I Schiffer

Johannes Gutenberg-Universität Mainz, Mayence, Rheinland-Pfalz, Germany

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Publications (26)96.21 Total impact

  • K Rommens · M Schmidt · I Schiffer · J Hengstler · H Kölbl

    No preview · Article · Sep 2008 · Geburtshilfe und Frauenheilkunde
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    ABSTRACT: Trastuzumab (Herceptin) has improved therapy of breast cancer. Only patients overexpressing ERBB2 are treated with trastuzumab, whereas its use in tumours without ERBB2 expression is useless. This led to the concept that the subgroup of trastuzumab-sensitive tumours is 'ERBB2-dependent', meaning that ERBB2 signalling is indispensable for growth of these tumours. We used a mouse model that allows anhydrotetracycline (ATc)-controlled downregulation of ERBB2 in tumour tissue. ERBB2 mRNA and protein expression were downregulated below detection limit leading to a macroscopically complete tumour remission within 14 days. Tumour remission was accompanied by a strong decrease in proliferation, a moderate increase in apoptosis, as well as dephosphorylation of ERK1/2 and AKT/PKB. These data clearly indicate ERBB2 dependence. Therefore, a high sensitivity to trastuzumab may be suspected. Surprisingly, trastuzumab caused a much weaker effect compared to ATc-induced ERBB2 downregulation, although a decrease in ERBB2 membrane localisation was induced. Only a slight decrease in proliferation and a weak transient increase in apoptosis were observed. Interestingly, tumours responded to trastuzumab by a sharp fivefold increase in phosphorylated AKT/PKB as well as a 3.5- and 5.3-fold increase in AKT1 and AKT2 mRNA levels, respectively. In conclusion, 'ERBB2 dependence' is not sufficient to define trastuzumab-responsive tumours. The suboptimal effect of trastuzumab compared to the maximally possible effect induced by ATc demonstrates a high potential for improved ERBB2 blocking therapies.
    Full-text · Article · Jun 2008 · British Journal of Cancer
  • K Rommens · M Schmidt · I Schiffer · J Hengstler · H Koebl

    No preview · Article · Jan 2008 · Geburtshilfe und Frauenheilkunde
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    ABSTRACT: Paclitaxel plays an important role in the treatment of primary breast cancer. However, a substantial proportion of patients treated with paclitaxel does not appear to derive any benefit from this therapy. We performed a prospective study using tumour cells isolated from 50 primary breast carcinomas. Sensitivity of primary tumour cells to paclitaxel was determined in a clinically relevant range of concentrations (0.85-27.2 microg ml(-1) paclitaxel) using an ATP assay. Chemosensitivity data were used to study a possible association with immunohistochemically determined oestrogen and progesterone receptor (ER and PR) status, as well as histopathological parameters. Progesterone receptor (PR) mRNA expression was also determined by quantitative RT-PCR. We observed a clear association of the PR status with chemosensitivity to paclitaxel. Higher levels of immunohistochemically detected PR expression correlated with decreased chemosensitivity (P=0.008). Similarly, high levels of PR mRNA expression were associated with decreased paclitaxel chemosensitivity (P=0.007). Cells from carcinomas with T-stages 3 and 4 were less sensitive compared to stages 1 and 2 (P=0.013). Multiple regression analysis identified PR receptor status and T-stage as independent predictors of paclitaxel chemosensitivity, whereas the ER, N-stage, grading and age were not influential. In conclusion, in vitro sensitivity to paclitaxel was higher for PR-negative compared with PR-positive breast carcinoma cells. Thus, PR status should be considered as a possible factor of influence when designing new trials and chemotherapy protocols.
