Effects of polyamines on the DNA-reactive properties of dimeric mithramycin complexed with cobalt(II): implications for anticancer therapy.

Few studies have examined the effects of polyamines on the action of DNA-binding anticancer drugs. Here, a Co(II)-mediated dimeric mithramycin (Mith) complex, (Mith)(2)-Co(II), was shown to be resistant to polyamine competition toward the divalent metal ion when compared to the Fe(II)-mediated drug complexes. Surface plasmon resonance experiments demonstrated that polyamines interfered with the binding capacity and association rates of (Mith)(2)-Co(II) binding to DNA duplexes, while the dissociation rates were not affected. Although (Mith)(2)-Co(II) exhibited the highest oxidative activity under physiological conditions (pH 7.3 and 37 degrees C), polyamines (spermine in particular) inhibited the DNA cleavage activity of the (Mith)(2)-Co(II) in a concentration-dependent manner. Depletion of intracellular polyamines by methylglyoxal bis(guanylhydrazone) (MGBG) enhanced the sensitivity of A549 lung cancer cells to (Mith)(2)-Co(II), most likely due to the decreased intracellular effect of polyamines on the action of (Mith)(2)-Co(II). Our study suggests a novel method for enhancing the anticancer activity of DNA-binding metalloantibiotics through polyamine depletion.

Effect of mitoguazone on polyamine oxidase activity in rat liver.

Mitoguazone is a known inhibitor of polyamine biosynthesis through competitive inhibition of S-adenosylmethionine decarboxylase. A recent renewed interest in mitoguazone as an antineoplastic agent prompted us to investigate the effect of the drug on polyamine catabolism in rat liver, since the organ plays an important role in detoxification mechanisms. Thus, the purpose of this work was to evaluate the effect of in vivo mitoguazone administration on polyamine catabolic enzymes. In particular, our interest was directed to the changes in polyamine oxidase activity, since this enzyme has been recently confirmed to exert important functions that until now were underestimated. Mitoguazone administration induced hepatic polyamine oxidase activity starting at 4 h after administration, and the enzyme returned to basal levels 96 h after treatment. The changes in enzyme activity were accompanied by changes in putrescine concentrations, which increased starting at 4 h until 72 h after treatment. We also evaluated the activity of the newly identified spermine oxidase, which was not significantly changed by mitoguazone treatment. Therefore, we hypothesized that the enzyme involved in mitoguazone response of the liver is the polyamine oxidase, which acts on acetylated polyamines as substrate.

Synergistic effect of sequential administration of mitoguazone (MGBG) and gemcitabine in treating tissue cultured human breast cancer cells and mammary rat tumors.

Modulation of cancer chemotherapeutic drugs has been attempted to increase efficacy and overcome resistance to the chemotherapeutic agent. Studies have shown schedule-dependent interactions in combined use of chemotherapeutic drugs. Mitoguazone (MGBG), an old drug with possible modulating activity, was used in combination with gemcitabine, a relatively new cancer drug, in treating tissue cultured human breast cancer cells and mammary rat tumors. Tissue cultured BOT-2 cancer cells were first treated with varying concentrations of gemcitabine and MGBG, independently. Combinations of the two drugs were then used with different scheduled administrations. Marked synergistic activity was found between gemcitabine and MGBG when the MGBG was given first, followed by gemcitabine 24 hours later. A non-toxic dose of MGBG enhanced the toxicity of gemcitabine by eight orders of magnitude using MTT assays in the tissue cultured human breast cancer cell study. The sequential administration of MGBG and gemcitabine also increased the survival rate of rats bearing mammary tumors in our pilot animal study.

Cellular pharmacodynamics of the cytotoxic guanidino-containing drug CHS 828. Comparison with methylglyoxal-bis(guanylhydrazone).

