LSD1 inhibition sensitizes anti-PD1 blockade immunotherapy by inhibiting the long-range attack of tumor-derived extracellular vesicles

Programmed cell death protein-1/programmed cell death ligand-1 (PD1/PD-L1) blockade has shown promise in cancer therapy but remains limited by low response rates. Recent efforts have explored strategies to enhance immunotherapy efficacy. Histone lysine-specific demethylase 1 (LSD1) inhibition can enhance tumor immune responses by downregulating PD-L1 expression. Furthermore, PD-L1 in tumor cell-derived extracellular vesicles (EVs) contributes to the immunosuppressive tumor microenvironment (TME) and promotes immune evasion. Here, we found that LSD1 inhibition can mediate the rearrangement of PD-L1 on tumor cell surfaces, reduce the secretion of EVs and PD-L1 levels in the TME, and ultimately block the long-range immunosuppression caused by tumor cell-released EVs. Therefore, we developed a TME-targeted synergistic therapy system with a dual mechanism in which anti-PD1 therapy blocks immune checkpoints, and forsythiaside A (FA) acts as an LSD1 inhibitor to regulate EVs secretion. Additionally, CD4 + T cells can directly kill tumor cells by inducing G1/S cell cycle arrest. Ultimately, this system activates the tumor immune response within the TME, effectively inhibiting the growth of non-small cell lung cancer tumors. Our work highlights the signaling role of EVs and the capacity of CD4 + T cells to arrest the cell cycle, offering a new approach to enhance response to anti-PD1/PD-L1 therapy. This study highlights the critical role of LSD1 in tumor immunotherapy, underscores the function of EVs as key signaling hubs bridging tumors and T cells, and reveals the direct contribution of CD4 + T cells to tumor clearance.