Targeting peroxiredoxin i potentiates 1,25-dihydroxyvitamin D3-induced cell differentiation in leukemia cells

Abstract

Although 1,25-dihydroxyvitamin D3 (VD3) is regarded as a promising inducing agent for leukemia cell differentiation, it is not as effective an agent as all-trans-retinoic acid, and its usefulness is also limited by the adverse effects of hypercalcemia. The aim of the present study was to determine whether combining VD3 with adenanthin, a peroxiresoxin I (Prx I)-targeting natural compound, improves the efficacy of VD3. Cell viability was assessed using a trypan blue exclusion assay and flow cytometry was used to evaluate the expression of cell surface markers, CD11b/CD14, and the level of reactive oxygen species (ROS). Wright's staining was used to examine morphological changes and RNA-interference was used to knockdown Prx I and p65 gene expression. Protein expression was determined by western blot analysis. The results demonstrated that adenanthin markedly enhanced VD3-induced cell differentiation of leukemia NB4 cells, as evidenced by the increased percentage of CD11b-and CD14-positive cells, the mature morphology of the monocytes and the increased phagocytic ability. Consistent with these results, knockdown of Prx I, but not nuclear factor-κB (p65), enhanced VD3-induced cell differentiation. The combinatorial effects of adenanthin and VD3 were shown to be associated with the ROS-CCAAT-enhancer-binding protein (C/EBP)β axis, since N-acetylcysteine, a ROS scavenger, was able to abrogate the differentiation-enhancing effects of adenanthin, and the knockdown of C/EBPβ also inhibited the combinatorial effects of adenanthin and VD3. In addition, co-treatment with adenanthin and VD3 was able to induce differentiation in other non-acute promyelocytic leukemia cells and primary leukemia cells. In conclusion, the results of the present study revealed a novel role for Prx I in VD3-induced cell differentiation, and suggested that targeting Prx I may represent a novel strategy to enhance VD3-induced leukemia cell differentiation.