Search

Mutations in the gene encoding Cu-Zn superoxide dismutase 1 (SOD1) cause a subset of familial amyotrophic lateral sclerosis (fALS) cases. A shared effect of these mutations is that SOD1, which is normally a stable dimer, dissociates into toxic monomers that seed toxic aggregates. Considerable research effort has been devoted to developing compounds that stabilize the dimer of fALS SOD1 variants, but unfortunately, this has not yet resulted in a treatment. We hypothesized that cyclic thiosulfinate cross-linkers, which selectively target a rare, 2 cysteine-containing motif, can stabilize fALS-causing SOD1 variants in vivo. We created a library of chemically diverse cyclic thiosulfinates and determined structure-cross-linking-activity relationships. A pre-lead compound, "S-XL6," was selected based upon its cross-linking rate and drug-like properties. Co-crystallographic structure clearly establishes the binding of S-XL6 at Cys 111 bridging the monomers and stabilizing the SOD1 dimer. Biophysical studies reveal that the degree of stabilization afforded by S-XL6 (up to 24°C) is unprecedented for fALS, and to our knowledge, for any protein target of any kinetic stabilizer. Gene silencing and protein degrading therapeutic approaches require careful dose titration to balance the benefit of diminished fALS SOD1 expression with the toxic loss-of-enzymatic function. We show that S-XL6 does not share this liability because it rescues the activity of fALS SOD1 variants. No pharmacological agent has been proven to bind to SOD1 in vivo. Here, using a fALS mouse model, we demonstrate oral bioavailability; rapid engagement of SOD1G93A by S-XL6 that increases SOD1G93A's in vivo half-life; and that S-XL6 crosses the blood–brain barrier. S-XL6 demonstrated a degree of selectivity by avoiding off-target binding to plasma proteins. Taken together, our results indicate that cyclic thiosulfinate-mediated SOD1 stabilization should receive further attention as a potential therapeutic approach for fALS. Mutations in the Cu-Zn superoxide dismutase 1 gene SOD1 can cause familial amyotrophic lateral sclerosis (fALS) in a process that involves dissociation of the SOD1 dimer. This study shows that a novel cyclic thiosulfinate cross-linker has favorable drug-like properties and can stabilize the SOD1 dimer in vivo, with therapeutic implications for fALS. [ABSTRACT FROM AUTHOR]

Selenium is an essential immunonutrient which holds the human's metabolic activity with its chemical bonds. The organic forms of selenium naturally present in human body are selenocysteine and selenoproteins. These forms have a unique way of synthesis and translational coding. Selenoproteins act as antioxidant warriors for thyroid regulation, male-fertility enhancement, and anti-inflammatory actions. They also participate indirectly in the mechanism of wound healing as oxidative stress reducers. Glutathione peroxidase (GPX) is the major selenoprotein present in the human body, which assists in the control of excessive production of free radical at the site of inflammation. Other than GPX, other selenoproteins include selenoprotein-S that regulates the inflammatory cytokines and selenoprotein-P that serves as an inducer of homeostasis. Previously, reports were mainly focused on the cellular and molecular mechanism of wound healing with reference to various animal models and cell lines. In this review, the role of selenium and its possible routes in translational decoding of selenocysteine, synthesis of selenoproteins, systemic action of selenoproteins and their indirect assimilation in the process of wound healing are explained in detail. Some of the selenium containing compounds which can acts as cancer preventive and therapeutics are also discussed. These compounds directly or indirectly exhibit antioxidant properties which can sustain the intracellular redox status and these activities protect the healthy cells from reactive oxygen species induced oxidative damage. Although the review covers the importance of selenium/selenoproteins in wound healing process, still some unresolved mystery persists which may be resolved in near future. [ABSTRACT FROM AUTHOR]

Human inosine 5′-monophosphate dehydrogenase 2 (hIMPDH2), being an age-old target, has attracted attention recently for anticancer drug development. Mycophenolic acid (MPA), a well-known immunosuppressant drug, was used a lead structure to design and develop modestly potent and selective analogues. The steep structure-activity relationship (SAR) requirements of the lead molecule left little scope to synthesise newer analogues. Here, newer MPA amides were designed, synthesised and evaluated for hIMPDH2 inhibition and cellular efficacy in breast, prostate and glioblastoma cell lines. Few title compounds exhibited cellular activity profile better than MPA itself. The observed differences in the overall biological profile could be attributed to improved structural and physicochemical properties of the analogues over MPA. This is the first report of the activity of MPA derivatives in glioblastoma, the most aggressive brain cancer. [ABSTRACT FROM AUTHOR]

