The results showed that the abundance of 53BP1 foci, an indicator of DDR, is much higher at telomeres and genome-wide in ALT cells (VA-13, U2OS, SAOS2 and SKLU-1) than in telomerase-positive cancer (MCF7, A549) or normal human cells (MRC5, BJ Fibroblast) (Fig. 1A and 1B). This evidence concerns the gene GPT and cancer.