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Biomedical subjects

D J Kerr

Publications and source records attributed to D J Kerr.

At least 19 recordsLinked to original sources
PubMed1997

Simultaneous gas chromatographic-mass spectrophotometric determination of alpha-fluoro-beta-alanine and 5-fluorouracil in plasma.

A gas chromatographic-mass spectrometric (GC-MS) method is reported for simultaneous determination of alpha-fluoro-beta-alanine (FBA), the major end metabolite of 5-fluorouracil (5-FU), and 5-FU in plasma samples isolated from cancer patients. 5-Chlorouracil (5-CIU, 1 micrograms/ml) is added to samples as an internal standard. The method relies on protein precipitation of the plasma sample followed by derivatisation with pentafluorobenzyl bromide. Following sample purification with Sep-pak C18 columns the derivatives are analysed by GC-MS, with FBA, 5-FU and 5-CIU being determined at 36.96-37.03, 46.91-46.98 and 51.99-52.13 min, respectively. The ions measured in each case had m/z of 390, 490 and 506, respectively. The method showed good reproducibility with coefficients of variation between 3 and 10%, with a detection limit of < 1 ng/ml for 5-FU and < 5 ng FBA/ml plasma. The possibility of sensitive determination of FBA without the use of radioisotopes should permit routine estimation of rates of 5-FU metabolism in individual patients.

Antimetabolites, Antineoplastic↗
PubMed1996

CD40-induced growth inhibition in epithelial cells is mimicked by Epstein-Barr Virus-encoded LMP1: involvement of TRAF3 as a common mediator.

CD40, a member of the tumour necrosis factor receptor family, is expressed on the surface of B lymphocytes where its ligation provides a potent survival signal. CD40 is also expressed in basal epithelial cells and in a number of different carcinomas where its function remains unknown. We observed that contrary to the studies in normal B cells, CD40 ligation in carcinoma cell lines and in normal primary epithelial cells resulted in growth inhibition and enhanced susceptibility to apoptosis induced by anti-neoplastic drugs, TNF-alpha, Fas and ceramide. This effect was also observed in CD40-transfected Rat-1 fibroblasts. The expression of Bcl-2 did not affect growth inhibition induced by CD40 ligation in epithelial cells but the Epstein - Barr Virus-encoded latent membrane protein 1 (LMP1) blocked the effect. Whilst transient expression of LMP-1 resulted in the inhibition of epithelial cell growth, this effect was not observed with a LMP1 mutant lacking the binding domain for TRAF3, a protein which may mediate signal transduction by interacting with the cytoplasmic domains of both CD40 and LMP1. Transient expression of TRAF3 also inhibited epithelial cell growth, whilst expression of a dominant-negative TRAF3 partially blocked the inhibitory effect of CD40 ligation and of transient LMP1 expression. These results suggest that CD40 regulates epithelial cell growth in a manner mimicked by LMP1 and implicate TRAF3 as a common mediator in the transduction of the growth inhibitory signals generated via the CD40 and LMP1 pathways.

Animals↗
PubMed1996

The prognostic significance of Bcl-2 and p53 expression in ovarian carcinoma.

Advanced ovarian cancer is characterized by poor prognosis and the development of resistance to chemotherapy. We have found that Bcl-2 and p53, two proteins implicated in the control of apoptosis, are differently expressed in the ovarian cell line A2780 and its cisplatin-resistant variant 2780CP, with the resistant line overexpressing both proteins. Transfection of the A2780 cells with a Bcl-2- or p53-expressing plasmid increases resistance to various drugs, including cisplatin, suggesting that Bcl-2 and p53 expression may influence the sensitivity of ovarian cancer cell lines to chemotherapy. Expression of these two proteins in vivo was determined by immunohistochemical staining of ovarian tumor biopsies from 70 patients. We found that Bcl-2 and p53 were expressed in 57 and 61% of specimens examined, respectively. Both p53 and Bcl-2 were found to be independent prognostic indicators of survival in ovarian cancer. Survival was poorer in patients with tumors expressing high levels of p53, whereas expression of Bcl-2 was associated with improved survival.

Drug Resistance, Neoplasm↗
PubMed1996

Is intra-arterial chemotherapy worthwhile in the treatment of patients with unresectable hepatic colorectal cancer metastases?

