MiR-101, downregulated in retinoblastoma, functions as a tumor suppressor in human retinoblastoma cells by targeting EZH2

Comprehensive review and in silico analysis of the role of noncoding RNAs in retinoblastoma: A step-toward ncRNA precision

Noncoding RNAs (ncRNAs) have greatly revolutionized our understanding of gene regulation and its main role in oncogenesis, particularly in retinoblastoma (RB), the most prevalent type of intraocular malignancy in children. Despite recent significant therapeutic advances, the prognosis for RB remains unclear owing to late diagnosis and resistance to conventional treatments. This review comprehensively explores the multiple roles of ncRNAs-microRNAs (miRNAs), long noncoding RNAs (lncRNAs), circular RNAs (circRNAs), and PIWI-interacting RNAs (piRNAs)-in RB pathogenesis. miRNA dysregulation serves as the initial cascade for modulating cell proliferation, apoptosis, and metastasis. Similarly, lncRNAs demonstrate dual behavior, functioning either as oncogenic drivers or tumor suppressors by interacting with several molecular targets and interacting with different signaling pathways, such as the PI3K/Akt and Wnt/β-catenin pathways. Additionally, circRNAs, owing to their persistent stability and unique ability to act as miRNA sponge main binding sites, affect various normal physiological processes, influencing tumor progression and chemoresistance. Emerging data also highlight the intricate crosstalk between piRNAs and other ncRNAs in retinal homeostasis and oncogenesis, with promising future implications for their utility as diagnostic biomarkers in liquid biopsy types. This comprehensive review consolidates the latest knowledge on the molecular mechanisms of noncoding RNAs (ncRNAs) in retinoblastoma (RB), along with in silico analysis of ncRNA-gene interactions, providing a guide for precision medical approaches. However, future research should aim to utilize ncRNAs as a vital clinical tool to improve the early diagnosis, prognosis, and targeted treatment of RB.

Tumor heterogeneity in retinoblastoma: a literature review

Tumor heterogeneity, characterized by the presence of diverse cell populations within a tumor, is a key feature of the complex nature of cancer. This diversity arises from the emergence of cells with varying genomic, epigenetic, transcriptomic, and phenotypic profiles over the course of the disease. Host factors and the tumor microenvironment play crucial roles in driving both inter-patient and intra-patient heterogeneity. These diverse cell populations can exhibit different behaviors, such as varying rates of proliferation, responses to treatment, and potential for metastasis. Both inter-patient heterogeneity and intra-patient heterogeneity pose significant challenges to cancer therapeutics and management. In retinoblastoma, while heterogeneity at the clinical presentation level has been recognized for some time, recent attention has shifted towards understanding the underlying cellular heterogeneity. This review primarily focuses on retinoblastoma heterogeneity and its implications for therapeutic strategies and disease management, emphasizing the need for further research and exploration in this complex and challenging area.

EZH2 Expression in Retinoblastoma: A Potential Therapeutic Target

INTRODUCTION

The enhancer of zeste homolog 2 (EZH2) is a member of the polycomb repressive complex 2 (PRC2) and is important in cell-cycle regulation. Increased expression of EZH2 has been reported in retinoblastoma (RB). The aim of the study was to determine EZH2 expression, compare this with clinicopathological parameters in RB, and assess its relationship with tumor cell proliferation.

METHODS

Ninety-nine retrospective cases of enucleated RB were included in the present study. Expression of EZH2 and the marker of cell proliferation, Ki67, were investigated by immunohistochemistry.

RESULTS

Among the 99 cases of RB in this study, EZH2 was found highly expressed (positive expression rate ≥70%) in 92 cases. EZH2 was expressed in tumor cells but absent in normal retinal tissues. The expression of EZH2 was positively linked to Ki67 expression (r = 0.65, p < 0.001).

CONCLUSION

Elevated EZH2 expression was found in most RB cases, indicating that EZH2 could be a potential therapeutic target for RB.

The role of EZH2 in ocular diseases: a narrative review

EZH2, acting as a catalytic subunit of PRC2 to catalyze lysine 27 in histone H3, induces the suppression of gene expression. EZH2 can regulate cell proliferation and differentiation of retinal progenitors, which are required for physiological retinal development. Meanwhile, an abnormal level of EZH2 has been observed in ocular tumors and other pathological tissues. This review summarizes the current knowledge on EZH2 in retinal development and ocular diseases, including inherited retinal diseases, ocular tumors, corneal injury, cataract, glaucoma, diabetic retinopathy and age-related retinal degeneration. We highlight the potential of targeting EZH2 as a precision therapeutic target in ocular diseases.

The role of EZH2 as a potential therapeutic target in retinoblastoma

Enhancer of zeste homolog 2 (EZH2) has been reported selectively expressed in postnatal human retinoblastoma (RB). While, the contribution of EZH2 in progression of RB and its clinical importance has not been clarified. Here, immunohistochemistry (IHC) was performed on tumor specimens from 53 RB patients. UNC1999 and GSK503, inhibitors targeting EZH2, were incubated with human RB cell line WERI-Rb-1 and Y79 to assess the role and mechanism of EZH2 in RB proliferation, metastasis and tumor glycolysis. Administration of UNC1999 in subcutaneous tumor model of RB was conducted. The results showed that highly expressed EZH2 in RB tissues was significantly associated with the poor overall survival. UNC1999 and GSK503 inhibited proliferation, migration, invasion and tumor glycolysis of RB. Results in mouse xenograft model confirmed the inhibitory effect of UNC1999 on tumor growth of RB and the regulation effect of EZH2 to STAT3/FoxO1 signaling pathway. Therefore, EZH2 is rewarding to study as a potential target for anti-RB treatment.

