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

Steroid-linked nitrogen mustards as potential anticancer therapeutics: a review

Nitrogen mustards, an important class of drugs for cancer therapy, are known as DNA alkylating agents. The nitrogen mustards are highly reactive and, as a consequence, lack of selectivity and produce several adverse side effects. In order to minimize these undesirable effects, the attachment of nitrogen mustards to a steroidal hormone with affinity for its receptor can lead to highly selective and less toxic antineoplastic therapeutics. This review will focus on the design, synthesis and evaluation of such steroid-nitrogen mustard hybrids as antineoplastic agents. Among these compounds, modified steroids with aromatic nitrogen mustards linked by an ester function were found to have better DNA alkylating properties, improved selectivity as well as low toxicity. This article is part of a Special Issue entitled "Synthesis and biological testing of steroid derivatives as inhibitors".

Antileukemic and Cytogenetic Activity by Triple Administration of Three Modified Steroidal Derivatives of Nitrogen Mustards

Combination chemotherapy is widely and routinely used for most cancer patients. The main objective of this study is an effort to develop new anticancer drugs and procedures with enhanced antitumor activity and reduced toxicity. This study was designed to determine the antileukemic and cytogenetic activity of five mixtures of three specific steroidal esters of aromatic nitrogen mustards in different proportions. This is the next step of two previous studies where the combination of two such esteric analogues was investigated with promising results. All of the five mixtures used proved active against leukemia P388 and in the induction of sister chromatid exchanges, indicating that the combination of the same class of compounds can be successful, especially when a highly potent agent is combined with another less active but probably mechanistically supplementary one. These results can be used in future experiments in order to further scout the specific role of the steroidal part of these molecules in the antileukemic potency of them.

Structure???anti-leukemic activity relationship study of B- and D-ring modified and non-modified steroidal esters of chlorambucil

In order to study the role of the steroidal moiety on the expression of anti-leukemic activity, we synthesized six derivatives of chlorambucil (CHL), and tested them on leukemias P388 and L1210 in vivo and in normal human lymphocytes in vitro. Five of the six tested compounds produced submultiple toxicity, while the measured anti-leukemic potency was significantly increased. The lactamization of the B-steroidal ring rendered the molecules more potent, but the corresponding 7-oxidized derivatives proved better in both leukemias tested. The lactamization of the D-steroidal ring afforded potent compounds, regardless of the configuration of the B-ring. The best among all derivatives contains both chemical modifications and is intended as a promising key molecule that must be further studied. We speculate that in leukemic cells a tumor-specific protein is overexpressed, the steroid has the ability to bind and block this protein from carrying out its normal function, and the drug-protein complex prevents the repair of the adducts. The synthesis, physicochemical and spectroscopic data of these compounds and a modified route for the synthesis of CHL are also reported.

Structure???anti-leukemic activity relationship study of B- and D-ring modified and non-modified steroidal esters of chlorambucil??s active metabolite

We have studied the effect of modification of the B-steroidal ring to lactamic on the anti-leukemic potency of D-modified and D-non-modified steroidal esters of chlorambucil's active metabolite. The compounds synthesized were studied against leukemias P388 and L1210 after the subsequent estimation of their toxicity in vivo, and for their ability to induce sister chromatid exchanges (SCEs) and to inhibit cell proliferation in normal human lymphocytes in vitro. The in vitro results correlated well, on a molar basis, with the results obtained from the study of the anti-leukemic potency. In a comparative study, the B-lactamic steroidal derivatives proved less active than the 7-oxidized ones against both leukemias. The presence of the -NHCO- group in the B-steroidal ring did not have the same positive effect on the biological action of chlorambucil's active metabolite esters as in the D-lactamic ring. However, this new modification of the B-ring rendered the final esteric derivatives much more toxic, compared with to the corresponding esters with a simple B-ring. This loss of the anti-leukemic specificity, which occurs from the modification of the B-ring, is additional evidence for the role of the steroidal part on the mechanism of action of these promising compounds. This provides support for the notion that the steroidal part of these molecules is not just a simple biological carrier, as has been speculated for many years.

