Introduction: CircRNAs are engaged in the tumorigenesis and progression of oral squamous cancer cells (OSCC). However, the function and underlying mechanism of circRNAs on tumor-associated immunity escape are largely unknown.

Materials and methods: We analyzed the expression pattern of has_circ_0069313 in our in-house database and its correlation with OSCC prognosis. Immunohistochemistry was applied to detected PDL1 expression. RNA fluorescence in situ hybridization was applied to detect subcellular location of circRNA. A luciferase activity assay was used to detect the interaction of has_circ_0069313 and miR-325-3p and its downstream target, Foxp3. Exosomes were collected to detect the exosomal circRNAs and co-culture assays were performed to detect the function of exosomal circRNAs on Tregs.

Results: has_circ_0069313 was upregulated in OSCC tissues and predicts poor prognosis. has_circ_0069313 promotes immunity escape through inhibiting miR-325-3p-induced Foxp3 degradation. has_circ_0069313 is an exosomal circRNA and the transfer of has_circ_0069313 to Treg cells promotes the Treg function through maintaining Foxp3 levels.

Conclusion: Our results indicate that has_circ_0069313 induces OSCC immunity escape via the miR-325-3p-Foxp3 axis in both OSCC cells and Treg cells.