vitamin-k-semiquinone-radical and Carcinoma-256--Walker

The enzyme DT diaphorase (NAD(P)H dehydrogenase (quinone), EC 1.6.99.2) is unusual in that it can utilize either NADH or NADPH as a co-factor for the reduction of its substrates. We have shown that the intact NAD(P)H molecule is not required and that other reduced pyridinium compounds can also act as co-factors for DT diaphorase. The entire adenine dinucleotide portion of NAD(P)H can be dispensed with entirely and the simplest quaternary (and therefore reducible) derivative of nicotinamide, 1-methylnicotinamide, was as effective as NAD(P)H as a co-factor for the reduction of the quinone, menadione. Nicotinamide 5'-O-benzoyl riboside was also as effective a co-factor as NAD(P)H, whilst nicotinamide ribotide and riboside have a higher Km, and decreased the kcat of DT diaphorase. Nicotinic acid derivatives had little activity. Kinetic analysis indicated that both nicotinamide ribotide and riboside may be interacting with the menadione binding site rather than the NAD(P)H site. Irrespective of the differences between the various reduced pyridinium derivatives in their ability to act as co-factors for the reduction of menadione by DT diaphorase, all the compounds that showed activity in this assay were equally effective co-factors for the reduction of the nitrobenzamide, CB 1954 (5-(aziridin-1-yl)-2,4-dinitrobenzamide). The apparent Km of DT diaphorase for all these co-factors approached zero. It was concluded that co-factor binding is not a rate-limiting step in the nitroreductase activity of DT diaphorase.

Topics: Animals; Aziridines; Carcinoma 256, Walker; Coenzymes; Kinetics; NAD(P)H Dehydrogenase (Quinone); NADP; Niacinamide; Nicotinamide Mononucleotide; Oxidation-Reduction; Pyridinium Compounds; Rats; Structure-Activity Relationship; Vitamin K

EO9 [3-hydroxymethyl-5-aziridinyl-1-methyl-2-(H-indole-4, 7-indione)-propenol] is a novel indoloquinone structurally related to mitomycin C, a quinone anticancer drug that requires reductive bioactivation. NAD(P)H: (quinone-acceptor) oxidoreductase (quinone reductase, DT-diaphorase, EC 1.6.99.2) is an obligate 2-electron donating enzyme that can reduce a variety of quinones resulting either in bioactivation or bioprotection. Using quinone reductase (QR) preparations from rat Walker 256 mammary tumor cells and human HT29 colon carcinoma cells, we have characterized the role of this enzyme in EO9 reductive metabolism. QR activity was assayed under optimal conditions by following cytochrome c reduction at 550 nm in the presence of enzyme, quinone substrate, NADH, and bovine albumin, and confirmed by loss of EO9 absorbance at 550 nm. Both the rat and human tumor cell enzymes catalyzed reduction of the benchmark quinone menadione with a similar Km of 1.4-3.1 microM, although the Vmax was 7 to 8-fold lower for the human preparation. EO9 was readily reduced by the rat Walker QR. The mean Km was about 5-fold higher than for menadione at around 15 microM and the Vmax was 6-fold lower at around 2.5 mumol of cytochrome c reduced mg-1 of protein. EO9 was also metabolized by QR from HT29 human colon carcinoma cells but rather less efficiently than by the rat tumor enzyme. For example, the rate was 6-fold lower than that for the Walker tumor enzyme at 100 microM substrate concentration after correcting for the 7- to 8-fold difference in specific activity for the two preparations.(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: Animals; Antineoplastic Agents; Aziridines; Biotransformation; Carcinoma 256, Walker; Colonic Neoplasms; Dicumarol; DNA Damage; DNA, Bacterial; Humans; Indolequinones; Indoles; Kinetics; Mitomycin; Mitomycins; NAD(P)H Dehydrogenase (Quinone); Oxidation-Reduction; Quinone Reductases; Quinones; Rats; Superoxide Dismutase; Tumor Cells, Cultured; Vitamin K

In vivo synergy was demonstrated with vitamin K3 (menadione) and methotrexate in rats bearing the Walker 256 im carcinosarcoma, without concomitant increase in toxicity. Synergy is defined as a combined antitumor effect which exceeds the sum of the individual antitumor effects. It is suggested that such synergy, extended to human neoplasms, may significantly increase the effectiveness of methotrexate as a chemotherapeutic agent.

Topics: Animals; Body Weight; Carcinoma 256, Walker; Dose-Response Relationship, Drug; Drug Evaluation, Preclinical; Drug Synergism; Methotrexate; Rats; Vitamin K; Vitamin K 3

Cultured rat lung fibroblasts (F-cells) and Walker rat carcinoma cells (WRC-cells) labeled with 51Cr were exposed to the following antitumor drugs alone or with O3: carmustine (BCNU), doxorubicin (Dox), cisplatin (CPt), mitomycin C (Mit C) or vitamin K3 (Vit K). Release of 51Cr (cell injury) was greater for F-cells than WRC-cells with any single treatment. Pretreatment with any drug (400 microM), except for Vit K with WRC-cells, did not significantly increase O3-induced loss of 51Cr. Co-exposure of F-cells to drugs and O3 resulted in a marked potentiation of O3-induced injury with Vit K, and an inhibition with Dox.

Topics: Animals; Antineoplastic Agents; Carcinoma 256, Walker; Cells, Cultured; Chromium Radioisotopes; Fibroblasts; Ozone; Rats; Vitamin K

Topics: Animals; Blood Coagulation; Blood Coagulation Factors; Carcinoma 256, Walker; Drug Tolerance; Factor VII; Factor X; Male; Prothrombin; Rats; Rats, Inbred Strains; Turpentine; Vitamin K; Warfarin

An attempt has been made to develop tritiated derivatives of Synkavit (menadiol sodium diphosphate, MNDP) of high specific activity as a radioactive drug.This paper summarizes the preliminary biological and physical studies, with emphasis on approximate radiation dosimetry and the necessary preliminary testing, and then gives an account of the clinical investigations and the trials carried out so far, which correspond essentially to Phases I and II trials for a chemotherapeutic agent.In all, 214 patients with different sites and types of advanced and recurrent, inoperable, histologically verified malignant tumours including reticuloses have been treated with doses of at least 1 Ci of the various preparations. Among the 203 evaluable treated cases, some form of response was observed in 23 out of 151 (15·2%) receiving the drug by intravenous injections and 13 out of 52 (25%) after intra-arterial injections. For the sites and types of malignant diseases which showed responses after either intravenous or intra-arterial administration among the 55 patients surviving at least 3 months after the first injection, some form of response was observed in 32 but only 5 of these showed either a "complete" or a "partial" response.It is concluded that further investigation is desirable. It is suggested that clinical trials with randomization should be carried out for inoperable cases of carcinoma of the colon and of the pancreas.

Topics: Adult; Aged; Animals; Breast Neoplasms; Carcinoma 256, Walker; Colonic Neoplasms; Culture Techniques; Dose-Response Relationship, Radiation; Female; Half-Life; Hodgkin Disease; Humans; Injections, Intra-Arterial; Injections, Intraperitoneal; Injections, Intravenous; Male; Methods; Middle Aged; Neoplasms; Ovarian Neoplasms; Palatal Neoplasms; Radionuclide Imaging; Rectal Neoplasms; Testicular Neoplasms; Tongue Neoplasms; Tritium; Vitamin K