Role of non-coding RNAs and exosomal non-coding RNAs in retinoblastoma progression

Retinoblastoma (RB) is a rare aggressive intraocular malignancy of childhood that has the potential to affect vision, and can even be fatal in some children. While the tumor can be controlled efficiently at early stages, metastatic tumors lead to high mortality. Non-coding RNAs (ncRNAs) are implicated in a number of physiological cellular process, including differentiation, proliferation, migration, and invasion, The deregulation of ncRNAs is correlated with several diseases, particularly cancer. ncRNAs are categorized into two main groups based on their length, i.e. short and long ncRNAs. Moreover, ncRNA deregulation has been demonstrated to play a role in the pathogenesis and development of RB. Several ncRNAs, such as miR-491-3p, miR-613,and SUSD2 have been found to act as tumor suppressor genes in RB, but other ncRNAs, such as circ-E2F3, NEAT1, and TUG1 act as tumor promoter genes. Understanding the regulatory mechanisms of ncRNAs can provide new opportunities for RB therapy. In the present review, we discuss the functional roles of the most important ncRNAs in RB, their interaction with the genes responsible for RB initiation and progression, and possible future clinical applications as diagnostic and prognostic tools or as therapeutic targets.

Applications of Non-Coding RNAs in Patients With Retinoblastoma

Retinoblastoma (RB) is the most common primary intraocular malignancy in childhood. In the carcinogenic process of neoplasms such as RB, the role of non-coding RNAs (ncRNAs) has been widely demonstrated recently. In this review, we aim to provide a clinical overview of the current knowledge regarding ncRNAs in relation to RB. Although ncRNAs are now considered as potential diagnostic biomarkers, prognostic factors, and therapeutic targets, further studies will facilitate enhanced understanding of ncRNAs in RB physiopathology and define the roles ncRNAs can play in clinical practice.

Polycomb and Trithorax Group Proteins: The Long Road from Mutations in Drosophila to Use in Medicine

Polycomb group (PcG) and Trithorax group (TrxG) proteins are evolutionarily conserved factors responsible for the repression and activation of the transcription of multiple genes in Drosophila and mammals. Disruption of the PcG/TrxG expression is associated with many pathological conditions, including cancer, which makes them suitable targets for diagnosis and therapy in medicine. In this review, we focus on the major PcG and TrxG complexes, the mechanisms of PcG/TrxG action, and their recruitment to chromatin. We discuss the alterations associated with the dysfunction of a number of factors of these groups in oncology and the current strategies used to develop drugs based on small-molecule inhibitors.

Chromatin regulators in retinoblastoma: Biological roles and therapeutic applications

Retinoblastoma (RB) is a pediatric ocular tumor mostly occurring due to the biallelic loss of RB1 gene in the developing retina. Early studies of genomic aberrations in RB have provided a valuable insight into how RB can progress following the tumor-initiating RB1 mutations and have established a notion that inactivation of RB1 gene is critical to initiate RB but this causative genetic lesion alone is not sufficient for malignant progression. With the advent of high-throughput sequencing technologies, we now have access to the comprehensive genomic and epigenetic landscape of RB and have come to appreciate that RB tumorigenesis requires both genetic and epigenetic alterations that might be directly or indirectly driven by RB1 loss. This integrative perspective on RB tumorigenesis has inspired research efforts to better understand the types and functions of epigenetic mechanisms contributing to RB development, leading to the identification of multiple epigenetic regulators misregulated in RB in recent years. A complete understanding of the intricate network of genetic and epigenetic factors in modulation of gene expression during RB tumorigenesis remains a major challenge but would be crucial to translate these findings into therapeutic interventions. In this review, we will provide an overview of chromatin regulators identified to be misregulated in human RB among the numerous epigenetic factors implicated in RB development. For a subset of these chromatin regulators, recent findings on their functions in RB development and potential therapeutic applications are discussed.

miR-340 Exerts Suppressive Effect on Retinoblastoma Progression by Targeting KIF14

Purpose: This work aimed to investigate the influences of microRNA-340 (miR-340) on proliferation and apoptosis of retinoblastoma (RB) cells and explore its regulatory mechanism.

MATERIALS AND METHODS

miR-340 mimic and inhibitor were applied for up-regulating or inhibiting the expression of miR-340 in RB cell lines. Then, CCK-8 and AnnexinV-FITC/PI staining were used to measure cell proliferation and apoptosis, respectively. After that, luciferase assay was performed to affirm the direct targets of miR-340. Furthermore, qRT-PCR and western blotting assay were carried out to detect the levels of miR-340 and KIF14.

RESULTS

Our results indicated that the miR-340 was lowly expressed in RB cell lines, and up-regulation of miR-340 can decrease the proliferation and induce the apoptosis of RB cells. Moreover, we verified that miR-340 controls KIF14 expression, either directly or through a subsequent molecular cascade, and inversely related to its expression. The results obtained from the rescue assays presented that over-expression of KIF14 reversed the miR-340-mediated inhibition on malignant phenotype of RB cells.

CONCLUSIONS

Overall, we proved that miR-340 can decrease the proliferation and increase the apoptosis of RB cells, and its function in RB cells was at least partially achieved via down-regulation of KIF14, prompting that miR-340 was expected to supply a new direction for clinical therapy of RB in the future.

BMP-Induced MicroRNA-101 Expression Regulates Vascular Smooth Muscle Cell Migration

Proliferation and migration of vascular smooth muscle cells (VSMCs) are implicated in blood vessel development, maintenance of vascular homeostasis, and pathogenesis of vascular disorders. MicroRNAs (miRNAs) mediate the regulation of VSMC functions in response to microenvironmental signals. Because a previous study reported that miR-101, a tumor-suppressive miRNA, is a critical regulator of cell proliferation in vascular disease, we hypothesized that miR-101 controls important cellular processes in VSMCs. The present study aimed to elucidate the effects of miR-101 on VSMC function and its molecular mechanisms. We revealed that miR-101 regulates VSMC proliferation and migration. We showed that miR-101 expression is induced by bone morphogenetic protein (BMP) signaling, and we identified dedicator of cytokinesis 4 (DOCK4) as a novel target of miR-101. Our results suggest that the BMP–miR-101–DOCK4 axis mediates the regulation of VSMC function. Our findings help further the understanding of vascular physiology and pathology.

