Characterisation and quantification of O6-alkylguanine adducts in DNA for clinical assessment of cancer risk

DNA暴露于烷化剂可产生烷基化DNA碱基加合物，其在DNA复制后诱导突变（碱基变化）。破坏碱基鸟嘌呤以产生O 6-烷基鸟嘌呤被认为是这些过程中最有害的过程之一，并导致突变模式，这在被诊断患有结直肠癌的患者中特别常见，结直肠癌是英国第三大常见癌症。尽管化学工作者可能直接暴露于烷基化剂，但还有许多其他暴露来源，包括环境（例如吸入烟草烟雾或车辆尾气）、膳食（例如许多食物中发现的N-亚硝胺）或癌症化疗后涉及使用甲基化剂，例如替莫唑胺。虽然O 6-甲基鸟嘌呤等加合物的特征相当好，但在DNA中检测到许多其他类型的加合物，例如O 6-（羧甲基）鸟嘌呤，其形成与红肉含量高的饮食有关。O 6-烷基鸟嘌呤的性质及其在人DNA中加合物的相对含量的表征（例如，从活检）将允许在定义癌症风险方面做出相当大的改进，此外，在监测接受化疗的患者方面也将非常有益。该项目建立在我们在核酸化学和生物学方面的专业知识基础上，旨在进一步研究O 6-烷基鸟嘌呤，可以出现在人类DNA中，并开发其定量方法。技术将涉及合成的有机和核酸化学的合成O 6-烷基鸟苷和标记的标准，O 6-烷基鸟嘌呤含寡脱氧核糖核苷酸和分析技术的发展，如质谱法，以确定和准确地定量O 6-烷基鸟嘌呤加合物的DNA。

Exposure of DNA to alkylating agents can produce alkylated DNA base adducts that induce mutations (base changes) following DNA replication. Damage to the base guanine to produce an O6-alkylguanine is considered to be one of the more detrimental of these processes and results in mutational patterns that are particularly common in patients diagnosed with colorectal cancer, the third most common cancer in the UK. Although chemical workers may be exposed directly to alkylating agents, there are many other sources of exposure that include environmental e.g. inhalation of tobacco smoke or vehicle exhaust fumes, dietary e.g. N-nitrosamines found in many foods or following cancer chemotherapy involving the use of methylating agents such as temozolomide. Although adducts such as O6-methylguanine are fairly well characterised, there are many other types of adducts that have been detected in DNA, for example O6-(carboxymethyl)guanine whose formation has been linked to diets high in red meat. Characterising the nature of O6-alkylguanines and the relative amounts of such adducts in human DNA (e.g. from a biopsy) would allow considerable improvements to be made in defining cancer risk and additionally would be hugely beneficial in monitoring patients undergoing chemotherapy.This project builds on our expertise in nucleic acid chemistry and biology and aims to further characterise the O6-alkylguanines that can arise in human DNA and to develop methods for their quantification. Techniques will involve synthetic organic and nucleic acid chemistry for the synthesis of O6-alkylguanosine and labelled standards, O6-alkylguanine-containing oligodeoxyribonucleotides and the development of analytical techniques such as mass spectrometry to characterise and to accurately quantify O6-alkylguanine adducts in DNA.