S100A9 and gastric cancer: Matrix metalloproteinases (MMPs) are known to have key roles in tumor cell migration and invasion.31 S100A8 and S100A9 were previously shown to stimulate MMP2 and MMP9 expression in breast and gastric cancer cells.32, 33 We found that S100A8 and S100A9 had similar effects in MC38 and LLC cells.