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Relationship of prior hormonal therapy to subsequent estramustine phosphate treatment in advanced prostatic cancer.

The relationship of prior hormonal therapy to subsequent response on estramustine phosphate (Estracyt) was examined in 107 patients with advanced prostatic cancer treated in two different Phase II chemotherapy trials. In both trials patients with the longest prior hormonal treatment were the least likely to respond to estramustine phosphate. Patients in the series from the National Prostatic Cancer Project with a response classification to prior hormonal therapy had only a 26 per cent response to subsequent estramustine phosphate therapy, whereas 40 per cent of those with no prior response to hormonal therapy responded to estramustine phosphate. This latter group had the shortest average disease duration from diagnosis. The sample of prostate cancers studied appeared to include groups that were sensitive to both hormones and cytotoxic activity as well as to either of these two alone. These data support the contention that estramustine phosphate may act both as an estrogenic and a cytotoxic agent.

Aged

Binding characteristics of a major protein in rat ventral prostate cytosol that interacts with estramustine, a nitrogen mustard derivative of 17 beta-estradiol.

The tissue distribution of [3H]estramustine, the dephosphorylated metabolite of estramustine phosphate (Estracyt), in the male rat was compared to that of [3H]estradiol 30 min and 2 hr following i.p. administration. In contrast to estradiol, estramustine was found to be efficiently concentrated in the ventral prostate gland by a soluble protein. The binding characteristics of this protein were studied in vitro using cytosol preparations of the gland. With a dextran-coated charcoal technique, the protein was found to bind estramustine with a broad pH optimum between pH 7 and pH 8.5, with an apparent Kd of 10 to 30 nM, and with a binding capacity of about 5 nmol/mg cytosol protein. The estramustine/protein complex was not retained by DNA-cellulose. None of the natural steroids tested inhibited the binding of 10 nM [3H]estramustine by more than 35% (progesterone), even when added in 4500-fold excess. The presence of a nitrogen mustard moiety at position 3 of the steroid was necessary for high-affinity binding to the protein. The protein was calculated to constitute about 20% of the total cytosol protein content.

Animals

The use of estramustine and prednimustine versus prednimustine alone in advanced metastatic prostatic cancer patients who have received prior irradiation.

Estramustine has been shown previously to be an effective drug in the treatment of metastatic prostatic cancer, demonstrating significant objective and subjective responses in long-term non-randomized trials and in other randomized trials. In this study prednimustine alone has shown a minimal over-all objective response rate of 12.9% of the cases, although with marked subjective improvement of pain relief and patient performance status. The combination of prednimustine with estramustine did not result in improvement of objective or subjective response parameters. The effects in terms of responses or in terms of toxicity for either agent were not additive when they were given in combination. Cross-over for those patients whose disease progressed on prednimustine therapy to estramustine had some benefit in over-all survival. Prednimustine alone or in combination with estramustine may be used safely and could improve markedly the quality of life for irradiated patients with advanced prostatic cancer who failed on hormonal treatment and have too poor a bone marrow reserve to be treated by other currently available myelosuppressive agents.

Chlorambucil

Purification and distribution of a major protein in rat prostate that binds estramustine, a nitrogen mustard derivative of estradiol-17 beta.

A protein in rat ventral prostate cytosol that binds estramustine [estradiol 3-bis(2-chloroethyl)carbamate) was purified to homogeneity by using chromatography on DEAE-cellulose, Sephadex G-100 (superfine), octyl-Sepharose (CL-4B, and polyacrylamide gel electrophoresis. The estramustine-binding protein was found to have a Mr of 46,000 as estimated by gel filtration. After analysis by polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate, the protein was found to consist of two subunits with Mr of about 20,000 and 18,000. After reduction of disulfide bridges, the protein was decomposed into three components with Mr of about 12,000, 11,000, and 8000. Amino acid analysis indicated that the protein is a glycoprotein. Antibodies against the protein were raised in rabbits and a radioimmunoassay was developed for it. The estramustine-binding protein constituted about 18% of the total protein in rat ventral prostate cytosol, was present in the dorsal and lateral lobes of the prostate, and was also detected in the pituitary gland, cerebral cortex, submaxillary gland, thyroid gland, adrenal gland, seminal vesicle, coagulating gland, epididymis, and preputial gland of the male rat. In female rats the protein was detected in cerebral cortex. Because the estramustine-binding protein is predominantly found in the accessory sexual glands of the male rat, it may be of importance for maintaining male fertility.

Amino Acids

Pilot study on the growth inhibition by estramustine phosphate (Estracyt) of rat mammary tumours sensitive and insensitive of oestrogen.

Rat mammary tumours induced by 7,12-dimethylbenz(a)anthracene had a higher concentration of 3H and 14C than muscle after injection of estramustine phosphate labelled with 3H in the oestrogen moiety and 14C in the alkylating moiety. Thin-layer chromatography showed that dephosphorylated estramustine phosphate was present in the tumours but no free oestradiol-17beta. The uptake of the drug in the tumours was parallelled by a dose dependant retardation of tumour growth and a prevention of tumour number increase. Estramustine phosphate also retarded growth of mammary tumours resistant to treatment with oestradiol-17 beta. It is concluded that estramustine phosphate has a greater effect on tumour growth than oestrogen.