Regional chemotherapy, from a theoretical and pharmacological stand point, would seem to offer significant advantage over systemic therapy for the treatment of hepatic metastatic colorectal cancer patients. Clinical experience has shown us that the technique itself is fraught with practical problems, but over the years, specialist centres have learned to overcome many of these, making the technique safer and minimising the possibility of complications and toxicity. As a consequence, there is no doubt that high response rates can be achieved with HAI fluoropyrimidines. However, randomised data have only been obtained from small numbers of patients in suboptimally designed trials and, to date, true patient benefit in terms of either survival or quality of life has not been adequately demonstrated. In parallel with the U.S. Intergroup study, the U.K.-based MRC phase III clinical trial of regional versus systemic 5-FU/FA warrants urgent support and we would welcome collaboration with interested European and American centres. The outcome of this trial will fully define the role of HAI chemotherapy in the management of unresectable hepatic metastatic colorectal cancer, in the context of modern, modulated 5-FU.

Antineoplastic Agents↗
PubMed1996

Delivering cancer care: a model from the West Midlands.

It would seem that time, tide and wind are favourably set for a shift in the organisation of cancer services. Let us test the hypotheses outlined in this brief paper and see if these changes will bring about demonstrable benefit.

Delivery of Health Care↗
PubMed1996

Prolonged intraperitoneal infusion of 5-fluorouracil using a novel carrier solution.

A novel peritoneal carrier solution, Icodextrin 20 (7.5%), has allowed exploration of prolonged, intraperitoneal (i.p.) infusion of the cytotoxic drug 5-fluorouracil (5-FU). A phase I and pharmacokinetic study was performed to determine the toxicities and maximum tolerated dose of prolonged and continuous intraperitoneal 5-FU in patients with peritoneal carcinomatosis. Seventeen patients were entered into this study. Each patient had a Tenckhoff catheter placed into the peritoneal cavity under general anaesthetic. After initial flushing and gradual increase in exchange volumes with Icodextrin 20, 5-FU was administered daily from Monday to Friday, 50% as a bolus in the exchange bag and 50% in an elastomeric infusor device delivering continuous 5-FU to the peritoneal cavity at 2 ml h-1. Treatment was continued for 12 weeks or until intolerable toxicity developed. Abdominal pain and infective peritonitis proved to be the main dose-limiting toxicities. Initial problems with infective peritonitis were overcome by redesign of the delivery system, and it proved possible to deliver 300 mg m-2 5-FU daily (5 days per week) for 12 weeks. Pharmacokinetic studies showed i.p. steady-state 5-FU concentrations (mean 47 500 ng ml-1) that were > 1000-fold higher than systemic venous levels (mean 30 ng ml-1).

Adult↗
PubMed1996

A pilot study of combination therapy with interferon-alpha-2a and 5-fluorouracil in metastatic carcinoid and malignant endocrine pancreatic tumours.

BACKGROUND: In view of the encouraging single agent response rates to interferon and 5-fluorouracil (5-FU) in malignant carcinoid and endocrine pancreatic tumours and the theoretical benefits of combination therapy with 5-FU and interferon in other tumours a study was designed to look at the feasibility of this combination, given for 12 months, in these tumours. PATIENTS AND METHODS: Patients were treated with 5-FU 750 mg/m2 by intravenous bolus every week and 3 Mega Units of recombinant interferon-alpha-2a subcutaneously 3 times per week increasing, as tolerated, to 6 then 9 MU. Fifteen patients were entered into the study. RESULTS: One patient died suddenly of an unrelated illness and is not assessed. None of the remaining 14 patients had radiological evidence of response to treatment, although 6 had stable disease lasting for 7 to 64 weeks (median 40 weeks). Two patients did have biochemical evidence of a response, i.e., a 50% reduction in baseline urinary 5HIAA for 26 and 52 weeks. Treatment toxicity was significant. Six patients stopped treatment prematurely because of either nausea and/or diarrhoea. Overall treatment duration ranged from 4 to 64 weeks (median 7.5 weeks). CONCLUSION: Overall we found the treatment to be disappointing in terms of tolerance and response rate and do not recommend its use in malignant carcinoid or endocrine pancreatic tumours.

