Bidirectional interaction between epithelial-mesenchymal transition and PD-1/PD-L1 expression in tongue carcinogenesis.

Objective: To investigate, through immunohistochemistry, the interaction between epithelial-mesenchymal transition (EMT) and the immune checkpoint proteins PD-1 and PD-L1 in oral tongue squamous cell carcinoma (OTSCC).

Design: The EMT status was determined based on the immunostaining of E-cadherin and N-cadherin proteins. EMT status and the immunoexpression of PD-L1 and PD-1 were analyzed semiquantitatively in 61 cases of OTSCC, and the cases were categorized into low and high expression groups for association with clinicopathological variables and overall survival (OS) and disease-free survival (DFS) rates.

Results: A predominance of cases with positive EMT status was identified (75.4 %), with a statistically significant association between histological grade of malignancy and the occurrence of EMT (p = 0.003). Regarding the clinical parameters analyzed, a statistically significant difference was observed between OTSCC cases with larger sizes and higher levels of PD-L1 expression (p = 0.048). Additionally, the immunoexpressions of the PD-1 and PD-L1 proteins were higher in cases with positive EMT status (p = 0.003 and p = 0.001, respectively), as well as a moderate, positive, and statistically significant correlation between the immunoexpression scores of PD-1 and PD-L1 proteins (r = 0.571; p < 0.001).

Conclusion: The results of the present study suggest the potential involvement of EMT in the modulation of an immunosuppressive microenvironment in OTSCC.