Toll-Like Receptor 3 as a Recurrence Risk Factor and a Potential Molecular Therapeutic Target in Colorectal Cancer

Colorectal cancer (CRC) often recurs after curative resection. Identification of major risk factors for CRC recurrence is important for effective prevention and treatment. In this study, we examined the potential relationship between CRC and TLR3 as this remains unclear.

Correlations between TLR3 immunostaining and clinicopathological factors and prognosis were examined in 50 samples that were randomly extracted from 264 patients with CRC from January 2010 to December 2011. Chemokines induced by TLR3 agonist stimulation were also examined using TLR3-positive human CRC cell lines. Furthermore, the association between TLR3 and chemokine expression was assessed by analyzing the immunohistochemistry of surgical specimens.

Of the 50 patients, 14 (28%) were TLR3-negative. In the comparison of clinicopathological factors between the TLR3-negative and -positive groups, there were more lymph node metastasis-positive cases in the TLR3-negative group, and this difference was significant. Furthermore, there was no difference in overall survival rates between the two groups, but the 5-year recurrence-free survival (RFS) was significantly lower in the TLR3-negative group (46.2%) than in the TLR3-positive group (78.1%). Analysis of 5-year RFS using factors thought to be related to recurrence identified a high tumor budding and a TLR3-negative status as independent risk factors for recurrence. TLR3 activation of CRC cell lines induced expression of C-C motif chemokine ligand 2 (CCL2), C-C motif chemokine ligand 5 (CCL5), and interleukin-8. The expressions of CCL2, CCL5, and IL-8 were observed in the TLR3-positive tumor cells of surgical specimens.

Non-expression of TLR3 in CRC cells was associated with lymph node metastasis and was an independent risk factor for recurrence. These results suggest that TLR3 may not only be used as a prognostic factor and a risk factor for recurrence, but further studies on the involvement of TLR3 with tumor growth may provide new therapeutic strategies.