Mechanisms of Metastasis in Experimental Prostate Cancer

描述(申请人提供)：小窝蛋白-1(Cav-1)是一种重要的结构/调节分子，参与分子运输和细胞信号转导的许多方面。Cav-1的活性依赖于蛋白质水平和细胞环境，然而对于Cav-1在恶性细胞中不适当表达的生物学后果的机制理解一直是难以捉摸的。我们以前已经证明Cav-1上调与转移性、雄激素不敏感的前列腺癌有关。在由这笔资金资助的研究中，我们确定了在前列腺癌进展过程中选择Cav-1过度表达的潜在机制。我们发现Cav-1结合并抑制PP1/PP2A丝氨酸/苏氨酸磷酸酶的活性，通过去磷酸化防止Akt失活，从而维持磷酸化Akt的水平及其致癌活性。最近，我们发现Cav-1过表达导致c-myc蛋白水平升高，上调和分泌VEGF、FGF2和TGF-β1。更重要的是，我们还发现Cav-1本身是由前列腺癌细胞特异性分泌的，并被前列腺癌细胞和内皮细胞(EC)摄取。总体而言，我们的数据表明，表达Cav-1的细胞可以通过分泌Cav-1和Cav-1刺激的生长因子(GF)/血管生成细胞因子(AC)来作为局部和潜在远处前列腺癌细胞和肿瘤相关EC的“饲养细胞”。为了支持这一概念，我们已经证明了实验诱导的转移在过表达Cav-1的宿主转基因小鼠中得到加强，而在宿主Cav-1-/-小鼠中被抑制。根据这一新信息，我们假设细胞内和分泌的Cav-1通过特定的促存活/促血管生成分子途径促进前列腺癌的进展。我们将通过特定的目标来验证这一假说：1)鉴定和表征新的Cav-1刺激前列腺癌的促生存/血管生成途径；2)鉴定Cav-1在前列腺癌细胞和EC中的摄取以及Cav-1对前列腺癌细胞和EC中的GF/AC活性的调节作用；3)识别和表征Cav-1在前列腺癌转移中系统作用的机制；以及4)在新型转基因小鼠前列腺重建模型中分析Cav-1在良性和恶性前列腺上皮细胞生长中的作用及其相关的血管生成。

DESCRIPTION (provided by applicant): Caveolin-1 (cav-1) is an important structural/regulatory molecule involved in many aspects of molecular transport and cell signaling. Cav-1 activities are dependent on protein levels and cell context, yet a mechanistic understanding of the biological consequences of inappropriate cav-1 expression in malignant cells has been elusive. We have shown previously that cav-1 up-regulation is associated with metastatic, androgen-insensitive prostate cancer. In studies funded by this grant we identified an underlying mechanism for the selection of cav-1 overexpression in prostate cancer cells during progression. We found that cav-1 binds to and inhibits the activities of PP1/PP2A serine/threonine phosphatases, preventing inactivation of Akt through dephosphorylation and thus sustaining levels of phospho-Akt and its oncogenic activities. Recently we demonstrated that cav-1 overexpression leads to increased levels of c-myc protein and up-regulation and secretion of VEGF, FGF2 and TGF-?1. Importantly, we have also discovered that cav-1 itself is specifically secreted by prostate cancer cells and taken up by prostate cancer cells and endothelial cells (EC). Overall our data suggest that cells expressing cav-1 can function as "feeder cells" for local and potentially distant prostate cancer cells and tumor-associated EC through secretion of cav-1 and cav-1 stimulated growth factors (GF)/angiogenic cytokines (AC). In support of this concept we have shown that experimentally induced metastasis is potentiated in host transgenic mice that overexpress cav-1 and is suppressed in host cav-1-/- mice. Informed by this new information we hypothesize that through specific prosurvival/proangiogenic molecular pathways, intracellular and secreted cav-1 promote prostate cancer progression. We will test this hypothesis through specific aims to: 1) identify and characterize novel cav-1 stimulated pro-survival/angiogenic pathways in prostate cancer; 2) characterize cav-1 uptake in prostate cancer cells and EC and the modulatory effects of cav-1 on GF/AC activities in prostate cancer cells and EC; 3) identify and characterize the mechanisms that underlie the systemic effects of cav-1 on prostate cancer metastasis; and 4) analyze the role of cav-1 in benign and malignant prostate epithelial cell growth and its associated angiogenesis in novel transgenic mouse prostate reconstitution models.