Validation of tumour models for use in anticancer nanomedicine evaluation: the EPR effect and cathepsin B-mediated drug release rate.

Purpose: Intravenously (i.v.) administered nanomedicines have the potential for tumour targeting due to the enhanced permeability and retention (EPR) effect, but in vivo tumour models are rarely calibrated with respect to functional vascular permeability and/or mechanisms controlling intratumoural drug release.

Use of the hollow fiber assay for the evaluation of DNA damaging agents.

Introduction: The preclinical development and clinical progression of potential anticancer agents are highly time and resource-intensive. Traditionally, promising compounds in vitro undergo further screening in xenograft models, a long process that uses large numbers of animals. In order to hasten compound progression, the hollow fiber assay (HFA) was developed by the US National Cancer Institute as an additional filtering step in drug development, bridging the gap between in vitro and xenograft compound screening.

Potentiation of the activity of cisplatin in a human colon tumour xenograft model by auristatin PYE, a structural modification of dolastatin 10.

Dolastatin 10, a marine natural product peptide, is now known to act as a vascular disrupting agent (VDA). These VDA properties were not known when other aspects of its promising pre-clinical profile led to initial unsuccessful clinical trials. Auristatin PYE, a synthetic analogue of dolastatin 10, has demonstrated improved activity in preliminary in vivo studies.

Development of a novel tumor-targeted vascular disrupting agent activated by membrane-type matrix metalloproteinases.

Vascular disrupting agents (VDA) offer a strategy to starve solid tumors of nutrients and oxygen concomitant with tumor shrinkage. Several VDAs have progressed into early clinical trials, but their therapeutic value seems to be compromised by systemic toxicity. In this report, we describe the design and characterization of a novel VDA, ICT2588, that is nontoxic until activated specifically in the tumor by membrane-type 1 matrix metalloproteinase (MT1-MMP).

Sodium pancratistatin 3,4-o-cyclic phosphate, a water-soluble synthetic derivative of pancratistatin, is highly effective in a human colon tumor model.

Sodium pancratistatin 3,4- O-cyclic phosphate ( 2) is a novel water-soluble synthetic derivative of pancratistatin ( 1), a natural alkaloid constituent of Amaryllidaceae plants, that exhibits good cytostatic and antineoplastic activity but is highly insoluble. Unlike most other natural alkaloids it does not act by binding to tubulin, and its mechanism of action has yet to be fully elucidated. Here the efficacy of 2 in a human colon adenocarcinoma model, DLD-1, and some understanding of its mode of action are investigated.

Auristatin PYE, a novel synthetic derivative of dolastatin 10, is highly effective in human colon tumour models.

Despite promising early data, the natural product dolastatin 10 has not been successful as a single agent in phase II clinical trials. Herein the mechanism of action and efficacy of a synthetic analogue, auristatin PYE, was investigated in 2 human colon adenocarcinoma models, DLD-1 and COLO 205. In vivo efficacy was assessed in subcutaneous xenografts following intravenous administration.

The hollow fibre model--facilitating anti-cancer pre-clinical pharmacodynamics and improving animal welfare.

We describe a modified hollow fibre assay (HFA) for investigating the potential of novel molecules as pharmaceutical agents. In particular the assay provides drug/target interaction data that can facilitate the selection of lead compounds for further evaluation in more sophisticated solid tumour models, whilst successfully implementing the 3Rs - the 'replacement' 'refinement' and 'reduction' of animals. This more ethical and rapid approach to early drug development does not compromise on the validity, sensitivity, predictivity or efficacy of preclinical evaluation.

The hollow fiber assay for drug responsiveness in the Ewing's sarcoma family of tumors.

Objective: To investigate the use of the National Cancer Institute's hollow fiber assay (HFA) to evaluate and prioritize novel treatment strategies for clinical trials in the Ewing's sarcoma family of tumors (ESFT).

Study Design: The growth and morphology of ESFT cell lines in hollow fibers (HFs) was characterized in vitro and in vivo. Reliability and reproducibility were evaluated using doxorubicin.

Polar, functionalized guanine-O6 derivatives resistant to repair by O6-alkylguanine-DNA alkyltransferase: implications for the design of DNA-modifying drugs.

The protein O6-alkylguanine-DNA alkyltransferase (Atase) is responsible for the repair of DNA lesions generated by several clinically important anti-cancer drugs; this is manifest as active resistance in those cancer cell lines proficient in Atase expression. Novel O6-substituted guanine analogues have been synthesized, bearing acidic, basic and hydrogen bonding functional groups. In contrast to existing O6-modified purine analogues, such as methyl or benzyl, the new compounds were found to resist repair by Atase even when tested at concentrations much higher than O6-benzylguanine, a well-established Atase substrate active both in vitro and in vivo.

