Abstract P170: SpliceCore® a platform for identifying aberrant alternative splicing in triple negative breast cancer for novel therapeutic development
Authors: Manzanares Miguel A. , Priyanka Dhingra , Anderson Kendall , Frederick Vanessa , Geier Adam , Casill Alyssa , Akerman Martin , Arun Gayatri 
Published: December 2021

Abstract
Splicing dysregulation is a major hallmark of cancer, affecting tumor progression, metastasis, and therapy resistance. Multiple studies have demonstrated the oncogenic activity of specific cis splicing errors and trans-acting splicing factor misregulation in patient tumors. As such, cancer-associated splicing dysregulation is a novel source of clinically actionable biomarkers and therapeutic targets, particularly for treatment insensitive cancers such as TNBC. Envisagenics has developed SpliceCore, an innovative cloud-based software platform that integrates machine learning (ML) algorithms with high performance computing to analyze large RNA-seq datasets to predict biologically relevant, novel, and highly prevalent tumor specific alternative splicing (AS) changes. Using SpliceCore, we have analyzed &gt;2500 RNAseq samples from different breast cancer subtypes as well as normal breast tissue and identified several AS targets with a potential to translate into therapeutic candidates for TNBC. Here, we will discuss one of our most promising AS targets; it is present in 60.5% of TNBC patients and correlates with poor overall survival. Using SpliceCore, we predicted and designed an optimal set of splice switching oligos (SSO) that can efficiently switch the skipping isoform to an inclusion isoform in TNBC cells. Detailed mechanism of action studies of isoform switching by SSO-0205 have demonstrated the critical role of the isoform in a TGFβ dependent tumor progression mechanism. Pretreatment of the TNBC cells with SSO-0205 24 hours before TGFβ pathway activation reversed the cell proliferative response associated with it. This resulted in a strong inhibition of p21 gene expression, accompanied by a 50% decrease on the number of cells in G2, the mitotic phase of the cell cycle, and 40% decrease on cell viability. Additionally, migratory response induced by TGFβ in TNBC cells was also significantly inhibited by SSO-0205 pretreatment, which downregulated ANGPTL4 gene expression followed by a 55% decrease in cell migration. Together, we provide experimental proof of concept to demonstrate SpliceCore’s ability to discover novel disease specific AS targets and design splice correcting oligonucleotides for subsequent correction and therapeutic development. Using this approach, we were able to uncover a novel therapeutic target for TNBC, whose aberrant splicing contributes to TNBC pathogenesis by promoting an overactivation of the TGFβ pathway. Reversal of this aberrant TNBC specific splicing using SSOs represent a new and promising therapeutic approach that will have a significant impact on TNBC treatment and clinical care.
Citation Format: Miguel A. Manzanares, Dhingra Priyanka, Kendall Anderson, Vanessa Frederick, Adam Geier, Alyssa Casill, Martin Akerman, Gayatri Arun. SpliceCore® a platform for identifying aberrant alternative splicing in triple negative breast cancer for novel therapeutic development [abstract]. In: Proceedings of the AACR-NCI-EORTC Virtual International Conference on Molecular Targets and Cancer Therapeutics; 2021 Oct 7-10. Philadelphia (PA): AACR; Mol Cancer Ther 2021;20(12 Suppl):Abstract nr P170.