Host Defense Mechanisms in Polyaromatic Hydrogen Carcinogenesis

描述（由申请人提供）： 多芳族烃是普遍存在的环境化合物，是香烟烟雾中的主要致癌成分，并存在于波斯湾战争中燃烧的油田排放物中。人们对确定它们致癌的机制产生了强烈的实验兴趣。现在已知，多环芳烃7，12-二甲基苯并（a）蒽（DMBA）在H-ras癌基因的第61位密码子中产生特异性点突变，并且该突变是肿瘤发展所必需的。虽然很明显，由致癌的多环芳烃引起的肿瘤引起部分保护性免疫应答，但T细胞介导的免疫在皮肤致癌途径的早期阶段所起的作用尚不清楚。我们通过VA Merit Review Award资助的研究表明，将DMBA施用于小鼠皮肤导致抗原特异性T细胞介导的免疫应答，其赋予对DMBA诱导的肿瘤发展的抗性。T细胞应答至少部分针对第61位密码子中的H-ras突变，并且不发生对内源性非突变ras的免疫应答。基于这些研究结果，我们假设，疫苗接种策略导致T细胞介导的免疫多环芳烃产生的致癌基因突变，以保护个人免受这些药物的致癌作用，并努力扩大这种反应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，我们制备了一个基因免疫载体，该载体含有一个泛素突变型ras融合小基因序列，该序列提供了编码蛋白的上级蛋白体靶向。这促进MHC I类抗原加工，从而增强CD 8 + T细胞的产生。我们已经开发了稳定的树突状细胞系转染我们的载体，并打算使用它们来接种动物，以确定它们是否会预防DMBA诱导的皮肤肿瘤。我们还将评估树突状细胞接种我们的载体对T细胞亚群活化及其细胞因子谱的影响。研究计划评估树突状细胞接种突变型H-ras对肿瘤和非荷瘤DMBA处理皮肤中H-ras突变存在的影响。最后，我们将确定IL-12和IL-23在T细胞对突变型H-ras的反应中的作用，以及这些细胞因子的施用或通过抗体处理的中和是否会改变疫苗接种程序的功效。这些研究的长期目标是确定由致癌多环芳烃引起的肿瘤的免疫预防方法。退伍军人可能是这些方法的主要受益者，因为这一人口中吸烟者的比例很高，而且他们在波斯湾战争期间接触过这些制剂。 公共卫生相关性： 人们对确定化学物质致癌的机制很感兴趣。尤其是多环芳烃（PAH），这种致癌物质存在于香烟烟雾中，木炭烧烤的食物中，并在波斯湾战争期间在燃烧的油田中发现。多环芳烃是一个主要的，如果不是主要的，退伍军人中的致癌剂。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，因为它很容易接近，肿瘤也很容易识别。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，以确定它们是否能增强对多环芳烃的免疫力，并可用于预防肿瘤的发展。

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.