GPT and osteosarcoma: This observation may however not be generalized to all ALT+ cell lines as the study by Lauvrak et al [20] reported efficient tumor formation in NSG mice injected with other ALT+ osteosarcoma cell lines, including CAL-72, ZK-58, KPD or G-292, although, here too, conflicting results were observed as the ZK-58 and KPD cell lines failed to develop tumors in nude mice [19].