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Biomedical subjects

R M Mader

Publications and source records attributed to R M Mader.

At least 19 recordsLinked to original sources
PubMed2006

Fate of 5-fluorouracil, doxorubicin, epirubicin, and daunorubicin in hospital wastewater and their elimination by activated sludge and treatment in a membrane-bio-reactor system.

Antineoplastic agents are applied in cancer therapy and end up in hospital wastewater by human excretions. In this study, the raw wastewater of the sewer of the oncologic in-patient treatment ward of the Vienna University Hospital was monitored for 98 d over 2 years for the cytostatics 5-fluorouracil (5-FU), doxorubicin (DOX), epirubicin, and daunorubicin. In a next step, the elimination of the drugs by a membrane-bio-reactor system was investigated. In addition, their fate in wastewater and elimination by activated sludge was investigated with radio-labelled substances. During the monitoring periods, concentration levels ranging from <8.6 to 124 microgl(-1) for 5-FU and from <0.26 to 1.35 microgl(-1) for DOX were determined. The concentrations analysed fitted the lower ranges calculated by an input-output model. Treatment of oncologic wastewater in the membrane bio-reactor as well as the analysis of the effluents of the Vienna University Hospital resulted in concentrations below the limit of detection. Investigations with radio-labelled compounds showed that 5-FU is eliminated from the liquid phase below the limit of detection. But, up to 25% of radio-labelled equivalents of the drug's amount were found in the gaseous phase and only a marginal part in the solid phase, this indicates that at least one part of the drug is biodegraded. For the anthracyclines more than 90% was eliminated from the liquid phase. In this case, adsorption to suspended solids seems to be the major elimination pathway, as up to 30% of the radio-labelled equivalents of the drug's amount was detected in the solid phase. Our results indicate that the investigated anticancer drugs are eliminated by sewage treatment plants, either by biodegradation or adsorption.

Bioreactors↗
PubMed2006

Analysis of mechanisms contributing to AraC-mediated chemoresistance and re-establishment of drug sensitivity by the novel heterodinucleoside phosphate 5-FdUrd-araC.

Chemoresistance is a biological response of cells to survive toxic stress. During cancer treatment the development of chemoresistance is a major problem. The mechanisms how cells become insensitive, and which downstream pathways are affected are not completely understood. Since it has not been well analysed which and how many regulative disorders are subsummised under the term "chemoresistance", we examined and measured arabinosylcytosine (AraC)-mediated desensitation of two mechanisms relevant for tissue homeostasis, cell cycle inhibition and apoptosis induction. MCF-7 cells harbouring ectopic mutated p53 were suitable for this investigation because they activated these mechanisms subsequently and became insensitive to AraC with regard to cell cycle inhibition and apoptosis induction. The major causal mechanism of acquired resistance against AraC was most likely through the inhibition of the first step of AraC phosphorylation within the cell, which is rate limiting for its activation. With regard to cell cycle inhibition AraC-resistant cells were also resistant against 5-fluorodeoxyuridine (5-FdUrd), but fully responsive to 5-FdUrd-induced apoptosis, evidencing that cell cycle and apoptosis are independent of each other. Apoptosis correlated with AIF-activation and was independent of Caspase 7, whereas cell cycle inhibition correlated with cyclinD1 expression but not with induction of p21 or p27. The phosphate conjugated 5-FdUrd-araC heterodimer (5-Fluoro-2'-desoxyuridylyl-(3'-->5')-Arabinocytidine), which is a prodrug of AraC-monophosphate, reactivated AIF and down-regulated cyclin D1 in AraC-resistant cells and circumvented resistance to apoptosis and to cell cycle inhibition. Also, cells which were resistant to 5-FdUrd or doxorubicin were sensitive to 5-FdUrd-araC. This investigation demonstrates that chemoresistance affects apoptosis induction and cell cycle inhibition independently and that detailed knowledge about the affected downstream pathways would enable the design of targeted intervention with small molecules to restore chemosensitivity.

Antimetabolites, Antineoplastic↗
PubMed2004

Cytotoxic and apoptotic effects of novel heterodinucleoside phosphates consisting of 5-fluorodeoxyuridine and Ara-C in human cancer cell lines.

