Metastatic cancer cells activate endothelial RhoA-ROCK pathway for trans-endothelial migration

Metastasis is the process through which tumor cells disseminate from the primary tumor and colonize in distant parts of the body. Two of the steps in the metastatic process are the trans-migration of cancer cells through the endothelial lining of blood and lymphatic vessels, during entrance (intravasation) and exit (extravasation) from the vascular system. We and others have shown that the endothelial RhoA pathway plays important role in endothelial permeability. Translating these findings in the metastasis context we aim to explore the role of endothelial RhoA signaling pathway on cancer cell trans-endothelial migration and metastasis. In vitro, we have established a quantifiable, highly reproducible, transwell-based, two-cell co-culture model of trans-endothelial migration, where fluorescently-labeled cancer cells transmigrate through an endothelial monolayer. Pharmacological and molecular biology approaches were incorporated to dissect the role of endothelial RhoA signaling pathway. Primary and immortalized endothelial cells were used and cancer cells of both mouse and human origin were tested. In all cases, conditioned media from the cancer cells activated endothelial RhoA. Blockade of the RhoA pathway inhibited cancer cell trans-endothelial migration. In vivo, syngeneic and human cancer cell lines were tested in tail-vein and intra-cardiac models of experimental metastasis. We observed decreased lung metastatic nodules in endothelial-specific RhoA-deficient mice, compared to the littermate controls. Treatment with a clinically-relevant inhibitor of the RhoA pathway, Fasudil, also decreased the metastatic colonization of both human and cancer cells. The above findings demonstrate that the endothelial RhoA pathway has a pivotal role on cancer cell trans-endothelial migration. Citation Format: Md Sanaullah Sajib, Fatema Tuz Zahra, Jee Hyun Park, Paul Tullar, Sanjay K. Srivastava, Ulrich Bickel, Constantinos M Mikelis. Metastatic cancer cells activate endothelial RhoA-ROCK pathway for trans-endothelial migration [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 1029.