Neutral Endopeptidase inactivation in advanced prostate

描述（申请人提供）：大量研究表明神经肽生长因子参与前列腺癌的发生和进展。中性内肽酶24.11 （NEP， CALLA, CD10）是一种细胞表面肽酶，可使多种与前列腺癌相关的神经肽失活，包括bombesin，内皮素-1 （ET-1）和神经紧张素。我们首先报道了NEP表达在原发性和转移性前列腺癌的一个亚群中降低，NEP表达部分受雄激素调节，并随着雄激素的减少而降低。在过去的研究中，我们描述了NEP基因的雄激素调控，证明使用外源性重组NEP或细胞表面过表达NEP替代NEP可抑制前列腺癌细胞生长、细胞迁移和致瘤性，并确定了NEP发挥肿瘤抑制作用的至少三种不同机制，包括1)NEP神经肽底物的催化失活；2)间接与磷脂酰肌醇3-激酶（P13-K）蛋白相关并抑制P13-K与focal adhesion kinase （FAK）的相互作用；3)直接与PTEN肿瘤抑制基因蛋白相关并稳定PTEN。这些数据表明，NEP蛋白在正常情况下调节前列腺上皮细胞的生长，NEP表达的缺失可能导致前列腺癌的生长和进展。在这项更新申请中，我们建议继续确定NEP在前列腺癌细胞中的抗肿瘤作用机制，更彻底地破译NEP的表达调控，并使用NEP与特异性靶向前列腺癌细胞的单克隆抗体相结合的新型融合蛋白来研究NEP作为治疗方法的潜力。这些拟开展的研究将为以NEP为原型的细胞表面肽酶的多种功能提供重要的新认识，并更清晰地界定NEP在前列腺癌发生发展中的作用。

DESCRIPTION (provided by applicant): Numerous studies indicate that neuropeptide growth factors contribute to the development and progression of prostate cancer. Neutral endopeptidase 24.11 (NEP, CALLA, CD10) is a cell-surface peptidase that inactivates a variety of neuropeptides implicated in prostate cancer, including bombesin, endothelin-1 (ET-1) and neurotensin. We first reported that NEP expression is decreased in a subset of primary and metastatic prostate cancers, and that NEP expression is in part regulated by androgen and decreases with androgen-withdrawal. In our research over this past grant period, we have characterized the androgen regulation of the NEP gene, demonstrated that replacement of NEP using either exogenous recombinant NEP or overexpression of cell-surface NEP inhibits prostate cancer cell growth, cell migration and tumorigenicity, and have identified at least three distinct mechanisms by which NEP exerts a tumor suppressive effect, including 1) catalytic inactivation of NEP's neuropeptide substrates, 2) indirectly associating with phosphatidylinositol 3-kinase (P13-K) protein and inhibiting the interaction of P13-K with focal adhesion kinase (FAK), and 3) directly associating with and stabilizing the PTEN tumor suppressor gene protein. These data suggest that the NEP protein normally functions to regulate prostate epithelial cell growth, and that loss of NEP expression may contribute to prostate cancer growth and progression. In this renewal application, we propose to continue to define the mechanisms of NEP anti-tumor effects in prostate cancer cells, to more thoroughly decipher the regulation of NEP expression, and to study the potential of NEP as therapy using a novel fusion protein in which NEP is linked to a monoclonal antibody which specifically targets prostate cancer cells. These proposed studies should provide significant new knowledge on the multiple functions of cell-surface peptidases with NEP as a prototype, and more clearly define the involvement of NEP in the development and progression of prostate cancer.