MMP9 and cancer: Secondly, according to the results of clinical correlation analysis, the expression of PTGS2, MMP9, MMP2 and CXCR4 genes in gastric cancer is higher than that in normal gastric tissues, and the expression of PPARG gene in gastric cancer is lower.[61–65] This indicates that the expression of the above genes causes obvious abnormal changes in cancer cells and tissues, and affects the growth status and proliferation rate of tumors.