Endothelial-mesenchymal transition of brain endothelial cells: possible role during metastatic extravasation.
Cancer progression towards metastasis follows a defined sequence of events described as the metastatic cascade. For extravasation and transendothelial migration metastatic cells interact first with endothelial cells. Yet the role of endothelial cells during the process of metastasis formation and extravasation is still unclear, and the interaction between metastatic and endothelial cells during transendothelial migration is poorly understood. Since tumor cells are well known to express TGF-β, and the compact endothelial layer undergoes a series of changes during metastatic extravasation (cell contact disruption, cytoskeletal reorganization, enhanced contractility), we hypothesized that an EndMT may be necessary for metastatic extravasation. We demonstrate that primary cultured rat brain endothelial cells (BEC) undergo EndMT upon TGF-β1 treatment, characterized by the loss of tight and adherens junction proteins, expression of fibronectin, β1-integrin, calponin and α-smooth muscle actin (SMA). B16/F10 cell line conditioned and activated medium (ACM) had similar effects: claudin-5 down-regulation, fibronectin and SMA expression. Inhibition of TGF-β signaling during B16/F10 ACM stimulation using SB-431542 maintained claudin-5 levels and mitigated fibronectin and SMA expression. B16/F10 ACM stimulation of BECs led to phosphorylation of Smad2 and Smad3. SB-431542 prevented SMA up-regulation upon stimulation of BECs with A2058, MCF-7 and MDA-MB231 ACM as well. Moreover, B16/F10 ACM caused a reduction in transendothelial electrical resistance, enhanced the number of melanoma cells adhering to and transmigrating through the endothelial layer, in a TGF-β-dependent manner. These effects were not confined to BECs: HUVECs showed TGF-β-dependent SMA expression when stimulated with breast cancer cell line ACM. Our results indicate that an EndMT may be necessary for metastatic transendothelial migration, and this transition may be one of the potential mechanisms occurring during the complex phenomenon known as metastatic extravasation.
Institute of Biophysics, Biological Research Centre, Hungarian Academy of Sciences, Temesvári krt. 62, 6726, Szeged, Hungary; Institute of Life Sciences, Vasile Goldis Western University of Arad, Liviu Rebreanu Str. 86, 310414, Arad, Romania.
István A
IA
Krizbai
Department of Pathophysiology, Semmelweis University, Nagyvárad Square 4, 1089, Budapest, Hungary.
Ákos
Á
Gasparics
Institute of Biophysics, Biological Research Centre, Hungarian Academy of Sciences, Temesvári krt. 62, 6726, Szeged, Hungary.
Péter
P
Nagyőszi
Institute of Biophysics, Biological Research Centre, Hungarian Academy of Sciences, Temesvári krt. 62, 6726, Szeged, Hungary.
Csilla
C
Fazakas
Institute of Biophysics, Biological Research Centre, Hungarian Academy of Sciences, Temesvári krt. 62, 6726, Szeged, Hungary.
Judit
J
Molnár
Institute of Biophysics, Biological Research Centre, Hungarian Academy of Sciences, Temesvári krt. 62, 6726, Szeged, Hungary.
Imola
I
Wilhelm
Department of Pathophysiology, Semmelweis University, Nagyvárad Square 4, 1089, Budapest, Hungary.
Rita
R
Bencs
Department of Pathophysiology, Semmelweis University, Nagyvárad Square 4, 1089, Budapest, Hungary; Pediatrics and Nephrology Research Group, Hungarian Academy of Sciences and Semmelweis University, Nagyvárad Square 4, 1089, Budapest, Hungary.
László
L
Rosivall
Department of Pathophysiology, Semmelweis University, Nagyvárad Square 4, 1089, Budapest, Hungary.
Attila
A
Sebe
D000818:Animals; D001549:Benzamides / Q000494:pharmacology; D001921:Brain / Q000166:cytology* / Q000187:drug effects; D045744:Cell Line, Tumor; D002478:Cells, Cultured; D017077:Culture Media, Conditioned / Q000494:pharmacology; D004149:Dioxoles / Q000494:pharmacology; D042783:Endothelial Cells / Q000187:drug effects / Q000502:physiology*; D058750:Epithelial-Mesenchymal Transition; D005786:Gene Expression Regulation / Q000187:drug effects*; D061307:Human Umbilical Vein Endothelial Cells; D006801:Humans; D061986:MCF-7 Cells; D051379:Mice; D009362:Neoplasm Metastasis; D051381:Rats; D053773:Transforming Growth Factor beta1 / Q000037:antagonists & inhibitors / Q000494:pharmacology*
C459179:4-(5-benzo(1,3)dioxol-5-yl-4-pyridin-2-yl-1H-imidazol-2-yl)benzamide; D001549:Benzamides; D017077:Culture Media, Conditioned; D004149:Dioxoles; D053773:Transforming Growth Factor beta1