Differential Maturation of miR-17 ~ 92 Cluster Members in Human Cancer Cell Lines

Post-transcriptional regulation of polycistronic microRNAs

An important proportion of microRNA (miRNA) genes tend to lie close to each other within animal genomes. Such genomic organization is generally referred to as miRNA clusters. Even though many miRNA clusters have been greatly studied, most attention has been usually focused on functional impacts of clustered miRNA co-expression. However, there is also another compelling aspect about these miRNA clusters, their polycistronic nature. Being transcribed on a single RNA precursor, polycistronic miRNAs benefit from common transcriptional regulation allowing their coordinated expression. And yet, numerous reports have revealed striking discrepancies in the accumulation of mature miRNAs produced from the same cluster. Indeed, the larger polycistronic transcripts can act as platforms providing unforeseen post-transcriptional regulatory mechanisms controlling individual miRNA processing, thus leading to differential miRNA expression, and sometimes even challenging the general assumption that polycistronic miRNAs are co-expressed. In this review, we aim to address the current knowledge about how miRNA polycistrons are post-transcriptionally regulated. In particular, we will focus on the mechanisms occurring at the level of the primary transcript, which are highly relevant for individual miRNA processing and as such have a direct repercussion on miRNA function within the cell. This article is categorized under: RNA Processing > Processing of Small RNAs Regulatory RNAs/RNAi/Riboswitches > Biogenesis of Effector Small RNAs RNA Interactions with Proteins and Other Molecules > RNA-Protein Complexes.

The dual role of microRNA (miR)-20b in cancers: Friend or foe?

MicroRNAs, as non-coding transcripts, modulate gene expression through RNA silencing under normal physiological conditions. Their aberrant expression has strongly associated with tumorigenesis and cancer development. MiR-20b is one of the crucial miRNAs that regulate essential biological processes such as cell proliferation, apoptosis, autophagy, and migration. Deregulated levels of miR-20b contribute to the early- and advanced stages of cancer. On the other hand, investigations emphasize the tumor suppressor ability of miR-20b. High-throughput strategies are developed to identify miR-20b potential targets, providing the proper insight into its molecular mechanism of action. Moreover, accumulated results suggest that miR-20b exerts its effects through diverse signaling pathways, including PI3K/AKT/mTOR and ERK axes. Restoration of the altered expression levels of miR-20b induces cell apoptosis and reduces invasion and migration. Further, miR-20b can be used as a biomarker in cancer. The current comprehensive review could lead to a better understanding of the miR-20b in either tumorigenesis or tumor regression that may open new avenues for cancer treatment. Video Abstract.

The miR-17-92 cluster: Yin and Yang in human cancers

MicroRNAs (miRNAs) are non-coding RNAs which modulate gene expression via multiple post-transcriptional mechanisms. They are involved in a variety of biological processes, including cell proliferation, metastasis, metabolism, tumorigenesis, and apoptosis. Dysregulation of miRNA expression has been implicated in human cancers, and they may also serve as biomarkers of disease progression and prognosis. The miR-17-92 cluster is one of the most widely studied miRNA clusters, which was initially reported as an oncogene, but was later reported to exhibit tumour suppressive effects in some human cancers. This review summarizes the recent progress and context-dependant role of this cluster in various cancers. We summarize the known mechanisms which regulate miR-17-92 expression and molecular pathways that are in turn controlled by it. We discuss examples where it acts as an oncogene or a tumour suppressor along with key targets affecting hallmarks of cancer. We discuss how cellular contexts regulate the biological effects of miR-17-92. The plausible mechanisms of its paradoxical roles are explained, and mechanisms are described that may contribute to cell fate regulation by miR-17-92. Further, we discuss recently developed strategies to target miR-17-92 cluster in human cancers. MiR-17-92 may serve as a potential biomarker for prognosis and response to therapy as well as a target for cancer prevention and therapeutics.

Immune therapy of melanoma: Overview of therapeutic vaccines

Melanoma is the most serious type of skin cancer which develops from the occurrence of genetic mutations in the melanocytes. Based on the features of melanoma tumors such as location, genetic profile and stage, there are several therapeutic strategies including surgery, chemotherapy, and radiotherapy. However, because of the appearance resistance mechanisms, the efficiency of these treatments strategies may be reduced. It has been demonstrated that therapeutic monoclonal antibodies can improve the efficiency of melanoma therapies. Recently, several mAbs, such as nivolumab, pembrolizumab, and ipilimumab, were approved for the immunotherapy of melanoma. The antibodies inhibit immune checkpoint receptors such as CTL4 and pd-1. Another therapeutic strategy for the treatment of melanoma is cancer vaccines, which improve clinical outcomes in patients. The combination therapy using antibodies and gene vaccine give us a new perspective in the treatment of melanoma patients. Herein, we present the recent progressions in the melanoma immunotherapy, especially dendritic cells mRNA vaccines by reviewing recent literature.