Biomarkers in retinoblastoma

Retinoblastoma (RB) is the most common intraocular malignancy of childhood caused by inactivation of the Rb genes. The prognosis of RB is better with an earlier diagnosis. Many diagnostic approaches and appropriate clinical treatments have been developed to improve clinical outcomes. However, limitations exist when utilizing current methods. Recently, many studies have identified identify new RB biomarkers which can be used in diagnosis, as prognostic indicators and may contribute to understanding the pathogenesis of RB and help determine specific treatment strategies. This review focuses on recent advances in the discovery of RB biomarkers and discusses their clinical utility and challenges from areas such as epigenetics, proteomics and radiogenomics.

miR-133a-3p promotes apoptosis and induces cell cycle arrest by targeting CREB1 in retinoblastoma

INTRODUCTION

Retinoblastoma (RB) is a malignant tumor that is derived from photoreceptors. It is common in children under 3 years old with a family genetic predisposition. MicroRNA-133a-3p (miR-133a-3p) is one of the tumor-related miRNAs that interprets a critical function in the genesis and development of various tumors. This study investigated the effects and underlying mechanisms of miR-133a-3p in RB.

MATERIAL AND METHODS

Quantitative reverse-transcription polymerase chain reaction (qRT-PCR) analysis was used to assess the miR-133a-3p expression in RB tissues and a cell model. MTT assay, western blot, flow cytometry and luciferase reporter assay were performed to evaluate the effect of miR-133a-3p on cell viability, apoptosis and the cell cycle. An RB xenograft model was established to assess the in vivo influence of miR-133a-3p on RB growth.

RESULTS

MiR-133a-3p level was reduced in RB tissues and the cell model (p < 0.01 or p < 0.001). Addition of miR-133a-3p reduced cell viability, and increased apoptosis and cell cycle arrest (p < 0.001). Additionally, CREB1 was identified to be the target of miR-133a-3p in RB cell lines (p < 0.001). Cell viability reduction, apoptosis and cell cycle arrest increases mediated by miR-133a-3p were attenuated by CREB1 overexpression (p < 0.001). MiR-133a-3p inhibited tumor growth of RB in vivo (p < 0.001).

CONCLUSIONS

Our results reveal that miR-133a-3p exhibits anti-cancer effects by targeting CREB1 in RB. This study provides a new direction for effective targeted treatment of this disease.

miR-224-5p protects dental pulp stem cells from apoptosis by targeting Rac1

Dental pulp stem cells (DPSCs) are reported to be enriched in stem/progenitor cells, however to the best of our knowledge they have yet to be well documented and characterized. In the present study, in order to characterize DPSCs and the effect of microRNAs (miRs/miRNAs) on DPSC properties, a miRNA array was performed between dental periodontal ligament cells (DPLCs) and DPSCs. The results revealed that miR-224-5p (miR-224) was highly expressed in the DPSCs compared with that in the DPLCs. The transfection of DPSCs with an miR-224 inhibitor impaired cell viability. In addition, miR-224 inhibition significantly promoted cell apoptosis in DPSCscompared with the NC group. In silico analysis and a dual-luciferase reporter assay demonstrated that miR-224 targets the 3′-untranslated region of the Rac family small GTPase 1 (Rac1) gene. miR-224 downregulation resulted in the increased expression of Rac1 in DPSCs compared with DPLCs. Furthermore, miR-224 inhibition caused augmented mitogen-activated protein kinase 8, caspase-3, caspase-9 and Fas ligand expression in DPSC, which may be recovered by Rac1 silencing with transfection with short hairpin RNA-Rac1. Furthermore, Annexin V-fluorescein isothiocyanate/propidium iodide flow cytometry indicated that the silencing of Rac1 restored the pro-apoptotic DPSC cell number with miR-224 transfection. Therefore, the results of the present study suggested miR-224 in DPSC serves an important function in protecting cells against apoptosis by downregulating Rac1 expression, and also identified miR-224 as a novel miRNA in regulating the features of DPSC.

Non-Coding RNAs in Pediatric Solid Tumors

Pediatric solid tumors are a diverse group of extracranial solid tumors representing approximately 40% of childhood cancers. Pediatric solid tumors are believed to arise as a result of disruptions in the developmental process of precursor cells which lead them to accumulate cancerous phenotypes. In contrast to many adult tumors, pediatric tumors typically feature a low number of genetic mutations in protein-coding genes which could explain the emergence of these phenotypes. It is likely that oncogenesis occurs after a failure at many different levels of regulation. Non-coding RNAs (ncRNAs) comprise a group of functional RNA molecules that lack protein coding potential but are essential in the regulation and maintenance of many epigenetic and post-translational mechanisms. Indeed, research has accumulated a large body of evidence implicating many ncRNAs in the regulation of well-established oncogenic networks. In this review we cover a range of extracranial solid tumors which represent some of the rarer and enigmatic childhood cancers known. We focus on two major classes of ncRNAs, microRNAs and long non-coding RNAs, which are likely to play a key role in the development of these cancers and emphasize their functional contributions and molecular interactions during tumor formation.

MicroRNA-224 enhances the osteoblastic differentiation of hMSCs via Rac1

Osteogenesis is the differentiation of mesenchymal stem cells (MSCs) into osteoblasts. MicroRNAs (miRNAs) are short noncoding RNAs that target specific genes to mediate translational activities. In this study, we investigated how miR-224 regulates the osteoblastic differentiation of human MSCs (hMSCs) as well as the underlying mechanism. The results revealed the upregulation of miR-224 during hMSC differentiation. In vitro experiments showed that the downregulation of miR-224 suppressed the differentiation of hMSCs into osteoblasts. However, upregulation of miR-224 was concomitant with increased expression of relevant genes and augmented activity of alkaline phosphatase. Furthermore, the results indicated that Rac1 acted as the bona fide target of miR-224 and that Rac1 depletion promoted osteogenic differentiation in miR-224-silenced hMSCs. In addition, we found that both JAK/STAT3 and Wnt/β-catenin pathways were repressed by Rac1 depletion using quantitative reverse transcription polymerase chain reaction (qRT-PCR), western blotting, and immunofluorescence. Our data indicate a novel molecular mechanism in relation to hMSCs differentiation into osteoblasts, which may facilitate bone anabolism via miR-224. SIGNIFICANCE OF THE STUDY: In this study, we mainly explored the effects of miR-224 on hMSCs differentiation into osteoblasts. We find that induced miR-224 expression in hMSCs is considered closely associated with specific osteogenesis-related genes, alkaline phosphatase activity, and matrix mineralization, indicating that miR-224 may serve as a promising biomarker for osteogenic differentiation. Our data indicate a novel molecular mechanism in relation to hMSCs differentiation into osteoblasts, which may facilitate bone anabolism via miR-224.

