The Primary Study On The Molecular Mechanism Of Cell Cycle Arrest By Lycorine In Leukemia Cells Via Up-regulating P21 Expression

Leukemia is a common hematological malignancy in the world. which is one of the ten high incidence of malignant tumor in China. At present, chemotherapy remains one of the convenional leukemia treatment and is the basis of other treatment methods. Lycorine is one of alkaloids extracted from Amaryllidaceae family, showing a strong anti-cancer activity. The author's research group made researchs in the anti-leukemia mechanism of lycorine and got a series of research results. To further elucidate anti-leukemia action of lycorine, this research focused on the expression change of proteins associated with cell cycle progression in HL-60 and K562 cells after treatment of lycorine.After HL-60 cells were treated with different concentrations of lycorine for 24h, real-time PCR was used to analyze the effect of lycorine on the expression of p21 at gene transcriptional level. The results show that the expression of p21 was up-regulated at a dose-dependent manner. Furthemore, Western blotting was used to analyze the effect of lycorine on the expression of p21 at protein level. After the K562 cells were treated with different concentrations of lycorine, p21 was up-regulated at a dose-dependent manner. This is consistent with the data of mRNA levels. So, we speculated that p21 should be the key molecular target for anti-leukemia action of lycorine. p21 functions as a regulator of cell cycle progression. Thus, the author used Western blotting to analyze the expression changes of CDK/Cyclin and non-phosphorylated Rb protein which made an important regulate role in G1/S and G2/M transition of cell cycle after cells were treated with lycorine. The results showed that expression of CDK2,CyclinB,CDK1 was down-regulated both in HL-60 and K562 cells. However the expression of non-phosphorylated Rb was up-regulated in HL-60 cell. Meanwhile we used flow cytometry to analyze the mean-immunofluorescence intensity of CDK2,CyclinB,CDK1,CyclinE,non-phosphorylated Rb after HL-60 cells were treated with different concentrations of lycorine. As a result, the mean-immunofluorescence intensity of CDK2,CyclinB,CDK1,CyclinE was down-regulated and the intensity of non-phosphorylated Rb was up-regulated.It is concluded that the p21 was up-regulated in the level of gene and protein after the cells was treated with lycorine. Moreover, the expression of CDK2,CyclinE,CDK1,CyclinB was down-regulated and the expression of non-phosphorylated Rb was up-regulated. So, the lycorine could induce leukemia cell cycle arrest.