Since we have recently shown that the TNF-α-induced cell fusion process between M13SV1-Cre breast epithelial cells and human MDA-MB-435-pFDR1 breast cancer cells is abolished by minocycline [13], we wondered how minocycline might affect TNF-α-induced signal transduction pathways in detail and which of them are relevant in promoting the cell fusion step. Here, TNF is linked to breast carcinoma.