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Biomedical subjects

D C Talbot

Publications and source records attributed to D C Talbot.

At least 55 records · Page 3Linked to original sources
PubMed1997

Overexpression of human NADPH:cytochrome c (P450) reductase confers enhanced sensitivity to both tirapazamine (SR 4233) and RSU 1069.

P450 reductase (NADPH: cytochrome c (P450) reductase, EC 1.6.2.4) plays an important role in the reductive activation of the bioreductive drug tirapazamine (SR4233). Thus, in a panel of human breast cancer cell lines, expression of P450 reductase correlated with both the hypoxic toxicity and the metabolism of tirapazamine [Patterson et al (1995) Br J Cancer 72: 1144-1150]. To examine this dependence in more detail, the MDA231 cell line, which has the lowest activity of P450 reductase in our breast cell line panel, was transfected with the human P450 reductase cDNA. Isolated clones expressed a 78-kDa protein, which was detected with anti-P450 reductase antibody, and were shown to have up to a 53-fold increase in activity of the enzyme. Using six stable transfected clones covering the 53-fold range of activity of P450 reductase, it was shown that the enzyme activity correlated directly with both hypoxic and aerobic toxicity of tirapazamine, and metabolism of the drug under hypoxic conditions. No metabolism was detected under aerobic conditions. For RSU1069, toxicity was also correlated with P450 reductase activity, but only under hypoxic conditions. Measurable activity of P450 reductase was found in a selection of 14 primary human breast tumours. Activity covered an 18-fold range, which was generally higher than that seen in cell lines but within the range of activity measured in the transfected clones. These results suggest that if breast tumours have significant areas of low oxygen tension, then they are likely to be highly sensitive to the cytotoxic action of tirapazamine and RSU 1069.

Antineoplastic Agents↗
PubMed1997

Platelet-derived endothelial cell growth factor expression correlates with tumour angiogenesis and prognosis in non-small-cell lung cancer.

Angiogenesis is a recently described prognostic factor in non-small-cell lung cancer. Platelet-derived endothelial cell growth factor (PD-ECGF), shown to be the enzyme thymidine phosphorylase (TP), induces angiogenesis in vitro and in vivo. High intracellular levels of the enzyme are associated with increased chemosensitivity to pyrimidine antimetabolites. PD-ECGF/TP expression was evaluated immunohistochemically in surgically resected specimens from 107 patients with operable non-small-cell lung cancer using the P-GF,44C monoclonal antibody. High expression of PD-ECGF/TP was found in 25% of cases and was associated with high vascular grade (P = 0.01). Fourteen of 32 (44%) high vascular grade tumours showed a positive reactivity for PD-ECGF/TP vs 13/75 (17%) of low/medium vascular grade. Positive expression was observed more frequently in T2-staged cases than in T1 (P = 0.04). While overall survival was not affected (P = 0.09), subset analysis revealed that node-negative patients with positive PD-ECGF/TP expression had a worse prognosis (P = 0.04). The results suggest that PD-ECGF/TP may be an important molecule involved in angiogenesis in non-small-cell lung cancer. Up-regulation of the enzyme defines a more aggressive tumour phenotype in patients with node-negative disease. Assessment of vascular grade and PD-ECGF/TP expression should be taken into account in the design of randomized trials assessing the role of adjuvant chemotherapy in non-small-cell lung cancer.

Adenocarcinoma↗
PubMed1997

A novel cyclic adenosine monophosphate analog induces hypercalcemia via production of 1,25-dihydroxyvitamin D in patients with solid tumors.

The treatment of cancer patients with conventional chemotherapy is sometimes associated with severe systemic toxicity and only a minimal survival benefit. Because of this, new less toxic and more efficacious treatments have been sought. 8-Chloro-cAMP (8-Cl-cAMP) is one of a new generation of anticancer drugs that act at the level of signal transduction. In preclinical models, 8-Cl-cAMP modulates protein kinase A (PKA) leading to growth inhibition and increased differentiation of cancer cells. 8-Cl-cAMP was given to 16 patients with advanced cancer as an infusion via an indwelling subclavian venous catheter. We showed that 8-Cl-cAMP had a parathyroid hormone-like effect leading to increased synthesis of renal 1,25-dihydroxyvitamin D [up to 14 times the baseline value, median 3.6 times; P = 0.00001 (Student's paired t test)]. This produced the dose-limiting toxicity of reversible hypercalcemia that could not be controlled by the administration of either pamidronate or dexamethasone. The treatment was otherwise well tolerated, and other cAMP-dependent pathways (cortisol and TSH) were not affected, emphasizing the marked differences between organs in their sensitivity to this cAMP analog. Our results have shown that 8-Cl-cAMP is biologically active, and it is feasible that if the hypercalcemia can be controlled, then this drug may have a role as a single agent, or as a short infusion between cycles of chemotherapy.

