Tiroid nodüllerinin değerlendirilmesinde DNA onarım proteinlerinin yeri

The role of DNA repair proteins in the assessment of thyroid nodules Aims: Bening and malignant thyroid nodules are the most common lesions of endocrine glands. However the differantiation between these lesions even histopathologically are sometimes difficult. Recently some molecular markers; Mut-SHomolog- 2 (MSH2) and Mut-L-Homolog-1 (MLH1) are the two of DNA repair proteins [?Mismatch Repair? (MMR) proteins], and metil guanin?DNA-metil transferase (MGMT) is one of the DNA repair enzymes have been studied for the purpose. Herein this study we aimed to evaluate MSH2, MLH1 and MGMT levels in papillary thyroid cancer (PTC), multinodular colloidal goitre (MNG) and chronic lymphocytic thyroiditis (CLT) cells, and define if could be used as new markers for diagnosis. Methods: Ninety patients? tissue specimens obtained from total or subtotal thyroidectomy materials with PTC (n=29; 50.07 ±16.42 yrs), MNG (n= 26; 52.96 ±17.09 yrs) and CLT (n=29; 46.21±11.80 yrs) were evaluated. The specimens were studied for MGMT, MSH2, MLH1 immunohistochemically. Descriptive analysis, ANOVA test and Pearson?s chi squared test were used for statistical analysis. Results: Despite all MGMT, MLH1 and MSH2 were similar for follicular cell expression statistically, the staining was noticible in PTC group. The expressions for MGMT and MSH2 were similar for staining density and immunoreactivity within groups, but the expressions were more pronounced in PTC cells with nuclear and sitoplasmic staining. Whereas MNG cells were expressing nuclear staining. The groups were reevaluated for MSH2 follicular cell expression as less than 50% and equal and greater than 50%. In this model CLT and MNG groups were different (p=0.023) and the difference was significant for staining density and immunreactivity as well (p=0,001 and p=0,044 respectively). Follicular cell expression between PTC and MNG (p=0.032), and immunoreactivity between CLT and MNG (p=0,012) were different for MLH1. Results: DNA repairment so the expression of its biomarkers is more pronounced in malignant lesions. This increament is based on the functional activation IV of repairing genes in response to DNA damage. Here in this study despite showing no statistical significancy we found an increased expression of the three biomarkers ? MGMT, MLH1 and MSH2- in PTC cells especially compared to MNG cells, with a marked similarity to CLT. The big dilemma to differentiate chronic thyroiditis and papillary cancer insists on with these molecules, but further studies may compromise for the use of these new biologic markers especially for differentiating benign and malignant lesions. Key Words: Thyroid, Papillary Thyroid Cancer, Chronic Lymphocytic Thyroiditis, Colloidal Goitre, DNA, MGMT, MMR, MSH2, MLH1.