Effect of HIPK2 on cell death and survival after cobalt treatment. RKO-C, RKO-p53i, and T98G cells were transfected with HIPK2-GFP or K221R-GFP expression vectors. Twelve hours after transfection cells were treated with CoCl2 (200 μM) for 24 h. Thirty-six hours after transfection cells cell viability was assayed by Trypan blue exclusion. The results shown are representative of three independent experiments performed in duplicate. (B) Colony-forming ability of RKO-C, RKO-p53i, and T98G cells transfected and treated as in (A). Death-resistant colonies were stained with crystal violet 14 days after transfection.