Nicotine, nicotinic receptors and lung cancer

描述（由申请人提供）：绝大多数肺癌与吸烟有关，大多数肺癌表达尼古丁乙酰胆碱受体（nAChR），该受体被香烟烟雾中的尼古丁激活。本应用的目的是表征尼古丁与肺癌表达的尼古丁乙酰胆碱受体（nAChR）的相互作用如何刺激肿瘤生长，最终目的是通过阻断这种增殖途径开发新的肺癌治疗方法。烟碱受体是由5个亚基组成的配体门控离子通道，这些亚基可以是a和¿亚基的混合物，也可以是5个相同的a亚基。尼古丁激动剂如乙酰胆碱或尼古丁的结合打开离子通道，允许Na+或Ca++进入细胞。虽然nAChR以其在中枢神经系统中作为神经递质受体的作用而闻名，但它们也广泛表达于非神经元细胞中。我们的实验室在证明基本上所有肺癌都表达nAChR和尼古丁与nAChR结合刺激肺癌生长方面一直处于领先地位。最近，多项全基因组关联研究证实了尼古丁受体的多态性与肺癌风险增加之间的联系，即使对吸烟数量进行了校正，尼古丁作为肺癌生长刺激物的现实重要性也得到了证实。到目前为止，最强的联系是与编码a3， a5和¿4 nAChR亚基的15q25.1烟碱受体基因簇的多态性。关键的是，这些nAChR亚基在介导尼古丁刺激癌症生长的能力中的确切作用尚不清楚。此外，我们最感兴趣的多态性rs16969968是如何将15个nAChR亚基398位（a5D398）的Asp改变为Asn （a5N398）的，对肺癌生长的影响是完全未知的。除了a5D398到a5N398突变外，15q25.1 nAChR基因位点也可能发生影响肺癌生长的其他突变。因此，我们提出以下3个具体目的：1、确定尼古丁刺激肺癌生长需要a3、a5和¿4 nAChR基因位点的哪些尼古丁受体亚型；2、确定a5D398 - a5N398突变（rs16969968）在促进肺癌生长发展中的作用；3、确定在a3、a5和¿4 nAChR亚基中是否存在可能增加肺癌对尼古丁反应的其他常见多态性。由于非小细胞肺癌（NSCLC）比小细胞肺癌（SCLC）更为常见，我们将重点关注NSCLC，特别是鳞状细胞肺癌（SCC）和肺腺癌（AC），这是最常见的非小细胞肺癌形式。这些目标将通过细胞生物学、电生理学和裸鼠和转基因小鼠体内研究的混合来实现，以表征nAChR受体在肺癌中的作用。通过这些研究，我们将了解哪些nAChR受体介导尼古丁对肺癌生长的影响，从而确定哪些nAChR和增殖途径可以有效地靶向，从而开发新的肺癌治疗方法。

DESCRIPTION (provided by applicant): The overwhelming majority of lung cancers are associated with smoking and most lung cancers express nicotinic acetylcholine receptors (nAChR) that are activated by the nicotine in cigarette smoke. The objective of this application is to characterize how the interaction of nicotine with nicotinic acetylcholine receptors (nAChR) expressed by lung cancers stimulates tumor growth with the ultimate objective of developing new therapeutic approaches to lung cancer by blocking this proliferative pathway. The nicotinic receptors are ligand-gated ion channels composed of 5 subunits, either a mixture of a and ¿ subunits or 5 of the same a subunit. Binding of a nicotinic agonist such as acetylcholine or nicotine opens the ion channel allowing entry of Na+ or Ca++ into the cell. While the nAChR are best known for their role as neurotransmitter receptors in the CNS, they are also widely expressed in non-neuronal cells. Our laboratory has been a leader in showing that essentially all lung cancers express nAChR and binding of nicotine to the nAChR stimulates lung cancer growth. The real world importance of nicotine as a stimulus for lung cancer growth has recently been confirmed by multiple genome-wide association studies linking polymorphisms in nicotinic receptors to increased risk of lung cancer even when corrected for numbers of cigarettes smoked. Strongest linkage by far has been with polymorphisms in the 15q25.1 nicotinic receptor gene cluster that encodes thea3, a5 and ¿4 nAChR subunits. Critically, the exact role of these nAChR subunits in mediating the ability of nicotine to stimulate cancer growth is unknown. In addition, how the polymorphism of greatest interest, rs16969968 which changes the Asp at residue 398 (a5D398) of the 15 nAChR subunit to Asn (a5N398) affects lung cancer growth is totally unknown. It is also likely that besides the a5D398 to a5N398 mutation, other mutations occur in the 15q25.1 nAChR gene locus that affects lung cancer growth. Therefore, we propose the following 3 specific aims: 1, To determine which nicotinic receptor subtypes in the a3, a5 and ¿4 nAChR gene locus are required for nicotine to stimulate lung cancer growth; 2, To determine the role of the a5D398 to a5N398 mutation (rs16969968) in mediating increased growth and development of lung cancer; and 3, To determine if there are additional common polymorphisms in the a3, a5 and ¿4 nAChR subunits that may increase lung cancer responses to nicotine. Because non-small cell lung cancer (NSCLC) is much more frequent than small cell lung carcinoma (SCLC) we will focus on NSCLC and specifically on squamous cell lung carcinoma (SCC) and lung adenocarcinoma (AC) which are the most frequent forms of NSCLC. These aims will be accomplished using a mix of cell biology, electrophysiology and in vivo studies in nude and transgenic mice to characterize actions of the nAChR receptors in lung cancer. From these studies will come understanding of which nAChR receptors mediate the effects of nicotine on lung cancer growth and thus identify which nAChR and proliferative pathways can be effectively targeted to develop new therapeutic approaches for lung cancer. PUBLIC HEALTH RELEVANCE: Lung cancer is the number one cause of cancer death in the United States and therapies for lung cancer remain dismal. By far the overwhelming majority of lung cancer occurs in smokers. The purpose of this application is to understand how nicotine stimulates the growth of lung cancers and ultimately develop new therapies for lung cancer by blocking the ability of nicotinic receptor signaling to stimulate lung cancer growth.