ABSTRACT
Papillary thyroid carcinoma (PTC), a common form of thyroid malignancy, displays significant variations in clinical features and outcome. The malignant transformation of the thyroid is driven by altered expression of many matrix-modulating enzymes, including matrix metalloproteinase-9 (MMP-9). A single nucleotide polymorphism in its promotor (-1562 C/T) is suspected to cause overexpression of MMP-9, which in turn contributes to development of a tumour unfavourable phenotype. The aim of this study was to investigate the impact of MMP-9 promotor genotype on MMP-9 expression in PTC samples, and to assess its value as a possible risk factor for developing PTC or its aggressive phenotype. A total of 105 PTC patients and 43 healthy controls were genotyped by the polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) method. In order to estimate MMP-9 expression, PTC tissue sections were stained immunohistochemically. Statistical analysis showed that PTC cases and controls did not differ significantly in genotype frequencies (OR = 2.27, CI = 0.854-6.022). In PTC samples, the presence of the T allele was accompanied by elevated MMP-9 expression (p = 0.047) as well as a higher risk of developing extrathyroid extensions (p = 0.037) and high TNM stages (p = 0.009). Moreover, we observed overexpression of MMP-9 in cases presenting with extrathyroid invasion (p = 0.001), lymph node metastasis (p = 0.028), large tumour size (p = 0.031) and advanced stage (p = 0.005) compared to indolent tumours, along with enhanced enzymatic activity demonstrated by in situ zymography. Data suggests that MMP-9 (-1562 C/T) does not facilitate predisposition for PTC but affects the disease course by modulating MMP-9 expression. Genotyping MMP-9 provides important information which may prove beneficial in risk stratification of PTC patients.