Lysine-Specific Demethylase 1 Is Strongly Expressed in Poorly Differentiated Neuroblastoma: Implications for Therapy

Johannes H Schulte,Ingrid Ora,Reinhard Buettner,Nicolaus Friedrichs,Roland SchüLe,Steffi Kuhfittig-Kulle,Ludger Klein-Hitpass,Jutta Kirfel,Angelika Eggert,Eric Metzger,Rogier Versteeg,Kristian Pajtler,Jan Koster,Alexander Schramm,Soyoung Lim

doi:10.1158/0008-5472.can-08-1735

Abstract

Aberrant epigenetic changes in DNA methylation and histone acetylation are hallmarks of most cancers, whereas histone methylation was previously considered to be irreversible and less versatile. Recently, several histone demethylases were identified catalyzing the removal of methyl groups from histone H3 lysine residues and thereby influencing gene expression. Neuroblastomas continue to remain a clinical challenge despite advances in multimodal therapy. Here, we address the functional significance of the chromatin-modifying enzyme lysine-specific demethylase 1 (LSD1) in neuroblastoma. LSD1 expression correlated with adverse outcome and was inversely correlated with differentiation in neuroblastic tumors. Differentiation of neuroblastoma cells resulted in down-regulation of LSD1. Small interfering RNA-mediated knockdown of LSD1 decreased cellular growth, induced expression of differentiation-associated genes, and increased target gene-specific H3K4 methylation. Moreover, LSD1 inhibition using monoamine oxidase inhibitors resulted in an increase of global H3K4 methylation and growth inhibition of neuroblastoma cells in vitro. Finally, targeting LSD1 reduced neuroblastoma xenograft growth in vivo. Here, we provide the first evidence that a histone demethylase, LSD1, is involved in maintaining the undifferentiated, malignant phenotype of neuroblastoma cells. We show that inhibition of LSD1 reprograms the transcriptome of neuroblastoma cells and inhibits neuroblastoma xenograft growth. Our results suggest that targeting histone demethylases may provide a novel option for cancer therapy.

Highlights

Neuroblastoma, the most common extracranial tumor of childhood, is an embryonal malignancy originating from the neural crest
Similar results were obtained in an independent cohort of 102 neuroblastic tumors previously analyzed on Affymetrix microarrays when these data were reanalyzed for lysine-specific demethylase 1 (LSD1) mRNA levels (Fig. 1C)
Our data clearly indicate that LSD1 expression inversely correlates with differentiation and adverse outcome of primary neuroblastic tumors

Summary

Introduction

Neuroblastoma, the most common extracranial tumor of childhood, is an embryonal malignancy originating from the neural crest. The clinical course of neuroblastoma is very heterogeneous. While neuroblastoma with favorable biology, as well as the benign variants ganglioneuroblastoma and ganglioneuroma, spontaneously regress or differentiate without any therapeutic intervention, neuroblastoma with unfavorable biology. Transcription factors are generally less suited as drug targets. Enzymes involved in epigenetic gene regulation are suitable drug targets and modulate broad expression patterns. Histone acetylation and DNA methylation have been shown to regulate central genes in aggressive neuroblastoma [9,10,11]. Treatment with histone deacetylase (HDAC) inhibitors and DNA-demethylating agents has proved effective against neuroblastoma cells in vitro [9] and are currently being evaluated for treating neuroblastoma in vivo

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Results

Conclusion