Bis-benzimidazole anticancer agents: targeting human tumour helicases.

Certain DNA minor groove binding agents, distamycin, netropsin, and a series of anticancer bis-benzimidazoles can block DNA helicase activity by binding to duplex DNA at specific base sequences. DNA helicases are crucial to cell DNA replication, transcription and repair because these enzymes separate double-stranded DNA, thereby preparing the strands for enzymatic manipulation. From our studies we have developed a hypothesis that focuses on cellular DNA helicase action as a mechanistic site where these minor groove binders can act.

Antihelicase action of CI-958, a new drug for prostate cancer.

CI-958, a new DNA-intercalating drug derived from a series of substituted 2H-[1] benzothiopyrano[4,3,2-cd]indazoles, is being tested in clinical trails because of its curative properties against murine solid tumor models and because it has demonstrated activity in a pilot phase II study of patients with hormone-refractory prostate cancer. However, the mechanism of anticancer action of CI-958 has not been established. Because CI-958 binds to DNA and DNA helicases are profoundly affected by DNA-binding drugs, we examined the effects of CI-958 on human DNA helicase action.

Anthracycline antibiotic blockade of SV40 T antigen helicase action.

We previously showed that anthracycline antibiotics potently block SV40 large T antigen helicase; in the present study, we describe the kinetics and the structure-activity characteristics of this process. The concentration vs effect data for helicase blockade were fitted by the Hill equation to yield nearly parallel log-concentration effect curves for a series of active anthracycline antibiotics. The effective concentration for 50% helicase blockade (EC50) values ranged from 0.

Antihelicase action of DNA-binding anticancer agents: relationship to guanosine-cytidine intercalator binding.

DNA-binding antibiotics such as intercalators, narrow groove binders, and other substances modify duplex DNA, making it an altered substrate for DNA helicases. The intercalators daunorubicin, actinomycin D, echinomycin, and elsamicin, the narrow groove binders distamycin and mithramycin, and the plant toxin teniposide, each representing a different chemical class, block SV40 large T antigen DNA helicase action with IC50 values ranging from 4 x 10(-8) to 2 x 10(-6) M. A partially purified human HeLa cell DNA helicase is also potently blocked by daunorubicin, distamycin, and teniposide.

Helicase inhibition by anthracycline anticancer agents.

Helicases are essential to both DNA replication and transcription because they separate double-stranded DNA, preparing the single strands for replication or transcription. Because the anti-cancer anthracycline antibiotics stabilize double-stranded DNA primarily by their intercalative binding, we expected the intercalated antibiotics to interfere with helicase action. We examined anthracycline antibiotic effects on SV40 large T antigen helicase activity, using a duplex DNA helicase substrate of 32P-labeled 17-mer annealed to complementary M13mp19(+) circular single-stranded DNA.

Phase I clinical and pharmacokinetic study of zeniplatin, a new platinum complex.

Forty-six patients with refractory solid malignancies received the new platinum complex [2,2-bis(aminomethyl)-1,3-propanediol-N-N'] [1,1-cyclobutanedicarboxylato] [(2-)0,0')] platinum (zeniplatin). Zeniplatin was given, without hydration or mannitol, as a 60- to 90-min i.v.

Induction of a human carbonyl reductase gene located on chromosome 21.

Carbonyl reductase (EC 1.1.1.

Experimental chemotherapy-induced skin necrosis in swine. Mechanistic studies of anthracycline antibiotic toxicity and protection with a radical dimer compound.

The reactivity of antitumor anthracycline and mitomycin C antibiotics with the oxomorpholinyl radical dimers, bi(3,5,5-trimethyl-2-oxomorpholin-3-yl) (TM3) and bi(3,5-dimethyl-5-hydroxymethyl-2-oxomorpholin-3-yl) (DHM3), was studied in vitro. The oxomorpholinyl radical reduced daunorubicin to a quinone methide intermediate that reacted with solvent to form 7-deoxydaunorubicinone. The solvolysis reaction followed first order kinetics, and the reactivity rate constants (k2) measured for seven anthracycline analogues ranged from 2 X 10(-2) s-1 to 8.

Loss of fluorescence by anthracycline antibiotics: effects of xanthine oxidase and identification of the nonfluorescent metabolites.

Rat liver cytosol and buttermilk xanthine oxidase both converted 7-deoxypyrromycinone, the 7-deoxyaglycone of marcellomycin, a new anthracycline antibiotic, to a nonfluorescent compound under anaerobic conditions and in the presence of an electron donor. Reduced nicotinamide adenine dinucleotide and reduced nicotinamide adenine dinucleotide phosphate were equally effective electron donors for liver cytosol, and xanthine was the best cofactor for xanthine oxidase. However, xanthine was inactive with liver cytosol.

DNA alkylation by enzyme-activated mitomycin C.

After anaerobic reductive activation by either NADPH cytochrome P-450 reductase (EC 1.6.2.

Comparative anthracycline metabolism in rats: loss of marcellomycin fluorescence.

The in vitro metabolism of marcellomycin by rat tissue fractions showed conversion of marcellomycin to 7-deoxypyrromycinone, bisanhydropyrromycinone, and an as yet unidentified compound by rat liver homogenate, microsomes, cytosol, and mitochondria, and purified hepatic reduced nicotinamide adenine dinucleotide phosphate-cytochrome P-450 reductase, under anaerobic conditions and in the presence of reduced nicotinamide adenine dinucleotide phosphate. All these fractions except the purified reductase subsequently induced a progressive loss of fluorescence. Mitochondria, however, were much less active than microsomes, cytosol, and homogenate in inducing this latter phenomenon.

