DLL4 and urinary bladder cancer: Although some traditional vascular markers, such as vascular endothelial growth factor (VEGF), vascular endothelial growth factor receptor 2 (VEGFR2), and delta-like 4 (DLL4), have been studied in the diagnosis and treatment of bladder cancer (41, 42), their ability to predict clinical prognosis is limited, resulting in an unvalidated therapeutic effect in UCB (43).