microRNAs (miRNAs) are aberrantly expressed in the whole blood of patients suffering from different types of cancer. Collection of whole blood samples is a minimally invasive procedure. To date, little is known concerning the altered miRNA expression in patients suffering from oral squamous cell carcinoma (OSCC). The present study aimed to evaluate the difference in miRNA expression in whole blood samples in OSCC patients as compared to healthy volunteers who served as controls. In 20 blood samples from patients and healthy volunteers, the expression patterns of 1,205 human miRNAs were examined by miRNA microarray in order to identify those with the most pronounced differential expression. The results were verified by quantitative RT-PCR (RT-qPCR) for miR-186, miR-3651 and miR-494 using 57 samples of patients and 33 samples of healthy volunteers. Receiver operating characteristic (ROC) curves and the highest Youden index were calculated in order to assess cut-off points (COPs) that allowed the distinguishing of blood samples of OSCC patients from those of healthy volunteers. Significantly different expression rates were found for miR-186 (p=0.01), miR-3651 (p=0.0001) and miR-494 (p=0.004) between the OSCC patients and healthy controls. In the OSCC patients, there was a 2-fold upregulation for miR-494 and miR-3651 and a 2-fold downregulation for miR-186. Based on the determined COPs, significant correlations between miR-3651 overexpression and lymph node status (p=0.04), tumor grade (p=0.02) and clinical stage (p=0.04) were indicated. Aberrant expression levels of miR-186, miR-494 and miR-3651 in whole blood samples of OSCC patients may provide the possibility to establish a minimally invasive screening method for OSCC.

BackgroundImmune checkpoints like programmed cell death-1 (PD-1) and its ligand PD-L1 are involved in immune escape mechanisms of solid tumors including oral squamous cell carcinoma (OSCC). Inhibitors of the pathway are successfully used for treating especially advanced disease. However, the physiological relevance of PD-1/PD-L1-signaling in OSCC is insufficiently understood. The aim of the study was to analyze if PD-L1 expression in tumor tissue and peripheral blood samples of OSCC patients is associated with histomorphological tumor parameters and if PD-L1 expression in patients is different from controls.ResultsOSCC tumor specimens showed a significantly higher PD-L1 expression than oral mucosa controls (p < 0.001; upregulation more than 3-fold). Cross-tabulation revealed an association of increased expression of PD-L1 mRNA in tissue specimens with malignancy (p < 0.001).OSCC cases with higher tumor grade and cases with lymph node metastases (N+) were significantly (p < 0.05) associated with increased PD-L1 expression in peripheral blood. Cross-tabulation revealed an significant association with lymph node metastases (N+) (p ≤ 0.002).Materials and MethodsPD-L1 mRNA expression was analyzed in tumor specimens and corresponding samples of healthy oral mucosa and peripheral blood of 45 OSCC patients and 36 healthy control persons using RT-qPCR analysis. A Mann-Whitney U-test, a cut-off point analysis and a Chi-square test were carried out.ConclusionsPD-L1 expression in OSCC could contribute to the immunosuppressive local tumor microenvironment. Increased malignant behavior (higher tumor grade, positive nodal status) might be associated with PD-L1 mediated systemic immune tolerance. Thus, PD-L1 expression in peripheral blood might be an indicator of the existence of metastatic disease (N+) in OSCC.

Background: Most oral squamous cell carcinomas (OSCC) occur on the basis of oral leukoplakias (OLP). The histologic degree of dysplasia is insufficient for the prediction of OLP malignant transformation. Immunologic parameters are gaining importance for prognostic assessment and therapy of cancer. M2 polarized macrophages were shown to be associated with OSCC progression and inferior prognosis. The current study aims to answer the question if OLP with malignant transformation into OSCC within 5 years differ from OLP without transformation regarding macrophage infiltration and polarization.Methods: 201 specimens (50 transforming OLP, 53 non-transforming OLP, 49 corresponding OSCC and 49 healthy oral mucosa controls) were processed for immunohistochemistry. Samples were stained for CD68, CD163 and CD11c expression, completely digitalized and computer-assisted cell counting was performed. Epithelial and subepithelial compartments were differentially assessed. Groups were statistically compared using the Mann-Whitney U-test. A cut-off point for the discrimination of transforming and non-transforming OLP was determined and the association between macrophage infiltration and malignant transformation was calculated using the Chi-square test (χ 2 test). Results:Macrophage infiltration and M2 polarization in OLP with malignant transformation within 5 years was significantly increased compared to OLP without malignant transformation (p < 0.05). OSCC samples showed the highest macrophage infiltration and strongest M2 polarization (p < 0.05). Additionally, transforming OLP revealed a significant shift of macrophage infiltration towards the epithelial compartment (p < 0.05). χ 2 test revealed a significant association of increased macrophage infiltration with malignant transformation (p < 0.05). Conclusion:Immunological changes precede malignant transformation of OLP. Increased macrophage infiltration and M2 polarization was associated with the development of oral cancer in OLP. Macrophage infiltration could serve as predictive marker for malignant transformation.

