[Effect of mifepristone on the expression of progesterone receptor messenger RNA and protein in uterine leiomyomata].

OBJECTIVE

To determine the expression of progesterone receptor (PR) mRNA and PR protein levels in the myometrium and leiomyomata from untreated and mifepristone pretreated women with leiomyoma and to examine the mechanism of mifepristone treatment on uterine leiomyomata.

METHODS

Expression of PR mRNA and PR protein were determined by Northern blot and HAP of single-dose saturated analysis in myometrium and leiomyomata (center and marginal area) from 27 untreated and 6 mifepristone pretreated women with leiomyomata.

RESULTS

PR mRNA abundance and PR protein levels in both myomatous center and marginal area were significantly greater than those in corporal myometrium (P < 0.01) in both follicular and luteal phases, but similar between myomatous center and marginal area (P > 0.05). 6 cases pretreated with mifepristone 25 mg/day for 3 months were operated, all but one patient displayed a decrease in leiomyomata volume. PR mRNA abundance in both myometruim and leiomyomata (center and marginal area) was significantly decreased in 4 patients continuing mifepristone treatment before the operation but not in the other 2 patients stopping RU486 1 month before operation. PR protein levels in these tissues showed significant decrease in all 6 cases.

CONCLUSION

There are overexpression of PRmRNA and PR protein in leiomyomata. One of the mechanism of mifepristone action on decreasing leiomyomata volume may be related to suppression on expression of PR gene. It seems that suppression on transcription of PR gene is reversible, but on translation of PR gene may maintain in a relatively longer period.