Adult↗
PubMed1996

Randomized trial assessing the addition of interferon alpha-2a to fluorouracil and leucovorin in advanced colorectal cancer. Colorectal Cancer Working Party of the United Kingdom Medical Research Council.

PURPOSE: To determine the effects of interferon alpha-2a (IFN alpha) on the efficacy and toxicity of fluorouracil (FUra) and leucovorin (LV) in patients with advanced colorectal cancer. PATIENTS AND METHODS: Two hundred sixty chemotherapy-naive patients were randomized to FUra/LV alone or FUra/LV plus IFN alpha. All patients received: LV 200 mg/m2 intravenous (IV) infusion over 2 hours, then FUra 400 mg/m2 i.v. bolus plus 400 mg/m2 i.v. infusion over 22 hours, all repeated on day 2. Treatment was every 2 weeks for up to 12 cycles. Patients randomized to IFN alpha received 6 x 10(6) IU subcutaneously every 48 hours throughout. Objective response (OR) and toxicity were assessed conventionally; in addition, palliative benefit and adverse effects were assessed using quality-of-life (QoL) questionnaires. RESULTS: There were no differences in OR rate, progression-free survival, or overall survival. OR rates in assessable patients were as follows: FUra/LV alone (n = 104), complete or partial response (OR) = 27%, no change (NC) = 34%; FUra/LV/IFN alpha (n = 101), OR = 28%, NC = 30%. Median survival was 10 months in both arms. Dose-limiting FUra toxicities were not significantly increased by co-administration of IFN alpha, and the delivered FUra dose-intensity was not significantly reduced. However, QoL was adversely affected: patients on IFN alpha were less likely to report improvement in pretreatment physical and psychologic symptoms, and more likely to report new or worsening symptoms. CONCLUSION: IFN alpha, at a dose that impaired QoL, did not improve the efficacy of FUra/LV. The power of this trial is sufficient to exclude with 95% confidence a benefit of 15% in OR or 10 weeks in median survival. Accordingly, we cannot recommend the use of IFN alpha as a clinical modulator of FUra/LV in the treatment of advanced colorectal cancer.

Adult↗
PubMed1996

Intra-hepatic arterial drug delivery.

In this review, the pharmacokinetic rationale for hepatic arterial drug therapy is discussed, along with techniques that have been developed in order to try to enhance the regional advantage accrued from this route of administration. Clinical trials of hepatic arterial therapy in patients with primary hepatocellular carcinoma and with liver metastases from colorectal carcinoma are discussed. Although clinical response rates are significantly better with regional as compared with systemic therapy, survival is not prolonged. This is mainly due to the development of extrahepatic metastases. A treatment strategy using high dose hepatic arterial 5-fluorouracil (5-FU) infusion with the deliberate aim of achieving maximum tolerated systemic drug levels has entered phase III clinical trial. Monitoring of in vivo tumour pharmacokinetics using 19F magnetic resonance spectroscopy and 18F-5-FU positron emission tomography (PET) demonstrate elegantly how target drug uptake may be assessed. We plan to use PET to monitor intra-tumoral viral transduction and 5-flucytosine conversion rates to active 5-FU in our hepatic arterial pro-drug gene therapy programme soon to enter clinical trial.

Antimetabolites, Antineoplastic↗
PubMed1996

Vascular endothelial growth factor stimulates protein kinase C-dependent phospholipase D activity in endothelial cells.

