The long non-coding RNA GAS5 differentially regulates cell cycle arrest and apoptosis through activation of BRCA1 and p53 in human neuroblastoma.

Joseph Mazar,Amy Rosado,John Shelley,Tamarah J Westmoreland,John Marchica

doi:10.18632/oncotarget.14244

Abstract

The long non-coding RNA GAS5 has been shown to modulate cancer proliferation in numerous human cancer systems and has been correlated with successful patient outcome. Our examination of GAS5 in neuroblastoma has revealed robust expression in both MYCN-amplified and non-amplified cell lines. Knockdown of GAS5 In vitro resulted in defects in cell proliferation, apoptosis, and induced cell cycle arrest. Further analysis of GAS5 clones revealed multiple novel splice variants, two of which inversely modulated with MYCN status. Complementation studies of the variants post-knockdown of GAS5 indicated alternate phenotypes, with one variant (FL) considerably enhancing cell proliferation by rescuing cell cycle arrest and the other (C2) driving apoptosis, suggesting a unique role for each in neuroblastoma cancer physiology. Global sequencing and ELISA arrays revealed that the loss of GAS5 induced p53, BRCA1, and GADD45A, which appeared to modulate cell cycle arrest in concert. Complementation with only the FL GAS5 clone could rescue cell cycle arrest, stabilizing HDM2, and leading to the loss of p53. Together, these data offer novel therapeutic targets in the form of lncRNA splice variants for separate challenges against cancer growth and cell death.

Highlights

Neuroblastoma is one of the most common extra cranial tumors of childhood, and the most commonly diagnosed malignancy in infants [1,2,3]
Expression of the long non-coding RNAs (lncRNAs) Growth Arrest-Specific 5 (GAS5) has been shown to have a physiological impact on numerous human cancer systems [12,13,14,15,16]
Given recent discoveries of the presence of lncRNAs relevant to neuroblastoma [40, 41] and various reports of the significance of GAS5 in several cancer systems [8,9,10], we decided to examine if this lncRNA showed promise as a biomarker or possible therapeutic target in this cancer system

Summary

Introduction

Neuroblastoma is one of the most common extra cranial tumors of childhood, and the most commonly diagnosed malignancy in infants [1,2,3]. With challenging heterogeneity within the tumor subpopulation, prognostic factors for survival include age at diagnosis, tumor grade, tumor site, histology, and amplification of the v-myc avian myelocytomatosis viral oncogene neuroblastoma derived homolog (MYCN) gene [4, 5]. Over the last 20 years, there has not been great improvement in the overall survival of children with MYCN-amplified neuroblastoma. It is imperative that we focus on the underlying genetic changes that are occurring in this high-risk group. To this end, we are investigating the molecular events surrounding neuroblastoma, with emphasis on long non-coding RNAs (lncRNAs) and their role in neuroblastoma. Thought to be “junk” RNA, there is increasing evidence that lncRNAs are involved in a wide range of biological functions, including cell differentiation, proliferation, and apoptosis, among others [2, 9]

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