Impact of histone deacetylase inhibitors SAHA and MS-275 on DNA repair pathways in human mesenchymal stem cells.

Histone deacetylase inhibitors (HDACis) have received considerable attention for their anti-tumoral properties. We report here the effects of two HDACis, SAHA and MS-275, on the biology of mesenchymal stem cells (MSCs). It is well known that HDACis trigger both DNA damage responses and actual DNA damage in cancer cells. On this premise, we evaluated HDACis influence on DNA damage pathways in MSCs. We analyzed a panel of genes involved in the regulation of base and nucleotide excision repair, mismatch repair, and double strand break repair. That a majority of the analyzed genes displayed significant expression changes upon incubation with SAHA or MS-275 suggested that regulation of their expression is greatly affected by HDACis. The complex expression pattern, with some genes up-regulated and other under-expressed, did not allow to foresee whether these changes allow cells cope with stressful DNA damaging stimuli. Furthermore, we evaluated the biological outcome following treatment of MSCs with DNA damaging agents (H(2)O(2) and UV) in presence of HDACis. In these settings, MSCs treated with H(2)O(2) or UV radiation underwent apoptosis and/or senescence, and pre-incubation with HDACi exacerbated cell death phenomena. Accordingly, the number of cells harboring 8-oxo-7,8-dihydroguanine (8oxodG), a hallmark of DNA oxidative damage, was significantly higher in samples incubated with HDACis compared to controls. In summary, our findings suggest that SAHA and MS-275, even at low effective doses, can alter the biology of MSCs, diminishing their ability to survive the effects of DNA-damaging agents.