Inhibition of phosphatidylcholine-specific phospholipase C downregulates HER2 overexpression on plasma membrane of breast cancer cells.
Breast Cancer Res
; 12(3): R27, 2010.
Article
em En
| MEDLINE
| ID: mdl-20462431
ABSTRACT
INTRODUCTION:
Overexpression on plasma membrane of human epidermal growth factor receptor 2 (HER2) is reported in 25% to 30% of breast cancers. Heterodimer formation with cognate members of the epidermal growth factor receptor (EGFR) family, such as HER3 and EGFR, activates abnormal cell-signalling cascades responsible for tumorigenesis and further transcriptional HER2 gene upregulation. Targeting the molecular mechanisms controlling HER2 overexpression and recycling may effectively deactivate this feedback-amplification loop. We recently showed that inactivation of phosphatidylcholine-specific phospholipase C (PC-PLC) may exert a pivotal role in selectively modulating the expression on the membrane of specific receptors or proteins relevant to cell function. In the present study, we investigated the capability of PC-PLC inhibition to target the molecular mechanisms controlling HER2 overexpression on the membrane of breast cancer cells by altering the rates of its endocytosis and lysosomal degradation.METHODS:
Localization on the membrane and interaction of PC-PLC with HER2, EGFR, and HER3 were investigated on HER2-overexpressing and HER2-low breast cancer cell lines, by using confocal laser scanning microscopy, flow cytometry, cell-surface biotinylation, isolation of lipid rafts, and immunoprecipitation experiments. The effects of the PC-PLC inhibitor tricyclodecan-9-yl-potassium xanthate (D609) on HER2 expression on the membrane and on the levels of overall HER2, HER2-HER3, and HER2-EGFR contents were monitored in the HER2-overexpressing SKBr3 cells, after either transient or continuous receptor engagement with anti-HER2 monoclonal antibodies, including trastuzumab. Changes of HER2 expression and cell proliferation were examined in SKBr3, BT-474, and MDA-MB-453 cells continuously exposed to D609 alone or combined with trastuzumab.RESULTS:
PC-PLC selectively accumulates on the plasma membrane of HER2-overexpressing cells, where it colocalizes and associates with HER2 in raft domains. PC-PLC inhibition resulted in enhanced HER2 internalization and lysosomal degradation, inducing downmodulation of HER2 expression on the membrane. Moreover, PC-PLC inhibition resulted in strong retardation of HER2 reexpression on the membrane and a decrease in the overall cellular contents of HER2, HER2-HER3, and HER2-EGFR heterodimers. The PC-PLC inhibitor also induced antiproliferative effects, especially in trastuzumab-resistant cells.CONCLUSIONS:
The results pointed to PC-PLC inhibition as a potential means to counteract the tumorigenic effects of HER2 amplification and complement the effectiveness of current HER2-targeting therapies.
Texto completo:
1
Base de dados:
MEDLINE
Assunto principal:
Fosfolipases Tipo C
/
Mama
/
Neoplasias da Mama
/
Membrana Celular
/
Receptor ErbB-2
Idioma:
En
Ano de publicação:
2010
Tipo de documento:
Article