Figure 8.

Effects of early and late deletion of mouse Cripto-1 on progesterone receptor (PR) expression. Representative PR-positive cells. A: Immunohistochemical analysis of mammary tissue collected from FVB/N, whey acidic protein-Cre⁺/Cripto^flox (WAP-CRKO), and MMTV-Cre⁺/Cripto^flox (MMTV-CRKO) mice at the indicated times: 10-week-old nulliparous females (10 wk), 6 days pregnancy (Early preg.), 15 days pregnancy (Late preg.), one day lactation (1D lac.), and 3 days involution (Early Inv.). Tissue was fixed and processed for PR expression, as described in Materials and Methods. Arrowheads indicate representative PR-positive cells. B: PR-positive cells were scored, and labeling index was expressed as a percentage of positive nuclei from 3000 counted cells. PR levels were significantly lower in the mouse Cripto-1 KO mice than FVB/N mice. C: Effect of Cripto-1 on PR expression. 293T cells were transiently transfected with a PR promoter luciferase reporter vector, in the presence or absence of mouse Cripto-1 expression vector. Data show significant increase in PR promoter activity in presence of mouse Cripto-1 expression vector is present. The results are the means ± SEM from two independent experiments with triplicate samples per experiment (B and C). ^∗P < 0.05. Original magnification, ×100 (A).