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Oncogenic KRAS drives cancer growth by activating diverse signaling networks, not all of which have been fully delineated. We set out to establish a system-wide profile of the KRAS-regulated kinase signaling network (kinome) in KRAS-mutant pancreatic ductal adenocarcinoma (PDAC). We knocked down KRAS expression in a panel of six cell lines and then applied multiplexed inhibitor bead/MS to monitor changes in kinase activity and/or expression. We hypothesized that depletion of KRAS would result in downregulation of kinases required for KRAS-mediated transformation and in upregulation of other kinases that could potentially compensate for the deleterious consequences of the loss of KRAS. We identified 15 upregulated and 13 downregulated kinases in common across the panel of cell lines. In agreement with our hypothesis, all 15 of the upregulated kinases have established roles as cancer drivers (e.g., SRC, TGF-β1, ILK), and pharmacological inhibition of one of these upregulated kinases, DDR1, suppressed PDAC growth. Interestingly, 11 of the 13 downregulated kinases have established driver roles in cell cycle progression, particularly in mitosis (e.g., WEE1, Aurora A, PLK1). Consistent with a crucial role for the downregulated kinases in promoting KRAS-driven proliferation, we found that pharmacological inhibition of WEE1 also suppressed PDAC growth. The unexpected paradoxical activation of ERK upon WEE1 inhibition led us to inhibit both WEE1 and ERK concurrently, which caused further potent growth suppression and enhanced apoptotic death compared with WEE1 inhibition alone. We conclude that system-wide delineation of the KRAS-regulated kinome can identify potential therapeutic targets for KRAS-mutant pancreatic cancer., Competing Interests: Conflict of interest C. J. D. is a consultant/advisory board member for Anchiano Therapeutics, Deciphera Pharmaceuticals, Mirati Therapeutics, and Revolution Medicines. C. J. D. has received research funding support from SpringWorks Therapeutics, Mirati Therapeutics, and Deciphera Pharmaceuticals and has consulted for Ribometrix, Sanofi, Jazz Therapeutics, Turning Point Therapeutics, and Eli Lilly. A. D. C. has consulted for Eli Lilly and Mirati Therapeutics. E. F. P. and M. P. are inventors on US government and university assigned patents and patent applications that cover aspects of the technologies discussed such as the reverse phase protein microarrays. As inventors, they are entitled to receive royalties as provided by US Law and George Mason University policy. M. P. and E. F. P. receive royalties from and are consultants of TheraLink Technologies, Inc. E. F. P. is a shareholder of TheraLink Technologies, Inc. and a shareholder and consultant of Perthera, Inc. All other authors no conflicts of interest with the contents of this article., (Copyright © 2021 The Authors. Published by Elsevier Inc. All rights reserved.)

We address whether combinations with a pan-RAF inhibitor (RAFi) would be effective in KRAS mutant pancreatic ductal adenocarcinoma (PDAC). Chemical library and CRISPR genetic screens identify combinations causing apoptotic anti-tumor activity. The most potent combination, concurrent inhibition of RAF (RAFi) and ERK (ERKi), is highly synergistic at low doses in cell line, organoid, and rat models of PDAC, whereas each inhibitor alone is only cytostatic. Comprehensive mechanistic signaling studies using reverse phase protein array (RPPA) pathway mapping and RNA sequencing (RNA-seq) show that RAFi/ERKi induced insensitivity to loss of negative feedback and system failures including loss of ERK signaling, FOSL1, and MYC; shutdown of the MYC transcriptome; and induction of mesenchymal-to-epithelial transition. We conclude that low-dose vertical inhibition of the RAF-MEK-ERK cascade is an effective therapeutic strategy for KRAS mutant PDAC., Competing Interests: Declaration of Interests C.J.D. is a consultant/advisory board member for Mirati Therapeutics and Deciphera Pharmaceuticals. C.J.D. has received research funding support from Mirati Therapeutics and Deciphera Pharmaceuticals and has consulted for Ribometrix, Jazz Therapeutics, SVB Leerink, Axon Advisors LLC, Third Bridge, SmartAnalyst, Turning Point Therapeutics, and Eli Lilly. A.D.C. has consulted for Eli Lilly and Mirati Therapeutics. E.F.P. and M.P. receive royalties from Avant Diagnostics. E.F.P. is a consultant to and shareholder of Avant Diagnostics, Inc. and Perthera, Inc. and received funding support from Mirati Therapeutics, Genentech, Inc., and Abbvie, Inc. R.V.T. was previously employed at Eli Lilly and Company and is now employed at Astellas Pharma US. S.V.B., S.-B.P., and R.V.T. are shareholders of Eli Lilly., (Copyright © 2020 The Author(s). Published by Elsevier Inc. All rights reserved.)

Purpose: The EphA2 tyrosine kinase is frequently overexpressed in human tumors that are also treated with radiation. However, few studies have examined the effect of radiation on the EphA2 receptor itself. The purpose of this project was to investigate the impact of radiation on EphA2 to better understand mechanisms of radioresistance., Materials and Methods: Cell lines were exposed to X-rays and assayed for changes in EphA2 protein levels and phosphorylation over time by Western blotting. HEK293 cells stably expressing wild-type EphA2 or the S897A mutant were analyzed for cell survival from X-rays., Results: Treatment of different cancer cell lines with 2 Gy of X-rays induced the phosphorylation of EphA2 on S897 but no changes were found in EphA2 total levels or its tyrosine phosphorylation. Radiation-induced S897 phosphorylation was unaffected by an AKT inhibitor but blocked by a MEK or RSK inhibitor. HEK293 cells expressing the EphA2 S897A mutant had a nearly 2-fold lower level of cell survival from X-rays than cells expressing wild-type EphA2., Conclusions: These findings show that radiation induces S897 EphA2 phosphorylation, an event associated with increased cell survival. Therefore, targeting pathways that mediate EphA2 S897 phosphorylation may be a beneficial strategy to reduce radioresistance.