Background microRNAs (miRNAs) are potentially involved in many physiopathological processes, including regulation of cell growth, differentiation, apoptosis and cancer. Single nucleotide polymorphisms of the genes encoding miRNAs can alter their expression and may influence cancer risks. This case-control study explored the relationship between three microRNA polymorphisms (miR-27a, miR-196a2 and miR -146a) and breast cancer (BC). Methods A total of 353 breast cancer cases and 353 controls were genotyped for miR-27a (rs895819), miR-196a2 (rs11614913) and miR -146a (rs2910164). The miR-27a and miR-146a variants were discriminated using a PCR-restriction fragment length polymorphism method, while miR-196a2 were analysed by tetra-primers amplification refractory mutation system PCR. Odds ratios (ORs) and 95% confidence intervals (95% CIs) were used to estimate associations. Results The CC homozygous genotype of miR-146a (rs2910164) was seen in 45(12.7%) patients with breast cancer and 18(5.1%) controls (OR 4.09 [95%CI 2.19-7.67] p < 0.001). The minor allele G of miR-27a was associated with a decreased risk of breast cancer (OR 0.24 [95% CI 0.14-0.42] p < 0.001). The miR-196a2 (rs11614913) was not related to breast cancer (p > 0.05). Conclusion Our data indicate that miR-146a (rs2910164) and miR-27a (rs895819) variants contribute to breast cancer. Further studies in larger populations including other genetic and environmental factors are required to achieve a definitive conclusion.

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The MMP-3 [rs632478] polymorphism may contribute to susceptibility to disc degeneration. To confirm our findings, additional well-designed studies in diverse ethnic populations are required.

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