Knockdown of dual specificity phosphatase 4 enhances the chemosensitivity of MCF-7 and MCF-7/ADR breast cancer cells to doxorubicin

Abstract

Background: Breast cancer is the major cause of cancer-related deaths in females world-wide. Doxorubicin-based therapy has limited efficacy in breast cancer due to drug resistance, which has been shown to be associated with the epithelial-to-mesenchymal transition (EMT). However, the molecular mechanisms linking the EMT and drug resistance in breast cancer cells remain unclear. Dual specificity phosphatase 4 (DUSP4), a member of the dual specificity phosphatase family, is associated with cellular proliferation and differentiation; however, its role in breast cancer progression is controversial.

Methods: We used cell viability assays, Western blotting and immunofluorescent staining, combined with siRNA interference, to evaluate chemoresistance and the EMT in MCF-7 and adriamycin-resistant MCF-7/ADR breast cancer cells, and investigate the underlying mechanisms.

Results: Knockdown of DUSP4 significantly increased the chemosensitivity of MCF-7 and MCF-7/ADR breast cancer cells to doxorubicin, and MCF-7/ADR cells which expressed high levels of DUSP4 had a mesenchymal phenotype. Furthermore, knockdown of DUSP4 reversed the EMT in MCF-7/ADR cells, as demonstrated by upregulation of epithelial biomarkers and downregulation of mesenchymal biomarkers, and also increased the chemosensitivity of MCF-7/ADR cells to doxorubicin.

Conclusions: DUSP4 might represent a potential drug target for inhibiting drug resistance and regulating the process of the EMT during the treatment of breast cancer.

Keywords: 4,6-diamidino-2-phenylindole; Breast cancer; CCK-8; Chemoresistance; DAPI; DUSP4; Doxorubicin; EMT; MAP; PBS; TGF-β; cell counting kit-8 assay; dual specificity phosphatase 4; epithelial-to-mesenchymal transition; mitogen-activated protein; phosphate buffer solution; transforming growth factor beta.