Treatment of Nasopharyngeal Carcinoma Cells with the Histone-Deacetylase Inhibitor Abexinostat: Cooperative Effects with Cis-platin and Radiotherapy on Patient-Derived Xenografts

Kwok-Wai Lo,Stéphane Depil,François-Régis Ferrand,Mélanie Gressette,Pierre Busson,Anne-Sophie Jimenez-Pailhès,Benjamin Vérillaud,Maria G Masucci,Charles-Henry Gattolliat,Anne Jacquet-Bescond,Hélène Lelièvre,Laurence Kraus-Berthier

doi:10.1371/journal.pone.0091325

Abstract

EBV-related nasopharyngeal carcinomas (NPCs) still raise serious therapeutic problems. The therapeutic potential of the histone-deacetylase (HDAC) inhibitor Abexinostat was investigated using 5 preclinical NPC models including 2 patient-derived xenografts (C15 and C17). The cytotoxicity of Abexinostat used either alone or in combination with cis-platin or irradiation was assessed in vitro by MTT and clonogenic assays using 2 EBV-negative (CNE1 and HONE1) and 3 EBV-positive NPC models (C15, C17 and C666-1). Subsequently, the 3 EBV-positive models were used under the form of xenografts to assess the impact of systemic treatments by Abexinostat or combinations of Abexinostat with cis-platin or irradiation. Several cell proteins known to be affected by HDAC inhibitors and the small viral non-coding RNA EBER1 were investigated in the treated tumors. Synergistic cytotoxic effects of Abexinostat combined with cis-platin or irradiation were demonstrated in vitro for each NPC model. When using xenografts, Abexinostat by itself (12.5 mg/kg, BID, 4 days a week for 3 weeks) had significant anti-tumor effects against C17. Cooperative effects with cis-platin (2 mg/kg, IP, at days 3, 10 and 17) and irradiation (1Gy) were observed for the C15 and C17 xenografts. Simultaneously two types of biological alterations were induced in the tumor tissue, especially in the C17 model: a depletion of the DNA-repair protein RAD51 and a stronger in situ detection of the small viral RNA EBER1. Overall, these results support implementation of phase I/II clinical trials of Abexinostat for the treatment of NPC. A depletion of RAD51 is likely to contribute to the cooperation of Abexinostat with DNA damaging agents. Reduction of RAD51 combined to enhanced detection of EBER 1 might be helpful for early assessment of tumor response.

Highlights

Nasopharyngeal carcinoma (NPC) is a malignant tumor arising from the epithelial lining of the nasopharynx
Clonogenic assays for Abexinostat were performed for three cell lines able to sustain prolonged growth at low density, HONE1, CNE1 and C666-1
Biological and pharmacological investigations of NPC cells have long been hampered by the lack of genuinely representative cell lines, especially cell lines permanently propagated in vitro and retaining the Epstein Barr Virus (EBV) genome

Summary

Introduction

Nasopharyngeal carcinoma (NPC) is a malignant tumor arising from the epithelial lining of the nasopharynx. There are areas of intermediate incidence whose extension has long been underestimated. These areas include much of Southeast Asia (Philippines, Indonesia, Thailand and Vietnam) and North Africa. Regardless of patient geographical origin, NPCs are constantly associated with the Epstein Barr Virus (EBV) (except for a very small number of highly differentiated atypical forms related to tobacco and alcohol which are observed in Europe and North America) [2]. No viral particles are detected in the tumor but the EBV genome is present in the nucleus of all malignant cells, encoding for a number of latent gene products, non-translated RNAs (EBERs) and nuclear (EBNA1) or membrane proteins (LMP1 and LMP2). NPC is clearly a multifactorial disease, non-viral risk factors are germline genetic susceptibility and diet carcinogens which probably account for multiple acquired cellular genetic and epigenetic alterations [1]

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