MMRN2 binding is the first description of an extracellular ligand for CD93 and explains previous observations, such as the ability of CD93-CTLD-Fc to stain endothelium in human tonsils and CD93 roles in cell adhesion.30, 31 CD93 is also important in endothelial migration and tube formation, CD93-deficient mice exhibit angiogenesis defects in tumour models phenocopying observations made for CLEC14A.2, 3, 5, 7, 32 We hypothesize that such effects are potentially due to no longer being present to bind MMRN2. This evidence concerns the gene CLEC14A and neoplasm.