroblastoma have just begun to be elucidated. This review summarises where we are with regards to lncRNAs in neuroblastoma. The known mechanistic roles of lncRNAs during neuroblastoma pathogenesis are discussed, as well as the relationship between lncRNA expression and the differentiation capacity of neuroblastoma cells. We speculate about the use of some of these lncRNAs, such as those mapping to the 6p22 hotspot, as biomarkers for neuroblastoma prognosis and treatment. This novel way of thinking about both neuroblastoma and lncRNAs brings a new perspective to the prognosis and treatment of high-risk patients.

microRNA-449a functions as a tumor suppressor in neuroblastoma through inducing cell differentiation and cell cycle arrest

microRNA-449a (miR-449a) has been identified to function as a tumor suppressor in several types of cancers. However, the role of miR-449a in neuroblastoma has not been intensively investigated. We recently found that the overexpression of miR-449a significantly induces neuroblastoma cell differentiation, suggesting its potential tumor suppressor function in neuroblastoma. In this study, we further investigated the mechanisms underlying the tumor suppressive function of miR-449a in neuroblastoma. We observed that miR-449a inhibits neuroblastoma cell survival and growth through 2 mechanisms--inducing cell differentiation and cell cycle arrest. Our comprehensive investigations on the dissection of the target genes of miR-449a revealed that 3 novel targets- MFAP4, PKP4 and TSEN15 -play important roles in mediating its differentiation-inducing function. In addition, we further found that its function in inducing cell cycle arrest involves down-regulating its direct targets CDK6 and LEF1. To determine the clinical significance of the miR-449a-mediated tumor suppressive mechanism, we examined the correlation between the expression of these 5 target genes in neuroblastoma tumor specimens and the survival of neuroblastoma patients. Remarkably, we noted that high tumor expression levels of all the 3 miR-449a target genes involved in regulating cell differentiation, but not the target genes involved in regulating cell cycle, are significantly correlated with poor survival of neuroblastoma patients. These results suggest the critical role of the differentiation-inducing function of miR-449a in determining neuroblastoma progression. Overall, our study provides the first comprehensive characterization of the tumor-suppressive function of miR-449a in neuroblastoma, and reveals the potential clinical significance of the miR-449a-mediated tumor suppressive pathway in neuroblastoma prognosis.

Association between single nucleotide polymorphisms in MiR219-1 and MiR137 and susceptibility to schizophrenia in a Chinese population

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A case-control study investigated rs107822, rs1625579 and risk of schizophrenia.

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rs107822 was negatively associated with susceptibility to schizophrenia.

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No association was found between rs1625579 and the disorder.

Schizophrenia is one of the most common mental disorders to severely affect human health worldwide. Single nucleotide polymorphisms (SNPs) within related genes are candidate susceptible factors for the disorder. Rs107822 within MiR219-1 and rs1625579 within MiR137 were genotyped in 589 cases and 622 controls to investigate the possible association between the loci and schizophrenia in a Chinese population. Our results showed significant association between rs107822 and the disorder in allele (C vs. T: adjusted OR = 0.773, 95%CI = 0.655–0.912), co-dominant (TC vs. TT: adjusted OR = 0.734, 95%CI = 0.571–0.943; CC vs. TT: adjusted OR = 0.655, 95%CI = 0.459–0.936), dominant (TC + CC vs. TT: adjusted OR = 0.707, 95%CI = 0.559–0.895), and recessive (CC vs. TC + TT: adjusted OR = 0.724, 95%CI = 0.524–0.999) models, respectively. Meanwhile, negative associations were also observed between rs107822 and the disorder in male and female subgroups, and genotype CC of the locus was significantly associated with a lower positive symptom score of PANSS compared to genotype TT carrier in the cases group. However, we didn’t observe a significant association between rs1625579 and the disorder. These findings indicate that rs107822 within MiR219-1 might be involved in pathogenesis of schizophrenia and that genotypes TC, CC and allele C of the locus are protective factors for schizophrenia in a Chinese population.

