GLI1 and prostate cancer: The urogenital sinus mesenchyme (UGM) of either ArL/Y:Gli1CreER/+ (ARKO) mice14, with tamoxifen (TM) induced Ar deletion in Gli1-expressing cells, or Gli1CreER/+ controls, and the urogenital sinus epithelium (UGE) of Ctnnb1L(ex3)/+:PBCre4 mice, a prostate cancer model, with stabilized β-catenin expressed in prostate epithelium were isolated at E16.5, and transplanted together under the renal capsule of NOD/SCID mice (Fig. 1a).