Emodin and AZT synergistically inhibit the proliferation and induce the apoptosis of leukemia K562 cells through the EGR1 and the Wnt/β‑catenin pathway.

The aim of the present study was to investigate the synergistic antitumor effects of emodin and 3'‑azido‑3'‑deoxythymidine (AZT) on human chronic myeloid leukemia cells and to explore the possible underlying mechanisms. The K562 cells were treated with emodin and AZT, and the rates of cell inhibition and apoptosis were determined by MTT assay and flow cytometry, respectively. The mRNA expression of EGR1 was detected by reverse transcription‑polymerase chain reaction (RT‑PCR) analysis. The expression of EGR1 was silenced using siRNA, and then protein expression of β‑catenin was detected by western blotting. The results demonstrated that AZT enhanced the inhibitory effect of emodin in K562 cells. The IC50 of the emodin/AZT combination at 24, 48 or 72 h was 23.6/235.6, 10.2/101.6 or 5.9/58.5 µmol/l, respectively, which was significantly lower compared with the IC50 of emodin (all >32 µmol/l) or AZT (all >320 µmol/l) alone. There was a dose‑dependent response to the combined emodin and AZT treatment, and the calculation of the combination index yielded values <1, demonstrating the synergistic effect of the combined treatment compared with the control (P<0.05). Furthermore, the combination of emodin and AZT increased apoptosis in K562 cells (P<0.05). Apoptosis was higher in the combination group compared with that of either treatment alone or control groups. The expression of early growth response‑1 (EGR1) in K562 cells was upregulated in a time‑dependent manner. The expression of EGR1 was higher in the combination group compared with that in the emodin or AZT alone groups. The expression of the Wnt/β‑catenin signaling pathway in the combination group was lower compared with that in the emodin or AZT alone groups. The expression of the Wnt/β‑catenin signaling pathway was significantly increased following EGR1 siRNA transfection. These data suggest that treating K562 cells with a combination of emodin and AZT exhibits reduced toxicity and improves therapeutic efficacy, and that the growth, inhibition, apoptosis and regulation of the Wnt/β‑catenin signaling pathway in human chronic myeloid leukemia cells by emodin and AZT may be associated with the expression of EGR1.