GPT and osteosarcoma: In conclusion, the present work indicates that, despite its efficacy to inhibit cell growth, the G4-ligand RHPS4 is able to stimulate telomeric recombination and c-circles formation through the induction of telomeric replicative stress, telomeric DNA damage, and APBs formation in U2OS and SAOS-2 ALT osteosarcoma cells.