Absence of swiveling at sites of intercalator-induced protein-associated deoxyribonucleic acid strand breaks in mammalian cell nucleoids

The sedimentation of DNA-nuclear protein complexes in 1.9 M salt-neutral sucrose gradients (nucleoid sedimentation) was used to examine the effects of the DNA intercalator 4'-(9-acridinylamino)methanesulfon-m-anisidide (m-AMSA) on mouse leukemia cell DNA. Mild detergent cell lysis and neutral pH make nucleoid sedimentation an extremely gentle, but sensitive, method to detect DNA scission. DNA breaks reduce the compaction of nucleoids and slow their sedimentation. Nucleoids from m-AMSA-treated cells sedimented as did those from untreated cells, indicating no detectable m-AMSA-dependent alterations in compaction despite an apparent underlying DNA break frequency of approximately 3 per 10(6) nucleotides, as measured by alkaline elution with proteinase. Mild proteinase digestion of cell lysates prior to nucleoid sedimentation unmasked some, but not all, of the underlying breaks. The frequency of DNA-protein cross-links in nucleoids from cells treated with m-AMSA was comparable to the single-strand break frequency produced by m-AMSA in whole cells. These results indicate that m-AMSA-induced DNA-protein cross-links conceal DNA breaks so as to prevent swiveling around the breaks within the nucleoids. This unique sort of DNA scission is consistent with the involvement of topoisomerases in the DNA breaks elicited by intercalators in mammalian cells.

Deoxyribonucleic acid breaks produced by 4'-(9-acridinylamino)methanesulfon-m-anisidide and copper

We have demonstrated that 4'-(9-acridinyl-amino)methanesulfon-m-anisidide (mAMSA), in the presence of Cu(II) ion, causes the breakage of plasmid pDPT275 and pBR322 superhelical form I DNA. In neutral pH, the degradative product was nicked, relaxed form II DNA, resulting from single-stranded DNA breakage. The extent of DNA breakage was both mAMSA concentration and Cu(II) concentration dependent. DNA breakage increased with increasing time of drug treatment. The mAMSA-Cu(II)-induced DNA breakage varied with pH values and also with the nature of the buffer systems. In both Tris-HCl and borate buffers the extent of DNA breakage increased with increasing pH. In Tris-HCl buffer (pH 7-9), only single-strand breaks were obtained, whereas in borate buffer (pH 9-10.5), linear form III DNA was obtained. At equivalent pH, the optimum buffer was borate. No breakage was observed at pH values below 6. The interaction of Cu(II) with mAMSA was examined by using absorption and fluorescence spectroscopies. Interaction of Cu(II) with mAMSA was characterized by a decrease in the absorption at 435 and 420 nm with a simultaneous increase at 330 nm. A highly fluorescent product was obtained upon reacting mAMSA with Cu(II), with an emission spectrum (excitation at 400 nm) showing a doublet at 430 and 450 nm and a shoulder around 480 nm. The spectral changes are also dependent similarly on the pH and the nature of buffer. Other divalent metal ions such as Co(II), Cd(II), Ni(II), and Zn(II) do not induce DNA breakage or spectral changes. The oAMSA isomer, which has no antitumor activity, is less effective in inducing DNA breakage than the mAMSA.

Mechanism of deoxyribonucleic acid breakage induced by 4'-(9-acridinylamino)methanesulfon-m-anisidide and copper: role for cuprous ion and oxygen free radicals

