de Rappard-Yuswack, G. | Search bioRxiv

bioRxiv2022

MEK inhibitor resistance in lung cancer cells associated with addiction to sustained ERK suppression

MEK inhibitors have yielded limited efficacy in KRAS-mutant lung adenocarcinoma (LUAD) patients due to drug resistance. We established trametinib-resistant KRAS-mutant LUAD cells and describe a state of "drug addiction" in a subset of resistant cases where cells are dependent on trametinib for survival. Dependence on ERK2 suppression underlies this phenomenon whereby trametinib removal hyperactivates ERK and results in ER stress and apoptosis. Amplification of KRASG12C occurs in drug-addicted cells and blocking mutant specific activity with AMG 510 rescues the lethality after trametinib withdrawal. Furthermore, increased KRASG12C expression is lethal to other KRAS mutant LUAD cells, consequential to ERK hyperactivation. Our study represents the first instance of this phenotype associated with KRAS amplification and demonstrates that acquired genetic changes that develop in the background of MAPK suppression can have unique consequence. We suggest that the presence of mutant KRAS amplification in patients may identify those that may benefit from a "drug holiday" to circumvent drug resistance. These findings demonstrate the toxic potential of hyperactive ERK signaling and highlight potential therapeutic opportunities in patients bearing KRAS mutations.

cancer biology↗

bioRxiv2021

A novel small molecule that induces cytotoxicity in lung cancer cells inhibits disulfide reductases GSR and TXNRD1

High-throughput phenotype-based screening of large libraries of novel compounds without known targets can identify small molecules that elicit a desired cellular response, but additional approaches are required to find and characterize their targets and mechanisms of action. Here we show that a compound termed lung cancer screen 3 (LCS3), previously selected for its ability to impair the growth of human lung adenocarcinoma (LUAD) cell lines, but not normal lung cells, induces oxidative stress and activates the NRF2 signaling pathway by generating reactive oxygen species (ROS) in sensitive LUAD cell lines. To identify the target that mediates this effect, we applied thermal proteome profiling (TPP) and uncovered the disulfide reductases GSR and TXNRD1 as LCS3 targets. Through enzymatic assays using purified protein, we confirmed that LCS3 inhibits disulfide reductase activity through a reversible, uncompetitive mechanism. Further, we demonstrate that LCS3-sensitive LUAD cells are correspondingly sensitive to the synergistic inhibition of glutathione and thioredoxin pathways. Lastly, a genome-wide CRISPR knockout screen identified the loss of NQO1 as a mechanism of LCS3 resistance. This work highlights the ability of TPP to uncover targets of small molecules identified by high-throughput screens and demonstrates the potential utility of inhibiting disulfide reductases as a therapeutic strategy for LUAD.

cancer biology↗