Mechanism of neoantigen generation and advances in neoantigen-based immunotherapies in colorectal cancer.

Colorectal cancer (CRC) is a leading cause of cancer-related morbidity and mortality worldwide. Conventional therapeutic modalities-such as surgery, chemotherapy, and radiotherapy-yield suboptimal outcomes in advanced or recurrent disease, while immune checkpoint inhibitors demonstrate durable clinical benefit almost exclusively in the microsatellite instability-high (MSI-H) subset, which constitutes only ~ 15% of CRC cases. This stark therapeutic gap underscores an unmet medical need for novel, mechanism-driven immunotherapies. Tumor neoantigens-immunogenic peptides arising from somatic mutations and exclusively presented on malignant cells-represent highly promising targets for precision immunotherapy owing to their strict tumor-restricted expression and negligible risk of on-target, off-tumor toxicity.

This review outlines the molecular mechanisms driving neoantigen generation in CRC, including frameshift mutations, single-nucleotide variants, alternative RNA splicing, and circular RNA-derived epitopes. We further delineate the immunological cascade by which these neoantigens are processed, presented via MHC molecules, and recognized by antigen-specific CD8+ and CD4+ T cells to elicit potent antitumor immunity. Subsequently, we evaluate neoantigen-directed therapeutic platforms, encompassing personalized neoantigen vaccines (peptide-, RNA-, and dendritic cell-based formulations, as well as innovative combinatorial delivery systems) and adoptive T-cell therapies-including tumor-infiltrating lymphocyte (TIL), chimeric antigen receptor T cells (CAR-T) and T cell receptor-engineered T cells (TCR-T)-that are engineered to recognize neoantigen-derived epitopes. Although challenges-including low tumor mutational burden (TMB), adaptive immune evasion, and spatially heterogeneous neoantigen expression-continue to impede broad clinical efficacy, emerging solutions-such as engineered exosome-based delivery, pharmacologic induction of neoantigen presentation (e.g., via RECTAS), and rationally designed combination regimens (e.g., with 5-fluorouracil or bevacizumab)-are demonstrating encouraging preclinical activity.

Looking forward, strategic targeting of clonal driver mutation-derived neoantigens and accelerated clinical development of next-generation neoantigen vaccine platforms hold significant potential to redefine the treatment paradigm for patients with CRC.