Vav3 Oncogene in Prostate Cancer

描述（由申请人提供）：雄激素受体（AR）活性升高和PI3K-Akt信号通路参与前列腺癌的发生和进展。然而，前列腺癌中这两个关键信号通路升高的机制尚未完全阐明。我们发现Vav3癌基因是Rac/Rho GTPases的一种quanine nucleotide exchange factor (GEF)，在雄激素非依赖性前列腺癌细胞和32%的人类前列腺癌中过度表达。进一步分析表明，Vav3刺激前列腺癌细胞生长，通过DH结构域与AR相互作用，并作为辅激活剂激活AR。Vav3作为信号换能器，也上调PI3K-Akt信号，导致AR激活。此外，Vav3在前列腺上皮中的靶向过表达可在2个月大的年轻成年小鼠中诱导前列腺上皮内瘤变（mPIN）。我们假设Vav3的过表达不适当地激活AR并促进前列腺癌的发展，进一步升高的Vav3活性刺激前列腺癌进展到雄激素非依赖性状态。提出了三个具体目标来检验这一假设。特异性目的1：在小鼠前列腺癌模型中，确定Vav3过表达在前列腺癌发生发展到雄激素不依赖状态中的作用。在转基因小鼠中，我们将研究Vav3的强迫过表达是否会刺激前列腺肿瘤中雄激素非依赖性的生长，以及Vav3在前列腺上皮中的靶向过表达是否会诱导前列腺癌的发展并刺激其向雄激素非依赖性状态发展。特异性目的2：阐明Vav3在前列腺癌中的信号通路。我们将通过常规的Vav3- rho - pi3k - akt通路，在前列腺癌细胞中确定Vav3共激活AR和Vav3信号传导的潜在分子机制。我们还将通过GST-pull - down和基于质谱的蛋白质组学分析，构建连接细胞外刺激和AR信号轴的vav3介导的完整信号通路以及细胞生长和存活途径。特异性目的3：将Vav3过表达与人类前列腺癌的Gleason评分、病理分期、PI3K-Akt信号传导和雄激素独立状态联系起来。这些从临床前小鼠模型到人类前列腺癌标本的临床研究一旦完成，将进一步加深我们对前列腺癌发展及其雄激素非依赖性生长机制的认识，并为合理开发前列腺癌新疗法提供靶点和动物模型。

DESCRIPTION (provided by applicant): Elevated androgen receptor (AR) activity and PI3K-Akt signaling are involved in prostate cancer development and progression. The mechanisms responsible for elevation of these two key signaling pathways in prostate cancer, however, have not fully elucidated. We found that Vav3 oncogene, a quanine nucleotide exchange factor (GEF) for Rac/Rho GTPases, is overexpressed in androgen-independent prostate cancer cells and in 32% of human prostate cancer. Further analysis revealed that Vav3 stimulates growth of prostate cancer cells, interacts with AR via the DH domain, and activates AR as a coactivator. Vav3, as a signal transducer, also upregulates PI3K-Akt signaling leading to AR activation. Furthermore, targeted overexpression of Vav3 in the prostate epithelium induces prostatic intraepithelial neoplasia (mPIN) in young adult mice as early as two months old. We hypothesize that overexpression of Vav3 inappropriately activates AR and promotes prostate cancer development and that further elevated Vav3 activity stimulates prostate cancer progression to the androgen-independent status. Three Specific Aims are proposed to test the hypothesis. Specific Aim 1: To determine the role of Vav3 overexpression in prostate cancer development and progression to the androgen-independent status in mouse prostate cancer models. We will investigate whether forced overexpression of Vav3 stimulates androgen-independent growth in prostate tumor and whether targeted overexpression of Vav3 in the prostate epithelium induces prostate cancer development and stimulates progression to the androgen-independent status in transgenic mice. Specific Aim 2: To elucidate the signaling pathways of Vav3 in prostate cancer. We will determine the underlying molecular mechanisms of Vav3 coactivation for AR and Vav3 signaling via the conventional Vav3-Rho-PI3K-Akt pathway leading AR activation in prostate cancer cells. We will also build up the whole Vav3-mediated signaling pathways that connect extracellular stimuli to AR signaling axis as well as cell growth and survival pathway by GST-pull down and Mass Spectrometry-based proteomics analysis. Specific Aim 3: To associate Vav3 overexpression with Gleason score, pathologic stage, PI3K-Akt signaling, and androgen-independent status in human prostate cancers. Once completed, these studies from the preclinical mouse model to the clinical study in human prostate cancer specimens will further our understanding of the mechanisms of prostate cancer development and its androgen-independent growth and provide targets and animal models for the rational development of novel therapies against prostate cancer.