In recent times, notable advancement has been made in the field of electrospinning for the fabrication of numerous types of nanofiber scaffolds. Due to the ultrathin fiber diameter, electrospun nanofiber scaffolds are considered to be an operational delivery system for biomolecules, genes, as well as drugs due to the high specific surface area and stereological porous structure. Here, we introduce some of methods for the integration of drugs and biomolecules within electrospun nanofiber scaffolds, such as blending, surface modification, coaxial process, and emulsion methods. Then, we describe some important biomedical applications of nanofibers in drug delivery systems along with their suitable examples in transdermal systems and wound dressings, cancer therapy, growth factor delivery, nucleic acid delivery, and stem cell delivery. [ABSTRACT FROM AUTHOR]

Inosine 5′-monophosphate dehydrogenase (IMPDH) is important molecular target for potential anticancer, antiviral, antibacterial and immunosuppressive agents. A lot of compounds were obtained to establish their activity toward this enzyme, and to improve therapeutic properties of IMPDH inhibitors used as the drugs. Some of the recently reported analogs exhibited promising results during in vitro and in vivo examinations in comparison to substances applied in clinic. In this review, we describe synthesis and biological activity evaluations of the newly designed IMPDH inhibitors. [ABSTRACT FROM AUTHOR]

Background: Malignant glioma is one of the most devastating tumors in adults with poor patient prognosis. Notably, glioma often exhibits resistance to conventional chemotherapeutic approaches, complicating patient treatments. However, the molecular mediators involved in tumor chemoresistance remain poorly defined, creating a barrier to the successful management of glioma. In the present study, we hypothesized that the antioxidant transcription factor, Nrf2 (nuclear factor erythroid-derived 2 like 2), attenuates glioma cytotoxicity to Carmustine (BCNU), a widely used chemotherapeutic agent known to modulate cellular oxidative balance. Methods: To test the hypothesis, we employed human malignant glioma cell line, U87MG and overexpression of Nrf2 in glioma cells was achieved using both pharmacological and genetic approaches. Results: Notably, induction of Nrf2 was associated with increased expression of heme oxygenase-1 (HO-1), a stress inducible enzyme involved in anti-oxidant defense. In addition, over expression of Nrf2 in U87MG cells significantly attenuated the cytotoxicity of Carmustine as evidenced by both cellular viability assay and flow cytometry analysis. Consistent with this, antioxidants such as glutathione and N-acetyl cysteine significantly reduced Carmustine mediated glioma cytotoxicity. Conclusions: Taken together, these data strongly implicate an unexplored role of Nrf2 in glioma resistance to Carmustine and raise the possible use of Nrf2 inhibitors as adjunct to Carmustine for the treatment of malignant glioma. [ABSTRACT FROM AUTHOR]

Development of effective therapeutic strategies to eliminate cancer stem cells, which play a major role in drug resistance and disease recurrence, is critical to improve cancer treatment outcomes. Our study showed that glioblastoma stem cells (GSCs) exhibited low mitochondrial respiration and high glycolytic activity. These GSCs were highly resistant to standard drugs such as carmustine and temozolomide (TMZ), but showed high sensitivity to a glycolytic inhibitor 3-bromo-2-oxopropionate-1-propyl ester (3-BrOP), especially under hypoxic conditions. We further showed that combination of 3-BrOP with carmustine but not with TMZ achieved a striking synergistic effect and effectively killed GSCs through a rapid depletion of cellular ATP and inhibition of carmustine-induced DNA repair. This drug combination significantly impaired the sphere-forming ability of GSCs in vitro and tumor formation in vivo, leading to increase in the overall survival of mice bearing orthotopic inoculation of GSCs. Further mechanistic study showed that 3-BrOP and carmustine inhibited glyceraldehyde-3-phosphate dehydrogenase and caused a severe energy crisis in GSCs. Our study suggests that GSCs are highly glycolytic and that certain drug combination strategies can be used to effectively overcome their drug resistance based on their metabolic properties. S TEM C ells 2013;31:23-34 [ABSTRACT FROM AUTHOR]

Controlled delivery systems are used to improve therapeutic efficacy and safety of drugs by delivering them over a period of treatment to the site of action at a rate dictated by the need of the physiological environment. A wide variety of polymeric materials, either biodegradable or non-biodegradable but biocompatible, can be used as delivery matrices. Recently, nanofibrous scaffolds, such as the systems fabricated by electrospinning or electrospraying, have been used in the field of biomedical engineering as wound dressings, scaffolds for tissue engineering, and drug delivery systems. The electrospun nanofibrous scaffolds can be used as carriers for various types of drugs, genes, and growth factors, whereby the release profile can be finely controlled by modulation of the scaffold's morphology, porosity, and composition. The main advantage of this system is that it offers site-specific delivery of any number of therapeutics from the scaffold into the body. The aim of this chapter is to review the recent advances on electrospun nanofibrous scaffolds based on biodegradable and biocompatible polymers for controlled drug and biomolecule delivery applications. The use of electrospun scaffolds as drug carriers is promising for future biomedical applications, particularly in the prevention of post-surgical adhesions and infections, for postoperative local chemotherapy, and for bone and skin tissue engineering. [ABSTRACT FROM AUTHOR]

