MST312 effect on both ALDH positive and negative populations. A: 96 h incubation with MST312 decreases survival of H460 cells in a dose-dependent manner, with a greater response observed for the ALDH+ fraction. B: Similar effects are detected for H1299 cells. C and D: MST312 was administered to the whole H460 or H1299 unsorted cell populations for 5 days and ALDH+ cells were quantified by FACS analysis. D: FACS quantifications revealed a significant reduction in ALDH+ percentage when cells were treated with MST312 (left: H460 cell line; right: H1299 cell line), thus showing that telomerase inhibition targets the CSC population. Data and error bars are shown as mean ± SEM; *: p < 0.05; **: p < 0.01.