The Molecular Profile of Prostate Tumors in Smokers

我们提出的假设是，现在吸烟者、过去吸烟者和从不吸烟者的前列腺癌在基因表达谱上表现出差异，这与当前吸烟者肿瘤中不同的致癌分子变化是一致的。我们还在探索尼古丁对人类前列腺癌细胞和流浪鼠的影响，并正在评估这些变化是否类似于前列腺癌中吸烟相关的变化。这项研究旨在确定吸烟诱导前列腺癌进展的机制，并确定尼古丁在这一过程中的具体作用。这项提议将新颖性与高影响力的概念结合在一起。如果我们发现尼古丁会导致疾病转移，结果可能会对公共卫生产生重大影响。烟草烟雾含有许多化学物质，包括许多破坏DNA和致癌的化学物质。亚硝胺是烟草烟气中一类重要的致癌物质，是香烟在收获后加工和燃烧过程中产生的尼古丁生物碱。最近，尼古丁和亚硝胺被发现通过受体-中介机制激活非神经性哺乳动物细胞中的信号通路。这些途径中有几个与癌症有关，促进细胞存活、血管生成和转移。例如，尼古丁激活Akt途径，这是许多癌症发生和发展的关键途径，包括前列腺癌。此外，尼古丁在当前吸烟者的血液中可以达到高纳摩尔稳态浓度，如果靶细胞表达适当的受体，可能会激活肺以外的器官的信号通路。为了这项研究，我们收集了67例前列腺癌患者，其中包括16名当前吸烟者、28名既往吸烟者和23名从不吸烟者。这些研究是从我们的资源合同NCI CPCTR和约翰·霍普金斯大学医疗机构获得的。这些肿瘤的临床特征在现在吸烟者、过去吸烟者和从不吸烟者中是相似的。在一项试验中，我们分析了9名当前吸烟者、21名过去吸烟者和17名从不吸烟者的肿瘤基因表达谱。这项分析揭示了一个非常明显的特征，将肿瘤与现在吸烟者和从未吸烟者和过去吸烟者区分开来。由于第一个数据集只包含9名当前吸烟者的肿瘤，约翰霍普金斯大学医疗机构的泌尿外科收集了额外的前列腺癌(与Jun Luo和William Isaacs合作)，并与现有样本相结合，以增强我们研究的统计能力，以确定在现在吸烟者和从未/过去吸烟者之间差异表达的其他基因。对现在吸烟者和从不吸烟者的肿瘤进行比较，得到了98个转录本，编码73个差异表达的基因。第二项比较，现在吸烟者和过去吸烟者/从不吸烟者，导致只有70个转录本编码40个差异表达基因的较短列表。这项研究可能是吸烟对既往吸烟者肿瘤基因特征的残余影响，当比较现在吸烟者和过去/从未吸烟者的组合时，这项研究产生的基因较少。许多差异表达的基因都具有已知的免疫调节功能。该列表还包括白介素8(IL-8)，以及其他几个差异基因被发现与肝细胞生长因子(HGF)有关。后者是耐人寻味的，因为尼古丁和HGF都激活了共同的通路，例如PI3激酶-Akt轴。我们的一些观察结果是初步的，需要进一步验证。然而，数据显示，目前的吸烟状态会在前列腺癌中产生一个基因签名，这可能会揭示吸烟导致前列腺癌转移扩散的机制。这些观察结果正在进行更多的研究。我们用免疫组织化学方法研究了前列腺癌患者中IL-8的相对丰度和表达模式，并分析了97例前列腺癌患者和87例已知吸烟的前列腺癌对照人群的血浆样本，以了解目前吸烟的前列腺癌患者的血液中IL-8水平是否高于既往吸烟者或从不吸烟者，或者高于人群对照组。免疫组织化学显示，目前吸烟者前列腺中的肿瘤上皮细胞和浆细胞样免疫细胞均表达IL-8。对病例和对照组的血浆样本的分析表明，在病例和基于人群的对照组中，与既往吸烟者和从不吸烟者相比，目前吸烟者的前列腺癌患者血液样本中的IL-8含量增加。此外，在以人群为基础的对照组中，目前的吸烟者的IL-8血浆浓度并没有像现在的吸烟者那样升高，这表明主动吸烟可能会导致前列腺癌中IL-8的升高，这些患者的血液中可以检测到IL-8。流行病学研究发现，IL-8的产生增加也可能促进当前吸烟者前列腺癌的更具侵袭性的行为，导致这一患者组更多的转移。目前，我们正在评估血浆淋巴毒素水平，以了解目前吸烟者的血浆淋巴毒素是否增加，这些吸烟者也是前列腺癌患者。我们正在跟进最近的一项观察，即前列腺癌中的B细胞可以通过淋巴毒素介导的机制加速前列腺癌的进展。最后，我们已经开始分析接受生理浓度尼古丁12周或仅接受自来水的流浪鼠前列腺癌的基因表达谱。本实验旨在将尼古丁诱导的基因表达谱与当前吸烟者的前列腺癌基因表达谱进行比较。我们的假设是这两个数据集有一个共同的特征。

We are pursuing the hypothesis that prostate tumors from current, past, and never smokers exhibit differences in their gene expression profiles that are consistent with distinct oncogenic molecular alterations in tumors of current smokers. We are also exploring the effects of nicotine in human prostate cancer cells and TRAMP mice, and are evaluating whether those resemble smoking-associated alterations in prostate tumors. This research is aimed at identifying the mechanisms by which cigarette smoking induces prostate cancer progression, and to define the specific role of nicotine in this process. This proposal combines novelty with a high-impact concept. If we find that nicotine induces disease metastasis, the results could have significant public health implications. Tobacco smoke contains numerous chemicals, including many that are DNA-damaging and carcinogenic. Nitrosamines that are produced from the alkaloid nicotine during post-harvest processing and the burning process of cigarettes are an important group of carcinogens in tobacco smoke. Recently, nicotine and nitrosamines were found to activate signaling pathways in non-neuronal mammalian cells by receptor-mediator mechanisms. Several of these pathways are cancer-related and promote cell survival, angiogenesis, and metastasis. For example, nicotine activates the Akt pathway, which is a key pathway in the development and progression of many cancers, including prostate cancer. In addition, nicotine can reach high nanomolar steady-state concentrations in the blood of current smokers that may activate a signaling pathway in organs other than lung if the appropriate receptors are expressed by the target cells. We collected 67 prostate tumors from 16 current, 28 past, and 23 never smokers for the study, which we obtained from the NCI CPCTR, our resource contract, and Johns Hopkins Medical Institutions. The clinical characteristics of these tumors are similar among current, past, and never smokers. In a pilot, we analyzed the gene expression profiles of