Differential p53 pathway activation in organotypic breast tumors. (A) Immunohistochemical analysis of differential expression of p53, p21Waf1 or MDM2 in control (Ctrl)- or doxorubicin (Doxo)-treated breast tumors after 48 h. Tissue morphology and proliferative index were determined by hematoxylin and eosin (H&E) and Ki-67 staining of the same cases, respectively. A representative case for Non Responder (left) or Responder (right) breast tumors ex vivo is shown. Original magnification, x200. (B-D) Quantification of p53 (B), p21Waf1 (C) or MDM2 (D) proteins levels in Ctrl or Doxo-treated Responder versus Non Responder breast tumors at the indicated time intervals. #P = 0.03 *P = 0.01; **P = 0.007 (unpaired t test).