8-Bromo Cyclic Adenosine Monophosphate↗
PubMed1996

Prognostic value of angiogenesis in operable non-small cell lung cancer.

Tumour angiogenesis is an important factor for tumour growth and metastasis. Although some recent reports suggest that microvessel counts in non-small cell lung cancer are related to a poor disease outcome, the results were not conclusive and were not compared with other molecular prognostic markers. In the present study, the vascular grade was assessed in 107 (T1,2-N0,1) operable non-small cell lung carcinomas, using the JC70 monoclonal antibody to CD31. Three vascular grades were defined with appraisal by eye and by Chalkley counting: high (Chalkley score 7-12), medium (5-6), and low (2-4). There was a significant correlation between eye appraisal and Chalkley counting (P < 0.0001). Vascular grade was not related to histology, grade, proliferation index (Ki67), or EGFR or p53 expression. Tumours from younger patients had a higher grade of angiogenesis (P = 0.05). Apart from the vascular grade, none of the other factors examined was statistically related to lymph node metastasis (P < 0.0001). A univariate analysis of survival showed that vascular grade was the most significant prognostic factor (P = 0.0004), followed by N-stage (P = 0.001). In a multivariate analysis, N-stage and vascular grade were not found to be independent prognostic factors, since they were strongly related to each other. Excluding N-stage, vascular grade was the only independent prognostic factor (P = 0.007). Kaplan-Meier survival curves showed a statistically significant worse prognosis for patients with high vascular grade, but no difference was observed between low and medium vascular grade. These data suggest that angiogenesis in operable non-small cell lung cancer is a major prognostic factor for survival and, among the parameters tested, is the only factor related to cancer cell migration to lymph nodes. The integration of vascular grading in clinical trials on adjuvant chemotherapy and/or radiotherapy could substantially contribute in defining groups of operable patients who might benefit from cytotoxic treatment.

Aged↗
PubMed1996

Modulation of bryostatin 1 muscle toxicity by nifedipine: effects on muscle metabolism and oxygen supply.

Bryostatin 1, an anti-neoplastic agent and protein kinase C activator, has dose-limiting toxicity manifesting as myalgia. Studies in vivo have suggested that this myalgia may be caused by impairment of oxidative metabolism as mitochondrial capacity, muscle reoxygenation and proton washout from muscle are reduced by bryostatin, possibly as a result of vasoconstriction. To investigate these mechanisms further, and to enable use of bryostatin for prolonged periods, the effect of a vasodilator on the established effects of bryostatin on calf metabolism was studied using 31P magnetic resonance spectroscopy and near infrared spectroscopy. Six patients with disseminated melanoma were examined on four occasions: before and 1 week after initiation of long-term nifedipine (10 mg twice daily) treatment and then 4 and 48 h after bryostatin infusion (25 micrograms m(-2)). Nifedipine impaired muscle oxidative metabolism but had no effect on proton efflux or muscle reoxygenation rate. In the presence of nifedipine, two of the effects of bryostatin, impaired reoxygenation rate and reduced proton efflux, were abolished, but the impaired mitochondrial activity remained. These results show that nifedipine counteracted the vasoconstrictive effect of bryostatin 1. However, because nifedipine itself had an unexpected effect on mitochondrial metabolism, it was not possible to assess whether nifedipine modified bryostatin's effect on this variable. There was no additive detrimental effect of bryostatin on mitochondrial metabolism and nifedipine did not reduce the clinical toxicity of bryostatin 1, which cannot therefore be due to vasoconstriction.

Adult↗
PubMed1996

A rapid immunoassay method for the direct detection of PCR products: application to detection of TEM beta-lactamase genes.