In search for possible alternatives in the treatment of human malignancies we investigated several new heterodinucleoside phosphates consisting of 5-Fluorodeoxyuridine (5-FdUrd) and Arabinofuranosylcytosine (Ara-C). We show that all dimers tested inhibited the number of colonies of CCL228, CCL227, 5-FU resistant CCL227 and HT-29 human colon tumor cells with IC50 values ranging from 0.65 to 1 nM. Dimer # 2 inhibited the number of sensitive and Ara-C resistant H9 human lymphoma cells with IC50 values ranging from 200 to 230 nM. Since no significant difference in the cytotoxicity of the dimers could be observed between sensitive and resistant cells, these compounds might be used in the treatment of 5-FU and Ara-C resistant tumors.

Antimetabolites, Antineoplastic↗
PubMed2003

Penetration of capecitabine and its metabolites into malignant and healthy tissues of patients with advanced breast cancer.

Capecitabine is an oral prodrug of 5-fluorouracil (FU). Since FU concentrations achieved in malignant lesions are an important determinant of efficacy, we investigated the intratumoral transcapillary transfer of capecitabine and its metabolites in vivo. A total of 10 patients with skin metastases from breast cancer received a daily dose of 2500 mg m(-2) capecitabine administered orally in two divided doses for 2 weeks. Microdialysis probes were inserted into a cutaneous metastasis and subcutaneous connective tissue to evaluate the interstitial tissue pharmacokinetics of capecitabine and its metabolites 5'-deoxy-5-fluorocytidine (DFCR), 5'-deoxy-5-fluorouridine (DFUR), and FU by capillary electrophoresis. As intended with the prodrug design of capecitabine, FU was present in low concentrations in tumour interstitium (median c(max): 0.26 microg ml(-1)) when compared with capecitabine, DFCR, and DFUR (median c(max): 2.66, 4.22, and 2.13 microg ml(-1), respectively). Capecitabine and its metabolites easily penetrated malignant and healthy tissue and equilibrated within 45 min between plasma and tissue interstitium. Considering tissue exposure at the extracellular level, no significant differences between healthy and malignant tissues were observed. Our data show that absorption and metabolism determined the tissue pharmacokinetics of capecitabine. There was no evidence of drug tolerance, which may be attributed to impaired transcapillary transfer into tissue, even after repeated administration as shown for three patients.

Adult↗
PubMed2002

On-line solid-phase extraction and determination of paclitaxel in human plasma.

The application of coupled-column liquid chromatographic analysis to pharmacokinetic studies eliminates the need for sample clean-up from plasma. Considering lipophilic antineoplastic agents, we tested this approach to analyze paclitaxel under unfavourable circumstances (i.e., weekly low-dose regimen, plasma protein binding >90%, UV detection at 229 nm). The excellent quality control data (recovery: 95.6-100.7%, inter-assay relative standard deviation on 5 days: 1.3-3.2%, accuracy: 0.9-2.7%) and the detection limit of 19 nM indicates the usefulness of this method for the analysis of paclitaxel in plasma using on-line solid-phase extraction.

Antineoplastic Agents, Phytogenic↗
PubMed2001

Penetration of dacarbazine and its active metabolite 5-aminoimidazole-4-carboxamide into cutaneous metastases of human malignant melanoma.

BACKGROUND: Dacarbazine has been on the market for approximately 3 decades but remains the most effective single agent available for the therapy of metastatic malignant melanoma (MMM). Most MMMs, however, respond poorly to dacarbazine therapy. Apart from tumor resistance at a molecular level, several studies support the notion that therapeutic failure in tumor therapy also might be attributed to an impaired transcapillary drug transfer. METHODS: On the basis of this hypothesis, the authors measured intratumor transcapillary transfer rates of dacarbazine and its active metabolite 5-aminoimidazole-4-carboxamide (AIC) by in vivo microdialysis after intravenous administration of dacarbazine at doses of 200 mg/m(2) to 1000 mg/m(2) (n = 7) in patients suffering from MMM. RESULTS: For all doses, area under the concentration curve (AUC) values for dacarbazine and AIC were not significantly different between plasma and tumor interstitium with AUC(tumor)/AUC(plasma) ratios of 0.97 +/- 0.08 (mean +/- standard error of the mean) for dacarbazine and 0.76 +/- 0.22 for AIC. AUC(0-240) values for dacarbazine and AIC measured in plasma correlated closely with corresponding AUC(0-240)values measured in the interstitium of MMMs with values of r(s) = 0.82 (P = 0.042) and r(s) = 0.90 (P = 0.037), respectively. CONCLUSIONS: The results of this study indicate favorable tumor penetration characteristics of dacarbazine and its active metabolite AIC. The relative lack of response to antineoplastic therapy with dacarbazine, thus might be explained by resistance of melanoma cells at a molecular level rather than by an inability of dacarbazine and AIC to penetrate into the interstitium of MMM.

