Figures and Tables
Figure 1  Effect of chemopreventive agents on mammary tumor formation in the NMU rat model of mammary tumorigenesis. Rats were administered NMU at 8 weeks of age (time t = 0), and were randomized into six groups which were given the following chemopreventive agents continuously in their diet, starting 1 week after initiation: no additions (unfilled circle), 4-HPR (filled circle), 9cRA (unfilled square), tamoxifen (filled square), 4-HPR + tamoxifen (unfilled triangle), or 9cRA + tamoxifen (filled triangle). Rats were weighed and palpated for tumors each week. (a) Percentage of rats with palpable tumors. (b) Mean number of tumors per rat. (c) Mean weight of rat. The open arrow indicates the start of the chemopreventive intervention.
Figure 2  Immunohistochemical analysis of TGF-β expression in the rat mammary gland. The first thoracic (number 2) mammary gland was harvested from 15-week-old rats that had been treated with NMU at age 8 weeks. Sections were immunostained (see Materials and method), with the following antisera: (a) anti-TGF-β1-LC (stains predominantly intracellular TGF-β1); (b) anti-TGF-β1-CC (stains extracellular TGF-β1); (c) anti-TGF-β2; (d) anti-TGF-β3; (e) anti-LTBP; and (f) normal rabbit immunoglobulin. The brown stain indicates a positive immunoperoxidase reaction. Images were shot at 630× original magnification.
Figure 3  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.
Figure 4  Treatment with tamoxifen affects the histology of the rat mammary gland. Representative hematoxylin and eosin stained sections of the first thoracic gland of 15-week-old rats that had undergone the following treatments: (a, b) No treatment; moderate numbers of mammary gland lobules are present containing primary, secondary and tertiary ductules, as well as developing alveoli. (c, d) Initiation with NMU at 8 weeks of age; no significant histologic differences are noted in mammary gland development from that in untreated control animals. (e, f) Initiation with NMU at 8 weeks, followed by treatment with tamoxifen from 9 to 15 weeks of age; scant numbers of atrophic primary and secondary mammary gland ductules are noted, with no alveolar bud development evident. (a, c, e) Shot at 100×; and (b, d, f) shot at 400× original magnification.