Breast Stem Cells - A toxicological model for endocrine disruptors, such as soy isoflavones

German. The adult mammary gland requires stem cells, or a stem cell-like activity, to fulfil the massive expansion in epithelial tissue during pregnancy and breast feeding and to replace cells that are lost through routine tissue renewal. Recently a human breast epithelial cell type (Type 1 HBEC) with stem cell characteristics has been isolated. The SV40 (simian virus) immortalized Type 1 HBEC cell line (M13SV1) was non-tumorigenic (Kao et al .). Two tumorigenic cell lines were developed from M13SV1 after X-ray irradiation (M13SV1 R2) and an additional transfection with a mutated ERBB2 oncogene (M13SV1 R2-N1), resulting in high and low tumorigenicity respectively, showing a change in tumorigenicity and estrogen response after growth in minimal media (Wang et al .).Isolated isoflavones are currently components of dietary supplements to treat postmenopausal symptoms of women. However, the epidemiological data to the effect of isoflavone intake on breast cancer is contradictory. According to the stem cell theory of carcinogenesis, breast stem cells are the ideal target for the proposed research. Therefore, we want to develop a toxicological model using these human breast stem cell lines to test the effect of endocrine disruptors, such as soy isoflavones in a human relevant model.In the present study we analyzed the effect of the phytoestrogen genistein, the most intensively studied soy protein, on the differentiation of M13SV1 cells. The expression of different luminal epithelial cell markers (i.e. epithelial membrane antigen and keratin 18), estrogen receptors and stem cell markers was measured on the mRNA level by quantitative real time PCR. The analysis of several of these markers was also performed on the protein level using western blot.We want to use this panel of different markers to establish a toxicological model that can be used in the future to analyze a wide panel of different endocrine disruptors.