Rhophilin-associated tail protein 1 promotes migration and metastasis in triple negative breast cancer via activation of RhoA.

Triple negative breast cancer (TNBC) is the most aggressive breast cancer subtype with high motile and invasive capacity that contributes to metastasis. Understanding the mechanisms for the motility of TNBC might provide novel targetable vulnerabilities of the tumors. Herein, we find that Rhophilin-associated tail protein 1 (ROPN1) is selectively overexpressed in human TNBC cell lines and tissues. Overexpression of ROPN1 promotes, while silencing of ROPN1 inhibits the robust migration, invasion, and in vivo metastasis of TNBC cells. Moreover, we find that ROPN1 activates RhoA signaling via rhophilin-1 (RHPN1), leading to enhanced actin stress fibers formation in TNBC cells. RhoA signaling is demonstrated to be essential for ROPN1-mediated migration and metastasis of TNBC cells. Finally, we find that high levels of ROPN1 are significantly associated distant metastasis and predicted poor prognosis in patients with breast cancer. These findings reveal a novel mechanism for the high motility and metastasis of TNBC cells, suggesting that ROPN1 might be a potential prognostic marker and therapeutic target.