To identify modulators of endothelial tube and lumen formation using the new optimized assay , we performed a high - content screening of a compound library containing 150 FDA - approved cardiovascular drugs in a 96 - well plate format at a final concentration of 5 µM in duplicate . Sunitinib was used as a positive control . Using the image analysis approach , we quantified two morphological parameters : total tube length and lumen area . Treated wells were normalized to negative control ( vehicle , DMSO ) wells . Compounds that changed the total tube length or lumen area by > 4 × SD from the mean of the DMSOtreated control wells were considered enhancer hits ( Figure 2a ) . Of the 150 compounds , we found that several L - type calcium channel blockers with different chemical structures could enhance the formation of lumen compared to controls ( Figure 2b ) . Lacidipine was selected for further validation and mechanistic studies . Dose - dependent effects of Lacidipine on the lumen area confirmed the screen results and demonstrated that the half - maximal effective concentration ( EC 50 ) of Lacidipine is ( 250 nmol / l ) in this assay ( Figure 2c ) . Our data shows that L - type calcium blockers enhance the endothelial lumen formation in our assay .