Abstract IA09: Comprehensive genomic characterization of head and neck squamous cell carcinomas

Abstract

Abstract Large and comprehensive genomic analyses of head and neck squamous cell carcinomas (HNSCC) are greatly increasing our understanding of the heterogeneity of this disease and identifying the key genomic changes that drive these tumors. HNSCC tumors associated with HPV are distinct from HNSCC disease linked to tobacco exposure (HPV-positive versus HPV-negative). HPV- tumors are characterized by: 1) amplification of receptor tyrosine kinases (RTK); 2) genomic loss of TP53 and loss of CKDN2A/RB1 by a variety of mechanisms including truncating mutation, deletion, and/or alternative splicing; 3) amplification of CCND1/CDK4/CDK6; 4) activation of NFE2L2/KEAP1/CUL3; and 5) loss of NOTCH1/FAT1/AJUBA. In contrast, HPV-positive HNSCCs harbor: 1) RTK amplification; 2) FGFR2/3 mutations and/or FGFR3-TACC3 fusions; 3) CDKN2A loss; and 4) E2F1 amplification. Interestingly, activating mutations in the PIK3CA oncogene are found in approximately one third of HPV-negative HNSCC and in over fifty percent of HPV-positive tumors. Mutually exclusive mutations in RAS family genes, specifically RHOA, KRAS, and HRAS, are present but infrequently found in HNSCC (6% of TCGA cases). Amplification of chromosome 3q, a region containing the TP63, SOX2, and PIK3CA genes, is seen in the majority of both HPV-negative and HPV-positive HNSCC. HPV-negative HNSCCs demonstrate clear evidence of molecular heterogeneity, as demonstrated by expression profiling studies indicating diverse biologic subclasses within HPV-negative disease, including a class of tumors without EGFR amplification and/or overexpression, previously termed “atypical” HNSCCs, which consist of approximately 20% of HPV-negative cases and the majority of HPV-positive HNSCCs. An intriguing mutational pattern identified by TCGA was a subset of HPV-negative HNSCC originating in the oral cavity with few to no copy-number alterations statistically enriched for HRAS, CASP8, and PIK3CA mutations and lack of TP53 mutation. With increasing genetic profiling of HNSCC cell lines and patient-derived xenografts, there is increasing opportunity to rationally select preclinical models to test specific precision medicine hypotheses. Citation Format: Jennifer R. Grandis. Comprehensive genomic characterization of head and neck squamous cell carcinomas [abstract]. In: Proceedings of the AACR-AHNS Head and Neck Cancer Conference: Optimizing Survival and Quality of Life through Basic, Clinical, and Translational Research; April 23-25, 2017; San Diego, CA. Philadelphia (PA): AACR; Clin Cancer Res 2017;23(23_Suppl):Abstract nr IA09.