N-(6-(4-chlorophenoxy)hexyl)-N'-cyano-N"-4-pyridylguanidine (CHS 828) is a new guanidino-containing compound with antitumoral activity both in vitro and in vivo. Its activity profile differs from those of standard cytotoxic drugs but the mechanism of action is not yet fully understood. CHS 828 is presently in early phase I and II clinical trials. In the present study, the pharmacodynamic effects at the cellular level of CHS 828 was compared to another compound containing two guanidino groups, methylglyoxal-bis(guanylhydrazone) (MGBG). MGBG is known to inhibit the synthesis of polyamines, which are important in, e.g., proliferation and macromolecular synthesis. The concentration-response relationship of CHS 828 closely resembled that of MGBG and the drugs were similar with respect to inhibition of DNA and protein synthesis. On the other hand, CHS 828 induced a significant increase in cellular metabolism while MGBG did not. The cytotoxic effect of MGBG was reversed by the addition of exogenous polyamines, while that of CHS 828 was unaffected. Unlike MGBG, there was also no effect of CHS 828 on the levels of decarboxylating enzymes in the polyamine biosynthesis. In conclusion, CHS 828 does not appear to share any major mechanisms of action with the polyamine synthesis inhibitor MGBG. Further studies will be required to define the exact mechanism of action of CHS 828.

In vitro cytotoxicity of guanylhydrazones (MGBG and PGBG) on cultured Chinese hamster ovary cells.

Guanylhydrazones, methylglyoxal bis(guanylhydrazone) (MGBG) and a new compound, phenylglyoxal bis(guanylhydrazone) (PGBG), interfering with polyamine biosynthesis have considerable potential for the use as antiparasitic and antitumor agents. The effect of these drugs on the cellular viability of Chinese hamster ovary cells was examined by in vitro neutral red assay. The time exposure and metabolic influence was studied. These compounds have a dose- and time-dependent cytotoxicity. The IC50 values were of 597.22 micrograms/ml and 1.77 micrograms/ml for MGBG after 3 and 24 h of incubation, respectively, and 380.50 micrograms/ml for PGBG after 24 h of incubation. The PGBG treatment during 3 h had no cytotoxic effect when the concentrations were lower than 3000 micrograms/ml. With the cytotoxicity assay used, we observed that the presence of S9 in cultured medium did not influence the cytotoxicity of these compounds.

Methylglyoxal bis (cyclopentylamidinohydrazone) (MGBCP): antitumor effect against human osteosarcoma cells and combined effect with methotrexate, adriamycin and 4-hydroperoxyifosfamide.

The antitumor effect of a polyamine biosynthetic pathway inhibitor methylglyoxal bis(cyclopentylamidinohydrazone) (MGBCP) on human osteosarcoma cell lines such as KHOS-240S, MG-63 and G-292 cells, and its effect in combination with anticancer drugs such as methotrexate (MTX), adriamycin (ADM) and 4-hydroperoxyfosfamide (HIFO) have been investigated. The growth of these cultured osteosarcoma cells was inhibited by MGBCP in a dose-dependent manner. Spermidine and spermine levels were dose-dependently depressed in these MGBCP-treated osteosarcoma cells. The antitumor effect of MGBCP was additively potentiated by combined treatment with MTX, ADM and HIFO, respectively.

Dioxopiperazine derivative potentiates antitumor effect of methylglyoxal bis(cyclopentylamidinohydrazone) on human and mouse leukemia cells.

Antiproliferative effects of 1,1'-ethylenedi-4-isobutoxy-carbonyloxymethyl-3,5-d iox opiperazine (MST-16), an inhibitor of topoisomerase II, in combination with methylglyoxal bis (cyclopentylamidinohydrazone) (MGBCP), an inhibitor for polyamine biosynthetic enzymes, were investigated using cultured human lymphoid cells and leukemic mice. The combined treatment of human Molt 4B lymphoid cells with MST-16 and MGBCP resulted in greater suppressions of cellular polyamine and protein biosyntheses and decrease of cell number than in the cells treated with either drug alone. Inhibition of macromolecule biosyntheses by MGBCP was additively potentiated by simultaneous treatment with MST-16. In vivo experiments, the combination of MST-16 and MGBCP markedly prolonged the survival time of mice bearing P388 or L1210 leukemia. These results suggest that good antitumor activity of combined treatment with MST-16 and MGBCP resulted from the diminution of DNA condensation and cellular proliferation caused by inhibition of topoisomerase II with MST-16 and by polyamine depletion with MGBCP.

