In the present study, the biological effects of telomeric G4 stabilization by G4Ls has been explored in a pair of ALT-positive osteosarcoma cell lines (U-2 OS/p53WT and Saos-2/p53del) that represent the gold standard for telomerase-negative/ALT-positive cancer cells [21]. The gene discussed is GPT; the disease is osteosarcoma.