A rapid immunoassay for the detection of specific PCR products is described in which a positive PCR amplification result is detected, usually in less than 5 min, by applying a few drops of the diluted PCR end-product to a small immunoassay sample device. The method was evaluated in comparison with conventional susceptibility tests and isoelectric focusing (IEF) for the detection of TEM-family beta-lactamase genes in 477 Escherichia coli isolates from urine samples. Of 187 isolates identified as presumptive TEM beta-lactamase producers by conventional methods, 185 generated a positive signal in the PCR immunoassay system. Two further signal-positive isolates were recognised when the PCR was repeated. In addition, one of the 276 ampicillin-susceptible isolates gave a positive signal in repeated PCR-immunoassay experiments despite being ampicillin susceptible and failing to give a TEM-type enzyme band in iso-electric focusing experiments.

Bacteriuria↗
PubMed1995

A pilot study of mitomycin, cisplatin and continuous infusion 5-fluorouracil (MCF) in advanced non-small-cell lung cancer.

A pilot study of continuous infusional 5-fluorouracil 200 mg m-2 per 24 h by ambulatory pump and Hickman line for the entire treatment cycle with mitomycin C 8 mg m-2 i.v. on day 1 and cisplatin 75 mg m-2 i.v. on day 1, both repeated every 28 days, was carried out in 31 previously untreated patients with advanced non-small-cell lung cancer (NSCLC). Of 31 patients assessable for response, one attained a complete remission and eight a partial remission, an overall response rate of 29%. Haematological toxicity was minimal, with only 3% of patients developing WHO grade III/IV neutropenia and 13% grade III/IV thrombocytopenia. Significant side-effects included moderate to severe emesis (41%), mucositis (34%), diarrhoea (31%) and palmar-plantar syndrome (14%). Seven patients (23%) had Hickman line complications requiring line removal. Continuous infusional chemotherapy with this regimen is active in advanced non-small-cell lung cancer, but its complexity and associated treatment toxicity offer little advantage over equally active but simpler and less toxic cisplatin-based regimens.

Adenocarcinoma↗
PubMed1995

Increased sensitivity to the prodrug 5'-deoxy-5-fluorouridine and modulation of 5-fluoro-2'-deoxyuridine sensitivity in MCF-7 cells transfected with thymidine phosphorylase.

Platelet-derived endothelial cell growth factor (PD-ECGF) is identical to human thymidine phosphorylase (dThdPase). The human MCF-7 breast cancer cell line was transfected with the dThdPase cDNA and expressed a 45 kDa protein that was detected with anti-dThdPase antibody. Cell lysates possessed elevated dThdPase activity and cells had up to 165-fold increased sensitivity to the prodrug 5'-deoxy-5-fluorouridine (5'-DFUR) in vitro. Sensitivity to 5-fluorouracil (5-FU) and 5-fluoro-2'-deoxyuridine (5-FUdR) was unchanged. Recombinant dThdPase was shown to catalyse directly the phosphorolytic cleavage of 5'-DFUR to 5-FU. Exogenous thymidine (dThd) reversed the toxicity of 5-FUdR on the parental line (1 microM dThd increased the IC50 value 1000-fold), but the dThd rescue was substantially modulated in the dThdPase-expressing clone 4 (1 microM dThd raised the IC50 value 3-fold). We observed a substantial 'bystander' killing effect when small proportions of dThdPase-expressing cells were mixed with parental MCF-7 cells. dThdPase activity was on average 27-fold higher in breast tumours than in normal breast. The levels of wild-type MCF-7 are similar to the low end of the tumour expression. Thus, in some tumours resistance to 5'-DFUR therapy could be due to low dThdPase activity, and transfection to raise the dThdPase levels within the broad tumour range or above it should markedly enhance sensitivity to the prodrug. These results confirm that dThdPase is a major pathway in the metabolic activation of 5'-DFUR, and the bystander effect suggests that this may be a suitable enzyme for gene therapy-directed enzyme/prodrug activation therapy.

Antineoplastic Agents↗
PubMed1995

Symptom relief with MVP (mitomycin C, vinblastine and cisplatin) chemotherapy in advanced non-small-cell lung cancer.

