GPT and neoplasm: Since ATRX loss and ALT activation are largely limited to high-grade neoplasms in the context of NF1 loss or inherited NF1 syndrome [10], we evaluated cell lines derived from high-grade neoplasms with NF1 loss, including two sporadic glioblastoma cell lines with NF1 inactivation (U251, SF188), an NF1-associated glioblastoma (JHH-NF1-GBM1), two MPNST cell lines (NF90-8, ST88-14), and an NF1-associated sarcoma line (JHH-CRC65).