Background: The programmed cell death ligand 1/programmed cell death receptor 1 (PD-L1/PD-1) Immune Checkpoint is an important modulator of the immune response. Overexpression of the receptor and its ligands is involved in immunosuppression and the failure of an immune response against tumor cells. PD-1/PD-L1 overexpression in oral squamous cell carcinoma (OSCC) compared to healthy oral mucosa (NOM) has already been demonstrated. However, little is known about its expression in oral precancerous lesions like oral leukoplakia (OLP). The aim of the study was to investigate whether an increased expression of PD-1/PD-L1 already exists in OLP and whether it is associated with malignant transformation. Material and Methods: PD-1 and PD-L1 expression was immunohistologically analyzed separately in the epithelium (E) and the subepithelium (S) of OLP that had undergone malignant transformation within 5 years (T-OLP), in OLP without malignant transformation (N-OLP), in corresponding OSCC and in NOM. Additionally, RT-qPCR analysis for PD-L1 expression was done in the entire tissues. Additionally, the association between overexpression and malignant transformation, dysplasia and inflammation were examined. Results: Compared to N-OLP, there were increased levels of PD-1 protein in the epithelial and subepithelial layers of T-OLP (pE = 0.001; pS = 0.005). There was no significant difference in PD-L1 mRNA expression between T-OLP and N-OLP (p = 0.128), but the fold-change increase between these groups was significant (Relative Quantification (RQ) = 3.1). In contrast to N-OLP, the PD-L1 protein levels were significantly increased in the epithelial layers of T-OLP (p = 0.007), but not in its subepithelial layers (p = 0.25). Importantly, increased PD-L1 levels were significantly associated to malignant transformation within 5 years. Conclusion: Increased levels of PD-1 and PD-L1 are related to malignant transformation in OLP and may represent a promising prognostic indicator to determine the risk of malignant progression of OLP. Increased PD-L1 levels might establish an immunosuppressive microenvironment, which could favor immune escape and thereby contribute to malignant transformation. Hence, checkpoint inhibitors could counteract tumor development in OLP and may serve as efficient therapeutic strategy in patients with high-risk precancerous lesions.

Currently, there is a lack of blood markers for the detection of recurrent oral squamous cell carcinoma (OSCC). The present study aimed to investigate whether the aberrant expression of single microRNAs (miRNAs) in whole blood of patients could serve as a biomarker for persistent or recurrent OSCC. Whole blood of 2 groups of formerly treated OSCC patients was investigated by RT-qPCR for their circulating miRNA profiles. The R-OC group included patients with recurrence of OSCC (n=21) and the NR-OC group included patients without recurrence (n=21). Fold-changes and significance of the differences in miRNA expression levels between the groups were determined. A cut-off point (COP) for the discrimination between the R-OC and NR-OC groups was calculated and the significance between over/under expression of the miRNAs and the recurrence of malignancy was determined. Significant differences in the miRNA expression in whole blood of the R-OC and NR-OC groups were found. The levels of miR-3651 and miR-494 were significantly increased and the level of miR-186 was significantly decreased in whole blood of the R-OC patients (pmiR-3651=0.001, pmiR-494=0.003 and pmiR-186=0.001). By the determination of the COP, increased or decreased expression of the markers was significantly correlated to the recurrence of the disease. Altered expression of miR-494, miR-3651 and miR-186 appears to be associated with the recurrence of OSCC. The present study may form the basis for establishing a blood test as a minimally invasive method for the detection of the recurrence of OSCC.