The analysis of BRAF fusions in Chinese patients with glioma.

Abstract

e14031 Background: KIAA1549-BRAF fusion is the most common genetic event in pilocytic astrocytoma (PA), and leads to activation of the mitogen activated protein kinase (MAPK) signaling pathway. KIAA1549-BRAF fusion has been considered to be a key variant of PA in WHO CNS5, however, fusions of BRAF with other partner genes leading to MAPK pathway activation, have been described rarely. Herein, we explore BRAF fusions profiles in Chinese glioma patients. Methods: Next generation sequencing of 131-gene profiling was performed to analyze BRAF fusions from 1955 Chinese brain tumor patients in 2019-2021. BRAF fusions were detected by following the standard operating procedure (SOP). We screened out the BRAF fusions, and calculated the mutation frequency and other rare BRAF gene fusions. Results: A total of 49 cases were detected with BRAF fusions, 36 cases were children (< 18 years old), and 13 cases were adults, with a mean age of 13 years (0-57 years). Interestingly, 39(80%) of them were KIAA1549-BRAF fusions, the most common fusion is between KIAA1549 exon 16 and BRAF exon 9 (exon 16–exon 9) followed by (exon 15–exon 9) and (exon 16–exon 11). And the other ten were rare fusions, including DENND2A-BRAF, MRPS33(Intergenic)- BRAF, BCAS1- BRAF, TMEM176B-BRAF, RNF130-BRAF, RIN2-BRAF, GNAI1-BRAF, EXOC4-BRAF, TNK2-BRAF. Most retained BRAF exons 9–18 (7/10, 70%). There was a significant statistical difference in age that the non- KIAA1549-BRAF fusions group was higher than the KIAA1549-BRAF fusions group (25 vs. 10, p < 0.005). Importantly, we identified new BRAF fusion variants resulting in RIN2-BRAF, EXOC4-BRAF, TNK2-BRAF and TMEM176B-BRAF rearrangements, which has not previously been reported in gliomas. Conclusions: We find new BRAF fusions in our 20% glioma patients. In addition, analysis of rare BRAF fusion may help guide diagnosis and develop potential targeted therapies of older PA.