Abstract

Combining immunotherapy with other treatments improves survival in colorectal cancer, yet some patients remain unresponsive. Tumor-associated macrophages (TAMs) are a key immune cell population driving this immunotherapy resistance and fostering an immunosuppressive microenvironment. To overcome this, we screened a deubiquitinating enzyme (DUB) library targeting TAMs and identified USP14 as specifically upregulated in TAMs. Inhibiting USP14 reversed their pro-tumor functions, promoted M1 polarization, enhanced tumor cell killing, and activated effector T cells. USP14 inhibition also increased PD-L1 expression on tumor cells, alleviating T-cell suppression. In vivo , combining a USP14 inhibitor with an anti-PD-1 antibody synergistically enhanced immunotherapy efficacy, suppressed tumor progression, and improved survival in a mouse colon cancer model. Thus, USP14 is a promising target to overcome immunotherapy resistance in colorectal cancer.