Explore the vast range of titles available.

Animal experiments remain essential to understand the fundamental mechanisms underpinning malignancy and to discover improved methods to prevent, diagnose and treat cancer. Excellent standards of animal care are fully consistent with the conduct of high quality cancer research. Here we provide updated guidelines on the welfare and use of animals in cancer research. All experiments should incorporate the 3Rs: replacement, reduction and refinement. Focusing on animal welfare, we present recommendations on all aspects of cancer research, including: study design, statistics and pilot studies; choice of tumour models (e.g., genetically engineered, orthotopic and metastatic); therapy (including drugs and radiation); imaging (covering techniques, anaesthesia and restraint); humane endpoints (including tumour burden and site); and publication of best practice.

2-(4-Aminophenyl)benzothiazoles represent a potent and highly selective class of antitumour agent. In vitro , sensitive carcinoma cells deplete 2-(4-aminophenyl)benzothiazoles from nutrient media; cytochrome P450 1A1 activity, critical for execution of antitumour activity, and protein expression are powerfully induced. 2-(4-Amino-3-methylphenyl)benzothiazole-derived covalent binding to cytochrome P450 1A1 is reduced by glutathione, suggesting 1A1-dependent production of a reactive electrophilic species. In vitro , 2-(4-aminophenyl)benzothiazole-generated DNA adducts form in sensitive tumour cells only. At concentrations >100 n M , adducts were detected in DNA of MCF-7 cells treated with 2-(4-amino-3-methylphenyl)-5-fluorobenzothiazole (5F 203). 5F 203 (1  μ M ) led to the formation of one major and a number of minor adducts. However, treatment of cells with 10  μ M 5F 203 resulted in the emergence of a new dominant adduct. Adducts accumulated steadily within DNA of MCF-7 cells exposed to 1  μ M 5F 203 between 2 and 24 h. Concentrations of the lysylamide prodrug of 5F 203 (Phortress) ≥100 n M generated adducts in the DNA of sensitive MCF-7 and IGROV-1 ovarian cells. At 1  μ M , one major Phortress-derived DNA adduct was detected in these two sensitive phenotypes; 10  μ M Phortress led to the emergence of an additional major adduct detected in the DNA of MCF-7 cells. Inherently resistant MDA-MB-435 breast carcinoma cells incurred no DNA damage upon exposure to Phortress (⩽10  μ M , 24 h). In vivo , DNA adducts accumulated within sensitive ovarian IGROV-1 and breast MCF-7 xenografts 24 h after treatment of mice with Phortress (20 mg kg −1 ). Moreover, Phortress-derived DNA adduct generation distinguished sensitive MCF-7 tumours from inherently resistant MDA-MB-435 xenografts implanted in opposite flanks of the same mouse.

AQ4 (1,4-Bis-{[2-(dimethylamino-N-oxide)ethyl]amino}5,8-dihydroxyanthracene-9, 10-dione) is a prodrug designed to be excluded from cell nuclei until bioreduced in hypoxic cells to AQ4, a DNA intercalator and topoisomerase II poison. Thus, AQ4N is a highly selective bioreductive drug that is activated in, and is preferentially toxic to, hypoxic cells in tumours. Five murine tumours (MAC16, MAC26, NT, SCCVII and RIF-1) have been used to investigate the anti-tumour effects of AQ4N. In only one tumour (MAC16) was AQ4N shown to be active as a single agent. However, when combined with methods to increase the hypoxic tumour fraction in RIF-1 (by physical clamping) and MAC26 tumours (using hydralazine) there was a substantial enhancement in anti-tumour effect. Notably, RIF-1 tumours treated with AQ4N (250 mg kg –1 ) followed 15 min later by physically occluding the blood supply to the tumour for 90 min, resulted in a 13-fold increase in growth delay. When combined with radiation or chemotherapy, AQ4N substantially increased the effectiveness of these modalities in a range of in vivo model systems. AQ4N potentiates the action of radiation in both a drug and radiation dose-dependent manner. Further the enhancement observed is schedule-independent with AQ4N giving similar effects when given at any time within 16 h before or after the radiation treatment. In combination with chemotherapy it is shown that AQ4N potentiates the activity of cyclophosphamide, cisplatin and thiotepa. Both the chemotherapeutic drugs and AQ4N are given at doses which individually are close to their estimated maximum tolerated dose (data not included) which provides indirect evidence that in the combination chemotherapy experiments there is some tumour selectivity in the enhanced action of the drugs.

