Targeted hyperthermia therapy (THT) using gold nanorods remodels the tumor microenvironment to sensitize murine microsatellite-stable colorectal cancer to immune checkpoint blockade.

Microsatellite-stable (MSS) colorectal cancers are refractory to immune checkpoint blockade (ICB) due to limited baseline inflammation, inefficient antigen presentation, and impaired T cell priming. We investigated whether nanomaterial-enabled targeted hyperthermia therapy (THT), based on intratumoral gold nanorods (GNRs) that convert near-infrared (NIR) light into localized heat, could remodel this microenvironment and enhance responsiveness to ICB. CT26 colorectal tumors were established subcutaneously in BALB/c mice. Intratumorally delivered GNRs (Sona Nanotech Inc.) were activated by NIR light to induce hyperthermia (42-48 °C) for 5 min. Mice received one or two THT treatments and were subsequently treated with anti-PD-1 alone or in combination with anti-CTLA-4. Tumor progression and immune responses were evaluated for up to 49 days using flow cytometry, bulk RNA sequencing, qPCR, and with tumor growth and thermal analyses. THT achieved reproducible intratumoral heating and transiently slowed MSS CT26 tumor growth. Immune profiling demonstrated expansion of adaptive immune populations, accompanied by transcriptional induction of chemokine, complement, matrix-remodeling, stress-response, and antigen-processing pathways. This thermally conditioned immune landscape improved responsiveness to anti-PD-1 therapy, with THT combined with anti-PD-1 enhancing tumor control and prolonging survival. Reduced pulmonary gp70 levels in THT-plus-anti-PD-1 cohorts suggested diminished lung metastasis. A second THT treatment further strengthened adaptive immune responses, promoted focused TCRβ clonal remodeling, and improved tumor control, achieving complete regression in a subset of anti-PD-1-treated mice. Collectively, these findings demonstrate that GNR-enabled targeted hyperthermia can reprogram immunologically cold MSS colorectal tumors, enhance antigen visibility and T-cell activation, and restore sensitivity to ICB.