Endothelin (ET)-1 and ET-3 promote expression of c-fos and c-jun in human choriocarcinoma via ET(B) receptor-mediated G(i)- and G(q)-pathways and MAP kinase activation.
OBJECTIVE
Endothelins (ETs) and their G protein-coupled receptors exert key physiological functions during normal and aberrant placental development. Trophoblast cells mediate the contact between the embryo and the mother, by establishing a transient organ, the placenta. Choriocarcinoma cells display many of the biochemical and morphological characteristics of in utero invasive trophoblast cells and may therefore be used as a suitable model to study epithelial tumour progression of foetal-derived cells.


METHODS
The present study aimed at investigating ET receptor-mediated activation of the mitogen-activated protein kinase (MAPK) pathway in human choriocarcinoma.


RESULTS
Both JAR and Jeg-3 choriocarcinoma cell lines expressed ET receptor subtype B (ET(B)) but not ET(A) receptor transcripts. ET(B) receptor engagement by ET-1 and ET-3 resulted in a similar time- and concentration-dependent phosphorylation of p42/44 MAPK, also known as extracellular regulated kinase 1/2. Using specific pharmacological antagonists/inhibitors, we showed that ET-1/-3-mediated signal transduction by the ET(B) receptor is transmitted via G(i)- and G(q)-dependent pathways through activation of the Src (G(i)) and protein kinase C (G(q)) axis that converge at Ras/Raf, leading to downstream activation of p42/44. On a functional level, ET(B) engagement and subsequent phosphorylation of p42/44 resulted in enhanced transcription of the immediate early response genes c-fos and c-jun, a process commonly assumed to be mediated by the ET(A) receptor, and increased cell growth and relative cell area.


CONCLUSIONS
As human choriocarcinoma cells secrete ETs, pharmacological antagonism of ETs and/or ET(B) receptor-mediated signal transduction could represent a likely target therapy for choriocarcinoma.
Rauh
A
A
Center of Molecular Medicine, Institute of Molecular Biology and Biochemistry, Medical University of Graz, Graz, Austria.
Windischhofer
W
W
Kovacevic
A
A
DeVaney
T
T
Huber
E
E
Semlitsch
M
M
Leis
H-J
HJ
Sattler
W
W
Malle
E
E
D015153:Blotting, Western; D002452:Cell Count; D045744:Cell Line, Tumor; D002465:Cell Movement / Q000187:drug effects; D002822:Choriocarcinoma / Q000235:genetics*; D017931:DNA Primers; D019332:Endothelin-1 / Q000494:pharmacology*; D019334:Endothelin-3 / Q000494:pharmacology*; D019206:GTP-Binding Protein alpha Subunits, Gi-Go / Q000502:physiology*; D043802:GTP-Binding Protein alpha Subunits, Gq-G11 / Q000502:physiology*; D015870:Gene Expression / Q000187:drug effects*; D016762:Genes, fos / Q000187:drug effects*; D016758:Genes, jun / Q000187:drug effects*; D006801:Humans; D020928:Mitogen-Activated Protein Kinases / Q000502:physiology*; D012313:RNA / Q000096:biosynthesis / Q000302:isolation & purification; D044023:Receptor, Endothelin B / Q000235:genetics*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology; D013778:Tetrazolium Salts; D013844:Thiazoles
D017931:DNA Primers; D019332:Endothelin-1; D019334:Endothelin-3; D044023:Receptor, Endothelin B; D013778:Tetrazolium Salts; D013844:Thiazoles; D012313:RNA; D020928:Mitogen-Activated Protein Kinases; D019206:GTP-Binding Protein alpha Subunits, Gi-Go; D043802:GTP-Binding Protein alpha Subunits, Gq-G11; C022616:thiazolyl blue