Aged↗
PubMed2001

Reverse transcriptase template switching during reverse transcriptase-polymerase chain reaction: artificial generation of deletions in ribonucleotide reductase mRNA.

Using reverse transcriptase-polymerase chain reaction (RT-PCR), we have recently described a bona fide deletion within the coding sequence of the large subunit of ribonucleotide reductase (R1) mRNA in colon cancer. Consecutive studies have raised questions about the nature of this phenomenon, because the corresponding genomic alteration at the DNA level or an aberrant protein could not be detected. Thus we considered an in vitro artifact during RT-PCR as a possible explanation for this observation. In contrast to reverse transcriptase, Taq DNA polymerase or C. therm DNA polymerase did not generate the aberrant product, suggesting the demand for the template switching activity intrinsic to retroviral reverse transcriptases. In fact, virtually the same deletion was observed in RT-PCR experiments when in vitro transcribed R1 mRNA was used. Considering structural prerequisites for template switching within R1 mRNA, we show that two direct repeats adjacent to a strong stem-loop secondary structure flank the deleted region of 1851 base pairs. Because several mRNAs encoding proteins of clinical and diagnostic importance fulfill these criteria, template switching enhances the potential risk of observing artifacts when interpreting results from RT-PCR studies. As shown in the present example, this may involve the artificial generation and the misinterpretation of PCR fragments amplified from targets relevant to tumor biology or cancer pharmacology. As a possible solution, one-step PCR with C. therm polymerase should be considered. This polymerase eliminates the artificial generation of aberrant mRNA signals observed during cDNA synthesis.

Adenocarcinoma↗
PubMed2000

Long-term monitoring of sister chromatid exchanges and micronucleus frequencies in pharmacy personnel occupationally exposed to cytostatic drugs.

OBJECTIVES: Many antineoplastic drugs were found to have carcinogenic, mutagenic and teratogenic potential. The aim of this study was to carry out cytogenetic and internal dose monitoring of hospital pharmacy personnel regularly involved in the preparation of cytostatic agents, in order to test possible cytostatics-induced genotoxic effects due to occupational exposure under routine working conditions, and in cases of accidental contamination. METHODS: Platinum in whole blood and anthracyclines in plasma were measured to assess internal exposure to cytostatics. The level of cytogenetic damage was determined in peripheral blood lymphocytes with the micronucleus test and the sister chromatid exchange assay. Five series of monitoring were performed over a period of 2 years. RESULTS: No significant differences in the mean frequencies of sister chromatid exchanges (SCE) and micronuclei (MN) were found between occupationally exposed probands and controls (9.9 +/- 1.4 vs 10.1 +/- 1.2 SCEs/cell and 21.2 +/- 7.2 vs 23.3 +/- 7.5 MN/2000 binucleated (BN) cells, n = 16). Significant elevations of SCE or MN were detected in seven out of 12 cases of accidental contamination at the workplace, whereas no increase in platinum in blood and anthracyclines in plasma was observed in these probands. Two cases of non-reported contamination were identified by measurement of epirubicin in plasma. Smoking was found to increase the SCE significantly. No correlation between individual SCE scores and MN scores was observed. CONCLUSIONS: Our findings support a transient increase in SCE or MN after relevant exposure to cytostatic drugs in cases of accidental contamination. The lack of significant differences in SCE and MN between hospital pharmacy personnel and unexposed controls, points to high standards of safety at the corresponding workplaces.

Adult↗
PubMed2000

Relationship between in vivo drug exposure of the tumor interstitium and inhibition of tumor cell growth in vitro: a study in breast cancer patients.

A novel approach is described to simulate effect site pharmacodynamics of anticancer drugs. This approach is based on (i) the in vivo measurement of unbound, interstitial drug pharmacokinetics (PK) in solid tumor lesions in patients and (ii) a subsequent pharmacodynamic (PD) simulation of the time versus drug concentration profile in an in vitro setting. For this purpose, breast cancer cells (MCF-7) were exposed in vitro to the time versus interstitial tumor concentration profiles of 5-fluorouracil (5-FU) and methotrexate (MTX) from primary breast cancer lesions in patients. This led to a maximal reduction in the viable cell count of 69% on day 4, and of 71% on day 7 for 5-FU and MTX, respectively. This effect was dependent on the initial cell count and was characterized by a high interindividual variability. For 5-FU there was a significant correlation between the maximum antitumor effect and the intratumoral AUC (r = -0.82, p = 0.0005), whereas no correlation could be shown for MTX (r = 0.05, p = 0.88). We conclude, that the in-vivo-PK / in-vitro-PD model presented in this study may provide a rational approach for describing and predicting pharmacodynamics of cytotoxic drugs at the target site. Data derived from this approach support the concept that tumor penetration of 5-FU may be a response-limiting event, while the response to MTX may be determined by events beyond interstitial fluid kinetics.