4'-(9-Acridinylamino)methanesulfon-m-anisidide (mAMSA) interacts with Cu(II) ion, as indicated by changes in the mAMSA absorption spectrum induced by Cu(II). The spectral changes are due to the oxidation of mAMSA by Cu(II), resulting in an oxidized mAMSA product and Cu(I). Two lines of evidence for the oxidation of mAMSA are as follows: (1) The spectral changes induced by manganese oxide, an oxidizing agent, were similar to those induced by Cu(II), and (2) the Cu(II)-induced spectral changes were reversed by a reducing agent, NADPH. Thin-layer chromatographic studies showed the oxidized mAMSA product to be N1-methylsulfonyl-N4-(9-acridinyl)-3-methoxy-2,5-cyclohexadiene-1, 4-diimine (mAQDI). The involvement of Cu(I) in the reaction was demonstrated by the use of two Cu(I)-specific chelating agents, neocuproine and bathocuproine. Neocuproine or bathocuproine chelated the Cu(I) ions in the mixture, producing Cu(neocuproine)2+ complex or Cu(bathocuproine)2+ complex. The stoichiometry of mAMSA-Cu(II) interactions was determined by titrating the mAMSA-Cu(II) mixtures with bathocuproine. Job plots of the absorbance at 480 nm showed a clear end point at a Cu(II)/mAMSA ratio of 1.5/1, indicating that 1.5 equiv of Cu(II) reacts with 1 equiv of mAMSA to produce 1.5 equiv of Cu(I). Cu(I) plays an important role in the mAMSA-Cu(II)-induced DNA breakage, since in the presence of neocuproine the DNA breakage is inhibited. Up to 200 microM, Cu(I) by itself is virtually ineffective, in contrast to the mixture of mAMSA and Cu(II).(ABSTRACT TRUNCATED AT 250 WORDS)

Phase II study of Amsacrine in refractory lymphomas. A report of the EORTC early clinical trials group

Forty-three patients with advanced measurable lymphoma, progressive after conventional therapy, were entered into a phase II study of m-AMSA 90-120 mg/m2 every 3 weeks. Five patients were ineligible and response could not be evaluated in four patients. For HD there were two partial responses (14%), lasting 6 and 41 weeks, in 14 evaluable patients. Among 20 evaluable patients with NHDL three (15%) achieved partial remission, but duration of response could not be evaluated. One patient with diffuse histiocytic lymphoma died of infection at 4 weeks, a second with lymphoblastic lymphoma was given high-dose steroids commencing at 6 weeks, and the third patient with nodular poorly differentiated lymphocytic lymphoma refused further treatment after one course. Leucopenia was more marked in patients with NHDL (WBC nadir X 10(9)/l, median 2.2, range 0.2-4.3) than in HD (WBC nadir X 10(9)/l, median 2.8, range 0.85-7.2), as was thrombocytopenia. There was one toxic death and one life-threatening infection, both secondary to myelosuppression. Non-haematological toxicity was mild. m-AMSA has marginal activity in previously treated lymphomas and causes considerable myelosuppression.

The treatment of melanoma with m-AMSA A Cancer and Leukemia Group B phase II study

The activity of m-AMSA was evaluated IN 39 patients with advanced malignant melanoma. Seventy-nine percent of the patients had some prior chemotherapy. The others had some combination of surgery, radiotherapy, and immunotherapy prior to this study. Patients were treated every 3 weeks starting with 60 or 120 mg/m2 of m-AMSA depending on the extent of prior treatment. Doses were escalated if nadir WBC counts were greater than 2500/microliter. Leukopenia was the dose-limiting toxicity with 7.5% of patients having nadir WBC counts less than 1000/microliter. Of the 39 patients evaluable for response, all had progressive disease. In this study, m-AMSA in myelosuppressive doses was not active in malignant melanoma.

High-dose cytosine arabinoside and m-AMSA is effective therapy in relapsed acute nonlymphocytic leukemia

High-dose cytosine arabinoside ( HDARAC ) and 4'-(9 acridinylamino) methane sulfon -m-anisidine (m-AMSA) was administered as induction therapy to 40 patients with relapsed or refractory acute nonlymphocytic leukemia (ANLL) with the following results: 28 patients (70%) achieved complete remission, one patient achieved a partial remission; five patients died with hypoplastic bone marrows containing less than 5% blasts; four patients died with hypoplastic marrowing containing greater than 5% blasts; and three patients failed to achieve marrow aplasia and died without significant cytoreduction in percentage of blasts. Consolidation therapy was not used and maintenance therapy was given to less than 10% (three patients) of remission patients. The median duration of remission for all patients was 6.0 months and the median time for the complete remission patients exceeded eight months. This regimen has acceptable toxicity and the results are equivalent to those obtained from conventional induction therapy of de novo ANLL patients.

