NFKB1 and breast cancer: We and others have shown that NF-κβ factors are activated in mammary cancer: most main human breast and DMBA-induced rat mammary tumor tissues, breast cancer cell lines, and carcinogen-transformed human mammary epithelial cells contained significant levels of nuclear NF-κβ.46 Before the development of carcinogen-induced rat mammary tumors, NF-κβ up-regulation can occur.47