Vorinostat is genotoxic and epigenotoxic in the mouse bone marrow cells at the human equivalent doses.

Vorinostat was approved as the first histone deacetylase inhibitor for the management of cutaneous T cell lymphoma. However, it's in vivo genetic and epigenetic effects on non-cancerous cells remain poorly understood. As genetic and epigenetic changes play a critical role in the pathogenesis of carcinogenesis, we investigated whether vorinostat induces genetic and epigenetic alterations in mouse bone marrow cells. Bone marrow cells were isolated 24 h following the last oral administration of vorinostat at the doses of 25, 50, or 100 mg/kg/day for five days (approximately equal to the recommended human doses). The cells were then used to assess clastogenicity and aneugenicity by the micronucleus test complemented by fluorescence in situ hybridization assay; DNA strand breaks, oxidative DNA strand breaks, and DNA methylation by the modified comet assay; apoptosis by annexin V/PI staining analysis and the occurrence of the hypodiploid DNA content; and DNA damage/repair gene expression by polymerase chain reaction (PCR) Array. The expression of the mRNA transcripts were also confirmed by real-time PCR and western blot analysis. Vorinostat caused structural chromosomal damage, numerical chromosomal abnormalities, DNA strand breaks, oxidative DNA strand breaks, DNA hypomethylation, and programed cell death in a dose-dependent manner. Furthermore, the expression of numerous genes implicated in DNA damage/repair were altered after vorinostat treatment. Accordingly, the genetic/epigenetic mechanism(s) of action of vorinostat may play a role in its carcinogenicity and support the continued study and development of new compounds with lower toxicity.