Malignant gliomas are aggressive forms of primary brain tumors characterized by a poor prognosis. The most successful treatment so far is the local implantation of polymer carriers (Gliadel® wafers) for the sustained release of carmustine. To improve the effectiveness of local drug treatment, new polymer carriers and pharmacological agents are currently being investigated. Of particular interest is a set of novel thermo-gelling polymers for the controlled release of hydrophobic drugs such as paclitaxel (e.g., OncoGel™). Herein, we use computational mass transport simulations to investigate the effectiveness of paclitaxel delivery from hydrogel-forming polymer carriers. We found similar (within 1-2 mm) therapeutic penetration distances of paclitaxel when released from these hydrogels as compared with carmustine released from Gliadel® wafers. Effective therapeutic concentrations were maintained for >30 days for paclitaxel when released from the hydrogel as compared with 4 days for carmustine released from Gliadel® wafers. Convection in brain tissue prevented the formation of a uniform drug concentration gradient around the implant. In addition, the surface area to volume ratio of the gel is an important factor that should be considered to maintain a controlled release of paclitaxel within the degradation lifetime of the polymer matrix. © 2011 American Institute of Chemical Engineers Biotechnol. Prog., 2011 [ABSTRACT FROM AUTHOR]

Background: Understanding how human cells in tissue culture adapt to hypothermia may aid in developing new clinical procedures for improved ischemic and hypothermic protection. Human coronary artery endothelial cells grown to confluence at 37°C and then transferred to 25°C become resistant over time to oxidative stress and injury induced by 0°C storage and rewarming. This protection correlates with an increase in intracellular glutathione at 25°C. To help understand the molecular basis of endothelial cold-adaptation, isolated proteins from cold-adapted (25°C/72 h) and pre-adapted cells were analyzed by quantitative proteomic methods and differentially expressed proteins were categorized using the DAVID Bioinformatics Resource. Results: Cells adapted to 25°C expressed changes in the abundance of 219 unique proteins representing a broad range of categories such as translation, glycolysis, biosynthetic (anabolic) processes, NAD, cytoskeletal organization, RNA processing, oxidoreductase activity, response-to-stress and cell redox homeostasis. The number of proteins that decreased significantly with cold-adaptation exceeded the number that increased by 2:1. Almost half of the decreases were associated with protein metabolic processes and a third were related to anabolic processes including protein, DNA and fatty acid synthesis. Changes consistent with the suppression of cytoskeletal dynamics provided further evidence that cold-adapted cells are in an energy conserving state. Among the specific changes were increases in the abundance and activity of redox proteins glutathione S-transferase, thioredoxin and thioredoxin reductase, which correlated with a decrease in oxidative stress, an increase in protein glutathionylation, and a recovery of reduced protein thiols during rewarming from 0°C. Increases in S-adenosylhomocysteine hydrolase and nicotinamide phosphoribosyltransferase implicate a central role for the methionine-cysteine transulfuration pathway in increasing glutathione levels and the NAD salvage pathway in increasing the reducing capacity of cold-adapted cells. Conclusions: Endothelial adaptation to mild-moderate hypothermia down-regulates anabolic processes and increases the reducing capacity of cells to enhance their resistance to oxidation and injury associated with 0°C storage and rewarming. Inducing these characteristics in a clinical setting could potentially limit the damaging effects of energy insufficiency due to ischemia and prevent the disruption of integrated metabolism at low temperatures. [ABSTRACT FROM AUTHOR]

Resistance of neoplastic cells to the alkylating drug BCNU [1,3-bis(2-chloroethyl)-1-nitrosourea] has been correlated with expression of O 6-methylguanine-DNA methyltransferase, which repairs the O 6-chloroethylguanine produced by the drug. Other possible mechanisms of resistance include raised levels of glutathione or increased repair of the DNA interstrand cross-links formed by BCNU. Transcriptional profiling revealed the upregulation of several metallothionein (MT) genes in a BCNU-resistant medulloblastoma cell line [D341 MED (OBR)] relative to its parental line. Previous studies have shown that MTs, through their reactive thiol groups can quench nitrogen mustard-derived alkylating drugs. In this report, we evaluate whether MTs can also quench BCNU. To demonstrate the binding of BCNU to MT, we used an assay that measured the release of the MT-bound divalent cations (Zn2+, Cd2+) upon their displacement by the drug. We also measured the decomposition rates of BCNU at those reaction conditions. The rate of release of the cations was higher in pH 7.4 than at pH 7.0, which is likely a result of more rapid decomposition of BCNU (thus faster release of MT-binding intermediate) at pH 7.4 than at pH 7.0. We demonstrate that resistance to BCNU may be a result of elevated levels of MTs which act by sequestering the drug’s decomposition product(s). [ABSTRACT FROM AUTHOR]

