GEF-H1 drives breast cancer cells to tumor progression

Rho GTPases are involved in several biological processes, including cytoskeletal remodeling, gene transcription, cell proliferation and differentiation. Dysregulation of Rho GTPases activity can lead to enhanced tumor cell proliferation and metastasis. Rho guanine nucleotide exchange factor-H1 (GEFH1) is a RhoA activator that is associated with microtubules (MT) and its localization and activity are regulated, in part, by MT and fibronectin-binding integrins. Our findings showed that GEF-H1 expression is significantly higher in human breast cancer biopsies than in normal tissues. Moreover, patients with increased GEF-H1 expression had a lower survival rate and a higher incidence of metastasis. We generated a GEF-H1 knockout (KO) breast cancer cell line and observed a significant reduction in the number of focal adhesions, formation of stress fibers, and activation of downstream signaling pathways. Concordantly, cell proliferation, migration, adhesion, and invasion were reduced. Furthermore, when GEF-H1 knockout (KO) cells were orthotopically implanted into the mammary fat pads of BALB/c mice, a significant decrease was observed in both tumor formation and lung metastasis compared to control breast cancer cells. These results suggest that GEF-H1/RhoA activation mediates cytoskeletal remodeling and signaling pathways critical for breast cancer cell proliferation, migration, and invasion. In vivo assays and human biopsy studies further support GEF-H1 as a potential biomarker of breast tumor progression.