That apelin signaling is instrumental for cell attraction was first shown for APLNR-transfected cell lines [20,21] and then verified for immortalized and primary vascular endothelial cells [19,22,23], vascular smooth muscle cells [24,25], lymphatic endothelial cells [26], and one tumor cell line (lung adenocarcinoma cell line A549) [27]. This evidence concerns the gene APLN and neoplasm.