(A) Cumulative cell size distributions of HLF cells arrested in G1 phase for 0 to 9 days with 1μM of the CDK4/6 inhibitor Palbociclib. (B) A representative immunoblot showing the accumulation of senescence markers p16 and p21 in the HLF cells that increase in size upon Palbociclib arrest. (C, D) Cell size distributions (C) and SA-beta-Gal staining images (D) of the RPE-1 cells treated for 8 days with DMSO or Palbociclib, in the presence or absence of Rapamycin to determine the effect of cell size reduction on senescence dynamics. (E) Effect of Rapamycin, which reduces cell growth, on the percentage (±standard error) of SA-beta-Gal positive cells in RPE-1 cultures treated with Palbociclib for 8 days. Values shown next to each condition indicate the mean cell sizes after 8 days of treatment. SA-beta-Gal quantification for every data point in included 700–1200 cells quantified from 9 different fields of view. Values shown next to each condition indicate the mean cell sizes after 8 days of treatment. (F-H) Effects of Rapamycin on the expression of senescence markers p21 and p16 in HLF cells that were treated with Palbociclib for 8 days to increase cell size. (F) Immunofluorescent staining against p21 in HLF cells. Scale bar = 10μm. (G) A representative immunoblot against p21 and p16. (H) Quantification of p21 and p16 immunoblots. Data are shown as mean ± standard error, n = 4 biological replicates.