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Updated: Aug 29, 2025
Implementation of In Vitro Drug Resistance Assays: Maximizing the Potential for Uncovering Clinically Relevant Resistance Mechanisms
Published on: December 9, 2015
Combinatorial approaches for mitigating resistance to KRAS-targeted therapies
Hannah R Warren1, Sarah J Ross2, Paul D Smith2
1Department of Molecular Physiology and Cell Signalling, Institute of Systems, Molecular and Integrative Biology, University of Liverpool, Liverpool L69 3BX, U.K.
Abstract:
Approximately 15% of all cancer patients harbor mutated KRAS. Direct inhibitors of KRAS have now been generated and are beginning to make progress through clinical trials. These include a suite of inhibitors targeting the KRASG12C mutation commonly found in lung cancer. We investigated emergent resistance to representative examples of different classes of Ras targeted therapies. They all exhibited rapid reactivation of Ras signaling within days of exposure and adaptive responses continued to change over long-term treatment schedules. Whilst the gene signatures were distinct for each inhibitor, they commonly involved up-regulation of upstream nodes promoting mutant and wild-type Ras activation. Experiments to reverse resistance unfortunately revealed frequent desensitization to members of a panel of anti-cancer therapeutics, suggesting that salvage approaches are unlikely to be feasible. Instead, we identified triple inhibitor combinations that resulted in more durable responses to KRAS inhibitors and that may benefit from further pre-clinical evaluation.
Insights
KRAS inhibitors show rapid resistance development in cancer, often reactivating Ras signaling. Combination therapies may offer more durable responses, suggesting new treatment strategies for KRAS-mutated cancers.
Area of Science:
- Oncology
- Molecular Biology
- Drug Discovery
Background:
- Mutated KRAS is found in approximately 15% of cancer patients.
- Direct KRAS inhibitors targeting mutations like KRASG12C are advancing in clinical trials, particularly for lung cancer.
Purpose of the Study:
- To investigate the mechanisms of emergent resistance to different classes of Ras-targeted therapies.
- To explore strategies for overcoming resistance and achieving durable responses to KRAS inhibitors.
Main Methods:
- Exposure of cancer models to representative KRAS inhibitors.
- Analysis of Ras signaling reactivation and adaptive responses over time.
- Gene expression profiling to identify resistance signatures.
- Evaluation of combination therapies and salvage approaches.
Main Results:
- Rapid reactivation of Ras signaling was observed within days of inhibitor exposure.
- Distinct gene expression signatures were associated with each inhibitor, commonly involving upregulation of upstream Ras activators.
- Long-term treatment led to evolving adaptive resistance responses.
- Resistance often resulted in cross-desensitization to other anti-cancer therapeutics, limiting salvage options.
Conclusions:
- Emergent resistance to KRAS inhibitors is a significant challenge, characterized by rapid Ras pathway reactivation.
- Combination therapy strategies, specifically triple inhibitor combinations, demonstrated more durable responses in pre-clinical models.
- Further pre-clinical evaluation of novel combination therapies is warranted to overcome resistance to KRAS-targeted treatments.
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