ITRAQ and PRM-based quantitative saliva proteomics in gastric cancer: biomarker discovery
Abstract
Gastric cancer (GC) remains one of the leading causes of cancer-related mortality worldwide, and early detection is critical for improving patient prognosis.
Traditional diagnostic methods, such as serum biopsy, endoscopy and CT scans, are invasive, costly, and often uncomfortable for patients. In addition, these traditional markers show limited sensitivity and specificity for early-stage GC, especially in asymptomatic patients. Therefore, this study was conducted to investigate salivary biomarkers for early GC detection using iTRAQ-based and PRM-based proteomics techniques to identify differentially expressed proteins in GC patients.
We utilized iTRAQ technology to quantitatively analyze salivary proteins from two gastric cancer groups (GC group 1 and GC group 2) and healthy controls. Differential expression of proteins between these groups was assessed, and functional annotation was performed using Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analyses. Protein-protein interaction (PPI) networks were constructed to investigate potential molecular interactions. Validation of saliva-specific biomarkers for GC was performed using PRM. Kaplan–Meier (KM) survival analysis were employed to evaluate the clinical relevance of the identified proteins.
In the screening cohort, 671 proteins with unique peptide segments were identified through iTRAQ analysis. Among them, 124 proteins were significantly differentially expressed in GC group 1, and 102 proteins were differentially expressed in GC group 2 compared to healthy controls. A total of 56 overlapping DEPs were identified between the two GC groups, with 24 proteins upregulated and 32 proteins downregulated. GO analysis revealed that these DEPs were involved in
several biological processes including nucleosome, DNA packaging complex. KEGG analysis indicated these proteins involved in several pathways including transcriptional misregulation in cancer, alcoholism, shigellosis, IL-17 signaling pathway. In the validation cohort, we found consistent expression patterns for four proteins: S100A8, S100A9, CST4, and CST5. Results show that the levels of S100A8, S100A9 were upregulated and CST4, and CST5 downregulated in the saliva. The Kaplan-Meier (KM) survival analysis indicated that elevated CST5 and CST4 expression levels were associated with faster disease progression while high expression of S100A8 and S100A9 correlated with poor progress. Overall, S100A8, S100A9, CST4, and CST5 emerged as cancer-specific saliva biomarkers for early detection and diagnosis of GC, providing a scientific basis for clinical application.
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