Immunohistochemical staining was performed on 7, 30, and 200 day-old human prostate xenografts to assess prostate expression of essential hormone markers. The different times post-transplantation are shown in the columns, and the rows are the markers: estrogen receptor alpha (ER-alpha), estrogen receptor marker, A-C; androgen receptor (AR), androgen receptor marker, D-F. Punctate nuclear staining depicts positive cells. Hematoxylin counter-stain; scale bar = 50 μm; 7 day sample, 20 weeks gestation; 30 day sample, 23.7 weeks gestation; 200 day sample, 17 weeks gestation.