Our previous classification of SERMs in these two cell lines was based on one single marker of E2-responsiveness in these breast cancer cells: E2 and 4OHT produced oestrogenic effects on the activation of TGFα mRNA in cell expressing wtERα whereas Ral and ICI were anti-oestrogens (Levenson et al, 1998b). This evidence concerns the gene RALA and breast cancer.