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

将DNA暴露在烷化剂中可产生烷基化的DNA碱基加合物，从而在DNA复制后引起突变(碱基变化)。在这些过程中，对碱基鸟嘌呤的破坏以产生O6-烷基鸟嘌呤被认为是最有害的过程之一，并导致突变模式，这种突变模式在被诊断为结直肠癌的患者中尤其常见。结直肠癌是英国第三种最常见的癌症。虽然化学工人可能直接接触烷化剂，但还有许多其他接触来源，包括环境因素，如吸入烟草烟雾或汽车尾气，饮食，如许多食物中发现的N-亚硝胺，或在癌症化疗后使用甲基化试剂，如替莫唑胺。虽然O6-甲基鸟嘌呤等加合物的特征很好，但在DNA中检测到了许多其他类型的加合物，例如O6-(羧甲基)鸟嘌呤，其形成与高红肉饮食有关。确定O6-烷基鸟嘌呤的性质和这种加合物在人类DNA中的相对数量(例如来自活组织检查)将允许在确定癌症风险方面取得相当大的改进，此外还将在监测接受化疗的患者方面大有裨益。这个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，旨在进一步表征人类DNA中可能出现的O6-烷基鸟嘌呤，并开发它们的量化方法。技术将涉及合成O6-烷基鸟苷和标记标准的合成有机化学和核酸化学、含O6-烷基鸟嘌呤的寡聚脱氧核苷酸，以及开发分析技术，如质谱学，以表征和准确量化DNA中的O6-烷基鸟嘌呤加合物。

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.