TLR9 and neoplasm: In communications between tumor and immune cells, exosomes perform a complex role in regulating tumor immunity via specific proteins and genetic components.50 As classical antigen-presenting cells (APCs), dendritic cells (DCs) express a variety of Toll-like receptors (TLRs).51 Evidence supports the involvement of TLRs (e.g., TLR2, TLR4, and TLR9) in PC development.