The role of chemotherapy in the palliation of patients with advanced stage (IIIB and IV non-small-cell lung cancer (NSCLC) remains controversial. We have carried out a chemotherapy study emphasising symptom relief, a topic not normally discussed in previous similar studies. A total of 120 patients with locally advanced or metastatic non-small-cell lung cancer (NSCLC) were treated with a moderate-dose palliative chemotherapy regimen consisting of mitomycin C 8 mg m-2 i.v. on day 1 (alternate courses), vinblastine 6 mg m-2 i.v. on day 1 and cisplatin 50 mg m-2 i.v. on day 1 (MVP), repeating every 21 days for a maximum of six courses. Thirty-eight of 118 assessable patients (32%) achieved an objective response. Patients with locally advanced disease (stage IIIB) had a significantly better response rate (52%) than those with metastatic disease (25%) (P < 0.01). In 76 out of 110 (69%) patients, with tumour-related symptoms including 24 out of 31 patients (78%) with locally advanced disease, symptoms completely disappeared or substantially improved. In only 15 patients (14%) did symptoms progress during treatment. Symptomatic improvement was achieved after one course of chemotherapy in 61% and after two courses in 96% of responding patients. The schedule was well tolerated. Only 19% developed WHO grade 3/4 nausea/vomiting, and only 3% developed significant alopecia. Other toxicities were minimal. MVP is a pragmatic inexpensive chemotherapy regimen that offers useful symptom palliation in patients with advanced NSCLC and merits a 1-2 course therapeutic trial in such patients. The schedule should also be assessed as primary (neoadjuvant) chemotherapy before radical radiotherapy for locally advanced NSCLC in a randomised trial.

Adult↗
PubMed1995

Combination chemotherapy with gemcitabine and cisplatin in the treatment of advanced non-small cell lung cancer: preliminary results of an ongoing phase I/II study.

Collaborative phase I and II studies of the combination of gemcitabine and cisplatin in patients with advanced non-small cell lung cancer are ongoing at five centres in the UK and France. In the initial completed phase I study, 16 patients (15 evaluable) have been entered using a fixed dose of gemcitabine 1000 mg/m2 given as a 30 min intravenous infusion weekly for 3 weeks. On the third week the gemcitabine was immediately followed by cisplatin with pre- and post-hydration. This regimen required only 1 night of hospitalization every 4 weeks. The study design was for sequential groups of patients to receive 3 dose levels of cisplatin (60 mg/m2, 75 mg/m2 and 100 mg/m2) but these doses would be modified and the number of patients at any dose level could be increased if significant toxicity was observed. Three patients were to be entered at the first two dose levels and 10 patients were to confirm the maximum tolerated dose (if reached) or expand the database on toxicity at the final predetermined dose level. The major haematological toxicities were neutropenia (grade 4 in 3 patients) and thrombocytopenia (grade 3 or 4 in 5 patients) but both were of short duration and uncomplicated. Grade 3 nausea and vomiting occurred in 12 patients but was no worse than would be expected from cisplatin alone. Alopecia was not a problem (no hair loss in 10 patients and grade 1 or 2 in 6 patients) and no significant renal or neurotoxicity was seen. A phase II study using cisplatin 100 mg/m2 in combination with gemcitabine 1000 mg/m2 has been opened and to date 19 patients are evaluable for response. Eight (42%) have achieved partial remissions. The study is ongoing and will recruit 50 evaluable patients.

Antimetabolites, Antineoplastic↗
PubMed1994

Signet-ring cell lymphoma of bone marrow.

A case of signet-ring cell lymphoma affecting bone marrow is reported. The tumour presented as multiple lytic lesions in the lumbosacral spine. A bone biopsy specimen showed the typical appearances of signet-ring cell lymphoma, and the cells stained positively with antiserum to CD20, though neither immunoglobulin light or heavy chains could be shown within the vacuoles. The patient subsequently responded to chemotherapy.

Bone Marrow↗
PubMed1993

Phase I study of bryostatin 1: assessment of interleukin 6 and tumor necrosis factor alpha induction in vivo. The Cancer Research Campaign Phase I Committee.

