Effects of transarterial chemoembolization on regulatory T cell and its subpopulations in patients with hepatocellular carcinoma

Background Regulatory T cell (Treg) plays an essential role in regulating anti-tumor immunity. The aim of this study was to investigate the effect of transarterial chemoembolization (TACE) on Treg in hepatocellular carcinoma (HCC) patients. Method The frequency of peripheral blood Tregs in 27 HCC patients who underwent TACE were measured at baseline and 1 month after TACE. The frequency of peripheral blood Tregs at baseline were compared with those in 23 healthy controls. Tregs were further classified into three subpopulations [Treg (I), Treg (II), Treg (III)] based on expression levels or markers and their function. The patients were divided into two groups according to tumor response after TACE; complete response group and incomplete response group. The correlations between the frequency of Treg and clinical factors were analyzed. Results The frequency of Treg in HCC patients (7.52%) was significantly higher than in healthy controls (4.99%) at baseline. Regarding Treg subpopulations, the frequency of Treg (II) was significantly higher in HCC patients (2.51%) than in healthy controls (0.60%). In comparison of Treg numbers at baseline and post-TACE by tumor response, the change of Treg (III) in complete response group from baseline to post-TACE was significantly decreased (63.8 -> 53.2/mm(3)). Patients with a high post-TACE Treg (III) (3.8 months) exhibited a significantly shorter median time to progression than those with a low post-TACE Treg (III) (11.6 months). In multivariate analyses, hypoalbuminemia (hazard ratio 3.324; 95% CI 1.098-10.063, p = 0.034) and high post-TACE Treg (III) (hazard ratio 3.080; 95% CI 1.091-8.696, p = 0.034) were significant factors for associating with progression. Conclusions The frequency of Tregs in HCC patients was significantly higher than in healthy controls. In addition, patients with a high post-TACE Treg (III) exhibited a significantly lower progression-free survival rate than those with a low post-TACE Treg (III).