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Updated: Jul 18, 2026
Pooled CRISPR-Based Genetic Screens in Mammalian Cells
Published on: September 4, 2019
Genome-wide CRISPR-cas9 knockout screening identifies GRB7 as a driver for MEK inhibitor resistance in KRAS mutant
1Laboratory of Integrative Medicine, Clinical Research Center for Breast, State Key Laboratory of Biotherapy, West China Hospital, Sichuan University and Collaborative Innovation Center, Chengdu, Sichuan, 610041, China.
Abstract:
Targeting the KRAS pathway is a promising but challenging approach for colorectal cancer therapy. Despite showing potent efficacy in BRAF-mutated melanoma, MEK inhibitors appeared to be tolerated by colorectal cancer cells due to their intrinsic compensatory signaling. Here, we performed genome-wide CRISPR/Cas9 screening in the presence of MEK inhibitor to identify genes that are synthetically lethal with MEK inhibition in CRC models harboring KRAS mutations. Several genes were identified as potential functional drivers, which were significantly enriched in the GRB7-mediated RTK pathway. Loss-of-function and gain-of-function assays validated that GRB7 potently rendered CRC cells primary resistance to MEK inhibitors through the RTK pathway. Mass spectrum analysis of GRB7 immunoprecipitates revealed that PLK1 was the predominant interacting kinase of GRB7. Inhibition of PLK1 suppressed downstream signaling of RTK, including FAK, STAT3, AKT, and 4EBP1. The combination of PLK1 and MEK inhibitors synergistically inhibited CRC cell proliferation and induced apoptosis in vitro and in vivo. In conclusion, we identified GRB7-PLK1 as a pivotal axis mediating RTKs, resulting in MEK inhibitor tolerance. PLK1 is therefore a promising target for synergizing MEK inhibitors in the clinical treatment of CRC patients harboring KRAS mutations.
Insights
Researchers identified GRB7-PLK1 as a key pathway causing resistance to MEK inhibitors in KRAS-mutated colorectal cancer (CRC). Targeting PLK1 alongside MEK inhibitors offers a promising strategy to overcome treatment tolerance in CRC patients.
Area of Science:
- Oncology
- Molecular Biology
- Cancer Genetics
Background:
- Targeting the KRAS pathway is crucial for colorectal cancer (CRC) therapy.
- MEK inhibitors show limited efficacy in CRC due to compensatory signaling pathways.
- Identifying resistance mechanisms is vital for improving CRC treatment outcomes.
Purpose of the Study:
- To identify genes synthetically lethal with MEK inhibition in KRAS-mutated CRC models.
- To elucidate the role of GRB7 in mediating resistance to MEK inhibitors.
- To explore PLK1 as a potential therapeutic target in combination with MEK inhibitors for CRC.
Main Methods:
- Genome-wide CRISPR/Cas9 screening was employed in CRC models with KRAS mutations under MEK inhibitor treatment.
- Loss-of-function and gain-of-function assays were used to validate GRB7's role.
- Mass spectrometry identified PLK1 as a GRB7 interacting kinase.
Main Results:
- GRB7 was identified as a key mediator of primary resistance to MEK inhibitors via the RTK pathway.
- PLK1 was found to be the predominant kinase interacting with GRB7.
- Combined inhibition of PLK1 and MEK synergistically reduced CRC cell proliferation and induced apoptosis in vitro and in vivo.
Conclusions:
- The GRB7-PLK1 axis is a pivotal mechanism driving RTK-mediated tolerance to MEK inhibitors in KRAS-mutated CRC.
- PLK1 inhibition potentiates MEK inhibitor efficacy, suggesting its potential as a therapeutic target.
- This study provides a rationale for combining PLK1 and MEK inhibitors for treating KRAS-mutated CRC.
