RHPS4-mediated inhibition of cell proliferation was also observed in ALT-positive cell lines such as GM847DM SV40-immortalized human skin fibroblasts and SAOS-2 osteosarcoma in different experimental settings [24,34] and, in general, the efficacy of telomeric G4 ligands in ALT cells is associated to the interference of G4 structures with telomere recombination [35,36] even if no direct evidence is available in the literature. Here, GPT is linked to osteosarcoma.