Estrogen Inhibits Epithelial Progesterone Receptor-Dependent Progestin Therapy Efficacy in a Mouse Model of Cervical Cancer

Abstract

Although the uterine cervix responds to the female sex hormone change, the role of progesterone in cervical cancer is poorly understood. It has been shown that medroxyprogesterone acetate (MPA) regresses cervical cancer in the transgenic mouse model expressing human papillomavirus type 16 E6 and E7 oncogenes. As MPA interacts most strongly with progesterone receptor (PR), we reasoned that PR would contribute to MPA-induced regression of cervical cancer. We also hypothesized that estrogen influences the therapeutic activity of MPA because it promotes cervical cancer growth in the same mouse model. The present study showed that the deletion of Pgr in the cervical cancer cells ablated the MPA's therapeutic effect in the human papillomavirus transgenic mouse model. Additionally, estrogen attenuated cancer regression by MPA in the same model system. These observations indicate that MPA can effectively regress cervical cancer only when cancer cells express PR and estrogen levels are low. These results suggest that, if translatable, MPA should be administered when estrogen levels are low in patients with PR-positive cervical cancer.

Figure 1

Medroxyprogesterone acetate (MPA) fails to regress progesterone receptor (PR)–negative cervical cancer. A: Schematic show modified alleles in each genotype. B: Treatment regimens are depicted. C: PR is not expressed in cervical cancer cells in E7/Cre/Pgr^f/− mice. Cancer sections from the cervical canal were stained for PR (green). Nuclei were stained with Hoechst 33258 and pseudocolored red. White lines separate cervical cancer (cc) from surrounding stroma (st). D: Shown are high-magnification images of representative hematoxylin and eosin–stained cervical cancers. Note that there were no cancers in MPA-treated E7/Pgr^f/− mice. E: Cervical cancer sections were stained with Alcian blue. Nuclei were stained with nuclear fast red. Scale bars: 50 μm (C and E); 100 μm (D). E, estrogen; PBS, phosphate-buffered saline.

Figure 2

Exogenous estrogen (E) inhibits medroxyprogesterone acetate (MPA)–mediated regression of progesterone receptor–positive cervical cancer. A: The treatment regimen is shown. B: Cervical cancer sections in each group were stained with hematoxylin and eosin. C: Cervical cancer sections were stained with an anti-K10 antibody (green). Hoechst 33258–stained nuclei were pseudocolored red. White lines show the boundary of cervical cancer (cc). D: Cervical cancer sections were subjected to Alcian blue staining. Nuclei were counterstained with nuclear fast red. Scale bars = 50 μm (B–D).

Figure 3

Medroxyprogesterone acetate (MPA) inhibits cervical cancer growth in the presence of exogenous estrogen (E). A: Tumor multipolicy in each group is shown in a box plot. There was no statistically significant difference among groups. Light and dark gray boxed areas represent E7/Pgr^f/− and E7/Cre/Pgr^f/− genotypes, respectively. See Figure 2A for treatment regimens for E and MPA/E groups. B: A box plot was used to show total cancer area in each group. Dots represent outliers. Note that total cancer area in E7/Pgr^f/− mice in MPA/E group was significantly smaller compared with the other groups. Group sizes are indicated in the graph. C: Cervical sections were stained for bromodeoxyuridine (BrdU), and the results were quantified. More than 500 cells per cancer in average were counted. P value is compared with the other groups. D: Terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) assay results were quantified. There was no statistically significant difference among groups. E: Model for the interplay between E and progesterone (P). See text for details. Results are shown as means ± SEM (A–D). n = 4 (C); n = 3 (D). ^∗P < 0.05. ER, estrogen receptor.

Supplemental Figure S1

A: Cervical epithelial sections in E7/Cre/Pgr^f/− mice were stained with hematoxylin and eosin. Note that the epithelium in the disease-free mouse is hypoplastic, unlike a diseased mouse. F288 and F292 are histology sample identifiers. B: The disease-free mouse sample shown in A was stained for progesterone receptor (green). A tissue section from E7/Cre/Pgr^f/− mice was used as positive control. Nuclei were counterstained with Hoechst 33258 and pseudocolored red. White lines separate epithelium (ep) and stroma (st). Scale bars: 100 μm (A); 30 μm (B).

Supplemental Figure S2

A: Shown are representative images of hematoxylin and eosin–stained cervical epithelia. Note that E7/Cre/Pgr^f/− mice in medroxyprogesterone acetate (MPA) group had epithelial cells with clear cytoplasm similar to E7/Pgr^f/− mice (black arrows). B: Cervical sections were stained with Alcian blue. Nuclei were counterstained with nuclear fast red. Black lines separate epithelium (ep) and stroma (st). C: Cancer sections from cervical canal were stained for progesterone receptor (green). Nuclei were counterstained with Hoechst 33258 and pseudocolored red. White lines separate ep and st. Scale bars: 25 μm (A); 50 μm (B and C).