Abstract
AIM: To detect proteomic differences in tears between adenoid cystic carcinoma (ACC) and pleomorphic adenoma (PA). METHODS: Tear samples were collected from 4 patients with ACC, 5 with PA, and 4 control cases. Label-free analysis and parallel reaction monitoring (PRM) were used to screen and validate the tear proteome. Gene Ontology (GO) annotation and Kyoto Encyclopedia of Genes and Genomes (KEGG) were conducted for bioinformatics analysis. RESULTS: In total, 1059 proteins in tear samples were identified by label-free analysis. Between ACC and PA, 415 differentially expressed proteins were detected. Based on the GO annotation, enzyme regulator activity and serine-type endopeptidase inhibitor activity in the molecular function category, blood microparticle and extracellular matrix in the cellular component category, and response to nutrient levels in the biological process category were most predominant. By KEGG pathway annotation, the different proteins between ACC and PA mainly participated in complement and coagulation cascades, amoebiasis, African trypanosomiasis and cholesterol metabolism. Eight proteins with mostly significant differences were verified by PRM, and five proteins with more than 10-fold increases in ACC compared with PA, including integrin β, α-2-macroglobulin, epididymal secretory sperm binding protein Li 78p, RAB5C, and complement C5, were identified. CONCLUSION: The combined tools of label-free analysis and PRM are very effective and efficient, especially for samples such as tears. Some proteomic differences in tears between ACC and PA are identified and these protein candidates may be specific biomarkers for future exploration.