From KRAS inhibition to tumor adaptation: mechanistic layers of resistance and therapeutic strategies.

BACKGROUND: KRAS is a central oncogenic driver in multiple solid malignancies, including non-small cell lung cancer, pancreatic ductal adenocarcinoma, and colorectal cancer. Activating KRAS mutations, together with co-mutations and gene-dosage alterations, reprogram signaling pathways, cellular metabolism, and the tumor microenvironment, thereby promoting aggressive tumor behavior and therapeutic resistance. Despite recent advances, including KRAS G12C inhibitors and emerging agents targeting G12D, pan-RAS(ON), and nucleotide-free RAS, clinical responses remain limited in many KRAS-mutant contexts due to rapid and multifaceted resistance. AIM OF REVIEW: This review aims to examine the mechanisms underlying resistance to KRAS-targeted therapies and to provide an integrated perspective on how adaptive tumor responses limit the durability of KRAS inhibition. KEY SCIENTIFIC CONCEPTS OF REVIEW: Selective pressure from KRAS-targeted therapies drives adaptive tumor evolution through on-target alterations, rewiring of signaling networks, and non-genetic changes in cell state and the tumor microenvironment. This review synthesizes current knowledge on these resistance mechanisms and highlights emerging therapeutic strategies, including rational combination approaches, enhanced RAS pathway suppression, targeted protein degradation, and KRAS-directed immunotherapies. By integrating recent preclinical and clinical advances, this work provides a comprehensive framework for understanding resistance and improving the durability of KRAS pathway inhibition in cancer.