Search PubMed⌕ Search

Biomedical subjects

D J Kerr

Publications and source records attributed to D J Kerr.

At least 19 recordsLinked to original sources
PubMed2000

Sensitisation of human carcinoma cells to the prodrug CB1954 by adenovirus vector-mediated expression of E. coli nitroreductase.

The enzyme nitroreductase from E. coli can reduce the weak, monofunctional alkylating agent 5-(aziridin-1-yl)-2, 4-dinitrobenzamide (CB1954) to a potent cytotoxic species that generates interstrand crosslinks in DNA. Nitroreductase therefore has potential as a "suicide enzyme" for cancer gene therapy, as cells that express nitroreductase become selectively sensitive to the prodrug CB1954. We have incorporated a nitroreductase expression cassette into a replication-defective adenovirus vector (Ad-CMV-ntr), which allowed efficient gene transfer to SK-OV-3 or IGROV-1 ovarian carcinoma cells. Nitroreductase levels increased in line with multiplicity of infection, and this was reflected in increasing sensitisation of the cells to CB1954, reaching an optimum (approx. 2, 000-fold sensitisation) with 25-50 p.f.u. per cell. Similar Ad-CMV-ntr-dependent sensitisation to CB1954 was seen in 3 of 6 low-passage primary ovarian tumour lines. Cells grown at low-serum concentration to inhibit proliferation remained equally susceptible to the Ad-CMV-ntr-dependent cytotoxicity of CB1954, indicating a distinct advantage over retroviral gene delivery and other popular enzyme-prodrug systems for human tumours with a low rate of cell proliferation. Additionally, cisplatin-resistant cells were sensitised towards CB1954 by Ad-CMV-ntr as efficiently as the parental cells, indicating that the system could be effective in patients with cisplatin-resistant tumours. In a murine xenograft model for disseminated peritoneal carcinomatosis with ascites, treatment of nude mice bearing intraperitoneal SUIT2 tumours with Ad-CMV-ntr and CB1954 almost doubled the median survival from 14 to 26 days (p < 0.0001).

Adenoviridae↗
PubMed2000

Gene therapy strategies for colon cancer.

Colorectal cancer is the second most common cause of cancer mortality in Western countries. Gene therapy represents a novel approach to the treatment of colorectal cancer, and this review addresses the current strategies and ongoing clinical trials, including gene correction, immunomodulatory approaches and virus-directed enzyme-prodrug systems. Although the pre-clinical results for these strategies have been encouraging, clinical trials have not yet reflected these data. However, gene therapy for colorectal cancer is still in the early stages of development, and its potential, particularly in combination with conventional cancer therapies, warrants further investigation.

Animals↗
PubMed2000

Expression of Escherichia coli B nitroreductase in established human tumor xenografts in mice results in potent antitumoral and bystander effects upon systemic administration of the prodrug CB1954.

Expression of the Escherichia coli enzyme nitroreductase (NTR) in mammalian cells enables them to activate the prodrug 5-(aziridin-1-yl)-2,4-dinitrobenzamide (CB1954), leading to interstrand DNA cross-linking and apoptosis in both proliferating and quiescent cells. In the work reported here, we used human hepatocellular carcinoma and squamous carcinoma cell lines constitutively expressing NTR to demonstrate that the ntr/CB1954 system results in potent, long-lasting antitumoral effects in mice. We also demonstrate that this enzyme/prodrug combination results in antitumoral effects in vivo when only a minority of tumor cells express the enzyme, using either cells constitutively expressing NTR or ntr gene delivery in situ.

Animals↗
PubMed1999

High-performance liquid chromatographic method for sensitive determination of the alkylating agent CB1954 in human plasma.

A high-performance liquid chromatography (HPLC) method is described for the measurement of the weak alkylating agent CB1954 in human plasma. CB1954 can be used as an innocuous prodrug designed for activation by bacterial nitroreductases in strategies of gene-directed enzyme-prodrug therapy, and becomes activated to a potent bifunctional alkylating agent. The HPLC method involves precipitation and solvent extraction and uses Mitomycin C (MMC) as an internal standard, with a retention time for MMC of 5.85 +/- 0.015 min, and for CB1954 of 10.72 +/- 0.063 min. The limit of detection for CB1954 is 2.9 ng/ml, and this compares favourably with systems involving direct analysis of plasma (limit of detection 600 ng/ml, approximately). The method is now being used for pharmacokinetic measurements in plasma samples from cancer patients entering phase I clinical trials of CB1954. Results using serial plasma samples from one patient are presented. The patient was treated intravenously with CB1954 (6 mg/m2), and plasma clearance of the drug showed biphasic kinetics with alpha half-life 14.6 min, and beta half-life 170.5 min.

