[Tumor-oriented anti-cancer agent with estrogen as a carrier]

Tumor oriented anticancer agents with estrogen as a carrier have been extensively studied since 1950's. Only Estracyt and bestrabucil have been evaluated to be useful in clinical trials. Although the use of estrogen as a carrier for anticancer agents aimed at the development of the anticancer drug for the receptor mediated chemotherapy, these two drugs did not show any affinity to estrogen receptor. The history tells us that the development of anticancer agents for the estrogen receptor mediated chemotherapy is extremely difficult. Estracyt is reported to exert its anticancer effect on prostate cancer through the specific binding to the estramustine binding protein (EMBP) which is present only in the prostate gland and cancer. Bestrabucil shows the selective uptake by the various malignant cells and is indicated that bestrabucil exerts its anti-cancer effects on various malignant tumors including breast cancer and hematopoietic malignancy, through the affinity to malignant cells. The mechanism is unknown and to be elucidated.