Effects of Notch1 signaling on histone acetylation of Foxp3 gene in children with B-cell precursor acute lymphoblastic leukemia / 中华微生物学和免疫学杂志

ABSTRACT

Objective:To investigate the effects of Notch1 signaling on histone acetylation of Foxp3 gene and its roles in regulating regulatory T (Treg) cells in children with acute B-cell precursor lymphoblastic leukemia (BCP-ALL).Methods:Blood samples were collected form 38 children with BCP-ALL before treatment and 15 age-matched healthy children (control group). Flow cytometry was performed to detect the proportion of peripheral blood CD4 + CD25 hiFoxp3 + Treg cells and the expression of Foxp3, cytotoxic lymphocyte antigen 4 (CTLA4), glucocorticoid-induced tumor necrosis factor receptor (GITR), CD39 and Notch1 at protein level. Histone 4 acetylation (H4Ac) at Foxp3 gene promoter and the binding abilities of Foxp3 gene promoter to NICD1 and p300 in CD4 + T cells were measured by chromatin immunoprecipitation. Quantitative real-time PCR was performed to detect the expression of Foxp3, presenilin 1 (PSEN1), mastermind-like transcriptional coactivator 1 (MAML1), SKI-interacting protein (SKIP), F-box and WD40 domain protein 7 (FBXW7), glycogen synthase kinase-3 beta (GSK3β) and IKAROS at mRNA level in CD4 + T cells. The concentrations of TGF-β and IL-10 in plasma were evaluated by ELISA. Results:(1) The proportion of peripheral blood CD4 + CD25 hiFoxp3 + Treg cells, the expression of differentiation- and function-associated molecules (Foxp3, CTLA4, GITR and CD39) and the concentrations of TGF-β and IL-10 in plasma were higher in the BCP-ALL group than in the control group ( P<0.05). (2) In children with acute BCP-ALL, H4Ac at Foxp3 promoter and the binding abilities of Foxp3 gene promoter to NICD1 and p300 were significantly increased as compared with those in control group( P<0.05). The binding abilities of Foxp3 gene promoter to NICD1 and p300 were positively correlated with the expression of Foxp3 at mRNA level ( r=0.58 and 0.46, both P<0.05). After competitive inhibition, the three aforementioned indexes in the acute BCP-ALL group were significantly lower than those in untreated group ( P<0.05); the binding ability of Foxp3 gene promoter to NICD1 in the control group was also significantly lower than that in untreated control group ( P<0.05), but no statistical differences in the other two indexes were found between the control groups with or without treatment ( P>0.05). ⑶ Compared with the control group, the expression of Notch1, PSEN1, MAML1 and SKIP in CD4 + T cells were elevated significantly ( P<0.05), while the transcription level of negative regulatory factor FBXW7 was decreased remarkably in children with acute BCP-ALL ( P<0.05). No statistical differences in the expression of GSK3β or IKAROS were found between the two groups ( P>0.05). Conclusions:Overactivation of Notch1 signaling caused by low expression of FBXW7 might be the key factor resulting in histone 4 hyperacetylation at foxp3 gene promoter and Treg cell dysfunction in children with acute BCP-ALL.