胃癌 (GC) 的早期准确诊断对于降低死亡率和改善患者健康至关重要。然而，GC的早期诊断方法仍然缺乏。在这项研究中，通过相对和绝对定量的同量异位标记 (iTRAQ)，我们鉴定了 336 个蛋白质，这些蛋白质在早期胃癌 (EGC) 与进展性胃癌 (PGC) 中上调的差异表达蛋白 (DEP) 之间重叠，在 EGC 中上调的差异表达蛋白 (DEP)与非胃癌 (NGC) 的比较，以及 EGC 与 NGC 中无显着性的蛋白质。这些 DEP 主要参与中性粒细胞相关的免疫反应。蛋白质和通路的网络分析表明，纤维蛋白原 α (FGA)、β (FGB) 和 γ (FGG) 是区分 EGC 的候选者。此外，对临床样本的平行反应监测（PRM）、免疫组织化学（IHC）和蛋白质印迹（WB）检测证实，与PGC和NGC相比，EGC胃粘膜中只有FGG独特且显着上调。我们的结果表明，胃粘膜中的 FGG 可以成为通过内窥镜检查诊断 EGC 患者的新型生物标志物。

Early and accurate diagnosis of gastric cancer (GC) is essential for reducing mortality and improving patient well-being. However, methods for the early diagnosis of GC are still lacking. In this study, by isobaric tagging for relative and absolute quantitation (iTRAQ), we identified 336 proteins that overlapped among the upregulated differentially expressed proteins (DEPs) in early gastric cancer (EGC) versus progressive gastric cancer (PGC), upregulated DEPs in EGC versus nongastric cancer (NGC), and nonsignificant proteins in EGC versus NGC. These DEPs were involved primarily in the neutrophil-related immune response. Network analysis of proteins and pathways revealed that fibrinogen α (FGA), β (FGB), and γ (FGG) are candidates for distinguishing EGC. Furthermore, parallel reaction monitoring (PRM), immunohistochemistry (IHC), and Western blot (WB) assays of clinical samples confirmed that, compared with that in PGC and NGC, only FGG was uniquely and significantly upregulated in the gastric mucosa of EGC. Our results demonstrated that FGG in the gastric mucosa could be a novel biomarker to diagnose EGC patients via endoscopy.