Abstract 488: High DKC1 expression supports neuroblastoma tumor cell proliferation and is strongly associated with poor patient outcomes

Abstract

Abstract Dyskerin is a nucleolar RNA-binding protein that functions as a core component of the telomerase holoenzyme, as well as in ribonuclear protein complexes involved in ribosome biogenesis and RNA processing. This study investigates the clinical and functional relevance of dyskerin expression in the paediatric cancer neuroblastoma. Here it is shown, in two independent neuroblastoma patient cohorts, that high expression of the gene encoding dyskerin (DKC1) very strongly correlates with poor event-free and overall survival. The prognostic power of DKC1 expression was independent of the established indicators used in the management of this disease, namely diagnosis age > 1.5 yr, stage of disease and amplification of the MYCN oncogene (P<0.0001). Dyskerin mRNA and protein expression were also found to be elevated, relative to normal cells, across a panel of neuroblastoma cell lines. Chromatin immunoprecipitation showed that the DKC1 promoter region was directly targeted by both MycN and c-Myc in neuroblastoma cells. Depletion of dyskerin using RNAi severely impaired proliferation, inhibited anchorage independent growth and dramatically slowed tumour growth in a mouse model of neuroblastoma (P<0.01, Two-way Anova). In p53 competent cells, the proliferative arrest induced by dyskerin depletion was accompanied by an accumulation of p53 and p21cip1, accumulation in G1 phase of the cell cycle and cell death. However in the absence of p53 function, an alternate mechanism operated to impair proliferation when dyskerin was downregulated. The mechanism responsible for the proliferative arrest also appeared to be telomerase-independent, as it was not rescued by ectopic overexpression of telomerase. Taken together, these data identify DKC1 is a crucial MYC target gene in neuroblastoma, and show that neuroblastoma cells become addicted to high DKC1 expression. The results support further investigation of DKC1 as a therapeutic target in the treatment of refractory neuroblastoma. Citation Format: Rosemary O'Brien, Michelle F. Maritz, Cheng Fei Kong, Stefania Purgato, Bing Liu, Chen Yang, Amanda Russell, Jayne Murray, Claudia Flemming, Michelle Haber, Giovanni Perini, Murray D. Norris, Jamie I. Fletcher, Karen L. Mackenzie. High DKC1 expression supports neuroblastoma tumor cell proliferation and is strongly associated with poor patient outcomes. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 488. doi:10.1158/1538-7445.AM2015-488