Treponema denticola chymotrypsin-like protease as associated with HPV-negative oropharyngeal squamous cell carcinoma

Background An opportunistic oral pathogen, Treponema denticola ( Td ), has been linked to orodigestive carcinogenesis, but its role in oropharyngeal squamous cell carcinoma (OPSCC) has remained open. We evaluated the presence of Td chymotrypsin-like protease ( Td -CTLP) in a series of 201 unselected consecutive OPSCC patients, and the relation of the Td -CTLP to human papillomavirus (HPV) status, to expression of toll-like receptors (TLR) 5, 7, and 9, and to clinical parameters and patient outcome. Methods Clinicopathological data came from hospital registries. The expression of cell surface-bound Td -CTLP was evaluated by immunohistochemistry. Immunoexpression of TLRs 5, 7, and 9, and HPV status we studied earlier in this patient series. Results We detected Td -CTLP in 81% of the OPSCC, and especially in HPV-negative tumours (48% of all OPSCCs). Among the HPV-positive tumours (52% of all OPSCCs), low Td -CTLP expression associated with low TLR 5 and high TLR 7 expression. Among those HPV-negative, higher TLR 5 and lower TLR 7 expression associated with high Td -CTLP expression. Strong Td -CTLP expression associated with poor disease-specific survival, but no similar association among HPV-positive and HPV-negative subgroups emerged. Conclusions Td -CTLP was highly expressed in OPSCC and was associated with the HPV status of tumour tissue.