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最常见的两种改变。由于化疗和放疗的肿瘤生长抑制作用通常需要p53的野生型功能，p53突变或缺失的肺肿瘤对治疗产生耐药性，最终导致患者死亡。此外，致癌的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耐药性。肿瘤的生长受到正常细胞和癌细胞之间复杂的相互作用网络的调控。除了局部相互作用外，肿瘤生长还可能受到宿主全身产生的促生长因子和抑制生长因子的影响。因此，可以适当地利用癌症治疗来调节系统环境，以直接针对异常生长。了解正常细胞分泌促凋亡蛋白的相关机制及其对肿瘤上皮细胞的影响是此类研究的关键方面。肺癌患者全身大部分细胞是正常的，具有野生型p53状态。本研究将探讨p53在正常细胞中的激活是否会引发p53缺陷肺肿瘤的旁分泌细胞死亡。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的并行激活和NF-kB的抑制来鉴定可在p53缺乏的肺癌细胞中引起旁分泌凋亡效应的分泌蛋白。根据我们的研究结果，我们假设p53调节正常细胞分泌促凋亡的肿瘤抑制蛋白Par-4，在癌细胞中发挥旁分泌作用，并且通过p53激活和NF-kB抑制正常细胞最大限度地诱导Par-4蛋白，可以有效地诱导p53缺失小鼠肺肿瘤的凋亡。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。（目的1）确定正常细胞中p53激活诱导肿瘤细胞凋亡的机制。我们将研究不同正常细胞类型中p53诱导的Par-4分泌导致p53缺失肺癌细胞凋亡的动力学和机制。（目的2）确定正常细胞中p53激活诱导的Par-4分泌对p53缺陷肺肿瘤的旁分泌作用。在同时激活p53和抑制NF-kB活性后，我们将在K-rasLSL-G12D、p53Fl/Fl小鼠中测试Par-4蛋白的全身升高动力学及其对肺肿瘤凋亡和消退的影响。此外，将进行机制研究，以更深入地了解par4在小鼠肿瘤旁分泌作用中的功能作用。综上所述，这些研究将揭示p53在正常细胞中激活对p53缺陷型肺癌的凋亡和消退的旁分泌作用的可行性和机制。由于p53在多种癌症中发生突变，因此本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.