Up-regulation of Toll-like Receptor 9 in Osteosarcoma.
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BACKGROUND: Increasing evidence has shown that Toll-like receptors (TLRs), key receptors in innate immunity, play a role in cancer development and progression. The present study aimed to elucidate the role of TLR expression in osteosarcoma cancer cells and patient specimens. MATERIALS AND METHODS: We investigated the expression of all of human TLRs in osteosarcoma MG-63 cells by real-time quantitative reverse transcription polymerase chain reaction. We then further explored whether the up-regulation of TLR9 expression is common in patients with osteosarcoma by examining TLR9 protein levels in 80 osteosarcoma specimens and 28 normal controls by immunohistochemistry. RESULTS: We found that among TLR family members, TLR9 was predominately expressed in osteosarcoma cells, and up-regulation of TLR9 expression was found in 72 out of 80 (90%) patients with osteosarcoma but in none of 28 normal controls. Furthermore, high expression of TLR9 appeared to be associated with osteosarcoma progression. CONCLUSION: TLR9 is up-regulated in the majority of osteosarcomas, which appears to play an important role in osteosarcoma development and progression. Therefore, TLR9 may serve as a novel therapeutic target for human osteosarcoma therapy.