Preclinical studies on NSC290205 aza-steroid alkylator activity in combination with adriamycin against lymphoid leukaemia

Summary NSC290205 (A) is an hybrid synthetic antineoplastic ester that is a combination of a d-lactam derivative of androsterone and an alkylating derivative of N,N-bis(2-chloroethyl)aniline. We tested NSC290205 for synergistic antileukaemic activity with adriamycin (ADR), (i) in vitro against the human lymphoid leukaemia cell lines: CCRF-CEM, MOLT-4, and RPMI-8226, (ii) in vivo against P388 lymphocytic and L1210 lymphoid murine leukaemias (at incipient and advanced phase). Our results indicated significant cytostatic and cytotoxic synergy of NSC290205 and ADR in vitro. We further examined these results in vivo by replacing cyclophosphamide in the standard CHOP (cyclophosphamide, hydroxydaunomycin, Oncovin, prednisone) regimen with NSC290205 (AHOP) and comparing the efficiency of these two regimens in vivo. Although treatment of P388 and L1210 with cyclophosphamide or NSC290205 alone yielded equivalent results, AHOP produced a clear benefit for survival compared with CHOP against advanced leukaemias, confirming the in vitro observations [higher percentage increase in median lifespan of treated animals over the untreated (control): 188% and 239% in L1210, 308% and 353% in P388, P < 0.01, for CHOP and AHOP respectively]. AHOP also proved to be more genotoxic and cytostatic than CHOP, inducing higher sister chromatid exchange levels and cell division delays on P388 cells in vivo. NSC290205 showed superior antineoplastic potential against lymphoid leukaemia and significant synergy with ADR, producing an excellent therapeutic outcome.

The allylic 7-ketone at the steroidal skeleton is crucial for the antileukemic potency of chlorambucil’s active metabolite steroidal esters

We have investigated the role of the allylic 7-ketone in oxidized Delta5-steroids on antileukemic activity. We synthesized and studied a series of oxidized and non-oxidized steroidal esters of p-N,N-bis(2-chloroethyl)aminophenylacetic acid (PHE), chlorambucil's active metabolite. In a comparative study of these 7-keto derivatives, on a molecular basis, regarding their ability to induce sister chromatid exchanges (SCEs) and to inhibit cell proliferation in normal human lymphocytes in vitro, the results with these 7-keto derivatives, on a molecular basis, correlated well with their antileukemic potency against leukemia P388- and L1210-bearing mice, which proved to be significantly increased compared to that of the non-oxidized derivatives. Our results indicate that the role of the steroidal skeleton it is not only for the transportation of the alkylating agent into the cell, but also contributes directly to the mechanism of antileukemic action, by an as-yet unknown way. The main conclusion from this study is that the existence of the allylic 7-keto group in the skeleton of the Delta5-steroidal esters impressively enhances their antileukemic activity, while the toxicity remains at clinically acceptable levels, suggesting that this structural modification should be further investigated.

In vitro antigenotoxic potential of acitretin in human lymphocytes treated with the antineoplastic alkylating agent ASE (NSC-71964)

Acitretin is widely used in the systemic treatment of severe forms of psoriasis and other skin disorders. ASE, namely 3beta-hydroxy-13alpha-amino-13,17-seco-5alpha-androstan-17-oic-13,17-lactam-p-bis(2-chloro-ethyl)amino phenylacetate (AzaSteroidalEster, NSC-71964), is an alkylating agent with antineoplastic activity and mutagenic properties. The aim of this study was to investigate the possible genotoxic and/or antigenotoxic effects of acitretin in human lymphocyte cultures in vitro, using sister chromatid exchange (SCE) and cytokinesis-blocked micronucleus (CBMN) assays. Micronucleus (MN) analysis was achieved in combination with fluorescence in situ hybridization (FISH), using an alpha-satellite DNA pancentromeric probe. It was found that acitretin alone demonstrated no clastogenic or aneugenic activity. However, simultaneous incubation of lymphocyte cultures with ASE and acitretin resulted in a reduction of ASE-induced SCEs. For MN analysis lymphocytes were treated with ASE and acitretin at 21 and 41 h after culture initiation, corresponding to G1 and G2 phases, respectively, and lasted until cell harvest. Acitretin caused a decrease in ASE-induced MN when treatment of cells started at 41 h, but exerted no effect on them when treatment started at 21 h. These findings suggest that acitretin exerts antigenotoxic effects in human lymphocyte cultures, the expression of which may be related to the cycle phase of the cells upon onset and duration of the treatment, at least as far as MN frequency is concerned.

