MMP9 and gastric cancer: In 2021, Liu et al. evaluated the capacity of melatonin to decrease cell proliferation in MGC-803 and SGC-7901 gastric cancer cell lines and found that melatonin directly regulates the production and secretion of matrix metalloproteinase 2 (MMP2) and MMP9 in CAFs, influencing collagen rearrangement in the ECM [96].