[Rapamycin Induces Apoptosis of K562 Cells through EZH2/Hedgehog Signaling Pathway]

To investigate the mechanism of rapamycin-induced apoptosis of chronic myelogenous leukemia cells.

The chronic granulocytic leukemia K562 cells were divided into 3 groups: A, B and C group were treated with rapamycin of 10, 15 and 20 nmol/L, repectively for 24 h, while the K562 cells in control group were not treated with rapamycin. The effect of rapamycin on the proliferation of K562 cells was detected by MTT, and the effect of rapamycin on the apoptosis of K562 cells was detected by AnnexinV-FITC/PI double staining. The expression level of EZH2/Hedgehog signaling pathway genes in K562 cells was detected by RT-PCR, and Western blot was used to detect the levels of apoptotic protein and the related signaling pathway proteins in K562 cells.

The MTT assay showed that the different concentration of rapamycin had obvious inhibitory effects on the cells, and the survival rate of cells in group C was 37.6%±3.4%, which was significantly lower than that of the other groups (P＜0.05). The apoptosis rate of cells in group C was 93.1%±8.1%, which was significantly higher than that of the other groups (P＜0.05). By Western blot, it was found that the relative expression levels of Caspase-3 and BAX protein in group C were 0.36 ± 0.04 and 0.39±0.06, respectively, which were significantly higher than those in other groups (P＜0.05), and the level of BCL-2 protein was 0.17±0.03, which was significantly lower than that of other groups (P＜0.05). By RT-PCR, it was found that the mRNA levels of EZH2 and Hedgehog genes in A, B and C groups were significantly lower than those in the control group (P＜0.05), but mRNA level of Ptch1 gene was significantly higher than that of the control (P＜0.05). By Western blot, it was found that the expression levels of EZH2 and Hedgehog protein in A, B and C groups were significantly lower than that in the control group (P＜0.05), but the level of Ptch1 protein was higher than that of the control (P＜0.05). The relative levels of EZH2 and Hedgehog protein in group C were 0.21 ±0.03 and 0.16±0.05 respectively, which were significantly lower than those in other groups (P＜0.05), and Ptch1 protein level were 0.46 ±0.06, significantly higher than that of other groups (P＜0.05).

Rapamycin can inhibit the protein expression of EZH2 in leukemic cells, thus interfere with the activation of Hedgehog signaling pathway, promote the expression of apoptotic protein, reduce the level of anti apoptotic protein, and eventually induce apoptosis of leukemia cells.