Nicotine, nicotinic receptors and lung cancer

描述（由申请人提供）：绝大多数肺癌与吸烟相关，大多数肺癌表达尼古丁乙酰胆碱受体（nAChR），其被香烟烟雾中的尼古丁激活。本申请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，最终目标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，可以是α和β亚基的混合物，也可以是5个相同的α亚基。烟碱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以其作为CNS中的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。我们的实验室一直是显示基本上所有肺癌表达nAChR的领导者，尼古丁与nAChR的结合刺激肺癌生长。尼古丁作为肺癌生长刺激物的真实的世界重要性最近已被多项全基因组关联研究证实，这些研究将尼古丁受体多态性与肺癌风险增加联系起来，即使在校正吸烟数量后也是如此。到目前为止，最强的联系是与15q25.1烟碱受体基因簇的多态性有关，该基因簇编码α 3、α 5和ω 4 nAChR亚基。重要的是，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，最令人感兴趣的多态性rs 16969968将15 nAChR亚基的残基398（a5 D398）处的Asp改变为Asn（a5 N398）如何影响肺癌生长是完全未知的。除了a5 D398到a5 N398突变之外，还可能在影响肺癌生长的15q25.1 nAChR基因位点中发生其他突变。因此，我们提出以下3个具体目标：1、确定尼古丁刺激肺癌生长所需的nAChR基因座中的a3、a5和<$4中的哪些烟碱受体亚型; 2、确定a5 D398突变为a5 N398的作用（rs 16969968）在介导肺癌的生长和发展增加中的作用;以及3.确定在a3、a5和rs 16969968中是否存在额外的常见多态性。4 nAChR亚基可能会增加肺癌对尼古丁的反应。由于非小细胞肺癌（NSCLC）比小细胞肺癌（SCLC）更常见，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NSCLC最常见的形式。这些目标将使用细胞生物学，电生理学和在裸鼠和转基因小鼠体内研究的组合来实现，以表征nAChR受体在肺癌中的作用。从这些研究中，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肺癌，以开发新的治疗方法。

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.