Taylor et al. BMC Cancer 2010, 10:541 http://www.biomedcentral.com/1471-2407/10/541 Page 8 of 12 Figure 2 Effects of 9cRA on cell proliferation and senescence in DLP of p27 deficient mice. Fig. 2A: Cell proliferation, as determined by Ki-67 antibody in DLP of 9-month-old p27+/+ mice. Note several Ki-67-positive cells (brawn-stained, arrows) in glandular structures which are covered by a single layer of epithelial cells. The slide is counterstained by hematoxylin × 200. 2B: Ki-67 positive cells (arrows) in anterior (large left) and DLP (two right glands) of 9-month-old p27-/- mice. Note the thick connective tissue surrounding glandular structures. The slide is counterstained by hematoxylin × 200. 2C: Ki-67 positive cells in PIN of MNU-treated mice. The number of Ki-67 positive cells is higher (arrow), as compared to those in Fig. 2B. The slide is counterstained by hematoxylin × 200. 2D: Treatment of p27-/- mice with 9cRA for 6 months reduced the number of Ki-67 positive cells in PIN (arrow). Note the inflammation associated cells in PINs’ lumen. The slide is counterstained by hematoxylin × 200. 2E: Senescent cells (blue stained) determined by SA-b-Gal staining in glandular and ductal structures of DLP of 9-month-old p27+/- mice. Senescent cells are also detectable among myoepithelial and stroma cells (arrows). The slide is counterstained by nuclear fast red × 200. 2F: Treatment of animals with 9cRA increased senescent cells (blue stained) in DLP and AP of a p27+/- mice. The slide is counterstained by nuclear fast red × 200. 2G: 9cRA increased senescent cells in low grade PIN (arrows) as compared to non-PIN areas of a 10-month-old p27+/- animal. The slide is counterstained by nuclear fast red × 200. 2H: 9cRA also increased senescent cells in high grade PIN as shown in the right glandular structure. The slide is counterstained by nuclear fast red × 200.