Progesterone receptor regulates Bcl-2 gene expression through direct binding to its promoter region in uterine leiomyoma cells.
BACKGROUND
Uterine leiomyomas are smooth muscle cell tumors that cause irregular uterine bleeding and pregnancy loss in many reproductive-age women. Progesterone stimulates their growth, whereas treatment with progesterone receptor (PR) antagonists or selective progesterone receptor modulators shrinks these tumors. Molecular mechanisms underlying these observations are unknown.


OBJECTIVE
Bcl-2 is a key protein that inhibits apoptosis. It was proposed that growth enhancement of leiomyoma cells by progesterone was mediated via bcl-2 induction. Here we test the hypothesis that PR regulates the bcl-2 gene by directly binding to its promoter.


RESULTS
The pure progesterone agonist R5020 increased the total number of viable primary human leiomyoma smooth muscle (LSM) cells in culture. Progesterone or R5020 (10(-6) m) significantly increased bcl-2 mRNA levels after 2 and 4 h by 9.2- and 3.4-fold, respectively, in LSM cells. Transient transfection with deletion mutants of bcl-2 promoter showed that the -1281/-258-bp region conferred responsiveness to progesterone induction in the presence of PR-A. We identified a palindromic progesterone response element (PRE) at -553/-539 bp. EMSA showed that PR in nuclear extracts from LSM cells bound specifically to this PRE. Chromatin immunoprecipitation-PCR confirmed in situ recruitment of PR to the -629/-388-bp region bearing the PRE. In vivo, bcl-2 mRNA levels correlated significantly with total PR mRNA levels in leiomyoma tissues.


CONCLUSIONS
Taken together, progesterone via PR interacts with the bcl-2 promoter to induce its expression in leiomyoma tissue. This may explain, in part, the progesterone-dependent enhancement of growth in uterine leiomyoma.
Yin
Ping
P
Division of Reproductive Biology Research, Department of Obstetrics and Gynecology, Feinberg School of Medicine at Northwestern University, Chicago, Illinois 60611, USA.
Lin
Zhihong
Z
Cheng
You-Hong
YH
Marsh
Erica E
EE
Utsunomiya
Hiroki
H
Ishikawa
Hiroshi
H
Xue
Qing
Q
Reierstad
Scott
S
Innes
Joy
J
Thung
Stephen
S
Kim
J Julie
JJ
Xu
Eugene
E
Bulun
Serdar E
SE
D015153:Blotting, Western; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects; D047369:Chromatin Immunoprecipitation; D024202:Electrophoretic Mobility Shift Assay; D005260:Female; D005786:Gene Expression Regulation / Q000235:genetics / Q000502:physiology*; D019254:Genes, bcl-2 / Q000235:genetics*; D006801:Humans; D007889:Leiomyoma / Q000235:genetics* / Q000378:metabolism; D008156:Luciferases / Q000235:genetics; D011374:Progesterone / Q000494:pharmacology; D011397:Promegestone / Q000494:pharmacology; D011401:Promoter Regions, Genetic / Q000235:genetics*; D012333:RNA, Messenger / Q000096:biosynthesis / Q000235:genetics; D011980:Receptors, Progesterone / Q000819:agonists / Q000502:physiology*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014162:Transfection; D014594:Uterine Neoplasms / Q000235:genetics* / Q000378:metabolism