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To carry out a comparative study of inhibition of radiation carcinogenesis using alpha-difluoromethylornithine (DFMO), tinctures of ginseng, eleutherococcus and leuzea in female rats.Locally bred female LIO-strain rats were subjected to a single whole body γ-irradiation dose of 4 Gy at 12 weeks of age. Modifying drugs were given with drinking water from the 10th day after irradiation until the end of the experiment (for 16 months).Irradiated rats developed tumors 70.0-79.6% (malignant tumors: 43.7-45.0%) with a multiplicity of 1.48-1.75 (malignant: 0.5-0.58), while in unirradiated animals the incidence of all/malignant tumors was 21.9%/7.7% with multiplicity of 0.22/0.08. In exposed rats tumors most often developed in the mammary gland - 57.3%, reproductive and endocrine organs - 27.2%, and other localizations - 29.1%. All drugs, except leuzea, significantly reduced incidence and multiplicity of tumors, overall or at some localizations in irradiated rats. Highest, and practically equal inhibition, was shown by ginseng and DFMO, while eleutherococcus was clearly inferior. Ginseng reduced overall tumor incidence and multiplicity by 1.5 and 2.4 times, malignant tumor incidence and multiplicity - by 2.5 and 2.9 times, respectively.The ginseng extract is the most promising radiation carcinogenesis inhibitor tested.

Background Mononuclear platinum anticancer agents hold a pivotal place in the treatment of many forms of cancers, however, there is a potential to improve response to evade resistance development and toxic side effects. BBR3464 is a promising trinuclear platinum anticancer agent, which is a polyamine mimic. The aim was to investigate the influence of polyamine pool reduction on the cytotoxic effects of the trinuclear platinum complex BBR3464 and cisplatin. Polyamine pool reduction was achieved by treating cells with either the polyamine biosynthesis inhibitor α-difluoromethylornithine (DFMO) or the polyamine analogue N1,N11-diethylnorspermine (DENSPM). Methods A human squamous cell carcinoma cell line, LU-HNSCC-4, established from a primary head and neck tumour was used to evaluate cellular effects of each drug alone or combinations thereof. High-performance liquid-chromatography was used to quantify intracellular polyamine contents. Inductively coupled mass spectroscopy was used to quantify intracellular platinum uptake. Cells were exposed to DFMO or DENSPM during 48 h at concentrations ranging from 0 to 5 mM or 0 to 10 μM, respectively. Thereafter, non-treated and treated cells were exposed to cisplatin or BBR3464 during 1 h at concentrations ranging from 0 to 100 μM. A 96-well assay was used to determine cytotoxicity after five days after treatment. Results The cytotoxic effect of BBR3464 on LU-HNSCC-4 cells was increased after cells were pre-treated with DENSPM or DFMO, and the interaction was found to be synergistic. In contrast, the interaction between cisplatin and DFMO or DENSPM was near-additive to antagonistic. The intracellular levels of the polyamines putrescine and spermidine were decreased after treatment with DFMO, and treatment with DENSPM resulted in an increase in putrescine level and concomitant decrease in spermidine and spermine levels. The uptake of BBR3464 was significantly increased after pre-treatment of the cells with DFMO, and varied dependent on the concentration of DENSPM. The uptake of cisplatin was unchanged. Conclusions Taken together, these results demonstrate that combinations of polyamine synthesis inhibitors with BBR3464 appear to be a promising approach to enhance the anticancer activity against HSCC.

Polyamines (PAs) are small aliphatic amines that play a major role in multicellular functions. The PA levels are controlled by ornithine decarboxylase (ODC), the rate limiting enzyme of PA biosynthesis. alpha-difluoromethylornithine (DFMO) is the ODC inhibitor, which has been shown to act as an antiproliferative agent in human cancer cells by irreversibly inhibiting ODC, which is overexpressed in breast cancer cells. Roscovitine (ROSC; CYC202), a selective cyclin-dependent kinase inhibitor, induces cell cycle arrest and concomitantly apoptosis in tumor cells. In this study, we aimed to investigate the possible role of PAs in ROSC-induced apoptosis in estrogen-dependent MCF-7 breast cancer cells. Cell viability was assessed following the exposure of MCF-7 cells to DFMO and/or ROSC by MTT cell viability assay. To evaluate the drug-induced apoptotic events, DNA fragmentation by Cell Death ELISA assay and 4,6-diamidino-2-phenylindole staining, were utilized. The disruption of mitochondrial membrane potential, caspase-9 and PARP cleavage was also determined in order to investigate the role of mitochondrial-mediated apoptosis. The modulation of Bcl-2 family members was also evaluated using the immunoblotting technique. Drug-induced reactive oxygen species was determined by a fluorometer following 2',7'-dichlorofluorescein diacetate staining. We found that ROSC induced apoptosis in a dose- and caspase-dependent manner. The ODC specific inhibitor, DFMO, altered the apoptotic effects of ROSC by increasing the generation of reactive oxygen species, decreasing the PA intracellular pool and modulating pro-apoptotic and anti-apoptotic Bcl-2 family members. All these findings suggest that ODC may be a critical target for evaluating the PA metabolic pathway as a therapeutic target in ROSC-induced mitochondrial-mediated apoptotis in estrogen-dependent MCF-7 breast cancer cells.

