ESR1 and breast cancer: In addition to their endocrine disruptive properties, the THF-diols were purified and identified on the basis of their abilities to stimulate the proliferation of estrogen receptor (ER) positive (MCF-7) and ER-negative (MDA-MD-231) human breast cancer cells in vitro and to promote the growth of PC-3 human prostate cancer cell xenografts in athymic nude mice (Markaverich et al. 2002a).