RESUMO
Objective To investigate the effect of Eicosapentaenoic scid (EPA) on the sensitivity of glioma cell line U87 to temozolomide (TMZ) and the mechanism behind this effect.Methods U87 cells were randomly divided into four groups:control group,TMZ group,EPA+TMZ group and endoplasmic reticulum stress (ERS) activation tunicamycin group (EPA+TMZ+TM group).MTT method was used to evaluate inhibition ratio of cell proliferation.The apoptotic ratio was examined by flow eytometry.Western blot was used to detect the protein expressions of apoptosis cytokines (caspase-3 and Bax) and ERS cytokines [glucose-regulated protein 78 (GRP78) and inositol-requiring enzyme 1 (IRE-1)].Results EPA causes concentration-dependent and time-dependent inhibition of the cell proliferation (all P=0.00).EPA significantly enhanced the sensitivity of glioma cell line U87 to temozolomide.Compared to TMZ treatment alone,the inhibition ratio [(56.27+6.15)％ vs.(42.32±4.12)％,P=0.03] and apoptotic ratio [(49.78±5.94)％ vs.(37.74± 4.24)％,P=0.04] of U87 cells were enhanced by EPA+TMZ treatment.Western blot showed that the expression of apoptotic factor caspase-3 and Bax proteins were increased by EPA+TMZ treatment,while the protein expressions of ERS-related factors (GRP78 and IRE-1) were significantly inhibited (P=0.01).However,the salutary effects of EPA were reversed by ERS activation tunicamycin.Conclusion EPA enhances the sensitivity of glioma cell line U87 to temozolomide,the mechanism of which may be the suppression of ERS response.