Durable Suppression of Acquired MEK Inhibitor Resistance in Cancer by Sequestering MEK from ERK and Promoting Anti-Tumor T-cell Immunity [RNA-seq]

ABSTRACT: Disruption of the MAPK pathway in cancer by kinase inhibition often fails due to pathway reactivation, causing clinical relapse. Among MAPK inhibitors, type I RAF inhibitors are only active against specific BRAF mutants; MEK inhibitor monotherapy is associated with limited clinical benefits but may serve as a foundation for combinatorial therapy. Here, we show that type II RAF plus allosteric MEK inhibitors durably blunt the development of acquired MEK inhibitor resistance among cancers with KRAS, NRAS, NF1, BRAFnon-V600 and BRAFV600 mutations, when compared to a combination of type II RAF plus ERK inhibitors. Type II RAF and MEK (versus ERK) inhibitors also display superior capacity to sequester MEK in RAF complexes and uncouple MEK and ERK interaction in acquired resistant tumor subpopulations. Systemically and intratumorally, type II RAF plus MEK inhibitors expand memory and activated/exhausted CD8+ T-cells. Whereas trametinib alone temporally reduces dominant intra-tumoral T-cell clones, type II RAF inhibitor co-treatment reverses this effect and promotes T-cell clonotypic expansion and convergence. Importantly, durably control of tumors by this combination requires CD8+ T-cells. Thus, the prolonged anti-tumor efficacy of type II RAF plus MEK inhibitors reveals exquisite MAPK addiction in common lethal cancer histologies, and the mechanisms include unexpected allosteric perturbation of the MAPK pathway and engagement of anti-tumor CD8+ T-cell immunity.

ORGANISM(S): Homo sapiens

PROVIDER: GSE158607 | GEO | 2021/06/06

REPOSITORIES: GEO