Abstract
BackgroundIntegrin-mediated platelet-tumor cell contacting plays an important role in promoting epithelial-mesenchymal transition (EMT) transformation of tumor cells and cancer metastasis, but whether it occurs in breast cancer cells is not completely clear.ObjectiveThe purpose of this study was to investigate the role of integrin α2β1 in platelet contacting to human breast cancer cell line MCF-7 and its effect on the EMT and the invasion of MCF-7 cells.MethodsHuman platelets were activated by thrombin, and separated into pellets and releasates before the co-incubation with MCF-7 cells. Cell invasion was evaluated by transwell assay. The surface integrins on pellets and MCF-7 cells were inhibited by antibodies. The effect of integrin α2β1 on Wnt-β-catenin pathway was assessed by integrin α2β1-silencing and Wnt-β-catenin inhibitor XAV. The therapeutic effect of integrin α2β1-silencing was confirmed in the xenograft mouse model.ResultsPellets promote the invasion and EMT of MCF-7 cells via direct contacting of surface integrin α2β1. The integrin α2β1 contacting activates Wnt-β-catenin pathway and promotes the expression of EMT proteins in MCF-7 cells. The activated Wnt-β-catenin pathway also promotes the autocrine of TGF-β1 in MCF-7 cells. Both Wnt-β-catenin and TGF-β1/pSmad3 pathways promote the expression of EMT proteins. Integrin α2β1-silencing inhibits breast cancer metastasis in vivo.ConclusionsThe direct interaction between platelets and tumor cells exerts its pro-metastatic function via surface integrin α2β1 contacting and Wnt-β-catenin activation. Integrin α2β1-silencing has the potential effect of inhibiting breast cancer metastasis.
Highlights
Integrin-mediated platelet-tumor cell contacting plays an important role in promoting epithelialmesenchymal transition (EMT) transformation of tumor cells and cancer metastasis, but whether it occurs in breast cancer cells is not completely clear
The direct interaction between platelets and tumor cells exerts its pro-metastatic function via surface integrin α2β1 contacting and Wnt-β-catenin activation
The results showed that both platelets and pellets promoted the invasion of MCF-7 cells, but releasates did not significantly affect the invasion of MCF-7 cells (Fig. 1a)
Summary
Integrin-mediated platelet-tumor cell contacting plays an important role in promoting epithelialmesenchymal transition (EMT) transformation of tumor cells and cancer metastasis, but whether it occurs in breast cancer cells is not completely clear. The increased level of platelets was correlated with tumor progression, recurrence and distant metastasis in various cancer types [2, 3]. It has been reported that platelet-derived α-granules containing transforming growth factor-β1 (TGF-β1) increased the growth of primary tumors in murine models of ovarian cancer [9, 10]. Labelle et al demonstrated that direct platelet-tumor cell contacting and platelet-derived TGF-β1 synergistically activate the TGF-β1/Smad pathway in cancer cells, resulting in their EMT transformation and enhanced metastasis [13]. The mechanism underlying the direct interaction between platelets and breast cancer cells is largely unknown
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