EphB4 as a Novel Target for the EGFR-Independent Suppressive Effects of Osimertinib on Cell Cycle Progression in Non-Small Cell Lung Cancer

Osimertinib is the latest generation epidermal growth factor receptor (EGFR)-tyrosine kinase inhibitor used for patients with EGFR-mutated non-small cell lung cancer (NSCLC). We aimed to explore the novel mechanisms of osimertinib by particularly focusing on EGFR-independent effects, which have not been well characterized. We explored the EGFR-independent effects of osimertinib on cell proliferation using NSCLC cell lines, an antibody array analysis, and the association between the action of osimertinib and the ephrin receptor B4 (EphB4). We also studied the clinicopathological significance of EphB4 in 84 lung adenocarcinoma patients. Osimertinib exerted significant inhibitory effects on cell growth and cell cycle progression by promoting the phosphorylation of p53 and p21 and decreasing cyclin D1 expression independently of EGFR. EphB4 was significantly suppressed by osimertinib and promoted cell growth and sensitivity to osimertinib. The EphB4 status in carcinoma cells was positively correlated with tumor size, T factor, and Ki-67 labeling index in all patients and was associated with poor relapse-free survival in EGFR mutation-positive patients. EphB4 is associated with the EGFR-independent suppressive effects of osimertinib on cell cycle and with a poor clinical outcome. Osimertinib can exert significant growth inhibitory effects in EGFR-mutated NSCLC patients with a high EphB4 status.