Abstract 3142: Whole genome sequencing of oligodendrogliomas identifies genes mutated at a low frequency that contribute to tumor formation.

Abstract

Background: Causal genetic changes in oligodendrogliomas (OD) with 1p/19q codeletion include mutations in IDH1, IDH2, CIC and FUBP1. Here, we have performed whole genome sequencing on three ODs to determine whether additional genetic changes contribute to tumor formation.

Methods: We performed whole genome sequencing of DNA from 3 ODs grade III with 1p/19q codeletion and matched germline DNA. Targeted resequencing of identified genes was performed in an additional 32 ODs with 1p19q LOH (28/32) or partial loss of 1p (2/32), 19q (2/32). All mutations were validated by Sanger sequencing. Constructs of wildtype and mutated genes were subsequently generated (n=13), fused to GFP for visualization. Established cell lines were created to perform functional analysis.

Results: Whole genome sequencing identified a total of 55 mutations in coding exons (range 8-32 mutations per tumor), including the known molecular abnormalities in IDH1 (2/3), IDH2 (1/3), CIC (2/3) and FUBP1 (1/3). Mutations in the ATRX gene were not identified. In addition to these known genes, we identified mutations in additional genes, most of which were previously not implicated in ODs. We first examined the mutation frequency of these genes in an additional 32 tumors. No additional mutations were identified. We then performed functional analysis on a subset of these mutations. For ZNF238, we observed a difference in the sub cellular localization between wildtype and mutant contructs; the wildtype protein localized to the nucleus while the mutant protein is present in the cytoplasm. In addition, stably transfected ZNF238 mutant cell line shows increased proliferation compared to wildtype.

Conclusion: Our results confirm that mutations in IDH, CIC and FUBP1 are present at high frequency in oligodendrogliomas with 1p/19q loss. Functional analysis of infrequently mutated genes provide evidence that they contribute to oncogenesis.

Citation Format: Lale Erdem-Eraslan, Maurice de Wit, Daphne Heijsman, Andreas Kremer, Peter J. van der Spek, Peter A.E. Sillevis Smitt, Pim J. French. Whole genome sequencing of oligodendrogliomas identifies genes mutated at a low frequency that contribute to tumor formation. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 3142. doi:10.1158/1538-7445.AM2013-3142