Abstract:

Objective

To investigate the effects of Velcade,a proteasome inhibitor,on HepG2 cells,and to explore the mechanism.

Methods

HepG2 cells were treated with various concentrations of Velcade for 24 h and 48 h. The cell viability was assessed by 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT)assay.Cell apoptosis was investigated by flow cytometry.Western blot assayed the change of caspase 3.The expressions of Bcl-2 family,Cyclin A and Cyclin D were detected by reverse transcription-polymerase chain reaction (RT-PCR).

Results

Viabilities of HepG2 cells treated with various concentrations of Velcade(32,64,128,256,512 nmol/L)for 48 h were significantly decreased compared to control group.Viabilities of HepG2 cells gradually reduced to 91.4%±2.1%, 75.0%±3.7%, 57.3%±1.6%, 52.7%±1.6% and 31.4%±2.6%, respectively. The differences compared with control group (100.0%±1.7%)were significant (P<0.05).The percent of SubG1 of HepG2 cells (27.3%±5.3%)treated with 128 nmol/L Velcade 48 h was significantly higher than that in control group(4.3%±0.5%,P<0.05).After treatment with Velcade(128 nmol/L)for 24 h,the expression of caspase 3 markedly decreased compared with control. Velcade greatly increased the G2/M phase in HepG2 cells. Velcade resulted in no significant changes of Bcl-2 family member.However,Velcade down regulated the expressions of Cyclin A and Cyclin D.

Conclusion

The mechanism of Velcade to induced apoptosis in HepG2 is not associated with change of Bcl-2 family member.Velcade induced G2/M phase arrest via down regulation of Cyclin A and D.

Key words: Proteasome inhibitor, Velcade, Hepatocellular carcinoma, Apoptosis