Background: Matrix metalloproteinase-9 (MMP-9) is an important mediator of tumor initiation and progression. The MMP-9 promoter -1562C/T functional polymorphism increases gene expression and was identified as a susceptibility factor for various cancers.
Objective: To evaluate the influence of the MMP-9 promoter genotype on the risk of developing papillary thyroid cancer (PTC) and to correlate cancer patient genotype with the clinical and pathological phenotype.
Methods: We evaluated 236 patients with nodular thyroid disease pre-thyroidectomy (119 benign disease, 117 PTC). Genomic DNA was isolated from whole blood and the MMP-9 -1562C/T genotype was evaluated by PCR-RFLP analysis.
Results: Genotype frequencies were in Hardy-Weinberg equilibrium for all groups. The T allele was significantly more frequent in cancer compared to benign disease (17.5% vs 10.1%), p= 0.019. Patients with the CT or CT+TT genotype had an increased risk of developing PTC, specifically micropapillary thyroid carcinoma (MPTC) (CT genotype: OR = 6.467, p= 0.00006; CT+TT: OR = 6.859, p= 0.00002), but not more advanced stages (CT: p= 0.094; CT+TT: p= 0.157). The -1562C/T genotype did not significantly correlate with tumor histological subtype, invasion or TNM stage.
Conclusion: The MMP-9 -1562C/T functional polymorphism may indicate susceptibility to develop thyroid cancer, specifically intrathyroidal clinically non-relevant MPTC. This suggests that although this genotype might be a predisposing factor, other genetic/epigenetic events are needed for cancer progression.
Keywords: MMP-9; Metalloproteinase-9; cancer susceptibility; polymorphism; thyroid cancer.