The expression of TLR9 was measured in different CRC cell lines and cancerous samples by RT-PCR or immunohistochemistry, which showed that high expression of TLR9 was significantly correlated with the tumor metastasis, advanced TNM stage and poor prognosis of patients.
Our results suggest that bacterial DNA as well as deoxynucleotides having stable secondary structures (i.e. hairpins or G-quadruplex structures) may serve as endogenous, invasion-inducing TLR9-ligands and promote local progression and metastasis of cancers in the alimentary tract.
All squamous cell carcinomas exhibited TLR9 expression that was positively associated with a high grade (p < 0.05), the presence of lymph node metastases (p < 0.05) and previously undetected distant metastases (p < 0.05).
Overall, TLR9 up-regulates COX-2 expression in prostate cancer cells, at least partially through the activation of NF-kappaB, which may be implicated in tumor invasion and metastasis.