Auranofin Sensitizes Oral Squamous Cell Carcinoma to PD-1 Blockade Through DUSP1-Associated Macrophage Reprogramming

Oral squamous cell carcinoma (OSCC) is frequently refractory to immune checkpoint blockade, in part because the tumor microenvironment is enriched with immunosuppressive, M2-like tumor-associated macrophages. Auranofin (ARN), an FDA-approved thioredoxin reductase inhibitor, induces oxidative and proteotoxic stress and may remodel myeloid compartments to improve immunotherapy responsiveness. Here, we investigated whether ARN sensitizes OSCC to PD-1 blockade through DUSP1-associated macrophage reprogramming. Using an immunotherapy-resistant, syngeneic MOC2 murine OSCC model, mice bearing established tumors were treated with vehicle, ARN, anti-PD-1, or combination therapy. Combination treatment significantly improved survival and produced the most pronounced reduction in tumor burden compared with control and monotherapy groups. In vitro, ARN increased Dusp1 mRNA in bone marrow-derived macrophages polarized toward an M2 phenotype in a time- and dose-dependent manner. In vivo, RNAscope analysis demonstrated increased Dusp1 expression within tumors following ARN and/or anti-PD-1, with co-localization patterns consistent with a shift toward a pro-inflammatory macrophage state. Functionally, ARN directly promoted macrophage repolarization, increasing the M1/M2 ratio by flow cytometry and suppressing expression of the M2 marker arginase-1 (Arg1). In tumors, ARN and anti-PD-1 each increased the frequency of M1-like macrophages while reducing M2-like populations. Adaptive immune profiling further showed increased CD8⁺ T-cell infiltration across treatments, peaking in the combination group. Tumor cells also upregulated PD-L1, PD-L2, and CTLA-4, consistent with heightened immune stress. Collectively, these findings support repurposing ARN as an immunomodulatory adjuvant to overcome resistance to PD-1 blockade in OSCC by inducing DUSP1-linked macrophage remodeling and enhancing cytotoxic T-cell-associated antitumor immunity.