Subsequently, ET was used at 0.1 μg/ml for the treatment of normal mouse mammary epithelial SCp2 cells, at 10 μg/ml for nontumorigenic human mammary epithelial S1 cells and their pretumorigenic counterparts, Cx43-KO S1 cells [21], and at 1 μg/ml for the tumorigenic cell lines including human breast cancer cells of intermediate (MCF-7) and high invasiveness (MDA-MB-231). The gene discussed is GJA1; the disease is breast cancer.