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The Na⁺/H⁺ exchanger (NHE1) as a novel co-adjuvant target in paclitaxel therapy of triple-negative breast cancer cells.

Amith SR, Wilkinson JM, Baksh S, Fliegel L - Oncotarget (2015)

Bottom Line: In vivo xenograft tumor growth in athymic nude mice was also dramatically decreased compared to parental MDA-MB-231 cells.Loss of NHE1 expression also increased the susceptibility of knockout cells to paclitaxel-mediated cell death.NHE1 inhibition, in combination with paclitaxel, resulted in a dramatic decrease in viability, and migratory and invasive potential of triple-negative breast cancer cells, but not in hormone receptor-positive, luminal MCF7 cells.

View Article: PubMed Central - PubMed

Affiliation: Department of Biochemistry, University of Alberta, Edmonton, Alberta, Canada.

ABSTRACT
Dysregulation of Na⁺/H⁺ exchanger isoform one (NHE1) activity is a hallmark of cells undergoing tumorigenesis and metastasis, the leading cause of patient mortality. The acidic tumor microenvironment is thought to facilitate the development of resistance to chemotherapy drugs and to promote extracellular matrix remodeling leading to metastasis. Here, we investigated NHE1 as a co-adjuvant target in paclitaxel chemotherapy of metastatic breast cancer. We generated a stable NHE1-knockout of the highly invasive, triple-negative, MDA-MB-231 breast cancer cells. The NHE1-knockout cells proliferated comparably to parental cells, but had markedly lower rates of migration and invasion in vitro. In vivo xenograft tumor growth in athymic nude mice was also dramatically decreased compared to parental MDA-MB-231 cells. Loss of NHE1 expression also increased the susceptibility of knockout cells to paclitaxel-mediated cell death. NHE1 inhibition, in combination with paclitaxel, resulted in a dramatic decrease in viability, and migratory and invasive potential of triple-negative breast cancer cells, but not in hormone receptor-positive, luminal MCF7 cells. Our data suggest that NHE1 is critical in triple-negative breast cancer metastasis, and its chemical inhibition boosts the efficacy of paclitaxel in vitro, highlighting NHE1 as a novel, potential co-adjuvant target in breast cancer chemotherapy.

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Invasiveness of stimulated (0.2% serum) or unstimulated (10% serum) 231-WT, 231-KO, MDA-MB-468 or MCF7 cells treated with paclitaxel +/− NHE1 inhibitorsThe rate of cell invasion was determined using a Matrigel-coated Boyden chamber porous insert as described in the Materials and Methods. A, Invasiveness of 231-KO cells, +/− stimulation, relative to 231-WT cells, and in comparison to MDA-MB-468 (468) and MCF7 cells [*P<0.001, N=4]. Side panel (B) illustrates representative images. C, Effect of paclitaxel (1 nM, TAX) in combination with NHE1 inhibitors (10 μM EMD87580 or 10 nM HMA) on cell invasion in wild type and NHE1-knockout MDA-MB-231, and MDA-MB-468 cells [*P<0.001, N=4]. D, Illustration of invasion of stimulated 231-WT cells.
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Figure 6: Invasiveness of stimulated (0.2% serum) or unstimulated (10% serum) 231-WT, 231-KO, MDA-MB-468 or MCF7 cells treated with paclitaxel +/− NHE1 inhibitorsThe rate of cell invasion was determined using a Matrigel-coated Boyden chamber porous insert as described in the Materials and Methods. A, Invasiveness of 231-KO cells, +/− stimulation, relative to 231-WT cells, and in comparison to MDA-MB-468 (468) and MCF7 cells [*P<0.001, N=4]. Side panel (B) illustrates representative images. C, Effect of paclitaxel (1 nM, TAX) in combination with NHE1 inhibitors (10 μM EMD87580 or 10 nM HMA) on cell invasion in wild type and NHE1-knockout MDA-MB-231, and MDA-MB-468 cells [*P<0.001, N=4]. D, Illustration of invasion of stimulated 231-WT cells.

Mentions: Cell invasion assays were performed to gain insights into the role of NHE1 in invasion and metastasis of the various types of breast cancer cells. Cell invasion was significantly reduced in 231-KO cells compared to 231-WT parental cells cultured in either stimulated (0.2% serum) or unstimulated (10% serum) conditions for 24 hr. prior to invasion. Additionally, stimulation of cells by reduction of serum caused invasion to more than double in 231-WT cells, but had no effect on 231-KO cells (P<0.001, N=4, Fig. 6A, B). A similar marked increase in invasive potential was seen in another triple-negative breast cancer cell line, MDA-MB-468 cells, with stimulation by reduced serum. No detectable invasion was observed in MCF7 cells in this assay.


