Rekasi Zoltan, Czompoly Tamas, Schally Andrew V, Boldizsar Ferenc, Varga Jozsef L, Zarandi Marta, Berki Timea, Horvath Reka A, Nemeth Peter
Department of Anatomy, University of Pécs, H-7624, Pécs, Hungary.
Proc Natl Acad Sci U S A. 2005 Mar 1;102(9):3435-40. doi: 10.1073/pnas.0410006102. Epub 2005 Feb 22.
Antagonists of growth hormone-releasing hormone (GHRH) exert antiproliferative effects directly on cancer cells, which are mediated by the tumoral GHRH receptors. However, the signal transduction pathways involved in antiproliferative effect of GHRH antagonists have not yet been elucidated. We used flow cytometry to investigate whether GHRH antagonist JV-1-38 can induce changes in the cytosolic free Ca2+ concentration leading to apoptosis in LNCaP human prostate cancer cells. JV-1-38 evoked prompt Ca2+ signal in a dose-dependent way (1-10 microM) and induced early stage of apoptosis in LNCaP human prostate cancer cells at a concentration effective in suppression of cell proliferation (10 microM) peaking after 3 h. Unexpectedly, agonist GHRH(1-29)NH2, which elevates cytosolic free Ca2+ concentration in pituitary somatotrophs at nanomolar concentrations, failed to induce Ca2+ signal or apoptosis even at a 10-fold higher concentration (100 microM). However, agonist GHRH(1-29)NH2 inhibited JV-1-38-induced Ca2+ signals in a dose-dependent way without affecting the antagonist-induced apoptosis. Peptides unrelated to GHRH did not induce Ca2+ signals in LNCaP human prostate cancer cells. EDTA (10 mM) or nifedipine (10 microM) significantly reduced the Ca2+ signal and early stage of apoptosis induced by JV-1-38, supporting the view that the increase in intracellular Ca2+ in response to JV-1-38 occurs primarily through extracellular Ca2+ entry through voltage-operated Ca2+ channels. In conclusion, GHRH antagonists activate tumoral GHRH receptors and are able to induce apoptosis in LNCaP human prostate cancer cells through a Ca2+-dependent pathway. Treatment with GHRH antagonists may offer a new approach to the therapy of prostate and other hormone-sensitive cancers.
生长激素释放激素（GHRH）拮抗剂可直接对癌细胞发挥抗增殖作用，这种作用由肿瘤GHRH受体介导。然而，GHRH拮抗剂抗增殖作用所涉及的信号转导途径尚未阐明。我们使用流式细胞术研究GHRH拮抗剂JV-1-38是否能诱导LNCaP人前列腺癌细胞胞质游离Ca2+浓度变化从而导致细胞凋亡。JV-1-38以剂量依赖方式（1 - 10微摩尔）引发快速的Ca2+信号，并在抑制细胞增殖有效的浓度（10微摩尔）下诱导LNCaP人前列腺癌细胞凋亡早期，3小时后达到峰值。出乎意料的是，激动剂GHRH(1 - 29)NH2在纳摩尔浓度下可提高垂体生长激素细胞胞质游离Ca2+浓度，但即使在高10倍的浓度（100微摩尔）下也未能诱导Ca2+信号或细胞凋亡。然而，激动剂GHRH(1 - 29)NH2以剂量依赖方式抑制JV-1-38诱导的Ca2+信号，而不影响拮抗剂诱导的细胞凋亡。与GHRH无关的肽未在LNCaP人前列腺癌细胞中诱导Ca2+信号。EDTA（10毫摩尔）或硝苯地平（10微摩尔）显著降低JV-1-38诱导的Ca2+信号和凋亡早期，支持以下观点：对JV-1-38的细胞内Ca2+增加主要通过电压门控Ca2+通道的细胞外Ca2+内流发生。总之，GHRH拮抗剂激活肿瘤GHRH受体，并能够通过Ca2+依赖途径诱导LNCaP人前列腺癌细胞凋亡。用GHRH拮抗剂治疗可能为前列腺癌和其他激素敏感性癌症的治疗提供一种新方法。
