ELF4 and esophageal squamous cell carcinoma: Similarly, exosomal circZNF451 in LUAD promotes ubiquitination of FXR1 and activates the ELF4-IRF4 pathway to induce macrophage polarization and CD8 + T cell dysfunction [33], exosomal circ0048117 under hypoxic conditions can be delivered from esophageal squamous cell carcinoma (ESCC) cells to macrophages and cause M2-type polarization [34].