Abstract
Paclitaxel (PTX) is one of the most effective drugs used in the treatment of breast cancer. Nonetheless, the appearance of MDR1 (multidrug resistance 1) in tumor cells has become a significant hindrance for efficacious chemotherapy. In this study, we show that the expression level of Egr-1 (early growth response gene-1) in cancer tissues (from paclitaxel chemotherapy failure patients) and MCF-7/PTX cells (the breast cancer cell line that was resistant to paclitaxel) was increased. Cell proliferation assay and apoptosis assay revealed that Egr-1 could promote cell growth and inhibit apoptosis in MCF-7/PTX. Mechanistic studies indicated that Egr-1 could bind to the proximal MDR1 promoter and enhance MDR1 transcription. These findings indicate that paclitaxel induced Egr-1 accumulation and upregulated the expression of MDR1, thereby inducing the drug resistance in MCF-7/PTX. Our results suggest a novel pathway by which paclitaxel induces MDR1 expression, possibly illuminating a potential target pathway for the prevention of MDR1-mediated drug resistance.
Key words:
Egr-1; Breast cancer; MDR1; Drug resistance.