Antimetabolites, Antineoplastic↗
PubMed2000

Genetic analysis of multiple synchronous lesions of the colon adenoma-carcinoma sequence.

The colorectal adenoma-carcinoma sequence represents a well-known paradigm for the sequential development of cancer driven by the accumulation of genomic defects. Although the colorectal adenoma-carcinoma sequence is well investigated, studies about tumours of different dignity co-existent in the same patient are seldom. In order to address the distribution of genetic alterations in different lesions of the same patient, we coincidently investigated carcinomas, adenomas and aberrant crypt foci in patients with sporadic colon cancer. By utilizing polymerase chain reaction, single-strand conformation polymorphism, heteroduplex-analysis, restriction fragment length polymorphism, protein truncation test and sequencing techniques we looked for mutations and microsatellite instability of APC, H-ras, K-ras, p53, DCC and the DNA repair genes hMLH1/hMSH2. In accordance with the suggested adenoma-carcinoma sequence of the colon, four patients reflected the progressive accumulation of genetic defects in synchronously appearing tumours during carcinogenesis. However, two patients with non-hereditary malignomas presented different genetic instabilities in different but synchronously appearing tumours suggesting non-clonal growth under almost identical conditions of the environment. Thus, sporadically manifesting multiple lesions of the colon were not necessarily driven by similar genetic mechanisms. Premalignant lesions may transform into malignant tumours starting from different types of genetic instability, which indicates independent and simultaneous tumorigenesis within the same organ.

Adenocarcinoma↗
PubMed2000

Benefit of interferon-alpha2b in a patient with unresectable hepatoma and chronic infection with hepatitis C virus.

Only in a small proportion of patients is advanced hepatocellular carcinoma (HCC) resectable, so the need for effective non-surgical treatments is obvious. We present details of a 72-year-old woman with inoperable HCC and chronic infection with hepatitis C virus, proved by the presence of antibodies directed against hepatitis C virus and positive polymerase chain reaction. The patient was treated with subcutaneous recombinant human interferon-alpha-2b. Within a few weeks, a partial tumour remission, paralleled by a decrease in serum levels of tumour markers and liver enzymes, was observed. In addition, polymerase chain reaction became negative. This observation facilitates the hypothesis that the anti-viral effects of interferon might have been jointly responsible for the anti-tumour activity observed. Interferon-alpha might serve as a treatment option in patients with unresectable hepatoma and chronic active viral hepatitis, but prospective studies are warranted.

Aged↗
PubMed1999

Activation of endothelium by immunotherapy with interleukin-2 in patients with malignant disorders.

Treatment with intravenous recombinant human interleukin-2 (rh IL-2) is frequently accompanied by the capillary leak syndrome and disturbances of the coagulation system. Although the exact mechanisms are still not fully understood, the involvement of the endothelium is proven. This investigation aimed to elucidate more precisely the role of the endothelium in the generation of IL-2-based side-effects. In nine tumour patients receiving intravenous rh IL-2, parameters characterizing endothelial cell activation as well as activation of the coagulation system were evaluated. A significant increase of the circulating endothelial leucocyte adhesion molecule-1 (cELAM-1) and the vasoconstrictor peptide endothelin-1 (ET-1) was observed (P<0.05), indicating activation of endothelial cells. The simultaneous increase of tissue-plasminogen activator and plasminogen activator inhibitor type-1 during therapy (P<0.05) corroborated this observation. A decrease in platelet count parallelled by an increase of fibrin degradation products, the prolongation of partial thromboplastin time, and the decrease of fibrinogen (P<0.05) suggested the development of disseminated intravascular coagulation (DIC), induced by activated endothelium and intensified by transient hepatic failure. We concluded that activation of the endothelium mediated by IL-2 was accompanied by a loss of endothelial integrity and capillary leak. The activated endothelium can trigger DIC via activation of the coagulation cascade. The increased ET-1 might act as an endogenous counter-regulator of the disadvantageous haemodynamic side-effects induced by IL-2.