The three-dimensional structure of glycosomal glyceraldehyde-3-phosphate dehydrogenase [D-glyceraldehyde-3-phosphate:NAD+ oxidoreductase (phosphorylating), EC 1.12.1.12] from the sleeping-sickness parasite Trypanosoma brucei was solved by molecular replacement at 3.2-angstrom resolution with an x-ray data set collected by the Laue method. For data collection, three crystals were exposed to the polychromatic synchrotron x-ray beam for a total of 20.5 sec. The structure was solved by using the Bacillus stearothermophilus enzyme model [Skarzynski, T., Moody, P. C. E. & Wonacott, A. J. (1987) J. Mol. Biol. 193, 171-187] with a partial data set which was 37% complete. The crystals contain six subunits per asymmetric unit, which allowed us to overcome the absence of >60% of the reflections by 6-fold density averaging. After molecular dynamics refinement, the current molecular model has an R factor of 17.6%. Comparing the structure of the trypanosome enzyme with that of the homologous human muscle enzyme, which was determined at 2.4-angstrom resolution, reveals important structural differences in the NAD binding region. These are of great interest for the design of specific inhibitors of the parasite enzyme.

We studied the effect of polyamine depletion on growth and cell cycle characteristics of subcutaneously grown Lewis lung carcinoma (LLC) and fibrosarcoma (FIO 26) in mice. Polyamine depletion was achieved by inhibition of ornithine decarboxylase using 2-(difluoromethyl)ornithine, limitation of exogenous polyamines by administration of a polyamine-poor diet and decontamination of the gastrointestinal tract, and inhibition of endogenous polyamine reutilization by N,N'-bis-(2,3-butadienyl)putrescine (MDL 72527). Determination of S-phase cells was performed in tumor-cell suspensions by flow cytometry and in tumor tissue sections by microscopy, following in vivo labelling with 5-bromo-2'-deoxyuridine (BUdR). DNA synthesis rate was estimated from the incorporation of in vivo-injected [H-3]-thymidine (H-3-TdR). Both solid tumors almost completely stopped growing after access to polyamines was blocked. Growth inhibition was, however, not attended by changes in cell-cycle-phase distribution. Paradoxically, we measured increased in vivo H-3-TdR incorporation rates and unaltered BUdR-linked staining intensity in treated tumors. Injection of putrescine into treated LLC-bearing mice resulted in an increase in intracellular putrescine and spermidine concentrations, a slight increase in the number of S-phase cells and a marked drop in DNA synthesis rate within the following 9 hr.

The effect of alpha-difluoromethylornithine (DFMO) administered in drinking water (0.2 and 0.5%) against liver and intestinal coccidioses in experimentally infected rabbits was studied. Zootechnical and clinical parameters were used to assess the efficacy of the compound. In both coccidioses the lower dose did not show any important effect. The higher dosage (0.5%) however, reduced the lesions induced by coccidia to an important extent. The animals infected and treated with 0.5% DFMO showed similar weight gain, food intake and relative liver weight figures to the non-infected controls. Serum transaminase levels in the rabbits infected with Eimeria stiedai and treated with 0.5% DFMO were close to those of the non-infected animals. Infected rabbits treated with this dosage also showed reductions (over 80%) in faecal oocyst output.

The pharmacokinetics of alpha-difluoromethylornithine (DFMO), an irreversible inhibitor of polyamine biosynthesis, were investigated in BALB/c (nude) mice after i.p. injection and after oral administration of radiolabeled drug. After i.p. injection the compound was rapidly cleared from the serum (t1/2 alpha = 14 min; t1/2 beta = 2.1 h) and from tissues such as muscle, liver and kidney (t1/2 alpha = 30-60 min; t1/2 beta = 2.1 h). DFMO concentrations were proportional to the administered dose (10-2000 mg/kg) in both serum and tissues. Oral administration of DFMO was carried out by dissolving the compound in drinking water at a concentration of 20 g/l. Studies on the distribution showed that DFMO did not accumulate preferentially in any particular tissue. An extremely wide variation in the dose actually achieved in different animals was observed; this ranged from 350 to 2800 mg/kg for a 14-h treatment period. A significant correlation (r = 0.83-0.92) between the dose of DFMO, calculated from the consumption of drinking water for each individual animal, and the DFMO concentrations in serum, muscle, spleen, liver and kidney was found. Similarly, it was shown that oral administration of DFMO during the daytime resulted in 10- to 15-fold lower levels than administration during the night. After discontinuation of treatment DFMO levels in serum and tissues decreased by 50% in approximately 6 h. From these results it is concluded that the optimal treatment schedule of mice with DFMO (or other drugs with similar pharmacodynamic properties) consists in a combination of oral administration via the drinking water and additional i.p. injection (during the daytime). Furthermore, the drug intake of the individual animals should be monitored to check whether the experimental requirements are actually fulfilled.