G·A·B·B·A

To metastasise cancer cells must enter and then exit lymphatic and blood vessels, in a process called transendothelial migration (TEM), which requires cytoskeletal changes. Rho GTPases control signal transduction pathways affecting cytoskeletal dynamics and are often deregulated in metastatic human cancers. Therefore we aim to understand their role during cancer cell TEM. We carried out a siRNA-based adhesion screen of MDA-MB-231 cells to primary human umbilical vein endothelial cells (HUVECs) which revealed that RhoBTB1 is required for breast cancer cell adhesion to HUVECs. Furthermore RhoBTB1 is required for the subsequent steps of extravasation: time-lapse microscopy showed that the intercalation of MDA-MB-231 cells between endothelial cells is delayed. Using a transwell system we have observed that the transmigration of MDA-MB-231 cells through a monolayer of HUVECs is also reduced.We developed a 3D model for cancer cell TEM in which endothelial cells are grown on top of a thick collagen I gel. MDA-MB-231 can transmigrate in this system and invade the underlying matrix. Current studies focus on the signalling pathways regarding RhoBTB1 depletion in the context of MDA-MB-231 extravasation in 3D.