RESUMO
Platelet-derived growth factor B (PDGFB) plays a crucial role in recruitment of PDGF receptor ß-positive pericytes to blood vessels. The endothelium is an essential source of PDGFB in this process. Platelets constitute a major reservoir of PDGFB and are continuously activated in the tumor microenvironment, exposing tumors to the plethora of growth factors contained in platelet granules. Here, we show that tumor vascular function, as well as pericyte coverage is significantly impaired in mice with conditional knockout of PDGFB in platelets. A lack of PDGFB in platelets led to enhanced hypoxia and epithelial-to-mesenchymal transition in the primary tumors, elevated levels of circulating tumor cells, and increased spontaneous metastasis to the liver or lungs in two mouse models. These findings establish a previously unknown role for platelet-derived PDGFB, whereby it promotes and maintains vascular integrity in the tumor microenvironment by contributing to the recruitment of pericytes. SIGNIFICANCE: Conditional knockout of PDGFB in platelets demonstrates its previously unknown role in the maintenance of tumor vascular integrity and host protection against metastasis.
Assuntos
Movimento Celular , Endotélio Vascular/metabolismo , Pericitos/fisiologia , Proteínas Proto-Oncogênicas c-sis/fisiologia , Animais , Vasos Sanguíneos , Neoplasias do Colo/irrigação sanguínea , Transição Epitelial-Mesenquimal , Matriz Extracelular , Técnicas de Inativação de Genes , Hibridização Genética , Neoplasias Hepáticas/secundário , Neoplasias Pulmonares/secundário , Melanoma/irrigação sanguínea , Melanoma/secundário , Camundongos , Células Neoplásicas Circulantes , Neoplasias Pancreáticas , Pericitos/metabolismo , Ativação Plaquetária/fisiologia , Proteínas Proto-Oncogênicas c-sis/deficiência , Proteínas Proto-Oncogênicas c-sis/genética , Receptor beta de Fator de Crescimento Derivado de Plaquetas/genética , Receptor beta de Fator de Crescimento Derivado de Plaquetas/metabolismo , Trombocitopenia , Hipóxia Tumoral , Microambiente TumoralRESUMO
Platelets can promote several stages of the metastatic process and thus contribute to malignant progression. As an example, platelets promote invasive properties of tumor cells by induction of epithelial to mesenchymal transition (EMT). In this study, we show that tumor necrosis factor receptor-associated factor (TRAF) family member-associated NF-κB activator (TANK)-binding kinase 1 (TBK1) is a previously unknown mediator of platelet-induced EMT in mammary carcinoma cells. Coculture of 2 mammary carcinoma cell lines, Ep5 from mice and MCF10A(MII) from humans, with isolated platelets induced morphologic as well as molecular changes characteristic of EMT, which was paralleled with activation of TBK1. TBK1 depletion using small interfering RNA impaired platelet-induced EMT in both Ep5 and MCF10A(MII) cells. Furthermore, platelet-induced activation of the NF-κB subunit p65 was suppressed after TBK1 knockdown, demonstrating that TBK1 mediates platelet-induced NF-κB signaling and EMT. Using an in vivo metastasis assay, we found that depletion of TBK1 from mammary carcinoma cells during in vitro preconditioning with platelets subsequently suppressed the formation of lung metastases in mice. Altogether, these results suggest that TBK1 contributes to tumor invasiveness and may be a driver of metastatic spread in breast cancer.-Zhang, Y., Unnithan, R. V. M., Hamidi, A., Caja, L., Saupe, F., Moustakas, A., Cedervall, J., Olsson, A.-K. TANK-binding kinase 1 is a mediator of platelet-induced EMT in mammary carcinoma cells.