Prostate carcinogenesis and PKC signaling

描述(申请人提供)：前列腺癌的发生和发展涉及一系列的遗传和表观遗传变化，导致增殖和生存信号的放松调控。在人类前列腺癌(以及其他几种上皮性癌症)中，一个显著的变化是PKCE的显著过度表达，PKCE是一种存活和有丝分裂的丝氨酸-苏氨酸激酶，是佛波酯肿瘤促进剂的受体。到目前为止，还不知道PKCE是否与前列腺癌的病因学有关。有待解决的问题是，PKCE的过度表达与前列腺癌的发生和发展是否存在因果关系。我们建立了使用前盆(PB)启动子将PKC同工酶靶向前列腺上皮的小鼠模型。有趣的是，PB-PKCE转基因小鼠出现了前列腺增生和上皮内肿瘤(PIN)病变，而在我们建立的类似的PKCA或PKCd过表达模型中没有观察到明显的表型。值得注意的是，当我们将PB-PKCE小鼠与杂合子Pten小鼠(也会发展为癌前病变)杂交时，得到的复合PB-PKCE Pten小鼠患上了侵袭性前列腺癌。前列腺病变表现为活性Akt、mTOR、S6、STAT3和NF-kB水平升高。因此，PKCE的过度表达是前列腺癌发生的一个潜在的致病因素，并与明确的致癌基因改变协同作用。在具体目标1中，目标是使用PKCE缺失的前列腺癌细胞和特定的PKCE抑制物(EV1-2)来确定PKCE是否有助于前列腺癌细胞的肿瘤发生和扩散。在特定的目标2中，我们建议研究PKCE和PI3K/Akt轴在前列腺癌发生中的相互作用。我们将建立前列腺特异性PKCE过度表达/Akt缺失的小鼠模型，以确定Akt是否与PB-PKCE过度表达驱动的前列腺病变的形成有关。我们还将测试这一假设，即基因或药物靶向的PKCE可以逆转Pten缺乏诱导的小鼠的恶性表型。在特定的目标3中，我们将探讨核因子-kB在前列腺癌的PKCE信号转导中的潜在作用。核因子-kB的过度激活是前列腺癌的一个标志，本申请中提供的初步数据显示，PKCE和核因子-kB通路之间存在明确的功能关系。具体地说，我们将a)检测PKCE的过表达是否足以促进正常前列腺上皮细胞中NF-kB的激活，并与Pten Lost合作激活NF-kB，b)确定PKCE是否参与前列腺癌中观察到的NF-kB的结构性激活，c)表征PKCE参与调控NF-kB调节基因的作用，以及d)剖析PKCE控制NF-kB激活的机制。因此，我们的研究将确定PKCE在前列腺癌病因中的潜在作用，并确定其作为治疗靶点的潜在意义。

DESCRIPTION (provided by applicant): The genesis and progression of prostate cancer involves a series of both genetic and epigenetic changes that result in deregulation of proliferation and survival signals. One notable alteration in human prostate cancer (as well as in several other epithelial cancers) is the marked overexpression of PKCe, a survival and mitogenic Ser-Thr kinase that is a receptor for the phorbol ester tumor promoters. To date it is not known whether PKCe is implicated in the etiology of prostate cancer. The question that remains to be addressed is whether there is a causal relationship between PKCe overexpression and prostate cancer initiation and progression. We generated mouse models to target PKC isozymes to the prostate epithelium using a probasin (PB) promoter. Interestingly, PB-PKCe transgenic mice developed prostatic hyperplasia and intraepithelial neoplastic (PIN) lesions, whereas no obvious phenotype was observed in similar models that we developed for PKCa or PKCd overexpression. Remarkably, when we crossed PB- PKCe mice with heterozygous Pten mice (which also develop preneoplastic lesions), the resulting compound PB-PKCe Pten mice developed invasive prostatic adenocarcinoma. Prostate lesions present elevated levels of active Akt, mTOR, S6, Stat3, and NF-kB. Thus, PKCe overexpression is a potential causative factor for prostate cancer development and cooperates with defined oncogenic alterations. In Specific Aim 1 the goal is to determine whether PKCe contributes to prostate cancer cell tumorigenicity and dissemination, using both PKCe-deficient prostate cancer cells and a specific PKCe inhibitor (eV1-2). In Specific Aim 2 we propose to study the mutual requirement for PKCe and the PI3K/Akt axis in prostate tumorigenesis. We will generate prostate-specific PKCe overexpressing/Akt-null mouse models to determine whether Akt is implicated in the formation of prostate lesions driven by PB-PKCe overexpression. We will also test the hypothesis that genetic or pharmacological targeting of PKCe can reverse the malignant phenotype induced by Pten deficiency in mice. In Specific Aim 3 we will address a potential involvement of NF-kB in PKCe signaling in prostate cancer. NF-kB hyperactivation is a hallmark of prostate cancer, and preliminary data presented in this application show a clear functional relationship between PKCe and NF-kB pathways. Specifically, in this aim we will a) examine if overexpression of PKCe is sufficient to promote NF-kB activation in normal prostate epithelial cells and cooperates with Pten loss to activate NF-kB, b) determine if PKCe is implicated in the constitutive activation of NF-kB observed in prostate cancer, c) characterize the involvement of PKCe in the control of NF-kB-regulated genes, and d) dissect of the mechanisms by which PKCe controls NF-kB activation. Our studies will therefore establish the potential role of PKCe in the etiology of prostate cancer and determine its potential significance as a therapeutic target.