Another report suggested that hypoxia-inducible chemotactic factors such as the CXCR4 ligand CXCL12 and Angiopoietin-2 (Ang-2) promote recruitment of Tie2-expressing monocytes in hypoxic areas of tumours and differentiate them into Tie2-expressing macrophages (Murdoch et al, 2007). This evidence concerns the gene TEK and neoplasm.