CXCR6 and CCR5 localize T lymphocyte subsets in nasopharyngeal carcinoma

Abstract

The substantial T lymphocyte infiltrate found in cases of nasopharyngeal carcinoma (NPC) has been implicated in the promotion of both tumor growth and immune escape. Conversely, because malignant NPC cells harbor the Epstein-Barr virus, this tumor is a candidate for virus-specific T cell-based therapies. Preventing the accumulation of tumor-promoting T cells or enhancing the recruitment of tumor-specific cytotoxic T cells offers therapeutic potential. However, the mechanisms involved in T cell recruitment to this tumor are poorly understood. Comparing memory T cell subsets that have naturally infiltrated NPC tissue with their counterparts from matched blood revealed enrichment of CD8(+), CD4(+), and regulatory T cells expressing the chemokine receptor CXCR6 in tumor tissue. CD8(+) and (nonregulatory) CD4(+) T cells also were more frequently CCR5(+) in tumor than in blood. Ex vivo studies demonstrated that both receptors were functional. CXCL16 and CCL4, unique chemokine ligands for CXCR6 and CCR5, respectively, were expressed by the malignant cells in tumor tissue from the majority of NPC cases, as was another CCR5 ligand, CCL5. The strongest expression of CXCL16 was found on tumor-infiltrating cells. CCL4 was detected on the tumor vasculature in a majority of cases. These findings suggest that CXCR6 and CCR5 play important roles in T cell recruitment and/or retention in NPC and have implications for the pathogenesis and treatment of this tumor.