Prostate Carcinogensis and PKC Signaling

虽然PKC同工酶通常被认为是促进生长的蛋白质，但佛波酯作为最常见的PKC激活剂，会导致前列腺癌细胞的生长抑制或凋亡，这表明PKC同工酶可能在这些细胞的生长和程序性死亡的控制中发挥重要作用。这项建议的总体目标是评估PKC家族中单个成员作为这些反应的介体的作用，并研究参与PKC功能的信号通路。作为一种克服缺乏研究同工酶选择功能的药理学工具的方法，我们将用腺病毒将单个PKC同工酶导入前列腺癌细胞。利用PKCdelta腺病毒，我们初步证明这种新的PKC同工酶在雄激素敏感的LNCaP细胞中是促凋亡的，并在雄激素非依赖性细胞中诱导G2/M期停滞。在特定的目标1中，我们将评估单个PKC同工酶在前列腺癌细胞生长和程序性细胞死亡中的作用。由于单个PKC同工酶可能具有重叠或不同的作用，本研究的一个主要目的是确定前列腺癌细胞中存在的PKC家族的其他成员(PKCalpha、PKCepsilon、PKCnu、PKCDelta)是否调节细胞生长或凋亡。我们还将表征细胞周期调节因子表达的变化，这些变化可能伴随着PKCDelta介导的G2/M停滞。在特定的目标2中，我们将描述参与PKC介导的前列腺癌细胞凋亡的信号通路，重点是通过P13K/Akt通路的MAPK级联和生存信号。这是相关的，因为许多前列腺癌存在PTEN突变，PTEN是P13K途径的负调控因子。在特定的目标3中，我们将评估在前列腺癌细胞中过表达PKC同工酶是否会降低其在裸鼠体内的致瘤潜能。在特定的目标4中，我们建议使用一种新的Cre/loxP重组系统来产生在前列腺中过度表达PKC同工酶或其主要阴性形式的转基因小鼠，该重组系统允许不依赖于雄激素水平的转基因成分的表达。该模型可用于评估去势和雄激素替代后PKC同工酶的表达如何分别调节前列腺的细胞凋亡和增殖。这些研究的结果将有助于确定PKC同工酶是否为前列腺癌治疗的潜在靶点。我们的研究将对前列腺癌发生的分子事件产生新的见解。

Although PKC isozymes have been generally viewed as growth- promoting proteins, phorbol esters, the most common PKC activators, cause growth inhibition or apoptosis in prostate cancer cells; suggesting that PKC isozymes may be important players in the control of growth and programmed cell death in these cells. The overall objective of this proposal is the evaluation of the roles of individual members of the PKC family as mediators of these responses, and the study of the signaling pathways involved in PKC function in prostate cancer cells. As an approach to overcome the lack of selectivity of pharmacological tools to study isozyme-selective function, we will deliver individual PKC isozymes into prostate cancer cells using adenoviruses. Using a PKCdelta adenovirus, we show strong preliminary evidence that this novel PKC isozyme is pro-apoptotic in androgen-sensitive LNCaP cells and induces G2/M arrest in androgen-independent cells. In Specific Aim 1 we will evaluate the role of individual PKC isozymes in cell growth and programmed cell death in prostate cancer cells. Since individual PKC isozymes may have either overlapping or distinct roles, a major goal of this proposal is to determine whether other members of the PKC family present in prostate cancer cells (PKCalpha, PKCepsilon, PKCnu, PKCdelta ) regulate cell growth or apoptosis. We will also characterize changes in the expression of cell cycle regulators that may accompany the G2/M arrest mediated by PKCdelta. In Specific Aim 2 we will characterize the signaling pathways involved in PKC-mediated apoptosis in prostate cancer cells, focusing on the MAPK cascades and survival signaling through the P13K/Akt pathway. This is relevant since many prostate tumors present mutations in PTEN, a negative regulator of the P13K pathway. In Specific Aim 3 we will evaluate whether overexpression of PKC isozymes in prostate cancer cells reduce their tumorigenic potential in athymic nude mice. In Specific Aim 4 we propose the generation of transgenic mice overexpressing PKC isozymes or their dominant negative forms in the prostate, using a novel Cre/loxP recombination system that allows constitutive expression of the transgene independent of the androgen levels. This model will allow for the evaluation of how expression of PKC isozymes regulate apoptosis and proliferation in the prostate after castration and androgen replacement, respectively. The outcome of these studies will be useful to determine whether PKC isozymes serve as potential targets for the therapeutics of prostate cancer. Our research will yield new insights into the molecular events of prostate carcinogenesis.