Abstract 1743: Comprehensive genomic characterization of a large cohort of platinum-sensitive, high-grade serous ovarian cancer (HGSOC) FFPE specimens
Authors: Haynes Brian C. , Fahey Marie E. , Myers Darcy , Ilsley Diane , Latham Gary J. , Somers Elizabeth B. , Nicolaides Nicholas C. , Schweizer Charles , O’Shannessy Daniel J. 
Published: July 2017

Introduction: Ovarian cancer is a leading cause of cancer related death in women. A comprehensive genomic characterization of platinum-sensitive tumors is required to further refine the definition of molecular subtypes and identify targeted therapies for this patient population. To this end we have performed a large-scale genomic and transcriptomic characterization of 348 primary FFPE tissues from a cohort of platinum-sensitive HGSOC patients collected from multiple clinical sites.

Methods: Macrodissection of FFPE resected tumor slides or sectioned blocks was performed to enrich for tumor content. RNA and DNA were each isolated from 2x 5µm sections of FFPE material. RNA expression and gene fusions were profiled by whole transcriptome RNA-Seq. DNA variants were analyzed by the AmpliSeq™ Cancer Hotspot Panel (Thermo Fisher). A subset of tumor and matched germline (PBL) specimens (N=181) were assessed for TP53 mutations by the QuantideX® NGS TP53 Assay (Asuragen, Inc.). CNV analysis of FFPE tumor DNA was performed using the OncoScan® FFPE Assay Kit (Affymetrix) and microsatellite instability was characterized by comparing matched tumor and PBL specimens with capillary electrophoresis using the Bethesda panel. Germline BRCA1/2 mutation status was determined by profiling PBL specimens with a custom AmpliSeq™ NGS panel.

Results: The spectrum of DNA mutations and CNVs was consistent with other HGSOC cohorts with mutations in TP53 present in the majority of specimens (87% for specimens with full exon coverage of TP53). Germline mutations in BRCA1 and BRCA2 were identified at 10.3% and 6.8% respectively. Analysis of recurrent whole chromosomal arm gain and loss displayed a striking agreement with the TCGA HGSOC cohort. Unsupervised analysis of the RNA-Seq expression data through non-negative matrix factorization revealed 4 distinct transcriptional subtypes, corresponding to the 4 established CLOVAR subtypes: differentiated, immunoreactive, mesenchymal and proliferative. Patients classified as mesenchymal had the poorest prognosis. Further integrative analysis identified additional associations between the CLOVAR subtypes and other molecular indications.

Conclusions: Through integrative genomic analyses on this challenging set of clinical specimens we have reproduced and refined the molecular subtypes of platinum-sensitive HGSOC and highlighted alterations that may lead to improved diagnostic and precision medicine strategies. In contrast to previous large-scale molecular characterization efforts such as TCGA where fresh-frozen tissues were collected under highly controlled settings, this study is based on molecular profiling of FFPE tissues collected at dozens of clinical sites. Thus, our study serves as a model for future molecular characterization efforts of FFPE specimens collected in real-world clinical settings.

Citation Format: Brian C. Haynes, Marie E. Fahey, Darcy Myers, Diane Ilsley, Gary J. Latham, Elizabeth B. Somers, Nicholas C. Nicolaides, Charles Schweizer, Daniel J. O’Shannessy. Comprehensive genomic characterization of a large cohort of platinum-sensitive, high-grade serous ovarian cancer (HGSOC) FFPE specimens [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 1743. doi:10.1158/1538-7445.AM2017-1743