CYP1B1: A Molecular Target for Chemoprevention of Lung Adenocarcinoma

描述（申请人提供）：肺癌仍然是美国男性和女性癌症死亡的主要原因，近几十年来女性发病率增加了6倍。此外，大多数非吸烟者的肺癌病例发生在女性身上。几项流行病学研究的结果表明，除了烟草烟雾，雌激素也可能导致肺癌的风险和进展。虽然受体介导的信号通路在癌变过程中已经得到了很好的研究，但雌激素代谢酶在肿瘤形成和发展中的潜在作用却很少得到关注。本研究的目的是使用新的动物模型来评估雌激素代谢改变对肺癌发展的影响。该实验的基本原理是由初步数据提供的，该数据首次表明雌激素在小鼠肺组织内代谢。小鼠暴露于烟草烟雾中会诱导细胞色素P450 1B1 （CYP1B1）的表达，CYP1B1是一种将雌激素和烟草烟雾成分转化为致癌衍生物的酶。与邻近正常组织相比，CYP1B1在肺肿瘤中的表达升高，4-羟基雌激素（4-OHE）的水平在烟雾暴露后在小鼠肺中显著升高，4-羟基雌激素是一种主要由CYP1B1产生的遗传毒性雌激素代谢物。该研究的假设是，抑制CYP1B1将导致4-OHE的产生减少，并提供预防肺癌的保护；因此代表了化学预防这种疾病的一个新的分子靶点。该假设将通过本小组近期建立的具有临床意义的LSL-KrasG12D小鼠肺肿瘤发生模型、CYP1B1-/-小鼠和新型双转基因LSL-KrasG12D /CYP1B1-/-小鼠进行验证。CYP1B1缺失对肺内雌激素代谢的影响将在Specific Aim 1中通过比较雌性CYP1B1-/-和CYP1B1+/+小鼠肺组织中雌激素代谢相关基因的表达和雌激素代谢物谱来研究。在Aim 2中，将使用LSL-KrasG12D小鼠模型研究抑制CYP1B1作为肺癌预防策略的可行性。CYP1B1的抑制将通过基因缺失或给药2,3',4,5'-四甲基二苯乙烯（TMS）来实现，TMS是白藜芦醇的合成类似物，是CYP1B1的选择性抑制剂。CYP1B1抑制对肿瘤总负荷（MRI测定的肿瘤体积）和肿瘤分期变化的影响将被确定。从拟议的研究中获得的数据有望揭示CYP1B1作为化学预防的分子靶点的潜在效用，并为雌激素代谢对肺癌发展的贡献提供新的见解。

DESCRIPTION (provided by applicant): Lung cancer remains the leading cause of cancer death among men and women in the U.S., with rates in women increasing 6-fold in recent decades. Furthermore, the majority of lung cancer cases in nonsmokers occur in women. Results from several epidemiological studies suggest that, in addition to tobacco smoke, estrogen may contribute to lung cancer risk and progression. Although receptor-mediated signaling pathways have been well studied in carcinogenesis, much less attention has been given to the potential contribution of estrogen metabolizing enzymes to tumor formation and progression. The goal of the present study is to use novel animal models to assess the impact of alterations in estrogen metabolism on lung cancer development. Rationale for this experimentation is provided by preliminary data that indicate for the first time that estrogen is metabolized within murine lung tissue. Exposure of mice to tobacco smoke induces the expression of cytochrome P450 1B1 (CYP1B1), an enzyme that converts both estrogen and constituents of tobacco smoke to carcinogenic derivatives. CYP1B1 expression is elevated in lung tumors vs. adjacent normal tissue, and levels of 4-hydroxyestrogen (4-OHE), a genotoxic estrogen metabolite produced primarily by CYP1B1, are elevated significantly within the murine lung following smoke exposure. The hypothesis of the proposed study is that inhibition of CYP1B1 will lead to decreased production of 4-OHE and provide protection against lung cancer; thus representing a novel molecular target for the chemoprevention of this disease. This hypothesis will be tested using the clinically relevant LSL-KrasG12D mouse model of lung tumorigenesis, CYP1B1-/- mice and novel double transgenic LSL- KrasG12D/CYP1B1-/- mice that have been established recently by this group. The impact of CYP1B1 deletion on estrogen metabolism within the lung will be examined in Specific Aim 1 by comparing the expression of genes involved in estrogen metabolism and estrogen metabolite profiles in lung tissue of female CYP1B1-/- and CYP1B1+/+ mice. In Aim 2, the feasibility of inhibiting CYP1B1 as a strategy for lung cancer prevention will be investigated using the LSL-KrasG12D mouse model. Inhibition of CYP1B1 will be achieved by gene deletion or administration of 2,3',4,5'-tetramethoxystilbene (TMS), a synthetic analog of resveratrol that is a selective inhibitor of CYP1B1. The effects of CYP1B1 inhibition on change in total tumor burden (tumor volume as determined by MRI) and tumor stage will be determined. Data obtained from the proposed studies are anticipated to reveal the potential utility of CYP1B1 as a molecular target for chemoprevention and provide novel insight into the contribution of estrogen metabolism to lung cancer development.