LncRNA XIST promotes the epithelial to mesenchymal transition of retinoblastoma via sponging miR-101

Accumulating evidence demonstrated that abnormal expression of long non-coding RNAs (lncRNAs) was closely associated with cancer development including retinoblastoma (RB). LncRNA X inactive specific transcript (XIST) has been found to function as an oncogene or a tumor suppressor in several cancers. However, the role and underlying mechanism of XIST in RB have not been clarified. The expression of XIST, microRNA (miR)- 101, zinc finger E-box binding homeobox (ZEB) 1, and ZEB2 was detected in human RB tissues and cell lines. The effects of XIST on the proliferation, migration, invasion, epithelial to mesenchymal transition (EMT), and apoptosis of RB cells were evaluated after downregulation of XIST. Furthermore, the mechanism of XIST was mainly focused on miR-101/ZEB1 or ZEB2 signaling. We found the expression of XIST, ZEB1 and ZEB2 was increased, whereas miR-101 was reduced in RB tissues and cells. Knockdown of XIST significantly suppressed the proliferation, migration, invasion and EMT, but promoted the apoptosis and caspase-3 activity. Moreover, we found that XIST functioned as a competing endogenous RNA (ceRNA) for miR-101 to regulate the de-repression of its endogenous targets ZEB1 and ZEB2. In conclusion, these findings suggest that XIST may facilitate the progression of RB through acting as a ceRNA for miR-101 to mediate the expression of ZEB1 and ZEB2. This may provide novel therapeutic options for RB.

MicroRNA‑93‑5p promotes the progression of human retinoblastoma by regulating the PTEN/PI3K/AKT signaling pathway

Numerous reports have indicated that microRNA‑93‑5p (miR‑93‑5p) is involved in the development and progression of human cancer, including non‑small cell lung, gastric and breast cancer; however, the role of miR‑93‑5p in retinoblastoma (RB) remains unknown. In the present study, it was reported that miR‑93‑5p expression levels were significantly upregulated in RB tissues compared with in normal tissues by reverse transcription‑quantitative polymerase chain reaction. Furthermore, it was demonstrated via cell counting kit‑8 and Transwell assays that knockdown of miR‑93‑5p significantly suppressed the proliferation, migration and invasion of RB cells, but promoted cellular apoptosis. Regarding the underlying mechanism, the present study reported that phosphatase and tensin homolog (PTEN) was a direct target of miR‑93‑5p in RB cells. Overexpression of miR‑93‑5p significantly inhibited the expression of PTEN; opposing results were observed when PTEN expression was downregulated. Furthermore, the present study revealed that PTEN expression levels were downregulated and were inversely correlated with that of miR‑93‑5p in RB tissues. Additionally, the present study demonstrated that knockdown of PTEN in miR‑93‑5p‑depleted RB cells significantly reversed the effects of miR‑93‑5p on cell proliferation, migration and invasion; miR‑93‑5p knockdown was suggested to promote PTEN expression, consequently inhibiting the activation of phosphoinositide 3‑kinase (PI3K)/protein kinase B (AKT) signaling pathway. Collectively, the results of the present study demonstrated that miR‑93‑5p may serve a role as an oncogene by modulating the PTEN/PI3K/AKT signaling pathway in RB, indicating that miR‑93‑5p may be a potential therapeutic target for the treatment of RB.

miR-101-3p induces autophagy in endometrial carcinoma cells by targeting EZH2

OBJECTIVE

This study aimed to investigate the effect of miR-101-3p on autophagy in endometrial carcinoma (EC) cells and the connection between miR-101-3p and EZH2.

METHODS

The expression levels of miRNAs were analyzed by microarray. The expression level of autophagy related proteins was measured by western blot. The mRNA expression level of beclin-1 was determined by qRT-PCR. Autophagy in EC cells was traced by GFP-LC3 fusion protein and observed by fluorescence microscopy. The number of autophagic vacuoles was determined by transmission electron microscopy (TEM). A luciferase reporter assay was utilized to assess the target relationship between miR-101-3p and EZH2.

RESULTS

The expression level of miR-101-3p in EC tissues was lower than in normal tissues. miR-101-3p upregulated the expression levels of the autophagy-related proteins LC3-II and beclin-1 in EC cells in a time- and dose-dependent manner. Overexpression of miR-101-3p and silencing of EZH2 both promoted autophagy in EC cells. Luciferase reporter assays verified that miR-101-3p inhibited EZH2 expression by binding to its 3'-UTR region.

CONCLUSION

miR-101-3p promoted autophagy in EC cells by downregulating the expression of EZH2, and it induced autophagy in EC cells by suppressing EZH2 expression. Inhibition of miR-101-3p could reduce its autophagy induction effect on EC cells.

