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[Polymorphisms of microRNA genes and their association with breast cancer risk].

OBJECTIVE
To explore the relationship between the polymorphisms of microRNA genes and the risk of breast cancer, and to analyze molecular markers which can be used in screening of susceptible population.


METHODS
All the individuals included in this case-control study were genetically independent ethnic Han Chinese. The breast cancer patient group consisted of 384 women confirmed by histopathology, and the control group consisted of 192 healthy female individuals. We screened genetic variants in all miRNA genes according to the public database miRBase and NCBI database. A total of twenty-three common single nucleotide polymorphisms in twenty-two miRNAs, which tagged the known common variants with minor allele frequency greater than 0.05 were genotyped. A MassARRAY ® MALDI-TOF system was used for genotyping the candidate SNPs by the method described in the Sequenom Genotyping Protocol. The frequencies of SNPs were compared between cancer cases and controls to identify the SNPs associated with breast cancer susceptibility. Logistic regression analysis was applied to analyze the differences in genotype or allele frequencies of individual SNPs in cancer cases and controls, and to evaluate the correlation between candidate loci and breast cancer risk.


RESULTS
The median age of the total group including 384 breast cancer patients and 192 control subjects was 48 years (range, 21-81 years). There were no significant differences in age distribution (P = 0.695) and smoking status (P = 0.193) between the case group and the control group. However, the number of patients with a family history of breast cancer or ovarian cancer in the case group was significantly higher than that in the control group (9.1% vs.1.6%, P < 0.001). The number of the patients with menarche age below 14 years in the case group was significantly higher than that in the control group (53.1% vs.37.5%, P < 0.001). The number of premenopausal patients in the case group was significantly higher than that in the control group (61.2% vs. 50.0%, P = 0.007). There was no significant association between breast cancer risk and the single nucleotide polymorphisms in miRNA genes (P > 0.05).


CONCLUSIONS
The genetic polymorphism of miRNA is not obviously associated with breast cancer risk among Chinese women.