Abstract
Approximately 85-90% of colorectal cancers (CRC) are microsatellite stable and resist immune checkpoint inhibitors (ICI). The recent success of intismeran, a lipid nanoparticle (LNP)-delivered mRNA encoding patient-specific tumor antigens, enhances pembrolizumab responses, showing that LNP-delivered nucleic acids can render ICI-resistant tumors responsive by supplying what the tumor microenvironment lacks. Because an IFN-responsive phenotype predicts CRC response to checkpoint blockade and tumor cell PD-L1 represses IFN-I, we asked whether delivering the missing cytokine, rather than antigen, achieves the same conversion. Here we show that PD-1 blockade failed even when initiated before tumor seeding, yet deleting tumor cell PD-L1 abolished colon cancer lung metastasis, implicating a tumor-intrinsic PD-L1 function that antibody blockade does not neutralize. An LNP-encapsulated IFNα2-encoding nanoplasmid (LNP-IFNα2) transfected tumor cells within lung metastases, converting them into a self-sustaining and tumor-restricted IFNα2 source. LNP-IFNα2 suppressed colon cancer lung metastasis in syngeneic and humanized mouse models and sensitized these ICI-resistant tumors to PD-1 blockade. Efficacy improved further with neutralization of co-induced IL6. scRNA-Seq revealed multi-compartment reprogramming: SPP1+ macrophages acquired apoptotic signatures as IFN-responsive monocytes replaced them, progenitor-exhausted T cells exited quiescence and expanded, and tumor cells exited a high-cycling state, gained antigen presentation, and shifted away from cuproptosis resistance. The treated microenvironment transcriptionally recapitulated pembrolizumab-responder signatures, positioning LNP-IFNα2 as an off-the-shelf nanomedicine for ICI-resistant CRC.
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