Suberoyl bis-hydroxamic acid reactivates Kaposis sarcoma-associated herpesvirus through histone acetylation and induces apoptosis in lymphoma cells

Abstract

Kaposis sarcoma-associated herpesvirus (KSHV) is an etiologic agent of Kaposis sarcoma as well as primary effusion lymphoma (PEL), an aggressive B-cell neoplasm which mostly arises in immunocompromised individuals. At present, there is no specific treatment available for PEL and its prognosis is poor. Lytic replication of KSHV is also associated with a subset of multicentric Castleman diseases. In this study, we found that the histone deacetylase inhibitor suberoyl bis-hydroxamic acid (SBHA) induced KSHV reactivation in PEL cells in a dose-dependent manner. Next-generation sequencing analysis showed that more than 40% of all transcripts expressed in SBHA-treated PEL cells originated from the KSHV genome compared with less than 1% in untreated cells. Chromatin immunoprecipitation assays demonstrated that SBHA induced histone acetylation targeting the promoter region of the KSHV replication and transcription activator gene. However, there was no significant change in methylation status of the promoter region of this gene. In addition to its effect of KSHV reactivation, this study revealed that SBHA induces apoptosis in PEL cells in a dose-dependent manner, inducing cleavage of caspases and expression of proapoptotic factors, including Bim and Bax. These findings suggest that SBHA reactivates KSHV from latency and induces apoptosis through the mitochondrial pathway in PEL cells. Therefore, SBHA can be considered a new tool for induction of KSHV reactivation, and could provide a novel therapeutic strategy against PEL. ImportanceKaposis sarcoma and primary effusion lymphoma cells are latently infected with Kaposis sarcoma-associated herpesvirus (KSHV), whereas KSHV replication is frequently observed in multicentric Castleman disease. Although KSHV replication can be induced by some chemical reagents (e.g. 12-O-tetradecanoylphorbol-13-acetate), the mechanism of KSHV replication is not fully understood. We found that the histone deacetylase inhibitor suberoyl bis-hydroxamic acid (SBHA) induced KSHV reactivation with high efficiency, through histone acetylation in the promoter of the replication and transcription activator gene, compared with 12-O-tetradecanoylphorbol-13-acetate. SBHA also induced apoptosis through the mitochondrial pathway in KSHV-infected cells, with a lower EC50 than measured for viral reactivation. SBHA could be used in a highly efficient replication system for KSHV in vitro, and as a tool to reveal the mechanism of replication and pathogenesis of KSHV. The ability of SBHA to induce apoptosis at lower levels than needed to stimulate KSHV reactivation, indicates its therapeutic potential.