Incidence of kiaa1549-braf fusion gene in Egyptian pediatric low grade glioma

Background: Low grade gliomas are the most common brain tumor in children. Tandem duplication involving the KIAA1549 and the BRAF kinase genes results in a gene fusion that has been recently characterized in a subset of low grade glioma While there is no clear evidence that the KIAA1549-BRAF gene fusion has an effect on prognosis, it is an attractive target for therapy development and as a diagnostic tool.

Methods: In the current study we examine the prevalence of KIAA1549-BRAF gene fusion in pediatric patients diagnosed with low grade glioma in the Egyptian population and its relationship to clinical and histological subtypes. Sixty patients between the ages of 1 to 18 years were analyzed for the presence of KIAA1549-BRAF fusion gene products using reverse transcription-PCR and sequencing. The clinicopathologic tumor characteristics were then analyzed in relation to the different fusion genes.

Results: KIAA1549-BRAF fusion genes were detected in 56.6% of patients. They were primarily associated with pilocytic astrocytoma (74.2%) and pilomyxoid astrocytoma (60%). Translocation 15-9 was the most common, representing (55.8%) of all positive samples followed by 16-9 (26.4%) and 16-11 (8.8%). Pilocytic astrocytomas presented primarily with 15-9 (32.2%), 16-9 (25.8%) and 16-11 (6.4%) while pilomyxoid astrocytomas presented with 15-9 (46.6%), 16-9 (6.6%) and 16-11 (6.6%) translocations.

Conclusion: Gene fusion is found to be significantly increased in cerebellar pilocytic astrocytoma tumors. Furthermore, 15-9 was found to have a higher incidence among our cohort compared to previous studies. While most of the gene fusion positive pilomyxoid astrocytomas were 15-9, we find the association none significant.