GPT and osteosarcoma: A recent study investigated telomerase-positive and ALT-positive osteosarcoma and lung cancer cell lines as well as glioma stem cell lines and reported that cells that employ the ALT pathway are hypersensitive to the inhibition of the protein kinase ataxia telangiectasia- and RAD3-related protein (ATR), one of the two main DNA damage checkpoint-activating kinases in human cells (3).