Neocarzinostatin versus m-AMSA or doxorubicin in hepatocellular carcinoma

Sixty-one of 76 patients entered on a prospective randomized trial of neocarzinostatin ( NCZ ) versus m-AMSA or doxorubicin were eligible for analysis. Among these 61 patients at least one episode of severe toxicity was documented in 39% of patients on NCZ and 58% on m-AMSA. Fifty-one of the 61 patients were previously untreated with chemotherapy. Among these 51 patients objective response was documented in two of 25 patients treated with NCZ , none of 17 treated with m-AMSA, and one of nine treated with doxorubicin. Among previously untreated North American and European (NA/E) patients the median survival times were: NCZ 11 weeks and m-AMSA 12 weeks. The data on South African (SA) patients with similar entrance criteria entered on earlier Eastern Cooperative Oncology Group trials were analyzed with that from the randomized trial and show that for SA patients the median survival times were: NCZ , 11 weeks (31 patients); m-AMSA, 13 weeks (33 patients); and doxorubicin, 15 weeks (29 patients).

Metabolism of 4'-(9-acridinylamino)methanesulfon-m-anisidide by rat liver microsomes

4'-(9-Acridinylamino)methanesulfon-m-anisidide (m-AMSA) is metabolized by a hepatic microsomal enzyme system composed of rat liver microsomes, a reduced nicotinamide adenine dinucleotide phosphate-generating system, cytosolic protein (or glutathione), and oxygen. Omission of any one of the components, or incubation under an atmosphere of CO or N2, results in inhibition of the reaction. Also, the addition of inhibitors of microsomal metabolism (alpha-naphthoflavone, metyrapone, or SKF 525-A) decreases m-AMSA metabolism. Metabolism of m-AMSA is more rapid with microsomes prepared from rats pretreated with phenobarbital or 3-methylcholanthrene. Two microsomal oxidation products of m-AMSA were isolated and identified as N1'-methanesulfonyl-N4'-(9-acridinyl)-3'-methoxy-2',5'-cyclohex adiene-1', 4'-dimine (m-AQDI) and 3'-methoxy-4'-(9-acridinylamino-2',5'-cyclohexadien-1'-one (m-AQI). m-AQDI reacts with glutathione to form a product previously identified in in vivo studies as the principal rat biliary metabolite and which is not cytotoxic to cultured L1210 cells. Thus, the end result of the microsomal metabolism of m-AMSA is detoxification. However, the two primary oxidation products (m-AQDI and m-AQI) are considerably more cytotoxic to L1210 cells in vitro than is m-AMSA. The concentration of m-AMSA required to produce a 5-log kill is 1.0 microgram/ml compared to 0.01 microgram/ml for m-AQDI and m-AQI. These results indicate that m-AMSA might undergo bioactivation to form the active cytotoxic species of the drug.

Potential antitumor agents. 40. Orally active 4,5-disubstituted derivatives of amsacrine

The DNA-intercalating agent amsacrine is an effective drug for the treatment of human leukemias and lymphomas but has minimal solid tumor activity. As a first step in identifying analogues with a wider spectrum of activity, a comparison was made of the in vivo antileukemic (P-388) activity of amsacrine analogues given by oral (po) and intraperitoneal (ip) routes. A series of 4-substituted and 4,5-disubstituted derivatives all showed high activity when administered ip against ip-implanted P-388, but activity varied widely when the compounds were given orally. 4-Methoxy and 4-carbamoyl derivatives proved essentially inactive, whereas 4-methyl and 4-methylcarbamoyl derivatives retained activity. Exceptional oral activity was shown by the 4-methyl-5-methylcarbamoyl derivative, making this amsacrine derivative worthy of further testing.

