PD-L1 Expression in Oral Squamous Cell Carcinoma and Circulating Tumor Cells: Prognostic Significance

Oral squamous cell carcinoma (OSCC) is the most common type of malignant tumor of the oral cavity and has been associated with bad prognosis. The aim of this study is to verify differences in expression between tumors of different T stages, looking for genes with either an increase or decrease through T1 to T4 stages. Thirty six frozen samples representing all tumor size stages (T1, T2, T3 and T4) were analyzed using whole genome cDNA microarrays. Selected genes were analyzed in a different cohort by immuohistochemistry and in circulating tumor cells (CTCs) by immunofluorescence and Nanostring. A significant correlation was shown between PD-L1 and tumor size and lymph node metastasis. We also found correlation between the expression of HOXB9 and tumor size, BLNK and perineural invasion, and ZNF813 and perineural invasion. Immunohistochemical expression of PD-L1 was shown to be an independent prognostic factor, increasing by 40% the chance of death in this cohort (p = 0.044, HH = 0.426, 95% CI: 0.186 to 0....