Lack of effect of chemopreventive agents on expression of TGF-βs in the NMU-initiated rat mammary gland. Immunohistochemical staining intensity for TGF-βs and LTBP was determined after 6 weeks of treatment with the following chemopreventive agents: None (C); 4-HPR (H); 9cRA (R); tamoxifen (T); 4-HPR + tamoxifen (T/H); 9cRA + tamoxifen (T/R). Staining intensity was determined independently for the ductal epithelial cells and the periductal stroma (see Materials and method). Staining intensity ranged from 0 to 4 (max). Results are given as the mean ± SD for five or six rats/group. TGF-β1-LC is an antibody that predominantly recognizes intracellular TGF-β1, whereas TGF-β1-CC recognizes extracellular TGF-β1.