CCDC170 and breast cancer: Subsequently, we transfected miR-27a-3p into MCF-7 breast cancer cells and validated its regulation of the endogenous CCDC170. The qRT-PCR assay showed that miR-27a-2p significantly decreased CCDC170 mRNA level compared with the negative controls (P = 0.016, Figure 2A); however, we did not find significant changes in ESR1 expression after miR-27a-3p transcription (P = 0.361) (Figure 2B).