Figure 1

Response of organotypic breast tumors to doxorubicin. (A) Ex vivo cultures of primary human breast tumors (n = 33) were incubated with 10 μM doxorubicin (Doxo) for the indicated time intervals, and analyzed for Ki-67 expression compared to baseline levels (T0), by immunohistochemistry. *P = 0.03; **P = 0.009 (unpaired t test). Each circle corresponds to an individual tumor. (B, C) Ex vivo tumor samples were analyzed for phosphorylation of histone H2AX (γH2AX) by immunofluorescence, with quantification of γH2AX-reactive cells after 48 h (C). **P = 0.002 (unpaired t test). (D) Responder breast tumors (n = 19) were treated with Doxo or vehicle (Ctrl) and analyzed for changes in cell proliferation by Ki-67 expression relative to T0 baseline at the indicated time intervals. Original magnification x200. (E) Quantification of Ki-67 expression in Responder breast tumors treated with Doxo or Ctrl for the indicated time intervals. *P = 0.02; **P = 0.0003 (unpaired t test). (F) Non Responder breast tumors (n = 14) were treated with Ctrl or Doxo, and analyzed for Ki-67 expression relative to T0 as in (D). Original magnification x200. (G) Quantification of Ki-67 expression in Non Responder breast tumors treated with Doxo or Ctrl for the indicated time intervals. (H) Responders and Non Responders breast tumors were analyzed for baseline Ki-67 immunoreactivity (% of positive nuclei). *P = 0.04 (Fisher’s exact test). For all experiments, bars represent mean ± SEM.