Isolation and Detection of Carcinogenic Nucleic Acid Adducts

Abstract

In general, nucleic acid adducts are formed when harmful chemical compounds react covalently with cellular DNA or RNA molecules. With only four natural nucleobases in DNA or RNA, identical nucleic acid adducts can theoretically occur at multiple positions within the human genome or transcriptome. The frequency of nucleic acid adduction is further increased by the reactivity of DNA or RNA to form adducts with many different types of chemicals, which include both exogenous compounds that our bodies have been exposed and endogenous compounds that are generated through normal metabolic activities in our bodies.1,2 Some exogenous compounds may require metabolic activation prior to the formation of nucleic acid adducts, whereas others may react directly with nucleic acids. If DNA adducts are not effectively removed by the DNA repair mechanism, the adducts can directly interfere with DNA replication and transcription.3 Similarly, the presence of adducts in RNA molecules can affect their biological functions. From the results of many experimental studies, the association of either DNA adducts or RNA adducts to cancer have already been well established. In the case of DNA adducts, it is widely recognized as the key element for the onset of carcinogenesis. Both DNA adducts and RNA adducts are, therefore, important biomarkers for cancer research, which include the monitoring of exposure to carcinogens, genetic mutation, DNA repair and so on. Similar to the analysis of other cancer biomarkers, both identification and quantification of nucleic acid adducts are required. Prior to the detection of nucleic acid adducts, it is important to ensure the biological or clinical samples are collected and stored properly. Equally important, the isolation of genomic DNA or RNA has to be carried out with high efficiency, which includes the yield and purity of selected material, reproducibility and the rate of sample throughput. For the detection of nucleic acid adducts, the requirements can be divided into the following order: