ROLE OF CYP24 IN NON-SMALL CELL LUNG CANCER

描述（由申请人提供）：我们的研究已经鉴定出非小细胞肺癌（NSCLC）中一种新型生长调节途径，该途径涉及CYP 24，CYP 24是降解内源性抗增殖剂1，25-二羟基维生素D3（1，25（OH）2D 3）的酶。组织中1，25（OH）2D 3的水平和生物活性通常通过维持CYP 27 B1合成速率和CYP 24降解速率之间的精确平衡来控制。我们发现这种平衡在NSCLC中失调。具体而言，我们确定CYP 24在人NSCLC细胞和大多数人肺肿瘤中过表达。我们假设CYP 24过表达通过允许肿瘤细胞逃避局部产生的1，25（OH）2D 3的抗增殖作用而促进肺癌生长。因此，我们发现CYP 24抑制揭示了CYP 27 B1 + CYP 24 + NSCLC细胞的1，25（OH）2D 3产生，并允许激素以足以抑制生长的量蓄积。我们的数据进一步表明，Ets-1和C/EBP蛋白增加CYP 24在NSCLC细胞中的转录。这些转录因子的激活先前已与肺癌中的致癌信号传导相关联。本研究的目的是探讨CYP 24异常表达对肺癌生长的影响以及CYP 24过表达在肺癌中的作用机制。在目的1中，我们将测试CYP 24过表达通过降低1，25（OH）2D 3的稳定性和抗肿瘤活性促进NSCLC生长的预测。我们将量化调控CYP 24表达对NSCLC细胞系和肿瘤异种移植模型中1，25（OH）2D 3催化剂和抗肿瘤活性的影响。我们还将使用一种创新的离体测定法来确定人肺肿瘤中CYP 24表达与1，25（OH）2D 3催化剂之间的关联。在目标2中，我们将测试CYP 24过表达拮抗维生素D3在NSCLC中的自分泌生长调节的预测。我们将利用一种新型CYP 24抑制剂来证明CYP 24对CYP 27 B1 + CYP 24 + NSCLC细胞合成1，25（OH）2D 3的影响，并证明局部产生的激素引发生物学反应的能力。我们还将检测CYP 24过表达和CYP 27 B1缺失是否与肺癌表型独立相关。在目标3中，我们将检验癌基因激活的Ets-1和C/EBP转录因子调节NSCLC中CYP 24表达的预测。将确定Ets-1和C/EBP调节对CYP 24转录和活性的影响。将通过染色质免疫沉淀法评价Ets和C/EBP蛋白向内源性CYP 24启动子的募集（作为ras激活的函数）。拟定的研究将确定NSCLC发病机制的新机制，其中癌基因激活的转录因子通过增加分解代谢内源性生长抑制因子（1，25（OH）2D 3）的蛋白质（CYP 24）的表达促进肿瘤发生。一旦证实，这种模式的治疗意义是抑制CYP 24的药物可用于恢复NSCLC中维生素D3介导的生长控制。公共卫生相关性：我们最近发现，肺癌细胞产生一种名为CYP 24的蛋白质，这种蛋白质会破坏天然的抗肿瘤剂维生素D。我们的研究旨在确定CYP 24在促进肺癌生长中的确切作用。最终，这将有助于我们开发阻断CYP 24的优化策略，从而增加维生素D在肺癌预防和治疗中的活性。

DESCRIPTION (provided by applicant): Our studies have led to the identification of a novel growth regulatory pathway in non-small cell lung cancer (NSCLC) that involves CYP24, the enzyme that degrades the endogenous anti-proliferative agent, 1,25- dihydroxyvitamin D3 (1,25(OH)2D3). The level and biological activity of 1,25(OH)2D3 in tissues is normally controlled by maintaining a precise balance between the rates of its synthesis by CYP27B1 and degradation by CYP24. We discovered that this balance is dysregulated in NSCLC. Specifically, we determined that CYP24 is overexpressed in human NSCLC cells and a majority of human lung tumors. We hypothesize that CYP24 overexpression facilitates lung cancer growth by allowing neoplastic cells to escape the anti- proliferative effects of locally-produced 1,25(OH)2D3. Accordingly, we found that CYP24 inhibition uncovers 1,25(OH)2D3 production by CYP27B1+CYP24+ NSCLC cells and allows for accumulation of hormone in amounts sufficient for growth suppression. Our data further indicate that Ets-1 and C/EBP proteins increase CYP24 transcription in NSCLC cells. Activation of these transcription factors has previously been linked to oncogenic signaling in lung cancer. Our objective is to establish the effect of aberrant CYP24 expression on lung cancer growth and the mechanism for CYP24 overexpression in lung cancer. In Aim 1 we will test the prediction that CYP24 overexpression facilitates NSCLC growth by decreasing the stability and anti- tumor activity of 1,25(OH)2D3. We will quantify the effect of modulating CYP24 expression on 1,25(OH)2D3 catabolism and anti-tumor activity in NSCLC cell lines and tumor xenograft models. We will also use an innovative ex vivo assay to determine the association between CYP24 expression and 1,25(OH)2D3 catabolism in human lung tumors. In Aim 2 we will test the prediction that CYP24 overexpression antagonizes autocrine growth regulation by vitamin D3 in NSCLC. We will utilize a novel CYP24 inhibitor to demonstrate the effect of CYP24 on 1,25(OH)2D3 synthesis by CYP27B1+CYP24+ NSCLC cells and demonstrate the ability of locally- produced hormone to elicit biological responses. We will also test whether CYP24 overexpression and CYP27B1 loss are independently correlated with the lung cancer phenotype. In Aim 3 we will test the prediction that oncogene-activated Ets-1 and C/EBP transcription factors regulate CYP24 expression in NSCLC. The effect of Ets-1 and C/EBP modulation on CYP24 transcription and activity will be established. Recruitment of Ets and C/EBP proteins to the endogenous CYP24 promoter (as a function of ras activation) will be evaluated by chromatin immunoprecipitation. The proposed studies will identify a novel mechanism for the pathogenesis of NSCLC in which oncogene-activated transcription factors facilitate tumorigenesis by increasing the expression of a protein (CYP24) that catabolizes an endogenous growth suppressor (1,25(OH)2D3). The therapeutic implication of this paradigm, once confirmed, is that agents that inhibit CYP24 can be used to restore vitamin D3-mediated growth control in NSCLC. PUBLIC HEALTH RELEVANCE: We recently discovered that lung cancer cells make a protein called CYP24 that destroys the natural anti-tumor agent, vitamin D. Our studies are designed to determine the precise role of CYP24 in promoting lung cancer growth. Ultimately, this will help us to develop optimized strategies to block CYP24 and thereby increase the activity of vitamin D in lung cancer prevention and treatment.