Abstract B44: The epigenetic modifier CHAF1A opposes neuroblastoma differentiation via metabolic reprogramming

Abstract

Abstract Background: Neuroblastoma arises from embryonal neural crest secondary to a block in differentiation and long-term survival inversely correlates with the degree of neuronal differentiation. Inhibition of epigenetically controlled developmental programs is critical for neuronal de-differentiation and neuroblastoma pathogenesis. Treatment with differentiation agents has modestly improved survival. Methods: Loss-of-function studies in neuroblastoma cell lines with inducible and stable CHAF1A knockdown were performed in vitro and in vivo. Gene expression profiling of knockdown and control cell lines was performed on the Affymetrix U133+2.0 arrays. GSEA (Gene Set Enrichment Analysis) defined the transcriptional response to CHAF1A silencing. Quantitative-PCR assays were used to correlate CHAF1A expression with outcome and to validate the most significant enriched gene sets. Results: Here we demonstrate a novel function for the histone chaperone and epigenetic regulator CHAF1A in maintaining the highly de-differentiated state of neuroblastoma. CHAF1A is a subunit of the Chromatin Assembly Factor-1 (CAF1) which regulates H3K9-trimethylation and DNA methylation. High CHAF1A expression strongly correlates with poor prognosis in a large clinical cohort of 348 neuroblastoma patients (Progression-Free and Overall Survival p<0.001). Loss-of-function effectively controls tumor growth and drives neuronal differentiation both in vitro and in vivo. GSEA reveals that genes regulated by CHAF1A are associated with major metabolism and oncogenic pathways. CHAF1A silencing significantly (nominal p-value <0.05 and FDR q-value <0.25) enriches for cell metabolism pathways (valine, leucine, and isoleucine degradation, glutamate metabolism and insulin pathways) and suppresses pathways with known oncogenic function in neuroblastoma (KRAS, ALK, Akt and BMI1). Quantitative-PCR confirms that the most affected genes belong to the glucose and insulin pathway. Conclusions: Our findings support the hypothesis that CHAF1A expression restricts neural crest differentiation and contributes to the pathogenesis of high-risk neuroblastoma by epigenetic regulation of glucose metabolism. In particular, we believe that the oncogenic functions of CHAF1A in neuroblastoma in part direct the metabolic reprogramming, thus conferring cell survival advantages and blocking cell differentiation. Further understanding of the metabolic changes epigenetically induced by CHAF1A will identify vulnerable points to impair neuroblastoma cell growth and guide the development of novel therapies. Citation Format: Eveline Barbieri, Zaowen Chen, Anna Lakoma, Eugene Kim, Jason Shohet. The epigenetic modifier CHAF1A opposes neuroblastoma differentiation via metabolic reprogramming. [abstract]. In: Proceedings of the AACR Special Conference on Pediatric Cancer at the Crossroads: Translating Discovery into Improved Outcomes; Nov 3-6, 2013; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2013;74(20 Suppl):Abstract nr B44.