T regulatory cell markers in oral squamous cell carcinoma: Relationship with survival and tumor aggressiveness

Tumor-infiltrating lymphocytes (TILs) are a heterogeneous cell family which plays an important role in tumor-associated immune response. Of these, T regulatory (Treg) cells have also been shown to inhibit anti-tumor response. We aimed to evaluate the expression of T regulatory cell markers (CD4, CD25, CTLA-4 and FoxP3) in samples of oral cavity squamous cell carcinoma (OCSCC) and lip SCC (LSCC) by immunohistochemistry. The relationship of Treg markers with survival data and the proliferative index were also evaluated. We observed similar numbers of CD4-, CD25- and FoxP3(+) cells in OCSCC and LSCC. On the other hand, numbers of CTLA-4(+) cells were significantly lower in OCSCC than in LSCC. OCSCC samples with high numbers of CD4 exhibited a high proliferative index, while samples with high CTLA-4 counts demonstrated a low tumoral proliferative index. A log-rank test showed that patients with OCSCC that presented high counts of CD4 showed a significantly decreased survival compared with patients with low cell counts. In contrast, high CD25(+) cell counts were associated with increased survival. Our results suggest an association of CD4 with poor prognosis, while CD25 expression is related with favorable prognosis. These findings result from the heterogeneity of TIL subsets that display an antagonistic role in tumor immune cell response.