BCR-ABL mediated repression of miR-223 results in the activation of MEF2C and PTBP2 in chronic myeloid leukemia

Role of miRNAs to control the progression of Chronic Myeloid Leukemia by their expression levels

Chronic Myeloid Leukemia (CML) is a myeloproliferative disorder distinguished by a specific genetic anomaly known as a reciprocal translocation between chromosomes 9 and 22. This translocation causes fusion between the BCR and ABL regions. Consequently, BCR::ABL oncoprotein is formed, which plays a significant role in driving CML progression. Imatinib, a tyrosine kinase inhibitor (TKI), became the first line of drugs against CML. However, with continuous treatment, patients developed resistance against it. Indeed, to address this challenge, microRNA-based therapy emerges as a promising approach. miRNAs are 20-25 nucleotides long and hold great significance in various cellular processes, including cell differentiation, proliferation, migration, and apoptosis. In several malignancies, it has been reported that miRNAs might help to promote or prevent tumourigenesis and abnormal expression because they could act as both oncogenes/tumor suppressors. Recently, because of their vital regulatory function in maintaining cell homeostasis, miRNAs might be used to control CML progression and in developing new therapies for TKI-resistant patients. They might also act as potential prognostic, diagnostic, and therapeutic biomarkers based on their expression profiles. Various annotation tools and microarray-based expression profiles can be used to predict dysregulated miRNAs and their target genes. The main purpose of this review is to provide brief insights into the role of dysregulated miRNAs in CML pathogenesis and to emphasize their clinical relevance, such as their significant potential as therapeutics against CML. Utilizing these miRNAs as a therapeutic approach by inhibition or amplification of their activity could unlock new doors for the therapy of CML.

miR-223 Plays a Key Role in Obesogen-Enhanced Adipogenesis in Mesenchymal Stem Cells and in Transgenerational Obesity

Exposure of pregnant F0 mouse dams to the obesogen tributyltin (TBT) predisposes unexposed male descendants to obesity and diverts mesenchymal stem cells (MSCs) toward the adipocytic lineage. TBT promotes adipogenic commitment and differentiation of MSCs in vitro. To identify TBT-induced factors predisposing MSCs toward the adipocytic fate, we exposed mouse MSCs to TBT, the peroxisome proliferator activated receptor gamma (PPARγ)-selective agonist rosiglitazone, or the retinoid X receptor (RXR)-selective agonist LG-100268. Then we determined their transcriptomal profiles to determine candidate microRNAs (miR) regulating adipogenic commitment and differentiation. Of the top 10 candidate microRNAs predicted by Ingenuity Pathway Analysis, miR-21, miR-33, and miR-223 were expressed consistent with an ability to differentially regulate target genes during adipogenesis. We found that 24-hour exposure to 50nM TBT caused miR-223 levels in MSCs to increase; expression of its target genes ZEB1, NFIB, and FOXP1 was decreased. Rosiglitazone and TBT increased miR-223 levels. This induction was inhibited by the PPARγ antagonist T0070907 but not by the RXR antagonists HX531 or UVI3003, placing miR-223 downstream of PPARγ. Chromatin immunoprecipitation confirmed TBT-induced binding of PPARγ to regulatory elements in the miR-223 promoter. miR-223 levels were elevated in white adipose tissue of F2 and F3 male descendants of pregnant F0 mouse dams exposed to 50nM TBT throughout gestation. miR-223 levels were potentiated in males fed an increased fat diet. We infer that TBT induced miR-223 expression and increased adipogenesis in MSCs through the PPARγ pathway and that transgenerationally increased expression of miR-223 plays an important role in the development of obesity caused by TBT exposure.

