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Ataxin-1 regulates epithelial – mesenchymal transition of cervical cancer cells

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ABSTRACT

The mutant form of the protein ataxin-1 (ATXN1) causes the neurodegenerative disease spinocerebellar ataxia type-1. Recently, ATXN1 was reported to enhance E-cadherin expression in the breast cancer cell line MCF-7, suggesting a potential association between ATXN1 and cancer development. In the present study, we discovered a novel mechanism through which ATXN1 regulates the epithelial–mesenchymal transition (EMT) of cancer cells. Hypoxia-induced upregulation of the Notch intracellular domain expression decreased ATXN1 expression via MDM2-associated ubiquitination and degradation. In cervical cancer cells, ATXN1 knockdown induced EMT by directly regulating Snail expression, leading to matrix metalloproteinase activation and the promotion of cell migration and invasion. These findings provide insights into a novel mechanism of tumorigenesis and will facilitate the development of new and more effective therapies for cancer.

No MeSH data available.


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NICD downregulates ATXN1 expressionA. HeLa and SiHa cells cultured under normoxic or hypoxic conditions for 24 and 48 h in the absence or presence of the γ-secretase inhibitor GSI-DAPT were subjected to a western blotting analysis of ATXN1 expression. Densitometry results of ATXN1 are shown below each lane. ATXN1 expression was normalized to β-actin levels. Numbers indicate the intensity ratio relative to each control lane (1.0) B. HeLa, SiHa, and CaSki cells were treated with the indicated concentrations (μM) of CoCl2 for 24 h, and lysates were analyzed via western blotting with the indicated antibodies. C. HeLa cells transfected with Myc-NICD were subjected to western blotting analysis. D. Western blotting analysis of HEK293 cells co-transfected with HA-ATXN1 and Myc-NICD. E. Western blotting analysis of HEK293 cells co-transfected with HA-ATXN1 and the indicated amounts of Myc-NICD DNA. H (Hypoxia), N (Normoxia), GSI (γ-secretase inhibitor).
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Figure 1: NICD downregulates ATXN1 expressionA. HeLa and SiHa cells cultured under normoxic or hypoxic conditions for 24 and 48 h in the absence or presence of the γ-secretase inhibitor GSI-DAPT were subjected to a western blotting analysis of ATXN1 expression. Densitometry results of ATXN1 are shown below each lane. ATXN1 expression was normalized to β-actin levels. Numbers indicate the intensity ratio relative to each control lane (1.0) B. HeLa, SiHa, and CaSki cells were treated with the indicated concentrations (μM) of CoCl2 for 24 h, and lysates were analyzed via western blotting with the indicated antibodies. C. HeLa cells transfected with Myc-NICD were subjected to western blotting analysis. D. Western blotting analysis of HEK293 cells co-transfected with HA-ATXN1 and Myc-NICD. E. Western blotting analysis of HEK293 cells co-transfected with HA-ATXN1 and the indicated amounts of Myc-NICD DNA. H (Hypoxia), N (Normoxia), GSI (γ-secretase inhibitor).

Mentions: Notch signaling is augmented by hypoxia in various tumor cell lines [10, 24]. We investigated the effect of hypoxia on ATXN1 expression. First, we examined ATXN1 expression in HeLa and SiHa cervical cancer cell line cells cultured under normoxic (21% O2) or hypoxic (1% O2) conditions. Hypoxia, which was confirmed via expression of the hypoxic marker HIF-1α [25, 26], led to the downregulation of endogenous ATXN1 expression after 24 and 48 h (Figure 1A). Furthermore, our results demonstrated elevated NICD levels in hypoxia and a partial rescue from a decrease in endogenous ATXN1 expression by DAPT GSI, which inhibits the final proteolytic cleavage of the Notch receptor by γ-secretase [27, 28]. We think that DAPT GSI should be not strong enough to completely inhibit the γ-secretase proteins, since NICD was still produced and ATXN1 levels still decreased upon hypoxia in the presence of DAPT.


