Breast tumors often require hormones for growth, which poses a unique problem because the hormones involved in tumor growth are either estrogen, progesterone, or both. Estrogen and progesterone are naturally occurring and necessary hormones, produced mainly in the ovaries and adrenal glands in varying amounts throughout a woman's lifetime. These hormones are essential for many physiological functions, such as bone integrity. Hormone receptor-positive tumors can consist of cancer cells with receptor sites for estrogen, progesterone, or both. The hormones attach to receptor sites and promote cell proliferation. Hormone therapy blocks the hormones from attaching to the tumor receptor sites and may slow or stop the cancer's growth. The drug most often used in this type of endocrine therapy is tamoxifen, with a response rate from 30-60%. Other therapies are sometimes used, such as aromatase inhibitors (that inhibit the conversion of precursors to estrogens) or oophorectomy (the removal of the ovaries). The stronger form of estrogen, estradiol, can be converted into the weaker form, estriol, in the body without using drugs. Estriol is considered to be a more desirable form of estrogen. It is less active than estradiol, so when it occupies the estrogen receptor, it blocks estradiol's strong "growth" signals. Using a natural substance, the conversion of estradiol to estriol increased by 50% in 12 healthy people (Michnovicz et al. 1991). Furthermore, in female mice prone to developing breast cancer the natural substance reduced the incidence of cancer and the number of tumors significantly. The natural substance was indole-3-carbinol (I3C). Indole-3-carbinol (I3C) is a phytochemical isolated from cruciferous vegetables (broccoli, cauliflower, Brussels sprouts, turnips, kale, green cabbage, mustard seed, etc.). I3C given to 17 men and women for 2 months reduced the levels of strong estrogen, and increased the levels of weak estrogen. But more importantly, the level of an estrogen metabolite associated with breast and endometrial cancer, 16-a-hydroxyestrone, was reduced by I3C (Bradlow et al. 1991). |