A Systematic Review of Candidate miRNAs, Its Targeted Genes and Pathways in Chronic Myeloid Leukemia-An Integrated Bioinformatical Analysis

Chronic myeloid leukaemia is blood cancer due to a reciprocal translocation, resulting in a BCR-ABL1 oncogene. Although tyrosine kinase inhibitors have been successfully used to treat CML, there are still cases of resistance. The resistance occurred mainly due to the mutation in the tyrosine kinase domain of the BCR-ABL1 gene. However, there are still many cases with unknown causes of resistance as the etiopathology of CML are not fully understood. Thus, it is crucial to figure out the complete pathogenesis of CML, and miRNA can be one of the essential pathogeneses. The objective of this study was to systematically review the literature on miRNAs that were differentially expressed in CML cases. Their target genes and downstream genes were also explored. An electronic search was performed via PubMed, Scopus, EBSCOhost MEDLINE, and Science Direct. The following MeSH (Medical Subject Heading) terms were used: chronic myeloid leukaemia, genes and microRNAs in the title or abstract. From 806 studies retrieved from the search, only clinical studies with in-vitro experimental evidence on the target genes of the studied miRNAs in CML cells were included. Two independent reviewers independently scrutinised the titles and abstracts before examining the eligibility of studies that met the inclusion criteria. Study design, sample size, sampling type, and the molecular method used were identified for each study. The pooled miRNAs were analysed using DIANA tools, and target genes were analysed with DAVID, STRING and Cytoscape MCODE. Fourteen original research articles on miRNAs in CML were included, 26 validated downstream genes and 187 predicted target genes were analysed and clustered into 7 clusters. Through GO analysis, miRNAs’ target genes were localised throughout the cells, including the extracellular region, cytosol, and nucleus. Those genes are involved in various pathways that regulate genomic instability, proliferation, apoptosis, cell cycle, differentiation, and migration of CML cells.

2-Methoxyestradiol combined with ascorbic acid facilitates the apoptosis of chronic myeloid leukemia cells via the microRNA-223/Fms-like tyrosine kinase 3/phosphatidylinositol-3 kinase/protein kinase B axis

Chronic myeloid leukemia (CML) is a malignant myeloproliferative tumor. 2-Methoxyestradiol (2-ME) is an endogenous estrogen metabolite that shows efficacy in human malignancies. Ascorbic acid (AA) possesses antioxidant activity. This study explored the mechanism of 2-ME combined with AA in the apoptosis of CML cells. Firstly, human CML cell lines were treated with 2-ME and AA. The cell viability, apoptosis, reactive oxygen species (ROS), and mitochondrial membrane potential (MMP) were detected. miR-223 expression in CML cells was detected. In addition, CML cells were transfected with miR-223 inhibitor. The binding relationship between miR-223 and FLT3 was verified. Subsequently, the FLT3 was overexpressed or silenced for the function rescue experiment to confirm the role of FLT3 in CML cell apoptosis. The expression levels of key factors of the PI3K/AKT pathway were detected. Finally, xenograft nude mouse models were established for in vivo verification. 2-ME + AA treatment inhibited CML cell viability and promoted apoptosis, elevated ROS content, and reduced MMP. 2-ME + AA treatment promoted miR-223 expression in CML cells. miR-223 targeted FLT3. Moreover, miR-223 inhibitor or FLT3 overexpression partially annulled the effect of 2-ME + AA on CML cells. 2-ME + AA inhibited the PI3K/AKT pathway via the miR-223/FLT3 axis. Furthermore, 2-ME + AA suppressed CML xenograft growth in mice. Collectively, 2-ME + AA promoted miR-223 expression and suppressed FLT3 and the PI3K/AKT pathway, thereby facilitating the apoptosis of CML cells and inhibiting CML xenograft growth in mice.

Downregulation of miR-142a Contributes to the Enhanced Anti-Apoptotic Ability of Murine Chronic Myelogenous Leukemia Cells

Background

Leukemic stem cell (LSC) is thought to be responsible for chronic myelogenous leukemia (CML) initiation and relapse. However, the inherent regulation of LSCs remains largely obscure. Herein, we integratedly analyzed miRNA and gene expression alterations in bone marrow (BM) Lin^-Sca1⁺c-Kit⁺ cells (LSKs) of a tet-off inducible CML mouse model, Scl/tTA-BCR/ABL (BA).

Methods

Scl/tTA and TRE-BA transgenic mice were crossed in the presence of doxycycline to get double transgenic mice. Both miRNA and mRNA expression profiles were generated from BM LSKs at 0 and 3 weeks after doxycycline withdrawal. The target genes of differentially expressed miRNAs were predicted, followed by the miRNA-mRNA network construction. In vitro and in vivo experiments were further performed to elucidate their regulation and function in CML progression.

