Study of the relationship between early growth response gene 1 activity in p38 mitogen-activated protein kinase pathway and epirubicin resistance of human breast carcinoma cells / 中华病理学杂志

ABSTRACT

<p><b>OBJECTIVE</b>To investigate the relationship between activities of early growth response gene 1 (EGR-1) of p38 mitogen-activated protein kinase (MAPK) pathway and in the epirubicin resistance of breast carcinoma cells.</p><p><b>METHODS</b>Protein expression of phosphorylated p38MAPK was detected by confocal spectral microscopy. Using specific inhibitor SB203580, the effect of p38MAPK on cell apoptosis was analyzed by FITC-Annexin-V/PI double staining. The concentration of epirubicin was detected by flow cytometry (FCM). The 50% inhibition concentration (IC50) of epirubicin on MCF-7/Adr cells was determined by MTT method. Electrophoretic motility shift assay (EMSA) was performed to examine the affinity of EGR-1. EGR-1 mRNA was assessed by RT-PCR. The expression levels of p-glycoprotein, phosphorylated p53 and p38 were detected by Western blot.</p><p><b>RESULTS</b>After treatment with SB203580 (15 micromol/L) 24 h and 48 h, (1) the early and late apoptosis of MCF-7/Adr cells expressing the phosphorylated p38MAPK protein was (25.36 +/- 1.17)% and (38.21 +/- 1.25)%, respectively, P < 0.05. And the tendency was in a time-dependent manner. (2) The average fluorescence intensity of MCF-7/Adr cells expressing the phosphorylated p38MAPK protein was (32.45 +/- 2.36) and (41.66 +/- 3.12), higher than the blank group (14.17 +/- 1.45) and DMSO group (16.28 +/- 0.63), P < 0.01. The epirubicin resistance of MCF-7/Adr cells significantly decreased. (3) SB203580 demonstrated a significantly higher level of EGR-1 activity. The IC50 was (21.53 +/- 2.17) and (8.77 +/- 1.02), lower than the DMSO group (40.74 +/- 2.56). MCF-7/Adr cells treated with SB203580 down-regulated the p38MAPK pathway activity, but up-regulated the EGR-1 mRNA expression. SB203580 significantly increased the cellular phosphorylated p53 protein level, but decreased the p-glycoprotein level in MCF-7/Adr cells.</p><p><b>CONCLUSIONS</b>There is a close relationship between p38MAPK pathway activity and the epirubicin resistance of breast carcinoma cells. The activation of EGR-1 mediated by p38MAPK pathway plays a critical role in epirubicin resistance.</p>