The Influence Of G₁/S Checkpoint And Related Protein Expression Induced By Vinyl Chloride Monomer

ObjectiveVinyl chloride monomer(CH2=CHCl, VCM) is a known carcinogen, it can induce DNA damage, thus the G1/S checkpoints of cell cycles function will be activated and cells were blocked in G1phase. This study focuses on proteins expression level of the G1/S checkpoint regulatory factors, and explores the impact of G1/S checkpoints induced by VCM and the possible carcinogenic mechanisms.MethodThe human normal liver cells (HL-7702) were exposed to VCM (volume fraction were0.8%,2.5%,7.5%,15%and30%respectively) and air (control group) for48h. By optical microscope, we observed the morphological changes of the cells; the fraction of cell cycle and apoptosis of HL-7702were detected by flow cytometry; the level of related proteins expression was detected by western blotting. Using SPSS16.0software to establish the database and the data was analyzed by ANOVA analysis.Results(1) After exposed to VCM for48hours, the quantity of adherent cell reduced and the dead cells increased.(2) Below7.5%VCM group, G0/G1phase of cells increase following the VCM concentration, and the differences compared with7.5%VCM group and control group of were statistically significant (P<0.05); S phase of cells in2.5%VCM group compared with the control group was statistically significant (P<0.05). (3) Below7.5%VCM group, cyclin A and CDK2protein expression increased following the increase VCM concentration, and the differences compared with7.5%,15%VCM group and the control group were statistically significant (P<0.05); CDK4, p53and P16protein expression increased following the increase VCM concentration, and the difference compared with7.5%VCM group and the control group were statistically significant (P<0.05); the expression of cyclinE protein in7.5%group compared with the control group of difference was statistically significant (P<0.05).Conclusion(1) Cell cycle was arrest in G1phase after exposed to low-dose VCM, whereas the arrest in G1phase was discharge after exposed to high-dose VCM; early apoptotic cells were increased.(2) Cell cycle arrest in G1phase after exposed to VCM mainly through the negative regulation of P16.(3) G1/S checkpoint damage by VCM is mainly through decreasing expression of P16, and increasing expression of cyclinE, cyclinA and CDK2, CDK4.