Search PubMed⌕ Search

Biomedical subjects

D J Kerr

Publications and source records attributed to D J Kerr.

At least 145 records · Page 8Linked to original sources
PubMed1991

Mitomycin C-loaded microcapsules in the treatment of colorectal liver metastases. Pharmacokinetics of regionally administered particulate chemotherapy.

Microencapsulated mitomycin C has been used for the treatment of intrahepatic tumors in Japan, but there have been no reports of its use in western countries. In this study, the pharmacokinetic profile of intrahepatic arterial mitomycin C microcapsules is reported. Regional mitomycin C was administered to six patients, both in the microencapsulated form and in solution. The clearance (140 +/- 31 1/hour, mean +/- SD) and half-life of drug in plasma (0.39 +/- 0.03 hours), and volume distribution (246 +/- 23 1) were significantly higher, and peak drug concentrations (80 +/- 75 ng/ml) significantly lower with the microencapsulated preparation than with the free drug (clearance, 46 +/- 8 1/hour; half-life, 0.11 +/- 0.02 hours; volume distribution, 33 +/- 4; peak drug concentration, 812 +/- 423 ng/ml), on Student's t testing (P less than 0.05). The results show that very little systemic exposure is associated with the microencapsulated form of mitomycin C. Dose escalation should be feasible without increasing systemic toxicity.

Antineoplastic Agents↗
PubMed1991

Drug metabolism in carcinogenesis and cancer chemotherapy.

Cytotoxic drugs have become invaluable for the clinical oncologist in the treatment of neoplastic disease. Frequently, these therapeutic agents are used in combination in order to combat the heterogeneity imposed by the variable tumor cell biochemistry of the neoplastic cell population. Hence, one could argue polypharmacy has become the rule rather than the exception in cancer chemotherapy. The use of such regimens obviously increases the potential for drug-drug interactions and also may potentiate the effects of interindividual variation in drug metabolism. Altered expression of drug metabolizing enzymes may also predispose certain individuals to cancer through enhanced metabolic activation and decreased detoxication of environmental, dietary and possibly endogenous procarcinogens. Many anticancer drugs can be considered as prodrugs which require metabolic activation to exert their selective cytotoxic effects. Recent molecular and biochemical advances have increased our understanding of the factors which govern the regulation of drug metabolizing enzymes and have improved our knowledge of the metabolism and action of anticancer agents. The aim of this review is not to exhaustively document all the work in the area of drug metabolism in relation to cancer, but to provide a comprehensive update of some of the recent advances in drug metabolism which have helped to rationalize the mechanism of action of some anticancer drugs and which may help to optimize future patient selection for certain novel chemotherapeutic regimens. This review also discusses some of the more recent breakthroughs in the area of carcinogenesis and highlights directions for future studies.

Animals↗
PubMed1991

Multidrug resistance: clinical relevance in haematological malignancies.

Multidrug resistance describes an experimental observation which appears to explain cross-resistance to certain structurally unrelated cytotoxic agents, including anthracyclines, vinca alkaloids and podophyllotoxins. It is now clear that a major factor responsible for its development is increased expression of a membrane glycoprotein--P-glycoprotein, which functions as an energy-dependent efflux pump. Recent data, particularly in haematological malignancies such as acute non-lymphocytic leukaemia, myeloma and non-Hodgkin's lymphoma, indicate that P-glycoprotein may be involved in the development of clinical drug resistance. The potential therefore exists for new therapeutic studies aimed at circumventing resistance which develops through this mechanism, by using modulators, such as verapamil, quinidine and several others, which prevent cellular drug efflux by competitive binding to P-glycoprotein.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1991

Doxorubicin stimulates transcription from the human immunodeficiency virus long terminal repeat sequences.

A recombinant plasmid carrying the long terminal repeat (LTR) of the human immunodeficiency virus 1 (HIV-1) linked to the reporter chloramphenicol acetyl transferase (CAT) gene was stably introduced into rat liver cells. The transfectant cells expressed CAT activity from the HIV LTR. The response to doxorubicin was studied and it was found that at the optimum concentration of 20 micrograms/ml doxorubicin, the expression of CAT from the HIV LTR was stimulated by 65-fold. Our results suggest caution against therapy including doxorubicin in the treatment of AIDS patients.

Animals↗
PubMed1991

Transforming growth factor beta 1 is implicated in the failure of tamoxifen therapy in human breast cancer.