The aim of this study is the development of microspheres of BCNU for intracranial administration, as an alternative to marketed novel Gliadel® Implant in the treatment of brain tumours. H poly-lactide-co-glycolide biodegradable microspheres of BCNU with a mean size of 33.5 ± 1.8 µm were obtained by an oil-in-water emulsion solvent evaporation method. Their small size would allow their intracranial administration through a needle by cerebral stereotaxia if tumour recurrence occurs, without a surgical intervention, as Gliadel® needs. BCNU was released from these microspheres during 21 days, mainly by a mechanism of diffusion from the polymer matrix (K = 2.91 mg days-½). The cytotoxic effects of these microspheres on human glioblastoma cells were demonstrated all through 21 days and the value of percentage of viable cells was less than 40%. These microspheres should be commercialized as a freeze-dried product to keep at -20°C. Three hundred and twenty milligrams of microspheres contain 61.6 mg of BCNU, the same amount of BCNU contained in 1600 mg or eight wafers of Gliadel usually implanted after the tumour resection. [ABSTRACT FROM AUTHOR]

Inosine monophosphate dehydrogenase (IMPDH) is a key enzyme of de novo purine nucleotide biosynthesis and is viewed as an important target in the quest for discovery of drugs in the antiviral, antibacterial and anticancer therapeutic areas. This review focuses on the medicinal chemistry, drug discovery and chemical biology of IMPDH. Examples of IMP and cofactor site-directed inhibitors, allosteric inhibitors and isoform-selective inhibitors are presented. Comparison of IMPDHs from different organisms is also made to facilitate the design of species-selective IMPDH inhibitors for drug discovery. Special emphasis in the review is placed on IMPDH from Mycobacterium tuberculosis. © 2007 Wiley Periodicals, Inc. Med Res Rev, 28, No. 2, 219-232, 2008 [ABSTRACT FROM AUTHOR]

Cancer is the second leading cause of death worldwide. There is thus increased interest in alternative treatment modalities that include chemotherapy, hormonal supplements, surgery, radiation therapy, complementary or alterative medicine, used alone or in combination. Therefore patients who are subjected to combination treatments such as hormonal supplements or alternative medicine face considerable risk of drug-drug interactions. The administration of herbal drugs by patients without a physician's prior counseling is increasing globally and there is a possibility of herb-drug interactions too. Herbal drugs or extracts themselves contain a combination of active constituents, which interact within themselves and also between other prescribed pharmaceutical drugs to either enhance (synergize) or decrease (antagonize) the therapeutic effect. This review focuses on a number of reports of herb-drug interactions, their mechanism of action with a special emphasis on dietetic phytochemicals such as quercetin, genistein, curcumin and catechins. All phytochemicals tend to increase the therapeutic effect by blocking one or more targets of the signal transduction pathway, by increasing the bioavailability of the other drug or, by stabilizing the other drug in the system. Copyright © 2006 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

The benzamide RH-5854 is shown to be highly potent toward tumor cells and to arrest nuclear division by a highly specific covalent binding to the {szligbeta}-subunit of tubulin in the colchicine binding region. Binding of 3H-RH-5854 to {szligbeta}-tubulin in HCT-116 colon cancer cells is saturable and has been exploited in the development of a cell-based competitive binding assay, which allows antitubulin effects to be detected inwhole cells. 3H-RH-5854 binding is strongly inhibited by preincubating the cells with compounds that bind to the colchicine site andwith paclitaxel. Binding of 3H-RH-5854 is enhanced by preincubating the cells with vinblastine but not by other agents that bind at or near the vinblastine site (ansamitocin P-3 and phomopsin A). Various cytotoxic agents that do not act on tubulin do not affect binding of 3H-RH-5854 in HCT-116 cells, demonstrating specificity of the assay for detection of antitubulin activity. As an alternative to traditional assays that employ isolated brain tubulin, the 3HRH-5854 binding assay enables screening for antitubulin effects directly in tumor cells, providing an assay that accounts for cell-specific criteria that influence sensitivity such as different tubulin isotypes, tubulin mutations, drug metabolism, and efflux mechanisms. [ABSTRACT FROM AUTHOR]

