Molecular and clinicopathological implications of PRAME expression in adult glioma

Background PRAME (PReferentially expressed Antigen in MElanoma) is a biomarker studied in various human cancers. Little is known about the biological implications of PRAME in glioma. We aimed to perform a comprehensive analysis to explore PRAME gene expression and its biological and clinicopathological significance in gliomas. Methods and materials We accessed the human cancer atlas (TCGA) database to collect glioma patients (n = 668) with primary tumors and gene expression data. Single nucleotide variants, copy number variation, DNA methylation data, and other clinicopathological factors were also extracted for the analysis. Results Overall, 170, 484, and 14 tumors showed no expression, low expression (FPKM <= 1), and overexpression (FPKM>1) of the PRAME gene, respectively. The principal component analysis and pathway analyses showed that PRAME-positive gliomas (n = 498), which consisted of tumors with PRAME low expression and overexpression, expressed different oncogenic profiles, possessing higher activity of Hedgehog, P3IK-AKT-mTOR, and Wnt/beta-catenin pathways (p<0.001). DNA methylation analysis also illustrated that PRAME-positive tumors were distributed more densely within a grade 4-related cluster (p<0.001). PRAME positivity was an independent prognostic factor for poor outcomes in a multivariate cox analysis adjusted for clinical characteristics and genetic events. Kaplan-Meier analysis stratified by revised classification showed that PRAME positivity was solely associated with IDH-wildtype glioblastoma, grade 4. Finally, PRAME-overexpressing cases (n = 14) had the worst clinical outcome compared to the PRAME-negative and PRAME-low cohorts (adjusted p<0.001) in pairwise comparisons. Conclusion PRAME expression statuses may dictate different biological and clinicopathological profiles in IDH-wildtype glioblastoma.