Effect of hyperthermia on the in vitro metabolism of doxorubicin.

The effect of hyperthermia on the uptake and metabolism of doxorubicin (ADM) was studied in in vitro systems. ADM uptake in rat liver slices was not affected by increasing the temperature from 37 degrees C to 43 degrees C. In rat liver homogenates, the aerobic transformation of ADM was low and was not affected by hyperthermia.

Interactions between cyclophosphamide and doxorubicin metabolism in rats. II. Effect of cyclophosphamide on the aldoketoreductase system.

Under anaerobic conditions, in comparison to liver microsomes obtained from normal controls, liver microsomes obtained from rats pretreated with cyclophosphamide formed significantly less 7-deoxydoxorubicinol aglycone (P less than or equal to .05), whereas the disappearance of doxorubicin and the formation of 7-deoxydoxorubicin aglycone were unaffected. When directly investigated, the reduction of 7-deoxydoxorubicin aglycone to 7-deoxydoxorubicinol aglycone by microsomes was inhibited by cyclophosphamide pretreatment.

Doxorubicin-induced skin necrosis in the swine model: protection with a novel radical dimer.

The treatment of doxorubicin (DOX) extravasation tissue injury is poorly defined. A swine model has been developed to study DOX skin toxicity and potential pharmacologic antidotes. Intradermal injections of DOX in miniature female weanling swine produced predictable and dose-dependent ulcerations that closely resemble lesions observed in humans following extravasation of DOX.

Cellular pharmacology and antitumor activity of N-(p-azidobenzoyl)-daunorubicin, a photoactive anthracycline analogue.

We have previously utilized N-(p-azidobenzoyl)daunorubicin (NABD), a photoactive analogue of daunorubicin (DNR), to identify unique anthracycline-binding polypeptides in rodent tissues and in tumor cells. Using cultured P388 tumor cells, we have now compared the cellular pharmacology and antitumor activity of NABD with that of DNR. Although rapidly accumulated by cells, the intracellular concentration of NABD was less than 20% that of DNR at steady-state levels.

Doxorubicin and cisplatin excretion into human milk.

Plasma and milk concentrations of doxorubicin (DOX) and cisplatin were measured after iv administration of these agents to a lactating patient with ovarian cancer. Cisplatin was undetectable in human milk. Milk concentrations of DOX often exceeded those detected in concomitant plasma samples.

Radical dimer rescue of toxicity and improved therapeutic index of adriamycin in tumor-bearing mice.

The product of adriamycin (ADR) reductive glycosidic cleavage is the pharmacologically inactive 7-deoxyadriamycin aglycone. Bi(3,5-dimethyl-5-hydroxymethyl-2-oxomorpholin-3-yl) (DHM3) is a radical dimer which reacts with ADR in vitro to produce this aglycone. We utilized DHM3 to prevent ADR toxicity in mice.

Metabolism and disposition of menogaril (NSC 269148) in the rabbit.

We have investigated the metabolism and disposition, in rabbits, of menogaril (7-OMEN), a new anthracycline antibiotic recently introduced into clinical trials. 7-OMEN was administered by rapid i.v.

Deoxyguanosine enhancement of cytarabine nucleotide accumulation in human leukemia cells.

We studied the effect of deoxyguanosine (dGuo) on cellular cytarabine (ara-C) nucleotide accumulation of the human leukemia cell line K562 and of bone marrow blast cells derived from patients with acute nonlymphocytic leukemia. Exposure of cells in culture to dGuo increased ara-C nucleotide accumulation measured in cell lysate, with an average increase of 386% (range, 242%-537%) of control in the presence of 500 microM dGuo. Maximal elevation occurred after 8 hours of exposure and remained constant through 48 hours.

Electron spin resonance of electrochemically generated free radicals from diaziquone and its derivatives.

The one-electron electrochemical reduction of diaziquone (AZQ) and 12 analogs is analyzed using ESR spectroscopy and cyclic voltammetry. The hyperfine coupling constants arising from the interaction of the unpaired electron with the aziridine nitrogen nuclei fall within 1.20 and 2.

Cellular activation of diaziquone [2,5-diaziridinyl-3,6-bis (carboethoxyamino)-1,4-benzoquinone] to its free radical species.

Human leukemic cell lines K562 and HL60, and the murine leukemic cell line L1210, reduce Diaziquone (AZQ) (NCS182986) to its free radical anion. With all cell lines, the free radical was observed immediately in both aerobic and anaerobic cell suspensions. The steady-state concentration of AZQ free radicals was approximately 1% of the total AZQ concentration.

Cellular pharmacology in murine and human leukemic cell lines of diaziquone (NSC 182986).

We investigated the in vitro interaction with and antitumor effect on several murine and human leukemic cell lines of diaziquone (AZQ). L1210 cells accumulated AZQ from Roswell Park Memorial Institute Medium 1640 with or without newborn calf serum by a temperature-dependent and sodium azide-resistant process. AZQ inhibited, in a dose-dependent fashion, [3H]thymidine incorporation into L1210 cells, but this inhibition was slow to develop, requiring approximately 6 hr to become apparent.