Key nodes of a microRNA network associated with the integrated mesenchymal subtype of high-grade serous ovarian cancer

Metastasis is the main cause of cancer mortality. One of the initiating events of cancer metastasis of epithelial tumors is epithelial-to-mesenchymal transition (EMT), during which cells dedifferentiate from a relatively rigid cell structure/morphology to a flexible and changeable structure/morphology often associated with mesenchymal cells. The presence of EMT in human epithelial tumors is reflected by the increased expression of genes and levels of proteins that are preferentially present in mesenchymal cells. The combined presence of these genes forms the basis of mesenchymal gene signatures, which are the foundation for classifying a mesenchymal subtype of tumors. Indeed, tumor classification schemes that use clustering analysis of large genomic characterizations, like The Cancer Genome Atlas (TCGA), have defined mesenchymal subtype in a number of cancer types, such as high-grade serous ovarian cancer and glioblastoma. However, recent analyses have shown that gene expression-based classifications of mesenchymal subtypes often do not associate with poor survival. This “paradox” can be ameliorated using integrated analysis that combines multiple data types. We recently found that integrating mRNA and microRNA (miRNA) data revealed an integrated mesenchymal subtype that is consistently associated with poor survival in multiple cohorts of patients with serous ovarian cancer. This network consists of 8 major miRNAs and 214 mRNAs. Among the 8 miRNAs, 4 are known to be regulators of EMT. This review provides a summary of these 8 miRNAs, which were associated with the integrated mesenchymal subtype of serous ovarian cancer.

Genetic mutation of p53 and suppression of the miR-17∼92 cluster are synthetic lethal in non-small cell lung cancer due to upregulation of vitamin D Signaling

Lung cancer is the leading cause of cancer-related fatalities. Recent success developing genotypically targeted therapies, with potency only in well-defined subpopulations of tumors, suggests a path to improving patient survival. We used a library of oligonucleotide inhibitors of microRNAs, a class of posttranscriptional gene regulators, to identify novel synthetic lethal interactions between miRNA inhibition and molecular mechanisms in non-small cell lung cancer (NSCLC). Two inhibitors, those for miR-92a and miR-1226*, produced a toxicity distribution across a panel of 27 cell lines that correlated with loss of p53 protein expression. Notably, depletion of p53 was sufficient to confer sensitivity to otherwise resistant telomerase-immortalized bronchial epithelial cells. We found that both miR inhibitors cause sequence-specific downregulation of the miR-17∼92 polycistron, and this downregulation was toxic only in the context of p53 loss. Mechanistic studies indicated that the selective toxicity of miR-17∼92 polycistron inactivation was the consequence of derepression of vitamin D signaling via suppression of CYP24A1, a rate-limiting enzyme in the 1α,25-dihydroxyvitamin D3 metabolic pathway. Of note, high CYP24A1 expression significantly correlated with poor patient outcome in multiple lung cancer cohorts. Our results indicate that the screening approach used in this study can identify clinically relevant synthetic lethal interactions and that vitamin D receptor agonists may show enhanced efficacy in p53-negative lung cancer patients.

MiR-506 inhibits multiple targets in the epithelial-to-mesenchymal transition network and is associated with good prognosis in epithelial ovarian cancer

Extensive investigations have shown that miRNAs are important regulators of epithelial-to-mesenchymal transition (EMT), mainly targeting the transcriptional repressors of E-cadherin (E-cad). Less is known about the post-transcriptional regulation of vimentin or N-cadherin (N-cad) in EMT. Our previous study identified miR-506 as a key EMT inhibitor through directly targeting the E-cad transcriptional repressor SNAI2. In this study, we provide evidence that miR-506 simultaneously suppresses vimentin and N-cad. The knockdown of vimentin using siRNA reversed EMT, suppressed cell migration and invasion, and increased E-cad expression on the cell membrane in epithelial ovarian cancer (EOC) cells. In a set of tissue microarrays that included 204 EOCs of all major subtypes (eg serous, endometrioid, clear cell, and mucinous), miR-506 was positively correlated with E-cad and negatively correlated with vimentin and N-cad in all subtypes of EOC. A high level of miR-506 was positively associated with early FIGO stage and longer survival in EOC. Introduction of miR-506, mediated by nanoparticle delivery, in EOC orthotopic mouse models resulted in decreased vimentin, N-cad, and SNAI2 expression and increased E-cad expression; it also suppressed the dissemination of EOC cells. Thus, miR-506 represents a new class of miRNA that regulates both E-cad and vimentin/N-cad in the suppression of EMT and metastasis.