MiR-23a impairs bone differentiation in osteosarcoma via down-regulation of GJA1.

Yevgeniy Gindin,Princy Francis,Robert L Walker,Paul S Meltzer,Yuan Jiang,Ogan D Abaan,Yuelin J Zhu

doi:10.3389/fgene.2015.00233

Abstract

Osteosarcoma is the most common type of bone cancer in children and adolescents. Impaired differentiation of osteoblast cells is a distinguishing feature of this aggressive disease. As improvements in survival outcomes have largely plateaued, better understanding of the bone differentiation program may provide new treatment approaches. The miRNA cluster miR-23a~27a~24-2, particularly miR-23a, has been shown to interact with genes important for bone development. However, global changes in gene expression associated with functional gain of this cluster have not been fully explored. To better understand the relationship between miR-23a expression and bone cell differentiation, we carried out a large-scale gene expression analysis in HOS cells. Experimental results demonstrate that over-expression of miR-23a delays differentiation in this system. Downstream bioinformatic analysis identified miR-23a target gene connexin-43 (Cx43/GJA1), a mediator of intercellular signaling critical to osteoblast development, as acutely affected by miR-23a levels. Connexin-43 is up-regulated in the course of HOS cell differentiation and is down-regulated in cells transfected with miR-23a. Analysis of gene expression data, housed at Gene Expression Omnibus, reveals that Cx43 is consistently up-regulated during osteoblast differentiation. Suppression of Cx43 mRNA by miR-23a was confirmed in vitro using a luciferase reporter assay. This work demonstrates novel interactions between microRNA expression, intercellular signaling and bone differentiation in osteosarcoma.

Highlights

Osteosarcoma is the most common primary bone malignancy and occurs most frequently in adolescents (Mirabello et al, 2009)
We study the effects of miR-23a expression in HOS cells, which are distinguished from other human osteosarcoma cells by their ability to undergo a bone cell lineage differentiation program (Siggelkow et al, 1998; Hassan et al, 2010)
Induction of Differentiation in Osteosarcoma Cells To confirm that HOS cells are amendable to bone differentiation induction (Siggelkow et al, 1998), we treated these cells with L-ascorbic acid, which induces the formation of collagenous extracellular matrix and brings an osteoblast-specific gene expression program in osteogenic lineage cells (Franceschi et al, 1994)

Summary

Introduction

Osteosarcoma is the most common primary bone malignancy and occurs most frequently in adolescents (Mirabello et al, 2009). Osteosarcoma tumors most often arise in the long bones of the skeleton, with more than half presenting around the knee (Broadhead et al, 2011), and is less common in axial skeleton (Martin et al, 2012). 20% of osteosarcoma patients present with lung metastases with an additional 40% developing metastases at later stage (Martin et al, 2012). The survival rates for osteosarcoma have remained essentially unchanged for over two decades (Longhi et al, 2006; Mirabello et al, 2009). It is possible that the path toward developing new treatment approaches for osteosarcoma lies through an improved understanding of the dysregulation of the bone differentiation program in this devastating disease

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Results

Conclusion