Fig. 1

a Combination dose-finding studies with panobinostat and erlotinib. The three NSCLC cell lines HCC827, A549 and NCI-H460 were treated with three different concentrations of PS in combination with five concentrations of erlotinib to determine by WST-1 assay the most effective combination dose that reduces proliferation to 50 % compared to the vehicle (DMSO) control after 72 h (representative experiment with biological triplicates shown). The concentration ranges of both drugs were determined beforehand in independent experiments (data not shown). b Combination treatment with panobinostat and erlotinib significantly reduces proliferation of NSCLC adenocarcinoma cell lines. Proliferation of NSCLC cells after treatment with PS and/or erlotinib was measured by WST-1 assay after 24, 48 and 72 h, normalized to DMSO vehicle treated cells. The combination of PS and erlotinib reduced proliferation significantly after 72 h in HCC827 and A549 cells (compared to PS alone; *** p < 0.001 Student’s t-test, paired, two-tailed)