Results

As a result of the integrated analysis and experimental validation, an anti-apoptotic pathway emerged from the fog. miR-142a was identified to be downregulated by enhanced ERK-phosphorylation in BA-harboring cells, thereby relieving its repression on Ciapin1, an apoptosis inhibitor. Moreover, miR-142a overexpression could partially rescue the abnormal anti-apoptotic phenotype and attenuate CML progression.

Conclusion

Taken together, this study explored the miRNA-mRNA regulatory networks in murine CML LSKs and demonstrated that ERK-miR-142a-Ciapin1 axis played an essential role in CML pathogenesis.

The many facets of miR-223 in cancer: Oncosuppressor, oncogenic driver, therapeutic target, and biomarker of response

Given their intrinsic pleiotropism, microRNAs (miR) play complex biological roles, in both normal and pathological conditions. Often the same miR can act as oncogene or oncosuppressor, depending on the biological process dysregulated in each specific tissue. miR‐223 does not represent an exception to this rule and its functions greatly differ in different contexts. miR‐223 has been widely studied in the hematopoietic compartment, where it plays a central role in innate immune response, regulating myeloid differentiation and granulocytes function. Accordingly, dysregulated expression of miR‐223 has been associated to different inflammatory disorders and tumors arising from the immune compartment. Most carcinomas, breast cancer being the most studied, display loss of miR‐223. However, in gastro‐esophageal cancers miR‐223 is frequently overexpressed and correlates with worse prognosis. A link between miR‐223 and response to CDK4/6‐inhibitors has been recently proposed, suggesting a role as biomarker of therapeutic response. The notion that one of the most commonly mutated protein in cancer, mutant p53, binds the promoter of miR‐223 and suppresses its transcription, adds a further level of complexity to the full understanding of miR‐223 in cancer. In this review, we will summarize the current knowledge on the molecular networks that alter or are altered by miR‐223, in different cancer types. We will discuss if the times are ready for the exploitation of miR‐223 as predictive biomarker of treatment response or, even, as therapeutic target, in specific settings. Finally, we will suggest which could be the next steps to be taken for a realistic clinical application of miR‐223.

This article is categorized under:

RNA in Disease and Development > RNA in Disease

MiR-195 enhances cardiomyogenic differentiation of the proepicardium/septum transversum by Smurf1 and Foxp1 modulation

Cardiovascular development is a complex developmental process in which multiple cell lineages are involved, namely the deployment of first and second heart fields. Beside the contribution of these cardiogenic fields, extracardiac inputs to the developing heart are provided by the migrating cardiac neural crest cells and the proepicardial derived cells. The proepicardium (PE) is a transitory cauliflower-like structure located between the cardiac and hepatic primordia. The PE is constituted by an internal mesenchymal component surrounded by an external epithelial lining. With development, cells derived from the proepicardium migrate to the neighboring embryonic heart and progressive cover the most external surface, leading to the formation of the embryonic epicardium. Experimental evidence in chicken have nicely demonstrated that epicardial derived cells can distinctly contribute to fibroblasts, endothelial and smooth muscle cells. Surprisingly, isolation of the developing PE anlage and ex vivo culturing spontaneously lead to differentiation into beating cardiomyocytes, a process that is enhanced by Bmp but halted by Fgf administration. In this study we provide a comprehensive characterization of the developmental expression profile of multiple microRNAs during epicardial development in chicken. Subsequently, we identified that miR-125, miR-146, miR-195 and miR-223 selectively enhance cardiomyogenesis both in the PE/ST explants as well as in the embryonic epicardium, a Smurf1- and Foxp1-driven process. In addition we identified three novel long non-coding RNAs with enhanced expression in the PE/ST, that are complementary regulated by Bmp and Fgf administration and well as by microRNAs that selectively promote cardiomyogenesis, supporting a pivotal role of these long non coding RNAs in microRNA-mediated cardiomyogenesis of the PE/ST cells.

