The novel, recurrent mutation in the TOP2A gene results in the enhanced topoisomerase activity and transcription deregulation in glioblastoma

Background: High grade gliomas (HGGs) are aggressive, primary brain tumors with poor clinical outcomes. We aim to better understand glioma pathobiology and find potential therapeutic susceptibilities. Methods: We designed a custom panel of 664 cancer- and epigenetics related genes, and employed targeted next generation sequencing to study the genomic landscape of somatic and germline variants in 182 gliomas of different malignancy grades. mRNA sequencing was performed to detect transcriptomic abnormalities. Results: In addition to known alterations in TP53, IDH1, ATRX, EGFR genes found in this cohort, we identified a novel, recurrent mutation in the TOP2A gene coding for Topoisomerase 2A occurring only in glioblastomas (GBM, WHO grade IV gliomas). Biochemical assays with recombinant proteins demonstrated stronger DNA binding and DNA supercoil relaxation activities of the variant proteins. GBM patients carrying the mutated TOP2A had shorter overall survival than those with the wild type TOP2A. Computational analyses of transcriptomic data showed that GBMs with the mutated TOP2A have different transcriptomic patterns suggesting higher transcriptomic activity. Conclusion: We identified a novel TOP2A E948Q variant that strongly binds to DNA and is more active than the wild type protein. Our findings suggest that the discovered TOP2A variant is gain of function mutation.