(A) TUNEL (terminal deoxynucleotidyl transferase–mediated deoxyuridine triphosphate nick end labeling) staining of tumors from group 3 (ICb-2555MB) and group 4 (ICb-1078MB) models before digoxin treatment, during treatment, or at time of recurrence. Scale bar, 25 mM. (B and C) Quantitation of TUNEL staining from group 3 (ICb-2555MB) (B) and group 4 (ICb-1078MB) (C). hpf, high-power field. (D and E) Heatmaps depicting changes gene expression in group 3 tumor (D) (ICb-2555 MB) and group 4 (E) (ICb-1078MB) tumors before and after digoxin treatment. Red text denotes genes that are differentially expressed in both groups 3 and 4 MB. For the heatmap, red indicates up-regulation, and green indicates down-regulation.