To enhance the effect of GS-1101, SU-DHL-6/16 cells and NHL primary cells were simultaneously treated with the HDAC inhibitor LBH589. An interaction of the LBH589/GS-1101 combination was formally examined by using various concentrations of LBH589 and GS-1101. Combined treatment resulted in a synergistic inhibition of proliferation in all tested cells and induced a significant increase of caspase-dependent apoptosis in SU-DHL-6/16 cells. For example, in SU-DHL-6 cells co-treatment of 0.1 μM GS-1101 with 2.5 nM LBH589 induced 62% increase of apoptotic population in comparison to the untreated sample, while GS-1101 alone induced 13% increase and LBH589 induced 11% increase. Moreover, substituting SAHA for LBH589 suggests that the synergy between GS-1101 and LBH589 is a class effect between HDAC inhibitors and GS-1101, rather than specific to LBH589.