The areca nut is a known carcinogen that causes oral cancer in individuals in Southeast Asia, but the molecular mechanism that leads to this malignancy is still unclear. To mimic the habit of areca nut chewing, our laboratory has established four oral cancer cell sublines (SAS, OECM1, K2, C9), which have been chronically exposed to areca nut extract (ANE). To elucidate the molecular basis of areca nut-induced oral carcinogenesis, the differential proteomes between oral cancer cells and the ANE-treated sublines were determined using isobaric mass tag (iTRAQ) labeling and multidimensional liquid chromatography-mass spectrometry (LC-MS/MS). Over 1000 proteins were identified in four sublines, and 196 proteins were found to be differentially expressed in at least two ANE-treated sublines. A bioinformatic analysis revealed that these proteins participate in several pathways, and one of the most prominent pathways was the regulation of epithelial to mesenchymal transition (EMT). In all, 24 proteins including Krt17 were confirmed to be differentially expressed in the ANE-treated sublines. To reveal additional information on the mechanism of ANE-induced carcinogenesis, Krt17 was further investigated. Krt17 knockdown significantly suppressed ANE-induced cell migration and invasion and modulated the EMT process. Furthermore, in a murine model of carcinogen-induced (arecoline cocktail, an active compound of ANE) oral cancer, Krt17 was significantly up-regulated in all hyperplastic tissues and in carcinoma tissues (p < 0.001). In conclusion, we have identified a proteome of oral cancer cells that is associated with chronic areca nut exposure. Krt17 was demonstrated to contribute to areca nut-induced oral malignancy. The results of this study contribute to risk assessment, disease prevention and other clinical applications associated with areca nut-induced oral cancer.
Keywords: Krt17; areca nut; epithelial to mesenchymal transition; iTRAQ; oral carcinogenesis.