For cell-cycle analysis, cells were harvested, fixed, incorporated with bromodeoxyuridine (BrdU), and stained with 7-aminoactinomycin D (BrdU Flow kit; BD Biosciences). The DNA content was analyzed using a cytofluorimeter, a fluorescence-activated cell sorter (FACScan; Becton Dickinson), and the ModFit software program (Verity Software House) (20 (link)). Terminal deoxynucleotidyl transferase dUTP nick end labeling staining (APO-BrdU kit; BD Biosciences) was performed to measure apoptosis, and bromodeoxyuridine incorporation was quantitated using fluorescence-activated cell sorting (BrdU Flow kits; BD Biosciences) according to the manufacturer's protocols.