CXCL12 and neoplasm: Hypoxia induced by vessel targeting agents upregulates the expression of stromal-derived factor-1α (SDF-1α), which is a chemoattractant of CD45+myeloid cells and induces recruitment of Tie2, VEGFR-1, CD11b and F4/80-expressing subtypes of myeloid cells; myeloid cells then promote angiogenesis and induce tumor cell intravasation, dissemination and metastasis [123,124].