GE and TAM inhibited the expression of PCNA and increased ERα expression in vivo . Immunohistochemical analysis was performed in tumor samples to detect PCNA-positive cells for proliferation index (left panel) and ERα in vivo expression (right panel). A) and B) PCNA and ERα expression in MDA-MB-231 tumor xenogratfs (Protocol 1). C) and D) PCNA and ERα expression in C3(1)-SV40 Tag transgenic mice tumors (Protocol 2). Immunohistochemical data in terms of percentage of positive cells are presented as mean ± SD from each group. PCNA-positive and ERα-positive cells were counted in 5 different areas of the sections, and data are summarized in terms of percent positive cells from all tumor samples. Representative photograph from one field of each experimental group. Columns, mean; Bars, SD from 5 or 10 mice per group; *, p < 0.05 significantly different from control group. †, P < 0.05, significantly different from TAM alone group.