Abstract
IntroductionGlucosylceramide synthase (GCS) is one enzyme that provides a major route for ceramide clearance. Recent evidence has indicated an important role for GCS in multidrug resistance (MDR) tumors. Doxorubicin (DOX)can modulate the expression of GCS in leukemia and ovary cell lines. However, few studies have investigated their relationship in breast cancer;MethodsWe collected 84 excision biopsies from patients with invasive ductal breast cancer of whom 33 patients had undergone preoperative chemotherapy. Immunohistochemistry was used to analyze the expression of GCS protein and significantly showed that the expression of GCS was higher in the samples from patients treated with preoperative chemotherapy(p = 0.018). In order to investigate the underlying mechanism, breast cancer cell lines were cultured with different concentrations of DOX, and mRNA and protein levels of GCS were then detected;ResultsDOX significantly upregulated the expression of GCS at both the mRNA and protein level in ERα-positive MCF-7 cells.We then block down the Sp1 site of GCS promoter, which inhibited the DOX-mediated increase in GCS expression; and after Erα was inhibited in MCF-7 cells, the up-regulation of GCS by DOX also been inhibited.ConclusionsIn conclusion, our data demonstrated the novel finding that DOX could modulate the expression of GCS through the Sp1 site of GCS promoter in ERα-positive breast cancer cells.
Highlights
Glucosylceramide synthase (GCS) is one enzyme that provides a major route for ceramide clearance
In conclusion, our data demonstrated the novel finding that DOX could modulate the expression of GCS through the Sp1 site of GCS promoter in ERa-positive breast cancer cells
33.3% of all the invasive carcinoma samples were positive for GCS (28/84); in tumors resected from patients who were treated with the CAF protocol, the expression of GCS was significantly increased (p = 0.018)
Summary
Glucosylceramide synthase (GCS) is one enzyme that provides a major route for ceramide clearance. The resistance of tumors to chemotherapy occurs to single cytotoxic drugs, and as a cross-resistance to a range of drugs with different structures and cellular targets This phenomenon is termed multidrug resistance (MDR), and is one of the contributing factors that prevents survival rates for breast cancer improving further [1]. Sphingolipids, which include ceramide and sphingosine, are essential structural components of cell membranes They play an important role in regulating the proliferation, survival and apoptosis of cells. Transfection with GCS could increase the level of MDR in breast cancer cell lines [6], whereas its inhibition has proven to be useful in altering responses to chemotherapy in numerous human tumor cell lines [5,7]
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