Radiochemotherapy upregulates expression of checkpoint receptors on circulating T cells

This study assesses changes of circulating leukocyte subpopulations and the expression of checkpoint receptors in T cells in patients undergoing radiochemotherapy.

Fifty-seven patients with either esophageal cancer or cervical cancer who received radiochemotherapy were recruited into this study. Serial blood collection was carried out before and during treatments. Leukocyte subpopulations and the level of PD-1 and CTLA-4 in T cells were determined by flow cytometry. The plasma concentrations of 34 human cytokines, chemokines, and growth factors were quantified.

Significant decreases of lymphocyte count and percentage of T cells and B cells were observed during radiochemotherapy. Percentages of PD-1^hi and CTLA-4^hi populations in T cells increased after treatments. Proportion of activated T cells showed no significant difference. No significant changes in the plasma concentrations of the 34 humoral mediators except mild decreases of six cytokines.

Elevated expression of PD-1 and CTLA-4 in T cells in patients receiving radiochemotherapy, which suggests that exhaustion-like T-cell dysfunction develops during cancer cytotoxic treatments.