In both cell lines, 30% of isogenic SMARCAL1−/− clones isolated exhibited significantly increased levels of C-circles (Fig. 5b), as well as rare ultrabright telomere foci and APBs (Fig. 5c), indicating that loss of SMARCAL1 in GBM cells can induce signs of ALT. This evidence concerns the gene SMARCAL1 and glioblastoma.