Dual RAF inhibition outperforms RAF-MEK combinations for suppressing ERK signaling in KRAS mutant cells

Area of Science:

• Oncology
• Molecular Biology
• Computational Biology

Background:

• RAS-RAF-MEK signaling pathway is crucial in cancer.
• Kinase inhibitors targeting this pathway show complex efficacy due to isoform interactions.
• KSR1 protein's role in modulating inhibitor response is not fully understood.

Purpose of the Study:

• To investigate how KSR1 abundance affects cellular responses to RAF and MEK inhibitors.
• To computationally model and experimentally validate the impact of KSR1 on inhibitor efficacy.
• To compare the effectiveness of different inhibitor combinations in RAS-mutant cancer cells.

Main Methods:

• Utilized structure-and-rule-based computational modeling.
• Conducted experiments on PSN1 (mutant KRAS) and MCF7 (wild-type KRAS) cancer cell lines.
• Performed KSR1 knockdown experiments and analyzed ERK signaling pathway responses.

Main Results:

• KSR1 knockdown had minimal effect on ppERK response to Type I½ RAF inhibitor (Encorafenib).
• MEK inhibitor (Cobimetinib) efficacy varied with KSR1 levels and cell type, aligning with model predictions.
• Two conformation-specific RAF inhibitors combined were more effective than RAF and MEK inhibitor combinations in RAS-mutant cells.

Conclusions:

• KSR1 levels modulate sensitivity to specific RAF and MEK inhibitors.
• Computational models accurately predict experimental outcomes regarding KSR1's role.
• Dual RAF inhibition offers a superior strategy for ERK pathway suppression in RAS-mutant cancers, independent of KSR1 levels.