Abstract 1990: Unique in vitro transcriptional activities of oncogenic Myb fusions identified in salivary gland adenoid cystic carcinoma

Abstract

Abstract Chromosomal translocations involving the MYB and NFIB (t(6;9)) genes are the sole recurrent cytogenetic aberration in Adenoid Cystic Carcinoma (ACC), a rare cancer that frequently manifests as salivary gland tumors. Since ACC has poor prognosis and treatment is accompanied by high morbidity, there is a need for additional investigation of this cancer with the goal of improving patient outcomes. Recurrent translocations create fusions involving the N-terminus of MYB, located on chromosome 6, and the C-terminus of NFIB, located on chromosome 9. Our lab also recently identified translocations involving the related MYBL1 gene fusing it to NFIB t(8;9) and RAD51B t(8;14) genes. Further, recent work in our lab demonstrated tumors with MYB or MYBL1 translocations have similar gene expression (1). The presence of recurrent translocations involving both the MYB proto-oncogene and the related MYBL1 gene suggests that the resulting novel fusion proteins are likely oncogenic drivers in these tumors. In order to directly address the transcriptional activities of the resulting fusion proteins MYB and MYBL1 fusion genes, identified in primary ACC tumors, were cloned and expressed in vitro. The fusion proteins transcriptional activities were examined using reporter gene assays and trancriptomics. Chromatin immunoprecipitation followed by sequencing (ChIP-seq) was performed to interrogate promoters bound by these proteins. Reporter genes specific for normal vs. oncogenic MYB variants have been constructed. These data demonstrate that the proteins predicted to be produced by MYB fusion genes after chromosomal translocation are transcriptionally active. Further, Myb fusion proteins bind and activate gene sets distinct from their wild type c-Myb and A-Myb counterparts. These data indicate Myb fusion proteins have unique transcriptional activities, perhaps underlying their ability to drive tumorigensis in ACC. 1. Brayer et al. Recurrent Fusions in MYB and MYBL1 Define a Common, Transcription Factor-Driven Oncogenic Pathway in Salivary Gland Adenoid Cystic Carcinoma. Cancer Discovery. In press. Citation Format: Candace A. Frerich, Scott A. Ness. Unique in vitro transcriptional activities of oncogenic Myb fusions identified in salivary gland adenoid cystic carcinoma. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 1990.