Role of sialyl 6-sulfo Lewis X in antitumor immunity against oral squamous cell carcinoma.

BACKGROUND: Tumor-infiltrating lymphocytes (TILs) reportedly play a pivotal role in antitumor immunity against oral squamous cell carcinoma (OSCC); however, mechanisms governing TIL recruitment to OSCC tissues remain to be clarified. This study was undertaken to assess a potential association between TILs and high endothelial venule (HEV)-like vessels that express sialyl 6-sulfo Lewis X (LeX).

METHODS: OSCC tissue sections (n=41) were subjected to immunohistochemistry for sialyl 6-sulfo LeX and CD34 to allow quantitation of HEV-like vessels. Triple immunohistochemistry for sialyl 6-sulfo LeX and either CD3 and CD20 or CD4 and CD8 was conducted to determine which lymphocyte subset is more closely associated with HEV-like vessels.

RESULTS: HEV-like vessels expressing sialyl 6-sulfo LeX were detected in 27 of 41 (65.9%) OSCC cases, and these vessels were more frequently found in early disease (T1/T2 stages) compared with advanced (T3/T4) stages. The number of T cells attached to the inner surface of these HEV-like vessels was significantly greater than that of B cells, while the number of CD4+ helper T cells and CD8+ cytotoxic T cells did not differ significantly. Interestingly, sialyl 6-sulfo LeX was also expressed on the membrane of a fraction of OSCC cells, and CD8+ cytotoxic T cells were almost exclusively found attached to these carcinoma cells.

CONCLUSIONS: Sialyl 6-sulfo LeX is displayed not only on HEV-like vessels but also on OSCC cells and may potentially function in antitumor immunity against OSCC.