The human cancer cell lines DU145, HCT116, HCT116N and SW480 have mutation rates (mutations per cell per generation) in the hprt gene locus of 529 × 10−7, 77.5 × 10−7, 5.9 × 10−7 and 0.75 × 10−7, respectively54, and the relative emission intensities of 2 (5 μM) at 5.1 μM of DNA are 7.7, 5.8, 3.7 and 2.3, respectively (Fig. 6a shows an increase of emission intensity at 0–5.1 μM of genomic DNA from different cancer cells). This evidence concerns the gene HPRT1 and cancer.