Host Defense Mechanisms in Polyaromatic Hydrogen Carcinogenesis

描述(由申请人提供)： 多环芳烃是一种普遍存在的环境化合物，是卷烟烟雾中的主要致癌物质，在波斯湾战争期间存在于燃烧的油田排放物中。人们对确定它们致癌的机制产生了浓厚的实验兴趣。目前已知多芳烃7，12-二甲基苯并(A)蒽(DMBA)会导致H-ras癌基因第61位密码子的特定点突变，该突变是肿瘤发生所必需的。虽然致癌多环芳烃引起的肿瘤可引起部分保护性免疫反应，但T细胞介导的免疫在皮肤癌变早期阶段所起的作用尚不清楚。我们通过VA Merit Review奖资助的研究表明，在小鼠皮肤上注射DMBA会产生抗原特异性T细胞介导的免疫反应，从而对DMBA诱导的肿瘤发展产生抵抗。T细胞的反应至少部分针对第61密码子的H-ras突变，不会对内源性的非突变ras产生免疫反应。基于这些发现，我们假设疫苗接种策略导致T细胞介导的对多环芳烃产生的癌基因突变的免疫有助于保护个人免受这些制剂的致癌作用，而放大这种反应的努力将进一步减少多环芳烃诱导的癌症的形成。为了验证我们的假设，我们准备了一个包含泛素-突变体ras融合微基因序列的遗传免疫载体，它提供了更好的蛋白质体靶向编码蛋白。这促进了MHC-I类抗原的处理，从而增强了CD8+T细胞的生成。我们已经建立了稳定的树突状细胞系，并打算将其用于免疫动物，以确定它们是否能预防DMBA诱导的皮肤肿瘤。我们还将评估用我们的载体接种树突状细胞对T细胞亚群激活及其细胞因子谱的影响。研究计划评估突变型H-ras树突状细胞疫苗对肿瘤和非荷瘤DMBA治疗皮肤中H-ras突变的影响。最后，我们将确定IL-12和IL-23在T细胞对突变的H-ras反应中的作用，以及这些细胞因子的应用或通过抗体治疗中和它们是否会改变疫苗接种程序的效果。这些研究的长期目标是确定免疫预防致癌多芳烃引起的肿瘤的方法。退伍军人可能是这种方法的主要受益者之一，因为吸烟者在这一人群中所占比例很高，而且他们在波斯湾战争期间接触到了这些毒剂。 公共卫生相关性： 人们对确定化学物质致癌的机制非常感兴趣。对于多环芳烃(PAHs)尤其如此，PAHs是存在于香烟烟雾、木炭烧烤食物中的致癌物质，在波斯湾战争期间在燃烧的油田中发现。在退伍军人中，多环芳烃即使不是主要的致癌物质，也是主要的致癌物质。它们会导致肺癌，并与头颈癌、膀胱癌和乳腺癌有关。皮肤是定义多环芳烃致癌过程的重要实验模型，因为它很容易接触到，而且很容易识别肿瘤。我们的研究表明，免疫系统、多环芳烃和多环芳烃产生的突变之间存在重要的相互作用。我们已经开发了新的试剂，并将其用作疫苗，以确定它们是否增强了对多环芳烃的免疫力，并可用于首先防止肿瘤的发展。

DESCRIPTION (provided by applicant): Polyaromatic hydrocarbons are ubiquitous environmental compounds that are the major carcinogenic moiety in cigarette smoke and were present in the burning oilfield emissions in the Persian Gulf War. There has been intense experimental interest in identifying the mechanisms by which they cause cancer. It is now known that the polyaromatic hydrocarbon 7,12- dimethylbenz(a)anthracene (DMBA) produces a specific point mutation in 61st codon of the H- ras oncogene and that this mutation is necessary for tumors to develop. While it is clear that the tumors caused by carcinogenic polyaromatic hydrocarbons elicit a partially protective immune response, the role that T-cell mediated immunity plays at earlier stages in the cutaneous carcinogenesis pathway is not well-understood. Our studies funded through a VA Merit Review Award have shown that administration of DMBA to the skin of mice results in an antigen specific T-cell mediated immune response that confers resistance to DMBA-induced tumor development. The T-cell response is directed, at least in part, at the H-ras mutation in the 61st codon and an immune response to the endogenous non-mutated ras does not occur. Based on these findings, we hypothesize that vaccination strategies resulting T-cell mediated immunity to oncogene mutations produced by polyaromatic hydrocarbons serves to protect individuals against the carcinogenic effects of these agents, and efforts to amplify that response will further reduce the formation of polyaromatic hydrocarbon-induced cancers. To test our hypothesis, we have prepared a genetic-immunization vector containing a ubiquitin-mutant ras fusion minigene sequence which provides superior proteosome targeting of the encoded protein. This promotes MHC class I antigen processing and thereby enhances the generation of CD8+ T-cells. We have developed stable dendritic cell lines transfected with our vector, and intend to us them to vaccinate animals to establish whether they will prevent the DMBA-induced skin tumors. We will also evaluate the effect of dendritic cell vaccination with our vector on activation of T-cell subsets and on their cytokine profiles. Studies are planned to assess the effect of dendritic cell vaccination with mutant H-ras on the presence of H-ras mutations in tumors and in non-tumor-bearing DMBA treated skin. Finally, we will determine the role of IL-12 and IL-23 in the T-cell response to mutant H-ras and whether administration of these cytokines or their neutralization through antibody treatment will alter the efficacy of the vaccination procedure. The long-term goal of these studies is to identify methods for the immunoprevention of tumors caused by carcinogenic polyaromatic hydrocarbons. Veterans are likely to be among the major beneficiaries of such methods because of the high proportion of smokers in this population and because of their exposure to these agents during the Persian Gulf War. PUBLIC HEALTH RELEVANCE: There is great interest in identifying the mechanisms by which chemicals cause cancer. This is especially true for polyaromatic hydrocarbons (PAHs), carcinogens that are present in cigarette smoke, charcoal broiled food, and were found in burning oilfields during the Persian Gulf War. PAHs are a major, if not the major, cancer producing agents among veterans. They cause lung cancer and have been implicated in cancers of the head and neck, bladder and breast. The skin is an important experimental model to define processes by which PAHs cause cancer, since it is easily accessible and tumors can be readily identified. Our studies suggest that there are important interactions between the immune system, PAHs and the mutations that PAHs produce. We have developed novel reagents and we utilize them as a vaccine to determine if they augment immunity to PAHs and can be used to prevent tumors from developing in the first place.