SC66 inhibits cell viability and colony forming capacity of HCC cells with IC50s of 0.77,0.47,0.92,0.75 and 2.85 μg/mL at 72 hours for HepG2, Hep3B, PLC/PRF/5,HA22T/VGH and Huh7 cells. HepG2, HA22T/VGH and PLC/PRF/5 cells have similar IC50s of approximately 0.85 and 0.75 μg/mL at 48 and 72 hours, respectively. To determine whether the decrease in cell viability is related to apoptosis induction, TUNEL assays are performed in Hep3B and Huh7 cells treated with 1, 2 and 4 μg/mL of SC66 for 24 hours. In Hep3B cells the number of TUNEL-positive cells increased with increasing concentrations of SC66, whereas in Huh7 cells very few light brown-colored cells are observed only after treatment with 4 μg/mL SC66.