Growth hormone-releasing hormone antagonist induces apoptosis of human endometrial cancer cells through PKCδ-mediated activation of p53/p21.
The growth hormone-releasing hormone (GHRH) antagonists have been shown to inhibit growth of human cancer cells, but the underlying molecular mechanisms and their actions have not been fully investigated. In this study, we first showed that GHRH-R splice variant 1 (SV1) was expressed in two human endometrial cancer cell lines, Ishikawa and ECC-1. By using MTT assay, immunoblotting for cleaved caspase-3 and TUNEL assays, we found that cell growth inhibition and apoptosis were induced in GHRH antagonist, JMR-132-treated cells by activating PKCδ and could be inhibited by treatment with PKC inhibitor, GF109203X. In addition, activation and protein expression of p53 as well as the expression of its downstream effector, p21, were increased by JMR-132 treatment. Moreover, JMR-132-induced p53 and p21 expression were diminished by treatment with PKC inhibitor. Knockdown of endogenous p53 and p21 by siRNAs abolished the JMR-132-induced cell growth inhibition and apoptosis. This study demonstrates a novel mechanism in which GHRH antagonist-induced cell growth inhibition and apoptosis through PKCδ-mediated activation of p53/p21 in human endometrial cancer cells. These findings may suggest the feasibility of GHRH antagonists as a therapeutic approach for human cancer.
Wu
Hsien-Ming
HM
Department of Obstetrics and Gynecology, University of British Columbia, Vancouver, British Columbia, Canada V6H3V5.
Schally
Andrew V
AV
Cheng
Jung-Chien
JC
Zarandi
Marta
M
Varga
Jozsef
J
Leung
Peter C K
PC
D017209:Apoptosis / Q000187:drug effects*; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects; D050759:Cyclin-Dependent Kinase Inhibitor p21 / Q000096:biosynthesis* / Q000235:genetics / Q000378:metabolism; D016889:Endometrial Neoplasms / Q000188:drug therapy* / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D005260:Female; D055785:Gene Knockdown Techniques; D013007:Growth Hormone-Releasing Hormone / Q000037:antagonists & inhibitors* / Q000378:metabolism; D006801:Humans; D007211:Indoles / Q000494:pharmacology; D008301:Maleimides / Q000494:pharmacology; D020033:Protein Isoforms; D051745:Protein Kinase C-delta / Q000037:antagonists & inhibitors / Q000096:biosynthesis* / Q000235:genetics / Q000378:metabolism; D012333:RNA, Messenger / Q000096:biosynthesis / Q000235:genetics; D034741:RNA, Small Interfering / Q000235:genetics; D017337:Sermorelin / Q000031:analogs & derivatives* / Q000494:pharmacology; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism*
C493956:CDKN1A protein, human; D050759:Cyclin-Dependent Kinase Inhibitor p21; C534070:GHRH(1-29)NH2, PhAcTyr(1)-Arg(2)-P(H)e(4-CL)(6)-Ala(8)-Tyr(Me)(10)-His(11)-Abu(15)-His(20)-Nle(27)-Arg(28)-HLCr(29)-; D007211:Indoles; D008301:Maleimides; D020033:Protein Isoforms; D012333:RNA, Messenger; D034741:RNA, Small Interfering; C495901:TP53 protein, human; D016159:Tumor Suppressor Protein p53; D017337:Sermorelin; D013007:Growth Hormone-Releasing Hormone; D051745:Protein Kinase C-delta; C070515:bisindolylmaleimide I