Broad-Spectrum HDAC Inhibitors Promote Autophagy through FOXO Transcription Factors in Neuroblastoma.

Katharina Körholz,Ina Oehme,Benjamin Meder,Olaf Witt,Johannes Ridinger,Heike Peterziel,Silvia Vega-Rubin-De-Celis,Karen Frese,Sara Najafi,Damir Krunic,Xenia F Gerloff

doi:10.3390/cells10051001

Abstract

Depending on context and tumor stage, deregulation of autophagy can either suppress tumorigenesis or promote chemoresistance and tumor survival. Histone deacetylases (HDACs) can modulate autophagy; however, the exact mechanisms are not fully understood. Here, we analyze the effects of the broad-spectrum HDAC inhibitors (HDACi) panobinostat and vorinostat on the transcriptional regulation of autophagy with respect to autophagy transcription factor activity (Transcription factor EB—TFEB, forkhead boxO—FOXO) and autophagic flux in neuroblastoma cells. In combination with the late-stage autophagic flux inhibitor bafilomycin A1, HDACis increase the number of autophagic vesicles, indicating an increase in autophagic flux. Both HDACi induce nuclear translocation of the transcription factors FOXO1 and FOXO3a, but not TFEB and promote the expression of pro-autophagic FOXO1/3a target genes. Moreover, FOXO1/3a knockdown experiments impaired HDACi treatment mediated expression of autophagy related genes. Combination of panobinostat with the lysosomal inhibitor chloroquine, which blocks autophagic flux, enhances neuroblastoma cell death in culture and hampers tumor growth in vivo in a neuroblastoma zebrafish xenograft model. In conclusion, our results indicate that pan-HDACi treatment induces autophagy in neuroblastoma at a transcriptional level. Combining HDACis with autophagy modulating drugs suppresses tumor growth of high-risk neuroblastoma cells. These experimental data provide novel insights for optimization of treatment strategies in neuroblastoma.

Highlights

We show that vorinostat and panobinostat induce autophagy, transcriptionally upregulate autophagy related genes in neuroblastoma cells and induce nuclear translocation of the autophagy transcription factors FOXO1 and FOXO3a
We assessed the amount of phosphatidylethanolamine conjugated microtubule-associated protein light chain 3 (LC3-II), an autophagy marker localized to the autophagosome membrane, after treatment with either Histone deacetylases (HDACs) inhibitor alone or in combination with the late stage autophagy inhibitor bafilomycin A1 [33]
As vorinostat and panobinostat promote autophagic flux and are well-known modulators of gene transcription, we investigated the effect of these HDAC inhibitors on the expression of autophagy-related genes

Summary

Introduction

Neuroblastoma is an embryonal tumor derived from progenitor cells of the sympathetic nervous system. It is the most common extracranial solid tumor in children and causes at least 10% of the pediatric cancer deaths [1,2]. Survival of neuroblastoma patients strongly depends on age at diagnosis, stage of disease and neuroblastoma tumor biology. In high-risk patients, disease outcome is still poor and relapse rates are high underlining the need to develop novel therapeutic strategies and treatments (reviewed in [3,4])

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