The experimental and clinical study on the effect of curcumin on cell cycle proteins and regulating proteins of apoptosis in acute myelogenous leukemia

Abstract

To investigate whether the Bcl-2 gene family is involved in modulating mechanism of apoptosis and change of cell cycle protein induced by curcumin in acute myeloid leukemia HL-60 cell line and primary acute myelogenous leukemic cells, the Bcl-2 family member Mcl-1, Bax and Bak and cell cycle proteins including P27^kipl, P21^wafl, cyclin D₃ and pRb^p− were selected and their expression detected by SABC immuno-histochemical stain method. The attitude of sub-G₁ peak in DNA histogram was determined by FCM. The TUNEL positive cell percentage was identified by terminal deoxynucleotidyl transferase (TdT)-mediated Biotin dUNP end labeling technique. It was found that when HL-60 cells were treated with 25 µmol/L curcumin for 24 h, the expression level of Mcl-1 was down-regulated, but that of Bax and Bak up-regulated time-dependently. There was significant difference in the expression level of Mcl-1, Bax and Bak between the curcumin-treated groups and control group (P<0.05−0.01). At the same time, curcumin had no effect on progress of cell cycle in primaty acute myelogenous leukemia at newly diagnosis, but could increase the peak of Sub-G₁(P<0.05), and down-regulate the expression of Mcl-1 and up-regulate the expression of Bax and Bak with the difference being statistically significant. The expression of P27^kipl, P21^wafl and pRb^p− were elevated and that of cyclin D₃ decreased in the presence of curcumin. These findings suggested that the Bcl-2 gene family indeed participated in the regulatory process of apoptosis induced by curcumin in HL-60 cells and AML cells. Curcumin can induce apoptosis of primary acute myelogenous leukemic cells and disturb cell cycle progression of HL-60 cells. The mechanism appeared to be mediated by perturbing G₀/G₁ phases checkpoints which associated with up-regulation of P27^kipl, P21^wafl and pRb^p− expression, and down-regulation of cyclin D₃.

Keywords

curcumin / Bcl-2 gene family / cell cycle protein / HL-60 cell / primary leukemic cell