Abstract 4278: Somatic MAPK pathway mutations are associated with high mutational burden and good survival in head and neck squamous cell carcinoma (HNSCC)

Abstract

Abstract Somatic mutations of the MAPK pathway occur in ~14% of head and neck squamous cell carcinoma (HNSCC; TCGA Provisional; www.cbioportal.org). Notably, mutations found in MAPK signaling components are apparent hotspot or activating mutations, potentially driving activation of the MAPK pathway. These mutations include HRAS p.G12V/D/A/C/S & p.G13V/R, MAPK1 p.E322K/*, BRAF p.D594N & p.V600E mutations. We found that this MAPK pathway mutated subset of HNSCC tumors have a higher mutational burden than MAPK-wildtype (WT) tumors. The average rate of non-synonymous mutations in MAPK pathway mutated tumors is 265.1±42.84 mutation/tumor vs 143.5±5.83 mutation/tumor in WT tumors in the TCGA cohort (P=0.0005). MAPK pathway mutations are not associated with HPV positivity (P=0.5815). Subsequent analysis shows that this subset of MAPK pathway-mutated tumors is unexpectedly associated with TP53 wildtype status (P=0.005584), as well as CASP8 mutations [29.3%; 27/92 cases vs. a 6.5% rate (27/418 cases) in the MAPK pathway WT group; P=9.91 x10-9]. Based on the current survival data of the TCGA Provisional cohort, it appears that patients whose tumors bearing HRAS, BRAF, MAPK1, MAP2K1, and RPS6KA1 mutations have a long median survival of 7.94 years (95.3 months; P=0.0165) vs. patients without these somatic mutations. Though TP53 WT status is a well-recognized biomarker for good prognosis in HNSCC, it only predicts with a median survival of ~45.8 months in this very same cohort. Thus, our findings suggest that MAPK pathway mutations may serve as potential genomic biomarkers for good prognosis in HNSCC. Recently, both HRAS and MAPK1 hotspot mutations have been shown to serve as potential neo-antigens in cervical cancer. Further investigation is needed to determine if these somatic MAPK pathway mutations are capable of mounting an anti-cancer immunity (via hotspot neo-antigens or neo-antigens due to higher mutational burden per se) in these patients, which may contribute to their improved survival. Acknowledgements: VWYL received funding supports from the Research Grant Council, Hong Kong (General Research Fund: #1711484, #17121616; Theme-based Research: T12-401/13-R) and the Hong Kong Cancer Fund, Hong Kong. Citation Format: Hoi-Lam Ngan, Andrew Y. Fong, Sharon Chan, Shing Chun Yu, Laura R. H. Ip, Jennifer R. Grandis, Vivian Lui. Somatic MAPK pathway mutations are associated with high mutational burden and good survival in head and neck squamous cell carcinoma (HNSCC) [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 4278.