[Antineoplastic activity and toxicity of dihydroambazone in comparison with ambazone (1,4-benzoquinone-guanylhydrazone-thiosemicarbazone)]. / Antineoplastische Wirksamkeit und Toxizität von Dihydroambazon im Vergleich zu Ambazon (1,4-Benzochinon-guanylhydrazon-thiosemicarbazon).

Dihydroambazone 1, a soluble derivative of ambazone, was tested with an admixture of ascorbic acid (0.1, 0.25, or 0.5% in distilled water) for antineoplastic activity by different routes (i.p., p.o., s.c., i.v.) against leukemia P388, and by s.c. application against Lewis lung carcinoma on B6D2F1-mice. The results were compared with that of ambazone. 1 was as active as ambazone upon the per os d 1-4 schedule only. Ascorbic acid, added for stabilization of 1, had no significant influence on the results. Intravenously given 1 was of low activity. It proved to be toxic at 100 mg/kg body mass. The i.v. toxicity was estimated approximately on B6D2F1-mice (LD50: 150 mg/kg; LD100: 175 mg/kg; maximum tolerated dose (MTD): 100 mg/kg. A comparison between the MTD's of 1 and ambazone in mice and rats (Wistar) showed partly a somewhat better p.o. compatibility of 1. The expectation of a favourable i.v. applicable derivative from the otherwise in water nearly insoluble ambazone could not be realized.

Influence of age on antileukemic action, subacute toxicity and tissue distribution of ambazone in B6D2F1 mice.

The influence of age of experimental animals on the antileukemic activity, toxicity and distribution of ambazone, a new potential antineoplastic agent, was studied in 2- and 12-month-old B6D2F1 mice. The predominant effect observed was a significant reduction of the antileukemic action of this compound in old-aged mice. Together with a slight increase in several toxicity parameters this caused a marked reduction of the therapeutic index in 12-month-old mice compared to younger individuals. Furthermore, a general tendency to increased ambazone levels in liver, kidneys and thymus of old-aged mice was observed. Our data therefore provide further evidence that age has to be taken into consideration as one factor that may account for the variety of drug response frequently observed during clinical therapy with anticancer agents.

Phase II trial of methylglyoxal bis-guanylhydrazone (MGBG) in refractory small cell lung cancer.

Methylglyoxal bis-guanylhydrazone (MGBG), a potent inhibitor of polyamine synthesis, has demonstrated single agent activity against a number of tumor types including malignant lymphomas and head and neck, esophageal and non-small cell lung cancers. The growth of small cell lung cancer (SCLC) cell lines can be arrested by polyamine inhibition. Therefore a phase II trial was conducted in twenty-four patients with refractory SCLC. MGBG was administered by intravenous infusion at a dose of 500 mg/m2 per week for four cycles and then every two weeks thereafter. The dose was escalated by 100 mg/m2 every two weeks in the absence of toxicity greater than or equal to grade 2. One patient achieved a partial response of objectively measurable lung disease and supraclavicular adenopathy. Three patients had stable disease. Dose limiting toxicity consisted primarily of mild to moderate nausea, vomiting, stomatitis and/or diarrhea. Myelosuppression was uncommon and rarely dose limiting. We conclude that MGBG in the dose and schedule used does not have significant activity as a single agent in previously treated small cell lung cancer.

[Mitoguazone (methylglyoxal bis(guanylhydrazone))--its status and prospects]. / Mitoguazon (Methylglyoxal-bis-guanylhydrazon)--Stand und Perspektiven.

Because of its severe side effects, initial clinical trials of the antineoplastic compound mitoguazone (Methyl-GAG, M-G) were ceased in the middle of 1960s. One decade later pharmacokinetically guided dose schedules as well as new experimental data on the antiproliferative mechanism of action stimulated new clinical studies. First results indicated that M-G had single-agent activity against various tumors such as acute leukemia and malignant lymphoma connected with acceptable tolerance. M-G seems to be effective especially in combination with other antineoplastic drugs. Its final evaluation may be reserved to further randomized trials. Recently, the psoriasis vulgaris is expected to be an additional field of the application of M-G. In this minireview data on synthesis, preclinical pharmacology, pharmacokinetics, biochemical effects and toxicology of M-G are given. Furthermore, clinical findings on M-G concerning its pharmacokinetic behaviour, antitumor and antipsoriatic activities are described.

