Dual topology of functional Toll-like receptor 3 expression in human hepatocellular carcinoma: Differential signaling mechanisms of TLR3-induced NF-κB activation and apoptosis
Toll-like receptor 3 (TLR3) is a pattern-recognizing receptor that is involved in immune signaling and plays a crucial role in survival by being able to recognize various viral components including double-stranded RNA (dsRNA). TLR3 expression and function in cancer cells are not well
understood. We investigated the expression of TLR3 in hepatocellular carcinoma (HCC) cells and the function of TLR3 signaling by stimulation and transfection with polyinosinic-polycytidylic acid (Poly I:C), a synthetic form of dsRNA. TLR3 mRNA was expressed in HCC tissues as well as in non-tumor
tissues. Positive immunohistochemical staining for TLR3 was observed in 52.7% of HCC tissues, and in HCC cells we found both membranous and cytoplasmic expression of TLR3. While cell surface stimulation of TLR3 with Poly I:C did not affect cell viability, it did activate NF-κB levels.
In contrast, cytoplasmic stimulation with transfected Poly I:C significantly induced apoptosis accompanied by the down-regulation of anti-apoptotic protein. Transfected Poly I:C also synergistically augmented TRAIL-induced apoptosis, but only with low levels of transfected Poly I:C was IFN-β
production not observed. In conclusion, our results indicate that TLR3 expression in HCC plays an important role with regard to cell survival and proapoptotic activity. Endogenously expressed TLR3 may provide new clinical prospects for TLR3 agonists as cytotoxic agents in HCC.
Document Type: Research Article
Affiliations: Department of Gastroenterology, Mie University Graduate School of Medicine, Tsu, Mie 514-8507, Japan
Publication date: 01 November 2008
- The International Journal of Oncology provides an international forum for the publication of the latest, cutting-edge research in the broad area of oncology and cancer treatment. The journal accepts original high quality works and reviews on all aspects of oncology research including carcinogenesis, metastasis, epidemiology, chemotherapy and viral oncology. Through fair and efficient peer review, the journal is dedicated to publishing top tier research in the field, offering authors rapid publication as well as high standards of copy-editing and production. The International Journal of Oncology is published on a monthly basis in both print and early online.
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