Growth inhibition of LU-HNSCC-4 cells following treatment with BBR3464 alone or in combination with (A) DENSPM and (B) DFMO. Cells were seeded in 96-well plates and 24 hours later DFMO or DENSPM were added at the indicated concentrations. The cells were incubated with the drugs for 48 h. Thereafter the cells were treated with BBR3464 at the indicated concentrations. After one 1 h of BBR3464 treatment, the drug containing medium was removed and the cells incubated for 72 h before cell growth was evaluated with an MTT assay. In the combination experiments cells were treated with different concentrations of DENSPM: 0 (□), 0.075 (●), 0.10 (♦), or 0.20 (■) μM, or DFMO: 0 (□), 10 (●), 25 (♦), or 50 (■) μM. Values represent average of triplicate experiments, and error bars indicate SEM. Isobolograms (C) and (D) for the combination of BBR3464 with DENSPM and DFMO, respectively.