The effects of some steroidal alkylating agents on experimental animal mammary tumor and leukemia systems

In vitro synergism between estrogens and cytotoxic agents

Two lines of research intending to achieve synergism between cytotoxic agents and estrogens for breast cancer treatment are pursued in our laboratory. According to a screening procedure we select cytotoxic-linked estrogens which bind to estrogen receptors and thereby would be specifically concentrated into the tumor cells. A mesylate derivative of estrone has emerged from our investigations. This compound displays a very strong binding affinity for the receptors and inhibits the growth of the receptor-positive MCF-7 breast cancer cell line. The lack of growth inhibition in the receptor-negative line Evsa-T indicates that it is devoid of major non-specific cytotoxicity. We attempt to enhance the vulnerability of the tumor cells by producing an estrogen-induced modification of their chromatin. The in vitro exposure of isolated uterine nuclei to uterine cytosol preincubated with estradiol increases their ability to bind [3H]actinomycin D. Identical results are obtained with MXT mouse mammary tumors. Experiments are in progress to settle whether these changes are associated with enhanced cell killing.

Approaches to prostatic cancer chemotherapy using the Dunning R3327H prostatic adenocarcinoma

Androgen-responsive cells: To determine if testosterone or dihydrotestosterone is the main trophic hormone of prostatic adenocarcinoma, we have treated Dunning R3327H prostatic adenocarcinoma-bearing rats with 6-methylene progesterone, which blocks conversion of testosterone to dihydrotestosterone. Copenhagen-Fisher rats were treated with steroid (20 mg/Kg daily) immediately following implantation of tumor and thereafter for 117 days. There was a 92% inhibition of growth of tumors and a lesser effect upon prostate and seminal vesicles. Tumor-free body weights remained unchanged. Both treated and untreated tumors had equivalent DNA content on a per weight basis. This result supports the thesis that prostatic adenocarcinoma requires dihydrotestosterone for growth. Androgen-insensitive cells: Advanced prostate cancer does not respond to endocrine therapy but is temporarily controlled by the cytotoxic steroid estramustine. The latter shows significant selective binding to prostatic protein. To develop chemotherapeutic agents that will control androgen-insensitive cells and possess improved selectivity for prostatic protein, we have studied a number of steroids for their ability to displace 3H-labeled estramustine from prostatic cytosolic proteins. Surprisingly, a carbamido substituent at the C17 position was found to confer significant binding affinity for prostatic estramustine-binding protein. Extension of this structural characteristic to the estramustine type of molecule is being studied.

Cytostatic activity of steroid linked nitrosoureas

First investigations on the therapeutic activity of a new group of steroid-linked N-(2-chloroethyl)-N-nitrosocarbamoyl-L-alanine esters (CNC-L-alanine esters) in a nitrosourea-sensitive rat leukemia (L 5222) characterized by a relatively high content of glucocorticoid binding sites are presented. Despite a considerable range of optimal and toxic doses of the different analogs, the respective therapeutic ratios do not appear to be significantly influenced by the nature of the carrier molecules to which CNC-L-alanine is attached. However several steroid-linked representatives are distinctly more active than CNC-L-alanine. The androsterone-3-ester and the dihydrotestosterone-17-ester, in particular effected high percentages of cures in contrast to CNC-L-alanine.

Further studies on the anti-neoplastic activity of 3 beta-hydroxy-13 alpha-amino-13,17-seco-5 alpha-androstan-17-oic-13,17-lactam [p-[bis(2-chloroethyl)amino]-phenyl]acetate (NSC 290205)

The modified steroidal alkylating agent 3 beta-hydroxy-13 alpha-amino-13,17-seco-5 alpha-androstan-17-oic-13,17-lactam [p-[bis(2-chloroethyl)amino]phenyl]acetate (NSC 290205) is active in treating the LX-1 lung and MX-1 breast xenografts as well as a number of rodent tumors. Of 13 tumors tested, activity has been shown in 10 systems. Two systems have not received adequate testing and negative results were recorded in 1 system.

