Abstract 2621: Characterizing MEK1/2 degradation in K-ras mutant cells

Activating KRAS mutations frequently occur in several cancers including the majority of pancreatic ductal adenocarcinoma (96%), ~50% of colorectal cancers, and ~30% of lung adenocarcinoma. It has been shown that mutant K-ras preferentially signals through RAF-MEK-ERK signaling and that blockade of this pathway is essential for tumor regression. However, targeted MEK inhibitors (MEKi) have shown limited clinical benefit in the treatment of K-ras mutant cancers due to resistance caused by the feedback activation of the upstream kinase CRAF. Recently, PROTACs (Proteolysis-Targeting Chimeras) targeting MEK1 and MEK2 were developed, providing a new therapeutic strategy to degrade MEK1/2 in K-ras mutant cancer cells. Due to the fact that feedback-induced CRAF causes MEKi resistance in K-ras mutant cells, we postulated that degrading MEK1/2 could bypass CRAF-mediated resistance. Indeed, treatment of MEKi-sensitive or resistant K-ras mutant cell lines with MEK1/2 degraders rapidly reduced MEK1/2 protein levels and downstream ERK signaling causing growth inhibition and apoptosis. Proteomics characterization of K-ras mutant cell lines following MEK1/2 degrader or inhibitor treatment revealed MEK1/2 degradation exhibited distinct signaling pathway responses compared to inhibition. Together, our studies showed MEK1/2 degraders represent a promising avenue for the treatment K-ras mutant cancers that can by-pass resistance mechanisms observed with traditional MEK1/2 inhibitors.

Citation Format: Carlos Herrera-Montavez, Alison M. Kurimchak, Jian Jin, James S. Duncan. Characterizing MEK1/2 degradation in K-ras mutant cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 2621.

Extensive rewiring of the EGFR network in colorectal cancer cells expressing transforming levels of KRASG13D

Protein-protein-interaction networks (PPINs) organize fundamental biological processes, but how oncogenic mutations impact these interactions and their functions at a network-level scale is poorly understood. Here, we analyze how a common oncogenic KRAS mutation (KRASG13D) affects PPIN structure and function of the Epidermal Growth Factor Receptor (EGFR) network in colorectal cancer (CRC) cells. Mapping >6000 PPIs shows that this network is extensively rewired in cells expressing transforming levels of KRASG13D (mtKRAS). The factors driving PPIN rewiring are multifactorial including changes in protein expression and phosphorylation. Mathematical modelling also suggests that the binding dynamics of low and high affinity KRAS interactors contribute to rewiring. PPIN rewiring substantially alters the composition of protein complexes, signal flow, transcriptional regulation, and cellular phenotype. These changes are validated by targeted and global experimental analysis. Importantly, genetic alterations in the most extensively rewired PPIN nodes occur frequently in CRC and are prognostic of poor patient outcomes.