The mono-functional hAAG enzyme exhibits broad substrate specificity and is responsible for the recognition and excision of a diverse group of alkylated purine bases (e.g. 3-methyladenine, 7-methylguanine and 1-N6-ethenoadenine) and the removal of hypoxanthine from deoxyinosine-containing DNA (Fig. S1, ESI†).19,20 Therefore, the simultaneous measurement of hOGG1 and hAAG activities is of great importance for the clinical diagnosis of lung cancer. Here, OGG1 is linked to lung carcinoma.