Fenretinide causes caspase-3 cleavage and DNA double-strand breaks in Huh-7 cells but not in HepG2 cells. Huh-7 and HepG2 cells were treated with either DMSO or fenretinide and analysed for caspase-3 cleavage by Western blot (A)and DNA double-strand breaks by TUNEL assay (B). TUNEL positive counting was presented as a relative fold of DMSO treatment, and the staining was representative result of two independent experiments. Data were shown as mean ± S.E.M. (* p < 0.05, ** p < 0.01 compared with DMSO treatment).