Experiments based on the ablation of approximately 8.1kb long fragment from the 20q subtelomere using the CRISPR-Cas9 method resulted in an almost complete downregulation of TERRA expression in 20q TERRA-KO U2OS osteosarcoma ALT-positive cells, telomere shortening, and the induction of massive DDR. This evidence concerns the gene GPT and osteosarcoma.