Effects of Tamoxifen and Soy Isoflavones on Mammary Tumor Development Induced by the neu Proto-oncogene Co-investigators: Shaikh, Firdosbanu, Ho, Arline; Hughes, Claude L., Duke University; Cline, J. Mark, Wake Forest University School of Medicine. Abstract #: F-08 The effects of tamoxifen and soy isoflavones on breast cancer were investigated in a mouse model that expresses the cancer gene, neu (also called c-erbB2 or HER2). This model is highly relevant to human breast cancer due to the high levels of neu, the most common oncogene in breast cancer, and to the spontaneous development of cancer in the mammary gland (analogous to the breast in women) that often spreads to the lungs. Tamoxifen has been shown in clinical studies to effectively prevent breast cancer in women. For isoflavones, there is evidence of both diminished and augmented growth of breast tumors, leaving questions regarding its effects on breast cancer unresolved. In this study, adult neu female mice were treated with tamoxifen (equivalent to 20 mg/day dose for women) and soy containing isoflavones (>300 mg/day for women). The dose of isoflavones in this study is higher than generally recommended for post-menopausal women (100 mg/day or less). The effects on tumor development for the treatment groups were compared to a control group that was not treated. Onset of tumor development was measured by when the tumors were first found by palpation. The number of females that developed tumors was also recorded for each group. Isoflavones did not reduce or delay the development mammary tumors in these mice. In contrast, tamoxifen was very effective at preventing tumor development. However, for the tumors that did grow in the tamoxifen group, they began at younger ages. Tumor development is still being assessed in the remaining females in this study. Also under investigation is whether the treatments influence the tumor to become more aggressive, resulting in the spread to other organs (the lungs in this model). The current data demonstrate that the neu model is a very sensitive to influences by estrogens and antiestrogens, such as tamoxifen, as is seen with human breast cancer, making it an excellent model for investigating the role of estrogens in tumor development. Remember we are NOT Doctors and have NO medical training. This site is like an Encylopedia - there are many pages, many links on many topics. Support our work with any size DONATION - see left side of any page - for how to donate. You can help raise awareness of CAM.