Primary mismatch repair deficient IDH-mutant astrocytoma (PMMRDIA) is a distinct type with a poor prognosis.

Abstract

Diffuse IDH-mutant astrocytoma mostly occurs in adults and carries a favorable prognosis compared to IDH-wildtype malignant gliomas. Acquired mismatch repair deficiency is known to occur in recurrent IDH-mutant gliomas as resistance mechanism towards alkylating chemotherapy. In this multi-institutional study, we report a novel epigenetic group of 32 IDH-mutant gliomas with proven or suspected hereditary mismatch repair deficiency. None of the tumors exhibited a combined 1p/19q deletion. These primary mismatch repair-deficient IDH-mutant astrocytomas (PMMRDIA) were histologically high-grade and were mainly found in children, adolescents and young adults (median age 14 years). Mismatch repair deficiency syndromes (Lynch or Constitutional Mismatch Repair Deficiency Syndrom (CMMRD)) were clinically diagnosed and/or germline mutations in DNA mismatch repair genes (MLH1, MSH6, MSH2) were found in all cases, except one case with a family and personal history of colon cancer and another case with MSH6-deficiency available only as recurrent tumor. Loss of at least one of the mismatch repair proteins was detected via immunohistochemistry in all, but one case analyzed. Tumors displayed a hypermutant genotype and microsatellite instability was present in more than half of the sequenced cases. Integrated somatic mutational and chromosomal copy number analyses showed frequent inactivation of TP53, RB1 and activation of RTK/PI3K/AKT pathways. In contrast to the majority of IDH-mutant gliomas, more than 60% of the samples in our cohort presented with an unmethylated MGMT promoter. While the rate of immuno-histochemical ATRX loss was reduced, variants of unknown significance were more frequently detected possibly indicating a higher frequency of ATRX inactivation by protein malfunction. Compared to reference cohorts of other IDH-mutant gliomas, primary mismatch repair-deficient IDH-mutant astrocytomas have by far the worst clinical outcome with a median survival of only 15 months irrespective of histological or molecular features. The findings reveal a so far unknown entity of IDH-mutant astrocytoma with high prognostic relevance. Diagnosis can be established by aligning with the characteristic DNA methylation profile, by DNA-sequencing-based proof of mismatch repair deficiency or immunohistochemically demonstrating loss-of-mismatch repair proteins.

• Authors: Abigail K Suwala, Damian Stichel, Daniel Schrimpf, Matthias Kloor, Annika K Wefers, Annekathrin Reinhardt, Sybren L N Maas, Christian P Kratz, Leonille Schweizer, Martin Hasselblatt, Matija Snuderl, Malak Sameer J Abedalthagafi, Zied Abdullaev, Camelia M Monoranu, Markus Bergmann, Arnulf Pekrun, Christian Freyschlag, Eleonora Aronica, Christof M Kramm, Felix Hinz, Philipp Sievers, Andrey Korshunov, Marcel Kool, Stefan M Pfister, Dominik Sturm, David T W Jones, Wolfgang Wick, Andreas Unterberg, Christian Hartmann, Andrew Dodgshun, Uri Tabori, Pieter Wesseling, Felix Sahm, Andreas von Deimling, David E Reuss
• Journal: Acta neuropathologica (Acta Neuropathol) Vol. 141 Issue 1 Pg. 85-100 (01 2021) ISSN: 1432-0533 [Electronic] Germany
• PMID: 33216206 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• Isocitrate Dehydrogenase
• ATRX protein, human
• X-linked Nuclear Protein

Topics

• Adolescent
• Adult
• Astrocytoma (diagnosis, genetics)
• Brain Neoplasms (diagnosis, genetics)
• Child
• DNA Methylation
• DNA Mismatch Repair (genetics)
• Female
• Gene Dosage
• Gene Expression Regulation, Neoplastic (genetics)
• Humans
• Immunohistochemistry
• Isocitrate Dehydrogenase (genetics)
• Kaplan-Meier Estimate
• Male
• Microsatellite Instability
• Mutation (genetics)
• Neoplasm Recurrence, Local
• Prognosis
• Signal Transduction (genetics)
• Survival Analysis
• X-linked Nuclear Protein (genetics)
• Young Adult