Liposomes as carrier of methyl-GAG. Increased antitumor activity and reduced hypoglycemia in mice.

The encapsulation efficiency and the leakage on storage of various types of liposomes prepared from different lipid compositions containing the anticancer drug methyl-GAG (methylglyoxal-bis-guanylhydrazone) were investigated. Treatment with methyl-GAG in a q.d. 1-4 schedule resulted in the murine leukemias P 388 and L 1210 (i.v.) in nearly the same increase in life span as the corresponding dose in liposomes. In a q.d. 1, 3 schedule methyl-GAG containing liposomes revealed comparable effects as the 4-day treatment with the free drug. The hypoglycemic effect of 80 mg/kg methyl-GAG, q.d. 1-4, could be normalized when the drug was administered in reverse-phase evaporation vesicles. We conclude that the liposomal encapsulation of methyl-GAG leads to a depot effect with a slight relief of toxicity.

Phase II trial of methylglyoxal bis (guanylhydrazone) (MGBG) in advanced head and neck cancer.

Methylglyoxal bis (guanylhydrazone) (MGBG) is an inhibitor of polyamine synthesis. In vitro studies demonstrate the accumulation of some tumor cells in S and G2 phases of the cell cycle. Nineteen patients with advanced head and neck cancer were entered in a Phase II trial of MGBG. MGBG, 500 mg/M2, was administered as a brief intravenous infusion weekly for 4 weeks, then every 2 weeks. Dose modifications were based on cumulative toxicity after 2 weekly treatments. All but three patients had prior exposure to chemotherapy for disease recurrence. Of 17 patients evaluable for response and toxicity, one brief partial response was observed. The most common toxicities were mild to moderate nausea, vomiting, diarrhea, and stomatitis. Myelosuppression occurred in three patients. Dose modifications were required in four patients; a maximum dose of 700 mg/M2 was tolerated. The results of four other Phase II single and combination chemotherapy trials of MGBG in head and neck cancer are reviewed. The single agent response rate in 59 patients was 22% (range, 6%-41%). The poor response rate observed in this trial was similar to that in other trials in which a heavily pretreated group of patients was evaluated. It is concluded that single agent MGBG is not a useful drug in heavily pretreated recurrent disease patients. However, because of its biochemical effects, further testing in combination with cycle specific agents and in larger numbers of patients with minimal prior treatment may be warranted.

Biochemical properties and crystal structure of ethylmethylglyoxal bis(guanylhydrazone) sulfate--an extremely powerful novel inhibitor of adenosylmethionine decarboxylase.

Ethylmethylglyoxal bis(guanylhydrazone) (EMGBG) sulfate, an analog of the well-known anti-leukemic drug methylglyoxal bis(guanylhydrazone), was synthesized. It was shown to be an extremely powerful competitive inhibitor of eukaryotic S-adenosylmethionine decarboxylase, with an apparent Ki value 12 nM. Thus, it appears to be the most powerful known inhibitor of the enzyme, being almost an order of magnitude more powerful than the corresponding ethylglyoxal derivative. It neither inhibited the proliferation of mouse L1210 leukemia cells in vitro, nor did it potentiate the growth inhibition produced by alpha-difluoromethyl ornithine. In this respect, its properties are closely related to those of dimethylglyoxal, ethylglyoxal and propylglyoxal bis(guanylhydrazones), while in striking contrast to those of the antiproliferative glyoxal and methylglyoxal analogs. EMGBG also inhibited intestinal diamine oxidase activity (Ki 0.7 microM). EMGBG sulfate was crystallized from water, giving orthorhombic crystals (space group Pbcn). Their crystal and molecular structure was determined by X-ray diffraction methods. The carbon-nitrogen double bonds between the ethylmethylglyoxal part and the aminoguanidine moieties were found to have the same configuration as they are known to have in the salts of glyoxal, methylglyoxal and propylglyoxal bis(guanylhydrazones). The glyoxal bis(guanylhydrazone) chain of the EMGBG cation deviated strongly from planarity, thus differing dramatically from the corresponding chains of the glyoxal, methylglyoxal and propylglyoxal analogs.