Antineoplastic Agents, Alkylating↗
PubMed1999

Effect of Epstein-Barr virus infection on response to chemotherapy and survival in Hodgkin's disease.

We have analyzed paraffin sections from 190 patients with histologically confirmed Hodgkin's disease (HD) for the presence of Epstein-Barr virus (EBV) using in situ hybridization to detect the EBV-encoded Epstein-Barr virus early RNAs (EBERs) and immunohistochemistry to identify latent membrane protein-1 (LMP1) expression. EBV was present in the tumor cells in 51 HD cases (27%) and was mainly confined to the mixed cellularity and nodular sclerosis subtypes. There was no difference between EBV-positive and EBV-negative HD patients with regard to age, clinical stage, presentation, and the number of alternating chemotherapy cycles of ChIVPP and PABIOE received. The complete remission rate after study chemotherapy was 80% in EBV-positive patients versus 69% in EBV-negative patients (P =.05). The 2-year failure-free survival rate was significantly better for EBV-positive patients when compared with the EBV-negative HD group (P =.02). Although 2-year and 5-year overall survival rates were better for EBV-positive HD patients, the differences were not statistically significant (P =.18 and P =.40, respectively). In conclusion, the results confirm the favorable prognostic value of EBV in the tumor cells of HD patients and suggest important differences in response to chemotherapy between EBV-positive and EBV-negative patients.

Antineoplastic Combined Chemotherapy Protocols↗
PubMed1999

Preliminary clinical study of the distribution of HPMA copolymers bearing doxorubicin and galactosamine.

Galactose-targeted delivery of macromolecules and drug conjugates to asialoglycoprotein receptor (ASGPR) positive cells has been widely documented in animals, although targeting in humans has never been demonstrated. In this study we report the pharmacokinetics and imaging determined in the first patient enrolled in a phase I clinical study of the poly[N-(2-hydroxypropyl)methacrylamide] copolymer bearing doxorubicin and galactosamine, known as PK2. Gradient high performance liquid chromatography (HPLC) evaluation of plasma and urine has been combined with 123I-based imaging to show biphasic clearance of the drug from the plasma (half-lives of 78+/-1 and 990+/-15), and approximately 30% delivery of the drug to the hepatic region, as determined by planar whole body imaging at 24 h. This patient has a multifocal hepatoma, and single photon emission computed tomography (SPECT) analysis showed a ratio of tumour tissue to normal liver uptake of approximately 1:3, at 24 h. On the basis of this patient, effective hepatic targeting can be achieved following an intravenous dose of 20 mg/m2 doxorubicin as PK2, however the therapeutic usefulness of this targeted drug has yet to be established.

Antibiotics, Antineoplastic↗
PubMed1999

Prospective, double-blind, placebo-controlled randomized trial of cimetidine in gastric cancer. British Stomach Cancer Group.

Cimetidine is thought to inhibit suppressor T-lymphocyte function and preliminary evidence from a randomized trial indicated that it might prolong survival for patients with operable and inoperable gastric cancer. The British Stomach Cancer Group conducted a randomized, double-blind, placebo-controlled trial examining the effects of cimetidine (400 mg or 800 mg twice a day) on the survival of patients with early (stages I, II and III: n = 229) and advanced (stages IVa and IVb: n = 201) gastric cancer. The primary end point was death. A total of 442 patients were randomized by 59 consultants in 39 hospitals between February 1990 and March 1995. Log-rank survival analysis was used to assess differences between the groups. Three hundred and forty patients died during the study: 166 (49%) in the cimetidine treatment groups and 174 (51%) in the placebo groups. Median survival for patients receiving cimetidine was 13 months (95% confidence interval (CI) 9-16 months) and 11 months in the placebo arm (95% CI 9-14 months). There was no significant difference in survival between the two treatment groups (P = 0.42) or between different doses of cimetidine tablets (P = 0.46). Five-year survival of those patients randomized to cimetidine was 21% compared to 18% for those patients randomized to placebo. Cimetidine at a dose of 400 mg or 800 mg twice a day does not have a significant influence on the survival of patients with gastric cancer compared to placebo.

