IDENTIFYING SIGNALING PATHWAYS PROSTATE TUMOR INHIBITION BY LHRH ANALOGS

本子项目是利用由NIH/NCRR资助的中心赠款提供的资源的众多研究子项目之一。子项目和研究者（PI）可能已经从另一个NIH来源获得了主要资金，因此可以在其他CRISP条目中表示。列出的机构是中心的，不一定是研究者的机构。在诊断时，超过一半的前列腺肿瘤已经侵袭和转移。早期发现前列腺癌并不是万无一失的治疗方法，因为肿瘤可以很快获得激素独立性。因此，我们必须了解肿瘤生长调控的生物学，以确定新的治疗靶点。促黄体生成素释放激素（LHRH）及其类似物直接抑制人类雄激素非依赖性前列腺细胞系的生长，包括DU-145。这些类似物发挥其抗增殖作用的机制尚不清楚。我们提出LHRH类似物通过表皮生长因子受体（EGFR）限制促生长信号。先前我们已经证明：1)DU-145细胞的生长和侵袭是通过EGFR介导的，2)EGFR信号细胞反应受pkc介导的EGFR直接磷酸化的负转调。尽管前列腺细胞中LHRH信号传导的数据仍不确定，但LHRH激动剂在乳腺肿瘤中刺激磷脂酶c （PLC）活性的方式与LHRH在垂体中的作用相似。我们的模型具有PLC活性产生二酰基甘油（DAG）和动员细胞内Ca2+激活蛋白激酶PKC)。这些发现使我们假设LHRH激动剂的抗增殖作用是通过EGFR的负衰减介导的，EGFR被PKC磷酸化而失活。我们建议在体外条件下利用强效LHRH类似物阐明LHRH信号通路抑制DU-145细胞增殖和侵袭的机制。我们这项研究的具体目的是确定LHRH类似物是否：1)在体外阻止前列腺肿瘤的生长和/或侵袭。2)影响细胞粘附谱。3)通过pkc介导的转调实现其作用。4)改变端粒酶表达谱。本课题的成功完成将阐明LHRH类似物发挥其抗增殖作用的细胞内机制。这将确定细胞内通路，其破坏有望限制前列腺癌的进展。

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. At the time of diagnosis, more than half of prostate tumors have invaded and metastasized. Early detection of prostate cancer is not a fail-safe cure since the tumors can quickly attain hormone-independence. Thus, it is imperative that we understand the biology of tumor growth regulation to define new therapeutic targets. Luteinizing hormone releasing hormone (LHRH) and its analogs directly inhibit growth of human, androgen independent prostate cell lines, including DU-145. The mechanism by which these analogs exert their antiproliferative effects is unknown. We propose that LHRH analogs limit the pro-growth signaling through the epidermal growth factor receptor (EGFR). Previously we have shown that: 1) DU-145 cells growth and invasion are mediated through the EGFR, and 2) EGFR-signaled cell responses are subject to PKC-mediated negative transmodulation by direct phosphorylatation of the EGFR. Although the data on LHRH signaling in prostate cells is still uncertain, LHRH agonists stimulate phospholipase-C (PLC) activity in mammary tumors in a similar manner as LHRH does in the pituitary gland. Our model has PLC activity generating diacylglycerol (DAG) and mobilizing intracellular Ca2+ to activate protein kinase C PKC). These findings lead us to hypothesize that the antiproliferative effects of LHRH agonists are mediated through negative attenuation of the EGFR, which is inactivated by phosphorylation by PKC. We propose to elucidate LHRH signaling mechanism for inhibition of cell proliferation and invasion in DU-145 cells under in vitro conditions utilizing potent LHRH analogs. Our specific aims for this study are to determine whether LHRH analogs: 1) Prevent prostate tumor growth and/or invasion in vitro. 2) Influence cell adhesion profile. 3) Achieve their effects via PKC-mediated transmodulation. 4) Alter the telomerase expression profile. The successful completeion of this project will elucidate the intracellular mechanism by which LHRH analogs exert their antiproliferative effect. This will identify intracellular pathways whose disruption hold promise for restricting prostate cancer progression.