Abstract 129: Integrated genomic analysis of survival outliers in glioblastoma

Abstract

Abstract Despite the general poor prognosis for patients with GBM, a proportion survives well beyond the median survival of 12-14 months following diagnosis. To elucidate molecular features associated with disproportionately protracted survival, we conducted deep genomic comparative analysis of a cohort of patients receiving standard therapy (surgery plus concurrent radiation and temozolomide) wherein “GBM outliers” were identified: patients who responded (long-term survivor, LTS) versus those who failed rapidly (short-term survivor, STS). The datasets enabled interrogation for signatures indicative of tumor vulnerability. Whole genomic, transcriptomic and epigenetic analyses of 18 patients, including 8 LTS with an average 30 months overall survival (OS) and 10 STS with an average of 7 months OS were performed to capture single nucleotide variants (SNVs), indels, translocations, intra-chromosomal rearrangements, copy number variants, along with DNA methylation and mRNA expression. LTS and STS cases showed equal proportion of 7p11.2 (EGFR) amplification and 9p21.3 (CDKN2A) deletion. However, LTS GBM showed frequent chromosomal gains in 4q12 (PDGFRA and KIT) and 12q14.1 (CDK4) and deletion in 19q13.33 (BAX, BCAT2 and CD33), whereas, STS GBM showed frequent deletion in 9p11.2 (FOXD4L2 and AQP7P3) and 22q11.21 (HIC2). In addition, LTS GBM showed a 2-fold increased copy number alteration (specifically deletion) as compared to STS GBM. By gene expression analysis, supervised clustering using the CIN70 signature (prognostic) showed an increased expression in STS GBM. Overall, whole genome methylation analyses showed that STS GBM tumors harbor more hypomethylation in probes situated in -200 bp of transcription start site (TSS) and both exon 1 and 5’UTR region. A methylation signature consist of 89 probes distantly separate LTS from STS GBM tumors. We posit that genomic instability (broadly inclusive) is associated with vulnerability of GBM to standard therapy; conversely, genomic instability coupled with genetic and epigenetic signatures may identify patients where up-front entry into alternative, targeted regimens would be a preferred, more-efficacious management. Supported by a grant from the Ben & Catherine Ivy Foundation. Citation Format: Sen Peng, Harshil Dhurv, Brock Armstrong, Jeffrey Kiefer, Bodour Salhia, Julianna Ross, Christophe Legendre, Selene Virk, Andrew E. Sloan, Quinn T. Ostrom, Jill Barnholtz-Sloan, Nhan L. Tran, Michael E. Berens. Integrated genomic analysis of survival outliers in glioblastoma. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 129.