# CRISPR knockout screens reveal JUN as the master mediator of resistance to MAPK inhibition in KRAS-mutant pancreatic cancer

## TL;DR

This study identifies JUN as a key driver of resistance to certain cancer drugs in pancreatic cancer with KRAS mutations, offering new insights for treatment strategies.

## Contribution

The study reveals JUN as a novel resistance mediator to MAPK inhibition in KRAS-mutant pancreatic cancer, suggesting new therapeutic approaches.

## Key findings

- CRISPR screens identified mTOR and JUN hyperactivation as resistance mechanisms to MAPK suppression.
- JUN was confirmed as the most downstream resistance mediator and a potential therapeutic target.
- PI3K/AKT/mTOR and JUN pathway alterations predict resistance to MAPK inhibitor combinations in KRAS-mutant PDAC.

## Abstract

Pancreatic ductal adenocarcinoma (PDAC) is often driven by KRAS mutations, but inhibitors targeting the most frequent KRAS substitutions in PDAC are not yet approved in the clinic. We previously discovered that KRAS-mutant PDAC is sensitive to the combination of SHP2 and ERK inhibitors, recently investigated in the Phase I/Ib clinical trial NCT04916236. Lately, RAS(ON) multi-selective inhibitors have entered clinical development, representing a promise for mono or combination therapies in PDAC. However, resistance may arise even for combination therapies. Here, we aimed at anticipating mechanisms of resistance to SHP2 plus ERK or RAS(ON) multi-selective inhibitors.

We performed a genome-wide CRISPR-KO screening, followed by four follow-up focused screenings, leading to the identification of resistance mediators, which were further validated through functional genetic and pharmacological experiments, both in vitro and in vivo.

Through unbiased CRISPR-based screenings, we identified mTOR and JUN hyperactivation as interconnected mechanisms that overcome MAPK suppression. Further investigation pointed at JUN as the most downstream resistance mediator, and indirect therapeutic target, using MAP2K4 inhibitors.

Alterations in the PI3K/AKT/mTOR and JUN pathways can induce resistance to multiple combinations of MAPK pathway inhibitors, and may serve as biomarkers for sensitivity/resistance in clinical trials exploring such combinations in KRAS-mutant PDAC.

The online version contains supplementary material available at 10.1186/s13046-025-03616-z.