Induction of apoptosis in Huh-7 cells by cyproheptadine. (A) Annexin V staining assay. Cyproheptadine-treated HCC cells were stained with annexin V–FITC and analyzed by fluorescence microscopy. Untreated cells were primarily negative for annexin V staining, indicating that they were viable and not undergoing apoptosis. Treated cells undergoing apoptosis were observed to have positive annexin V staining. (B) Western blot analysis of PARP expression in cyproheptadine-treated HCC cells. The levels of PARP and its cleaved form increased significantly in Huh-7 cells after 18–30 h of treatment, but decreased in HepG2 cells after 24–30 h of treatment.