Adult↗
PubMed1999

The acridonecarboxamide GF120918 potently reverses P-glycoprotein-mediated resistance in human sarcoma MES-Dx5 cells.

The doxorubicin-selected, P-glycoprotein (P-gp)-expressing human sarcoma cell line MES-Dx5 showed the following levels of resistance relative to the non-P-gp-expressing parental MES-SA cells in a 72 h exposure to cytotoxic drugs: etoposide twofold, doxorubicin ninefold, vinblastine tenfold, taxotere 19-fold and taxol 94-fold. GF120918 potently reversed resistance completely for all drugs. The EC50s of GF120918 to reverse resistance of MES-Dx5 cells were: etoposide 7+/-2 nM, vinblastine 19+/-3 nM, doxorubicin 21+/-6 nM, taxotere 57+/-14 nM and taxol 91+/-23 nM. MES-Dx5 cells exhibited an accumulation deficit relative to the parental MES-SA cells of 35% for [3H]-vinblastine, 20% for [3H]-taxol and [14C]-doxorubicin. The EC50 of GF120918, to reverse the accumulation deficit in MES-Dx5 cells, ranged from 37 to 64 nM for all three radiolabelled cytotoxics. [3H]-vinblastine bound saturably to membranes from MES-Dx5 cells with a KD of 7.8+/-1.4 nM and a Bmax of 5.2+/-1.6 pmol mg(-1) protein. Binding of [3H]-vinblastine to P-gp in MES-Dx5 membranes was inhibited by GF120918 (K = 5+/-1 nM), verapamil (Ki = 660+/-350 nM) and doxorubicin (Ki = 6940+/-2100 nM). Taxol, an allosteric inhibitor of [3H]-vinblastine binding to P-gp, could only displace 40% of [3H]-vinblastine (Ki = 400+/-140 nM). The novel acridonecarboxamide derivative GF120918 potently overcomes P-gp-mediated multidrug resistance in the human sarcoma cell line MES-Dx5. Detailed analysis revealed that five times higher GF120918 concentrations were needed to reverse drug resistance to taxol in the cytotoxicity assay compared to doxorubicin, vinblastine and etoposide. An explanation for this phenomenon had not been found.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1999

Antioxidant effects of isoflavonoids and lignans, and protection against DNA oxidation.

The antioxidant capability of a series of isoflavonoid and lignan compounds in both cellular and cell-free systems has been investigated, and related to structure. Nordihydroguaiaretic acid exhibited a potent antioxidant activity in both HepG2 and MDA-MB-468 cells (IC50 5.3 and 1.1 microM respectively), as determined by inhibition of 2',7'-dichlorofluorescin oxidation via t-BOOH, although no inhibition was observed with other compounds tested in this system. All compounds inhibited the formation of 8-oxodeoxyguanosine in DNA exposed to hydroxyl radicals via gamma irradiation or the Fenton reaction. Whilst almost complete inhibition of gamma irradiation-induced damage was achieved (IC50 ranged from 0.2 to 0.8 microM), inhibition was less pronounced with the Fenton system. The ability of all compounds to interact with DNA (as well as with reactive oxygen and iron) was also demonstrated by scanning UV spectroscopy, suggesting that the compounds may inhibit DNA oxidation at least in part by binding to DNA. Hydroxyl radical-scavenging, iron-chelating and DNA-binding activity of these compounds supports their proposed role as natural cancer-protective agents.

Antioxidants↗
PubMed1999

Intra-arterial 5-fluorouracil and intravenous folinic acid in the treatment of liver metastases from colorectal cancer.

OBJECTIVE: To compare two regimens of intra-arterial chemotherapy for the treatment of hepatic metastases from colorectal cancer. DESIGN: Open study. SETTING: Teaching hospital, UK SUBJECT: 57 patients with unresectable metastases confined to the liver, and an indwelling catheter in the hepatic artery. INTERVENTIONS: The first 33 patients had a 24-hour intra-arterial infusion of 5-fluorouracil (5-FU) 1500 mg/m2, together with folinic acid 200 mg/m2 intravenously for the first and last two hours of the 5-FU infusion. This was repeated at weekly intervals for six weeks followed by a two-week gap before the next cycle. The remaining 24 patients had a two-weekly regimen in which folinic acid 200 mg/m2 was infused intravenously over 2 hours followed by an intra-arterial loading dose of 5-FU 400 mg/m2 over 15 minutes; 5-FU 1600 mg/m2 was then given by intra-arterial infusion over 22 hours. This was repeated on day 2 and then at two-weekly intervals. MAIN OUTCOME MEASURES: Response rate and toxicity. RESULTS: Median follow-up was 21 months, and estimated median survival 19 months. 29 patients (51%) have responded, 5 completely. There are no significant differences between the groups. Sites of progression were liver alone 26 (53%), lung alone 9 (18%), liver and lung 3 (6%), and the remainder in local or regional nodes (n = 7) or bone (n = 4). Six patients experienced WHO grade 3 or 4 toxicity. CONCLUSION: The two regimens have high response rates and cause little systemic toxicity. Intra-arterial chemotherapy for hepatic metastases from colorectal cancer is currently being compared with conventional systemic chemotherapy in a randomised controlled trial.

