Nicotine, nicotinic receptors and lung cancer

描述(申请人提供)：绝大多数肺癌与吸烟有关，大多数肺癌表达烟碱型乙酰胆碱受体(NAChR)，该受体由香烟烟雾中的尼古丁激活。这项应用的目的是描述尼古丁与肺癌表达的烟碱型乙酰胆碱受体(NAChR)相互作用如何刺激肿瘤生长，最终目的是通过阻断这一增殖途径来开发肺癌的新治疗方法。烟碱受体是由5个亚基组成的配基门控离子通道，既可以是α和β亚基的混合物，也可以是同一个α亚基的5个亚基。结合烟碱激动剂，如乙酰胆碱或尼古丁，打开离子通道，允许Na+或Ca++进入细胞。虽然nAChR在中枢神经系统中作为神经递质受体而闻名，但它们也在非神经细胞中广泛表达。我们的实验室一直是表明基本上所有肺癌都表达nAChR的领先者，尼古丁与nAChR的结合会刺激肺癌的生长。尼古丁作为肺癌生长刺激物的现实世界重要性最近得到了多项全基因组关联研究的证实，该研究将尼古丁受体的多态与肺癌风险增加联系在一起，即使在校正吸烟数量的情况下也是如此。到目前为止，最强的关联与15q25.1尼古丁受体基因簇的多态有关，该基因簇编码a3、a5和？4nAChR亚基。关键的是，这些nAChR亚基在调节尼古丁刺激癌症生长能力方面的确切作用尚不清楚。此外，最令人感兴趣的多态rs16969968将15个nAChR亚基的第398位天冬氨酸(A5D398)改变为天冬氨酸(A5N398)是如何影响肺癌生长的完全未知。也有可能的是，除了a5D398到a5N398突变外，15q25.1 nAChR基因位点还存在影响肺癌生长的其他突变。因此，我们提出了以下三个特定目标：1，确定A3，a5和？4 nAChR基因座上的哪些尼古丁受体亚型是尼古丁刺激肺癌生长所必需的；2，确定a5D398到a5N398突变(Rs16969968)在调节肺癌生长和发展中的作用；以及3，确定A3，a5和？4 nAChR亚单位是否存在其他常见的多态可能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)这两种最常见的非小细胞肺癌。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组合来实现，以表征nAChR受体在肺癌中的作用。从这些研究将了解哪些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开发肺癌的新治疗方法。

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.