Relationship between the induction of chromosome damage and cytotoxicity for amsacrine and congeners

The antitumor drug amsacrine causes chromosomal aberrations both in cultured cells (L1210 murine leukemia and HeLa cells) and in vivo (L1210 leukemia). The proportions of different types of aberrations, mainly chromatid gaps, chromatid exchanges, and acentric chromosome fragments, are similar in both the in vivo and in vitro experiments. A small proportion of cells, particularly after drug exposure for 24 hours, show extensively damaged or pulverized chromosomes. In in vitro experiments using HeLa cells and amsacrine together with two analogs of amsacrine with differing cytotoxic activity, an inverse relationship between the frequency of chromosomal aberrations and cell survival has been demonstrated. The results are consistent with the proposal that for this class of drugs, the induction of chromosomal aberrations, both in vivo and in vitro, leads to cell death.

Mechanism of antitumor drug action: poisoning of mammalian DNA topoisomerase II on DNA by 4'-(9-acridinylamino)-methanesulfon-m-anisidide

The intercalative acridine derivative 4'-(9-acridinylamino)methanesulfon-m-anisidide (m-AMSA), but not its isomer o-AMSA, is a potent antitumor drug that in mammalian cells stimulates the formation of DNA strand breaks that are characterized by tightly bound proteins. Using purified mammalian DNA topoisomerases, we have analyzed the effects of these antitumor drugs on topoisomerase-DNA interactions. The antitumor drug m-AMSA dramatically stimulates the formation of a topoisomerase II-DNA complex that is detected on protein-denaturant treatment: both single- and double-stranded DNA breaks are produced and a topoisomerase II subunit is linked covalently to each 5' end of the broken DNA strands. The noncytotoxic isomer, o-AMSA, which does not induce significant amounts of DNA breaks in cultured cells, exhibits a correspondingly smaller effect in stimulating formation of the complex in vitro. The agreement between in vitro and in vivo studies suggests that mammalian DNA topoisomerase II may be the primary target of m-AMSA and that the drug-induced complex formation between topoisomerase II and DNA may be the cause of cytotoxicity and other effects such as DNA sequence rearrangements and sister-chromatid exchange.

Differential growth inhibition of cultured mammalian cells: Comparison of clinical antitumour agents and amsacrine derivatives

The growth-inhibitory potencies in culture of a variety of clinical antitumour drugs have been compared using two widely studied cell lines: L1210 murine leukaemia and V79 Chinese hamster fibroblasts. Marked variations in the relative sensitivities of these two lines were observed with individual antimetabolites and DNA intercalating agents, while activities of alkylating agents and vinca alkaloids were similar for both cell lines. This experimental system was used to evaluate the possibility of designing intercalating drugs selective for a particular target cell. Results with derivatives of the antileukaemia agent amsacrine indicate that relative cytotoxicity can be modulated by simple monosubstitution within the 9-anilinoacridine ring system. The variation in ratios of inhibitory potencies within the latter series is similar to that observed for the structurally diverse group of clinically-utilized intercalators tested. These results suggest that amsacrine analogue development may provide agents having a different tumour spectrum and greater therapeutic utility than the parent drug.

Acridinyl anisidide (m-AMSA) therapy in 11 patients with refractory acute leukemia

Eleven patients with acute leukemia, refractory to all previous chemotherapy, were treated with acridinyl anisidide (m-AMSA). Seven patients received m-AMSA i.v. as a single agent at 150 mg/m2 daily for 4 to 7 days, and 4 patients received m-AMSA at 90 mg/m2 daily for 3 days in combination with thioguanine and cytosine arabinoside. Four of the nine patients with acute nonlymphoblastic leukemia responded to the treatment, and complete remission was obtained in three of them. One of these patients remained in complete remission 5 months after therapy. Three of the four responding patients received m-AMSA as a single agent. Two patients with resistant acute lymphoblastic leukemia did not respond. As in earlier trials with m-AMSA reported by others, about one-third of our refractory patients responded, which justifies the future use of this agent in refractory leukemia and in other regimens for the induction of remission in acute leukemia. Despite minimal cardiotoxicity of the drug, evidence of its cardiotoxic potential is recorded.

