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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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Effect of knocking out NHE1 on MDA-MB-231 xenograft tumor growth in female athymic nude miceA, Average tumor volume over time in mice subcutaneously injected with either 231-WT or 231-KO cells. Suspensions of 231-WT and 231-KO cells in Matrigel were subcutaneously injected into the right and left dorsal flanks of female athymic nude mice to determine their tumor-promoting potential. Tumor growth was monitored weekly and mice were euthanized at Day 60. Tumor volume was calculated based on the volume of a sphere (V = (4/3)πr3), or the length and width of the tumor mass (V = 0.5x X 2y, where x is the length and y is the width of the tumor mass). There were 4 mice per group: 7 of 8, and 3 of 8, tumor xenografts developed in the wild type and knockout group respectively. B, Excised tumors from all mice. 231-WT xenografted cells developed into significantly larger, heterogeneous tumors than the 231-KO cells starting at Day 28 [# P<0.05, N=8], and showed a marked increase tumor growth after Day 35 [*P<0.01, N=8]. No significant tumor growth was observed in the knockout group.
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Figure 3: Effect of knocking out NHE1 on MDA-MB-231 xenograft tumor growth in female athymic nude miceA, Average tumor volume over time in mice subcutaneously injected with either 231-WT or 231-KO cells. Suspensions of 231-WT and 231-KO cells in Matrigel were subcutaneously injected into the right and left dorsal flanks of female athymic nude mice to determine their tumor-promoting potential. Tumor growth was monitored weekly and mice were euthanized at Day 60. Tumor volume was calculated based on the volume of a sphere (V = (4/3)πr3), or the length and width of the tumor mass (V = 0.5x X 2y, where x is the length and y is the width of the tumor mass). There were 4 mice per group: 7 of 8, and 3 of 8, tumor xenografts developed in the wild type and knockout group respectively. B, Excised tumors from all mice. 231-WT xenografted cells developed into significantly larger, heterogeneous tumors than the 231-KO cells starting at Day 28 [# P<0.05, N=8], and showed a marked increase tumor growth after Day 35 [*P<0.01, N=8]. No significant tumor growth was observed in the knockout group.

Mentions: To assess the tumor-promoting potential of MDA-MB-231 cells in relation to NHE1 expression, tumor growth of both 231-WT and 231-KO cells was examined as xenografts in athymic nude mice over 60 days. As shown in Fig. 3A, tumors derived from parental MDA-MB-231 cells (N=8) increased in volume over time, while the growth of 231-KO tumors was minimal, or not at all, with small tumors formed in only 3 of 8 injection sites. At 28 days, the observed differences in tumor growth were significant (P<0.05). At 35 days and onwards, growth of 231-WT tumors was markedly increased (P<0.001), but no difference was observed in 231-KO tumor growth. While heterogeneity of excised tumors was observed within the 231-WT group, the importance of NHE1 in tumor-promotion was evident from the lack of tumor formation with the 231-KO cells (Fig. 3B).


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)

Effect of knocking out NHE1 on MDA-MB-231 xenograft tumor growth in female athymic nude miceA, Average tumor volume over time in mice subcutaneously injected with either 231-WT or 231-KO cells. Suspensions of 231-WT and 231-KO cells in Matrigel were subcutaneously injected into the right and left dorsal flanks of female athymic nude mice to determine their tumor-promoting potential. Tumor growth was monitored weekly and mice were euthanized at Day 60. Tumor volume was calculated based on the volume of a sphere (V = (4/3)πr3), or the length and width of the tumor mass (V = 0.5x X 2y, where x is the length and y is the width of the tumor mass). There were 4 mice per group: 7 of 8, and 3 of 8, tumor xenografts developed in the wild type and knockout group respectively. B, Excised tumors from all mice. 231-WT xenografted cells developed into significantly larger, heterogeneous tumors than the 231-KO cells starting at Day 28 [# P<0.05, N=8], and showed a marked increase tumor growth after Day 35 [*P<0.01, N=8]. No significant tumor growth was observed in the knockout group.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4359231&req=5

Figure 3: Effect of knocking out NHE1 on MDA-MB-231 xenograft tumor growth in female athymic nude miceA, Average tumor volume over time in mice subcutaneously injected with either 231-WT or 231-KO cells. Suspensions of 231-WT and 231-KO cells in Matrigel were subcutaneously injected into the right and left dorsal flanks of female athymic nude mice to determine their tumor-promoting potential. Tumor growth was monitored weekly and mice were euthanized at Day 60. Tumor volume was calculated based on the volume of a sphere (V = (4/3)πr3), or the length and width of the tumor mass (V = 0.5x X 2y, where x is the length and y is the width of the tumor mass). There were 4 mice per group: 7 of 8, and 3 of 8, tumor xenografts developed in the wild type and knockout group respectively. B, Excised tumors from all mice. 231-WT xenografted cells developed into significantly larger, heterogeneous tumors than the 231-KO cells starting at Day 28 [# P<0.05, N=8], and showed a marked increase tumor growth after Day 35 [*P<0.01, N=8]. No significant tumor growth was observed in the knockout group.
Mentions: To assess the tumor-promoting potential of MDA-MB-231 cells in relation to NHE1 expression, tumor growth of both 231-WT and 231-KO cells was examined as xenografts in athymic nude mice over 60 days. As shown in Fig. 3A, tumors derived from parental MDA-MB-231 cells (N=8) increased in volume over time, while the growth of 231-KO tumors was minimal, or not at all, with small tumors formed in only 3 of 8 injection sites. At 28 days, the observed differences in tumor growth were significant (P<0.05). At 35 days and onwards, growth of 231-WT tumors was markedly increased (P<0.001), but no difference was observed in 231-KO tumor growth. While heterogeneity of excised tumors was observed within the 231-WT group, the importance of NHE1 in tumor-promotion was evident from the lack of tumor formation with the 231-KO cells (Fig. 3B).

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