(A) A plate colony formation assay was used to assess the effect of digoxin on the colony formation capability of A549 and H1299 cells. The cells were incubated for 12 days and then stained with Crystal Violet after treatment with various concentrations of digoxin. (B) The histograms represent the number of colonies of A549 and H1299 cells following treatment with digoxin compared with those of control cells. (C) PBMCs were assessed by an MTT assay. The data are expressed as mean ± SD (n=3); ∗P<0.05, ∗∗P<0.01, ∗∗∗P<0.01, compared with the control.