title: Potentiation response of cultured human uterine leiomyoma cells to various growth factors by endothelin-1: role of protein kinase C.
abstract: OBJECTIVE
  Factors responsible for the abnormal proliferation of myometrial cells that accompanies leiomyoma formation are unknown, although steroid hormones and peptide growth factors have been implicated. We hypothesized that endothelin-1 (ET-1) is a physiological regulator of tumor growth.
  
  
  METHODS
  In this study, we investigated the role of ET-1 on growth of human leiomyoma cells and its synergistic effect with growth factors, as well as the signaling pathway involved in this interaction.
  
  
  METHODS
  Leiomyoma cell proliferation was assayed by [H]thymidine incorporation and cell number. Protein kinase C (PKC) isoforms were analyzed by Western blot using specific antibodies.
  
  
  RESULTS
  ET-1 on its own was unable to stimulate DNA synthesis but potentiated the leiomyoma cell growth effects of basic fibroblast growth factor (bFGF), epidermal growth factor (EGF), IGF-I and IGF-II. The failure of a protein tyrosine kinase (PTK) inhibitor, tyrphostin 51, to affect the potentiating effect of ET-1, supports the hypothesis of non-involvement of PTK in this process. The inhibition of PKC by calphostin C or its down-regulation by phorbol 12,13-dibutyrate (PDB) eliminated the potentiating effect of ET-1, but did not block cell proliferation induced by the growth factors alone. Five PKC isoforms (alpha, beta1, epsilon, delta and zeta) were detected in leiomyoma cells, but only phorbol ester-sensitive PKC isoforms (PKCalpha, epsilon and delta) contribute to the potentiating effect of leiomyoma cell growth by ET-1.
  
  
  CONCLUSIONS
  We have demonstrated that ET-1 potentiates leiomyoma cell proliferation to growth factors through a PKC-dependent pathway. These findings suggest a possible involvement of ET-1 in the pathogenesis of leiomyomas.
authors.affiliation: INSERM U.361, Universite Rene-Descartes, Pavillon Baudelocque, Paris, France.
authors.forename: I
authors.initials: I
authors.lastname: Eude
authors.forename: E
authors.initials: E
authors.lastname: Dallot
authors.forename: M C
authors.initials: MC
authors.lastname: Vacher-Lavenu
authors.forename: C
authors.initials: C
authors.lastname: Chapron
authors.forename: F
authors.initials: F
authors.lastname: Ferre
authors.forename: M
authors.initials: M
authors.lastname: Breuiller-Fouche
mesh_terms: D015153:Blotting, Western; D002455:Cell Division / Q000187:drug effects; D004273:DNA, Neoplasm / Q000096:biosynthesis; D019332:Endothelin-1 / Q000494:pharmacology*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005260:Female; D006133:Growth Substances / Q000494:pharmacology*; D006801:Humans; D007889:Leiomyoma / Q000378:metabolism / Q000473:pathology*; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000502:physiology*; D011505:Protein-Tyrosine Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects; D014407:Tumor Cells, Cultured; D014594:Uterine Neoplasms / Q000378:metabolism / Q000473:pathology*
chemical_list: D004273:DNA, Neoplasm; D019332:Endothelin-1; D004791:Enzyme Inhibitors; D006133:Growth Substances; D011505:Protein-Tyrosine Kinases; D011493:Protein Kinase C