Endothelial RhoA Regulates Breast Cancer Metastasis

Abstract

Metastasis is the cause of more than 90% of cancer‐related deaths. An important step in metastatic process is the migration of the disseminating cancer cells through the endothelial monolayer during entrance or exit from the vasculature. Activation of endothelial RhoA‐ROCK pathway has been implicated in the regulation of vascular permeability in various pathophysiological conditions. In the present study, we have investigated the role of this pathway in trans‐endothelial migration and metastasis of breast cancer cells. RhoA activation was identified by RhoA pull‐down experiments of murine and human breast cancer cell supernatant on primary endothelial cells. Cancer cell trans‐endothelial migration efficiency was explored through an in vitro transwell‐based two‐cell co‐culture model. RhoA signaling pathway was blocked by both pharmacological inhibition and knockdown experiments. In vivo metastatic potential was identified by experimental metastasis models of murine and human breast cancer cell lines using endothelial‐specific RhoA‐deficient mice or clinically relevant ROCK inhibitors. We identified that the diverse metastatic potential of a panel of human breast cancer cell lines correlated with the RhoA activation efficiency of their supernatant on primary endothelial cells. Secretome analysis revealed that IL‐8 (over)expression was relevant to breast cancer cell aggressiveness and its functionality was tested with gain‐and loss‐of‐function experiments. In vivo, experimental metastasis experiments with the syngeneic breast cancer cell line E0771 showed that endothelial RhoA deficiency decreased the metastatic potential. Similar inhibition was obtained with treatment with the clinically‐relevant ROCK inhibitor, Fasudil, in experimental metastasis experiments of murine and human cell lines using immune‐competent and immune‐deficient mice respectively. Collectively, our in vitro and in vivo findings demonstrate that the endothelial RhoA‐ROCK pathway affects breast cancer trans‐endothelial migration and metastasis and propose endothelial RhoA inhibition as a novel therapy for breast cancer metastases.This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.