Synthetic approaches for the synthesis of a cytostatic steroidal B-D bilactam

A new synthetic procedure and a modification of the original method described in the literature for the synthesis of the steroidal B-D bilactam, 3 beta-hydroxy-7 alpha,17 alpha-diaza-B,D-dihomo-5-androsten-7,17-dione are reported. The key step in the modified method involved protection of the D-lactamic nitrogen atom of 3 beta-acetoxy-17 alpha-aza-D-homo-5-androsten-17-one using a reagent of specific electrophilicity (due to the stereoelectronic properties of the cyclic amide), as Beckmann rearrangement of the B-steroidal ring was hindered, possibly via long range effects, by the presence of the unprotected D-lactamic moiety. Using the 3 beta-acetoxy-5-androsten-17-one as starting material, a new synthetic procedure was developed through ketalization of the 17-ketone and allylic oxidation to the 7-ketone, which was subsequently followed by Beckmann rearrangement of the B- and D-steroid rings. Both approaches resulted in 45 and 67% yields of the desired B,D-bilactam, respectively, in contrast to the 15% yield, which has been reported in the literature.

Structure--anticancer and structure--genetic activity relationships of homo-aza-steroidal esters of N,N-bis(2-chloroethyl)aminocinnamic acid isomers

Four steroidal lactams of the A- and D-rings were used for the esterification in the C-3 or C-17 positions, respectively, of their nuclei with the N,N-bis(2-chloroethyl)aminocinnamic acid isomers. The condensation reaction of the hydroxylic group of the steroidal lactams with each mustard was effected in dichloromethane in the presence of the catalyst p-dimethylaminopyridine and dicyclohexylcarbodiimide as dehydrating agent. The esters were obtained in pure form after column chromatography, and their structures were verified and confirmed by analytical methods (IR and UV spectra). The 12 esters were tested in vivo against P388, L1210 leukemias, Ehrlich ascites tumor, and melanoma B16. The esters 3 alpha-hydroxy-13 alpha-amino-13,17-seco-5 alpha-androstan-17- oic-13,17-lactam-o,m,p-N,N-bis(2-chloroethyl)aminocinnamates, in which the alkylating agents are linked to the modified steroid in the axial position, are inactive in the above experimental animal tumor systems. The effect of the homo-aza-steroidal esters of N,N-bis(2-chloroethyl)aminocinnamic acid isomers on the incorporation of radioactive precursors into DNA, RNA, and proteins of L1210, P388 leukemias, Ehrlich ascites tumor, and baby hamster kidney cells was investigated. Higher inhibitory effects on the incorporation of the radioactive precursors was obtained with the ortho-derivatives, yielding > 40% inhibition of thymidine incorporation in all tumor lines tested. The effect of four esters in which the m- N,N-bis(2-chloroethyl)aminocinnamic acid is linked to the modified steroids on sister chromatid exchanges in human lymphocyte culture was investigated.

Altered protein synthesis rate in ovaries of D. melanogaster caused by new antitumour alkylating agents

1. The effect of two homo-aza-steroidal esters with antineoplastic activity, namely 3 beta-hydroxy-13 alpha-amino-13,17-seco-5 alpha-androstan-17-oic-13,17-lactam-p-bis(2-chloroethyl)aminoph enoxyacetate (NSC 294859) and 3 beta-hydroxy-13 alpha-amino-13,17-seco-5 alpha-androstan-17-oic-13,17-lactam-p-bis(2-chloroethyl)aminoph enylacetate (ASE) on protein synthesis rate was studied in ovaries of Drosophila melanogaster females. 2. Two different concentrations for each compound were examined. 3. Both esters containing the same alkylating agent have been shown to decrease protein synthesis in relation to control.

Synergistic induction of cytogenetic damage by the homo-aza-steroidal ester of p-bis(2-chloroethyl)aminophenylacetic acid in combination with caffeine in human lymphocytes in vitro and in Ehrlich ascites tumour cells in vivo

We studied the effects of caffeine alone or in combination with homo-aza-steroidal ester of p-bis(2-chloroethyl)aminophenylacetic acid (ASE, NSC 290205) on the frequency of SCEs and lymphocyte proliferation kinetics. Caffeine was found to act synergistically with ASE on the induction of SCEs when the two components were administered in combination. Caffeine was also found to act synergistically with ASE in inducing cell-division delays. Enhanced cytogenetic damage by ASE was observed when Ehrlich ascites tumour cells (EAT cells) were exposed in vivo to caffeine. ASE alone or in combination with caffeine caused a dose-dependent increase in SCE rates and cell-division delays. SCEs were demonstrated in EAT-bearing mice, by the i.p. injection of BrdUrd adsorbed onto activated charcoal, 1 h after the i.p. injection of ASE and/or caffeine.

