A concentration-dependent increase of the mutant frequency was induced by up to 10 μM chemically synthesized AOH of high purity at the hypoxanthine–guanine phosphoribosyltransferase (HPRT) and the thymidine kinase (TK) gene locus, respectively, in Chinese hamster V79 lung fibroblasts and mouse lymphoma L5178Y tk+/− cells (MLC) (Brugger et al. 2006). The gene discussed is TKT; the disease is lymphoma.