Figure 5.

Response of MCF-7 and MCF-7CLU cells grown as orthotopic xenografts to tamoxifen. Panel A: Ovariectomized nude mice supplemented with slow release estradiol pellets (1.7 mg/90 day) were inoculated with MCF-7 or MCF-7CLU cells and allowed to grow for 4-5 weeks. *P < 0.05; MCF-7 vs MCF-7CLU. (n = 10-12). Panel B: Ovariectomized nude mice supplemented with slow release estradiol pellets (1.7 mg/90 day) were inoculated with MCF-7 or MCF-7CLU cells and allowed to grow for 4-5 weeks until tumors measured 200 mm³. Animals were implanted with slow release placebo or tamoxifen pellets. Results are expressed as mean ± SD. *P < 0.05 (control versus treated, n = 10). Panel C: Formalin-fixed sections from placebo or tamoxifen treated MCF-7 or MCF-7CLU tumors were labeled for cellular proliferation using PCNA. Representative sections stained for PCNA (scale bar: 50 micrometers). Positive cells were counted as a percentage of total cells. A minimum of 500 cells from each of two sections from four mice per treatment group were evaluated. *P < 0.05 control vs treated. Panel D: Formalin-fixed sections from placebo or tamoxifen (15 mg/60 day) treated MCF-7 or MCF-7CLU tumors, excised after 10 weeks of treatment, were TUNEL labelled. Representative TUNEL-stained sections (scale bar: 50 micrometers). Positive cells were counted as a percentage of total cells. A minimum of 500 cells from each of two sections from four mice per treatment group were evaluated. *P < 0.05 control vs treated.