[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].

OBJECTIVE

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.

METHODS

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.

RESULTS

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.

CONCLUSIONS

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.