Transforming growth factor-beta 1 (TGF-beta 1) is inhibitory for breast epithelial cells in vitro and treatment of breast cancer cell lines with tamoxifen results in a rise in TGF-beta 1 mRNA expression with associated inhibition of cell growth. To study whether these findings apply in vivo we examined TGF-beta 1 mRNA expression in an oestrogen-dependent mouse xenograft system following systemic treatment of the mice with tamoxifen. In agreement with in vitro studies. TGF-beta 1 mRNA expression was sustained at high levels and associated with a reduction in tumour size. A subsequent study of breast tumour tissue from 56 patients demonstrated high levels of TGF-beta 1 mRNA in 45 of the tumours. High expression was found to correlate with premenopausal status, but not with tumour oestrogen receptor content or other parameters. In a subgroup of 11 patients who had received tamoxifen therapy for 3 to 6 months prior to surgery, unexpectedly high levels of TGF-beta 1 mRNA were demonstrated in tumours increasing in size and unresponsive to tamoxifen. Data from this study indicate that in patients with breast cancer, TGF-beta 1 in the tumour may not behave as in vitro and xenograft studies have suggested. We speculate that failure of tamoxifen therapy may be due to failure of the autocrine inhibitory functions of TGF-beta 1 either alone or in combination with paracrine stimulation of stromal cells or angiogenesis and localised immunosuppression. Further studies of active TGF-beta 1, TGF-beta receptors and the interactions with other growth factors will be required to elucidate the precise role of TGF-beta 1 in human breast cancer and in the failure of tamoxifen therapy.

Adult↗
PubMed1991

Angiotensin II as a potential method of targeting cytotoxic-loaded microspheres in patients with colorectal liver metastases.

Regional chemotherapy is commonly used to treat patients with colorectal liver metastases. However, improvement in survival has still not been demonstrated. Cytotoxic loaded albumin microspheres for arterial administration have been described as a means of improving the the therapeutic index, but their distribution depends upon the prevailing pattern of arterial blood-flow at the time of injection. In this study, the ability of the vasoactive drug angiotensin II to target arterially injected microspheres to colorectal liver metastases is assessed in nine patients using scintigraphic planar and tomographic imaging. The median tumour: normal ratio in nine patients with colorectal liver metastases was 3.4:1 before the administration of angiotensin II. The corresponding ratio after administration of angiotensin II was 7.3:1. The median improvement factor was 1.8 (P less than 0.05). The data suggest that worthwhile tumour targeting can be achieved with angiotensin II in patients with colorectal liver metastases.

Angiotensin II↗
PubMed1991

Regional chemotherapy for inoperable renal carcinoma: a method of targeting therapeutic microspheres to tumour.

Regionally-administered, drug-loaded microspheres have a potential role in the treatment of renal tumours. Vasoactive agents, for example, angiotensin II, may allow selective delivery of microspheres to tumour. The present study defines the regional advantage that may be obtained from angiotensin II by quantifying tumour and normal kidney blood flow using radiolabelled microsphere renal perfusion studies and per-operative laser-doppler flow measurements. Angiotensin II increased microsphere distribution to tumour, relative to normal kidney, by a factor of four. This enhancement was associated with an absolute increase in tumour blood flow.

Angiotensin II↗
PubMed1991

Regional delivery of microspheres to liver metastases: the effects of particle size and concentration on intrahepatic distribution.

There is increasing interest in the use of microspheres, loaded with chemotherapeutic agents, for regional therapy to hepatic metastases. It is necessary to deliver these particles predominately to tumour rather than to normal liver. This study investigates factors influencing the distribution of regionally injected microspheres. Discreet tumour was induced in rats by subcapsular hepatic inoculations of HSN cells. At 20 days, 12.5 microns, 25 microns or 40 microns diameter, radiolabelled albumin microspheres were administered, in various concentrations, via the gastroduodenal artery. Tumour to normal liver microsphere distribution ratios were determined and median values ranged from 0.1 (0.2 mg ml-1 12.5 microns microspheres) to 1.8 (20 mg ml 40 microns microspheres). Concentrated suspensions (20 mg ml-1) of large microspheres (40 microns) produced the most favourable tumour to normal liver distribution ratios. These results not only have implications for the therapeutic administration of microspheres but also for their use in blood-flow studies.

Albumins↗
PubMed1991

Phase I and pharmacokinetic study of D-verapamil and doxorubicin.

