Abstract 4228: Integrated drug high-throughput screening and quantitative phosphoproteomics rationalizes combination therapy for mutant KRAS pancreatic cancer
Authors: Capri Joseph , Le Thuc , Radu Caius , Donahue Timothy 
Published: August 2019

Abstract
Pancreatic ductal adenocarcinoma (PDAC) is a highly recalcitrant malignancy for which better therapies are urgently needed. KRAS is the most frequently altered gene in PDAC and it orchestrates a number of effector pathways that ultimately drives PDAC growth and proliferation. The recent development of allele-specific inhibitors of oncogenic KRAS G12C, such as ARS-1620, provides an unprecedented opportunity to explore direct targeting of oncogenic KRAS signaling in PDAC. Nearly 3% PDAC patient harbor KRAS G12C, corresponding to ~1,600 new cases of PDAC/year in the US alone for which currently there are no robust targeted therapies. Even if the inhibitor effectively block KRAS function, compensatory mechanism will probably be triggered to overcome the KRAS-mutant PDAC.To better position the direct mutant KRAS inhibitor, we have developed a platform that includes: a high-throughput screen anchored with ARS-1620 to identify companion inhibitor to further dial down the oncogenic KRAS signaling, quantitative mass spectrometric method to map out the adaptive signaling mechanisms of this combination therapy, and bioinformatics pipeline to reveal and rank targetable kinases that drive the adaptive resistance mechanism. To do so, we will apply our platform on a panel of KRAS G12C primary PDAC models. We will profile the proteomic/phosphoproteomic changes of cells treated with combination therapy to identify adaptive signaling pathways that could be potentially targeted.High-throughput chemical-genomics screening identified receptor tyrosine kinases (RTKs) to be synergistic to the KRAS inhibitor, ARS-1620. In particular, multiple epidermal growth factor receptor (EGFR) inhibitors restrict growth of patient-derived PDAC, XWR200, when combined with ARS-1620. When profiling the proteomic/phosphoproteomics changes induced by the combination therapy, we quantified nearly 9600 protein groups and 44,000 phosphopeptides with 36,000 class 1 phosphopeptides having quantitation in all groups (FDR &lt; 1%). We interrogated the Drug Signature Database (DSigDB) using the ~2,400 significantly-altered proteins (FDR &lt; 0.1%) and found the protein gene set to be highly correlated to genes downregulated by topoisomerase inhibition. To identify adaptive signaling pathways, we performed kinase-substrate enrichment analysis (KSEA) on the phosphoproteomic dataset containing ~8,000 significantly altered phosphopeptides (FDR &lt; 1%). KSEA identified hyperactivation of several G2/M checkpoint kinases such as Aurora kinases A and B. This integrative platform has revealed synergistic drug combinations with ARS-1620 and the phosphoproteomics has prescribed possibly the third drug of the combination therapy.
Note: This abstract was not presented at the meeting.
Citation Format: Joseph Capri, Thuc Le, Caius Radu, Timothy Donahue. Integrated drug high-throughput screening and quantitative phosphoproteomics rationalizes combination therapy for mutant KRAS pancreatic cancer [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 4228.