Tetramethylpyrazine potentiates arsenic trioxide activity against HL-60 cell lines

The objective of this study was to evaluate the effects of tetramethylpyrazine (TMP) in combination with arsenic trioxide (As 2 O 3 ) on the proliferation and differentiation of HL-60 cells. The HL-60 cells were treated with 300 µg/mL TMP, 0.5 µM As 2 O 3 , and 300 µg/mL TMP combined with 0.5 µM As 2 O 3 , respectively. The proliferative inhibition rates were determined with MTT. Differentiation was detected by the nitroblue tetrazolium (NBT) reduction test, Wright's staining and the distribution of CD11b and CD14. Flow cytometry was used to analyze cell cycle distribution. RT-PCR and Western blot assays were employed to detect the expressions of c-myc, p27, CDK2, and cyclin E1. Combination treatment had synergistic effects on the proliferative inhibition rates. The rates were increased gradually after the combination treatment, much higher than those treated with the corresponding concentration of As 2 O 3 alone. The cells exhibited characteristics of mature granulocytes and a higher NBT-reducing ability, being a 2.6-fold increase in the rate of NBT-positive ratio of HL-60 cells within the As 2 O 3 treatment versus almost a 13-fold increase in the TMP + As 2 O 3 group. Cells treated with both TMP and As 2 O 3 expressed far more CD11b antigens, almost 2-fold compared with the control group. Small doses of TMP potentiate As 2 O 3 -induced differentiation of HL-60 cells, possibly by regulating the expression and activity of G0/G1 phase-arresting molecules. Combination treatment of TMP with As 2 O 3 has significant synergistic effects on the proliferative inhibition of HL-60 cells.