    Full-text · Article · Feb 2007 · British Journal of Cancer
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    ABSTRACT: Identification of oncogene dependent signaling pathways controlling aggressive tumor growth has led to the emergence of a new era of oncogene-blocking therapies, including Herceptin and Gleevec. In the recent years conditional mouse tumor models have been established that allow switching-off the expression of specific oncogenes controlling tumor growth. The results may have two important implications for oncogene-blocking therapies: (i) downregulation of oncogenes, for instance HER2, MYC, RAS, RAF, BCR-ABL or WNT1, usually leads to a rapid tumor remission. However, it was observed that the initial remission was followed by recurrent tumor growth in most studies. Interestingly, different oncogenes controlled tumor growth in the recurrent than in the primary tumors. This could explain the astonishing clinical observation that inhibitors of a broader spectrum of protein kinases (so-called: "dirty inhibitors") may be superior over highly specific substances. Due to their additional "unspecific" inhibition of a broader spectrum of kinases, they may hamper the escape mechanisms by antagonizing also the pathways controlling recurrent tumor growth. (ii) Experiments with cell systems that allow switching-on oncogene expression point to a so far possibly underestimated cancer drug target: the dormant tumor cell. Oncogene expression (for instance: NeuT or RAS) led to a phenomenon named oncogene-induced senescence or dormancy. Dormant cells are unresponsive to mitogenic stimuli. Importantly, such cells are not at all ready to die, but can remain viable for extended periods of time. Recently, dormant tumor cells have been shown to be more resistant to stresses such as hypoxia or exposure to cytostatic drugs. It still is a matter of debate if and under which conditions dormant tumor cells can be "kissed to life". If these cells contribute to carcinogenesis, it will be important to identify substances specifically killing senescent cells. This review will focus on the possible relevance of senescence both as a pre-oncogenic condition and also for therapy.
    No preview · Article · Dec 2006 · Current cancer drug targets
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    ABSTRACT: HER3 (erbB-3) is a member of the epidermal growth factor receptor (EGFR) family. After dimerization with other members of the EGFR family several signal transduction cascades can be activated, including phosphoinosite 3'-kinase (PI3-K)/Akt and extracellular signal-regulated kinase (ERK1/2). Here, we studied a possible association between HER3 expression and prognosis in patients with ovarian cancer. Tumor tissue of 116 consecutive patients diagnosed with primary epithelial ovarian cancer between 1986 and 1995 was analyzed immunohistochemically for HER3 expression. A possible influence of HER3 expression on survival was studied by multivariate Cox regression adjusting for established clinical prognostic factors. A positive HER3 expression was observed in 53.4% of the patients. HER3 expression was associated with decreased survival in proportional hazard modeling, including the International Federation of Gynecology and Obstetrics (FIGO) stage, histologic grade and type, residual disease, and age. After likelihood ratio forward as well as backward selection, only HER3 expression (hazard ratio, 1.71; 95% CI, 1.10 to 2.67; P = .018), FIGO stage (hazard ratio, 4.78; 95% CI, 1.89 to 12.08; P = .001), residual tumor (hazard ratio, 2.69; 95% CI, 1.40 to 5.17; P = .003), and age (hazard ratio, 2.06; 95% CI, 1.17 to 3.65; P = .013) were found to be significant. Kaplan-Meier plots demonstrated a clear influence of HER3 expression on survival time. Median survival time was 3.31 years (95% CI, 1.93 to 4.68) for patients with low HER3 expression, compared with only 1.80 years (95% CI, 0.83 to 2.78) for patients with HER3 overexpression (log-rank test P = .0034). HER3 may represent a new prognostic factor in primary epithelial ovarian cancer. Pending validation, exploration of therapeutic strategies to block HER3 could be warranted.
