Inhibition of class I histone deacetylases by romidepsin potently induces Epstein‐Barr virus lytic cycle and mediates enhanced cell death with ganciclovir

• Published in: International journal of cancer 2016-01, Vol.138 (1), p.125-136
• Main Authors: Hui, Kwai Fung, Cheung, Arthur Kwok Leung, Choi, Chung King, Yeung, Po Ling, Middeldorp, Jaap M., Lung, Maria Li, Tsao, Sai Wah, Chiang, Alan Kwok Shing
• Format: Article
• Language: English
• Subjects: Acetylation; Animals; Antiviral Agents - pharmacology; Apoptosis; Ataxia Telangiectasia Mutated Proteins - metabolism; Cancer; Carcinoma; Cell Death - drug effects; Cell Line; Cell Proliferation - drug effects; Cyclin-Dependent Kinase Inhibitor p21 - metabolism; Depsipeptides - pharmacology; Disease Models, Animal; Disease Susceptibility; Dose-Response Relationship, Drug; epithelial cancer; Epithelial Cells - drug effects; Epithelial Cells - metabolism; Epithelial Cells - virology; Epstein-Barr virus; Ganciclovir - pharmacology; Genes; Herpesvirus 4, Human - drug effects; Herpesvirus 4, Human - physiology; histone deacetylase inhibitor; Histone Deacetylase Inhibitors - pharmacology; Histone Deacetylases - genetics; Histone Deacetylases - metabolism; Histones - metabolism; Humans; Kinases; lytic cycle; MAP Kinase Signaling System - drug effects; Medical research; Mice; Nasopharyngeal Carcinoma; Nasopharyngeal Neoplasms - drug therapy; Nasopharyngeal Neoplasms - metabolism; Nasopharyngeal Neoplasms - pathology; Nasopharyngeal Neoplasms - virology; Protein Kinase C-delta - metabolism; romidepsin; Signal Transduction - drug effects; Stomach Neoplasms - drug therapy; Stomach Neoplasms - metabolism; Stomach Neoplasms - pathology; Stomach Neoplasms - virology; Virus Activation - drug effects; Virus Replication - drug effects; Xenograft Model Antitumor Assays
• ISSN: 0020-7136; 1097-0215
• DOI: 10.1002/ijc.29698

Pan‐histone deacetylase (HDAC) inhibitors, which inhibit 11 HDAC isoforms, are widely used to induce Epstein‐Barr virus (EBV) lytic cycle in EBV‐associated cancers in vitro and in clinical trials. Here, we hypothesized that inhibition of one or several specific HDAC isoforms by selective HDAC inhibitors could potently induce EBV lytic cycle in EBV‐associated malignancies such as nasopharyngeal carcinoma (NPC) and gastric carcinoma (GC). We found that inhibition of class I HDACs, particularly HDAC‐1, ‐2 and ‐3, was sufficient to induce EBV lytic cycle in NPC and GC cells in vitro and in vivo. Among a panel of selective HDAC inhibitors, the FDA‐approved HDAC inhibitor romidepsin was found to be the most potent lytic inducer, which could activate EBV lytic cycle at ∼0.5 to 5 nM (versus ∼800 nM achievable concentration in patients' plasma) in more than 75% of cells. Upregulation of p21WAF1, which is negatively regulated by class I HDACs, was observed before the induction of EBV lytic cycle. The upregulation of p21WAF1 and induction of lytic cycle were abrogated by a specific inhibitor of PKC‐δ but not the inhibitors of PI3K, MEK, p38 MAPK, JNK or ATM pathways. Interestingly, inhibition of HDAC‐1, −2 and −3 by romidepsin or shRNA knockdown could confer susceptibility of EBV‐positive epithelial cells to the treatment with ganciclovir (GCV). In conclusion, we demonstrated that inhibition of class I HDACs by romidepsin could potently induce EBV lytic cycle and mediate enhanced cell death with GCV, suggesting potential application of romidepsin for the treatment of EBV‐associated cancers. What's new? In cancers associated with Epstein‐Barr virus (EBV), the virus persists in latent form, becoming susceptible to drug therapy only after the lytic cycle has been reactivated. To effectively leverage lytic reactivation clinically, however, more specific and more potent pharmacologic lytic inducers are needed. A promising agent is romidepsin, a class I histone deacetylase (HDAC) inhibitor, shown in this study to potently trigger the EBV lytic cycle through HDAC‐1/‐2/‐3 inhibition and protein kinase C‐δ activation. Lytic induction augmented the cell‐killing effects of the antiviral ganciclovir. The data warrant further investigation of romidepsin for the treatment of EBV‐associated cancers.