Anti-PLSCR1 induces G1/S arrest and activates the tumor suppressor protein, pRb. (A) Cell-cycle distributions of HT29 cells at different time points after the addition of NP1 are shown. DNA content was analyzed by the EXPO32 ADC Software (EPICS XL-MCL, Beckman Coulter). Data are presented as the mean ± SD calculated from three experiments. Cells treated with NP1 accumulated higher percentage of cells in G1 at 12 h compared with cells treat with isotype-control IgG. (B) Western blot analysis of cyclin D1, total pRb, and phosphorylated pRb after cells were treated with NP1 or isotype-control IgG is shown. Actin was used as a loading control.