BIOMARKERS OF CARCINOGENESIS

众所周知，癌症的发生涉及多个步骤的体细胞突变。在过去的二十年里，已经开发了各种生物标记物来检测人类致癌暴露的早期染色体和突变效应。尽管这些生物标记物已被证明与广泛的致癌暴露有关，但它们并不是真正的早期影响生物标记物，因为它们不在环境诱发癌症的致病途径上。这些生物标记物应该比目前可用的更好地预测癌症风险的增加。特定的染色体重排和基因甲基化改变被认为是白血病、淋巴瘤、肺癌和膀胱癌发生的关键因素。我们计划为一些白血病/淋巴瘤相关的易位(例如1(12；21)和t(14；18))开发新的实时定量聚合酶链式反应方法和甲基化特异性的聚合酶链式反应方法，使我们能够检测各种癌症相关基因(例如p16/INK4a和p14/ARF)的甲基化状态。然后，我们将对这些标记物中的一些与非霍奇金淋巴瘤的相关性进行初步测试，并检查它们在包括新生儿在内的普通人群中的流行率。目前，关于人类血液中是否存在易位存在相当大的争论，特别是在新生儿中。此外，我们将使用这些新的标记物进行体外细胞培养研究，以检查超级基金化学品砷和苯在关键目标细胞中产生的染色体损伤和基因甲基化异常的性质。我们还计划使用实时荧光定量聚合酶链式反应(Real-Time-PCR)方法，在项目2下收集的儿童白血病病例的新生儿血液样本中追溯白血病的出生。这将确定白血病病例出生时血液中是否存在易位或倒置，并为潜在预测儿童白血病开辟新的途径。最后，我们将应用甲基化特异性聚合酶链式反应方法对项目2下收集的白血病骨髓样本中的特定基因以及项目3下收集的砷流行区肺和膀胱肿瘤中的特定基因进行检测，以确定肿瘤中是否存在化学特异性基因甲基化模式。

Carcinogenesis is known to involve multiple steps of somatic mutation. During the last two decades various biomarkers have been developed to detect early chromosomal and mutational effects of carcinogenic exposure in humans. Although these biomarkers have been shown to be associated with a wide range of carcinogenic exposures, they are not truly biomarkers of early effect as they are not on the causal pathway of environmentally-induced cancers. These biomarkers should be better predictors of increased cancer risk than those currently available. Specific chromosome rearrangements and altered gene methylation are known to be key factors in the development of leukemia, lymphoma, lung and bladder cancer. We plan to develop novel quantitative real time PCR methods for a number of leukemia/lymphoma-related translocations (e.g. 1 (12;21) and t(14;18)) and methylation-specific PCR methods that allow us to examine the methylation status of various cancer-related genes (e.g.p16/INK4a and p14/ARF. We will then make an initial test of the association of some of these markers with non-Hodgkins lymphoma and examine their prevalence in the general population, including newborns. There is currently considerable debate about the presence of translocations in human blood, especially in newborns. In addition, we will perform in vitro cell culture studies with these new markers to examine the nature of the chromosomal damage and aberrant gene methylation produced in critical target cells by the Superfund chemicals, arsenic and benzene. We also plan to use the real-time PCR methods to backtrack leukemia to birth in newborn blood samples from childhood leukemia cases collected under Project 2. This will determine if the translocations or inversions present in the blood of leukemia cases were present at birth and open up new avenues for potentially predicting childhood leukemia. Finally, we will apply the methylation specific-PCR methods to specific genes in leukemia marrow samples collected under Project 2 and in lung and bladder tumors from arsenic endemic areas collected under Project 3, to determine if chemical-specific gene methylation patterns exist in the tumors.