Quantitative proteomic analysis of different stages of rat lingual carcinogenesis

Background: In India, oral squamous cell carcinoma (OSCC) is the single largest group of malignancies in males. Early diagnosis of cancer is difficult because of the lack of specific symptoms and/or biomarkers for early disease. Animal models provide an opportunity to study development and progression of cancers. Materials and Methods: In this study, we have explored the 4-nitroquinoline 1-oxide (4NQO)-induced tongue cancer model in Sprague Dawley rats. We compared the protein expression profiles of normal tissues with different stages of rat tongue cancer using isobaric tags for relative and absolute quantitation (iTRAQ)-liquid chromatography-tandem mass spectrometry (LC-MS/MS) based proteomics strategy. We validated some known and novel proteins by immunohistochemistry (IHC) and real-time polymerase chain reaction (PCR). Results: We observed hyperplasia, papillomas, and carcinomas after 120, 160, and 200 days treatment of 4NQO, respectively. LC-MS/MS analysis resulted in identification of 2223 proteins. Of these, 415 proteins were found to be differentially expressed in tumors, 333 proteins in papilloma and 109 proteins in hyperplasia. We have found alterations in several previously reported as well as novel proteins during rat tongue carcinogenesis. We validated known molecules such as vimentin, fascin, periostin, transglutaminase 3 by IHC and cornulin by real-time PCR on rat tissues. We also validated tenascin N, a novel protein by IHC on rat as well as in human tongue tissues. Conclusion: To the best of our knowledge, this is the first in-depth differential proteomics study carried out using an experimental rat model of OSCC. Proteomic alterations observed in this study provide insights into carcinogenesis process and may serve as a valuable resource for oral cancer biomarker discovery.