Purpose. To determine whether gamma-glutamyl transpeptidase (γ-GT) is involved in the maintenance of elevated cysteine levels in cervical carcinoma. Methods. Four cervical carcinoma cell lines were tested in vitro for cysteine accumulation and γ-GT levels. The highest and lowest γ-GT-expressing cell lines were used in in vivo experiments to determine the effect of γ-GT inhibition on cysteine levels. Results. Treatment of a series of cervical carcinoma cell lines with acivicin decreased intracellular cysteine concentrations. Cysteine depletion was evident in Me180 cells which had the greatest levels of γ-GT activity, and had a more pronounced cysteine decrease in medium with glutathione and cysteine concentrations simulating the in vivo situation. Also investigated were the effects of inhibition of γ-GT activity on intracellular cysteine levels in xenografts grown in severe combined immunodeficient (SCID) mice. With the use of 35 mg/kg of acivicin, γ-GT activity decreased to basal levels of detection in both tumour types and significant decreases in cysteine levels were seen in the high γ-GT-expressing tumours (Me180). Thus, inhibition of γ-GT activity may have therapeutic potential in high-expressing cancers. Conclusions. In tumours and cell lines with elevated levels of γ-GT activity, inhibition of this enzyme led to decreases of cysteine levels. [ABSTRACT FROM AUTHOR]

Purpose: We had previously shown in acute leukemia and in breast and ovary carcinoma patients that a cholesterol-rich emulsion (LDE) that binds to receptors for low-density lipoprotein (LDL) may concentrate in neoplastic tissues. In this study, the potential of LDE as a carrier for anticancer drugs was investigated. Methods: LDE was associated with carmustine, and the cytotoxicity of the LDE-carmustine complex was studied in a neoplastic cell line and its biodistribution was studied in mice. The plasma kinetics of the complex and its uptake by tumor and normal tissue were determined in cancer patients. Finally, an exploratory clinical study to determine the toxicity profile of LDE-carmustine at escalating dose levels was conducted in 42 advanced cancer patients refractory to conventional chemotherapy. Results: Carmustine formed a stable association with LDE. The pharmacological action of carmustine, as tested in cancer cells, was not diminished by association with LDE compared with the free drug and was indeed mediated by the LDL receptor. The biodistribution in mice and plasma kinetics in patients of the emulsion were not changed by association of the drug. The uptake of LDE-carmustine by tumor was severalfold greater than the uptake by the corresponding normal tissue. Finally, patients treated with LDE-carmustine showed negligible side effects even at very high dose levels. Conclusions: Association with LDE preserves the cytotoxicity of carmustine and markedly diminishes its side effects. [ABSTRACT FROM AUTHOR]

Contemporary treatment of malignant brain tumors has been hampered by problems with drug delivery to the tumor bed. Inherent boundaries of the central nervous system, such as the blood-brain barrier or the bloodcerebrospinal fluid barrier, and a general lack of response to many chemotherapeutic agents have led to alternative treatment modalities. In general, all these modalities have sought to either disrupt or bypass the physiologic brain barriers and deliver the drug directly to the tumor. This article reviews past, as well as current, methods of drug delivery to tumors of the central nervous system. Special emphasis is placed on biodegradable polymers that can release chemotherapeutic agents against malignant gliomas. A variety of other nonchemotherapeutic drugs, including antiangiogenesis and immunotherapeutic agents, are presented in the context of new polymer technology. Finally, future directions in drug delivery are discussed with an overview on new advances in emerging biotechnology. [ABSTRACT FROM AUTHOR]

One of the mechanisms of action of a new oncolytic agent, benzamide riboside (BR) is by inhibiting inosine 5'-monophosphate dehydrogenase (IMPDH) which catalyzes the formation of xanthine 5'-monophosphate from inosine 5'monophosphate and nicotinamide adenine dinucleotide, thereby restricting the biosynthesis of guanylates. In the present study BR (10-20 µM) induced apoptosis in a human ovarian carcinoma N.1 cell line (a monoclonal derivative of its heterogenous parent line HOC-7). This was ascertained by DNA fragmentation, TUNEL assay, [poly(ADP)ribose polymerase]-cleavage and alteration in cell morphology. Apoptosis was accompanied by sustained c-Myc expression, concurrent down-regulation of cdc25A mRNA and protein, and by inhibition of Cdk2 activity. Both Cdk2 and cdc25A are G1 phase specific genes and Cdk2 is the target of Cdc25A. These studies demonstrate that BR exhibits dual mechanisms of action, first by inhibiting IMPDH, and second by inducing apoptosis, which is associated with repression of components of the cell cycle that are downstream of constitutive cMyc expression. [ABSTRACT FROM AUTHOR]

