Differential response to phytoestrogens in endocrine sensitive and resistant breast cancer cellsin vitro

Women approaching menopause increasingly investigate alternatives to hormone replacement therapy. Plant phytoestrogens are being promoted as "natural" alternatives but there is a lack of substantive data to advocate their safe use in breast cancer patients receiving tamoxifen (TAM), or in those who have relapsed. The aim of our study was to investigate the proliferative effects and mode of action of the phytoestrogens genistein, daidzein and coumestrol on TAM-sensitive (-s) and resistant (-r) breast cancer cells under in vitro conditions designed to mimic the hormonal environment of the pre- and post-menopausal breast. At physiological concentrations (<10 microM) and under reduced estrogen (E2) conditions, genistein was mitogenic to TAM-s cells with TAM-r cells generally refractory. Daidzein and coumestrol were growth stimulatory irrespective of TAM sensitivity. Transcriptional activity was ERE-mediated. Combining phytoestrogens with E2 (simulating the pre-menopausal breast environment) had no effect on growth of TAM-s or TAM-r cells. Addition of 4-HT mimicked the hormonal environment in post-menopausal breast cancer patients receiving TAM. The growth inhibitory effects of 4-HT were abrogated in TAM-s cells when combined with genistein and coumestrol, and to a lesser extent, daidzein, where significant growth stimulatory effects were observed. In TAM-r cells, proliferation did not exceed control values. At phytoestrogen concentrations above 10 microM, growth inhibitory effects were seen, irrespective of estrogenic environment or cell sensitivity to TAM. Our in vitro data suggests that phytoestrogens could have potentially adverse mitogenic effects on tumour cells and should probably be avoided by patients who remain sensitive to TAM or in those with pre-existing and possibly undiagnosed breast tumours.

Phyto-oestrogens and breast cancer chemoprevention

Phytoestrogens are polyphenol compounds of plant origin that exhibit a structural similarity to the mammalian steroid hormone 17β-oestradiol. In Asian nations the staple consumption of phyto-oestrogen-rich foodstuffs correlates with a reduced incidence of breast cancer. Human dietary intervention trials have noted a direct relationship between phyto-oestrogen ingestion and a favourable hormonal profile associated with decreased breast cancer risk. However, these studies failed to ascertain the precise effect of dietary phyto-oestrogens on the proliferation of mammary tissue. Epidemiological and rodent studies crucially suggest that breast cancer chemoprevention by dietary phyto-oestrogen compounds is dependent on ingestion before puberty, when the mammary gland is relatively immature. Phyto-oestrogen supplements are commercially marketed for use by postmenopausal women as natural and safe alternatives to hormone replacement therapy. Of current concern is the effect of phyto-oestrogen compounds on the growth of pre-existing breast tumours. Data are contradictory, with cell culture studies reporting both the oestrogenic stimulation of oestrogen receptor-positive breast cancer cell lines and the antagonism of tamoxifen activity at physiological phyto-oestrogen concentrations. Conversely, phyto-oestrogen ingestion by rodents is associated with the development of less aggressive breast tumours with reduced metastatic potential. Despite the present ambiguity, current data do suggest a potential benefit from use of phyto-oestrogens in breast cancer chemoprevention and therapy. These aspects are discussed.

8th Nottingham International Breast Cancer Conference, Nottingham, UK, 16-19 September 2003

The four-day biennial 8th Nottingham Breast Cancer Conference held at the East Midlands Conference Centre, University of Nottingham, UK (16-19 September 2003) once again proved to be a successful event. Recent advances in clinical and scientific research were presented to an international audience, covering a broad spectrum of breast cancer issues including prediction, diagnosis and treatment. Delegates were encouraged to participate in workshop sessions, which allowed the comprehensive discussion of existing and promising future advances in breast cancer care.

Evaluation of seven oestrogen receptor beta antibodies for immunohistochemistry, western blotting, and flow cytometry in human breast tissue

Two oestrogen receptors, ER alpha and ER beta, exist. While much is known about ER alpha, the role of ER beta is still undefined, especially at the protein level. The aim of this study was to determine the utility of seven ER beta antibodies (14C8, 8D5, PAI313, PPG5/10, N19, 9.88, and D7N) raised against different domains of ER beta in three commonly used laboratory applications, namely immunohistochemistry, western blot, and flow cytometry, using human breast material. For immunohistochemical analysis of frozen material, PAI313 and D7N gave stronger and more specific signals than 14C8, 8D5, and PPG5/10. In paraffin sections, 14C8, closely followed by PPG5/10, gave by far the most superior nuclear immunoreactivity, compared with the other antibodies tested. In general, flow cytometry results mirrored the immunohistochemistry data for paraffin sections, with antibodies ranked 14C8 > 8D5> or = PAI-313 > PPG5/10 >D7N. For western blotting, 8D5 and D7N yielded the strongest and most consistent bands, with weaker bands seen with the others. It is concluded that ER beta protein can be detected using specific antibodies. However, there is considerable variation between the specificity and application of these antibodies, highlighting the fact that careful optimization is required when selecting an antibody for use in a particular laboratory technique.