MMP9 and neoplasm: Secondly, during tumor development, highly invasive tumor cells can secrete large amounts of matrix metalloproteinases (MMPs), such as MMP-2, MMP-9, and MMP-14, while the overexpression of MMPs can promote the degradation of ECM components, thereby increasing tumor cell migration, invasion, and the capacity for VM formation (Seftor et al., 2001; Cabral-Pacheco et al., 2020; Najafi et al., 2019; Cai et al., 2019; Sun et al., 2007).