Progesterone Receptor Regulates Bcl-2 Gene Expression Through Direct Binding to Its Promoter Region in Uterine Leiomyoma Cells

J Clin Endocrinol Metab. 2007 Nov;92(11):4459-66. doi: 10.1210/jc.2007-0725. Epub 2007 Sep 4.

Abstract

Context: 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.

Conclusion: 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.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Blotting, Western
  • Cell Line, Tumor
  • Cell Survival / drug effects
  • Chromatin Immunoprecipitation
  • Electrophoretic Mobility Shift Assay
  • Female
  • Gene Expression Regulation / genetics
  • Gene Expression Regulation / physiology*
  • Genes, bcl-2 / genetics*
  • Humans
  • Leiomyoma / genetics*
  • Leiomyoma / metabolism
  • Luciferases / genetics
  • Progesterone / pharmacology
  • Promegestone / pharmacology
  • Promoter Regions, Genetic / genetics*
  • RNA, Messenger / biosynthesis
  • RNA, Messenger / genetics
  • Receptors, Progesterone / agonists
  • Receptors, Progesterone / physiology*
  • Reverse Transcriptase Polymerase Chain Reaction
  • Transfection
  • Uterine Neoplasms / genetics*
  • Uterine Neoplasms / metabolism

Substances

  • RNA, Messenger
  • Receptors, Progesterone
  • Progesterone
  • Promegestone
  • Luciferases