Platelet integrin α6β1 controls lung metastasis through direct binding to cancer cell–derived ADAM9
Elmina Mammadova-Bach, Paola Zigrino, Camille Brucker, Catherine Bourdon, Monique Freund, Adèle De Arcangelis, Scott I. Abrams, Gertaud Orend, Christian Gachet, Pierre Henri Mangin
Elmina Mammadova-Bach, Paola Zigrino, Camille Brucker, Catherine Bourdon, Monique Freund, Adèle De Arcangelis, Scott I. Abrams, Gertaud Orend, Christian Gachet, Pierre Henri Mangin
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Research Article Hematology Oncology

Platelet integrin α6β1 controls lung metastasis through direct binding to cancer cell–derived ADAM9

Abstract

Metastatic dissemination of cancer cells, which accounts for 90% of cancer mortality, is the ultimate hallmark of malignancy. Growing evidence suggests that blood platelets have a predominant role in tumor metastasis; however, the molecular mechanisms involved remain elusive. Here, we demonstrate that genetic deficiency of integrin α6β1 on platelets markedly decreases experimental and spontaneous lung metastasis. In vitro and in vivo assays reveal that human and mouse platelet α6β1 supports platelet adhesion to various types of cancer cells. Using a knockdown approach, we identified ADAM9 as the major counter receptor of α6β1 on both human and mouse tumor cells. Static and flow-based adhesion assays of platelets binding to DC-9, a recombinant protein covering the disintegrin-cysteine domain of ADAM9, demonstrated that this receptor directly binds to platelet α6β1. In vivo studies showed that the interplay between platelet α6β1 and tumor cell–expressed ADAM9 promotes efficient lung metastasis. The integrin α6β1–dependent platelet-tumor cell interaction induces platelet activation and favors the extravasation process of tumor cells. Finally, we demonstrate that a pharmacological approach targeting α6β1 efficiently impairs tumor metastasis through a platelet-dependent mechanism. Our study reveals a mechanism by which platelets promote tumor metastasis and suggests that integrin α6β1 represents a promising target for antimetastatic therapies.

Authors

Elmina Mammadova-Bach, Paola Zigrino, Camille Brucker, Catherine Bourdon, Monique Freund, Adèle De Arcangelis, Scott I. Abrams, Gertaud Orend, Christian Gachet, Pierre Henri Mangin

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Figure 2

Platelet integrin α6β1 deficiency or blockade impairs platelet and tumor cell interaction.

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Platelet integrin α6β1 deficiency or blockade impairs platelet and tumor...
Platelet adhesion to tumor cells was quantified based on the fluorescence detection of RAM.1-labeled platelets, as described in Methods. (A) Representative epifluorescence microcopy images of RAM.1-Alexa 488–labeled mouse PF4-Cre-α6+/+ and PF4-Cre-α6–/– platelets (green) adhering to AT-3 tumor cells. Scale bar: 50 μm. (B and C) Quantification of the fluorescent signal corresponding to the amount of platelets allowed to adhere to tumor cells. (B) Washed PF4-Cre-α6+/+ or PF4-Cre-α6–/– mouse platelets were allowed to adhere on AT-3 breast cancer, MC38 colon carcinoma, and B16F10 melanoma cells. (C) Washed human platelets were treated with an irrelevant IgG (control) or blocking antibodies against α6 (GoH3) or β1 (P5D2) integrin (10 μg/ml) and cultured on MDA-MB-231, SKRB-3 breast, and LoVo colon cancer cells. *P < 0.05, **P < 0.01, ***P < 0.001, Mann-Whitney test. (D) Experimental design. c-mpl–/– mice were injected with RAM.1-cy3–labeled PF4-Cre-α6+/+ or PF4-Cre-α6–/– platelets (red) and CFSE-labeled AT-3 tumor cells (green). (E) Two hours after injection, mice were euthanized and lungs were collected, and the colocalization of AT-3 tumor cells with platelets was determined by fluorescence microscopy. Nuclei were stained with DAPI (blue). Scale bar: 20 μm. (F) Quantification of the number of tumor cells surrounded by platelets. *P < 0.05, Mann-Whitney test. (G) WT or c-mpl–/– mice were transfused or not with PF4-Cre-α6+/+ and PF4-Cre-α6–/– platelets. In parallel, these mice were also injected with AT-3 cells through a different tail vein. Experimental lung metastasis was determined 20 days of after injection. Numbers of metastatic foci in lung tissues of AT-3–injected WT or c-mpl–/– mice. *P < 0.05, **P < 0.01, Mann-Whitney test. Each point represents (B, F, and G) an individual mouse or (C) healthy human donor. (B, C, F, and G) Box-and-whisker plots were used to graphically represent the median (line within box), upper and lower quartile (bounds of box), and maximum and minimum values (bars). *P < 0.05, **P < 0.01, ***P < 0.001.