The indolequinone EO9 demonstrated good preclinical activity but failed to show clinical efficacy against a range of tumours following intravenous drug administration. A significant factor in EO9's failure in the clinic has been attributed to its rapid pharmacokinetic elimination resulting in poor drug delivery to tumours. Intravesical administration of EO9 would circumvent the problem of drug delivery to tumours and the principal objective of this study is to determine whether or not bladder tumours have elevated levels of the enzyme NQO1 (NAD(P)H:quinone oxidoreductase) which plays a key role in activating EO9 under aerobic conditions. Elevated NQO1 levels in human bladder tumour tissue exist in a subset of patients as measured by both immunohistochemical and enzymatic assays. In a panel of human tumour cell lines, EO9 is selectively toxic towards NQO1 rich cell lines under aerobic conditions and potency can be enhanced by reducing extracellular pH. These studies suggest that a subset of bladder cancer patients exist whose tumours possess the appropriate biochemical machinery required to activate EO9. Administration of EO9 in an acidic vehicle could be employed to reduce possible systemic toxicity as any drug absorbed into the blood stream would become relatively inactive due to an increase in pH. © 2001 Cancer Research Campaign http://www.bjcancer.com

Telomerase, a ribonucleoprotein enzyme, has been found in immortalized but not in most somatic adult human tissues, and thus emerged as a novel target for cancer chemotherapy. However, its usefulness could still be limited by normal tissue toxicity. This study compares enzyme activity in tissues and tumours in conventional in vivo models and human biopsy material, specifically normal human liver, with a view to determining the therapeutic potential of anti-telomerase therapy. The telomeric repeat amplification protocol (TRAP assay) was used to measure enzyme activity and levels were semiquantified by assaying equal concentrations of cellular protein. Telomerase activity was high in the murine embryonic stem cell line CGR8.8, WRL 68 human embryo liver cells, testis, ovary and liver of adult mouse and rat. Low activity was detected in normal human liver, marmoset and pig liver. Very low enzyme activity was seen in mouse, rat and marmoset bone marrow, brain or skin; no activity could be detected in mammalian lung and heart. On the contrary, all 30 human and murine malignant tissues studied showed high to moderate enzyme levels. However, activity found in murine liver was often higher than in tumour, e.g. in the transplantable adenocarcinoma of the colon MAC16. Our findings indicate that telomerase is present not only in murine but also in other normal mammalian tissues such as liver, and that this activity might result from the presence of somatic stem cells. In view of this, the role of telomerase as a potential selective target for therapy needs further investigation. Furthermore, the understanding of regulatory pathways of this enzyme and the selection of screening models will be critical.

Human breast cancer cell lines are required as models for use in the understanding of breast carcinoma, and for improving the ability of cell screens to detect appropriate anti-cancer agents. Four human breast cancer cell lines (MT-1, MaTu. MT-3 and MC4000) were established from human tumour xenografts grown in nude mice. All the lines were shown to be of human origin by karyotype analysis, were epithelial in morphology by both light and electron microscopy, were positive for cytokeratin 18, and were free from mycoplasma, bacterial, yeast and fungal contamination. All of the new lines were shown to be ER and PgR negative, while using the same procedures (i.e. radioligand binding and immunohistochemical staining) the positive control cell line MCF-7 was shown to be positive. MaTu had been previously reported as ER and PgR positive in vivo and it may be that this characteristic had been lost due to in vitro selection pressures. The growth rates of all the new breast cancer cell lines were similar and within the limits required for incorporation into a panel for screening anti-cancer drugs by a microtetrazolium based, colorimetric growth inhibition assay. Three of the lines (MT-1. MaTu and MC4000) were also able to grow into macroscopic colonies for use in a non-agar clonogenic assay. In addition, both MT-1 and MaTu formed spheroids and were clonogenic in soft-agar. The new lines demonstrated a wide range of sensitivities to anticancer agents commonly used in the treatment of breast cancer, and together with their corresponding xenografts are providing additional systems for the evaluation of new compounds.

