The α2β1 integrin is a metastasis suppressor in mouse models and human cancer
Norma E. Ramirez, … , Andries Zijlstra, Mary M. Zutter
Norma E. Ramirez, … , Andries Zijlstra, Mary M. Zutter
Published December 6, 2010
Citation Information: J Clin Invest. 2011;121(1):226-237. https://doi.org/10.1172/JCI42328.
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Research Article Oncology

The α2β1 integrin is a metastasis suppressor in mouse models and human cancer

Abstract

Integrins regulate cell-cell and cell-matrix adhesion and thereby play critical roles in tumor progression and metastasis. Although work in preclinical models suggests that β1 integrins may stimulate metastasis of a number of cancers, expression of the β1 subunit alone has not been shown to be a useful prognostic indicator in human cancer patients. Here we have demonstrated that the α2β1 integrin suppresses metastasis in a clinically relevant spontaneous mouse model of breast cancer. These data are consistent with previous studies indicating high expression of α2β1 integrin in normal breast epithelium and loss of α2β1 in poorly differentiated breast cancer. They are also consistent with our systematic analysis of microarray databases of human breast and prostate cancer, which revealed that decreased expression of the gene encoding α2 integrin, but not genes encoding α1, α3, or β1 integrin, was predictive of metastatic dissemination and decreased survival. The predictive value of α2 expression persisted within both good-risk and poor-risk cohorts defined by estrogen receptor and lymph node status. Thus, the α2β1 integrin functionally inhibits breast tumor metastasis, and α2 expression may serve as an important biomarker of metastatic potential and patient survival.

Authors

Norma E. Ramirez, Zhonghua Zhang, Aasakiran Madamanchi, Kelli L. Boyd, Lynda D. O’Rear, Abudi Nashabi, Zhengzi Li, William D. Dupont, Andries Zijlstra, Mary M. Zutter

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Figure 5

α2β1 integrin expression inhibits migration, intravasation, and anchorage-independent growth in vitro.

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α2β1 integrin expression inhibits migration, intravasation, and anchorag...
(A) Primary WT/Neu or α2-null/Neu tumor cells stained with rhodamine-phalloidin (red) and DAPI (blue) were examined by immunofluorescence microscopy. Primary WT/Neu tumor cells exhibit an epithelial morphology with cobblestone-appearing colonies. In contrast, the α2-null/Neu tumor cells are mesenchymal in shape. Scale bar: 100 μm. (B and C) α2-null/Neu tumor cells exhibited significantly enhanced migration at 12 and 24 hours in a scratch assay. The straight lines in part C connect data points on cells from the same mouse. The rate of cell migration was significantly greater in cells from α2-null/Neu mice than WT/Neu mice (P = 0.05). (D) Morphogenesis of WT/Neu and α2-null/Neu tumor cells into 3D matrigel cultures. Scale bar: 100 μm. (E) Anchorage-independent colony assays were conducted in soft-agar. α2-null/Neu tumor cells generated significantly greater numbers of colonies than WT/Neu tumor cells. Each point represents the number of colonies 50 μm or greater in diameter generated from 10,000 primary tumor cells from an individual mouse. (F and G) α2-null/Neu tumor cells exhibit enhanced intravasation in comparison with WT/Neu tumor cells in vitro through a barrier of WT endothelial cells. Primary WT endothelial cells, stimulated with TNF, were labeled with CellTracer Vybrant CFDA SE (green) and seeded onto the bottom of a Transwell filter. The ability of WT/Neu or α2-null/Neu tumor cells, labeled with CellTracker Red CMTPX (red), to intravasate through the endothelial barrier in 8 hours was determined. The number of intravasated (red) cells was quantitated as mean ± SEM of 3 separate experiments carried out with primary cells from 3 different animals (P < 0.0003 by Mann-Whitney analysis).