Heparin octasaccharides inhibit angiogenesis in vivo.

Background: In previous experiments, we showed that heparin oligosaccharides inhibit the angiogenic cytokine fibroblast growth factor-2. Here, we present the first in vivo study of size-fractionated heparin oligosaccharides in four models of angiogenesis that are progressively less dependent on fibroblast growth factor-2.

Experimental Design: Heparin oligosaccharides were prepared using size-exclusion gel filtration chromatography and characterized through depolymerization and strong anion exchange high-performance liquid chromatography.

Antineoplastic agents. 509: synthesis of fluorcombstatin phosphate and related 3-halostilbenes(1).

The present SAR study of combretastatin A-3 (3a) focused on replacement of the 3-hydroxyl group by a series of halogens. That approach with Z-stilbenes resulted in greatly enhanced (>10-100-fold) cancer cell growth inhibition against a panel of human cancer cell lines and the murine P388 lymphocytic leukemia cell line. Synthesis of the 3-fluoro-Z-stilbene designated fluorcombstatin (11a) and its potassium 3'-O-phosphate derivative (16c) by the route 7 --> 8a --> 11a --> 14 --> 16c illustrates the general synthetic pathway.

Expression of matrix metalloproteinase-10 in human bladder transitional cell carcinoma.

Objectives: To analyze matrix metalloproteinase-10 (MMP-10) expression in transitional cell carcinoma (TCC) of the bladder, evaluate the correlations between MMP-10 protein expression and clinicopathologic parameters, and address the viability of MMP-10 as a therapeutic target for TCC. MMP-mediated degradation of the extracellular matrix is an important factor in the pathogenesis of tumorigenesis and metastasis.

Methods: Using immunohistochemistry, the expression of MMP-10 was assessed using both tissue microarrays and whole sections of archival tissue specimens representative of all grades and stages of human bladder TCC (n = 60).

MMP-10 is overexpressed, proteolytically active, and a potential target for therapeutic intervention in human lung carcinomas.

Matrix metalloproteinase (MMP)-mediated degradation of the extracellular matrix is a major factor for tumor development and expansion. This study analysed MMP-10 protein expression and activity in human lung tumors of various grade, stage, and type to address the relationship between MMP-10 and tumor characteristics and to evaluate MMP-10 as a therapeutic target in non small cell lung carcinoma (NSCLC). Unlike the majority of MMPs, MMP-10 was located in the tumor mass as opposed to tumor stroma.

50 years of preclinical anticancer drug screening: empirical to target-driven approaches.

The number of anticancer agents that fail in the clinic far outweighs those considered effective, suggesting that the selection procedure for progression of molecules into the clinic requires improvement. The value of any preclinical model will ultimately depend on its ability to accurately predict clinical response. This review focuses on the major contributions of preclinical screening models to anticancer drug development over the past 50 years.

Differentiation and definition of vascular-targeted therapies.

The therapeutic potential of targeting the tumor vascular supply is now widely recognized. Intense research and development activity has resulted in a variety of investigational agents, a number of which are currently in clinical development. As these novel agents are quite distinct from the cytotoxic drugs conventionally used in the treatment of solid tumors, it will be particularly important to ensure early differentiation of these vascular-targeted therapies in order to encourage widespread understanding of their potential benefits and application in the clinic.

In vitro, in vivo, and in silico analyses of the antitumor activity of 2-(4-amino-3-methylphenyl)-5-fluorobenzothiazoles.

Phortress is a novel, potent, and selective experimental antitumor agent. Its mechanism of action involves induction of CYP1A1-catalyzed biotransformation of 2-(4-amino-3-methylphenyl)-5-fluorobenzothiazole (5F 203) to generate electrophilic species, which covalently bind to DNA, exacting lethal damage to sensitive tumor cells, in vitro and in vivo. Herein, we investigate the effects of DNA adduct formation on cellular DNA integrity and progression through cell cycle and examine whether a relevant pharmacodynamic end point may be exploited to probe the clinical mechanism of action of Phortress and predict tumor response.

Secretory phospholipase A2 as a tumor-specific trigger for targeted delivery of a novel class of liposomal prodrug anticancer etherlipids.

