The findings are reported in the June 25 issue of the Journal of Biological Chemistry. The pharmaceutical companies have made hundreds of drugs that resemble tamoxifen in their capacity to block estrogen binding to its receptor. However, testing all of these drugs in patients would involve considerable cost and time. Given the large number of women that are currently battling breast cancer, there is a great incentive to select drugs for clinical tests that are most likely to retain only the positive attributes of tamoxifen. Breast cancer afflicts one out of every eight women, and it is the most common form of cancer in women in the Western world.
Most breast cancers depend on estrogen for their growth.
Molecules on the surface of breast cancer cells, called estrogen receptors, bind to the hormone and respond to its growth-stimulating effects. Tamoxifen is also able to bind to these receptors, thereby blocking estrogen from binding and preventing the growth of new or recurring tumors. In a recent large scale study, tamoxifen also reduced the occurrence of breast cancer. Its ability to block tumor growth has proven so successful, that during this past year, it became the first drug approved by the Food and Drug Administration as a cancer preventative. Unfortunately, tamoxifen also has demonstrated a number of serious side effects.