OBJECTIVETo explore the impact of a new generation of histone deacetylase inhibitor LBH589 alone or in combination with proteasome inhibitor bortezomib on multiple myeloma (MM) cells proliferation and its mechanism.

METHODSMM cell line U266 and dexamethasone resistant cell line MM1R cells were treated with different concentrations of LBH589 alone or in combination with bortezomib, the inhibition of cells proliferation was detected by MTT, the cell cycle and apoptosis by flow cytometry. The expression level of histone H4 acetylation and PARP, Bcl-X protein was analyzed by western blot, expression level of caspase-3, APAF-1 and TOSO gene by real-time fluorescence quantitative PCR.

RESULTSU266 and MM1R cell proliferation were inhibited by different concentrations of LBH589 (0, 10, 20, 50 nmol/L) alone or 50 nmol/L of LBH589 in combination with bortezomib (10, 20 nmol/L) in a dose- and time-dependent manner. Inhibition effect was significantly higher in all combinative groups than in single agent groups (all P < 0.05). The percentage of G(0)/G(1) phase in MM1R cells were 36.60%, 46.50%, 51.40%, 57.10%, 75.48%, 79.73%, respectively, and the apoptosis rate were 5.27%, 31.41%, 39.78%, 44.07%, 73.60%, 83.27%, respectively. The effects appeared to occur in a dose-dependent manner, and being significantly higher in all combinative groups than in single agent groups (all P < 0.05). The expression of the caspase-3 and APAF-1 gene up-regulated gradually, while TOSO gene expression in MM1R cells down-regulated gradually in a dose- and time-dependent manner (all P < 0.05).

CONCLUSIONSLBH589 can inhibit the growth of MM cells, block the cell cycle and induce cell apoptosis, which has anti-resistant effect on multidrug resistant cell. At the same time LBH589 in combination with bortezomib on myeloma cell has a synergistic effect, its mechanism and reversal of drug resistance mechanism involves in multiple changes in gene expression.