Background: Tumor associated macrophages (TAMs) have strong plasticity and if reprogrammed, can clear tumor cells and regulate the adaptive immune system for cancer immunotherapy. Deubiquitinating enzymes (DUBs), which can remove ubiquitin (Ub) from Ub-modified substrates, have been associated with oncogenic metabolism but are not well-known for regulating TAMs repolarization. Methods: The expression of DUB related genes in macrophages (MΦs) was detected by reverse transcription-PCR. Flow cytometry and immunofluorescence were used to detect the changes of immune cells in the tumor microenvironment and spleen, including M1 (CD11b + F4/80 + CD86 + CD206 - ), and M2 (CD11b + F4/80 + CD86 - CD206 + ) MΦs, and IFN-γ + CD8 + T cells. A proliferation assay was used to determine the effect of M2 MΦs treated with a USP7 inhibitor on T cell proliferation. Western blotting was used to detect the expression of USP7 and the activation of the MAPK pathway. The TGCA database was used to assess the role of USP7 in the immune microenvironment of human lung adenocarcinoma (LUAD). Results: 51 DUB genes were screened and USP7 was identified as a highly expressed gene in M2 but not M1 MΦs. Specific silencing of USP7 using siRNA or USP7 inhibitors led to phenotypical and functional changes in M2 MΦs, favoring CD8 + T cells proliferation in vitro . USP7 inhibitors delayed tumor growth in mice with Lewis lung carcinoma, and promoted tumor infiltration of M1 MΦs and IFN-γ + CD8 + T cells. Depletion of TAMs attenuated these therapeutic effects. USP7 inhibition was shown to mediate MΦs reprogramming by activating the p38 MAPK pathway. Administration of USP7 inhibitors increased the expression of programmed cell death ligand 1 (PD-L1) in tumors, while blocking programmed cell death protein 1 (PD-1) provided an effective anti-tumor response. Clinical databases suggest that high expression of USP7 in LUAD was negatively correlated with innate and adaptive immunity. Conclusions: Taken together, these results provide evidence to suggest that therapeutic approaches targeting USP7, in combination with immunotherapy, should be considered for lung cancer treatment.

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Malignant ascites in advanced hepatocellular carcinoma (HCC) is a complex clinical problem that lacks effective treatments. Due to the insensitivity of advanced HCC cells to traditional chemotherapies, low drug accumulation, and limited drug residence time in the peritoneal cavity, the therapeutic effects of malignant ascites in HCC are not satisfactory. In this study, an injectable hydrogel drug delivery system based on chitosan hydrochloride and oxidized dextran (CH‐OD) is designed to load sulfasalazine (SSZ), an FDA‐approved drug with ferroptosis‐inducing ability, for effective tumor‐killing and activation of anti‐tumor immunity. Compared to free SSZ, SSZ‐loaded CH‐OD (CH‐OD‐SSZ) hydrogel exhibits greater cytotoxicity and induces higher levels of immunogenic ferroptosis. In the preclinical model of hepatoma ascites, intraperitoneal administration of CH‐OD‐SSZ hydrogel can significantly suppress tumor progression and improve the immune landscape. Both in vitro and in vivo, CH‐OD‐SSZ hydrogel induces the repolarization of macrophages to an M1‐like phenotype and promotes the maturation and activation of dendritic cells. Combination treatment with CH‐OD‐SSZ hydrogel and anti‐programmed cell death protein 1 (PD‐1) immunotherapy achieves more than 50% ascites regression and generates long‐term immune memory. Collectively, CH‐OD‐SSZ hydrogel exhibits promising therapeutic potential in the treatment of peritoneal dissemination and malignant ascites in advanced HCC, especially when combined with anti‐PD‐1 immunotherapy.