Figure 3. Treatment with the estrogen receptor antagonist, ICI 182,780, does not alter growth of passaged tumors, but transiently depletes the tumor subpopulation with basal characteristics.

(A) Schema of the in vivo treatment methodology. When transplanted tumor cells developed into tumors of 7mm in diameter, mice were treated with or without ICI 182,780 (ICI) as described in the Methods, and tumors were harvested after 2 or 14 days of treatment. (B) Uterine wet-weights of treated and untreated mice confirm the systemic anti-estrogenic activity of ICI 182,780 (N=3; mean±S.D.). (C) ICI did not alter the rate of growth of established tumors (Tumor 1 shown, Tumor 2 in Supplementary Fig. 2A). (N=3; mean±S.D.). (D) ICI did not alter the rate of proliferation in established tumors measured by Ki-67 staining. (N=3; mean±S.D.). (E) Flow cytometric analysis in response to in vivo ICI 182,780, 2 or 14 days after initiation of treatment (N=3; mean±S.D.). (F) Representative K5 and K8 immunofluorescence at 2 and 14 days after initiation of treatment. (G) Quantification of K8/K5 staining was performed as described in the Methods. N= 3 independent tumors. (Means±S.D. and statistical evaluations are shown in Supplementary Table 2).