We have used the 9L rat brain tumor model to search for effective chemotherapeutic approaches to the management of brain tumors. Several antineoplastic agents which have been proposed or are currently being used for human brain tumors, including 1,3-bis (2-chloroethyl)-1-nitrosourea (BCNU), bleomycin, aziridinylbenzoquinone (AZQ), cis-Platinum, and acivicin, were administered intravenously (iv), intraperitoneally (ip), or intracerebrally (ic) to rats burdened with the intracranial 9L gliosarcoma. The results confirm that BCNU is the most effective systemic agent among the chemotherapeutic agents tested as indicated by its ability to significantly increase the median survival time (MST) and life span of the tumor-burdened animals. Bleomycin is an effective agent against the intracranial 9L tumor when administered ic. While neither systemic single iv dose AZQ (0.5-2.5 mg/kg) nor multiple ip treatments (0.5-1.0 mg/kg × 5, q 6 h) were effective in prolonging the survival, single is dose AZQ (5-50 μg/rat) treatment significantly increased the MST of the treated animals (P < 0.05). Systemic AZQ treatments using higher doses produced a hematological toxicity, resulting in a decrease in MST of the treated animals. Cis-Platinum, either administered ip or ic, produced only a marginal effect on survival, although acute neurologic toxicity limited the dose of cis-Patinum that could be administered ic. Acivicin, either administered ip or ic, produced no effect on the survival of treated animals. Our results suggest that local treatment with certain antineoplastic agents may be an efficient therapy in the management of brain tumors. [ABSTRACT FROM AUTHOR]

Wistar rats implanted intracerebrally with AA ascites tumor were injected seven or eight days later with C-labelled BCNU. Radioactive compounds in samples of plasma, tumor, and contralateral brain were identified after injection at intervals by doing chloroform extraction and thin layer radiochromatography. At 60 min after injection radioactivity levels were 56% higher in the tumor than in contralateral brain. This increase was due mainly to 2-chloroethyl isocyanate, which binds to amino groups and/ or nucleic acid. The results demonstrated both a higher concentration and a faster decomposition of BCNU in the tumor. [ABSTRACT FROM AUTHOR]

Tiazofurin is an oncolytic nucleoside analog that has shown therapeutic activity in end-stage acute non-lymphocytic leukemia and in chronic granulocytic leukemia in blast crisis. Tiazofurin is anabolized to the active metabolite, TAD, which inhibits IMP dehydrogenase activity, leading to a reduction in guanylate pools and to the cessation of neoplastic cell proliferation. The drug exhibits potent cytostatic and cytotoxic activity against hepatoma 3924A cells in culture. In growth-inhibition and clonogenic assays, the 50% inhibitory concentration of tiazofurin was 3.8 and 4.2 microM, respectively. Dipyridamole, an inhibitor of nucleoside transport, curtails the salvage of nucleosides and bases for nucleotide biosynthesis. Dipyridamole exhibited cytotoxicity against hepatoma 3924A cells, with an LC50 of 24 microM and an IC50 of 29 microM being recorded. A combination of tiazofurin and dipyridamole provided synergistic cytotoxicity in hepatoma 3924A cells in culture. This synergistic activity was dependent on the order of addition of the drugs. Simultaneous addition of the two drugs produced antagonism, whereas preincubation of cells with tiazofurin or dipyridamole followed by addition of the second drug resulted in synergy. TAD concentrations were significantly higher (129% and 135%) in cells that had been pretreated with tiazofurin or dipyridamole before the addition of the second agent as compared with cells that had been treated simultaneously (113%). These studies indicate the importance of the order of the addition of drugs to obtain a synergistic response in combination chemotherapy and suggest the need for a careful selection of drug modulation in clinical trials of tiazofurin and dipyridamole. [ABSTRACT FROM AUTHOR]

