Serum-derived factors in breast cancer patients change barrier properties of the human in vitro blood-brain barrier model
Curtaz C.1, Schmitt C.2, Herbert S.-L.1, Quenzer A.1, Feldheim J.3, Schlegel N.4, Gosselet F.5, Hagemann C.3, Roewert N.2, Meybohm P.2, Wöckel A.1, Burek M.2
1University of Würzburg, Department of Gynecology and Obstetrics, Würzburg, Deutschland, 2University of Würzburg, Department of Anaesthesia and Critical Care, Würzburg, Deutschland, 3University of Würzburg, Department of Neurosurgery, Tumor Biology Laboratory, Würzburg, Deutschland, 4University of Würzburg, Department of Surgery I, Würzburg, Deutschland, 5Université d'Artois, Blood-Brain Barrier Laboratory, Lens, Frankreich

Introduction: Metastases are still the most threatening event in breast cancer (BC) patients' medical history, while brain metastases correlate with the worst overall survival. The key event for the metastatic progression of BC into the brain is the migration of cancer cells across the blood-brain barrier (BBB). In this study, we examined the effects of serum factors from BC patients on BBB integrity in vitro.
Material and methods: We collected serum samples from healthy donors, BC patients with primary tumor, and BC patients with brain, bone or visceral metastases. Cytokine levels were measured in patients' sera using immunosassays. Human CD34+ cells-derived endothelial cells were cultured with pericytes to induce BBB properties. We utilized paracellular permeability measurements, immunofluorescent staining, Western blot and mRNA analysis to examine the effects of 2% patient sera on the BBB in vitro.
Results: We analyzed the concentrations of BCA-1 (CXCL13), CCL20, fractalkine (CX3CL1), MCP-1 (CCL2), RANTES (CCL5) and SDF-1a/b (CXCL12) in patients' sera. Fractalkine and BCA-1 were significantly increased in BC patients' sera with brain metastases. CCL20 showed a similar trend. Elevated fractalkine levels were associated with the tumor's estrogen/progesterone receptor status. Treatment of the in vitro BBB model with BC patients' sera with cerebral metastases resulted in delocalization of the tight junction protein claudin-5, increased paracellular permeability and changes in gene expression.
Conclusion: Serum from BC patients with cerebral metastases can affect the integrity of the BBB in vitro. Increased concentrations of specific cytokines in BC patients with cerebral metastases may contribute to this effect.