Sterigmatocystin Induced G2 Arrest of Gastric Epithelial Cells in Vitro

Abstract: To explore the effects of sterigmatocystin (ST) on the cell cycle distribution and the expression of cyclinD1， eIF4E and 4E-BP1 of human gastric cell line (GES-1) in vitro. GES-1 cells were treated with ST at different concentrations (100， 500， 1 000 and 2 000 μg/L) for 24 h. The effects of ST on the cell proliferation of GES-1 cells were determined with MTT， flow cytometric (FCM) DNA analysis and Giemsa staining， while that on the expression of proliferation related gene——eIF4E， 4E-BP1 and cyclinD1 at protein level and mRNA level were studied with Western blot and reverse transcription polymerase chain reaction (RT-PCR) respectively. MTT results showed that ST treatment could significantly inhibit the proliferation of the GES-1 cells. The inhibition rate of ST 100， 500， 1 000 and 2 000 μg/L group was 12.76%， 16.35%， 21.65% and 32.06% respectively. FCM cell cycle analysis revealed that the G₂/M fraction was significantly increased in 500， 1 000 and 2 000 μg/L ST treatment group 24 h after treatment. The results of Giemsa showed that within the concentration range from 0 to 2000 μg/L， ST could decrease the mitosis index (MI) of GES-1 dose-dependently. The FCM and Giemsa results suggest that ST could induce cell cycle G₂ arrest on human gastric cells (GES-1) in vitro. Western blot analysis showed that ST could significantly increase the expression of eIF4E and 4E-BP1 within the concentration range from 0 to 2 000 μg/L， and there is a significant dose-effect correlation between ST concentration and the intensity of eIF4E and 4E-BP1 expression at protein level (eIF4E: r=0.844， P<0.01; 4E-BP1: r=0.930， P<0.01)， while the phosphorylation of eIF4E and 4E-BP1 were significantly decreased by ST in a dose-dependent way (peIF4E: r=-0.663， P<0.01; p4E-BP1: r= -0.656， P<0.01). At the same time， the expression of cyclinD1 was down-regulated (r=-0.559， P<0.05). The results of RT-PCR confirmed that ST could increase the expression of eIF4E and 4E-BP1 at mRNA level of GES-1 cells in vitro. Thus， the results in this study suggested that ST could inhibit the proliferation and induce G2 arrest of human gastric GES-1 cells in vitro. The increase of eIF4E and 4E-BP1 and decrease of peIF4E， p4E-BP1 and cyclinD1 may be the putative mechanism.
    

CSTR: 32200.14.cjcb.2009.01.0016