A study on the oncolytic activity of the L-cysteine derivative L-cysteine, ethyl ester, S-(N-methylcarbamate) monohydrochloride (NSC 303861), revealed that the drug caused complete regression of the MX-1 human mammary tumor xenograft. The compound also exhibited moderate antitumor activity against murine leukemia P388 (T/C value of 169% at a daily dose of 400 mg/kg) and against M5076 sarcoma (T/C value of 135% at a daily dose of 600 mg/kg). The drug was inactive against B16 melanoma, Lewis lung, colon 38 and CD8F1 mammary carcinomas. The compound exhibited significant cytotoxicity against hepatoma 3924A cells in culture (LC50 = 6 microM). Studies on the mechanism of action revealed that the cytotoxicity of the drug could be partially abrogated by protecting hepatoma 3924A cells in culture with L-glutamine. At 6 h after injection of the compound (400 mg/kg) into rats bearing hepatoma 3924A, the pools of L-glutamine and L-glutamate in the tumor decreased to 33% and 71%, respectively, of control levels; the drug selectively inhibited the activities of L-glutamine-requiring enzymes of purine nucleotide biosynthesis, amidophosphoribosyltransferase, FGAM synthase, and GMP synthase, to 21%, 1%, and 69%, respectively, without significantly altering the activities of pyrimidine biosynthetic enzymes, carbamoylphosphate synthase II and CTP synthase. Measurement of the nucleotide concentrations further corroborated the actions of the drug on the purine nucleotide biosynthetic enzyme activities. Drug injection (400 mg/kg) in the hepatoma 3924A-bearing rats reduced the concentrations of IMP in the tumor to 52%, those of total adenylates to 52%, those of total guanylates to 57%, and those of NAD to 73%, without significantly perturbing the pyrimidine nucleotide pools. Studies on the mechanism of action of the L-cysteine derivative suggested that the compound behaved as an L-glutamine antagonist, selectively acting on the enzymes of purine nucleotide biosynthesis. [ABSTRACT FROM AUTHOR]

A phase I and pharmacokinetic study of tiazofurin (NSC 286193), a C-nucleoside that inhibits IMP dehydrogenase, has been completed. The drug was administered by continuous infusion over 5 days. The maximum tolerated dose was 1650 mg/m2 per day, neurological toxicity being the dose-limiting factor. Gastrointestinal and hematological toxicity were mild. A definite relationship exists between dosage and steady-state levels. The plasma clearance was 29.13 (+/- SD 4.05) ml/min per m2. No complete or partial remissions were demonstrated among the 18 patients treated at five dose levels between 550 mg/m2 and 2200 mg/m2 per day. [ABSTRACT FROM AUTHOR]

A study was made of the in vivo effects of equitoxic doses of AT-125 and 5-FU combination, being administered either simultaneously (% ILS 152) or with a 6-h pretreatment with AT-125 (% ILS 184). To examine the biochemical basis for the scheduled synergism, measurements were made of the concentration of PRPP, the specific activities of CPS II, cytidine, thymidine, uridine, deoxyuridine kinases, and fluorinated nucleotide formation in P388 tumors and the small intestine. Two hours after in vivo simultaneous treatment of mice bearing tumors the concentration of PRPP increased 9- and 6-fold above baseline in the tumor and the small intestine, respectively. In the AT-125 pretreatment arm the concentration of PRPP increased 18- and 7-fold above baseline in the tumor and the small intestine, respectively. CPS II activity was reduced to 28%-18% of control in the tumors in the simultaneous and pretreatment groups, respectively, whereas it remained unchanged in the small intestine. Specific activities of cytidine kinase (5.5±1), thymidine kinase (4.0±1.6), uridine kinase (35.6±6.5), and deoxyuridine kinase (2.4±1.1) nmol/mg protein/h remained unchanged with treatment. In concert with the increased intratumor concentration of PRPP, fluorinated nucleotide formation was proportionally increased in the treatment arms. These results indicate the importance of drug scheduling of the above two agents in treating P388 leukemia. [ABSTRACT FROM AUTHOR]

In vitro drug sensitivity of tumour biopsies is currently being determined using a variety of methods. For these chemosensitivity assays many drugs are required at short notice, and this in turn means that the drugs must generally be stored in solution. There are, however, a number of potential problems associated with dissolving and storing drugs for in vitro use, which include (a) drug adsorption; (b) effects of freezing; (c) drug stability under the normal conditions of dilution and setting up of an in vitro assay; and (d) insolubility of drugs in normal saline (NS) or phosphate-buffered saline (PBS). These problems are considered in general, and some recommendations for use of solutions of drugs in in vitro assays are suggested. The nitrosoureas and alkylating agents are also investigated in greate detail in this respect. The nitrosoureas are found to be very labile in PBS at pH 7, with 5% degradation (t) occurring in 10-50 min at room temeperature. These values are increased about 10-fold on refrigeration and about 5-to 10-fold on reduction of the pH of the medium to pH 4-5. At pH 7 and room temperature, t is observed in under 1 h with the alkylating agents nitrogen mustard, chlorambucil, melphalan, 2,5-diaziridinyl-3,6-bis(2-hydroxyethylamino)-1,4-benzoquinone (BZQ), dibromodulcitol, dibromomannitol, treosulphan, and procarbazine. Of the other alkylating agents, 4-hydroperoxycylophosphamide (sometimes used in vitro in place of cyclophosphamide), busulphan, dianhydrogalactitol, aziridinylbenzoquinone (AZQ), and dacarbazine have a t of between 2 and 24 h, while ifosfamide and pentamethylmelamine are both stable in aqueous solution for > 7 days. About half the drugs studied in detail have been stored frozen in solution for in vitro use, although very little is known about their stability under these conditions. [ABSTRACT FROM AUTHOR]

