Prognostic Relevance of CD4+, CD8+ and FOXP3+ TILs in Oral Squamous Cell Carcinoma and Correlations with PD-L1 and Cancer Stem Cell Markers

This study investigates the relevance of tumor-infiltrating lymphocytes (TILs) in oral squamous cell carcinoma (OSCC). Immunohistochemical analysis of stromal/tumoral CD4(+), CD8(+) and FOXP3(+) TILs is performed in 125 OSCC patients. Potential relationships with the expression of tumoral PD-L1 and cancer stem cell (CSC) markers (NANOG, SOX2, OCT4, Nestin and Podoplanin (PDPN)) are assessed. CD4(+) and CD8(+) TILs are significantly associated with smoking and alcohol habits. CD4(+) and CD8(+) TILs show an inverse relationship with NANOG and SOX2 expression, and FOXP3(+) TILs is significantly correlated with Nestin and PDPN expression. High infiltration of CD4(+) and CD8(+) TILs and a high tumoral CD8(+)/FOXP3(+) ratio are significantly associated with tumors harboring positive PD-L1 expression. Infiltration of stromal/tumoral FOXP3(+) TILs and a low stromal CD8(+)/FOXP3(+) ratio are significantly associated with better disease-specific survival. Multivariate analysis reveals that the stromal CD8(+)/FOXP3(+) TILs ratio is a significant independent prognostic factor. Regarding OSCC patient survival, the CD8(+)/FOXP3(+) TILs ratio is an independent prognostic factor. TILs may act as biomarkers and potential therapeutic targets for OSCC.