Metabolic plasticity drives specific mechanisms of chemotherapy and targeted therapy resistance in metastatic colorectal cancer

Microsatellite-stable metastatic colorectal cancer (MSS mCRC) is currently treated with chemotherapy and targeted agents based on RAS and BRAF mutational status. Although these therapies offer initial benefit, most patients rapidly develop resistance, with fewer than 20% remaining progression-free at two years. This review aims to synthesize emerging evidence on the metabolic mechanisms driving treatment resistance in MSS mCRC, with a particular focus on the immune-metabolic signature (IMMETCOLS) classification. We conducted a comprehensive review of preclinical models, transcriptomic datasets, and clinical trial results addressing metabolic adaptations to chemotherapy and targeted therapies in MSS mCRC. The IMMETCOLS framework defines three metabolic subtypes-IMC1, IMC2, and IMC3-each associated with distinct resistance mechanisms. IMC1 exhibits glycolysis and transforming growth factor-β (TGF-β)-dependent signaling enriched in inflammatory fibroblasts, conferring resistance to chemotherapy. IMC2 relies on oxidative phosphorylation and glutamine metabolism, supporting antioxidant defenses and resistance to both cytotoxic agents and anti-EGFR therapies. IMC3 demonstrates lactate-fueled respiration and pentose phosphate pathway activation, contributing to redox balance, DNA repair, and resistance to targeted therapies such as anti-BRAF or KRAS inhibitors. All subtypes display metabolic plasticity under therapeutic pressure. Emerging clinical data support tailoring targeted therapy combinations based on IMMETCOLS subtype, particularly in BRAF- and HER2-positive populations. Understanding subtype-specific metabolic rewiring in MSS mCRC offers novel opportunities to overcome drug resistance. Targeting the metabolic vulnerabilities defined by the IMMETCOLS signature may improve response durability and inform precision treatment strategies.