Figure 5.

TGF-β1 depletion results in increased frequency of ER-α-positive mammary epithelial cells in cycle in parous mice. Ki-67 and ER-α/Ki-67 co-localization frequency in mammary epithelium of parous Tgfβ1 heterozygote (+/−) and Tgfβ1 wild-type (+/+) C57BL/6–129SV mice at estrus. These animals were sacrificed 3 weeks after weaning. Four animals per genotype and at least 250 cells per animal were scored for presence of ER-α and Ki-67 immunoreactivity. Asterisk indicates significant difference from Tgfβ1 wild-type mean frequency (P < 0.05; t-test).