MicroRNAs in retinoblastoma: Potential diagnostic and therapeutic biomarkers

Retinoblastoma (Rb) is known as one of important childhood malignancies which due to inactivation of the RB gene (tumor suppressor gene in various patients). The early detection of Rb could provide better treatment for Rb patients. Imaging techniques (e.g., MRI and CT) are known as one of effective diagnosis approaches for detection of patients with Rb. It has been shown that utilization of imaging techniques is associated with some limitations. Hence, identification of new diagnosis approaches might provide a better treatment for Rb patients. Identification of new biomarkers could contribute to better understanding of pathogenesis events involved in Rb and provide new insights into design better treatment approaches for these patients. Among the various biomarkers, microRNAs (miRNAs) have emerged as attractive tools for Rb detection. miRNAs are one classes of small non-coding RNAs which could anticipate in a variety of biological process via targeting sequence of cellular and molecular pathways. Deregulations of these molecules are associated with cancerous condition. Multiple lines of evidence indicated that deregulation of various miRNAs involved in various stages of Rb. Here, we summarized a variety of tissue-specific and circulating miRNAs involved in Rb pathogenesis which could be used as diagnostic, prognostic, and therapeutic biomarkers in Rb patients.

Polycomb Repressor Complex 2 in Genomic Instability and Cancer

Polycomb repressor complexes PRC1 and PRC2 regulate chromatin compaction and gene expression, and are widely recognized for their fundamental contributions to developmental processes. Herein, we summarize the existing evidence and molecular mechanisms linking PRC-mediated epigenetic aberrations to genomic instability and malignancy, with a particular focus on the role of deregulated PRC2 in tumor suppressor gene expression, the DNA damage response, and the fidelity of DNA replication. We also discuss some of the recent advances in the development of pharmacological and dietary interventions affecting PRC2, which point to promising applications for the prevention and management of human malignancies.

MicroRNA-320 inhibits cell proliferation, migration and invasion in retinoblastoma by targeting specificity protein 1

Research into the expression and function of microRNAs (miRNAs/miR) in human cancer has provided novel insights into the molecular mechanisms underlying carcinogenesis and cancer progression. Aberrant miRNA expression has been reported in retinoblastoma (RB) and several other types of human cancer. The present study demonstrated that miR‑320 is significantly downregulated in RB tissues and cell lines. Furthermore, overexpression of miR‑320 was demonstrated to inhibit proliferation, migration and invasion of RB cells. Bioinformatic analysis identified specificity protein 1 (SP1) as a potential target gene of miR‑320. Luciferase reporter assay confirmed that the SP1 3'‑untranslated region contains a direct binding site for miR‑320, and restoration of miR‑320 expression decreased the mRNA and protein expression levels of SP1. Notably, SP1 silencing induced a similar effect on the proliferation, migration and invasion of RB cells as that observed with miR‑320 overexpression, further supporting the hypothesis that SP1 is a direct functional target of miR‑320 in RB. In conclusion, these findings indicate that miR‑320 may be an effective therapeutic target for the treatment of RB.

MiR-101 Targets the EZH2/Wnt/β-Catenin the Pathway to Promote the Osteogenic Differentiation of Human Bone Marrow-Derived Mesenchymal Stem Cells

Mounting evidence indicates that microRNAs (miRNAs) are involved in multiple processes of osteogenic differentiation. MicroRNA-101 (miR-101), identified as a tumor suppressor, has been implicated in the pathogenesis of several types of cancer. However, the expression of miR-101 and its roles in the osteogenic differentiation of human bone marrow-derived mesenchymal stem cells (hBMSCs) remain unclear. We found that the miR-101 expression level was significantly increased during the osteogenic differentiation of hBMSCs. MiR-101 depletion suppressed osteogenic differentiation, whereas the overexpression of miR-101 was sufficient to promote this process. We further demonstrated that enhancer of zeste homolog 2 (EZH2) was a target gene of miR-101. EZH2 overexpression and depletion reversed the promoting or suppressing effect of osteogenic differentiation of hBMSCs, respectively, caused by miR-101. In addition, we showed that miR-101 overexpression promoted the expression of Wnt genes, resulting in the activation of the Wnt/β-catenin signaling pathway by targeting EZH2, while the activity of β-catenin and the Wnt/β-catenin signaling pathway was inhibited by ICG-001, a β-Catenin inhibitor, which reversed the promoting effect of miR-101. Finally, miR-101 also promotes in vivo bone formation by hBMSCs. Collectively, these data suggest that miR-101 is induced by osteogenic stimuli and promotes osteogenic differentiation at least partly by targeting the EZH2/Wnt/β-Catenin signaling pathway.

Epigenetic regulation of human retinoblastoma

Retinoblastoma is a rare type of eye cancer of the retina that commonly occurs in early childhood and mostly affects the children before the age of 5. It occurs due to the mutations in the retinoblastoma gene (RB1) which inactivates both alleles of the RB1. RB1 was first identified as a tumor suppressor gene, which regulates cell cycle components and associated with retinoblastoma. Previously, genetic alteration was known as the major cause of its occurrence, but later, it is revealed that besides genetic changes, epigenetic changes also play a significant role in the disease. Initiation and progression of retinoblastoma could be due to independent or combined genetic and epigenetic events. Remarkable work has been done in understanding retinoblastoma pathogenesis in terms of genetic alterations, but not much in the context of epigenetic modification. Epigenetic modifications that silence tumor suppressor genes and activate oncogenes include DNA methylation, chromatin remodeling, histone modification and noncoding RNA-mediated gene silencing. Epigenetic changes can lead to altered gene function and transform normal cell into tumor cells. This review focuses on important epigenetic alteration which occurs in retinoblastoma and its current state of knowledge. The critical role of epigenetic regulation in retinoblastoma is now an emerging area, and better understanding of epigenetic changes in retinoblastoma will open the door for future therapy and diagnosis.