Salt-inducible kinase inhibition suppresses acute myeloid leukemia progression in vivo

Lineage-defining transcription factors (TFs) are compelling targets for leukemia therapy, yet they are among the most challenging proteins to modulate directly with small molecules. We previously used CRISPR screening to identify a salt-inducible kinase 3 (SIK3) requirement for the growth of acute myeloid leukemia (AML) cell lines that overexpress the lineage TF myocyte enhancer factor (MEF2C). In this context, SIK3 maintains MEF2C function by directly phosphorylating histone deacetylase 4 (HDAC4), a repressive cofactor of MEF2C. In this study, we evaluated whether inhibition of SIK3 with the tool compound YKL-05-099 can suppress MEF2C function and attenuate disease progression in animal models of AML. Genetic targeting of SIK3 or MEF2C selectively suppressed the growth of transformed hematopoietic cells under in vitro and in vivo conditions. Similar phenotypes were obtained when cells were exposed to YKL-05-099, which caused cell-cycle arrest and apoptosis in MEF2C-expressing AML cell lines. An epigenomic analysis revealed that YKL-05-099 rapidly suppressed MEF2C function by altering the phosphorylation state and nuclear localization of HDAC4. Using a gatekeeper allele of SIK3, we found that the antiproliferative effects of YKL-05-099 occurred through on-target inhibition of SIK3 kinase activity. Based on these findings, we treated 2 different mouse models of MLL-AF9 AML with YKL-05-099, which attenuated disease progression in vivo and extended animal survival at well-tolerated doses. These findings validate SIK3 as a therapeutic target in MEF2C-addicted AML and provide a rationale for developing druglike inhibitors of SIK3 for definitive preclinical investigation and for studies in human patients.

Methylation‑associated silencing of miR‑638 promotes endometrial carcinoma progression by targeting MEF2C

Promoter methylation‑associated silencing of cancer‑associated microRNAs (miRNAs) is a common epigenetic mechanism during tumorigenesis in various types of human cancer. However, this has not been comprehensively examined in endometrial carcinoma (EC). In the present study, an miRNA microarray consisting of 1,347 common human miRNAs was used to select potential tumor suppressive miRNAs that were hyper‑methylated in EC. This led to the identification of miR‑638, miR‑210 and miR‑3665. The methylation status of miR‑638 was examined by bisulfite sequencing polymerase chain reaction and miR‑638 expression was measured by TaqMan miRNA assays. EC cell lines transfected with vectors overexpressing miR‑638, its target gene myocyte enhancer factor 2C (MEF2C) or both, were constructed. Dual‑luciferase reporter assays, a xenograft mouse model and rescue experiments were designed to study miR‑638 and its target gene MEF2C. The results indicated that the promoter region of miR‑638 was highly methylated and the expression of miR‑638 was significantly downregulated in cancerous tissues from 42 patients with EC who underwent surgical resection. Additionally, a low expression of miR‑638 was significantly associated with advanced Federation of Gynecology and Obstetrics stage and was demonstrated to indicate shorter disease‑free survival. Functional studies indicated that the overexpression of miR‑638 in EC cell lines inhibited in vitro tumor progression and in vivo tumorigenicity. MEF2C was verified as a direct target of miR‑638 and was demonstrated to mediate the tumor‑suppressive function of miR‑638 in EC.

Functional Screening Identifies MicroRNAs as Multi-Cellular Regulators of Heart Failure

Heart failure (HF) is the leading cause of death in the Western world. Pathophysiological processes underlying HF development, including cardiac hypertrophy, fibrosis and inflammation, are controlled by specific microRNAs (miRNAs). Whereas most studies investigate miRNA function in one particular cardiac cell type, their multicellular function is poorly investigated. The present study probed 194 miRNAs –differentially expressed in cardiac inflammatory disease – for regulating cardiomyocyte size, cardiac fibroblasts collagen content, and macrophage polarization. Of the tested miRNAs, 13%, 26%, and 41% modulated cardiomyocyte size, fibroblast collagen production, and macrophage polarization, respectively. Seventeen miRNAs affected all three cellular processes, including miRNAs with established (miR-210) and unknown roles in cardiac pathophysiology (miR-145-3p). These miRNAs with a multi-cellular function commonly target various genes. In-depth analysis in vitro of previously unstudied miRNAs revealed that the observed phenotypical alterations concurred with changes in transcript and protein levels of hypertrophy-, fibrosis- and inflammation-related genes. MiR-145-3p and miR-891a-3p were identified to regulate the fibrotic response, whereas miR-223-3p, miR-486-3p, and miR-488-5p modulated macrophage activation and polarisation. In conclusion, miRNAs are multi-cellular regulators of different cellular processes underlying cardiac disease. We identified previously undescribed roles of miRNAs in hypertrophy, fibrosis, and inflammation, and attribute new cellular effects to various well-known miRNAs.

