They contribute to tumor development by producing reactive oxygen species (ROS) and reactive nitrogen species (RNS), as well as stimulating tumor cell proliferation by secreting neutrophil elastase (NE), which enhances tumor invasion, metastasis progression [21], and the secretion of matrix metalloproteinase 9 (MMP9), which activates pro-TGF-β and pro-TNF-α growth factors [22]. The gene discussed is MMP9; the disease is neoplasm.