MicroRNA-101 inhibits cell proliferation and induces apoptosis by targeting EYA1 in breast cancer

MicroRNAs (miRNAs or miRs) regulate gene expression by negatively modulating the stability or translational efficiency of their target genes by targeting the 3'-untranslated region (3'-UTR). Aberrant miRNA expression has been reported in various types of cancer; miRNAs can function as either oncogenes or tumor suppressor genes in cancer. In this study, we examined the expression level of miR‑101 in breast cancer tissues and cell lines by RT-qPCR, and found that miR‑101 expression was downregulated in breast cancer tissues and cell lines; indeed, in 6 of the 28 tissue samples, miR‑101 could not be detected. Furthermore, miR‑101, when transfected into SKBR3 cells, inhibited cell proliferation and promoted apoptosis, while miR‑101 inhibitor had the opposite effect. A dual-luciferase reporter assay revealed that miR‑101 targeted the 3'-UTR of eyes absent homolog 1 (Drosophila) (EYA1). Western blot analysis demonstrated a significantly decreased protein level of EYA1 in the SKBR3 cells transfected with miR‑101 mimic, whereas transfection with miR‑101 inhibitor led to an increased level of EYA1. Moreover, an increased expression of EYA1 was also found in breast cancer tissues and cell lines. The silencing of EYA1 using siRNA targeting EYA1 (EYA1‑siRNA) significantly inhibited SKBR3 cell proliferation and promoted apoptosis, and also suppressed the increased proliferation induced by transfection with miR‑101 inhibitor. The protein expression levels of Notch signaling components (jagged1, Hes1 and Hey1) were significantly decreased by transfection with miR‑101 mimic and EYA1-siRNA, and were increased by transfection with miR‑101 inhibitor. Furthermore, the elevated protein expression levels of jagged1, Hes1 and Hey1 induced by transfection with miR‑101 inhibitor in the SKBR3 cells were significantly decreased by transfection with EYA1-siRNA. Taken together, these results suggest that miR‑101 is down-regulated in breast cancer, and can inhibit cell proliferation and promote apoptosis by targeting EYA1 through the Notch signaling pathway.

Suppression of microRNA-125a-5p upregulates the TAZ-EGFR signaling pathway and promotes retinoblastoma proliferation

Retinoblastoma is the most common intraocular malignancy that occurs during childhood; however, the mechanism underlying retinoblastoma proliferation and progression remains unclear. MicroRNAs (miRNAs) play an important role in the regulation of a myriad of biological processes in various types of cancer. In this study, we performed microarray analysis followed by qRT-PCR using four classes of retinoblastoma tissues with increasing cTNM classification stages to identify crucial miRNAs whose expression was correlated with retinoblastoma progression. miR-125a-5p was downregulated, and its expression levels were inversely correlated with cell proliferation in retinoblastoma compared with adjacent non-tumor retinal tissues. The overexpression of miR-125a-5p significantly suppressed cell proliferation and tumor formation in retinoblastoma. We further identified the transcriptional co-activator with PDZ binding motif (TAZ) as a direct target of miR-125a-5p. Importantly, TAZ levels were inversely correlated with miRNA-125a-5p expression, and TAZ promoted retinoblastoma cell proliferation. Moreover, the overexpression of miR-125a-5p led to a decrease in TAZ expression and downstream EGFR signaling pathway activation both in vitro and vivo. Finally, TAZ overexpression in retinoblastoma cells overexpressing miR-125a-5p restored retinoblastoma cell proliferation and EGFR pathway activation. Taken together, our data demonstrated that miR-125a-5p functions as an important tumor suppressor that suppresses the EGFR pathway by targeting TAZ to inhibit tumor progression in retinoblastoma. Thus, the miR-125a-5p/TAZ/EGFR axis may be a potential therapeutic target for retinoblastoma.

Gga-miR-101-3p Plays a Key Role in Mycoplasma gallisepticum (HS Strain) Infection of Chicken

Mycoplasma gallisepticum (MG), one of the most pathogenic Mycoplasma, has caused tremendous economic loss in the poultry industry. Recently, increasing evidence has suggested that micro ribonucleic acids (miRNAs) are involved in microbial pathogenesis. However, little is known about potential roles of miRNAs in MG infection of chicken. In the present study, using miRNA Solexa sequencing we have found that gga-miR-101-3p was up-regulated in the lungs of MG-infected chicken embryos. Moreover, gga-miR-101-3p regulated expression of the host enhancer of zeste homolog 2 (EZH2) through binding to the 3’ un-translated region (3’-UTR) of EZH2 gene. Over-expression of gga-miR-101-3p significantly inhibited EZH2 expression and hence inhibited proliferation of chicken embryonic fibroblast (DF-1 cells) by blocking the G1-to-S phase transition. Similar results were obtained in MG-infected chicken embryos and DF-1 cells, where gga-miR-101-3p was significantly up-regulated, while EZH2 was significantly down-regulated. This study reveals that gga-miR-101-3p plays an important role in MG infection through regulation of EZH2 expression and provides a new insight into the mechanisms of MG pathogenesis.

Cyclooxygenase-2, a Potential Therapeutic Target, Is Regulated by miR-101 in Esophageal Squamous Cell Carcinoma

BACKGROUND & AIMS

Cyclooxygenase-2 (COX-2) is known to promote the carcinogenesis of esophageal squamous cell carcinoma (ESCC). There are no reports on whether microRNAs (miRNAs) regulate COX-2 expression in ESCC. This study investigated the effect of miR-101 on ESCC through modulating COX-2 expression in ESCC.

METHODS

Real-time quantitative reverse transcription-polymerase chain reaction (RT-PCR) was used to quantify miR-101 expression in ESCC clinical tissues and cell lines. The effects of miR-101 on ESCC progression were evaluated by cell counting kit-8 (CCK8), transwell migration and invasion assays, as well as by flow cytometry. The COX-2 and PEG2 levels were determined by western blot and enzyme-linked immunosorbent assays (ELISA). The luciferase reporter assay was used to verify COX-2 as a direct target of miR-101. The anti-tumor activity of miR-101 in vivo was investigated in a xenograft nude mouse model of ESCC.

RESULTS

Downregulation of miR-101 was confirmed through comparison of 30 pairs of ESCC tumor and adjacent normal tissues (P < 0.001), as well as in 11 ESCC cell lines and a human immortalized esophageal cell line (P < 0.001). Transfection of miR-101 in ESCC cell lines significantly suppressed cell proliferation, migration, and invasion (all P < 0.001). The antitumor effect of miR-101 was verified in a xenograft model. Furthermore, COX-2 was shown to be a target of miR-101.

