The latter non-specific effect of ANGPT2 and the need of hypoxia for inducing CXCR4 expression on all macrophages suggest that the CXCL12-CXCR4 axis as well as ANGPT2 might regulate interstitial migration of proangiogenic macrophages inside the tumour, rather than initial recruitment through blood vessels. This evidence concerns the gene CXCR4 and neoplasm.