A comparative analysis of data on the clastogenicity of 951 chemical substances tested in mammalian cell cultures

A literature review was conducted using original papers published during 1964-1985 on the in vitro clastogenicity of chemical substances. Results of tests on 951 chemical substances were abstracted from over 240 reports to form the database. The evaluation of these data relied on each author's original conclusion on a positive or negative outcome. Of these 951 substances, 447 (47%) were consistently positive either with or without activation; 417 (44%) were negative in the direct test but not tested with metabolic activation systems; 4 were negative but tested only with activation; and 30 (3%) were clearly negative both with and without activation. The remaining 53 substances gave variable results when tested under different experimental protocols or in different cell types, but were positive in at least one test. Although discrepant results were found associated with some cell types, the addition of metabolic activation systems tended to eliminate such variability. No one cell appeared to be superior in response to all clastogens. For screening purposes, the choice of cell may thus depend more on the general usefulness and reliability of a cell type than on a strong response to a particular chemical. However, the use of a suitable metabolic activation system does appear to be of critical importance. The concentration at which clastogenic effects were detected varied extensively for different test substances, ranging from a minimum of 4.3 X 10(-8) to 6.9 X 10(2) mM. Possible mechanisms of action for substances active at only high levels are discussed, but no satisfactory explanation is available at this time. The relevance of tests conducted at concentrations high enough to alter significantly the osmolarity and other culture conditions is considered, and caution urged in the interpretation of test results obtained under physiologically stressful conditions. The clastogenic potential was compared quantitatively using an index of effective concentration (D20) and one which estimates the number of cells with exchange aberrations expected per mg/ml (TR) for data obtained by using a uniform protocol and cultures of Chinese hamster lung (CHL) cells. Both values were distributed over a wide range, demonstrating the variety of genotoxic potential in chemicals. In general, a substance which was active at only high concentrations produced fewer exchange-type aberrations. In vivo activity, as measured by tumourigenic effect and formation of micronuclei in bone marrow, tended to be greater for substances with a D20 below 10(-2) mg/ml and a TR value over 10(3).(ABSTRACT TRUNCATED AT 400 WORDS)

Induction of cytogenetic damage by modified steroidal derivatives of p-bis(2-chloroethyl)aminophenylacetic acid in human lymphocytes

The effect of modified steroids, containing alkylating agents, on SCE rates and on cell kinetics in cultured human lymphocytes was studied. The homo-aza-steroidal ester of p-bis(2-chloroethyl)aminophenylacetic acid (ASE) was found to be the most effective in causing markedly increased SCE rates and cell division delays. The androsterone ester of p-bis(2-chloroethyl)aminophenylacetic acid (AE-CAPA) was found to be next in order of effectiveness with the lactone ester (LE-CAPA), chlorambucil ester 3 beta-hydroxy-13a-amino-13,17-seco-5a-androstan-17-oic-13,17-lactam (CBC-HAAL) and chlorambucil (CBC) following. p-Bis(2-chloroethyl)aminophenylacetic acid (CAPA) had only a small effect and 3 beta-hydroxy-13a-amino-13,17-seco-5a-androstan-17-oic-13,17-lactam (HAAL) had no effect at all. A correlation between potency for SCE induction, effectiveness in cell division delay and previously established antitumor activity of these drugs was observed.

Mutagenicity and clastogenicity of the antineoplastic agents homo-azasteroidal ester of p-bis(2-chloroethyl)aminophenyl acetic acid and chlorambucil

The mutagenic and clastogenic effects of the antineoplastic agents homo-aza-steroidal ester (ASE) and chlorambucil (CBC) were tested for their ability to induce mutations in the Salmonella/microsome system and SCE in CHO cells in culture. ASE was found to be positive in strains TA1535 and TA100 and in the newer strain TA102 with and without metabolic activation, while CBC caused histidine reversion in strain TA102 after the addition of mammalian liver microsomal extract (S9). In addition, both agents were found to be strongly positive for SCE induction. The mutagenic and clastogenic actions of both agents were of a dose-response type.