MMP9 and gastric cancer: In this study, the constructed PNI gene signature expression in gastric cancer is meta-analyzed, and the consensus expressions of C-X-C motif chemokine ligand 8 (CXCL8) and matrix metallopeptidase 9 (MMP9) are screened, indicating that a CXCL8/MMP9-relevant PNI process could be targeted to prevent further metastasis.