KIAA1549-BRAF Fusionindependent RSK1 over Expression in Pilocytic Astrocytoma - Abstract
BRAF is the most frequently altered gene in pediatric low grade glioma (pLGG), primarily in the most common pLGG – the pilocytic astrocytoma (PA) harboring a tandem duplication on chromosome 7q34 which results in the KIAA1549 – BRAF fusion gene. The rates of BRAF fusion are depending on tumor location in the CNS and the prognostic effects of this fusion are variable. BRAF fusion proteins result in aberrant activation of the MAP-Kinase (MAPK) pathway, downstream of which the p90 Ribosomal S6 kinase (RSK) is located, known to be important for regulation of gene expression and protein synthesis. However, RSK genes activity, and their relation to the major molecular event in PA pathogenesis – the KIAA1549-BRAF genes fusion has never been investigated. Fifty patients with a total number of 73 tumor samples were included in the study: 52 formalin-fixed paraffin-embedded (FFPE) and 21 corresponding fresh frozen (FF) tumor samples of various pLGG and high-grade glioma (HGG). q-PCR and RT-PCR were performed in order to quantify RSK expression and the presence of BRAFfusion gene, respectively. PCR products were subjected to gel electrophoresis and Sanger sequencing. Immunohistochemistry and Western Blotting were performed for RSK proteins investigation. Interestingly, RSK1 expression was 3.485 times increased in PAs compared to normal tissue. The change in RSK1 expression had no correlation with the status of KIAA1549-BRAF fusion presence.