The Histone Deacetylase Inhibitor Valproic Acid Exerts a Synergistic Cytotoxicity with the DNA-Damaging Drug Ellipticine in Neuroblastoma Cells.

Tereza Cerna,Eva Frei,Tomas Eckschlager,Marie Stiborová,Heinz Schmeiser,Volker Arlt,Jan Hrabeta

doi:10.3390/ijms19010164

Abstract

Neuroblastoma (NBL) originates from undifferentiated cells of the sympathetic nervous system. Chemotherapy is judged to be suitable for successful treatment of this disease. Here, the influence of histone deacetylase (HDAC) inhibitor valproate (VPA) combined with DNA-damaging chemotherapeutic, ellipticine, on UKF-NB-4 and SH-SY5Y neuroblastoma cells was investigated. Treatment of these cells with ellipticine in combination with VPA led to the synergism of their anticancer efficacy. The effect is more pronounced in the UKF-NB-4 cell line, the line with N-myc amplification, than in SH-SY5Y cells. This was associated with caspase-3-dependent induction of apoptosis in UKF-NB-4 cells. The increase in cytotoxicity of ellipticine in UKF-NB-4 by VPA is dictated by the sequence of drug administration; the increased cytotoxicity was seen only after either simultaneous exposure to these drugs or after pretreatment of cells with ellipticine before their treatment with VPA. The synergism of treatment of cells with VPA and ellipticine seems to be connected with increased acetylation of histones H3 and H4. Further, co-treatment of cells with ellipticine and VPA increased the formation of ellipticine-derived DNA adducts, which indicates an easier accessibility of ellipticine to DNA in cells by its co-treatment with VPA and also resulted in higher ellipticine cytotoxicity. The results are promising for in vivo studies and perhaps later for clinical studies of combined treatment of children suffering from high-risk NBL.

Highlights

Neuroblastoma (NBL) represents the commonest extracranial solid tumor of children
Our results indicated that ellipticine was toxic to both UKF-NB-4 and SH-SY5Y cells, but that its toxic effect was lower in SH-SY5Y cells than in UKF-NB-4 cells; the IC50 values were 1.88 ± 0.13 μM and 1.27 ± 0.28 μM, respectively
When cells were treated with both drugs in combination, ellipticine cytotoxicity was higher and this effect was more pronounced in UKF-NB-4 NBL cells

Summary

Introduction

NBL cells can spontaneously regress or differentiate; they can naturally deteriorate, develop to benign ganglioneuroma, or grow continuously becoming speedily lethal depending on the NBL biological type [1,2]. These processes might influence the efficacy of therapy, especially the replay on apoptosis developed during chemotherapy. Histone modifications include the lysine acetylation status of the core histones H3 and H4, which influence chromatin condensation Such changes affect transcription of several genes together with upregulation of numerous antioncogenes and genes participating in repair of DNA [9]. HDACs function in posttranscriptional alterations of numerous regulatory non-histone proteins, for example several transcription factors, chaperones or signaling factors [10]

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Results

Conclusion