Human tissue distribution of 4'-(9-acridinylamino)-methanesulfon-m-anisidide (NSC 141549, AMSA)

Concentrations of AMSA were determined by HPLC in autopsy tissue samples from five patients who had received the drug antemortem. Relative organ concentrations of AMSA varied from patient to patient; however, concentrations were generally highest in gallbladder, liver, and kidney, while low levels were generally but not invariably found in lung, testicle, muscle, fat, spleen, bladder, pancreas, colon, prostate, and brain. One patient with ventricular fibrillation and seizures had high tissue AMSA concentrations in myocardium, but low concentrations in brain. Another patient with seizures during treatment had high brain concentrations of AMSA. Relative organ concentrations were similar to those found in mice, except that mice have high AMSA concentration in their spleens whereas our patients did not, even when the spleen was infiltrated with leukemic cells. High tissue concentrations of AMSA were still present 2 weeks after treatment. AMSA concentration was lower in a renal oncocytoma (1.1 micrograms/g) than in surrounding kidney (2.4 micrograms/g).

Prediction of complete remission in patients with refractory acute leukemia treated with AMSA

The relation between characteristics known at start of therapy and response in 102 adults with refractory acute leukemia who received 4'-(9 acridinylamino)-methane-sulfon-m-anisidide (AMSA) was examined. Twenty-three (23%) of these patients attained complete remission (CR). Univariate analysis showed that the following characteristics were associated with CR: a fewer number of prior induction and maintenance regimens, a shorter time between latest relapse and AMSA therapy, the presence of Auer rods, a circulating blast cell count of less than 25,000/mm3, a marrow cellularity less than 90%, a ratio of marrow blasts and promyelocytes to more mature myeloid cells (differentiation ratio) less than 15, and a first-course AMSA dose of greater than or equal to 375 mg/m2. Some of these factors were interrelated. Multivariate analysis using logistic regression techniques was carried out to determine which of the above factors added independent prognostic information. This analysis produced a statistical model that related probability of response to the following in order of selection: Auer rod status, first-course dose, differentiation ratio, and absolute circulating blast cell count. Such a model could be useful in identifying patients with high, intermediate, or low probability of response to AMSA. AMSA could then be prescribed only for patients likely to respond while affording other patients alternate salvage programs at an earlier time.

Primary therapy of acute promyelocytic leukemia: results of amsacrine- and daunorubicin-based therapy

Remission rates for patients with acute promyelocytic leukemia (APL) have improved with the use of anthracyclines and proper management of disseminated intravascular coagulopathy. In a prospective randomized trial of chemotherapy in patients with acute nonlymphoblastic leukemia, there were 16 patients with APL. All 7 of the patients receiving the amsacrine-containing regimen and 5 of 9 receiving the daunorubicin-containing regimen achieved a remission. All patients, except 2 of the 3 who underwent bone marrow transplantation, remain alive and in remission from 1+ to 25+ mo. Amsacrine is an effective replacement for daunorubicin in the treatment of APL, and its use does not compromise the favorable remission duration characteristic of APL.

Effectiveness of AMSA alone or in combination with radiation on murine fibrosarcoma pulmonary nodules

The cytotoxic effects in vivo of 4'-(9-acridinylamino) methanesulfon-m-anisidide (AMSA), radiation or both modalities in combination on murine fibrosarcoma (FSa) cells grown as pulmonary tumors were determined. Fourteen days following the i.v. injection of viable FSa cells, recipient mice developed between 100 and 150 visible pulmonary nodules. At that time, tumor-bearing animals were exposed to either single or combined modality treatments, as well as single and fractionated dose regimens. Animals were sacrificed 1 hour after the last treatment. Tumor nodules were excised, made into a single cell suspension and separated on the basis of cell size by centrifugal elutriation. Flow microfluorometry (FMF) was used to determine the cell-cycle parameters and the relative synchrony of the separated populations, as well as the percentage contamination by normal diploid cells in each of the tumor cell populations. Known numbers of viable cells from each elutriator fraction were injected into recipient mice to determine their colony-forming efficiency (CFE). Surviving fractions were determined by comparing the CFEs of treated FSa cells from each of the separated elutriator fractions with those of appropriate untreated controls. Following a single i.v. dose of AMSA (30 mg/kg), populations of cells enriched in S phase were the most sensitive. When a single dose of AMSA was combined with a single dose of radiation (100 rad), there was a marked schedule dependence with the more effective sequence, especially if a 12 hour interval was chosen between doses, being AMSA followed by irradiation. No schedule dependence was observed if both modalities were combined and administered under a fractionated protocol of four fractions of AMSA (5 mg/kg per fraction) and four fractions of radiation (300 rad per fraction). Under these conditions the greatest reduction in CFE was in cell subpopulations most enriched in S and G2 + M phase cells.