Antitumor activity of homo-aza-steroidal esters of [p-[bis(2-chloroethyl)amino]phenyl]acetic acid and [p-[bis(2-chloroethyl)amino]phenyl]butyric acid

Three new modified steroidal alkylating agents, 3 beta-hydroxy-13 alpha-amino-13,17-seco-5 alpha-androstan-17-oic-13,17-lactam-p-bis(2-chloroethyl)aminophenylacetate, 3 beta-hydroxy-13 alpha-amino-13,17-seco-5 alpha-androstan-17-oic-13,17-lactam-p-bis-(2-chloroethyl)aminophenylbutyrate, and 17 beta-hydroxy-3-aza-A-homo-4 alpha-androsten-4-one-p-N,N-bis(2-chloroethyl)aminophenylacetate are active in treatment of L1210 and P388 leukemias. A stereoisomer of the first compound, 3 alpha-hydroxy-13 alpha-amino-13,17-seco-5 alpha-androstan-17-oic-13, 17-lactam-p-bis(2-chloroethyl)aminophenylacetate, was tested in L1210 leukemia. This stereoisomer, in which the alkylating agent is linked to the modified steroid in the axial position, is active only as much higher doses in L1210 leukemia. The results of testing these compounds and previous results from similar compounds allow certain conclusions to be drawn regarding structure-activity relationships. The presence of the lactam moiety is the major structural feature that confers activity in the murine leukemias. The steric arrangement of the alkylating moiety at position 3 and the hydrogen atom at position 5 influence toxicity and antileukemic activity.

Chromosome damage and SCE induced by the cytostatic factor homo-aza-steroidal ester of P-bis (2-chloro-ethyl) amino phenyl acetic acid in CHO cells in culture

The cytogenetic effects of homo-aza-steroidal ester (ASE) on Chinese hamster ovary (CHO) cells in vitro are reported. It was found that treatment of cells with a dose as low as 0.025 micrograms/ml of ASE causes a significant number of abnormal metaphases containing mostly chromatid-type aberrations. Similarly, significant frequencies of SCE were induced with only 0.075 micrograms/ml of ASE.

New steroidal nitrosoureas

Reformatsky reaction of 3beta, 21-diacyloxy-and 3beta-methoxy-21-acyloxy-5-pregnen-20-one with ethyl bromoacetate yields, through an intramolecular 1,2-acyl migration, 38, 20 XI-diacyloxy- and 3 beta-methoxy-20 XI-acyloxy-14alpha-card-5-enolide respectively. The 20 XI-acyloxy-14, alpha-card-5-enolides were converted into the respective 20 XI-hydroxy-14alpha-card-5-enolides and the 14 alpha card-5,20(22)-dienolides. Experimental support to the proposed intramolecular 1,2-acyl migration is provided by the use of labelled compounds.

Low-density lipoprotein as a potential vehicle for chemotherapeutic agents and radionucleotides in the management of gynecologic neoplasms

Cholesterol metabolism was studied in cells from two established gynecologic cancer cell lines which were maintained in monolayer cultures. The cell lines were derived and established from poorly differentiated epidermoid cervical carcinoma (EC-50) and endometrial adenocarcinoma (AC-258). The specific activity of 3-hydroxy-3-methylglutaryl coenzyme A (HMG CoA) reductase, the rate-limiting enzyme of cholesterol de novo synthesis, in AC-258 cells (1,700 pmoles x mg-1 microsomal protein x min-1) was three times higher than that found in EC-50 cells (550 pmoles x mg-1 microsomal protein x min-1). However, epidermoid cervical cancer cells (EC-50) metabolized low-density lipoprotein (LDL), the major transport vehicle for cholesterol in plasma, at a very high rate (14,000 ng x mg-1 cell protein x 6 hours). This rate is fifteen times greater than the rate observed in fetal adrenal tissue and fifty times greater than the rate observed in nonneoplastic gynecologic tissue, each in organ culture. Both cancer cells (EC-50 and AC-258) in monolayer culture were shown to have specific receptors for LDL. These cancer cells demonstrate no defect in LDL metabolism, and lysosomal degradation of LDL was blocked by chloroquine. From the results of studies of specific binding of LDL in tissues obtained from nude mice it was demonstrated that membrane fractions prepared from EC-50 cells, after propagation in the mice, contained fifteen to thirty times more specific binding capacity for [125I]iodo-LDL than vital organs of the mouse, such as the liver, heart, lung, kidney, or brain. The results of these studies are suggestive that certain tumor cells might have a higher affinity for LDL than normal tissues and cytotoxic drugs or radionucleotides ligated to the LDL macromolecule may be utilized for the specific delivery of these agents.

New compounds: antitumor activity of 3beta-hydroxy-13alpha-amino-13,17-seco-5alpha-androstan-17-oic-13,17-lactam 4-[p-[bis(2-chloroethyl)amino]phenyl]butyrate

3beta-Hydroxy-13alpha-amino-13,17-seco-5alpha-androstan-17-oic-13,17-lactam 4-[p[bis(2chloroethyl)amino]phenyl]butyrate was prepared by reacting 4-[p-[bis(2-chloroethyl)amino]phenyl]butyryl chloride hydrochloride with 3beta-hydroxy-13alpha-amino-13,17-seco-5alpha-androstan-17-oic-13,17-lactam. They cytostatic action of the ester was investigated on two tumor systems (B16 melanoma on C57 b1 mice and T8-Guerin on rats).