Some aspects of clearance of mitoguazone in cancer patients and experimental cancer models.

Mitoguazone (methylglyoxal-bis(guanyl-hydrazone), MGBG) was studied by its first-pass mechanism in both cancer patients and experimental cancer models. It appears from the study that 90% of MGBG is cleared from the plasma within minutes. 24-h recovery in the urine, however, did not exceed 16% so that 84% of the drug seems to be bound to subcellular compartments. Tissue levels of MGBG in the normal prostate ranged higher than in experimental prostate cancer type 3327 M/G, i.e. enhanced clearance from cancer tissues: polyamine biosynthetic enzymes ornithine decarboxylase as well as S-adenosylmethionine decarboxylase are contrarily affected by MGBG.

Chemotherapy of subcutaneous and intracranial human medulloblastoma xenografts in athymic nude mice.

The continuous human medulloblastoma cell line TE-671 was grown as s.c. and intracranial xenografts in athymic nude mice. Tumor-bearing animals were treated with chemotherapeutic agents at the 10% lethal dose; s.c. xenografts were sensitive to melphalan, 1-(2-chloroethyl)-3-(2,6-dioxo-1-piperidyl)-1-nitrosourea, and 5-azacytidine. No consistent response could be demonstrated to 9-beta-D-arabinofuranosyl-2-fluoroadenine 5'-monophosphate, and no response to methylglyoxal bis(guanyl hydrazone), N-trifluoroacetyl adriamycin-14-valerate, or to 1-beta-D-arabinofuranosylcytosine was observed. Melphalan produced a significant (P = less than or equal to 0.007) increase in the median survival of mice bearing intracranial xenografts, whereas no response was seen to 1-(2-chloroethyl)-3-(2,6-dioxo-1-piperidyl)-1-nitrosourea or 5-azacytidine. This model will allow analysis of the chemotherapeutic profile of human medulloblastoma, and provides a means to differentiate cellular sensitivity and resistance from drug access to the intracranial site.

Effects of alpha-difluoromethylornithine and methylglyoxal bis(guanylhydrazone) on the growth of experimental renal adenocarcinoma in mice.

alpha-Difluoromethylornithine (DFMO) and methylglyoxal bis-(guanylhydrazone) (MGBG) were tested against a murine renal adenocarcinoma, because polyamines are necessary for neoplastic cell growth and because human renal adenocarcinomas contain higher levels of spermidine than do normal renal cells; MGBG inhibits spermidine synthesis and has some activity against human renal tumors; DFMO irreversibly inhibits ornithine decarboxylase, the first rate-limiting enzyme controlling polyamine biosynthesis; and DFMO promotes intracellular accumulation of MGBG in experimental tumor models and human leukemia. DFMO (2%) in drinking water, MGBG (15 mg/kg i.p.), or a combination of DFMO and MGBG was administered daily to BALB/c mice (n = 80) with intrarenal transplants of renal adenocarcinoma cells. At 28 days, renal carcinomas weighed 64 and 73% less, respectively, in DFMO- and DFMO-MGBG-treated mice than in control animals (p less than 0.01). MGBG alone had no antigrowth effect. DFMO-MGBG reduced the total metastatic index (total number of metastases/total number of animals) to 1.2 versus 3.6 in control animals (p less than 0.01) and increased survival by 12.3 +/- 1.5 (S.E.) days, from 30.8 to 42.5 days (p less than 0.05). Compared with control, DFMO-, or MGBG-treated animals, DFMO-MGBG exposure reduced tumor growth and the number of metastases, prevented metastases in some animals (47%), and increased survival of mice bearing renal adenocarcinomas. DFMO also appeared to selectively increase the uptake of [14C]MGBG by tumor tissue, which may help to explain the enhanced synergistic antigrowth effect of DFMO and MGBG against this murine renal adenocarcinoma.

Analysis of methylglyoxal bis(guanylhydrazone)-induced alterations of hamster tumor mitochondria by correlated studies of selective rhodamine binding, ultrastructural damage, DNA replication, and reversibility.

