Abstract 5472: Role of Harvey Ras (HRAS) mutations in head and neck squamous cell carcinoma (HNSCC)

Abstract

Abstract Background: Harvey Ras (HRAS) was recently reported being mutated in head and neck squamous cell carcinomas (HNSCC) and likely plays an important role as an oncogene. The precise role of HRAS mutations for signaling and carcinogenesis of HNSCC remains to be determined. Methods: We completed mutational screening (Sanger Sequencing) for tissues and cell lines focused on the known hotspot mutations G12X and Q61X. Furthermore we performed viability testing for various cell lines and visualized the signaling-effects by itself, in presence of PI3K-, EGFR inhibitors and likewise in combination, by immunoblotting. After suppression of HRAS using siRNA, we determined the cell-viability. Results: In our study we sequenced 100 HNSCC tumor tissues and HNSCC cell lines and identified several canonical HRAS mutations. One cell line contained a G12D HRAS mutation and was further examined. Additional two cell lines with atypical HRAS variants were identified and compared to the classic hotspot mutated cell line. The viability for the mentioned cell lines were indicative of resistance to EGFR inhibition to different degrees. The protein activation levels in important signaling pathways (PI3K/MAPK) confirmed our viability data. HRAS signaling was primarily via PI3K/AKT. Silencing HRAS showed significantly decreased viability. Conclusions: Previous studies have shown that EGFR-targeting agents remain insufficient as single targeted therapy. HRAS appears to contribute to the EGFR-resistance of HNSCC. The canonical mutation G12D appears to signal primarily via PI3K and PI3K inhibitors may be effective. The G12D cell line model indicates a central role of mutated HRAS for signaling and viability consistent with role as a driver mutation. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 5472. doi:1538-7445.AM2012-5472