Normal lung cells and lung tumor cells were treated with cidofovir (Panel A), dihydroartemisinin (Panel B), or vorinostat (Panel C) at the indicated concentrations for 48 hours. Cell viability was measured with the use of the CellTiter-Glo Luminescent Cell Viability Assay. Vorinostat had a median curative dose of 4.2 μM in tumor cells (95% confidence interval [CI], 3.2 to 5.4) versus 15.9 μM in normal cells (95% CI, 13.2 to 19.2), with selectivity for tumor versus normal cells (P<0.001). Panel D shows images from a computed tomographic scan of a representative lung tumor mass in the right lower lobe before and after a 3-month course of treatment with vorinostat. This mass remained reduced in size 9 months later, when the yearlong course of therapy was terminated.