ALT in Pediatric High-Grade Gliomas Can Occur without ATRX Mutation and is Enriched in Patients with Pathogenic Germline MMR Variants

alexandrossfakianakis shared this article with you from Inoreader ALT in Pediatric High-Grade Gliomas Can Occur without ATRX Mutation and is Enriched in Patients with Pathogenic Germline MMR Variants via Neuro-Oncology Advance Access Abstract Background To achieve replicative immortality, most cancers develop a telomere maintenance mechanism, such as reactivation of telomerase or alternative lengthening of telomeres (ALT). There are limited data on the prevalence and clinical significance of ALT in pediatric brain tumors, and ALT-directed therapy is not available. Methods We performed C-circle analysis (CCA) on 579 pediatric brain tumors that had corresponding tumor/normal whole genome sequencing through the Open Pediatric Brain Tumor Atlas (OpenPBTA). We detected ALT in 6.9% (n=40/579) of these tumors and completed additional validation by ultrabright telomeric foci in situ on a subset of these tumors. We used CCA to validate TelomereHunter for computational prediction of ALT status and focus subsequent analyses on pediatric high-grade glioma (pHGG) Finally, we examined whether ALT is a ssociated with recurrent somatic or germline alterations. Results ALT is common in pHGG (n=24/63, 38.1%), but occurs infrequently in other pediatric brain tumors (<3%). Somatic ATRX mutations occur in 50% of ALT+ pHGG and in 30% of ALT- pHGG. Rare pathogenic germline variants in mismatch repair (MMR) genes are significantly associated with an increased occurrence of ALT. Conclusions We demonstrate that ATRX is mutated in only a subset of ALT+ pHGG, suggesting other mechanisms of ATRX loss of function or alterations in other genes may be associated with the development of ALT in these patients. We show that germline variants in MMR are associated with development of ALT in patients with pHGG. View on Web

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