    Full-text · Article · Oct 2006 · Journal of Clinical Oncology
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    ABSTRACT: Oncogenic activation of the receptor tyrosine kinase ERBB2 is a key event in the development of a number of epithelial malignancies. In these tumors, high levels of ERBB2 are strongly associated with metastatic disease and poor prognosis. Paradoxically, an inherent cellular response to hypermitogenic signaling by ERBB2 and other oncogenes seems to be growth arrest, rather than proliferation. Molecular characterization of this yet undefined antiproliferative state in independent cell lines overexpressing either wild-type ERBB2 or the mutationally activated receptor unveiled a dramatic induction of the alpha5beta1 integrin fibronectin receptor. alpha5 Integrin up-regulation is mainly a transcriptional response mediated by the hypoxia-inducible transcription factors (HIF), leading to a massive increase in membrane-resident receptor molecules and enhanced fibronectin adhesiveness of the respective cells. Functionally, ERBB2-dependent ligation of fibronectin results in improved survival of mammary adenocarcinoma cells under adverse conditions, like serum withdrawal, hypoxia, and chemotherapy. HIF-1alpha is an independent predictor of poor overall survival in patients with breast cancer. In particular, HIF-1alpha overexpression correlates significantly with early local relapse and distant metastasis, a phenotype also highly characteristic of ERBB2-positive tumors. As HIF-1alpha is known to be stabilized by ERBB2 signaling under normoxic conditions, we propose that alpha5 integrin is a major effector in this regulatory circuit and may represent the molecular basis for the HIF-1alpha-dependent aggressiveness observed in ERBB2-overexpressing breast carcinomas. Hypermitogenic ERBB2 signaling and tumor hypoxia may act synergistically to favor the establishment of chemoresistant dormant micrometastatic cells frequently observed in patients with breast cancer. This new insight could be the basis for additional approaches complementing current cancer therapy.
    Preview · Article · May 2006 · Cancer Research
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    ABSTRACT: Several studies have shown that HER-2/neu (erbB-2) blocking therapy strategies can cause tumor remission. However, the responsible molecular mechanisms are not yet known. Both ERK1/2 and Akt/PKB are critical for HER-2-mediated signal transduction. Therefore, we used a mouse tumor model that allows downregulation of HER-2 in tumor tissue by administration of anhydrotetracycline (ATc). Switching-off HER-2 caused a rapid tumor remission by more than 95% within 7 d of ATc administration compared to the volume before switching-off HER-2. Interestingly, HER-2 downregulation caused a dephosphorylation of p-ERK1/2 by more than 80% already before tumor remission occurred. Levels of total ERK protein were not influenced. In contrast, dephosphorylation of p-Akt occurred later, when the tumor was already in remission. These data suggest that in our HER-2 tumor model dephosphorylation of p-ERK1/2 may be more critical for tumor remission than dephosphorylation of p-Akt. To test this hypothesis we used a second mouse tumor model that allows ATc controlled expression of BXB-Raf1 because the latter constitutively signals to ERK1/2, but cannot activate Akt/PKB. As expected, downregulation of BXB-Raf1 in tumor tissue caused a strong dephosphorylation of p-ERK1/2, but did not decrease levels of p-Akt. Interestingly, tumor remission after switching-off BXB-Raf1 was similarly efficient as the effect of HER-2 downregulation, despite the lack of p-Akt dephosphorylation. In conclusion, two lines of evidence strongly suggest that dephosphorylation of p-ERK1/2 and not that of p-Akt is critical for the rapid tumor remission after downregulation of HER-2 or BXB-Raf1 in our tumor model: (i) dephosphorylation of p-ERK1/2 but not that of p-Akt precedes tumor remission after switching-off HER-2 and (ii) downregulation of BXB-Raf1 leads to a similarly efficient tumor remission as downregulation of HER-2, although no p-Akt dephosphorylation was observed after switching-off BXB-Raf1.
    No preview · Article · May 2006 · Molecular Carcinogenesis
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    ABSTRACT: The receptor tyrosine kinase ERBB2 plays a central role in the development of breast cancer and other epithelial malignancies. Elevated ERBB2 activity is believed to transform cells by transmitting mitogenic and antiapoptotic signals. Here we show that tightly regulated overexpression of oncogenic ERBB2 in human breast carcinoma cells does not stimulate proliferation but provokes premature senescence, accompanied by up-regulation of the cyclin-dependent kinase inhibitor P21(WAF1/CIP1). A similar effect was caused by retrovirus-mediated overexpression of oncogenic ERBB2 in low-passage murine embryonic fibroblasts. In contrast to previous observations based on constitutively overexpressing cell lines, P21 induced by tetracycline-regulated ERBB2 localizes to the nucleus in arrested cells. P21 up-regulation seems to be independent of the P53 tumor suppressor protein, and senescence-associated phenotypic alterations are reversed by specific inhibition of P38 mitogen-activated protein kinases. Functional inactivation of P21 by antisense oligonucleotides is sufficient to prevent cell cycle arrest as well as the senescent phenotype, thereby identifying the P21 protein as the key mediator of hypermitogenic cell cycle arrest and premature senescence in breast carcinoma cells. Our results may thus indicate that premature senescence represents an inherent anticarcinogenic program during ERBB2-driven mammary tumorigenesis. We propose a multistep model for the process of malignant transformation by ERBB2 wherein secondary lesions either target P21 or downstream effectors of senescence to bypass this primary fail-safe mechanism.
