Objectives: The aim of this study was to identify potential salivary biomarkers for early diagnosis of oral cancer patients by using the shotgun proteomics technique.
Methods: Saliva was collected by Navazesh’s method and immediately placed on ice. Saliva was centrifuged at 14,000 rpm for 10 minutes at 4°C. The supernatant was collected, added with protease inhibitor, and then kept at -80°C until analysis. Whole salivary proteins of six oral cancer patients and six healthy controls were profiled using shotgun proteomics based on protein digestion and peptide sequencing by tandem mass spectrometry and automated database searching.
Results: Shotgun proteomics pattern showed different protein patterns among normal and oral cancer patients. Thus, many proteins associated with cell division and cell cycle namely centrin 2, E3 ubiquitin-protein ligase HERC2, microtubule-associated protein tau isoform 3, pregnane X nuclear receptor, prothymosin alpha were found to be upregulated in saliva from oral cancer patients. These proteins were reported in other studies to be upregulated in breast cancer patients. In addition, microphthalmia-associated transcription factor A and Poly(Adp-Ribose) Polymerase 15 were upregulated in our studies: the former protein was previously reported to be upregulated in renal cell carcinoma and melanoma, while the latter protein was reported to be upregulated in ovarian cancer. Moreover transformation/transcription domain-associated protein, isoform CRA_e, associated with tumor suppressor p53, was also found to be upregulated.
Conclusions: Shotgun proteomics may useful as a tool for identification of some proteins from the saliva of oral cancer patients.
This project is supported by the Office of the Higher Education Commission and Mahidol University under the National Research Universities Initiative.