Many tumors produce vascular endothelial growth factor (VEGF), a paracrine factor acting selectively on endothelial cells. VEGF has many effects on cultured endothelial cells and mediates angiogenesis and enhanced vascular permeability in vivo. The endothelial signal transduction pathways of VEGF represent novel targets for cancer therapy because they are readily accessible to systemically administered drugs. We have examined VEGF-stimulated signals generated in HUVEC to identify potential targets for therapeutic intervention. The transphosphatidylation reaction has been used to monitor phospholipase D (PLD) activity; total inositol phosphates have been measured after prelabeling of cells with [3H]myoinositol; and intracellular free calcium has been measured using Fura-2 fluorescence. After HUVEC-stimulation with VEGF, there is an early influx of calcium (maximal by 100 seconds) followed by activation of PLD (half maximal by 100 seconds, EC50 70 pm). The PLD activity was inhibited by reducing extracellular calcium (150 nM, 50% inhibition), exposure to 12-O-tetradecanoylphorbol 13 acetate (200 nM, 24 hours, 100% inhibition), Roche 31,8220 (10 microM, 15 minutes, 72% inhibition), or genestein (100 microM, 30 minutes, 56% inhibition), which suggests a dependence on both protein kinase C and tyrosine phosphorylation. Activation of phospholipase C-catalyzed hydrolysis of phosphatidylinositol-4,5-bisphosphate was inferred from the production of inositol phosphates, although this response was slower (half maximal by 3 minutes). The phospholipase C activity was also dependent on influx of calcium and was partially inhibited by low (150 nM) extracellular calcium. PLD may be involved in mediating a number of endothelial responses to tumor-secreted VEGF, notably cytoskeleton-dependent effects such as the cell migration involved in angiogenesis. This signal transduction pathway could represent an accessible and vulnerable target for cancer therapeutic intervention and has the novelty of being located within normal cells rather than tumor cells.

Calcium↗
PubMed1995

Melanoma cell lines express VEGF receptor KDR and respond to exogenously added VEGF.

Tumour-secreted vascular endothelial growth factor (VEGF) exerts a number of effects which are important in tumour pathology, including stimulation of angiogenesis and permeabilisation of tumour-associated vasculature. In this study we have examined the possibility that VEGF may also play an autocrine role in tumour growth. Using reverse-transcriptase polymerase chain reaction (RT-PCR), the expression of VEGF was found in 15/15 human tumour cell lines examined, while the VEGF receptor KDR was detected only in three melanoma cell lines (MeWo and A375, both wild type and metastatic variant). Exogenously added VEGF (10ng/ml) was able to stimulate up to 40% increased proliferation of A375 M melanoma cells following a 48-h period of quiescence, suggesting that VEGF may indeed play a role in autocrine, as well as paracrine, stimulation of melanoma growth.

Base Sequence↗
PubMed1995

Wortmannin and its structural analogue demethoxyviridin inhibit stimulated phospholipase A2 activity in Swiss 3T3 cells. Wortmannin is not a specific inhibitor of phosphatidylinositol 3-kinase.

Wortmannin and its structural analogue demethoxyviridin (DMV) have been reported to be specific inhibitors of phosphatidylinositol 3-kinase activity. Here we report that these compounds are not as selective as assumed and demonstrate inhibition of bombesin-stimulated phospholipase A2 activity by both wortmannin and DMV with an IC50 (2 nM) which is slightly more potent than the inhibition of insulin-stimulated phosphatidylinositol 3,4,5-trisphosphate generation in these cells (approximately 10nM). While it has not been possible to fully block in vitro phospholipase A2 activity with wortmannin, inhibition cannot be a consequence of inhibition of PI 3-kinase activity since bombesin fails to generate 3-phosphorylated lipids in the intact cell. Therefore, while wortmannin is indeed a PI 3-kinase inhibitor, it is not as specific as previously reported, and experimental conclusions based solely on its use should be treated with caution.

3T3 Cells↗
PubMed1995

The control of apoptosis and drug resistance in ovarian cancer: influence of p53 and Bcl-2.

Modulation of apoptosis may influence resistance to chemotherapy and therefore affect the outcome of cancer treatment. Ovarian cancer, one of the most fatal malignancies in women, is often associated with drug resistance but the cellular pathways contributing to this effect remain obscure. We have found that Bcl-2 and p53, two proteins implicated in the control of apoptosis, are frequently expressed in fresh biopsies of primary ovarian carcinoma. Examination of Bcl-2 and p53 protein levels in pairs of cis-platin sensitive and resistant ovarian cell lines demonstrated that the resistant variants over-express Bcl-2 and/or p53, apparently due to progressive expansion of Bcl-2 and/or p53 positive subpopulations during the in vitro development of resistance. Exogenous expression of Bcl-2 or a temperature sensitive mutant p53 (ts p53) in the ovarian cell line A2780 resulted in protection from drug-induced apoptosis and a delay in drug-mediated S-phase arrest. Interestingly, p53 accumulation in response to DNA damage induced by different agents was significantly delayed and reduced in the Bcl-2 transfectants compared to the control A2780 line, suggesting that Bcl-2 may act upstream of the p53 pathway. Similarly, the induction of Bax mRNA and protein was also found to be delayed in the presence of Bcl-2. Overall, our data provide further evidence for cross-talk between Bcl-2, p53 and Bax and suggest that these genes are important determinants of drug-induced apoptosis thereby modulating resistance to chemotherapy.

