CD8+ and CD163+ infiltrating cells and PD‐L1 immunoexpression in oral leukoplakia and oral carcinoma

Overexpression of inhibitory checkpoint PD1/PD‐L1 plays an important role in carcinogenesis and patients prognosis. 70 cases of oral squamous cell carcinoma (OSCC), 23 cases of oral leukoplakia (OLK), and 19 control cases were immunohistochemically stained with anti‐PD‐L1, ‐CD8, and ‐CD163 antibodies. PD‐L1 was expressed on dysplastic and subepithelial infiltrating cells of OLK as well as on cancer and tumor‐infiltrating cells of OSCC. In OSCC, PD‐L1 immunoexpression was significantly increased in comparison to OLK, and control groups. The correlative study showed significant correlations between the immunoexpression of PD‐L1 and the number of CD8+, CD163+ cells in both OLK and OSCC groups. We found also significant negative correlation between the number of PD‐L1+ infiltrating cells and the number of CD8+ cells in OSCC, and positive correlation between the number of PD‐L1+ infiltrating cells and CD163+ cells in OLK and OSCC groups. In conclusion, our study indicate that CD163+ and CD8+ infiltrating cells influence the early and subsequent stages of oral carcinogenesis. We demonstrated also that studied tumors may evade the host immune system by PD‐L1 immunoexpression not only on epithelial cells but on infiltrating cells as well.