Up-regulation of Toll-like Receptor 9 in Osteosarcoma

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. 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. 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. 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.