MAPK1 and breast cancer: To examine whether compensatory expression of ERK1 or ERK2 attenuated the inhibitory effects of miR-550a-3p on breast cancer cell viability and progression, pcDNA3-ERK1, pcDNA3-ERK2 or empty vector were co-transfected into MDA-MB-231 (Figure 7) and MCF-7 (Supplementary Figure S3) cells with the pre-miR-550a-3p or mNC.