Identification\nof FGG as a Biomarker in Early Gastric\nCancer via Tissue Proteomics and Clinical Verification

Early and accurate diagnosis of gastric cancer (GC) is\nessential\nfor reducing mortality and improving patient well-being. However,\nmethods for the early diagnosis of GC are still lacking. In this study,\nby isobaric tagging for relative and absolute quantitation (iTRAQ),\nwe identified 336 proteins that overlapped among the upregulated differentially\nexpressed proteins (DEPs) in early gastric cancer (EGC) versus progressive\ngastric cancer (PGC), upregulated DEPs in EGC versus nongastric cancer\n(NGC), and nonsignificant proteins in EGC versus NGC. These DEPs were\ninvolved primarily in the neutrophil-related immune response. Network\nanalysis of proteins and pathways revealed that fibrinogen α\n(FGA), β (FGB), and γ (FGG) are candidates for distinguishing\nEGC. Furthermore, parallel reaction monitoring (PRM), immunohistochemistry\n(IHC), and Western blot (WB) assays of clinical samples confirmed\nthat, compared with that in PGC and NGC, only FGG was uniquely and\nsignificantly upregulated in the gastric mucosa of EGC. Our results\ndemonstrated that FGG in the gastric mucosa could be a novel biomarker\nto diagnose EGC patients via endoscopy.