Cell adhesion molecule BVES functions as a suppressor of tumor cells extrusion in hepatocellular carcinoma metastasis

Background: Tumor cells detachment from primary lesions is an early event for hepatocellular carcinoma (HCC) metastasis, in which cell adhesion molecules play an important role. The role of mechanical crowding has attracted increasing attention. Previous studies have found that overcrowding can induce live cells extrusion to maintain epithelial cell homeostasis, and normally, live extruded cells eventually die through a process termed anoikis, suggesting the potential of tumor cells resistant to anoikis might initiate metastasis from primary tumors by cell extrusion. We have demonstrated transmembrane adhesion molecule blood vessel epicardial substance (BVES) suppression as an early event in HCC metastasis. However, whether its suppression is involved in HCC cell extrusion, especially in HCC metastasis, remains unknown. This study aims to investigate the role of BVES in tumor cells extrusion in HCC metastasis, as well as the underlying mechanisms.

Methods: Cells extrusion was observed by silicone chamber, petri dish inversion, and three-dimensional Cell Culture model. Polymerase chain reaction, western blotting, immunohistochemistry, immunofluorescence, co-immunoprecipitation, and RhoA activity assays were used to explore the underlying mechanisms of cell extrusion regulated by BVES. An orthotopic xenograft model was established to investigate the effects of BVES and cell extrusion in HCC metastasis in vivo.

Results: Tumor cell extrusion was observed in HCC cells and tissues. BVES expression was decreased both in HCC and extruded tumor cells. BVES overexpression led to the decrease in HCC cells extrusion in vitro and in vivo. Moreover, our data showed that BVES co-localized with ZO-1 and GEFT, regulating ZO-1 expression and localization, and GEFT distribution, thus modulating RhoA activity.

Conclusion: The present study revealed that BVES downregulation in HCC enhanced tumor cells extrusion, thus promoting HCC metastasis, which contributed to a more comprehensive understanding of tumor metastasis, and provided clues for developing novel HCC therapy strategies. Video abstract.