OBJECTIVETo investigate synergistically killing effect of histone deacetylase (HDAC) inhibitor suberoylanilide hydroxamic acid (SAHA) combined with imatinib on human chronic myeloid leukemia (CML) cell line.

METHODSK562 cells were co-treated with SAHA and imatinib. Cell growth was measured by MTT assay. Apoptosis was determined using Hoechst staining apoptosis detection kit and flow cytometric analysis. Activation of Caspase pathway, expression of Bcr-Abl and its downstream target genes, and expression of anti-apoptotic proteins were detected by Western blot.

RESULTSSAHA synergized the cytotoxicity of imatinib against leukemia K562 cells, concomitantly with increased apoptosis and enhanced activation of Caspase-3, -8 and PRAP. The combination therapy resulted in significantly lower levels of Bcr-Abl,phosphorylated Bcr-Abl compared to treatment with either SAHA or imatinib alone. Furthermore,the co-treatment resulted in down-regulation of anti-apoptotic protein Mcl-1 expression. Also,marked down-regulated expression of JAK2,STAT5,and phosphorylated STAT5 was detected in the combination therapy.

CONCLUSIONCombining HDAC inhibitor SAHA with imatinib can kill CML cells synergistically by inhibiting cell growth and inducing apoptosis, which is associated with activation of Caspase pathway and regulation of anti-apoptotic proteins.