Prognostic significance of microRNA gene polymorphisms in patients with surgically resected colorectal cancer

MicroRNAs (miRNAs) are small 19- to 22-nucleotide sequences of RNA that participate in the regulation of cell differentiation, cell cycle progression and apoptosis. Although single-nucleotide polymorphisms (SNPs) in miRNA regions are considered unlikely to be functionally important, nucleotide variations within the sequences of primary (pri)- or precursor (pre)-miRNAs may affect miRNA processing and ultimately result in the modification of miRNA expression. The aim of this study was to investigate associations between four SNPs in pre-miRNA genes and the survival of colorectal cancer patients. A total of 407 colorectal patients were consecutively enrolled. DNA was extracted from blood specimens, and the hsa-mir-146aC>G, hsa-mir-149C>T, hsa-mir-196a2C>T and hsa-mir-499A>G polymorphisms were genotyped by PCR-RFLP. We were unable to identify independent prognostic SNPs for colorectal cancer. However, the heterozygous TC genotype of the 196a2C>T polymorphism was a significant risk factor for the overall survival of rectal cancer patients (HR=3.554, 95% CI 1.296-9.747, p=0.014). Further large-population studies are warranted to define the 196a2C>T polymorphism as a prognostic factor of rectal cancer.