Investigation of methylation and expression levels of thioredoxin interacting protein (TXNIP) gene in oral squamous cell carcinoma

Investigation of Expression and Methylation Levels of Thioredoxin Interacting Protein (TXNIP) Gene in Oral Squamous Cell Carcinoma Objecktive: In this study, methylation and expression levels of Thioredoxin Interacting Protein (TXNIP) gene, which was determined to show decrease in expression due to methylation by Prof. Dr. Semra Demokan et al. in their project's array results with TÜBİTAK-114S497 number, was studied in a wider group of patients with oral squamous cell carcinoma (OSCC). By developing an invasive/noninvasive method, we aim to define the usability of TXNIP as a biomarker for diagnosis / early diagnosis of oral squamous cell carcinoma Material and Method: In our study, tumor, normal and serum samples of 50 patients who were diagnosed and operated for OSCC in Istanbul Faculty of Medicine, Department of Otolaryngology & Head and Neck Surgery and normal mucosal tissue and serum samples of 10 healthy volunteers were collected. After isolation of DNA, ratio of methylation and expression of TXNIP gene and downregulation of expression ratio due to methylation were investigated. Quantitative Methylation Specific Polymerase Chain Reaction (QMSP) method was used to show methylation and Quantitative Real Time PCR (QRT-PCR) method was used to define the expression levels. Results: After the analysis, a decrease in TXNIP expression levels was found in 30 (60%) patients compared to normal tissue. While methylation in the promoter area was determined in 9 (18%) patients, only one normal tissue was found to have methylation. In 6 of 9 (67%) patients in whom methylation was observed, a decrease in expression levels was also observed. In 1 of 6 patients in whom decrease in expression due to methylation was found, methylation in normal tissue and serum samples was found. No methylation was found in healthy subjects. In OSCC patients with methylation, expression of the gene was found 89 times lower than the healthy population. In OSCC patients without methylation, expression of the gene was found 35 times lower than the healthy population. Conclusion: For the TXNIP gene that shows no methylation in healthy population, after studies with higher volumes of OSCC patients, it is possible to use this gene as a biomarker for OSCC diagnosis/early diagnosis and follow-up. Key words: oral squamous cell carcinoma, methylation, expression , TXNIP, epigenetic