MMP9 and neoplasm: Peripheral monocytes accumulate into the tumor tissue and are differentiated into TAMs under the action of different tumor-derived chemokines, such as VEGFA and CCL-2; TAMs are able to divide into tumor-supportive M2-polarized macrophages, which promote angiogenesis by secreting different proangiogenic factors, including VEGFA, MMP-9, bFGF and ADM [25,26].