BACKGROUND: Lately, immune checkpoint proteins, such as programmed death 1 (PD-1) and its ligand-1 (PD-L1), have garnered attention as a new target in oral squamous cell carcinoma (OSCC). Reportedly, fluoro-D-glucose (FDG)-uptake alteration by anti-PD-1 antibody treatment depicts the response in patients with lung cancer. This study aims to elucidate the correlations between tumour immune status, clinicopathological factors, 18 F-FDG-uptake and cold tumour phenotypes as low PD-L1 expression/low CD8 + tumour-infiltrating lymphocytes (TILs) in OSCC. METHODS: We performed immunohistochemical analysis of PD-L1, hypoxia-inducible factor 1 A (HIF-1A), glucose transporter type 1 (GLUT1), CD8, E-cadherin and Ki-67 on 59 operable OSCC samples. We assessed the correlations between these factors and preoperative 18 F-FDG-uptake, clinicopathological characteristics and prognosis. RESULTS: Low expression of PD-L1 in OSCC correlated with cancer aggressiveness, poor prognosis, high 18 F-FDG-uptake with HIF-1A/GLUT1 and low E-cadherin expression and low CD8. Cold tumour phenotypes as low PD-L1 tumour cells and low stromal CD8 correlated with the poor prognosis, high 18 F-FDG-uptake and E-cadherin suppression. Furthermore, the high level of preoperative 18 F-FDG-uptake in OSCC was an independent predictor of the cold tumour immune status. CONCLUSIONS: 18 F-FDG-uptake is an independent predictor of cold tumour in OSCC. 18 F-FDG-PET imaging could be a promising diagnostic tool to estimate tumour immune status.

Claudins (CLDNs) are key cell adhesion molecules, which compose tight junctions (TJs), and the disruption of TJs is associated with cancer development. Here we immunohistochemically studied expression patterns of CLDNs in 222 primary invasive breast cancers including 68 triple-negative breast cancers (TNBCs), and examined their correlation with epithelial-to-mesenchymal transition (EMT)-related markers, breast cancer stem cell (BCSC) markers, and clinicopathological features including patients' clinical outcome. Tumor margins were classified as three infiltrating growth patterns (expanding, intermediate and infiltrating). For CLDN1, 3, 4, and 7, their expression rates were more frequent in TNBCs than in other subtypes (11.8% vs 0.7%, 26.5% vs 2.0%, 48.5% vs 11.1%, and 32.4% vs 8.7%, respectively; P ≤ 0.001). In 68 TNBCs, we identified high Ki67 labeling index (LI) and the combination of CLDN4 high/CLDN7 low expression as independent predictors of axillary nodal metastasis (P = 0.019; OR, 4.36; 95%CI, 1.28-14.90 and P = 0.007; OR, 5.33; 95%CI, 1.58-17.90). Moreover, the combination of CLDN1 low/CLDN7 low/E-cadherin negative as well as tumor infiltrating patterns were predictors for worse recurrence-free survival by univariate analyses in TNBCs (P = 0.005 and P = 0.011). Our analyses provide further evidence that CLDNs would be valuable prognostic markers in TNBCs.