Abstract 3644: Novel NOTCH1-ROS1 gene fusion drives distinct molecular mechanisms in a rare pediatric angiosarcoma
Authors: Jain Payal , Iyer Sudarshan , Straka Joshua , Surrey Lea , Pogoriler Jennifer , Smith Tiffany , Busch Christine , Li Marilyn , Fox Elizabeth , Resnick Adam C. , Davare Monika , Waanders Angela J. 
Published: August 2019

Abstract
Angiosarcomas are extremely rare, malignant childhood tumors, which often arise in deep soft tissue and liver as well as exhibit a wide anatomical distribution. Due to the rarity of this diagnosis in pediatrics, the development of novel targeted therapeutic options are limited. Here, we diagnosed a case of pediatric angiosarcoma (pAS), and to identify putative driver genomic aberrations, we performed genomic sequencing via a Comprehensive Next Generation Sequencing Solid Tumor Panel, including RNA-sequencing by anchored multiplex PCR (ArcherDx) for 106 fusion partner genes. We identified a novel NOTCH1-ROS1 gene fusion generated from a rearrangement of chromosomes 9 and 6. Subsequent reverse transcription and Sanger sequencing validated the expression of NOTCH1-ROS1 in the pAs. While both NOTCH1 and ROS1 are established proto-oncogenes, and have been separately involved in gene fusions across diverse cancer types, this is a previously unreported fusion in this rare pediatric cancer. We also identified a germline TP53 p.T123Wfs*12 pathogenic variant on follow-up sequencing, thus revealing Li Fraumeni syndrome in this angiosarcoma patient.Notch1-ROS1 is a novel, uncharacterized fusion protein and its functional oncogenic potential or tumorigenic sufficiency is unknown. We cloned NOTCH1-ROS1 cDNA and generated stably expressing heterologous cell lines to test its oncogenic potential using cellular models of transformation and tumorigenicity. Our analysis revealed that Notch1-ROS1 is a potent oncogene capable of inducing neoplastic transformation in cells, and demonstrated that its expression alone is sufficient for tumor formation in a murine allograft model. Notch1-ROS1 oncogenesis is driven via activation of several downstream pathways through a collaboration between the Notch1 and Ros1 domains. We also tested the efficacy of ROS1-targeted tyrosine kinase inhibitors (TKI) in these model systems; our data show dose-dependent suppression of Notch1-Ros1 driven cellular activity and concurrent inhibition of tumor growth as well as prolonged survival after oral monotherapy.Overall, this study reveals the first known NOTCH1-ROS1 alteration in a case of pAs. Given the extreme rarity of this malignant disease, it is challenging to expand to a larger cohort in a short duration. However, our findings on the mechanistic underpinnings of Notch1-ROS1 provide a deeper understanding of how this novel fusion drives tumor growth. Furthermore, drug-targeting studies provide requisite preclinical evidence for the possibility of utilizing ROS1-TKI in pA patients harboring this or other ROS1-fusions. Overall, these data suggest that ongoing genomic profiling of these rare tumors may reveal actionable drivers and holds the promise to improve patient outcomes.
Citation Format: Payal Jain, Sudarshan Iyer, Joshua Straka, Lea Surrey, Jennifer Pogoriler, Tiffany Smith, Christine Busch, Marilyn Li, Elizabeth Fox, Adam C. Resnick, Monika Davare, Angela J. Waanders. Novel NOTCH1-ROS1 gene fusion drives distinct molecular mechanisms in a rare pediatric angiosarcoma [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 3644.