MEF-2 isoforms' (A-D) roles in development and tumorigenesis

Myocyte enhancer factor (MEF)-2 plays a critical role in proliferation, differentiation, and development of various cell types in a tissue specific manner. Four isoforms of MEF-2 (A-D) differentially participate in controlling the cell fate during the developmental phases of cardiac, muscle, vascular, immune and skeletal systems. Through their associations with various cellular factors MEF-2 isoforms can trigger alterations in complex protein networks and modulate various stages of cellular differentiation, proliferation, survival and apoptosis. The role of the MEF-2 family of transcription factors in the development has been investigated in various cell types, and the evolving alterations in this family of transcription factors have resulted in a diverse and wide spectrum of disease phenotypes, ranging from cancer to infection. This review provides a comprehensive account on MEF-2 isoforms (A-D) from their respective localization, signaling, role in development and tumorigenesis as well as their association with histone deacetylases (HDACs), which can be exploited for therapeutic intervention.

PTBP2 exon 10 inclusion is associated with the progression of CML and it is BCR-ABL1 dependent

Altered or aberrant expression of several splicing factors leads to the progression of different cancers. Though there are several ongoing studies underscoring the role of the splicing regulator polypyrimidine tract binding protein 2 (PTBP2) in neuronal cells, we unveil the role of PTBP2 in chronic myeloid leukemia (CML). Different RNA binding proteins (RBP's) earlier reported in chronic myeloid leukemia blast crisis (CML-BC) cases (n = 28) from Radich Oncomine leukemia dataset, were compared. We observed increased expression of MSI2 followed by PTBP2 in BC cases and increased PTBP2 expression in relapsed cases (n = 10) from the same dataset compared to other RBPs. We also observed increased PTBP2 exon 10 inclusion in KCL22, a granulocytic lineage CML cell line when compared to other CML cell lines of different lineages. As PTBP2 protein expression is associated with PTBP2 exon 10 inclusion, we observed in cell lines and in a set of progressed cases (n = 4) that increased BCR-ABL1 expression potentiates PTBP2 exon 10 inclusion and thus confers the existence of a functional protein. Inhibition of BCR-ABL1 with imatinib not only blocks the inclusion of exon 10 but also deregulates PTBP2 expression in CML cells. Knockdown of PTBP2 in KCL22 cells leads to reduced cell proliferation, increased G2/M cell cycle arrest and increased apoptosis. Taken together our study portrays PTBP2 as a new possible target for CML and progressive inclusion/exclusion of PTBP2 exon 10 might play an important role in CML progression.

MEF2C and CEBPA: Possible co-regulators in chronic myeloid leukemia disease progression

Chronic myelogenous leukemia (CML), a hematopoietic malignancy, characterized initially by a chronic phase (CP) progresses into blast crisis (BC) with the accumulation of secondary abnormalities. We have reported earlier that MEF2C, a target of miR-223, was significantly up regulated in CML and also showed a negative correlation with miR-223. In this study, gene expression arrays were used to identify the genes regulated by MEF2C during myelopoiesis. Statistical tools were used to understand the correlation between MEF2C and the targets in different phases of CML. Different CML cell lines and CML patient samples were treated with imatinib to study the effect of MEF2C on the target genes. We observed that MEF2C targets a set of myeloid genes including the myeloid transcription factor CEBPA. MEF2C and CEBPA expression patterns are negatively correlated in CML patient samples. We further show that the expression of MEF2C and CEBPA along with CSF3R is sufficient to molecularly classify different stages of CML. Imatinib, the drug of choice for CML, abrogates MEF2C expression and reverses CEBPA repression both in the cell line and the primary cells. We report the existence of a MEF2C and CEBPA correlation in CML disease progression.

