Ephrin-A1 is a member of the A-type ephrin family of cell surface proteins that function as ligands for the A-type Eph receptor tyrosine kinase family. Ephrin-A1 can be induced by TNF and IL1B. Its expression levels can be down-regulated in primary glioma tissues compared to the normal tissues. The soluble monomeric form is expressed in the glioblastoma multiforme (GBM) and breast cancer cells. Soluble Ephrin-A1 is necessary for the transformation of HeLa and SK-BR3 cells and participates in the relocalization of EPHA2 away from sites of cell-cell contact during transformation. Ephrin-A1 plays an important role in angiogenesis and tumor neovascularization.