Overcoming immunotherapy resistance in colorectal cancer through nano-selenium probiotic complexes and IL-32 modulation.

Background And Objective: Colorectal cancer (CRC) is a major global health burden, with immunotherapy often limited by immune tolerance and resistance. This study introduces an innovative approach using Selenium Nanoparticles-Loaded Extracellular Vesicles combined with Interleukin-32 and Engineered Probiotic Escherichia coli Nissle 1917 (SeNVs@NE-IL32-EcN) to enhance CD8 T cell-mediated immune responses and overcome immunotherapy resistance.

Methods: Single-cell RNA sequencing (scRNA-seq) and transcriptomic analyses were performed to identify key immune cells and regulators involved in CRC immunotherapy resistance, focusing on CD8 T cells and the regulatory factor IL32. A humanized xenograft mouse model was used to evaluate the impact of IL32 and SeNVs@NE-IL32-EcN on tumor growth and immune responses. The SeNVs@NE-IL32-EcN complex was synthesized through a reverse micelle method and functionalized using extracellular vesicles. Its morphology, size, antioxidant activity, and safety were characterized using electron microscopy, dynamic light scattering (DLS), and in vitro co-culture assays.

Results: Single-cell analyses revealed a significant reduction in CD8 T cell infiltration in immunotherapy-resistant CRC patients. IL32 was identified as a key regulator enhancing CD8 T cell cytotoxic activity through granzyme B and IFN-γ secretion. Treatment with SeNVs@NE-IL32-EcN significantly improved the proliferation and activity of CD8 T cells and reduced tumor progression in humanized mouse models. In vitro and in vivo results demonstrated the complex's biocompatibility, antioxidant properties, and ability to enhance CRC immunotherapy while mitigating immune tolerance.

Conclusion: SeNVs@NE-IL32-EcN offers a novel nano-biomaterial strategy that integrates nanotechnology and probiotic therapy to enhance CD8 T cell-mediated immunity and overcome CRC immunotherapy resistance. This study lays the foundation for future therapeutic applications in cancer treatment by advancing immune-modulating biomaterials.