Nanoparticle delivery of miR-223 to attenuate macrophage fusion

The foreign body response (FBR) begins with injury acquired during implantation of a biomaterial (BM) and is detrimental due to the eventual encapsulation of the implant. Fusion of macrophages to form foreign body giant cells (FBGC), a hallmark of the FBR, is the consequence of a multistep mechanism induced by interleukin (IL)-4 that includes the acquisition of a fusion competent state and subsequent cytoskeletal rearrangements. However, the precise mechanism, regulation, and interplay among molecular mediators to generate FBGCs are insufficiently understood. Seeking novel mediators of fusion that might be regulated at the post-transcriptional level, we examined the role of microRNAs (miRs) in this process. A miR microarray was screened and identified miR-223 as a negative regulator of macrophage fusion. In addition, transfection of primary macrophages with a mir-223 mimic attenuated IL-4-induced fusion. Furthermore, miR-223 KO mice and mir-223 deficient cells displayed increased fusion in vivo and in vitro, respectively. Finally, we developed a method for in vivo delivery of miR-223 mimic utilizing PLGA nanoparticles, which inhibited FBGC formation in a biomaterial implant model. Our results identify miR-223 as a negative regulator of fusion and demonstrate miR-223 mimic-loaded nanoparticles as a therapeutic inhibitor of macrophage fusion.

The implication of cancer progenitor cells and the role of epigenetics in the development of novel therapeutic strategies for chronic myeloid leukemia

SIGNIFICANCE

Chronic myeloid leukemia (CML) involves the malignant transformation of hematopoietic stem cells, defined largely by the Philadelphia chromosome and expression of the breakpoint cluster region-Abelson (BCR-ABL) oncoprotein. Pharmacological tyrosine kinase inhibitors (TKIs), including imatinib mesylate, have overcome limitations in conventional treatment for the improved clinical management of CML.

RECENT ADVANCES

Accumulated evidence has led to the identification of a subpopulation of quiescent leukemia progenitor cells with stem-like self renewal properties that may initiate leukemogenesis, which are also shown to be present in residual disease due to their insensitivity to tyrosine kinase inhibition.

CRITICAL ISSUES

The characterization of quiescent leukemia progenitor cells as a unique cell population in CML pathogenesis has become critical with the complete elucidation of mechanisms involved in their survival independent of BCR-ABL that is important in the development of novel anticancer strategies. Understanding of these functional pathways in CML progenitor cells will allow for their selective therapeutic targeting. In addition, disease pathogenesis and drug responsiveness is also thought to be modulated by epigenetic regulatory mechanisms such as DNA methylation, histone acetylation, and microRNA expression, with a capacity to control CML-associated gene transcription.

FUTURE DIRECTIONS

A number of compounds in combination with TKIs are under preclinical and clinical investigation to assess their synergistic potential in targeting leukemic progenitor cells and/or the epigenome in CML. Despite the collective promise, further research is required in order to refine understanding, and, ultimately, advance antileukemic therapeutic strategies.

De Novo Acute Myeloid Leukemia in Adults: Suppression of MicroRNA-223 is Independent of LMO2 Protein Expression BUT Associate With Adverse Cytogenetic Profile and Undifferentiated Blast Morphology

MicroRNA (MIR) signatures are critical to pathobiology and prognosis of acute myeloid leukemia (AML). MIR223 is expressed at low levels in progenitor cells, whereas high expression is induced by granulocytic differentiation. Novel-targeted therapies through epigenetic manipulation of MIR223 regulators are being explored in AML but correlative data between established clinical prognostic markers and MIR223 expression in AML is lacking. MIR223 has inverse relationship with LMO2 protein expression and our group has recently reported a close association between LMO2 protein expression and chromosomal findings in AML patients. In this study, we examined the expression of MIR223 in a large cohort of AML patients and correlated it with LMO2 protein expression, cytogenetic data, degree of differentiation [French-American and British (FAB)/World Health Organization classifications], and overall survival. MIR223 expression was upregulated in only a subset of patients (37%). Suppression of MIR223 was more frequent among patients with aneuploid karyotype compared with diploid karyotype (P=0.005). In AML, not otherwise specified category, AML with maturation (FAB-M2) showed higher levels of MIR223 when compared with either AML without maturation (FAB M0/M1) (P=0.001); AML with monoblastic differentiation (FAB M4/M5) (P=0.004) or AML with myelodysplasia-related changes (P=0.011). Among cytogenetic risk groups, suppression of MIR223 was universal (>95%) in high-risk group when compared with intermediate-risk group (P=0.004). No correlation between MIR223 and LMO2 protein expression was identified. In conclusion, we have shown that suppression of MIR223 expression, as compared with controls, is associated with lack of differentiation and adverse cytogenetic profile, but unrelated with LMO2 protein expression or overall survival.

