Preliminary investigation on the abnormal mechanism of CD4+FOXP3+CD25high regulatory T cells in pediatric B‑cell acute lymphoblastic leukemia

Abstract

The current study aimed to investigate the changes and regulatory mechanism of cluster of differentiation (CD)4+CD25high forkhead box protein 3 (Foxp3+) regulatory T cells (Tregs) in childhood B‑cell acute lymphocytic leukemia (B‑ALL). A total of 18 children with B‑ALL and 15 age‑matched healthy children were included. Reverse‑transcription quantitative polymerase chain reaction was used to evaluate the mRNA levels of Foxp3, cytotoxic T‑lymphocyte associated protein 4 (CTLA4), glucocorticoid‑induced tumor necrosis factor receptor (GITR), lymphocyte activation gene 3 (LAG3), interleukin (IL)‑2 receptor (R)β/γ, IL‑6Rα/β, mothers against decapentaplegic homolog (Smad)3/4 and runt‑related transcription factor (RUNX)1/3 in CD4‑positive cells. The concentration of cytokines in plasma were measured using a cytometric bead array. Additionally, the proportion of CD4+CD25highFoxp3+ Tregs and levels of associated proteins was analyzed using flow cytometry. The results demonstrated that the proportion of CD4+CD25highFoxp3+ and expression of Foxp3 in children with B‑ALL was significantly higher compared with healthy controls (P<0.05) and that transcription levels of CTLA4, GITR and LAG3 were also significantly elevated (P<0.05). Compared with healthy controls, the expression of IL‑2Rα/β and its downstream molecule phosphorylated signal transducer and activator of transcription 5 (pSTAT5) in CD4‑positive cells significantly increased (P<0.05); however, no significant difference of IL‑2Rγ levels was identified between the two groups. Correlation analysis demonstrated a significant positive correlation between the expression of phosphorylated (p) signal transducer and activator of transcription factor (STAT)5 and CD4+CD25highFoxp3+ Tregs in children with B‑ALL (r=0.17; P<0.05). The plasma concentration of TGF‑β, the expression of its receptor TGF‑βRI/II and downstream molecules Smad3/4 were significantly upregulated in children with B‑ALL (P<0.05), whereas the expression of RUNX1/3 was lower compared with healthy controls (P<0.05). Furthermore, the expression of Smad3 and RUNX1 was positively correlated with CD4+CD25highFoxp3+ Tregs in children with B‑ALL (r=0.87 and 0.60, respectively; P<0.05). Additionally, the expression of pSTAT3 in CD4‑positive cells decreased significantly in pediatric patients with B‑ALL when compared with healthy controls; however, plasma concentrations of IL‑6 was significantly higher (P<0.05). Furthermore, a negative correlation was identified between pSTAT3 and CD4+CD25highFoxp3+ Tregs in pediatric patients with B‑ALL (r=‑0.39; P<0.05). However, no significant differences in IL‑6Rα/β expression were identified between the two groups. The results demonstrated that the excessive activation of IL‑2/pSTAT5 and TGF‑β/Smad signaling, and insufficiency of pSTAT3 may be correlated with increased CD4+CD25highFoxp3+ Tregs in pediatric B‑ALL.