MMP9 and gastric cancer: A variety of studies have observed that the single nucleotide polymorphisms (SNPs) matrix metalloproteinase-9 (MMP-9) gene may be associated with the risk of gastric cancer(GC), and a cytosine (C) to thymine (T) mutation at the -1562 site of the MMP-9 gene promoter is reported to be closely related to the susceptibility.