Antioxidants Impair Anti-Tumoral Effects of Vorinostat, but Not Anti-Neoplastic Effects of Vorinostat and Caspase-8 Downregulation

Laura Bergadà,Andree Yeramian,Xavier Dolcet,Xavier Matias-Guiu,Annabel Sorolla

doi:10.1371/journal.pone.0092764

Abstract

We have recently demonstrated that histone deacetylase inhibitor, Vorinostat, applied as a single therapy or in combination with caspase-8 downregulation exhibits high anti-tumoral activity on endometrial carcinoma cell lines. In the present study, we have assessed the signalling processes underlying anti-tumoral effects of Vorinostat. Increasing evidence suggests that reactive oxygen species are responsible for histone deacetylase inhibitor-induced cell killing. We have found that Vorinostat induces formation of reactive oxygen species and DNA damage. To investigate the role of oxidative stress as anti-neoplastic mechanism, we have evaluated the effects of different antioxidants (Bha, Nac and Tiron) on endometrial carcinoma cell line Ishikawa treated with Vorinostat. We show that Bha, Nac and Tiron markedly inhibited the cytotoxic effects of Vorinostat, increasing cell viability in vitro. We found that all three antioxidants did not inhibited accumulation of acetyl Histone H4, so that antioxidants did not inhibit Vorinostat activity. Finally, we have evaluated the effects of antioxidants on anti-tumoral activity of Vorinostat as monotherapy or in combination with caspase-8 downregulation in vivo. Interestingly, antioxidants blocked the reduction of tumour growth caused by Vorinostat, but they were unable to inhibit anti-tumoral activity of Vorinostat plus caspase-8 inhibition.

Highlights

Histone deacetylase (HDAC) and histone acetyltransferase (HAT) are a class of enzymes which regulate the acetylation status of histones and non-histone proteins, the most frequently post-translational epigenetic modification in eukaryotic cells [1,2]
Vorinostat induces reactive oxygen species (ROS) production and DNA damage on endometrial cancer cells We have recently demonstrated that Vorinostat is an effective anti-neoplastic agent for EC cell lines [19]
We demonstrated that Vorinostat induced cell growth arrest, loss of clonogenic capability and apoptosis of EC cells

Summary

Introduction

Histone deacetylase (HDAC) and histone acetyltransferase (HAT) are a class of enzymes which regulate the acetylation status of histones and non-histone proteins, the most frequently post-translational epigenetic modification in eukaryotic cells [1,2]. HATs induce protein acetylation that neutralizes the positive charges on the histone by changing amines into amides decreasing the ability of the histones to bind to DNA. This allows chromatin expansion and gene transcription. HDACs induce protein hypoacetylation increasing positive charge of histone tails causing compaction of the DNA/histone complex and preventing expression of genes required for cell cycle arrest and apoptosis [3,4,5,6,7]. A recent study of our laboratory has demonstrated that HDACi such as Vorinostat can be effective for inducing apoptotic cell death in endometrial cancer (EC) cells [19]. We have demonstrated that Vorinostat displays anti-neoplastic activity on EC cells alone or in combination with inhibition of caspase-8

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