The rs9383935 risk allele A showed decreased activity of reporter gene in both the MCF-7 and BT-474 breast cancer cell lines, which might be due to an altered binding capacity of miR-27a to the 3' untranslated region (3' UTR) sequence of CCDC170. Real-time quantitative reverse transcription PCR confirmed the correlation between rs9383935 genotypes and CCDC170 expression levels. This evidence concerns the gene CCDC170 and breast cancer.