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TLR7 and TLR8 as targets in cancer therapy

Oncogene volume 27, pages 190–199 (2008)Cite this article

Abstract

Small-molecule agonists at Toll-like receptor 7 (TLR7) and TLR8 have sparked a vivid interest in cancer research owing to their profound antitumoral activity. The lead compound of the imidazoquinoline family, imiquimod, is marketed as a topical formulation. It is efficacious against many primary skin tumors and cutaneous metastases. Using different imidazoquinoline species, distinct functions of TLR7 and TLR8 have been discovered. The predominant antitumoral mode of action of these agents is TLR7/8-mediated activation of the central transcription factor nuclear factor-κB, which leads to induction of proinflammatory cytokines and other mediators. Cutaneous dendritic cells are the primary responsive cell type and initiate a strong Th1-weighted antitumoral cellular immune response. Recent research has shown that dendritic cells themselves acquire direct antitumoral activity upon stimulation by imiquimod. In addition, there are a number of secondary effects on the molecular and cellular level that can be explained through the activation of TLR7/8. The proinflammatory activity of imiquimod, but not resiquimod, appears to be augmented by suppression of a regulatory mechanism, which normally limits inflammatory responses. This is achieved independently of TLR7/8 through interference with adenosine receptor signaling pathways. Finally, at higher concentrations imiquimod exerts Bcl-2- and caspase-dependent proapoptotic activity against tumor cells.

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Acknowledgements

This work was supported by a research grant from the Dr Mildred Scheel Stiftung/Deutsche Krebshilfe (10-2196 Schö-2) to MS and MPS, and by a Rudolf Virchow Award from the Deutsche Forschungsgemeinschaft to MPS.

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  1. DFG Research Center for Experimental Biomedicine and Department of Dermatology, Rudolf Virchow Center, Julius-Maximilians-University, Würzburg, Germany

    M P Schön & M Schön

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  1. M P Schön
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  2. M Schön
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Correspondence to M P Schön.

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Schön, M., Schön, M. TLR7 and TLR8 as targets in cancer therapy. Oncogene 27, 190–199 (2008). https://doi.org/10.1038/sj.onc.1210913

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