Blocked Autophagy is Involved in Layered Double Hydroxide‐Induced Repolarization and Immune Activation in Tumor‐Associated Macrophages

Tumor-associated macrophages (TAMs) are important immune cells in the tumor microenvironment (TME). The polar plasticity of TAMs makes them important targets for improving the immunosuppressive microenvironment of tumors. The previous study reveals that layered double hydroxides (LDHs) can effectively promote the polarization of TAMs from the anti-inflammatory M2 type to the pro-inflammatory M1 type. However, their mechanisms of action remain unexplored. This study reveals that LDHs composed of different cations exhibit distinct abilities to regulate the polarity of TAMs. Compared to Mg-Fe LDH, Mg-Al LDH has a stronger ability to promote the repolarization of TAMs from M2 to M1 and inhibit the formation of myeloid-derived suppressor cells (MDSCs). In addition, Mg-Al LDH restrains the growth of tumors in vivo and promotes the infiltration of activated immune cells into the TME more effectively. Interestingly, Mg-Al LDH influences the autophagy of TAMs; this negatively correlates with the pro-inflammatory ability of TAMs. Therefore, LDHs exert their polarization ability by inhibiting the autophagy of TAMs, and this mechanism might be related to the ionic composition of LDHs. This study lays the foundation for optimizing the performance of LDH-based immune adjuvants, which display excellent application prospects for tumor immunotherapy.