Chemokine Receptor 7, A New Player in Regulating Apoptosis of CD8+ T Cells in Cancer Patients

The immune signature of CD8(+)CCR7(+) T cells in the peripheral circulation associates with disease recurrence in patients with HNSCC

PURPOSE

Patients with cancer have an increased frequency of circulating apoptosis-sensitive CD8(+)CCR7(neg) T cells and few CD8(+)CCR7(+) T cells versus normal controls. The functional and clinical significance of this imbalance was investigated using peripheral blood of patients with squamous cell carcinoma of the head and neck (HNSCC).

EXPERIMENTAL DESIGN

The frequency of circulating CD8(+) T cells co-expressing CCR7, CD45RO, CD28, and Annexin V (ANXV) was evaluated in 67 patients and 57 normal controls by flow cytometry. Spearman rank correlations among immunophenotypic profiles were analyzed. Recursive partitioning classified subjects as patients or normal controls based on CD8(+)CCR7(+) T-cell percentages. Kaplan-Meier plots estimated disease-free survival (DFS).

RESULTS

The CD8(+)CCR7(+) T-cell frequency was low, whereas that of total CD8(+)CCR7(neg) and ANXV-binding CD8(+)CCR7(neg) T cells was higher in patients with HNSCC than in normal controls (P < 0.001-0.0001). ANXV binding correlated with the absence of CCR7 on CD8(+) T cells (P < 0.001). ANXV binding was negatively correlated with the CD8(+)CD45RO(neg)CCR7(+) (T(N)) cell frequency (P < 0.01) but positively correlated (P < 0.01) with that of CD8(+)CD45RO(+)CCR7(+) (T(CM)) T cells and of the two CCR7(neg) subsets (T(PM) and T(TD)). In recursive partitioning models, the CD8(+)CCR7(+) T-cell frequency of 31% distinguished patients from normal controls with 77% to 88% accuracy after cross-validation. In 25 patients tested before any therapy, the CD8(+)CCR7(+) T-cell frequency of less than 28% predicted disease recurrence within 4 years of definitive therapy (P < 0.0115).

CONCLUSION

The CD8(+)CCR7(+) T-cell frequency in HNSCC patients' blood tested at diagnosis can discriminate them from normal controls and predicts disease recurrence.

Hypoxia induces T-cell apoptosis by inhibiting chemokine C receptor 7 expression: the role of adenosine receptor A(2)

Hypoxia is a major characteristic of the tumor microenvironment, and its effects on immune cells are proposed to be important factors for the process of tumor immune escape. It has been reported that hypoxia affects the function of dendritic cells and the antitumor function of T cells. Here we discuss the effects of hypoxia on T-cell survival. Our results showed that hypoxia induced apoptosis of T cells. Adenosine and adenosine receptors (AR) are important to the hypoxia-related signaling pathway. Using AR agonists and antagonists, we demonstrated that hypoxia-induced apoptosis of T cells was mediated by A(2a )and A(2b) receptors. Furthermore, we are the first, to our knowledge, to report that hypoxia significantly inhibited the expression of chemokine C receptor 7 (CCR7) of T cells via the A(2)R signal pathway, perhaps representing a mechanism of hypoxia-induced apoptosis of T cells. Collectively, our research demonstrated that hypoxia induces T-cell apoptosis by the A(2)R signaling pathway partly by suppressing CCR7. Blocking the A(2)R signaling pathway and/or activation of CCR7 can increase the anti-apoptosis function of T cells and may become a new strategy to improve antitumor potential.

Tumor microenvironment and immune escape

This article describes the multiple escape mechanisms used by tumor cells to avoid T-cell-mediated recognition and destruction. The discussion focuses on escape mechanisms that may result from changes at the level of TA-specific cytotoxic T lymphocytes and tumor cells in the tumor microenvironment. Specifically, we discuss the negative impact of regulatory T cells and T-cell apoptosis on the tumor antigen-specific cytotoxic T lymphocyte response. We also discuss changes in the expression of histocompatibility antigens by tumor cells, which may affect tumor cell-immune cell interactions.