MMP1 and neoplasm: MMP-1, in particular, has been shown to promote angiogenesis and bone metastasis [48], whereas MMP-9, which is released by tumor-infiltrating neutrophils and macrophages, acts as an angiogenic factor, triggering the release of vascular endothelial growth factor (VEGF) and basic fibroblast growth factor (bFGF), both of which interact with the ECM [49,50].