Biological significance of progesterone receptor isoforms A and B in the normal ovary, and in benign, borderline, and malignant ovarian tumors

Hoh, Jeong Kyu; Kim, Kyung Tai

Abstract

OBJECTIVE
The differential expression patterns of the two progesterone receptor (PR) isoforms, PRA and PRB were examined using immunohistochemistry and real time quantitative RT-PCR in normal and neoplastic ovarian tissues, and in cell lines derived from epithelial ovarian cancer and breast cancer as a positive control in order to further elucidate the possible involvement of progesterone in the development of ovarian neoplasia.
METHODS
Breast cancer cell line MCF-7 and ovarian cancer cell line SNU-8 were seeded to 24-well plate with 5 X 10(5) cell/well and incubated overnight. Those cell lines were treated with 17-beta-estradiol and incubated for another 24 hrs. RNA were purified for RT-PCR and whole cell prepared total proteins were subject to immunoblot with DAB-staining. DNA ladder pattern and flowcytometry were studied to evaluate progestins induced apoptosis in the ovarian epithelium.
RESULTS
The median H-scores for PR isoforms in normal (n=8), benign (n=10), borderline (n=8) and malignant (n=24) ovarian tissues were as follows; PRA: 194.0, 171.0, 49.5, 0.0 (P<0.05), and PRB: 175.0, 180.5, 251.5, 168.5, respectively. In ovarian cancer cell line (SNU-8), PRB/PRAB mRNA ratio was not increased by 17-beta-estradiol, but that ratio was increased by 17-beta-estradiol in breast cancer cell line (MCF 7). Immunoblotting analysis demonstrated that PRB protein expression was markedly up- regulated in SNU-8, whereas the PRA and PRB isoforms both appeared to be increased in MCF-7. DNA ladder pattern was increased in dose and time related exposure of progestins and apoptotic cells were markedly increased during exposure progestins in ovarian cancer cell line were found by flowcytometry.
CONCLUSION
These results suggest that down-regulation of PRA is associated with the development of ovarian epithelial carcinoma. Progestins can activate the apoptotic pathway in the ovarian epithelium for protection of normal tissues from neoplatic transformation suggests that progestins deserve further evaluation as potential ovarian cancer preventive agents.