CD276 Promotes Immune Evasion in Clear Cell Renal Cell Carcinoma via NF-κB–IL-6–STAT3 Signaling Crosstalk

Background: Clear cell renal cell carcinoma (ccRCC) exhibits prominent immune infiltration and inflammatory signaling, yet the tumor-intrinsic mechanisms that promote immune evasion remain incompletely defined. CD276/B7-H3 is linked to an unfavorable prognosis in ccRCC, but its involvement in regulating inflammatory immune suppression requires clarification. This study aimed to determine whether tumor-cell CD276 drives NF-κB–IL-6–STAT3 signaling and macrophage-dependent immune evasion in ccRCC.

Methods: TCGA-KIRC data were analyzed to assess CD276 expression, prognosis, and immune-related signatures. Stable CD276-knockdown 786-O and Caki-1 cells were generated using shRNA. Cell proliferation, invasion, NF-κB activation, cytokine secretion, and STAT3 signaling were evaluated using CCK-8, Transwell assays, Western blotting, immunofluorescence, luciferase reporter assays, RT-qPCR, and ELISA. Tumor-conditioned media were applied to THP-1-derived macrophages to examine STAT3-dependent polarization. Macrophage–T-cell co-culture assays were used to assess T-cell activation, cytokine secretion, and proliferation.

Results: CD276 was highly expressed in ccRCC tissues and was associated with poorer overall survival and enrichment of macrophage-related and IL-6–JAK–STAT3 immune signatures. CD276 knockdown inhibited ccRCC cell proliferation and invasion, reduced NF-κB p65 nuclear translocation and transcriptional activity, and decreased IL-6 production. CD276 silencing also attenuated STAT3 phosphorylation in tumor cells and macrophages. Conditioned media from CD276-knockdown cells suppressed CD206⁺CD163⁺ macrophage polarization, decreased ARG1 and IL10 expression, and increased iNOS expression. Functionally, macrophages exposed to CD276-deficient tumor media showed reduced suppression of CD3⁺ T-cell activation, IFN-γ and IL-2 secretion, and proliferation. Recombinant IL-6 restored, whereas STAT3 inhibition or IL-6 neutralization diminished, these effects.

Conclusions: CD276 promotes ccRCC immune evasion by activating an NF-κB–IL-6–STAT3 signaling axis that drives immunosuppressive macrophage polarization and T-cell dysfunction.