Although the role of ELA in cancer has been investigated in a limited number of studies [20, 21], several studies have shown that apelin, which is the other endogenous ligand of APRLN, is overexpressed in many tumour tissues and cell lines, and the apelin/APLNR system plays a role in the regulation of cancer cell growth and migration [22–24]. The gene discussed is APLN; the disease is neoplasm.