Active Motif's T-47D nuclear extract was prepared from cell cultures of the human ductal breast epithelial tumor cell line. The T-47D cell line was derived from a pleural effusion of a 54-year old female patient with infiltrating ductal carcinoma. These cells exhibit a differentiated epithelial cell phenotype and express receptors to estradiol, as well as other steroids, and calcitonin. These cells also express mutant tumor suppressor p53 and are therefore commonly used in research as in vitro models of mutant p53 breast cancer cells to study breast cancer tumorigenicity and related drug therapies, such as tamoxifen.