Investigation of Methylation-Related Expression Changes of GABRB3 Gene in Oral Malignant Lesions

Aim: Oral cancer constitutes 2-4% of all cancers and is the most common cancer in the head and neck region after laryngeal cancer. Oral squamous cell carcinoma (OSCC) constitutes more than 90% of all oral cavity carcinomas. While the 5-year survival rate in OSCC is 40%, this rate increases to 95% in early diagnosis. The GABRB3 gene was identified as a potential epigenetic biomarker candidate in the TUBITAK-SBAG-114S497 project conducted by Demokan et al., and in this study, the differing methylation and expression levels in OSCC patients were examined and its biomarker potential in early diagnosis and prognosis was investigated. Methods: DNA and RNA were isolated from tissue samples taken from 15 patients diagnosed with OSCC, then the methylation status and gene expression levels of the GABRB3 gene were evaluated by Quantitative Methylation Specific PCR and Real-Time PCR methods, respectively. Results and Conclusions: Methylation was detected in the promoter region of the GABRB3 gene in 60% of tumor samples from OSCC patients. When expression levels were evaluated, loss of expression of the GABRB3 gene was detected in 46.7% of samples compared to normal tissues in tumor tissues, while increased expression was observed as 13.3%. Methylation was detected in all patients with decreased expression levels. While decreased expression was observed in 33.3% of tumor tissues having no methylation, increased expression was observed in 50%. It is thought that GABRB3 gene may be responsible for a special subgroup of OSCC patients via methylation-related loss of expression and can be used as a potential biomarker candidate in early diagnosis and prognosis determination. Further studies in larger patient groups are needed to confirm these findings.