Our study investigates the role of ET-induced inflammatory insult in breast cancer initiation events using nontumorigenic (SCp2 and S1) rodent mammary and human breast epithelial cells, respectively, and whether such an insult can “add injury” to pretumorigenic (Cx43-KO S1) or tumorigenic breast cells (MCF-7 and MDA-MB-231). Here, GJA1 is linked to breast carcinoma.