MicroRNAs (miRNAs) are an abundant class of small nonprotein-coding RNAs with posttranscriptional regulatory functions as tumour suppressors and oncogenes. Aberrant expression and structural alteration of miRNAs are thought to participate in tumourigenesis and cancer development. It has been suggested that the presence of single-nucleotide polymorphisms in precursor miRNAs (pre-miRNAs) can alter miRNA processing, expression, and/or binding to target mRNA and represent another type of genetic variability that can contribute to the development of human cancers. Recent studies have indicated that the miR-196a-2 rs11614913 (C→T) polymorphism could alter mature miR-196a-2 expression and target mRNA binding. To determine the association of the miR-196a-2 rs11614913 polymorphism with the risk of hepatocellular carcinoma (HCC) development in a Turkish population, a hospital-based case-control study was designed consisting of 185 subjects with HCC and 185 cancer-free control subjects matched for age, gender, smoking and alcohol status. The genotype frequency of the miR-196a-2 rs11614913 polymorphism was determined by using a polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) assay. Our data shows that the CC genotype of the miR-196a-2 rs11614913 polymorphism is associated with increased risk of HCC development in this Turkish population (OR = 2.41, 95% CI: 1.30-4.50, P = 0.005). Furthermore, according to stratified analysis, a significant association was observed between the homozygote CC genotype and HCC risk in the subgroups of male gender (OR = 3.12, 95% CI: 1.53-6.34, P = 0.002) and patients with hepatitis B virus (HBV)-related HCC (OR = 2.88, 95% CI: 1.33-6.22, P = 0.007). Because our results suggest for the first time that the miR-196a-2 rs11614913 polymorphism may be a genetic susceptibility factor for HCC (especially in the male gender and HBV-infected patients) in the Turkish population, further independent studies are required to validate our findings in a larger series, as well as in patients of different ethnic origins.

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Our results suggest that the CCND1 G870A single nucleotide polymorphism is associated with an increased risk of HCC in our Turkish population.

Exonuclease 1 (Exo 1) is an important nuclease involved in mismatch repair system that contributes to maintain genomic stability, to modulate DNA recombination, and to mediate cell cycle arrest. A guanine (G)/adenine (A) common single nucleotide polymorphism at first position of codon 589 in Exo 1 gene determines a glutamic acid (Glu, E) to lysine (Lys, K) (K589E) aminoacidic substitution which may alter cancer risk by influencing the activity of Exo 1 protein. Exo 1 K589E polymorphism has been studied in various cancers, but its association with hepatocellular carcinoma (HCC) has yet to be investigated. To determine the association of the Exo 1 K589E polymorphism with the risk of HCC development in a Turkish population, a hospital-based case-control study was designed consisting of 224 subjects with HCC and 224 cancer-free control subjects matched for age, gender, smoking and alcohol status. The genotype frequency of the Exo 1 K589E polymorphism was determined by using a polymerase chain reaction-restriction fragment length polymorphism assay. Our data shows that the Lys/Lys genotype of the Exo 1 K589E polymorphism is associated with increased risk of HCC development in this Turkish population [odds ratio (OR) = 2.15, 95% confidence interval (CI): 1.13-4.09, P = 0.02]. Furthermore, according to stratified analysis, a significant association was observed between the homozygote Lys/Lys genotype and HCC risk in the subgroups of male gender (OR = 2.67, 95% CI: 1.27-5.61, P = 0.009) and patients with non-viral-related HCC (OR = 3.14, 95% CI: 1.09-8.99, P = 0.03). Because our results suggest for the first time that the Lys/Lys homozygote genotype of Exo 1 K589E polymorphism may be a genetic susceptibility factor for HCC in the Turkish population, further independent studies are required to validate our findings in a larger series, as well as in patients of different ethnic origins.

Cyclooxygenase-2 (COX-2) influences carcinogenesis through immune response suppression, apoptosis inhibition, regulation of angiogenesis and tumor cell invasion, and metastasis. It is now well established that COX-2 is overexpressed in many premalignant, malignant, and metastatic cancers, including hepatocellular carcinoma (HCC). DNA sequence variations in the COX-2 gene may lead to altered COX-2 production and/or activity, and so they cause inter-individual differences in the susceptibility to HCC. Functional coding region polymorphisms -1195A>G (rs689466), -765G>C (rs20417), and +8473T>C (rs5275) in the COX-2 gene have recently been shown to be associated with several human cancers but their association with HCC has yet to be investigated. We used hospital-based case-control study to assess the hypothesis that the functional COX-2 variation may affect individual susceptibility to the HCC. COX-2 polymorphisms were investigated in 129 confirmed subjects with HCC and 129 cancer-free control subjects matched on age, gender, smoking, and alcohol consumption using a polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) assay. The distribution of the COX-2 -1195A>G and +8473T>C genotypes were not significantly different between HCC cases and control. However, proportion of the COX-2 -765CC genotype which leads to a 30% reduction of the COX-2 promoter activity was significantly lower in patients with HCC (3.1%) when compared to control subjects (11.6%) (P < 0.05). Logistic regression analyses revealed that the COX-2 -765G>C variant genotype (-765CC) was associated with a significantly decreased risk of HCC compared with the -765GG wild-type homozygotes [P < 0.05, odds ratio (OR) = 0.25, 95% confidence interval (CI) = 0.08-0.79]. Our results suggest for the first time that the -765CC genotype of COX-2 -765G>C polymorphism, causing lower COX-2 gen expression, is a genetic protective factor for HCC. However, because this is the first report concerning the COX-2 -1195A>G, -765G>C, and +8473T>C polymorphisms and the risk of HCC, independent studies are needed to validate our findings.