tumors from 9 current, 21 past, and 17 never smokers. This analysis revealed a very distinct signature that differentiated tumors from current smokers from those of never and past smokers. Because the first dataset contained tumors from only 9 current smokers, additional prostate tumors were collected at the Department of Urology, Johns Hopkins Medical Institutions (in collaboration with Jun Luo and William Isaacs) and combined with the existing samples to increase the statistical power of our study to identify additional genes that are differentially expressed between current and never/past smokers. The comparison of tumors from current and never smokers yielded 98 transcripts encoding 73 differentially expressed genes. A second comparison, current versus past/never smokers, resulted in a shorter list of only 70 transcripts encoding 40 differentially expressed genes. Likely a residual effect of smoking on the tumor gene signature in past smokers, this study yielded fewer genes when the current and combined past/never smokers were compared. Many of the differentially expressed genes have known immune-regulatory functions. The list also contained interleukin 8 (IL-8), and several others of the differentially genes were found to have an association with hepatocyte growth factor (HGF). The latter is intriguing because both nicotine and HGF activate common pathways, e.g., the PI3 kinase-Akt axis. Some of our observations are preliminary and will need further validation. Nevertheless, the data show that a current smoking status generates a gene signature in prostate tumors that could reveal the mechanism by which smoking causes the metastatic spread of prostate cancer. These observations are being followed up with additional research. We evaluated the relative abundance and expression pattern of IL-8 in prostate tumors from current, former, and never smokers by immunohistochemistry, and also analyzed plasma samples from prostate cancer cases (n = 97) and matched population-based controls (n = 87) with known smoking status to find out whether patients with prostate cancer who are current smokers have higher IL-8 levels in their blood than former or never smokers, or than population-based controls. Immunohistochemistry revealed that IL-8 is expressed by the tumor epithelium and by plasma cell-like immune cells in the prostate of current smokers. The analysis of plasma samples from cases and controls showed that IL-8 is increased in blood samples of prostate cancer patients who are current smokers when compared to former and never smokers among cases and population-based controls. Furthermore, current smokers among population-based controls did not have the same increased IL-8 plasma concentrations that current smoking cases had, indicating that active smoking may lead to increased IL-8 in prostate tumors that can be detected in the blood of these patients. This increased production of IL-8 may also promote the more aggressive behavior of prostate tumors in current smokers, leading to more metastases in this patient group, as found by epidemiological studies. Currently, we are evaluating plasma for lymphotoxin levels to see whether lymphotoxin is increased in the plasma of current smokers who are also prostate cancer patients. We are following up on a recent observation that B cells in prostate tumors can accelerate prostate cancer progression by a lymphotoxin-mediated mechanism. Lastly, we have started to analyze gene expression profiles from the cancerous prostate of TRAMP mice that received physiological concentrations of nicotine for 12 weeks, or tap water only. This experiment is designed to compare the nicotine-induced profiles with the gene expression profiles in prostate tumors from current smokers. It is our hypothesis that these two datasets have a common signature.