CONCLUSIONS

Overexpression of miR-101 in ESCC inhibits proliferation and metastasis. Therefore, the miR-101/COX-2 pathway might be a therapeutic target in ESCC.

Characterization and pharmacologic targeting of EZH2, a fetal retinal protein and epigenetic regulator, in human retinoblastoma

Retinoblastoma (RB) is the most common primary intraocular cancer in children, and the third most common cancer overall in infants. No molecular-targeted therapy for this lethal tumor exists. Since the tumor suppressor RB1, whose genetic inactivation underlies RB, is upstream of the epigenetic regulator EZH2, a pharmacologic target for many solid tumors, we reasoned that EZH2 might regulate human RB tumorigenesis. Histologic and immunohistochemical analyses were performed using an EZH2 antibody in sections from 43 samples of primary, formalin-fixed, paraffin-embedded human RB tissue, cryopreserved mouse retina, and in whole cell lysates from human RB cell lines (Y79 and WERI-Rb1), primary human fetal retinal pigment epithelium (RPE) and fetal and adult retina, mouse retina and embryonic stem (ES) cells. Although enriched during fetal human retinal development, EZH2 protein was not present in the normal postnatal retina. However, EZH2 was detected in all 43 analyzed human RB specimens, indicating that EZH2 is a fetal protein expressed in postnatal human RB. EZH2 expression marked single RB cell invasion into the optic nerve, a site of invasion whose involvement may influence the decision for systemic chemotherapy. To assess the role of EZH2 in RB cell survival, human RB and primary RPE cells were treated with two EZH2 inhibitors (EZH2i), GSK126 and SAH-EZH2 (SAH). EZH2i impaired intracellular adenosine triphosphate (ATP) production, an indicator of cell viability, in a time and dose-dependent manner, but did not affect primary human fetal RPE. Thus, aberrant expression of a histone methyltransferase protein is a feature of human RB. This is the first time this mechanism has been implicated for an eye, adnexal, or orbital tumor. The specificity of EZH2i toward human RB cells, but not RPE, warrants further in vivo testing in animal models of RB, especially those EZH2i currently in clinical trials for solid tumors and lymphoma.

MicroRNA-101 suppresses migration and invasion via targeting vascular endothelial growth factor-C in hepatocellular carcinoma cells

MicroRNAs (miRNAs) are a class of non-coding RNAs 18-25 nucleotides in length, which play important roles in the regulation of cancer progression through gene silencing. miRNA (miR)-101 has been suggested to be associated with hepatocellular carcinoma (HCC). However, the detailed role of miR-101 in HCC metastasis and the underlying mechanism remain largely unclear. The present study demonstrated that the expression of miR-101 was significantly reduced in HCC tissues compared with that in matched normal adjacent tissues. miR-101 was also found to be downregulated in four HCC cell lines compared with its expression in a normal liver cell line. Vascular endothelial growth factor (VEGF)-C was further identified as a direct target of miR-101, and the protein expression of VEGF-C was downregulated by miR-101 in HepG2 HCC cells. Furthermore, the overexpression of miR-101 and the knockdown of VEGF-C significantly inhibited HepG2 cell migration and invasion, while restoration of VEGF-C reversed the inhibitory effect of miR-101 overexpression on HepG2 cell migration and invasion. Finally, the expression of VEGF-C was notably increased in HCC tissues and cell lines. These findings suggest that miR-101 exerts a suppressive effect on HCC cell migration and invasion, at least in part through the direct inhibition of VEGF-C protein expression. Therefore, the miR-101/VEGF-C axis may serve as a potential therapeutic target for HCC metastasis.

Activation of SAPK/JNK mediated the inhibition and reciprocal interaction of DNA methyltransferase 1 and EZH2 by ursolic acid in human lung cancer cells

BACKGROUND

Ursolic acid (UA), a pentacyclic triterpenoid, is known to have anti-tumor activity in various cancers including human non small cell lung cancer (NSCLC). However, the molecular mechanisms underlying the action of UA remain largely unknown.

METHODS

Cell viability was measured by MTT assays. Apoptosis was analyzed with Annexin V-FITC/PI Apoptosis Detection Kit by Flow cytometry. Western blot analysis was performed to measure the phosphorylation and protein expression of stress-activated protein kinase/c-Jun N-terminal kinase (SAPK/JNK), DNMT1 [DNA (cytosine-5)-methyltransferase 1], enhancer of zeste 2 polycomb repressive complex 2 subunit (EZH2) and SP1. Exogenous expression of SP1 and DNMT1 was carried out by transient transfection assays.

RESULTS

We showed that UA inhibited the growth and induced apoptosis of NSCLC cells in the dose- and time-dependent fashion. Furthermore, we found that UA induced phosphorylation of SAPK/JNK and suppressed the protein expression of DNMT1 and EZH2. The inhibitor of SAPK/JNK (SP600125) blocked the UA-reduced expression of DNMT1 and EZH2. In addition, UA suppressed the expression of SP1 protein. Conversely, overexpression of SP1 reversed the effect of UA on DNMT1 and EZH2 expression, and feedback attenuated UA-induced phosphorylation of SAPK/JNK. Moreover, exogenous expression of DNMT1 antagonized the effect of UA on SAPK/JNK signaling, EZH2 protein expression, and NSCLC cell growth.

CONCLUSION

Our results show that UA inhibits growth of NSCLC cells through SAPK/JNK-mediated inhibition of SP1; this in turn results in inhibition the expression of DNMT1 and EZH2. Overexpression of DNMT1 diminishes UA-reduced EZH2 protein expression. The negative feedback regulation of SAPK/JNK signaling by SP1 and DNMT1, and the reciprocal interaction of EZH2 and DNMT1 contribute to the overall effects of UA. This study leads to important new insights into the mechanisms by which UA controls growth of NSCLC cells.

