p73-mediated cell cycle arrest in MRC-5 cells and H1299 cells treated with B(a)P.

Objective To understand the effect of p73 on the B(a)P-induced cell cycle arrest in MRC-5 and H1299 cells.Methods Both MRC-5 cells and H1299 cells in the period of logarithmic growth were treated with B(a)P at the concentrations of 0 μmol/L (the solvent control),8,16,32,64 and 128 μmol/L for 24 h.Cell proliferations were detected with the MTT assay.In MRC5 cells and H1299 cells,the percentages of cells in the G1,S and G2 phases of the cell cycle were analyzed using the flow cytometry.Expressions of p53,p73,p21 and Gadd45 genes at mRNA levels were detected by real-time quantitative PCR assay.Results The cell proliferation of MRC-5 cells and H1299 cells were increased at the concentrations of 8,16,32 and 64 μmol/L (P0.05 or P0.01).The proliferation reached to the highest point at the concentration of 16 μmol/L in MRC-5 cells and 32 μmol/L in H1299 cells.It was enhanced by fourty and thirty percent respectively compared with the solvent control group.The increased mRNA levels of p53,p73 and p21 genes were determined in the MRC-5 cells treated with B (a)P at the concentrations of 8,16,32,64 and 128 μmol/L (P0.05 or P0.01),and cells were arrested in G1 phases in all treatment groups.After H1299 cells were treated with 8 μmol/L B(a)P for 24 h,enhanced mRNA levels of p21 and p73 were observed (P0.05),and cells were also arrested in G1 phase.However,for Gadd45 gene no significant differences at mRNA levels were detected in all treatment groups (P 0.05).Conclusion When the two kinds of cells are treated with B (a)P at the certain concentrations for 24 h,arrested MRC-5 cells in G1 phase of the cell cycle may be mediated by p53,whereas arrested H1299 cells (p53 null) in G1 phase of the cell cycle may be associated with modulations of p73-mediated signal pathways.