Thus, the present study explored the association between five common functional polymorphisms in miRNAs (i.e., miRNA-196a2C>T, rs11614913; miRNA-146aG>C, rs2910164; miRNA-423C>A, rs6505162; miRNA-608G>C, rs4919510; miRNA-27aC>T, rs895819) and the risk of BC.
Significantly higher levels of miR-140-5p, miR-194 and miR-423-5p (the last of which harbours the single-nucleotide polymorphism rs6505162) were seen in the breast tumours of Nigerian patients when compared with other ethnic groups (all p < 0.0001). miR-101 was overexpressed in breast cancers in the Indian patients.
Our findings support the following conclusions: a) rs6505162:C > A in pre-miR-423 increases risk of familial BC in families with a strong history of BC; b) the C/A genotype at rs2682818:C > A (pre-miR-618) increases BC risk in non-familial early-onset BC; and c) the G/G genotype at rs895819:A > G (miR-27a) reduces BC risk in families with a moderate history of BC.
In this study, we determined the genotypes of SNP rs6505162 in 5 matched cell lines (breast cancer cell lines and their corresponding peripheral blood cell lines) and 114 matched clinical specimens (clinical breast carcinoma specimens and their corresponding normal tissues), compared the processing efficiency of pri-miRNA to mature forms between pre-miR-423-12C (wild-type) and pre-miR-423-12A (mutant-type) expression vectors, and evaluated the function of miR-423 on cell proliferation.
However, for the miR-146a rs2910164 (G>C), miR-149 rs2292832 (G>T), miR-373 rs12983273 (C>T), and miR-423 rs6505162 (C>A) polymorphisms, we failed to find any significant association with the risk of breast cancer in any genetic model.
Caucasian Australian women with breast cancer and controls matched for age and ethnicity were genotyped for rs6505162 and their genotypic and allelic frequencies analysed for significant differences.