C1311 is the most active member of a new series of rationally designed anti-cancer agents, the imidazoacridinones, which has shown promising pre-clinical anti-tumour activity in vitro and in vivo against a variety of human colon cancers and is a strong candidate for clinical trials. Data are not available on the pharmacokinetic properties of this compound; therefore, the main aim of this project was to study the plasma pharmacokinetics and tissue and tumour distribution of C1311 in mice and to assess, prior to potential clinical application, whether these pharmacokinetics were linear with respect to the dose. The distribution of C1311 in whole blood was also studied. NMRI or NCR-Nu mice were used throughout the study. C1311 was given i.p. at doses of 15, 50, 100 and (the maximum tolerated dose, (MTD) 150 mg kg(-l) i.p. Plasma, tissue and tumour levels were monitored over a 24-h period using high-performance liquid chromatography (HPLC) with fluorescence detection. The distribution of C1311 in murine and human whole blood was studied using both HPLC and fluorescence microscopy. C1311 was quickly cleared from the plasma (47410 ml min kg(-1)) and rapidly distributed into the tissues at all doses. Tissue-to-plasma ratios were large, ranging from 8 in the liver (15 mg kg(-l)) to 600 (50 mg kg(-1)) in the spleen. Overall concentrations were ranked in the order of plasma << liver < kidney < fat < small intestine < spleen. Tumour concentrations were similar to those measured in the liver and kidney, with AUCs being 186 (MAC15A) and 94.4 microg h ml(-l)(HT-29). Plasma pharmacokinetics were linear at doses of 15-100 mg kg(-1), but disproportionate increases were seen in plasma and tissue concentrations at doses above 100 mg kg(-l). C1311 distributed unevenly in both mouse and human blood, with higher concentrations occurring in the cellular fraction than in plasma. Nucleated cells accounted for a large proportion of this localised drug. In conclusion, C1311 is quickly cleared from the plasma and rapidly distributed into the tissues, with tissue concentrations being far higher than plasma levels. The plasma pharmacokinetics are linear up to but not above doses of 100 mg kg(-1). Concentrations of C1311 are greater in the cellular fraction of the blood than in the plasma, with disproportionately high concentrations occurring in the nucleated fraction.

The development of agents that target tumour vasculature is ultimately dependent on the availability of appropriate preclinical screening assays. Several quantitative angiogenesis assays exist, each with its own unique characteristics and disadvantages. In this review we discuss some of the commonly used assays, their methodological pitfalls and current use. The corneal micropocket and the CAM assay are well established. However, the matrix-implant assays have the potential advantage of replicating the hypoxic tumour microenvironment, thus making them suitable for the study of tumour angiogenesis. The ideal quantitative angiogenesis assay does not exist and the use of two complimentary quantitative assays, such as a matrix implant assay and a microcirculatory preparation like the CAM or corneal micropocket assay, provides the best compromise. Newer models like the hollow-fibre assay are being developed and older ones refined. Assay systems should reflect distinct disease processes. Thus it is appropriate to develop assays that study exclusively pro- or anti-angiogenic compounds or anti-vascular agents. Criticisms of currently available screening systems are that the predictive value of current screening systems remains to be established as anti-angiogenic agents are still in clinical development. Anti-angiogenic agents are likely to be most effective as chronic therapy for remission maintenance in the metastatic setting or as adjuvant therapy in patients at high risk of relapse, an important clinical aspect not addressed in animal models of tumour angiogenesis. Histological analysis still provides the most detailed information on in vivo angiogenesis. However, angiogenesis is a dynamic process and assays that permit continuous monitoring of the angiogenic response and provide information on the physiological characteristics of new vessels will be distinctly advantageous over older systems. The development of non-invasive techniques for quantitation of angiogenesis will greatly facilitate this process.

SYNOPSIS: Tobacco cessation programs have variable success rates and often employ use of multiple strategies, including behavioral counseling and pharmaceutical treatments. This study investigates the use of N-acetylcysteine in combination with group behavioral therapy as a treatment for tobacco use disorder resistant to first-line smoking cessation treatments.