CPT inhibits LEC tube formation in a concentration- and time-dependent manner. LECs were treated with CPT (0–10 µM) for 24 h, or CPT (10 µM) for 0–24 h, followed by tube formation assay and morphological analysis, as described in “Materials and Methods”. Representative images are shown in (A) and (B), respectively. Bar = 100 µm. The length of tube-like formation was evaluated by NIH Image J software. Quantitative data are presented as mean ± SD (n = 3) in (C) and (D), respectively. *P < 0.05, **P < 0.01, difference vs. control group.