Next-generation CAR-T engineering for colorectal cancer: integrating targets, tumor microenvironment barriers, and emerging strategies.

Chimeric antigen receptor (CAR)-T cell therapy for colorectal cancer (CRC) faces three major barriers: antigen heterogeneity, off-tumor toxicity, and the efficacy-safety trade-off. To overcome these obstacles, next-generation engineering strategies have emerged, including: (1) novel CRC-associated targets with improved tissue restriction; (2) architectural innovations such as armored CARs, optimized signaling (1XX, 28-ΔIL2RB-z(YXXQ)), and cytokine-arming; (3) combinatorial antigen-sensing circuits (AND/OR/NOT gates, SUPRA, synNotch); and (4) CRISPR-based editing for exhaustion-related knockouts (e.g., PD-1, Fas, TGFBR2) and site-specific CAR knock-in. Clinical evidence has demonstrated objective responses and disease stabilization in subsets of patients.

However, the immunosuppressive tumor microenvironment-including inhibitory cells, dense stroma, and metabolic dysfunction-remains a critical hurdle limiting CAR-T persistence. Future directions should prioritize molecular typing-guided intervention, universal CAR-T, multicellular platforms (CAR-NK, CAR-M), and interdisciplinary collaboration. This review provides a framework for designing next-generation CAR-T therapies capable of achieving durable remissions in advanced CRC.