The Na⁺/H⁺ exchanger (NHE1) as a novel co-adjuvant target in paclitaxel therapy of triple-negative breast cancer cells.

Amith SR, Wilkinson JM, Baksh S, Fliegel L - Oncotarget (2015)

Invasiveness of stimulated (0.2% serum) or unstimulated (10% serum) 231-WT, 231-KO, MDA-MB-468 or MCF7 cells treated with paclitaxel +/− NHE1 inhibitorsThe rate of cell invasion was determined using a Matrigel-coated Boyden chamber porous insert as described in the Materials and Methods. A, Invasiveness of 231-KO cells, +/− stimulation, relative to 231-WT cells, and in comparison to MDA-MB-468 (468) and MCF7 cells [*P<0.001, N=4]. Side panel (B) illustrates representative images. C, Effect of paclitaxel (1 nM, TAX) in combination with NHE1 inhibitors (10 μM EMD87580 or 10 nM HMA) on cell invasion in wild type and NHE1-knockout MDA-MB-231, and MDA-MB-468 cells [*P<0.001, N=4]. D, Illustration of invasion of stimulated 231-WT cells.
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Related In: Results  -  Collection

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Figure 6: Invasiveness of stimulated (0.2% serum) or unstimulated (10% serum) 231-WT, 231-KO, MDA-MB-468 or MCF7 cells treated with paclitaxel +/− NHE1 inhibitorsThe rate of cell invasion was determined using a Matrigel-coated Boyden chamber porous insert as described in the Materials and Methods. A, Invasiveness of 231-KO cells, +/− stimulation, relative to 231-WT cells, and in comparison to MDA-MB-468 (468) and MCF7 cells [*P<0.001, N=4]. Side panel (B) illustrates representative images. C, Effect of paclitaxel (1 nM, TAX) in combination with NHE1 inhibitors (10 μM EMD87580 or 10 nM HMA) on cell invasion in wild type and NHE1-knockout MDA-MB-231, and MDA-MB-468 cells [*P<0.001, N=4]. D, Illustration of invasion of stimulated 231-WT cells.
Mentions: Cell invasion assays were performed to gain insights into the role of NHE1 in invasion and metastasis of the various types of breast cancer cells. Cell invasion was significantly reduced in 231-KO cells compared to 231-WT parental cells cultured in either stimulated (0.2% serum) or unstimulated (10% serum) conditions for 24 hr. prior to invasion. Additionally, stimulation of cells by reduction of serum caused invasion to more than double in 231-WT cells, but had no effect on 231-KO cells (P<0.001, N=4, Fig. 6A, B). A similar marked increase in invasive potential was seen in another triple-negative breast cancer cell line, MDA-MB-468 cells, with stimulation by reduced serum. No detectable invasion was observed in MCF7 cells in this assay.

Bottom Line: In vivo xenograft tumor growth in athymic nude mice was also dramatically decreased compared to parental MDA-MB-231 cells.Loss of NHE1 expression also increased the susceptibility of knockout cells to paclitaxel-mediated cell death.NHE1 inhibition, in combination with paclitaxel, resulted in a dramatic decrease in viability, and migratory and invasive potential of triple-negative breast cancer cells, but not in hormone receptor-positive, luminal MCF7 cells.

View Article: PubMed Central - PubMed

Affiliation: Department of Biochemistry, University of Alberta, Edmonton, Alberta, Canada.

ABSTRACT
Dysregulation of Na⁺/H⁺ exchanger isoform one (NHE1) activity is a hallmark of cells undergoing tumorigenesis and metastasis, the leading cause of patient mortality. The acidic tumor microenvironment is thought to facilitate the development of resistance to chemotherapy drugs and to promote extracellular matrix remodeling leading to metastasis. Here, we investigated NHE1 as a co-adjuvant target in paclitaxel chemotherapy of metastatic breast cancer. We generated a stable NHE1-knockout of the highly invasive, triple-negative, MDA-MB-231 breast cancer cells. The NHE1-knockout cells proliferated comparably to parental cells, but had markedly lower rates of migration and invasion in vitro. In vivo xenograft tumor growth in athymic nude mice was also dramatically decreased compared to parental MDA-MB-231 cells. Loss of NHE1 expression also increased the susceptibility of knockout cells to paclitaxel-mediated cell death. NHE1 inhibition, in combination with paclitaxel, resulted in a dramatic decrease in viability, and migratory and invasive potential of triple-negative breast cancer cells, but not in hormone receptor-positive, luminal MCF7 cells. Our data suggest that NHE1 is critical in triple-negative breast cancer metastasis, and its chemical inhibition boosts the efficacy of paclitaxel in vitro, highlighting NHE1 as a novel, potential co-adjuvant target in breast cancer chemotherapy.

Show MeSH
Related in: MedlinePlus