MicroRNA-101 inhibits the migration and invasion of intrahepatic cholangiocarcinoma cells via direct suppression of vascular endothelial growth factor-C

MicroRNAs (miRs) have important roles in the pathogenesis of human malignancy. It has previously been suggested that deregulation of miR‑101 is associated with the progression of intrahepatic cholangiocarcinoma (ICC); however, the exact role of miR‑101 in the regulation of ICC metastasis remains largely unknown. The present study demonstrated that the expression levels of miR‑101 were significantly decreased in ICC tissue, as compared with matched adjacent normal tissue. Furthermore, miR‑101 was downregulated in the ICC‑9810 human ICC cell line, as compared with in the normal human intrahepatic biliary epithelial cell (HIBEC) line. Vascular endothelial growth factor (VEGF)‑C was identified as a target gene of miR‑101 in ICC‑9810 cells. The expression of VEGF‑C was negatively regulated by miR‑101 at the post‑transcriptional level in ICC‑9810 cells. Further investigation demonstrated that overexpression of miR‑101 markedly suppressed the migration and invasion of ICC‑9810 cells, and these effects were similar to those observed following VEGF‑C knockdown. Conversely, restoration of VEGF‑C reversed the inhibitory effects of miR‑101 overexpression on ICC‑9810 cell migration and invasion, thus suggesting that miR‑101 may suppress ICC‑9810 cell migration and invasion, at least partly via inhibition of VEGF‑C. It was also demonstrated that the mRNA and protein expression levels of VEGF‑C were frequently upregulated in ICC tissue and cells, and its expression level was inversely correlated with that of miR‑101 in ICC tissue. In conclusion, the present study identified important roles for miR‑101 and VEGF‑C in ICC, suggesting that miR‑101/VEGF‑C signaling may be a promising diagnostic and/or therapeutic target for ICC.

MicroRNA-101 is repressed by EZH2 and its restoration inhibits tumorigenic features in embryonal rhabdomyosarcoma

Background

Rhabdomyosarcoma (RMS) is a pediatric soft tissue sarcoma arising from myogenic precursors that have lost their capability to differentiate into skeletal muscle. The polycomb-group protein EZH2 is a Lys27 histone H3 methyltransferase that regulates the balance between cell proliferation and differentiation by epigenetically silencing muscle-specific genes. EZH2 is often over-expressed in several human cancers acting as an oncogene. We previously reported that EZH2 inhibition induces cell cycle arrest followed by myogenic differentiation of RMS cells of the embryonal subtype (eRMS). MiR-101 is a microRNA involved in a negative feedback circuit with EZH2 in different normal and tumor tissues. To that, miR-101 can behave as a tumor suppressor in several cancers by repressing EZH2 expression. We, therefore, evaluated whether miR-101 is de-regulated in eRMS and investigated its interplaying with EZH2 as well as its role in the in vitro tumorigenic potential of these tumor cells.

Results

Herein, we report that miR-101 is down-regulated in eRMS patients and in tumor cell lines compared to their controls showing an inverse pattern of expression with EZH2. We also show that miR-101 is up-regulated in eRMS cells following both genetic and pharmacological inhibition of EZH2. In turn, miR-101 forced expression reduces EZH2 levels as well as restrains the migratory potential of eRMS cells and impairs their clonogenic and anchorage-independent growth capabilities. Finally, EZH2 recruitment to regulatory region of miR-101-2 gene decreases in EZH2-silenced eRMS cells. This phenomenon is associated to reduced H3K27me3 levels at the same regulatory locus, indicating that EZH2 directly targets miR-101 for repression in eRMS cells.

Conclusions

Altogether, our data show that, in human eRMS, miR-101 is involved in a negative feedback loop with EZH2, whose targeting has been previously shown to halt eRMS tumorigenicity. They also demonstrate that the re-induction of miR-101 hampers the tumor features of eRMS cells. In this scenario, epigenetic dysregulations confirm their crucial role in the pathogenesis of this soft tissue sarcoma.

Electronic supplementary material

The online version of this article (doi:10.1186/s13148-015-0107-z) contains supplementary material, which is available to authorized users.

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.

Long non-coding RNA BANCR regulates growth and metastasis and is associated with poor prognosis in retinoblastoma

Recent evidence shows that BRAF-activated non-coding RNA (BANCR) acts as a critical role in the proliferation and metastasis in malignant melanoma and lung cancer; however, little is known about the significance of lncRNA BANCR in retinoblastoma. The purpose of our study is to explore the role of lncRNA BANCR in retinoblastoma clinical samples and cell lines. The expression of lncRNA BANCR was measured in 60 retinoblastoma samples and normal retina samples by using RT-PCR. The effects of lncRNA BANCR on cell proliferation, migration, and invasion were also explored. In our results, lncRNA BANCR is overexpressed in retinoblastoma tissues and cell lines and is associated with tumor size, choroidal invasion, and optic nerve invasion. Moreover, patients with high levels of lncRNA BANCR expression had poorer survival than those with lower levels of lncRNA BANCR expression. Multivariate analysis showed that increased lncRNA BANCR expression was a poor independent prognostic factor for retinoblastoma patients. Furthermore, knocking down lncRNA BANCR expression significantly suppressed the retinoblastoma cell proliferation, migration, and invasion in vitro. In conclusion, lncRNA BANCR plays a significant role in retinoblastoma aggressiveness and prognosis and may act as a promising target for therapeutic strategy and prognostic prediction.

MiR-204, down-regulated in retinoblastoma, regulates proliferation and invasion of human retinoblastoma cells by targeting CyclinD2 and MMP-9

Aberrant expression of miR-204 had been frequently reported in cancer studies; however, the mechanism of its function in retinoblastoma remained unknown. Here, we reported that miR-204 was frequently downregulated in retinoblastoma tissues and cell lines. Enforced expression of miR-204 inhibited retinoblastoma cells' proliferation and invasion. In vivo study indicated that restoration of miR-204 inhibited tumor growth. CyclinD2 and MMP-9 were identified as potential targets of miR-204. In addition, a reverse correlation between miR-204 and CyclinD2 or MMP-9 expression was noted in retinoblastoma tissues. Taken together, our results identified a crucial tumor suppressive role of miR-204 in the progression of retinoblastoma.