Induction of apoptosis by bisbibenzyls in PC3 cells. (A) Bisbibenzyls-induced apoptosis was detected by Giemsa staining. After exposure to different doses of Ric, Pak, Mar, and Pla for 24 h, cells were washed, fixed, and stained with Giemsa. Apoptotic cells were observed by microscopy. (B) Bisbibenzyls-induced apoptosis was quantified by flow cytometric analysis. After treatment with different doses of Ric, Pak, Mar, and Pla for 48 h, cells were harvested, stained with propidium iodide and analyzed by flow cytometry. Flow cytometric histograms are representative of two separate experiments.