CDC73 suppresses lung adenocarcinoma via the PTEN/AKT pathway and exhibits biomarker and functional potential in extracellular vesicles.

CDC73 is a canonical tumor suppressor; however, its biological functions in lung adenocarcinoma (LUAD) and the extracellular vesicle (EV)-mediated mechanisms through which it exerts its effects remain unclear. In this study, we systematically evaluated the diagnostic value, biological functions, and EV-mediated regulatory roles of CDC73 in LUAD. First, quantitative proteomic analysis was performed on plasma-derived EVs from six patients with early-stage LUAD and three healthy donors, followed by further validation of EV-borne CDC73 expression in plasma-derived EV samples from eight LUAD patients and eight healthy donors. We found that the level of EV-borne CDC73 protein (EV-CDC73) was significantly reduced in LUAD, indicating its potential value as a diagnostic liquid-biopsy biomarker. To define its functional role, we established LUAD cell lines stably overexpressing CDC73 (A549^OE and H1299^OE) and performed rescue experiments in combination with PTEN knockdown using siRNA. The tumor-suppressive effects of CDC73 were systematically assessed through experiments examining cell proliferation, cell-cycle progression, apoptosis, migration, and related molecular mechanisms. Meanwhile, EVs were isolated by ultracentrifugation from the conditioned media of A549, H1299, and human bronchial epithelial (HBE) cells to analyze the effects of EVs with different CDC73 levels on recipient A549 and HBE cells, and xenograft models were used for in vivo validation. The results showed that CDC73 overexpression markedly inhibited LUAD cell proliferation and migration, induced G1-phase arrest, and promoted apoptosis. Mechanistically, CDC73 exerted its tumor-suppressive effects by upregulating PTEN and inhibiting AKT activation, whereas PTEN knockdown partially reversed these effects. In vivo experiments further confirmed that CDC73 overexpression suppressed tumor growth and migration. In addition, EVs derived from LUAD cells with high CDC73 expression showed a reduced ability to induce malignant transformation-related phenotypes in HBE cells and suppressed the PTEN/AKT signaling axis; conversely, EVs derived from HBE cells with high CDC73 expression inhibited the malignant progression of LUAD cells. Collectively, CDC73 suppresses the malignant progression of LUAD through the PTEN/AKT signaling axis, while EV-borne CDC73 not only has potential diagnostic value but also directly regulates malignant phenotypes in recipient cells, highlighting its translational potential in the diagnosis and treatment of LUAD.