Mutagenicity of tobacco smoke in human cell co-cultures

描述（由申请人提供）：吸烟是许多部位癌症的主要原因，特别是空气消化道。多年来，有过滤嘴和低焦油含量的香烟已经存在，但由于代偿性吸烟行为，并没有减少与吸烟有关的癌症的发病率。最近，新版本的“低风险”香烟已经上市，但它们的相对致癌性尚不清楚。癌症是通过多阶段癌变产生的，这涉及到多年来基因损伤（如突变）的积累，直到细胞转化为癌症。目前对人类潜在致癌性的测定都有一定的缺陷。很少有模型使用正常的人类细胞，诱变通常不是终点。为了更好地了解潜在致癌物的风险，需要新的模型系统来评估这种风险。在初步研究中，我们发现，在将正常人口腔上皮细胞（NOE）与lacI大鼠报告细胞系（BB细胞-含有用于检测诱变的基于lambda的穿梭载体）的单层共培养中，与单独的BB细胞相比，苯并(a)芘（BaP）诱导的诱变增加。这种增加的突变性很可能是由于NOE激活了BaP。我们假设NOE's与lacI报告细胞共培养将允许检测与正常人类口腔细胞致癌物质代谢激活因果相关的突变。为了验证该模型，将研究两种烟草致癌物（BaP和亚硝基烟碱）诱导的诱变。在目的1中，我们将建立并表征由NOE与BB报告细胞共培养组成的共培养模型。在目标2中，该模型将用于：1)比较来自传统香烟和最近引入的“低风险”香烟的烟草烟雾冷凝物（TSC）诱导的诱变；2)确定这些TSC代谢的个体间差异。由于来自各种器官部位的人类细胞可以在培养物中生长，该模型有可能成为一个灵活的基础广泛的系统，以评估烟草制品在许多人体器官中的致癌性风险。第三个目标将是利用基因表达阵列和RT-PCR和western blotting确认，对有无TSC存在的NOE中细胞色素P- 450的水平进行初步研究。由于NOE正是注定要发展成口腔癌的细胞，该模型填补了作为一种器官特异性技术来量化突变的潜力的空白，突变是癌变的一个重要步骤。显然，最好是前瞻性地确定它们的潜在风险，而不是回顾性地确定。

DESCRIPTION (provided by applicant): Tobacco smoking is a major cause of cancers at many sites, particularly the aerodigestive tract. For many years, filter and reduced tar cigarettes have been available, but have not resulted in reduced incidences of smoking-related cancers, because of compensatory smoking behavior. Recently, newer versions of "reduced-risk" cigarettes have been marketed, but their relative carcinogenicities are unknown. Cancer arises through multistage carcinogenesis, which involves the accumulation of genetic damage (such as mutations), over years, until a cell converts to cancer. Current assays for potential carcinogenesis in humans all have certain deficiencies. Few models employ normal human cells and mutagenesis is generally not an endpoint. To better understand risk from potential carcinogens, new model systems that can evaluate such risk are needed. In preliminary studies, we showed that in monolayer co-culture of normal human oral epithelial cells (NOE's) with a lacI rat reporter cell line (BB cells - that contain a lambda-based shuttle vector for detecting mutagenesis), increased mutagenesis induced by benzo(a)pyrene (BaP), relative to BB cells alone. This increased mutagenesis is most likely due to activation of BaP by the NOE's. We hypothesize that co-culturing NOE's with lacI reporter cells will allow detection of mutagenesis that is causally linked to metabolic activation of carcinogens by the normal human oral cells. To validate the model, mutagenesis induced by the two tobacco carcinogens (BaP and nitrosonornicotine) will be investigated. In Aim 1 we will establish and characterize a co- culture model composed of NOE's co-cultured with BB reporter cells. In Aim 2, this model will be used: 1) to compare mutagenesis induced by tobacco smoke condensate (TSC) from conventional cigarettes and recently-introduced "low-risk" cigarettes and 2) to determine inter-individual variation in the metabolism of these TSC's. Since human cells from a variety of organ sites can be grown in culture, the model has potential to become a flexible broad-based system to evaluate carcinogenicity risk of tobacco products in a number of human organs. A third aim will be a pilot study on the levels of cytochrome P- 450's in NOE's with and without the presence of TSC's, using gene expression arrays and confirmation by RT-PCR and western blotting. As NOE's are the very cells that are destined to develop into oral cancers, the model fills a void with the potential of being an organ specific technique to quantify mutagenesis, a major step in carcinogenesis. Clearly, it is preferable to determine their potential risk prospectively, rather than retrospectively.