estramustine and Carcinoma-256--Walker

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.

Topics: Animals; Antineoplastic Agents; Carcinoma 256, Walker; Chlorambucil; Drug Carriers; Estradiol; Estramustine; Estrogens; Humans; Male; Prostatic Neoplasms; Rats

Using cultured HeLa S3 cells an ID50 of 2.5 micrograms/ml was found after a twenty-four-hour incubation with estradiol-17 beta- 3N -bis-(2-chloroethyl) carbamate (estramustine). Similar ID90 values were found in two Walker 256 rat carcinoma cell lines which were either sensitive or resistant to nitrogen mustards. Alkaline elution methodology revealed the complete absence of DNA strand breaks or cross-links in cells receiving up to 10 micrograms/ml estramustine for twenty-four hours. Nuclear uptake was 1.34 per cent of the available drug, one third of which was hydrophobically associated with the protein/phospholipid components of the nuclear matrix. In the human prostatic cell lines DU145 and PC3 , estramustine caused a drastic dose-dependent increase in the mitotic index. This increase resulted from an arrest of cells in metaphase, with highly contracted disoriented chromosomes present. Rapid reverse of the arrest on removal of drug resulted in cell death. Neither nor-nitrogen mustard nor estradiol demonstrated antimitotic properties. The lack of macromolecular alkylation together with the observed antimitotic effects predict a mechanism of action for estramustine which is distinct from either of its constituent components.

Topics: Alkylation; Animals; Carcinoma 256, Walker; Cells, Cultured; Drug Evaluation, Preclinical; Estramustine; Female; HeLa Cells; Humans; Male; Mammary Neoplasms, Experimental; Mitosis; Nitrogen Mustard Compounds; Prostatic Neoplasms; Rats; Structure-Activity Relationship

Estramustine is cytotoxic in HeLa and Walker 256 carcinoma cells (with or without acquired resistance to nitrogen mustards) at concentrations equivalent to other alkylating agents. Even at lethal estramustine levels, no damage to DNA occurs. Instead, a disproportionately high amount of intact estramustine binds hydrophobically to the structural proteins of the nucleus, the nuclear matrix. In HeLa cells, estradiol receptors are absent, and estradiol per se is not toxic. Thus, estramustine has a mechanism of action distinct from that of steroids and alkylating agents and may induce cytotoxicity through interactions with the proteins of the nuclear matrix.

Topics: Animals; Antineoplastic Agents; Carcinoma 256, Walker; Cells, Cultured; DNA, Neoplasm; Estramustine; HeLa Cells; Humans; Macromolecular Substances; Nitrogen Mustard Compounds; Rats