Caption: A: Apoptosis increases after 16 hours of MPA treatment. Cervical sections were subjected to TUNEL assay to detect apoptotic cells. Cells with green staining indicate apoptotic cells. Note that there are more apoptotic cells in the MPA-treated cervix. Nuclei were stained blue. White dotted lines demarcate the border between the epithelium (ep) and stroma (st). B: Cervical tissue sections were stained with hematoxylin and eosin (H&E). Note that MPA induces hypoplasia (i.e., thin epithelium) only in progesterone receptor (PR)-positive mice (Pgr+/-). However, in PR-negative mice (Pgr-/-), cervical epithelium is as hyperplastic as vehicle-treated mice, and cervical cancer is present.