Abstract 3387: Comprehensive detection and analysis of mutant-SF3B1 splice pattern

Abstract

Abstract Aberrant alternative splicing is emerging as a frequent and important process in cancer. Splice aberrations are mainly associated with missense mutations within genes encoding splice factors involved in 3′-splice site recognition. SF3B1, U2AF1, SRSF2 and ZRSR2 are the most frequently mutated genes encoding splicing factors in tumors. Interestingly, these mutations are mutually exclusive and each leads to a distinct aberrant splice pattern. Based on RNA-seq analyses of 74 primary tumors of uveal melanoma, we previously defined the aberrant splice pattern of SF3B1 hotspot mutations. In order to further characterize the catalogue of pathogenic mutations in SF3B1 that induce the aberrant splice pattern, we used a Sequence Bloom Tree (SBT) constructed from RNA-seq data for a total of 11,350 different tumors from the TCGA (Collaborative project with Seven Bridges Cancer Genome Cloud) to rapidly screen for samples consistent with the aberrant splice pattern. Based on this analysis, 75 tumors from different tissues of origin presented with the mutant-SF3B1 pattern, including 70 tumors harboring SF3B1 mutations: 48 cases of the hotspot mutations (21 tumors with SF3B1R625, 6 with SF3B1K666 and 21 with SF3B1K700) and 22 cases harbored non-hotspot SF3B1 mutations. No mutation or deletion in SF3B1 was detected in 5 tumors. Taking into account that the threshold of scores defining the significant presence of the aberrant splice pattern varies between tumor types, we proceeded to an in cellulo validation of a set of newly described mutations of SF3B1 and confirmed the induction of the aberrant splice pattern. Overall, our study highlights the potential of splice patterns as a biomarker in absence of detectable splice related mutations and sheds light on an efficient, large-scale computational approach to screen clinical cases for splice patterns. Citation Format: Samar Alsafadi, Dorine Bellanger, Michele Cornella, Erik Lehnert, Sergio Roman-Roman, Marc-Henri Stern, Tatiana Popova. Comprehensive detection and analysis of mutant-SF3B1 splice pattern [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 3387.