Adult↗
PubMed1999

Can pharmacokinetic monitoring improve clinical use of fluorouracil?

Fluorouracil is used clinically against a variety of solid tumors. It is a prodrug that undergoes a series of intracellular conversions to active cytotoxic species. There is wide interindividual variability in fluorouracil metabolism; furthermore, it has nonlinear kinetics that make it relatively more difficult to predict plasma concentrations after brief infusions compared with prolonged infusions. There is an increasing body of evidence that relates plasma fluorouracil concentrations to toxicity and effectiveness, and consequently there may be a definable mathematical relationship that describes a 'therapeutic window'. Dose nomograms and pharmacokinetic models based on limited sampling strategies have been developed, as have empirical dose escalation schedules based on multivariate analysis of the determinants of toxicity, The utility of these approaches should be tested in properly powered, prospective, randomised trials.

Age Factors↗
PubMed1999

Virus-directed enzyme prodrug therapy using CB1954.

The virus-directed enzyme prodrug therapy (VDEPT) anti-cancer 'gene therapy' strategy relies on the use of viral vectors for the efficient delivery to tumour cells of a 'suicide gene' encoding an enzyme which converts a non-toxic prodrug to a cytotoxic agent. The prodrug 5-(aziridin-1-yl)-2,4 dinitrobenzamide, CB1954, has been proposed for use in enzyme-prodrug gene therapy systems with the Escherichia coli enzyme nitroreductase (Ntr). Ntr converts CB1954 to 2- and 4-hydroxylamino derivatives, whereupon the non-enzymatic reaction of the 4-hydroxylamino derivative with cellular thio- esters generates a potent cytotoxic bifunctional alkylating agent capable of cross-linking DNA. Ntr delivery has been achieved in vitro using retroviral and adenoviral vectors and confirmed by immunocytochemical demonstration of Ntr expression. The Ntr-expressing cells have been shown to be sensitized to CB1954 by up to 2000-fold. The Ntr-CB1954 system shows effective bystander killing in mixed populations of Ntr-expressing and non-expressing cells treated with CB1954. The efficacy of this enzyme-prodrug approach in model systems compared with other VDEPT approaches demonstrates the feasibility and future promise of this gene therapy strategy.

Alkylating Agents↗
PubMed1998

The effect of cimetidine on the pharmacokinetics of epirubicin in patients with advanced breast cancer: preliminary evidence of a potentially common drug interaction.

Epirubicin is known to be metabolized in the liver. Therefore, drugs such as cimetidine, which inhibit the cytochrome P-450 enzyme system or reduce liver blood flow, may reduce the plasma clearance of epirubicin. In a small study, epirubicin 100 mg/m2 every 3 weeks was administered intravenously to eight patients, who also received oral cimetidine (400 mg b.d. for 7 days starting 5 days before chemotherapy) with either the first or second cycles. Epirubicin pharmacokinetics and liver blood flow (idocyanine green clearance) were assessed at each course. The areas under the plasma concentration time curves (AUCs) were used to compare the systemic exposure to epirubicin and its metabolites with each course. The estimated median percentage increase (95% confidence interval CI) in the AUC with cimetidine were: epirubicin 50% (95% CI -18 to 193, epirubicinol 41% (95% CI 1 to 92). Despite the small numbers studied, the increase in the active metabolite epirubicinol was significant (P < 0.05). These changes in exposure were not explained by reduced cytochrome P-450 activity as the 7-deoxy-doxorubicinol aglycone AUC was not reduced (357% increase: 95% CI 17 to 719) or by a decrease in liver blood flow (17% increase: 95% CI -39 to 104). Cimetidine is likely to be coprescribed or self-administered with epirubicin and therefore clinicians should be aware of this potential interaction.

Administration, Oral↗