Oncogenic RAS as an adaptive signaling ecosystem: context-dependent vulnerabilities and resistance-informed therapeutic design

Direct RAS targeting has progressed from pharmacologic proof of concept to routine treatment for selected KRAS G12C-mutant cancers. KRAS G12C inhibitors and KRAS G12C-EGFR combinations established allele- and lineage-specific treatment paradigms. More recently, the multiselective RAS(ON) inhibitor daraxonrasib became the first FDA-approved direct RAS-targeted therapy for metastatic pancreatic adenocarcinoma, while the KRAS G12D-directed degrader setidegrasib remains investigational. Target engagement alone, however, does not ensure durable disease control, and the same drug class can perform differently across tumor lineages. This Review develops an adaptive RAS signaling ecosystem model in which allele and isoform biology, membrane organization, feedback architecture, mutant–wild-type RAS crosstalk, co-mutation patterns, chromatin state, epithelial-mesenchymal plasticity, metabolism, spatial heterogeneity, the tumor microenvironment and treatment delivery jointly determine pathway dependence and therapeutic escape. Comparisons among pancreatic ductal adenocarcinoma, colorectal cancer, lung adenocarcinoma and NRAS-mutant melanoma show how related oncogenic RAS nodes acquire different vulnerabilities in distinct tissue contexts. We integrate direct RAS inhibition with mechanism-guided vertical and horizontal strategies directed at feedback rebound, bypass signaling, cell-state persistence, stromal protection, metabolic adaptation and immune exclusion. We then translate this model into a biomarker-integrated development framework that links serial circulating tumor DNA, modality-matched pharmacodynamic assays, paired tissue sampling, spatial profiling and toxicity-aware scheduling to prespecified, falsifiable treatment hypotheses. RAS dependence is conditional rather than absolute. Durable control will require strategies that match the RAS allele and tumor lineage to the dominant adaptive circuitry, verify that target and pathway suppression persist over time, and maintain sufficient dose intensity to exert biologically effective pressure without disabling antitumor immunity or normal-tissue function.