Nicotine in Pancreatic Cancer: Molecular Mechanisms

描述（由申请人提供）：胰腺导管腺癌（PDA）是美国成人癌症死亡的第四大原因。2007年，美国的PDA新病例估计为37,180例。不幸的是，大多数人将死于这种疾病。这种癌症在吸烟的人群中发病率最高。尼古丁是香烟烟雾的重要成分，已被证明可以激活几种癌症中促进生长的途径。然而，人们对尼古丁导致PDA攻击性的途径知之甚少。因此，迫切需要剖析尼古丁介导PDA进展的基本分子机制。在这个探索性应用中，我们建议研究尼古丁诱导的导致胰腺癌进展的分子和细胞变化所涉及的信号通路。我们建议关注骨桥蛋白（OPN）在胰腺癌细胞中与恶性肿瘤的发生和发展有关的相互作用。OPN是一种分泌的糖基化蛋白，可变丝氨酸磷酸化，结合整合素和某些CD44变异体，触发细胞内信号事件级联，调节细胞运动、存活和增殖。我们的初步结果为PDA、尼古丁和OPN之间的复杂关系提供了新颖而有趣的见解。在胰腺癌细胞中添加尼古丁可显著增加OPN mRNA和蛋白的表达。此外，暴露于香烟烟雾的大鼠显示出胰腺OPN mRNA和蛋白表达的剂量依赖性上调。对PDA患者癌组织的分析显示，在胰腺腺泡和恶性导管中存在大量的OPN。目前尚不清楚OPN在介导尼古丁在胰腺癌中的致瘤作用中起什么作用，如果有的话。因此，在拟建的研究中，我们将利用胰腺癌细胞系研究尼古丁刺激和OPN激活的下游信号通路，以促进癌变。我们将探讨包括Src、FAK、PKC和AKT/PI 3-激酶在内的OPN下游单链通路在调节胰腺癌细胞迁移和增殖中的作用。在人PDA组织中，OPN的表达将与血管生成和增殖标志物相关，其表达水平将在吸烟者和非吸烟者的原发和转移部位进行比较。我们假设尼古丁通过增强OPN表达和随后激活下游信号事件介导其在胰腺癌中的致癌作用。我们进一步提出，阻断OPN的表达和/或功能可能是一种新的治疗方法，可以降低胰腺癌细胞的致瘤性，抑制手术切除后的转移和复发，特别是在吸烟人群中。我们的研究将引入新的机制见解，并更好地理解尼古丁作为胰腺癌发生和发展的主要危险因素的作用。公共卫生相关性：在这项探索性研究中，我们建议辨别尼古丁诱导的OPN促进PDA进展的分子和细胞过程。一个强大的研究人员和临床医生团队将进行拟议的研究。Charles Yeo负责胰腺癌和外科肿瘤学，David Denhardt负责骨桥蛋白信号传导和癌症转移，以及我们在胰腺病理学和骨桥蛋白信号传导和胰腺调节方面的专业知识。我们的研究数据可能会带来新的机制见解，到目前为止，尼古丁和OPN之间存在未知的功能联系。解开这些机制将有助于更好地理解尼古丁作为胰腺癌主要危险因素的作用。

DESCRIPTION (provided by applicant): Pancreatic ductal adenocarcinoma (PDA) is the fourth leading cause of adult cancer mortality in the United States. In 2007, the number of new PDA cases in the United States is estimated at 37,180. Unfortunately, most will die of this disease. This type of cancer has the highest incidence in people who smoke cigarettes. Nicotine is an important component of cigarette smoke and has been shown to activate growth-promoting pathways in several cancers. However, the means through which nicotine contributes to the aggressive nature of PDA is poorly understood. There is, therefore, an urgent need to dissect the basic molecular mechanisms that are initiated by nicotine to mediate PDA progression. In this exploratory application we propose to study the signaling pathways involved in the nicotine-induced molecular and cellular changes that lead to pancreatic cancer progression. We propose to focus on the interactions of osteopontin (OPN) in pancreatic cancer cells with regard to the initiation and progression of malignancy. OPN is a secreted glycosylated protein, variably serine-phosphorylated, that binds integrins and certain CD44 variants, triggering a cascade of intracellular signaling events regulating cell motility, survival and proliferation. Our preliminary results provide novel and intriguing insights into a complex relationship among PDA, nicotine, and OPN. Addition of nicotine to pancreatic cancer cells induced a significant increase in OPN mRNA and protein expression. Moreover, rats that were exposed to cigarette smoke show a dose-dependent upregulation in pancreatic OPN mRNA and protein expression. Analysis of cancer tissue from PDA patients showed the presence of significant amounts of OPN in the pancreatic acini and in the malignant ducts. It is unknown what role, if any, OPN plays in mediating the tumorigenic effects of nicotine in pancreatic cancer. Thus, in the proposed studies we will utilize pancreatic cancer cell lines to investigate the downstream signaling pathways that are stimulated by nicotine and activated by OPN to promote carcinogenesis. We will address the involvement of OPN downstream singling pathways that involve Src, FAK, PKC, and AKT/PI 3-kinase in modulating migration and proliferation of pancreatic cancer cells. In human PDA tissue, the expression of OPN will be correlated with angiogenesis and proliferation markers and its expression levels will be compared in patients who are smokers and non-smokers in primary and metastatic sites. We hypothesize that nicotine mediates its carcinogenic effects in pancreatic cancer through enhancement of OPN expression and subsequent activation of downstream signaling events. We further propose that blocking OPN expression and/or function may represent a novel therapeutic approach to reduce pancreatic cancer cell tumorigenicity and inhibit metastasis and recurrence after surgical resection, especially in the cigarette-smoking population. Our studies will introduce novel mechanistic insights and a better understanding of the role of nicotine as a major risk factor in the development and progression of pancreatic cancer. PUBLIC HEALTH RELEVANCE: In this exploratory study, we are proposing to discern the molecular and cellular processes through which nicotine-induced OPN contributes to the progression of PDA. A powerful team of researchers and clinicians will conduct the proposed studies: Drs. Charles Yeo in pancreatic cancer and surgical oncology, David Denhardt, in osteopontin signaling and cancer metastasis, and our expertise in pancreatic pathology and osteopontin signaling and regulation in the pancreas. Data from our studies are likely to lead to novel mechanistic insights and as yet, an unknown functional link between nicotine and OPN. Unraveling these mechanisms will lead to better understanding of the role of nicotine as a major risk factor in pancreatic cancer.