The MicroRNA Family Both in Normal Development and in Different Diseases: The miR-17-92 Cluster

An increasing number of research studies over recent years have focused on the function of microRNA (miRNA) molecules which have unique characteristics in terms of structure and function. They represent a class of endogenous noncoding single-strand small molecules. An abundance of miRNA clusters has been found in the genomes of various organisms often located in a polycistron. The miR-17-92 family is among the most famous miRNAs and has been identified as an oncogene. The functions of this cluster, together with the seven individual molecules that it comprises, are most related to cancers, so it would not be surprising that they are considered to have involvement in the development of tumors. The miR-17-92 cluster is therefore expected not only to be a tumor marker, but also to perform an important role in the early diagnosis of those diseases and possibly also be a target for tumor biotherapy. The miR-17-92 cluster affects the development of disease by regulating many related cellular processes and multiple target genes. Interestingly, it also has important roles that cannot be ignored in disease of the nervous system and circulation and modulates the growth and development of bone. Therefore, it provides new opportunities for disease prevention, clinical diagnosis, prognosis, and targeted therapy. Here we review the role of the miR-17-92 cluster that has received little attention in relation to neurological diseases, cardiac diseases, and the development of bone and tumors.

MicroRNA-17 promotes osteosarcoma cells proliferation and migration and inhibits apoptosis by regulating SASH1 expression

MicroRNAs (miRNAs) are abnormally expressed in numerous diseases, which are intimately associated with cell proliferation, migration and invasion. Recent study indicated that miR-17 may be involved in regulating osteosarcoma (OS) occurrence and development, but its function and mechanism have not been reported. In this study, quantitative real-time PCR (qRT-PCR) was used to measure the expression of miR-17, and Western blotting assay was performed to measure the expressions of SAM and SH3 domain containing 1 (SASH1), phosphoinoinositide-3 kinase (PI3K), protein kinase B (AKT), Caspase3, Bcl-2 gene family (Bcl-2, Bax) and matrix metalloprotein (MMP-2, MMP-9) in MG-63 cells. Luciferase reporter assay was conducted to confirm the target of SASH1 by miR-17. Cell proliferation, migration, invasion and apoptosis assay was performed to investigate the role of miR-17 in OS cells. We found that the expression of miR-17 was significantly up-regulated in OS cell lines. MiR-17 inhibitor inhibited the proliferation ability, and induced apoptosis of OS cells. Besides, miR-17 inhibitor prevented the migration and invasion of OS cells. Further, we identified that SASH1 was a target gene of miR-17. In addition, knockdown of miR-17 increased the protein expression of SASH1, and regulate related genes of cell proliferation, invasion and anti-apoptosis in the downstream of OS cells. These findings indicated that miR-17 was over-expressed and promoted cell proliferation, migration and inhibited cell apoptosis by targeting SASH1 in OS cells.

The expression of Mirc1/Mir17-92 cluster in sputum samples correlates with pulmonary exacerbations in cystic fibrosis patients

INTRODUCTION

Cystic fibrosis (CF) is a multi-organ disorder characterized by chronic sino-pulmonary infections and inflammation. Many patients with CF suffer from repeated pulmonary exacerbations that are predictors of worsened long-term morbidity and mortality. There are no reliable markers that associate with the onset or progression of an exacerbation or pulmonary deterioration. Previously, we found that the Mirc1/Mir17-92a cluster which is comprised of 6 microRNAs (Mirs) is highly expressed in CF mice and negatively regulates autophagy which in turn improves CF transmembrane conductance regulator (CFTR) function. Therefore, here we sought to examine the expression of individual Mirs within the Mirc1/Mir17-92 cluster in human cells and biological fluids and determine their role as biomarkers of pulmonary exacerbations and response to treatment.

METHODS

Mirc1/Mir17-92 cluster expression was measured in human CF and non-CF plasma, blood-derived neutrophils, and sputum samples. Values were correlated with pulmonary function, exacerbations and use of CFTR modulators.

RESULTS

Mirc1/Mir17-92 cluster expression was not significantly elevated in CF neutrophils nor plasma when compared to the non-CF cohort. Cluster expression in CF sputum was significantly higher than its expression in plasma. Elevated CF sputum Mirc1/Mir17-92 cluster expression positively correlated with pulmonary exacerbations and negatively correlated with lung function. Patients with CF undergoing treatment with the CFTR modulator Ivacaftor/Lumacaftor did not demonstrate significant change in the expression Mirc1/Mir17-92 cluster after six months of treatment.

CONCLUSIONS

Mirc1/Mir17-92 cluster expression is a promising biomarker of respiratory status in patients with CF including pulmonary exacerbation.