Blood Coagulation↗
PubMed1999

Negative chronotropic effects of fentanyl attenuate beneficial effects of dobutamine on oxygen metabolism: hemodynamic and pharmacokinetic interactions.

Opioids are well known to cause cardiovascular depression. The aim of the present investigation was to determine whether an interaction of opioid derivatives with catecholamines might be involved in these hemodynamic alterations. Six comatose patients were enrolled into a prospective, nonrandomized pilot trial. All patients first received a continuous i.v. infusion of dobutamine (10 microgram. kg-1. min-1) paralleled by continuous administration of midazolam (0.4 mg. kg-1. h-1); thereafter, fentanyl was added i.v. (4 microgram. kg-1. h-1). Hemodynamic parameters as well as dobutamine and endogenous catecholamines plasma levels were determined. The mean arterial blood pressure did not change significantly during the whole study period. The continuous administration of dobutamine (steady-state plasma concentrations: 217 +/- 118 ng. ml-1) increased the beta1-adrenergic receptor-mediated hemodynamic parameters such as heart rate, stroke volume index, cardiac index, and oxygen delivery index (p <.05). The concomitant administration of fentanyl decreased the heart rate-dependent hemodynamic parameters (p <.05), suggesting that fentanyl antagonizes the chronotropic effects of dobutamine. In parallel, dobutamine plasma levels increased significantly (275 +/- 165 ng. ml-1; p <.05). Noteworthy, after administration of fentanyl, oxygen delivery and consumption index returned to baseline values. Radioligand binding experiments on rat cardiac ventricular microsomes ruled out a direct interaction of fentanyl with beta-adrenergic receptors and, more importantly, a fentanyl-induced inhibition of beta-adrenergic receptor G protein coupling. Our observations suggest that fentanyl inhibits the frequency-related hemodynamic changes induced by dobutamine. The underlying mechanism is independent of beta-adrenergic receptors, but is powerful enough to abolish the salutary effect of dobutamine on oxygen delivery and consumption.

Aged↗
PubMed1998

Interstitial methotrexate kinetics in primary breast cancer lesions.

The transfer of cytotoxic agents across the tumor endothelium into the interstitial tumor space is considered a critical step in clinical resistance of solid tumors to antineoplastic chemotherapy. However, experimental data on drug transfer from the blood into the interstitium of solid tumors are scarce. Therefore, in this study, we used an innovative technique, in vivo microdialysis, for measuring interstitial tumor pharmacokinetics and plasma-to-tumor transfer rates of methotrexate (MTX) in breast cancer patients. Microdialysis probes were inserted into the primary tumor and the periumbilical s.c. adipose layer of nine previously chemotherapy-naive breast cancer patients to monitor interstitial concentrations following i.v. administration of MTX (40 mg/m2) during a three-drug treatment regimen. Mean interstitial MTX load in breast tumors, expressed as area under curve (AUC), was 60 +/- 20% (mean +/- SE; coefficient of variation = 100%) of mean plasma MTX load. There was no correlation between plasma AUC and the AUC in the interstitial space of tumor tissue (P = 0.93). Not one of the parameters plasma, interstitial tumor load, and transfer rate of MTX to the interstitial space was associated with favorable clinical response. In conclusion, plasma levels of MTX are not predictive of intratumor levels. There is a high interindividual variability in transendothelial MTX transfer. Under the present conditions, access of MTX to the interstitial space is not a rate-limiting step for clinical response to chemotherapy.

Antimetabolites, Antineoplastic↗
PubMed1998

Analysis of microdialysates from cancer patients by capillary electrophoresis.

Microdialysis (MD) is an innovative clinical technique for measuring interstitial tissue pharmacokinetics and plasma-to-tissue transfer rates of drugs in humans. However, microdialysis requires the availability of specialized analytical techniques. Capillary electrophoresis (CE), which enables concentration measurements of small volume samples, theoretically constitutes an ideal analytical technique for measuring drug concentrations in microdialysates. In the present experiments, we aimed at assessing the potential utility and limitations of CE for analysis of microdialysates in a clinical situation. Microdialysates were obtained from primary breast cancer patients who received chemotherapy including 5-fluorouracil (5-FU; 600 mg/m2). Subsequently, 5-FU concentrations were measured in tumor - and subcutaneous adipose tissue - microdialysates by CE. By combining MD and CE, complete time versus concentrations profiles could be obtained for 5-FU in the interstitial tumor space and important clinical questions could be addressed. We conclude that the combination of MD and CE leads to important and previously inaccessible information about the drug distribution process in a clinical setting.

Antimetabolites, Antineoplastic↗