9,10-Dimethyl-1,2-benzanthracene

Effect of oral estramustine phosphate on pituitary, gonadal, and adrenal function in the green monkey (Cercopithecus aethiops sabaeus).

We studied the effects of estramustine phosphate on pituitary, gonadal, and adrenal function in the green monkey. A 2-week course of estramustine phosphate (75 mg per day) reversibly suppressed the luteinizing hormone and testosterone response to luteinizing hormone-releasing hormone but did not affect pituitary-adrenal function assessed by the 11-deoxycorticosterone response to metyrapone. Treatment with oral estramustine phosphate also resulted in a significant increase in corticosteroid-binding globulin but did not affect a series of liver enzymes nor hematology. The results are consistent with a pure estrogen effect produced by hydrolysis of the carbamate-ester bona at a site distant from estrogen target tissues and could explain most of the reported in vivo effects of this compound.

Administration, Oral

Estramustine phosphate: metabolic aspects related to its action in prostatic cancer.

Estramustine phosphate, a drug effective in a substantial number of patients with cancer of the prostate who had failed on other forms of therapy, has been shown to be split into its constituents, that is estradiol-17beta and the carbamate nitrogen mustard by non-cancerous and cancerous human prostatic tissues. This fact may explain, in part, the mechanism of action and efficacy of the drug in patients with cancer of the prostate. In addition to presenting results on the hydrolysis and its products accomplished by human prostatic tissues we discuss the limitations of extrapolating animal results with estramustine phosphate to the human condition and possible parameters that bear upon the insignificant toxic and estrogenic effects observed in patients given estramustine phosphate.

Adenocarcinoma

Inhibition by estramustine phosphate on estradiol and androgen binding in benign and malignant prostate in humans.

Specific cytoplasmic androgen and estrogen binding has been measured in human benign prostatic hypertrophy and carcinomatous tissue. In vitro support for the binding of estramustine phosphate (Estracyt) to both estradiol- and dihydrotestosterone-binding sites is presented, which in part could explain the clinical effect of estramustine phosphate when pure estrogenic compunds are not effective.

Androgens

Treatment of stage D hormone-resistant carcinoma of the prostate with estramustine phosphate.

We report on 51 patients with hormone-resistant, stage D prostatic carcinoma who were treated with estramustine phosphate and followed for at least 6 months. Of the 51 patients 5 (10 per cent) had a partial objective response, 30 (59 per cent) remained stable and 16 (31 per cent) had progression of the disease. All of those patients who had a partial response or remained stable also experienced subjective improvement as judged by relief of pain and performance status. Approximately 8 per cent of the patients will be unable to take estramustine phosphate because of intolerable gastrointestinal side effects.

Aged

The treatment of oestrogen-escaped carcinoma of the prostate with estramustine phosphate.

30 patients with oestrogen-escaped carcinoma of the prostate have been treated with estramustine phosphate (Estracyt). 27% showed a partial objective response and 33% had a subjective response. The terms used for defining a response are challenged and it is recommended that comparative controlled trials are necessary to judge the place of this drug in the management of advanced prostatic cancer.

Clinical Trials as Topic

Treatment of advanced prostatic carcinoma with estramustine phosphate (Estracyt).

Estramustine phosphate (Estracyt) was used in the treatment of 154 patients with carcinoma of the prostate in stage IV. Sixty-three patients were given Estracyt from the outset (primary treatment group) and 91 had previously received some other endocrine therapy (secondary treatment group). All of the patients were observed for more than one year. The drug was given intravenously and/or orally. Objective remissions occurred in 46 (73.0%) of the 63 patients in the primary treatment group and subjective remissions in all the objective responders and in 12 additional patients (92.0%). The corresponding figures for the secondary treatment group were 28 (30.7%) and 52 (57.1%) of 91. The side-effects were negligible, and the drug was well tolerated. No cumulative toxic effect was observed in patients who had been receiving the treatment for more than five years. In our opinion the compound is valuable in the treatment of advanced prostatic carcinoma (stage IV).

Acid Phosphatase

Treatment of oral estramustine phosphate (Estracyt) in prostatic carcinoma: influences on lipid and carbohydrate metabolism.

Estramustine phosphate (Estracyt), a combination of estradiol and nitrogen mustard given to males with prostatic carcinoma, had the same effect on serum lipids, lipoproteins, and serum phosphoglyceride fatty acid composition as ethynyl estradiol (Etivex). The characteristic effects on serum lipids caused by both drugs, i.e., a reduction in serum cholesterol and an increase in serum phospholipids, were apparently expressions for reduced low density lipoproteins and increased alpha-lipoproteins. Serum lecithin fatty acid composition revealed during the administration of both drugs a characteristic increase in palmitic acid (16:0) and a decrease in stearic acid (18:0), interpreted as evidence for a cholestatic, although subclinical, liver involvement. Similar changes have earlier been revealed in women given ethynyl estradiol; however, the increase in serum triglycerides and very low density lipoprotein cholesterol in young women was not duplicated in aged males with prostatic carcinoma. Furthermore, in aged males, the administration of these estrogens did not change carbohydrate metabolism but did produce an increase in adipose tissue lipoprotein lipase.

Adipose Tissue