Our results verified these notions: (1) overexpressing Cx43 in a non-aggressive breast cancer cell line MCF-7 enhanced the cell migration activity; (2) Additional treatment of miR-200a could fully prevent Cx43-induced cell migration activity in MCF-7 cell; (3) Treatment of miR-200a or miR-1, both of which were direct suppressors of Cx43, could attenuate the migration activity of an aggressive breast cancer cell line MDA-MB-231. This evidence concerns the gene GJA1 and breast carcinoma.