Analysis of the cell cycle of BL cell lines, transduced either with RBL2/p130 (B) or with the empty vector (A), as a negative control, obtained by FACS analysis. Briefly, each cell-cycle phase is distinguishable on the basis of DNA content because propidium iodide (PI) stoichiometrically binds to DNA, making it possible to discriminate between dividing and nondividing cells. Each cell-cycle stage is graphically represented as a distinct peak on the graph. Percentages of cells in each cell-cycle stage are reported in Table 2. Notably, RBL2/p130 induces an increase in the G₀/G₁ fraction, thus suggesting a reduction of the proliferation rate.