Toll-like receptors in lymphoid malignancies: double-edged sword

Toll-like receptors (TLRs) are the best characterized pattern recognition receptors (PRRs), which play an essential role in the recognition of invading pathogens via specific microbial molecular motifs, comprising a bridge between the innate and adaptive immune responses. Toll-like receptors expression is determined in both normal immune cells and malignant cells, with a distinctive pattern compared to each other, rendering them plausible targets for cancer therapy. Improved molecular profiling of lymphoid malignancies may give new insights into pathogenesis of these cancers and pave the way for novel therapeutic agents, including TLR agonists. In the current review, we summarize the immunopathogenic roles of TLRs in B cell and T cell lymphomas, acute lymphoblastic leukemia, multiple myeloma, and chronic lymphocytic leukemia, as well as the results of studies on TLR ligands and their future implications to manage these hematologic malignancies.