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Breast Cancer Res Treat. 2016 Jan;155(2):203-13. doi: 10.1007/s10549-015-3667-x. Epub 2016 Jan 6.

Silencing overexpression of FXYD3 protein in breast cancer cells amplifies effects of doxorubicin and γ-radiation on Na(+)/K(+)-ATPase and cell survival.

Author information

1
North Shore Heart Research Group, Kolling Institute of Medical Research, University of Sydney, Sydney, Australia.
2
Hormones and Cancer Laboratories, Kolling Institute of Medical Research, University of Sydney, Sydney, Australia.
3
North Shore Heart Research Group, Kolling Institute of Medical Research, University of Sydney, Sydney, Australia. helge.rasmussen@sydney.edu.au.
4
The Department of Cardiology, Royal North Shore Hospital, St Leonards, NSW, 2065, Australia. helge.rasmussen@sydney.edu.au.

Abstract

FXYD3, also known as mammary tumor protein 8, is overexpressed in several common cancers, including in many breast cancers. We examined if such overexpression might protect Na(+)/K(+)-ATPase and cancer cells against the high levels of oxidative stress characteristic of many tumors and often induced by cancer treatments. We measured FXYD3 expression, Na(+)/K(+)-ATPase activity and glutathionylation of the β1 subunit of Na(+)/K(+)-ATPase, a reversible oxidative modification that inhibits the ATPase, in MCF-7 and MDA-MB-468 cells. Expression of FXYD3 was suppressed by transfection with FXYD3 siRNA. A colorimetric end-point assay was used to estimate cell viability. Apoptosis was estimated by caspase 3/7 (DEVDase) activation using a Caspase fluorogenic substrate kit. Expression of FXYD3 in MCF-7 breast cancer cells was ~eightfold and ~twofold higher than in non-cancer MCF-10A cells and MDA-MB-468 cancer cells, respectively. A ~50 % reduction in FXYD3 expression increased glutathionylation of the β1 Na(+)/K(+)-ATPase subunit and reduced Na(+)/K(+)-ATPase activity by ~50 %, consistent with the role of FXYD3 to facilitate reversal of glutathionylation of the β1 subunit of Na(+)/K(+)-ATPase and glutathionylation-induced inhibition of Na(+)/K(+)-ATPase. Treatment of MCF-7 and MDA-MB- 468 cells with doxorubicin or γ-radiation decreased cell viability and induced apoptosis. The treatments upregulated FXYD3 expression in MCF-7 but not in MDA-MB-468 cells and suppression of FXYD3 in MCF-7 but not in MDA-MB-468 cells amplified effects of treatments on Na(+)/K(+)-ATPase activity and treatment-induced cell death and apoptosis. Overexpression of FXYD3 may be a marker of resistance to cancer treatments and a potentially important therapeutic target.

KEYWORDS:

Breast cancer; Doxorubicin; FXYD3 protein; Gamma irradiation; Glutathionylation; Sodium–potassium (Na+/K+) ATPase

PMID:
26740212
DOI:
10.1007/s10549-015-3667-x
[Indexed for MEDLINE]

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