Regulation of Par-4 Secretion in Normal Cells for Paracrine Action in Tumor Cells

描述（由申请人提供）：肺癌是美国男性和女性癌症死亡的主要原因。导致Ras癌基因激活和p53肿瘤抑制基因失活的突变是肺癌中两种最常见的改变。由于化疗和放疗的肿瘤生长抑制作用通常需要野生型p53功能，具有p53突变或缺失的肺肿瘤对治疗产生抗性，导致患者最终死亡。此外，致癌Ras激活和p53失活导致NF-kB活性升高，这有助于细胞存活和治疗抗性。肿瘤生长受正常细胞和癌细胞之间相互作用的复杂网络的调节。除了局部相互作用外，肿瘤生长可能受到宿主全身产生的生长促进和生长抑制因子的影响。因此，癌症治疗剂可以适当地用于调节全身环境，以便直接靶向异常生长。了解与正常细胞系统性分泌促凋亡蛋白及其对肿瘤上皮细胞的影响相关的机制是此类研究的关键方面。肺癌患者全身的大多数细胞是正常的，并且具有野生型p53状态。该提案将探讨正常细胞中p53的激活是否会引发p53缺陷型肺肿瘤中的旁分泌细胞死亡。由于p53激活仅部分抑制NF-kB活性，我们的初步研究在正常细胞中使用p53的共平行激活和NF-kB的抑制来鉴定可在p53缺陷型肺癌细胞中引起旁分泌凋亡效应的分泌蛋白。基于我们的研究结果，我们假设p53调节促凋亡肿瘤抑制蛋白Par-4从正常细胞中的旁分泌效应在癌细胞中的分泌，并且Par-4蛋白的最大诱导由p53激活和NF-kB抑制从正常细胞中应有效地诱导p53缺陷的小鼠肺肿瘤中的凋亡。拟议的研究将通过追求两个具体目标来探索这一新的调查领域的可行性。(Aim 1）确定正常细胞中p53激活诱导肿瘤细胞凋亡的机制。我们将研究Par-4分泌的动力学和机制，诱导p53在不同的正常细胞类型，导致p53缺陷的肺癌细胞凋亡。(Aim 2）确定Par-4分泌对p53缺陷型肺肿瘤的旁分泌作用，所述Par-4分泌由正常细胞中的p53活化诱导。在同时激活p53和抑制NF-κ B活性后，我们将在K-rasLSL-G12 D、p53 Fl/Fl小鼠中测试Par-4蛋白的系统性升高的动力学及其对肺肿瘤的细胞凋亡和消退的影响。此外，将进行机制研究，以更深入地了解Par-4在旁分泌作用于小鼠这些肿瘤中的功能作用。总之，这些研究将揭示正常细胞中p53激活的旁分泌效应对p53缺陷型肺癌细胞凋亡和消退的可行性和机制。由于p53在不同的癌症中发生突变，这项研究的发现将具有广泛的翻译意义。

DESCRIPTION (provided by applicant): Lung cancer is a leading cause of cancer death in men and women in the United States. Mutations leading to activation of the Ras oncogenes and inactivation of the p53 tumor suppressor gene are two of the most common alterations in lung cancer. As the tumor growth inhibitory action of chemotherapy and radiation therapy generally requires wild-type p53 function, lung tumors with p53 mutations or deletions develop resistance to therapy resulting in ultimate death of the patients. Moreover, oncogenic Ras activation and p53 inactivation results in elevated NF-kB activity that contributes to cell survival and therapeutic resistance. Tumor growth is regulated by a complex network of interactions between normal cells and cancer cells. In addition to local interactions, tumor growth may be influenced by growth-promoting and growth-inhibiting factors produced systemically by the host. Accordingly, cancer therapeutics can be aptly utilized to regulate the systemic environment in order to directly target aberrant growth. Understanding the mechanisms associated with systemic secretion of pro-apoptotic proteins by normal cells and their effect on tumor epithelial cells is a critical facet of such investigations. A majority of the cells throughout the body of lug cancer patients are normal and have wild type p53 status. This proposal will explore whether p53 activation in normal cells triggers paracrine cell death in p53-deficient lung tumors. As p53 activation only partially inhibits NF-kB activity, our Preliminary Studies used co-parallel activation of p53 and inhibition of NF-kB in normal cells to identify secreted protein(s) that can cause a paracrine apoptotic effect in p53-deficient lung cancer cells. Based on our findings, we hypothesize that p53 regulates the secretion of the pro-apoptotic tumor suppressor protein Par-4 from normal cells for paracrine effect in cancer cells, and that maximum induction of Par-4 protein by p53 activation and NF-kB inhibition from normal cells should effectively induce apoptosis in p53-deficient lung tumors in mice. The proposed study will explore the feasibility of this novel area of investigation by pursuing two Specific Aims. (Aim 1) Determine the mechanism by which p53 activation in normal cells induces tumor cell apoptosis. We will study the kinetics and mechanism of Par-4 secretion induced by p53 in diverse normal cell types leading to apoptosis of p53-deficient lung cancer cells. (Aim 2) Determine the paracrine effect of Par-4 secretion, which is induced by p53 activation in normal cells, on p53-deficient lung tumors. After concomitant activation of p53 and inhibition of NF-kB activity, we will test the kinetics of systemic elevation of Par-4 protein and its effect on apoptosis and regression of lung tumors in K-rasLSL-G12D,p53Fl/Fl mice. Moreover, mechanistic studies will be undertaken to gain deeper insights into the functional role of Par-4 in the paracrine action on these tumors in mice. Collectively, these studies will uncover the feasibility and mechanism of the paracrine effects of p53 activation in normal cells for apoptosis and regression of p53-deficient lung cancer. As p53 is mutated in diverse cancers, the findings of this study will have broad translational implications.