Abstract 3437: Whole genome and transcriptome sequencing of a pan cancer cohort unearths novel therapeutic avenues

Abstract

Whole genome sequencing (WGS) has emerged as a tool to characterize the entire genomic landscape of cancer and capture potential new targets and predictive biomarkers. Using state-of-the-art whole-genome and transcriptome sequencing (WGTS) analysis we interrogated a pan cancer cohort to nominate new treatment options. WGS was performed on 414 tumor/germline pairs from our pan cancer cohort of 355 patients, of which 103 had results of other commercial NGS assays. RNAseq data was available in 96 samples. We employed the Isabl GxT analytic platform and manually curated single base substitution (COSMIC v3) mutational signatures and structural variants (SVs). WGTS results were correlated with available clinico-pathologic data. High throughput drug screening that included PARP inhibitors and functional validation were performed in 61 matched patient-derived tumor organoids (PDTO). We found 5,129 SVs affecting at least one cancer gene in 88% of cases. High-confidence homologous recombination deficiency (HRD), determined by curation of mutational signatures and mutations/SVs affecting oncogenes and tumor suppressor genes, was detected in 8.3% of solid tumors (e.g., prostate, pancreas, ovarian, uterine, breast, gallbladder, and stomach carcinomas). HRD status included tumors with BRCA1/2 wildtype and SVs impacting BRCA1/2, RAD51, ATM and other HRD genes. CDK12-loss associated genomic instability was detected in 7 cases including 3 cases of prostate adenocarcinoma. 93 gene fusions involving cancer genes were detected including known and novel fusions of potential significance (e.g., SLC45A3::ALK in metastatic prostate adenocarcinoma, TMEM106A::BRCA1 in serious ovarian carcinoma, ESR1::EP300 in metastatic breast cancer). Some tumor cohorts demonstrated enrichment of drivers e.g., FGFR1 amplification in male breast cancer, rearrangements at the TERT locus in adrenocortical carcinoma, enrichment for repeat-mediated deletion attributed to mismatch repair (MMR) in gynecological carcinosarcoma, and SVs affecting FHIT in gastric adenocarcinoma. Drug screening of PDTO and functional testing with RAD51 immunofluorescence assay validated high-confidence HRD annotation. One example is a BRCA1/2 wildtype pancreatic adenocarcinoma with increased tandem duplications and SV (inversion) impacting BRCA2, and high-confidence HRD by our novel WGS classifier. Drug screening of the corresponding PDTO showed an enhanced response to Olaparib, in contrast to cases without HRD that did not. We have used state-of-the-art analysis of WGTS to improve the detection of targets and significant biomarkers in a pan cancer cohort, including HRD, CDK12-type genomic instability, pathogenic germline mutations and potential targetable novel fusions. A robust and clinically relevant ex vivo preclinical model allowed us to validate a WGS-based classifier that detects HRD even in cancers with wildtype BRCA1/2. Citation Format: Majd Al Assaad, Hui-Hsuan Kuo, Jones Nauseef, Max F. Levine, Gunes Gundem, Juan S. Medina-Martínez, Jyothi Manohar, Michael Sigouros, Ahmed Elsaeed, David Wilkes, Elli Papaemmanuil, Eloise Chapman, Scott T. Tagawa, Allyson Ocean, Cora N. Sternberg, Eleni Andreopoulou, Manish Shah, Andrea Sboner, Kevin Holcomb, David Nanus, Laura Martin, Olivier Elemento, Juan Miguel Mosquera. Whole genome and transcriptome sequencing of a pan cancer cohort unearths novel therapeutic avenues [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 3437.

Unearthed Novel Molecular Phenotypes and Potential Therapeutic Targets in Esophagogastric Adenocarcinoma

“…The genomic characteristics of the case with a CDK12::RAB5B fusion are illustrated in Figure 3B. Further, we employed a whole genome-based classifier of HRD (37,38) and identified one case with a high confidence HRD score (>0.50) supported by increased small deletions (1Kb-10Kb) in rearrangement signatures. The tumor sample harbored a BRCA2 p.K503fs*6 somatic biallelic frameshift variant, most likely resulting in the HRD phenotype.…”