Because of the renewed importance of methylglyoxal bis(guanylhydrazone) (MGBG) in recent clinical trials for a variety of cancers, and because the antiproliferative activity of MGBG cannot be accounted for exclusively by the known inhibition by the drug of polyamine biosynthesis, but is thought to involve an alternative action in which the mitochondria are implicated, we have investigated several new aspects of the nature and reversibility of this mitochondrial damage. Using Rous sarcoma hamster tumor cells as a model, treatment of monolayer cultures during exponential growth with 10, 25, and 50 microM MGBG (up to 48 hr) resulted in dose-dependent (reversible) growth inhibition and selective ultrastructural damage to the mitochondria (e.g., extreme swelling, loss of cristae and matrix components, and dense inclusions) in up to 96% of cells, while nuclei appeared normal, corroborating and extending findings by others in mouse, rat, and human cells. Mitochondria in 3 to 5% of cells failed to swell, even at highest drug dosage, but were of unusual structure. After removal of MGBG, damaged mitochondria in 90 to 95% of cells recovered near-normal ultrastructure within 1 to 2 days; in some cells, mitochondrial recovery from severe damage could be monitored following a lag period of up to 5 days. The potential-dependent, supravital fluorescent probe rhodamine 123 (RH 123) selectively and relatively uniformly stained the grossly enlarged mitochondria, strikingly delineating residual organelle membranes. Quantitative assays of the uptake and retention of RH 123/10(6) cells demonstrated the maintenance of mitochondrial membrane potential in both control and MGBG-treated cell populations. These data also support the concept of mitochondrial fusion in MGBG-treated cells. The fate of mitochondrial DNA (mtDNA) both during (24 to 48 hr) and following (7 hr to 7 days) MGBG treatment was monitored by ultrastructural, electron autoradiographic, pulse-labeling, gradient centrifugation, restriction cleavage, and electrophoretic methods. MGBG treatment (50 microM; 7 and 16 hr) selectively inhibited mtDNA replication (73% at 16 hr) prior to significant inhibition of nuclear DNA synthesis (19% at 16 hr); the drug induced structural alterations, without substantial degradation, of the closed circular (major form) of mtDNA, and cessation of D-loop strand (7S) initiation within the replication origin. Upon return to drug-free medium, mtDNA resumed replicative activity, and mtDNA fibrils appeared to be associated with regenerating cristae, as assessed by electron microscopy. The combined results demonstrate mitochondria to be a selective target of MGBG action, and define structu

Trypanocidal 1,3-arylene diketone bis(guanylhydrazone)s. Structure-activity relationships among substituted and heterocyclic analogues.

Based on the antitrypanosomal activity of 1,3-diacetylbenzene bis(guanylhydrazone) (4) and 2,6-diacetylpyridine bis(guanylhydrazone) (17), a number of substituted and heterocyclic 1,3-arylene diketone bis(guanylhydrazone)s were prepared and tested against Trypanosoma brucei infections in mice. A wide range of ED50 values was observed among 5-substituted derivatives of 4. The 5-amino analogue 5 and 5-acetamido analogue 6 were about twice as active as 4. 1,3,5-Triacetylbenzene tris(guanylhydrazone) (12) was about 9 times as active as 4 and was approximately one-half as active as the currently used trypanocide diminazene aceturate in this test system. Other 5-derivatives had activity equivalent to or less than that of the parent compound 4. Three new heterocyclic analogues were all less active than 2,6-diacetylpyridine derivative 17 and benzene derivative 4. Ring substitution ortho to the guanylhydrazone side chains was invariably detrimental to activity. Side-chain homologues 1,3-dipentanoylbenzene bis(guanylhydrazone) and 1,3-diacetylbenzene bis(2-imidazolin-2-ylhydrazone) were essentially inactive.

Antigrowth effect of polyamine biosynthesis inhibitors on the Dunning R 3327-G prostatic tumor.

alpha-Difluoromethylornithine (DFMO) and methylglyoxal-bis-guanylhydrazone (MGBG), when administered simultaneously, inhibited growth and were highly toxic to the Dunning R 3327-G hormone-resistant prostatic adenocarcinoma transplanted into Copenhagen rats. Neither DFMO (2%) nor MGBG at a nontoxic dose (15 mg/kg) inhibited tumor growth, but total (47% early cure rate) or near total suppression of growth of established tumors was observed in rats receiving both treatments.