Association between circulating CD39+CD8+ T cells pre-chemoradiotherapy and prognosis in patients with nasopharyngeal carcinoma.

BACKGROUND: The mortality rate among patients with nasopharyngeal carcinoma (NPC) has improved significantly with the advent of chemoradiotherapy strategies. However, distant metastasis remains problematic. Tumor-specific reactivity in cancer patients has been detected exclusively in CD39+ T cells, particularly in CD39+CD103+ T cells. Circulating cancer-specific T cells are important for protecting against metastasis. This study aimed to evaluate the predictive value of circulating CD39+CD8+ T cells for metastasis in patients with NPC. METHODS: We performed a cross-sectional, longitudinal study of 55 patients with newly diagnosed NPC of stage III-IVa. All patients were initially treated with standard combined chemoradiotherapy. Blood samples were obtained from 24 patients before and at 1 month and 6 months after treatment. T cell expression of CD39 and CD103, together with the markers of T cell exhaustion programmed death-1 (PD-1)/T cell immunoglobulin and mucin domain-containing protein 3 (Tim-3) and markers of cell differentiation CD27/CC-chemokine receptor 7/CD45RA, was examined by flow cytometry. The Wilcoxon rank-sum test analysis was used to analyze the differences between two groups. Kaplan-Meier analysis was used for analysis of progression-free survival (PFS). RESULTS: The expression of circulating CD39+CD8+ and CD39+CD103+ CD8+ T cells was significantly higher in patients without distant metastasis (CD39+CD8+: 6.52% [1.24%, 12.58%] vs. 2.41% [0.58%, 5.31%], Z=-2.073, P=0.038 and CD39+CD103+CD8+: 0.72% [0.26%, 2.05%] vs. 0.26% [0.12%, 0.64%], Z=-2.313, P = 0.021). Most CD39+ T cells did not express PD-1 or Tim-3. Patients with high expression of CD39+CD103+CD8+ T cells had better PFS than patients with low expression (log rank value = 4.854, P = 0.028). CD39+CD8+ T cells were significantly elevated at 1-month post-treatment (10.02% [0.98%, 17.42%] vs. 5.91% [0.61%, 10.23%], Z = -2.943, P = 0.003). The percentage of advanced differentiated CD8+ T cells also increased at 1-month post-treatment compared with pre-treatment (33.10% [21.60%, 43.05%] vs. 21.00% [11.65%, 43.00%], Z = -2.155, P = 0.031). There was a significant correlation between elevated CD39+CD8+ T cells and increased effector memory T cells (intermediate stage: r = 0.469, P = 0.031; advanced stage: r = 0.508, P = 0.019). CONCLUSIONS: CD39+CD8+ circulating T cells have preserved effector function, contributing to an improved prognosis and a reduced risk of metastasis among NPC patients. These cells may thus be a useful predictive marker for a better prognosis in patients with NPC.