Distinct expression patterns of Toll-like receptor 7 in tumour cells and fibroblast-like cells in oral squamous cell carcinoma.

Aims: Toll-like receptor (TLR)-7 agonists have been used in cancer immunotherapy, but tumour heterogeneity means that TLR-7 activity is variable in different components of the tumour microenvironment and the characteristics of TLR-7 in oral squamous cell carcinoma (OSCC) are unclear.

Methods And Results: Twenty healthy oral tissues, 50 oral leukoplakia tissues and 166 retrospective primary OSCC samples were collected for immunohistochemical staining of TLR-7 and showed up-regulated expression during carcinogenesis. Moreover, patients with high expression of TLR-7 in tumour cells (TCs) had poor differentiation and prognosis. Interestingly, patients with high expression of TLR-7 in stroma fibroblast-like cells (FLCs) had low tumour stage, no lymph node metastasis (LNM) and better prognosis. Furthermore, Ki-67, CD3, CD4, CD8 and forkhead box protein 3 (FoxP3)(+) tumour-infiltrated lymphocytes were assessed and we found that TLR-7(high) TCs were infiltrated by fewer CD3(+) CD4(+) but more FoxP3(+) lymphocytes. Importantly, patients with TLR-7(low) TCs and TLR-7(high) FLCs had less FoxP3(+) lymphocyte infiltration and longer survival time than those with TLR-7(high) TCs/TLR-7(low) FLCs, although TLR-7 was not an independent prognostic factor for OSCC.

Conclusions: The low expression of TLR-7 in tumour and high expression of TLR-7 in stroma predict a good clinical outcome for OSCC patients, and stroma FLCs might be amenable to immunotherapy by a TLR-7 agonist.