CXCR1 blockade selectively targets human breast cancer stem cells in vitro and in xenografts
Christophe Ginestier, … , Gabriela Dontu, Max S. Wicha
Christophe Ginestier, … , Gabriela Dontu, Max S. Wicha
Published January 4, 2010
Citation Information: J Clin Invest. 2010;120(2):485-497. https://doi.org/10.1172/JCI39397.
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Research Article Oncology

CXCR1 blockade selectively targets human breast cancer stem cells in vitro and in xenografts

Abstract

Recent evidence suggests that breast cancer and other solid tumors possess a rare population of cells capable of extensive self-renewal that contribute to metastasis and treatment resistance. We report here the development of a strategy to target these breast cancer stem cells (CSCs) through blockade of the IL-8 receptor CXCR1. CXCR1 blockade using either a CXCR1-specific blocking antibody or repertaxin, a small-molecule CXCR1 inhibitor, selectively depleted the CSC population in 2 human breast cancer cell lines in vitro. Furthermore, this was followed by the induction of massive apoptosis in the bulk tumor population via FASL/FAS signaling. The effects of CXCR1 blockade on CSC viability and on FASL production were mediated by the FAK/AKT/FOXO3A pathway. In addition, repertaxin was able to specifically target the CSC population in human breast cancer xenografts, retarding tumor growth and reducing metastasis. Our data therefore suggest that CXCR1 blockade may provide a novel means of targeting and eliminating breast CSCs.

Authors

Christophe Ginestier, Suling Liu, Mark E. Diebel, Hasan Korkaya, Ming Luo, Marty Brown, Julien Wicinski, Olivier Cabaud, Emmanuelle Charafe-Jauffret, Daniel Birnbaum, Jun-Lin Guan, Gabriela Dontu, Max S. Wicha

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Figure 3

Effect of repertaxin treatment on FAK, AKT, and FOXO3A activation.

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Effect of repertaxin treatment on FAK, AKT, and FOXO3A activation. To ev...
To evaluate the effect of repertaxin treatment on CXCR1 downstream signaling, we used 2 different viral constructs, 1 knocking down PTEN expression via a PTEN-siRNA and the other leading to FAK overexpression (Ad-FAK). (A) Repertaxin treatment led to a decrease in FAK Tyr397 and AKT Ser473 phosphorylation, whereas PTEN deletion and FAK overexpression blocked the effect of repertaxin treatment on FAK and AKT activity. (B) Using immunofluorescence staining on CXCR1+ cells, we confirmed that repertaxin treatment caused a disappearance of phospho-FAK (membranous staining in red) and phospho-AKT expression (cytoplasmic staining in red). Immunofluorescence staining with anti-FOXO3A revealed a cytoplasmic location of FOXO3A (red) in the untreated cells, whereas repertaxin treatment induced a relocalization of FOXO3A to the nucleus. In contrast, cells with PTEN deletion or FAK overexpression displayed a high level of phospho-FAK, phospho-AKT, and cytoplasmic FOXO3A expression in both the repertaxin-treated and untreated cells. In all samples, nuclei were counterstained with DAPI (blue). Scale bar: 50 μm. (C and D) The effect of repertaxin on SUM159 PTEN-siRNA and SUM159 Ad-FAK cell viability and on the CSC population was assessed using MTT and ALDEFLUOR assays, respectively. After 3 days of treatment, cells with PTEN deletion or FAK overexpression developed resistance to repertaxin (C). Furthermore, repertaxin treatment did not alter the proportion of ALDEFLUOR+ SUM159 PTEN knockdown cells (D). Error bars represent mean ± SD.