Targeting the SMO oncogene by miR-326 inhibits glioma biological behaviors and stemness

BACKGROUND

Few studies have associated microRNAs (miRNAs) with the hedgehog (Hh) pathway. Here, we investigated whether targeting smoothened (SMO) with miR-326 would affect glioma biological behavior and stemness.

METHODS

To investigate the expression of SMO and miR-326 in glioma specimens and cell lines, we utilized quantitative real-time (qRT)-PCR, Western blot, immunohistochemistry, and fluorescence in situ hybridization. The luciferase reporter assay was used to verify the relationship between SMO and miR-326. We performed cell counting kit-8, transwell, and flow cytometric assays using annexin-V labeling to detect changes after transfection with siRNA against SMO or miR-326. qRT-PCR assays, neurosphere formation, and immunofluorescence were utilized to detect the modification of self-renewal and stemness in U251 tumor stem cells. A U251-implanted intracranial model was used to study the effect of miR-326 on tumor volume and SMO suppression efficacy.

RESULTS

SMO was upregulated in gliomas and was associated with tumor grade and survival period. SMO inhibition suppressed the biological behaviors of glioma cells. SMO expression was inversely correlated with miR-326 and was identified as a novel direct target of miR-326. miR-326 overexpression not only repressed SMO and downstream genes but also decreased the activity of the Hh pathway. Moreover, miR-326 overexpression decreased self-renewal and stemness and partially prompted differentiation in U251 tumor stem cells. In turn, the inhibition of Hh partially elevated miR-326 expression. Intracranial tumorigenicity induced by the transfection of miR-326 was reduced and was partially mediated by the decreased SMO expression.

CONCLUSIONS

This work suggests a possible molecular mechanism of the miR- 326/SMO axis, which can be a potential alternative therapeutic pathway for gliomas.

miR-223 is a coordinator of breast cancer progression as revealed by bioinformatics predictions

MicroRNAs are single-stranded non-coding RNAs that simultaneously down-modulate the expression of multiple genes post-transcriptionally by binding to the 3'UTRs of target mRNAs. Here we used computational methods to predict microRNAs relevant in breast cancer progression. Specifically, we applied different microRNA target prediction algorithms to various groups of differentially expressed protein-coding genes obtained from four breast cancer datasets. Six potential candidates were identified, among them miR-223, previously described to be highly expressed in the tumor microenvironment and known to be actively transferred into breast cancer cells. To investigate the function of miR-223 in tumorigenesis and to define its molecular mechanism, we overexpressed miR-223 in breast cancer cells in a transient or stable manner. Alternatively we overexpressed miR-223 in mouse embryonic fibroblasts or HEK293 cells and used their conditioned medium to treat tumor cells. With both approaches, we obtained elevated levels of miR-223 in tumor cells and observed decreased migration, increased cell death in anoikis conditions and augmented sensitivity to chemotherapy but no effect on adhesion and proliferation. The analysis of miR-223 predicted targets revealed enrichment in cell death and survival-related genes and in pathways frequently altered in breast cancer. Among these genes, we showed that protein levels for STAT5A, ITGA3 and NRAS were modulated by miR-223. In addition, we proved that STAT5A is a direct miR-223 target and highlighted a possible correlation between miR-223 and STAT5A in migration and chemotherapy response. Our investigation revealed that a computational analysis of cancer gene expression datasets can be a relevant tool to identify microRNAs involved in cancer progression and that miR-223 has a prominent role in breast malignancy that could potentially be exploited therapeutically.

Myocyte enhancer factor 2C in hematopoiesis and leukemia

MEF2C is a selectively expressed transcription factor involved in different transcriptional complexes. Originally identified as an essential regulator of muscle development, ectopic expression of MEF2C as a result of chromosomal rearrangements is now linked to leukemia. Specifically, high MEF2C expression has been linked to mixed lineage leukemia-rearranged acute myeloid leukemia as well as to the immature subgroup of T-cell acute lymphoblastic leukemia. This review focuses on the role of MEF2C in the hematopoietic system and on aberrant MEF2C expression in human leukemia.