Intrathecally Administered m-AMSA in the Rhesus Monkey

4'-(9-Acridinylamino)-methanesulfon-m-anisidide (m-AMSA) is an acridine compound that has been found useful in the systemic treatment of acute leukemia. This paper specifically investigates the CSF pharmacokinetics of m-AMSA following both intravenous and intraventricular administration in a subhuman primate model. Following intravenous administration, m-AMSA crossed the blood-brain barrier poorly; cerebrospinal fluid (CSF) concentrations were only 1-3% of systemic concentrations. Intraventricular administration of drug achieved high initial ventricular fluid concentrations, but the drug was rapidly cleared with a half-life of 115 min. Following 500 micrograms of intraventricular drug, CSF concentrations of m-AMSA remained above 1 microM for only 6 h. These data suggest that m-AMSA has potential as an intrathecal agent against meningeal leukemia refractory to more conventional therapy, but detailed toxicology and neurohistopathology will be required before intra-CSF m-AMSA can be considered for human use.

Bacterial and mammalian cell mutagenesis, sister-chromatid exchange, and mouse lung adenoma bioassay with the antineoplastic acridine derivative amsacrine

Amsacrine is a DNA intercalating agent with antineoplastic properties in lymphoproliferative disorders. This report describes a group of short-term tests with multiple endpoints to characterize the mutagenic and carcinogenic properties of this drug. In vitro studies included bacterial and mammalian cell mutagenesis, and sister-chromatid exchange and chromosome aberrations in mammalian cells. In vivo, mice were given amsacrine for 7 wk at 2, 5, and 10 mg/kg and were observed for an additional 17 wk. The standard bacterial assay revealed cytotoxicity at 2000 and 5000 micrograms/plate in the preincubation assay. No significant increase in revertants occurred in Salmonella strains, except for TA1537 in the activation phase. Amsacrine at 4.0 micrograms/ml was cytotoxic to V-79 cells in the cell mutation assay, and at lower dose levels was a direct-acting mutagen for the HGPRT locus. Sister-chromatid exchange rate of Chinese hamster ovary cells was increased more than twofold at 2 micrograms/ml without metabolic activation. Cell anomalies included changes in metaphase cell kinetics and chromosome damage. Mice in the lung adenoma bioassay failed to show increased numbers of tumors, while indicating lack of tolerance and survival beyond 5 mg/kg. The results indicate clear genotoxicity to mammalian cell systems with a spectrum of changes from point mutation and SCE induction to cell-cycle alterations, irrespective of exogenous metabolic activation. These results corroborate previous findings in animal and human cell systems in vitro. The reduction of genotoxicity in bacterial assays after exogenous metabolic activation may suggest some detoxification, and the magnitude of effects observed in mammalian cells indicates that exogenous metabolic activation is not required to manifest amsacrine's activity. The lack of tumor-inducing potential in mice may be attributed to strong cytotoxic effects in this species, or to an insensitivity of the target organ, or to assay systems that may mask the carcinogenic potential.

AMSA: a phase II trial in resistant and recurrent acute myelogenous leukemia

27 patients with resistant acute myelogenous leukemia (AML) were treated with AMSA. Three achieved a complete remission, and two a partial remission. Median survival for all patients was 12 weeks and was 16 weeks for responders.