The effect of aqueous cinnamon extract on the apoptotic process in acute myeloid leukemia HL-60 cells

Abstract

Background: Acute promyelocytic leukemia (APL) is an acute leukemia diagnosed by translocation of chromosomes 15 and 17 [T (15,17)] and aggregation of neoplastic promyelocytes which are incapable of being converted into mature cells. Today, many tend to use medicinal herbs in studies and clinical applications for treatment of cancers. Cinnamon with scientific name "cinnamomumzelanicum" is a shrub of Laurales order, lauraceae family with cinnamomum genus. It is a medicinal shrub with anti-proliferation effect on tumor cells. This study was conducted to determine the effects of aqueous cinnamon extract on HL-60 cells as a model for APL.

Materials and methods: In this in vitro experimental study, HL-60 cell line was cultured under the influence of cinnamon extract's concentrations of 0.01, 0.1, 1, and 2 mg/ml in with intervals of 24, 48, and 72 h. Growth inhibition and toxic effects of cinnamon extract were evaluated through tetrazolium salt reduction. The effect of this herb on the cell cycle was studied by flow cytometry. The Hoechst stain was used to detect apoptotic cell nuclei.

Results: Cinnamon extract inhibited the growth of HL-60 cells as correlated with concentration and time. After 72 h of treating HL-60 cells with 0.01 mg/l cinnamon extract, the growth of cells was inhibited by 90.1%. Cinnamon extract stopped the cell cycle in G1 phase and the Hoechst staining verified the apoptotic process in those cells.

Conclusion: Considering the inhibitory property of cinnamon extract, we recommend it as a single drug or besides other medications for treating promyelocytic leukemia.

Keywords: Acute promyelocytic leukemia; HL-60 cells; apoptosis; cell cycle; cinnamon extract.

Figure 1

The results of analyzing variations in percentage of inhibiting proliferation of HL-60 cell line incubating with aqueous cinnamon extract concentrations of 0.01, 0.1, 1, and 2 mg/ml after 24, 48, and 72 h (*P < 0.05 and ***P < 0.001)

Figure 2a

The control samples of HL-60 cell line which were not incubated at all. As seen in the figure, no apoptotic cell is observed under magnification of ×10

Figure 2b

Fluorescent microscope image of HL-60 cells incubated with 2 mg/ml aqueous cinnamon extract for 24 h, then, stained with Hoechst dye. The apoptotic cells are clearly distinguished under magnification of ×10

Figure 2c

Fluorescent microscope image of HL-60 cells incubated with 0.01 mg/ml aqueous cinnamon extract for 72 h, then, stained with Hoechst dye. The number of apoptotic nuclei in this slide obviously ncreased compared to that of control samples under magnification of ×10

Figure 3a

Analysis of cell cycle distribution method and DNA content in each phases of G2/M, S, G1, and SubG1 in HL-60 cell line (control sample)

Figure 3b

Evaluating the effect of 2 mg/ml aqueous cinnamon extract and 24 h of incubation on distribution and progression of cell cycle in HL-60 cell line

Figure 3c

Evaluating the effect of 0.01 mg/ml aqueous cinnamon extract on distribution and progression of cell cycle in HL-60 cell line