Saccharide analog, 2‐deoxy‐d‐glucose enhances 4‐1BB‐mediated antitumor immunity via PD‐L1 deglycosylation

Triple‐negative breast cancer (TNBC) lacks a well‐defined molecular target and is associated with poorer outcomes compared to other breast cancer subtypes. Programmed cell death protein 1 (PD‐1)/programmed death‐ligand 1 (PD‐L1) blockade therapy shows a 10% to 20% response rate in TNBC patients. Our previous studies show that PD‐L1 proteins are heavily glycosylated in TNBC, and the glycosylation plays an important role in the PD‐L1 protein's stability and immunosuppressive function. However, a strategy for PD‐L1 deglycosylation in TNBC is poorly defined. Here we found that a saccharide analog, 2‐deoxy‐ d‐glucose (2‐DG), inhibits glycosylation of PD‐L1 and its immunosuppressive function by combining with EGFR inhibitor, gefitinib. Interestingly, 2‐DG/gefitinib‐induced deglycosylation of PD‐L1 decreased the expression level of PD‐L1 protein as well as its binding with PD‐1. However, there was no significant decrease in 4‐1BB expression and its binding with 4‐1BBL by 2‐DG/gefitinib. Furthermore, we demonstrated that the combination treatment of 2‐DG/gefitinib and 4‐1BB antibody enhances antitumor immunity in TNBC syngeneic murine models. Together, our results suggest a new immunotherapeutic strategy to enhance antitumor immunity by PD‐L1 deglycosylation and 4‐1BB stimulation in TNBC.