Fibrinogen Alpha Chain Knockout Promotes Tumor Growth and Metastasis through Integrin–AKT Signaling Pathway in Lung Cancer

Abstract

Fibrinogen is an extracellular matrix protein composed of three polypeptide chains with fibrinogen alpha (FGA), beta (FGB) and gamma (FGG). Although fibrinogen and its related fragments are involved in tumor angiogenesis and metastasis, their functional roles are incompatible. A recent genome-scale screening reveals that loss of <i>FGA</i> affects the acceleration of tumor growth and metastasis of lung cancer, but the mechanism remains elusive. We used CRISPR/Cas9 genome editing to knockout (KO) <i>FGA</i> in human lung adenocarcinoma (LUAD) cell lines A549 and H1299. By colony formation, transwell migration and matrix invasion assays, <i>FGA</i> KO increased cell proliferation, migration, and invasion but decreased the expressions of epithelial-mesenchymal transition marker E-cadherin and cytokeratin 5/8 in A549 and H1299 cells. However, administration of FGA inhibited cell proliferation and migration but induced apoptosis in A549 cells. Of note, <i>FGA</i> KO cells indirectly cocultured by transwells with <i>FGA</i> wild-type cells increased FGA in the culture medium, leading to decreased migration of <i>FGA</i> KO cells. Furthermore, our functional analysis identified a direct interaction of FGA with integrin α5 as well as FGA-integrin signaling that regulated the AKT-mTOR signaling pathway in A549 cells. In addition, we validated that <i>FGA</i> KO increased tumor growth and metastasis through activation of AKT signaling in an A549 xenograft model. IMPLICATIONS: These findings demonstrate that that loss of <i>FGA</i> facilities tumor growth and metastasis through the integrin-AKT signaling pathway in lung cancer.