Apoptosis↗
PubMed1995

Induction of the c-myc but not the cH-ras promoter by platinum compounds.

The recombinant plasmids p324, p330 and p323 carrying the aminoglycoside phosphotransferase (aph) gene and 5' flanking c-myc sequences linked to the reporter gene chloramphenicol acetyl-transferase (cat) were introduced into the mouse erythroleukaemic cell line F412B2TK- and stable transfectants resistant to geneticin G418 were obtained. The effects of cis-platin and two novel platinum compounds, D19466 (lobaplatin) and D17872, on c-myc promoter regions were studied using a large range of drug concentrations and correlated with cytotoxicity data. It was found that cis-platin and D19466 show a similar pattern of cytotoxicity and activation of c-myc promoter-driven cat gene expression with maximum effect (increased expression of 7.4- and 8.1-fold, respectively) at a concentration of 5 x 10(-5) M, while the less cytotoxic D17872 only slightly activates cat expression at the same concentration. However, when the F412B2TK- cell line was transfected with a plasmid carrying 5' flanking sequences of the c-Hras1 gene with promoter/enhancer function, linked to the cat reporter, no similar inductive effect was observed with any of the platinum drugs used. These data suggest that platinum compounds and possibly other DNA-damaging agents may specifically influence the expression of certain genes.

Animals↗
PubMed1995

Allosteric regulation of [3H]vinblastine binding to P-glycoprotein of MCF-7 ADR cells by dexniguldipine.

Plasma membranes were prepared from the P-glycoprotein expressing human breast cancer cell line MCF-7 ADR. [3H]Vinblastine bound to these membranes saturably with a Bmax of 24 pmol/mg of protein and KD of 23 nM. In contrast, membranes from the parent cells MCF-7 WT, which do not express P-glycoprotein, did not bind [3H]vinblastine with high affinity. Cytotoxics known to be transported by P-glycoprotein inhibited the binding of [3H]vinblastine, as did multidrug reversing agents including the 1,4-dihydropyridine, dexniguldipine-HCl (Ki, 15 nM). In dissociation kinetic experiments, dexniguldipine-HCl accelerated the dissociation of [3H]vinblastine from P-glycoprotein, indicating a negative heterotropic allosteric mechanism of action through a drug binding site distinct from that of vinblastine. Other 1,4-dihydropyridines tested also accelerated [3H]vinblastine dissociation from P-glycoprotein, however, multidrug reversing drugs of different chemical classes, including quinidine, verapamil and cyclosporin A did not. These results suggest that P-glycoprotein of MCF-7 ADR cell membranes possesses at least two drug acceptor sites which are allosterically coupled: receptor site-1 which binds vinca alkaloids, and receptor site-2 which binds 1,4-dihydropyridines such as dexniguldipine-HCl, which had the highest affinity of the tested derivatives.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1995

Determination of quercetin in human plasma using reversed-phase high-performance liquid chromatography.

A method is reported for the measurement of quercetin in human plasma using reversed-phase high-performance liquid chromatography (HPLC). Quercetin and kaempferol (as internal standard) were spiked into plasma samples and extracted using C18 Sep-Pak Light cartridges (efficiency > 85%). Flavonoids were eluted with aqueous acetone (50% v/v, pH 3.5), dried down and redissolved in aqueous acetone (45% v/v, pH 3.5). The increased osmolarity promoted a phase separation and the water-saturated acetone layer, containing the flavonoids, was analysed by HPLC with aqueous acetone mobile phase (45% v/v acetone in 250 mM sodium dihydrogen sulphate. The mixture was adjusted to pH 3.5 with phosphoric acid and used at a flow-rate of 1.0 ml/min) and mu Bondapak C18 column (150 x 3.9 mm I.D., 10 microns particle size). The detection limit (A375 nm) for quercetin in plasma was 0.1 microgram/ml (300 nM). The method also detects metabolites of quercetin, although these are not yet identified.

Chromatography, High Pressure Liquid↗