USP22 as promoter of Treg cell infiltration and modulator of immunotherapy efficacy through the PIAS1/P65/CCL22 pathway in pancreatic cancer.

4174 Background: Immune checkpoint inhibitors targeting PD-1 and CTLA-4 have shown success in various cancers; however, their efficacy in pancreatic cancer remains limited, likely due to its immunosuppressive microenvironment. Treg cells are crucial in tumor immune evasion and suppression. Targeting Treg cells is an emerging strategy in pancreatic cancer immunotherapy. Recent studies show that USP22 (Ubiquitin-Specific Protease 22) regulates immunity by deubiquitinating key proteins like PD-L1 and STAT1 in tumor cells, while in Treg cells, USP22 controls FoxP3, modulating Treg cell function. This study aims to explore how USP22 regulates the immune microenvironment in pancreatic cancer and identify potential targets to enhance immune checkpoint blockade responses. Methods: Bioinformatics analysis of tissue microarrays and the TCGA database was used to assess the correlation between USP22 and Treg cell infiltration in pancreatic cancer. 2. Tumorigenicity assays, immunohistochemistry, and flow cytometry were performed in C57BL/6 mice to determine the effect of USP22 on Treg cell infiltration. 3. Transcriptomic and proteomic analyses were conducted to explore the mechanisms by which USP22 regulates Treg cell infiltration. 4. In vitro experiments, including Western blot, qRT-PCR, immunofluorescence, deubiquitination assays, and chromatin immunoprecipitation, were used to identify the specific mechanisms of USP22 in regulating Treg cell infiltration. 5. The combination of PD-1 monoclonal antibody and nab-paclitaxel chemotherapy was tested to determine if targeting USP22 improves immunotherapy efficacy. Results: Immunohistochemistry and bioinformatics analysis revealed a significant positive correlation between USP22 expression and Treg cell infiltration in pancreatic cancer. 2. Tumorigenicity assays in C57BL/6 mice showed that USP22 promotes tumor growth and Treg cell infiltration. 3. Transcriptomic analysis found a strong association between USP22 and the TRAF1/NF-κB signaling pathway as well as CCL22 expression. 4. In vivo and in vitro experiments confirmed that USP22 activates TRAF1/NF-κB signaling and increases CCL22 release, promoting Treg cell infiltration. 5. USP22 deubiquitinates PIAS1, inhibiting its nuclear translocation and activating p65. 6. USP22 knockdown improved therapeutic responses to combined immunotherapy (PD-1 inhibitors) and chemotherapy (nab-paclitaxel). Conclusions: USP22 promotes Treg cell infiltration in pancreatic cancer by deubiquitinating PIAS1, inhibiting its nuclear translocation, and activating the TRAF1/NF-κB signaling pathway, which leads to CCL22 release. Targeting USP22 could inhibit cell proliferation, promote apoptosis, and remodel the immune microenvironment, enhancing the efficacy of immune checkpoint blockade therapy.