Oral Squamous Carcinoma Cells Express B7-H1 and B7-DC Receptors in Vivo.

B7-H1 and B7-DC ligands are members of the B7 family with important regulatory functions in cell-mediated immune response. Both receptors are ligands of the programmed death receptor PD-1. B7-H1 expression has been detected in the majority of human carcinomas in vivo. B7-H1 mediated signals are able to negatively regulate activated T cell functions and survival, and enable tumor cells to overcome host response. The aim of this study was to investigate the expression of B7-H1 and B7-DC proteins in oral squamous cell carcinomas (OSCC) in vivo. Tissues from 15 samples were cryo-sected and following histological routine staining (HE), incubated with antibodies against human B7-H1 and B7-DC. Immuno-staining of pan-cytokeratin was performed to ascertain the epithelial origin of the tissue and CK 19 to demonstrate the proliferating stage. Confocal laser scanning microscopy confirmed the presence of both B7-H1 and B7-DC in all 15 OSCC. The B7-H1 and B7-DC staining was located in areas of the tissue that were identified as cancerous lesions in the previously stained HE sections before. Staining with Pan-CK and CK19 provided evidence for the epithelial origin and the proliferating stage of the tissue. The in vivo expression of the B7-H1 and B7-DC receptors in oral squamous cell carcinomas suggest that general mechanisms for immune evasion of tumors are also found in OSCC.