Ataxin-1 regulates epithelial – mesenchymal transition of cervical cancer cells
NICD downregulates ATXN1 expressionA. HeLa and SiHa cells cultured under normoxic or hypoxic conditions for 24 and 48 h in the absence or presence of the γ-secretase inhibitor GSI-DAPT were subjected to a western blotting analysis of ATXN1 expression. Densitometry results of ATXN1 are shown below each lane. ATXN1 expression was normalized to β-actin levels. Numbers indicate the intensity ratio relative to each control lane (1.0) B. HeLa, SiHa, and CaSki cells were treated with the indicated concentrations (μM) of CoCl2 for 24 h, and lysates were analyzed via western blotting with the indicated antibodies. C. HeLa cells transfected with Myc-NICD were subjected to western blotting analysis. D. Western blotting analysis of HEK293 cells co-transfected with HA-ATXN1 and Myc-NICD. E. Western blotting analysis of HEK293 cells co-transfected with HA-ATXN1 and the indicated amounts of Myc-NICD DNA. H (Hypoxia), N (Normoxia), GSI (γ-secretase inhibitor).
© Copyright Policy - open-access
Related In: Results  -  Collection

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Figure 1: NICD downregulates ATXN1 expressionA. HeLa and SiHa cells cultured under normoxic or hypoxic conditions for 24 and 48 h in the absence or presence of the γ-secretase inhibitor GSI-DAPT were subjected to a western blotting analysis of ATXN1 expression. Densitometry results of ATXN1 are shown below each lane. ATXN1 expression was normalized to β-actin levels. Numbers indicate the intensity ratio relative to each control lane (1.0) B. HeLa, SiHa, and CaSki cells were treated with the indicated concentrations (μM) of CoCl2 for 24 h, and lysates were analyzed via western blotting with the indicated antibodies. C. HeLa cells transfected with Myc-NICD were subjected to western blotting analysis. D. Western blotting analysis of HEK293 cells co-transfected with HA-ATXN1 and Myc-NICD. E. Western blotting analysis of HEK293 cells co-transfected with HA-ATXN1 and the indicated amounts of Myc-NICD DNA. H (Hypoxia), N (Normoxia), GSI (γ-secretase inhibitor).
Mentions: Notch signaling is augmented by hypoxia in various tumor cell lines [10, 24]. We investigated the effect of hypoxia on ATXN1 expression. First, we examined ATXN1 expression in HeLa and SiHa cervical cancer cell line cells cultured under normoxic (21% O2) or hypoxic (1% O2) conditions. Hypoxia, which was confirmed via expression of the hypoxic marker HIF-1α [25, 26], led to the downregulation of endogenous ATXN1 expression after 24 and 48 h (Figure 1A). Furthermore, our results demonstrated elevated NICD levels in hypoxia and a partial rescue from a decrease in endogenous ATXN1 expression by DAPT GSI, which inhibits the final proteolytic cleavage of the Notch receptor by γ-secretase [27, 28]. We think that DAPT GSI should be not strong enough to completely inhibit the γ-secretase proteins, since NICD was still produced and ATXN1 levels still decreased upon hypoxia in the presence of DAPT.

View Article: PubMed Central - PubMed

ABSTRACT

The mutant form of the protein ataxin-1 (ATXN1) causes the neurodegenerative disease spinocerebellar ataxia type-1. Recently, ATXN1 was reported to enhance E-cadherin expression in the breast cancer cell line MCF-7, suggesting a potential association between ATXN1 and cancer development. In the present study, we discovered a novel mechanism through which ATXN1 regulates the epithelial–mesenchymal transition (EMT) of cancer cells. Hypoxia-induced upregulation of the Notch intracellular domain expression decreased ATXN1 expression via MDM2-associated ubiquitination and degradation. In cervical cancer cells, ATXN1 knockdown induced EMT by directly regulating Snail expression, leading to matrix metalloproteinase activation and the promotion of cell migration and invasion. These findings provide insights into a novel mechanism of tumorigenesis and will facilitate the development of new and more effective therapies for cancer.

No MeSH data available.


Related in: MedlinePlus