The calcium antagonist verapamil (a mixture of D- and L-racemers) is a potent modulator of the multi-drug resistance phenotype in vitro at a concentration of 6 microM. Clinical studies have shown dose-limiting toxicity of hypotension and heart block when plasma levels approach the concentrations active in vitro. Previous data indicate that the D-isomer is less cardioactive than the L-isomer but they appear to be equipotent in reversing drug resistance in vitro. In an attempt to increase plasma verapamil concentrations, we have treated ten patients (total of 27 courses) with oral D-verapamil (DVPM), 150-300 mg 6 h, and doxorubicin i.v. 70 mg m2 q 3 weeks. Hypotension (supine systolic BP less than 100 mmHg or a fall in systolic BP of greater than 30 mmHg) occurred in 5/6 patients at 1200 mg day DVPM, in 1/5 at 800 mg day, and in 1/5 at 600 mg day. PQ prolongation (greater than 0.23 s) was demonstrated in 2/5 patients at 800 mg day DVPM. Plasma levels of DVPM and its active metabolite norverapamil were measured and, combining these, levels of 3-4 microM were achieved at 1200 mg day DVPM; however this dose is likely to lead to unacceptable toxicity in the outpatient setting. Using an oral outpatient schedule of administration, an appropriate dose of DVPM is 800 mg day. This provides a combined plasma level (for VPM and DVPM) of 2-3 microM. If DVPM is to prove useful as a resistance modulator, it may require to be administered intravenously with careful inpatient monitoring and support.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1991

The use of angiotensin II as a potential method of targeting cytotoxic microspheres in patients with intrahepatic tumour.

Cytotoxic microspheres have been developed for intra-arterial use in patients with liver metastases. Following injection, the distribution of microspheres reflects the pattern of hepatic arterial blood-flow. Vasoactive agents, such as angiotensin II, by producing vasoconstriction in normal liver, might divert arterial blood toward tumour and thereby enhance the delivery of drug-loaded particles. Using a double isotope technique, the distribution of radiolabelled microspheres to tumour and normal liver tissue was measured before and after angiotensin II infusion in nine patients with multiple liver metastases. The median increase in tumour: normal ratio following angiotensin II infusion was by a factor of 2.8 (range 0.8-11.7, P less than 0.05). This novel approach to regional chemotherapy, using a combination of angiotensin II infusion and cytotoxic microspheres, increases the exposure of tumour to cytotoxic agents and may, therefore, enhance tumour response rates.

Adult↗
PubMed1991

The effect of cisplatin and carboplatin on c-myc promoter in erythroleukemic cells.

The recombinant plasmids p324, p330 and p323 carrying 5' flanking c-myc sequences linked to the reporter gene chloramphenicol acetyl-transferase (cat) were introduced into the mouse erythroleukemia cell line F412B2TK- and stable transfectants resistant to geneticin were obtained. The effects of two platinum coordination compounds, cisplatin and carboplatin, were studied using a wide range of drug concentrations. It was found that cisplatin stimulates cat gene expression with maximum effect at 5 x 10(-5) M concentration, while carboplatin at concentrations from 1 x 10(-6) to 1 x 10(-4) M did not have any effect. These results demonstrate that cisplatin stimulates transcription from the c-myc promoter in erythroleukemia cells and may support the use of carboplatin as compared to cisplatin in the treatment of cancer patients.

Animals↗
PubMed1990

Regional chemotherapy for colorectal liver metastases: a phase II evaluation of targeted hepatic arterial 5-fluorouracil for colorectal liver metastases.

The results of systemic chemotherapy in patients with liver metastases from colorectal cancer remain dismal. Regional chemotherapy has been advocated as a method of improving the delivery of cytotoxic drugs to tumour, while minimizing systemic toxicity. The use of vasoactive agents to redistribute arterial blood flow towards tumour, and of biodegradable microspheres to slow tumour blood flow, have also been suggested as methods of further improving tumour exposure to drug. We present 21 patients who received intrahepatic arterial chemotherapy for colorectal liver metastases. Combined treatment (angiotensin II, albumin microspheres and 5-fluorouracil) was administered 4-6 weekly, and bolus 5-fluorouracil was given in the intervening weeks. Toxicity was minimal. Responses were seen in seven patients. Fewer than half of the deaths were from liver metastases; a quarter of the patients died from non-cancer-related causes. Survival was prolonged in the treated group compared with historical controls. These results suggest that this regimen has activity in patients with colorectal liver metastases.

Adult↗
PubMed1990

Relationship between the pharmacokinetics and toxicity of mitozolomide.

The cytotoxic drug mitozolomide has been found to cause unpredictably severe thrombocytopenia during phase I and II clinical trials. In an attempt to relate dose and pharmacokinetic parameters to toxicity, we measured plasma concentrations of mitozolomide in 14 patients with a range of malignancies. There were significant correlations (Spearman rank correlation test) between drug clearance and AUC and white blood cell nadir. The pharmacokinetic and toxicity data were not normally distributed; therefore, it was not possible to construct predictive nomograms for toxicity based on linear regression analysis.

Adult↗