The effects of a range of anticancer drugs on murine neuroblastoma cells, used as a readily reproducible model system, have been compared by means of colony-forming assays and analyses by flow microfluorimetry (FMF). FMF provides the most rapid means of assessing the kinetic effects of drugs on cells. However, interpretation of these data is not clear-cut, since drug effects are highly dose-dependent and no distinction can be made easily between progression arrest and cell kill. Thus whilst FMF allows some qualitative assessment of the perturbing effects of cytotoxic drugs quantitative evaluation of cytotoxicity is still dependent on data from the more time-consuming cloning assays. However, when cells are treated with certain drugs, e.g., methotrexate, vincristine, or VM26, for only 1 h, negligible kill occurred as measured by colony formation. Therefore it appears necessary to prolong in vitro exposure time when testing these drugs or evaluating cytotoxicity of potential antitumour agents in vitro. [ABSTRACT FROM AUTHOR]

As determined by a colorimetric assay measuring parent compounds plus ether-extractable nitroso-containing metabolites, N,N'-bis(2-chloroethyl)-N-nitrosourea (BCNU) disappeared more rapidly than N-(2-chloroethyl)-N'cyclohexyl-N-nitrosourea (CCNU) and N-(2-chloroethyl)-N'-(4-transmethylcyclohexyl)-N-nitrosourea (MeCCNU) and their products from the tissues of mice injected IV. Assay of selected samples by high-pressure liquid chromatography revealed that the colorimetric assay for BCNU was specific in that the two assays gave equivalent results. Following IV-injections of CCNU and MeCCNU, however, levels of the parent compounds decreased much more rapidly than the total, color-producing material. Of seven tissues, the largest Cxt values for BCNU, as determined by the colorimetric assay, were noted for blood (442 microgram-min/ml) and large intestine (285 microgram-min/g). Liver (29 microgram-min/g) had the lowest Cxt value, reflecting rapid metabolism of the compound by this organ. Color-producing material related to CCNU disappeared from the solid tissues of mice in a manner generally parallel to that for blood. Of the Cxt values for this compound and its products, those for lung (1753 microgram-equivalents-min/g), kidney (1633 microgram-equivalents-min/g), and small intestine (1557 microgram-equivalents-min/g) were highest. Consistent with its slower rate of metabolism, MeCCNU and its color-producing metabolites remained in most tissues of mice for 12 h following injection. Except for brain (1434 microgram-equivalents-min/g), Cxt values for this nitrosourea and its metabolites in tissues were higher than those of blood (5485 microgram-equivalents-min/ml), with kidney (15,324 micrograms-equivalents-min/g), liver (12,921 microgram-equivalents-min/g), and large intestine (11,501 microgram-equivalents-min/g) being highest. For each nitrosourea, a fair correlation was observed between the Cxt values for tissues and the toxic and/or antitumor effects at those sites. [ABSTRACT FROM AUTHOR]

This article reviews the role of implantable pumps in the treatment of CNS tumors. Systemic administration of chemotherapeutic agents has been associated with various problems, including adverse systemic effects and decreased concentration of the drug at the target site. Continuous infusion of chemotherapeutic agents with implantble pumps have been used in an attempt to overcome these problems. Various different chemo-therapeutic agents have been used for this purpose, and catheters have been placed in the intraspinal, intraventricular and intratumoral locations. [ABSTRACT FROM AUTHOR]

The present study was undertaken to explore the possible interaction between tumor immunity and antineoplastic agents at the brain level in murine lymphoma models. Host immunity against intracerebral lymphoma graft was directed against tumor-associated histocompatibility antigens, using an appropriate design of genetic distance between host and tumor. It was revealed that primary graft response against lymphoma cells can be demonstrated in the central nervous system. Immunochemotherapy synergism can occur at the mouse brain level, when allogeneic lymphomas are inoculated intracerebrally and the recipient hosts are treated with antineoplastic agents capable of crossing the blood-brain-barrier. [ABSTRACT FROM AUTHOR]

The benzamideRH-5854 is shown to be highly potent toward tumor cells and to arrest nuclear division by a highly specific covalent binding to the β-subunit of tubulin in the colchicine [...]