The use of many common clinically relevant chemotherapeutics is often limited due to insufficient delivery to the tumor and dose-limiting systemic toxicities. Therefore, therapeutics that specifically target tumor cells and are nontoxic to normal cells are required. Here, we report the development of a novel class of liposomes composed of lipid prodrugs, which use the increased secretory phospholipase A2 type IIA (sPLA2) activity of the tumor microenvironment as a trigger for the release of anticancer etherlipids (AEL).

Characterization of the hollow fiber assay for the determination of microtubule disruption in vivo.

Purpose: The hollow fiber assay is used successfully as a routine in vivo screening model to quantitatively define anticancer activity by the National Cancer Institute. This study investigates whether the hollow fiber assay can be used as a short-term in vivo model to demonstrate specific pharmacodynamic end points, namely microtubule and cell cycle disruption.

Experimental Design: The growth of A549 cells was characterized within hollow fibers over 5 days in vivo at both subcutaneous (s.

In-vitro cytotoxic activities of the major bromophenols of the red alga Polysiphonia lanosa and some novel synthetic isomers.

Bioassay-guided fractionation was applied to the cytotoxic chloroform fraction of the red alga Polysiphonia lanosa. The major compounds of the most active fraction were identified using GLC-MS analysis as lanosol (1), methyl, ethyl, and n-propyl ethers of lanosol (1a, 1b, and 1c, respectively), and aldehyde of lanosol (2), although 1b appears to be an artifact arising during the fractionation procedure. These compounds and other known bromophenols were synthesized in addition to four novel isomers (3, 3a-c).

Temporal evaluation of methionine synthase and related metabolites in the MAC15A mouse adenocarcinoma animal model.

Methionine dependence is unique to cancer cells and defined as the inability to grow in a methionine-deprived environment even if supplemented with the metabolic precursor homocysteine. Cobalamin-dependent methionine synthase (MS) catalyses the formation of methionine and tetrahydrofolate from homocysteine and methyltetrahydrofolate, thus linking the methionine and folate pathways. The apparent altered methionine metabolism in methionine-dependent cancer cells suggests a role for MS, although results to date are conflicting.

Phytochemistry and preliminary biological evaluation of Cyathostemma argenteum, a malaysian plant used traditionally for the treatment of breast cancer.

Bioassay guided fractionation of the roots of Cyathostemma argenteum using the brine shrimp resulted in the isolation of two uncommon flavanones, 2,5-dihydroxy-7-methoxy flavanone 1 and 2,5-dihydroxy-6,7-dimethoxy flavanone 2 while the stem bark yielded the related compounds 5-hydroxy-7-methoxy flavone 3 and 5-hydroxy-6,7-dimethoxy flavone 4. The alkaloids liriodenine 5 and discretamine 6 as well as benzyl benzoate 7 were isolated from the roots and 6 was also isolated from the stembark. In cytotoxicity tests using four human breast cancer cell lines, 1 and 2 were weakly toxic to MCF-7 cells (IC(50) = 19.

The role of p53 in the chemotherapeutic responses to cisplatin, doxorubicin and 5-fluorouracil treatment.

A panel of tumour models used extensively for in vivo evaluation of new drugs was characterised for their p53 status. Basal p53 protein levels were measured by immunodetection on both formalin-fixed tumour tissue and from protein extracts of fresh tumours. High levels of nuclear-specific staining, indicative of p53 mutation, was seen in 15/25 tumours, with the remainder showing intermittent or no staining.

Cytochrome P450 1B1 (CYP1B1) is overexpressed in human colon adenocarcinomas relative to normal colon: implications for drug development.

The cytochrome P450 family of enzymes is involved in the Phase I metabolism of a wide variety of compounds. Although generally involved with detoxification, overexpression of one family member, cytochrome P450 1B1 (CYP1B1), has been associated with human epithelial tumors. As such, CYP1B1 was hypothesized to be a novel target for the development of anticancer therapies.

An introduction to telomeres and telomerase.

It is now more than a dozen years since the enzyme telomerase was discovered, and since that time, key studies have characterized the structural components of the enzyme and the associated telomeric proteins. Since the original discovery of telomerase, a clear association with cancer has been demonstrated. In normal somatic cells the telomeres at the ends of chromosomes shorten with every cell division, whereas in cancer cells telomere length is often maintained by reactivation of the enzyme telomerase.

Preclinical evaluation of amino acid prodrugs of novel antitumor 2-(4-amino-3-methylphenyl)benzothiazoles.

Novel 2-(4-aminophenyl)benzothiazoles (e.g., compounds 1 and 2) possess highly selective, potent antitumor properties in vitro and in vivo.