Gonadotropin-releasing hormone type II induces apoptosis of human endometrial cancer cells by activating GADD45alpha.
Gonadotropin-releasing hormone type II (GnRH-II) has an antiproliferative effect on human endometrial cancer cells. Apoptosis in cancer cells may play a critical role in regulating cell proliferation. However, more studies are necessary to elucidate the underlying molecular mechanisms and develop potential applications of GnRH-II. Therefore, we explored the mechanisms of GnRH-II-induced apoptosis and the effects of GnRH-II on GADD45alpha activation in human endometrial cancer cell lines. GnRH-II decreased cell viability in a dose- and time-dependent manner. Apoptosis was induced with increased terminal deoxyribonucleotidyl transferase-mediated dUTP nick end labeling apoptotic cells after GnRH-II treatment. Knockdown of the endogenous GnRH-I receptor with small interfering RNA (siRNA) rescued the cells from GnRH-II-mediated cell growth inhibition and abolished the induction of apoptosis. GnRH-II activated extracellular signal-regulated kinase (ERK)-1/2 and p38 mitogen-activated protein kinase (MAPK) in a time-dependent manner, and the activation was abolished by GnRH-I receptor siRNA and MAPK inhibitors. Cells pretreated with MAPK inhibitors were rescued from GnRH-II-mediated cell growth inhibition. Moreover, both inhibitors abolished GnRH-II-induced apoptosis. GnRH-II induced GADD45alpha expression, which was abolished by knockdown of endogenous GnRH-I receptors and MAPK inhibitors. GnRH-II-stimulated cell growth inhibition was rescued by knockdown of endogenous GADD45alpha with siRNA. Cells treated with GADD45alpha siRNA were refractory to GnRH-II-induced apoptosis. Thus, GnRH-II inhibits cell growth by inducing apoptosis through binding of the GnRH-I receptor, activation of the ERK1/2 and p38 MAPK pathways, and induction of GADD45alpha signaling. This finding may provide a new concept relating to the mechanism of GnRH-II-induced antiproliferation and apoptosis in endometrial cancer cells, indicating the possibility of GnRH-II as a promising therapeutic intervention for human endometrial cancer.
Department of Obstetrics and Gynecology, University of British Columbia, Vancouver, British Columbia, Canada.
Hsien-Ming
HM
Wu
Jung-Chien
JC
Cheng
Hsin-Shih
HS
Wang
Hong-Yuan
HY
Huang
Colin D
CD
MacCalman
Peter C K
PC
Leung
D017209:Apoptosis / Q000187:drug effects / Q000502:physiology*; D002455:Cell Division / Q000187:drug effects; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects; D016889:Endometrial Neoplasms / Q000201:enzymology / Q000235:genetics / Q000473:pathology*; D005260:Female; D007987:Gonadotropin-Releasing Hormone / Q000031:analogs & derivatives* / Q000494:pharmacology; D006801:Humans; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D034741:RNA, Small Interfering / Q000235:genetics; D011966:Receptors, LHRH / Q000172:deficiency / Q000235:genetics / Q000502:physiology; D014162:Transfection; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism
C484844:GNRHR protein, human; D034741:RNA, Small Interfering; D011966:Receptors, LHRH; D007987:Gonadotropin-Releasing Hormone; C047717:LHRH, His(5)-Trp(7)-Tyr(8)-; D020928:Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases