Passage-matched Ccnd1+/+ or Ccnd1KI/KI MAF lines were infected with lentivirus containing vector control or h-Ras constructs. Cells were selected with puromycin for 14 days and assayed for β-galactosidase activity. DAPI serves as a control for cell number. Images were taken at 200× magnification with insets taken at 400× magnification. 