Fig. 3.

Loss of Rb in MEFs decreases senescence, enhances cell proliferation, and increases cell survival. (A) MEFs grown at 3% or 21% oxygen were stained for β-galactosidase. At least 500 cells from 5 different fields of view were counted, and the percentage of senescent cells was plotted. (B) MEFs were grown at 21% O₂ and were assessed by the 3T3 assay to investigate spontaneous immortalization. Cumulative growth was plotted for each MEF line.