Gonadotropin-releasing hormone induces apoptosis of prostate cancer cells: role of c-Jun NH2-terminal kinase, protein kinase B, and extracellular signal-regulated kinase pathways.
A standard therapy used today for prostate cancer is androgen ablation by gonadotropin-releasing hormone analogs (GnRH-a). Although most patients respond to androgen ablation as an initial systemic therapy, nearly all cases will develop androgen resistance, the management of which is still a major challenge. Here, we report that GnRH-a can directly induce apoptosis of the androgen-independent prostate cancer-derived DU145 and PC3 cell lines. Using specific inhibitors, we found that the apoptotic effect of GnRH-a is mediated by c-Jun NH2-terminal kinase (JNK) and inhibited by the phosphatidylinositol 3'-kinase (PI3K)-protein kinase B (PKB) pathway. Indeed, in DU145 cells, GnRH-a activates the JNK cascade in a c-Src- and MLK3-dependent manner but does not involve protein kinase C and epidermal growth factor receptor. Concomitantly, GnRH-a reduces the activity of the PI3K-PKB pathway, which results in the dephosphorylation of PKB mainly in the nucleus. The reduction of PKB activity releases PKB-induced inhibition of MLK3 and thus further stimulates JNK activity and accelerates the apoptotic effect of GnRH-a. Interestingly, extracellular signal-regulated kinase is also activated by GnRH-a, and this occurs via a pathway that involves matrix metalloproteinases and epidermal growth factor receptor, but its activation does not affect JNK activation and the GnRH-a-induced apoptosis. Our results support a potential use of GnRH-a for the treatment of advanced prostate cancer and suggest that the outcome of this treatment can be amplified by using PI3K-PKB inhibitors.
Department of Biological Regulation, The Weizmann Institute of Science, Rehovot, Israel.
Sarah
S
Kraus
Gal
G
Levy
Tamar
T
Hanoch
Zvi
Z
Naor
Rony
R
Seger
D017209:Apoptosis / Q000187:drug effects* / Q000502:physiology; D045744:Cell Line, Tumor; D002467:Cell Nucleus / Q000201:enzymology; D004789:Enzyme Activation / Q000187:drug effects; D007987:Gonadotropin-Releasing Hormone / Q000031:analogs & derivatives* / Q000494:pharmacology; D006801:Humans; D048031:JNK Mitogen-Activated Protein Kinases; D020935:MAP Kinase Signaling System / Q000187:drug effects* / Q000502:physiology; D008297:Male; D020928:Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D000081082:Phosphoinositide-3 Kinase Inhibitors; D010766:Phosphorylation / Q000187:drug effects; D011471:Prostatic Neoplasms / Q000188:drug therapy* / Q000201:enzymology* / Q000473:pathology; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D011518:Proto-Oncogene Proteins / Q000378:metabolism*; D051057:Proto-Oncogene Proteins c-akt; D048051:p38 Mitogen-Activated Protein Kinases
D007987:Gonadotropin-Releasing Hormone; D048031:JNK Mitogen-Activated Protein Kinases; D020928:Mitogen-Activated Protein Kinases; D019869:Phosphatidylinositol 3-Kinases; D000081082:Phosphoinositide-3 Kinase Inhibitors; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins; D051057:Proto-Oncogene Proteins c-akt; D048051:p38 Mitogen-Activated Protein Kinases