BACKGROUND: Many oncogenes have been shown to code for growth factor receptors that are involved in regulation of cell growth and proliferation and can activate transcription via protein kinase C. Bryostatin 1, a partial agonist of protein kinase C, has demonstrated potent antitumor activity in vitro and in vivo in human tumor xenografts. PURPOSE: The aim of this phase I study was to determine the optimal dosage and toxicity profile of bryostatin 1 and its influence on cytokine release in vivo. METHODS: Three successive cohorts consisting of 35 patients with various malignant tumors were treated with bryostatin 1 by intravenous infusion over 1 hour as follows: cohort A--35 micrograms/m2 (three patients) or 50 micrograms/m2 (eight patients) once every 2 weeks; cohort B--25 micrograms/m2 once a week (eight patients); and cohort C--25 micrograms/m2 once a week for 3 weeks, with no treatment during the 4th week (16 patients). Plasma levels of tumor necrosis factor alpha (TNF-alpha) and interleukin 6 (IL-6) were measured by immunoradiometric assay and by radioimmunoassay, respectively. RESULTS: The dose-limiting toxicity was grade 3 or 4 myalgia in four of 11 patients in cohort A, in two of eight in cohort B, and in none of 16 in cohort C. Occurrence of myalgia was dose related. There was no significant myelosuppression, apart from a small and transient fall in platelet count. Six patients experienced acute but transient skin flushing, dyspnea, hypotension, and bradycardia, probably related to the bryostatin 1 vehicle. TNF-alpha and IL-6 were detected in plasma at 2 and 24 hours after treatment, respectively, and the levels were dose related (P = .02). Two patients with metastatic malignant melanoma had partial remission after three or four cycles of therapy; remission lasted 6 weeks and 10+ months, respectively. CONCLUSIONS: The dose-limiting toxicity of bryostatin 1 was myalgia. Plasma IL-6 and TNF-alpha concentrations were increased within 24 hours of therapy. Antitumor activity against malignant melanoma was observed early in the course of treatment. IMPLICATIONS: The recommended dosage of bryostatin 1 for phase II studies is 25 micrograms/m2 by intravenous infusion for 1 hour once a week for 3 weeks, with no treatment in the 4th week. IL-6 and TNF-alpha plasma concentrations may be useful in monitoring biological activity of bryostatin 1. Future studies should explore use of this drug with other conventional immune modulators and conventional cytotoxic drugs.

Adult↗
PubMed1993

Phase II trial of the novel sulphonylurea sulofenur in advanced breast cancer.

A total of 18 women with advanced breast cancer were treated with sulofenur [LY186641; N-(5-indanylsulfonyl)-N'-(4-chlorophenyl)-urea], a diarylsulfonylurea that has broad-spectrum activity against a number of murine mammary tumour xenografts. The dosage chosen on the basis of pre-clinical and phase I studies was 700 mg/m2 given orally once daily for 14 days, with treatments being repeated every 3 weeks. There was no response. All patients experienced at least grade 1 anaemia, and two patients developed symptomatic methaemoglobinaemia. Two patients developed grade 4 rises in serum liver-function values along with histological changes consistent with drug-induced toxicity. The mean plasma concentrations of 176 micrograms/ml were lower than the levels required to exert anti-tumour effect in the mouse model.

Administration, Oral↗
PubMed1993

Carboplatin in the treatment of advanced breast cancer: a phase II study using a pharmacokinetically guided dose schedule.

PURPOSE: We performed a phase II study of single-agent carboplatin against metastatic/locally advanced breast cancer using a pharmacokinetically guided dose schedule, to define further the potential role for this agent in combination and high-dose therapy. PATIENTS AND METHODS: Forty patients with metastatic/locally advanced breast cancer were treated with carboplatin based on glomerular filtration rate (GFR) to achieve an area under the concentration-versus-time curve (AUC) of 7 mg/mL.min, with each course repeated at 4-week intervals. The median age was 57 years (range, 37 to 71). RESULTS: Ten patients achieved a partial response (PR), for an overall response rate of 25% (95% confidence interval, 13% to 41%). One of 13 (8%) previously treated patients responded compared with nine of 27 (33%) patients who had not received previous chemotherapy. Median response duration was 18 weeks (range, 10 to 68). World Health Organization (WHO) grade 2 or greater toxicity was as follows: anemia, 42%; leukopenia, 20%; thrombocytopenia, 35%; nausea/vomiting, 39%; and infection, 9%. CONCLUSION: This study confirms other reports indicating that carboplatin has moderate activity in previously untreated patients, but not in previously treated patients. In our view, carboplatin is a more appropriate agent than cisplatin for inclusion in high-dose chemotherapy schedules with autologous bone marrow rescue, and our results support the concept of calculating dose escalation on the basis of the area under the dose-response curve using the Calvert formula, rather than on surface area.

Adult↗