During the past 20 years our understanding of the control of
breast tumor development, growth and survival has changed dramatically. The once long forgotten application of high dose
synthetic estrogen therapy as the first chemical
therapy to treat any
cancer has been resurrected, refined and reinvented as the new biology of
estrogen-induced apoptosis. High dose
estrogen therapy was cast aside once
tamoxifen, from its origins as a failed "
morning after pill", was reinvented as the first targeted
therapy to treat any
cancer. The current understanding of the mechanism of
estrogen-induced apoptosis is described as a consequence of acquired resistance to long term antihormone
therapy in
estrogen receptor (ER) positive
breast cancer. The ER signal transduction pathway remains a target for
therapy in
breast cancer despite "
antiestrogen" resistance, but becomes a regulator of resistance. Multiple mechanisms of resistance come into play: Selective ER modulator (
SERM) stimulated growth,
growth factor/ER crosstalk,
estrogen-induced apoptosis and mutations of ER. But it is with the science of
estrogen-induced apoptosis that the next innovation in women's health will be developed. Recent evidence suggests that the
glucocorticoid properties of
medroxyprogesterone acetate blunt
estrogen-induced apoptosis in
estrogen deprived
breast cancer cell populations. As a result
breast cancer develops during long-term
hormone replacement therapy (HRT). A new
synthetic progestin with
estrogen-like properties, such as the 19
nortestosterone derivatives used in
oral contraceptives, will continue to protect the uterus from unopposed
estrogen stimulation but at the same time, reinforce apoptosis in vulnerable populations of nascent
breast cancer cells.