A phase II study of phenesterin (NSC-104469)

Phenesterin was evaluated in 222 patients with two different dosage regimens, one by daily treatment and the other with an intermittent schedule. Toxicity was moderate with both programs. The largest group of patients treated had breast cancer; they experienced a 10% response rate. Of interest was a higher percentage of responses in ovarian cancer (36%). An expanded study of patients with ovarian cancer would be of interest.

Potentiation of vincristine cytotoxicity by hormones: corticosteroids, androgens, estrogens and progestins

Using an in vitro system to evaluate the simultaneous use of two drugs, we previously have confirmed the synergism of vincristine and prednisolone cytotoxicity against lymphoid cells. Experiments were now carried out to determine whether other steroid hormones can be substituted for prednisolone. Partial or complete potentiation of vincristine cytotoxicity comparable to that achieved by the addition of prednisolone was observed when the latter drug was replaced by a variety of mineralocorticoids (aldosterone, desoxycorticosterone and fludrocortisone), glucocorticoids (hydrocortisone, dexamethasone), androgens (testosterone, methyltestosterone, androsterone, dehydroepiandrosterone, etiocholanolone), estrogens (estrone, 17-beta estradiol) and progestins (progesterone, pregnanediol). No potentiation of cytotoxicity was observed when nonsteroidal hormones (thyroxin, ACTH) were added to vincristine. It is concluded that a wide variety of compounds with the basic perhydrocyclopentanophenanthrene nucleus of the steroid molecule are capable of enhancing the cytotoxicity achieved with vincristine.

Affinity of estradiol mustard for estrogen receptors and its enzymatic degradation in uterine and breast cancer cytosols

Estradiol mustard (EM) is the 3,17beta-diester of estradiol-17beta (E2) with the nitrogen mustard derivative chlorphenacyl. The ability of EM to bind to cytoplasmic estrogen receptors was tested by inhibition of the binding of 3H-E2 to rat uterine cytosol at 18 degrees C and 30 degrees C. At both temperatures an inhibition curve was observed in the presence of a large excess of drug, suggesting that the latter has a very weak binding affinity (100,000 times lower than E2). Incubation of uterine cytosol with increasing amounts of 3H-E2 in the presence and absence of an excess of EM indicated that the drug interacted with the receptors at the same sites as E2 (competitive inhibition). Preincubation of uterine cytosol at 18 degrees C with EM induced a progressive reduction of 3H-E2 binding capacity. This reduction also occurred, although to a lesser extent, when long-term incubation of the cytosol with EM was performed in the presence of labelled E2 from the start. The process was faster at 18 degrees C than at 4 degrees C and did not occur with EM preincubated in homogenization buffer. Exchange assays by 3H-E2 of uterine receptors preincubated with labelled E2 and excess EM indicated that the drug-induced inhibition of binding capacity was reversible and produced no apparent alteration of the receptors. Furthermore, the rate of exchange was similar to that observed with receptors previously filled with unlabelled E2. In 9 "receptor-positive" cytosols from human breast cancers, time-course study of the binding of 3H-E2 in the presence of excess of EM yielded similar results as those obtained with rat uterine cytosol. These results show that EM has a very low binding affinity for the extrogen receptors and that it is metabolized into one or several compounds of higher binding affinity. They suggest that EM is probably not significantly concentrated by the estrogen target tissues such as mammary cancers. Therefore, the drug is unlikely to be very valuable in the treatment of breast cancer through a specific mechanism involving concentration by the estrogen receptors.

Therapeutic effect of Leo 1031, an alkylating corticosteroid ester, in lymphoproliferative disorders. I. chronic lymphocytic leukaemia

Leo 1031, a chlorambucil ester of prednisolone, has been administered orally to 15 patients with chronic lymphocytic leukaemia (CLL) continuously for 1-29 months (mean 12.5). Seven patients were previously untreated and eight had been treated with prednisolone, radiotherapy and/or alkylating agents. The initial daily dose was generally 8-16 mg and the maintenance dose was 6-8 mg. Allopurinol was given concurrently. In 14 of 15 patients a reduction of the leucocyte count was observed and a reduction, in most instances, of lymphadenopathy or splenomegaly, or both. In seven patients the Hb concentration was improved. Significant toxic effects on bone marrow function have been observed in one patient. Two patients developed urticaria. Our study suggests that the drug is effective in the treatment of CLL.

New compounds: fatty acid and long chain hydrocarbon derivatives containing a strong chelating agent

Fatty acid and long chain hydrocarbon analogs that contain a strong chelating group were synthesized as part of an effort to determine if the biological function of the fatty acid can be used to transport metallic isotopes to the myocardium.