Department of Gastroenterology, Mie Graduate University School of Medicine, Tsu, Mie 514-8507, Japan.
Int J Oncol. 2010 Oct;37(4):805-14.
Toll-like receptor 9 (TLR9) is a pattern-recognition receptor that is involved in immune signaling and plays a crucial role in cell survival through recognition of various bacterial and viral components including unmethylated CpG-DNA. TLR9 expression and function in cancer cells are not well understood. We investigated the expression of TLR9, and the function of TLR9 signaling, in hepatocellular carcinoma (HCC) cells following stimulation with CpG-oligodeoxynucleotides (ODNs). Positive immunohistochemical staining for TLR9 was observed in 85.7% of HCC tissues. Western blot analysis revealed that TLR9 was expressed both on the cell membrane and in the cytoplasm of HCC cell lines. Full-length TLR9 was predominantly expressed on the membrane rather than in the cytoplasm, whereas multiple cleaved forms of TLR9 were predominantly expressed in the cytoplasm rather than on the membrane. Cell surface stimulation of TLR9 promoted cell proliferation, and, furthermore, the TLR9 agonists, CpG-ODNs, reduced the cytotoxicity of the anti-cancer drug adriamycin (ADM) via up-regulation of apoptosis inhibitors such as survivin, Bcl-xL, XIAP and cFLIP, in HCC cell lines. Although cell surface stimulation of TLR9 did not activate either the NF-kappaB signaling pathway or the type-I IFN secretion pathway, gene chip microarray analysis indicated that TLR9 agonists closely regulated multiple oncology-related genes and transcription factors involved in tumorigenesis and cancer progression. In conclusion, our results indicate that functional cell surface expression of TLR9 in human HCC may play an important role in tumorigenesis and cancer progression.
Toll 样受体 9（TLR9）是一种模式识别受体，参与免疫信号转导，通过识别各种细菌和病毒成分（包括未甲基化的 CpG-DNA）在细胞存活中发挥关键作用。TLR9 在癌细胞中的表达和功能尚未得到很好的理解。我们研究了 CpG-寡脱氧核苷酸（ODNs）刺激后肝癌（HCC）细胞中 TLR9 的表达和 TLR9 信号转导的功能。85.7%的 HCC 组织中 TLR9 的免疫组织化学染色呈阳性。Western blot 分析显示 TLR9 在 HCC 细胞系的细胞膜和细胞质中均有表达。全长 TLR9 主要表达在细胞膜上，而不是细胞质中，而多个切割形式的 TLR9 主要表达在细胞质中，而不是细胞膜上。TLR9 的细胞表面刺激促进细胞增殖，并且 TLR9 激动剂 CpG-ODNs 通过上调凋亡抑制剂（如 survivin、Bcl-xL、XIAP 和 cFLIP）降低抗癌药物阿霉素（ADM）的细胞毒性，在 HCC 细胞系中。尽管 TLR9 的细胞表面刺激并未激活 NF-κB 信号通路或 I 型 IFN 分泌通路，但基因芯片微阵列分析表明 TLR9 激动剂密切调节了多个与肿瘤发生和癌症进展相关的肿瘤学相关基因和转录因子。总之，我们的结果表明，人 HCC 中功能性细胞表面 TLR9 的表达可能在肿瘤发生和癌症进展中发挥重要作用。