    Full-text · Article · Mar 2005 · Cancer Research
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    ABSTRACT: Since the pioneering work by Gossen and Bujard in 1992 demonstrating the usefulness of the Escherichia coli derived tet resistance operon for regulating gene expression a large collection of doxycycline-controlled transgenic mice has been established. Gene switching in eukaryotic tissue culture cells or mice requires administration of tetracycline, anhydrotetracycline or doxycycline to efficiently inactivate the transactivator protein tTA (TET-OFF system) or alternatively to activate the reverse transactivator protein rtTA (TET-ON system). However, the antibiotic activity of doxycycline can create an imbalance of the intestinal flora, resulting in diarrhoea and in a smaller number of animals in colitis. Previous studies reported that 4-epidoxycycline (4-ED), a hepatic metabolite of doxycycline, does not function as an antibiotic in mice. This gave us the idea that 4-ED might be useful for controlling gene expression in mice without the unwanted antibiotic side effect. To study the applicability of 4-ED for control of gene expression we used cell lines expressing the oncogene HER2 under control of tTA (TET-OFF) as well as rtTA (TET-ON). 4-ED and doxycycline were similarly efficient in switching on or -off HER2 expression. In vivo we used a conditional mouse model that allows switching off HER2 in tumor tissue. We show that (i) doxycycline, 7.5mg/ml in drinking water (used as a positive control), (ii) 4-ED, 7.5mg/ml in drinking water, (iii) 4-ED, 10mg/kg body weight, s.c., and (iv) anhydrotetracycline, 10mg/kg, s.c. (used as a second positive control), were similarly efficient. Using mice with tumor volumes of 1.6cm(3) all four schedules led to a tumor remission of more than 95% within 7 days. In conclusion, 4-ED is similarly efficient as doxycycline to control gene expression in vitro and in mice. Since 4-ED lacks the antibiotic activity of doxycycline it may help to avoid adverse side effects and selection of resistant bacteria.
    Full-text · Article · Nov 2004 · Biochemical and Biophysical Research Communications

  • No preview · Article · Aug 2004 · Geburtshilfe und Frauenheilkunde
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    ABSTRACT: Apurinic/apyrimidinic endonuclease (APE alias Ref-1) is a key enzyme in the base excision repair pathway. Besides its function in DNA repair, APE serves to maintain several transcription factors in an active reduced state such as c-Fos, c-Jun, NF-kappaB, p53 and HIF-1alpha, all of which have been shown to play a role in tumorigenesis. Because of the importance of APE in maintaining genomic stability and gene regulation, we examined whether APE expression is associated with survival and histopathological parameters of patients with ovarian cancer. Tissue sections of primary epithelial ovarian carcinomas from 141 patients were immunostained using a monoclonal antibody directed against APE. Nuclear expression of APE was clearly associated with progression of ovarian carcinomas. Patients with Federation of Gynecology and Obstetrics (FIGO) stages III and IV showed a higher nuclear APE expression level than patients with FIGO stages I and II (P < 0.0001). Similarly, nuclear APE expression was associated with histological grading (grade 1 vs. 2 vs. 3; P = 0.025). In contrast, cytoplasmic and stromal APE expression were not associated with progression. The fraction of APE-positive nuclei (P = 0.0185), the intensity of nuclear staining (P = 0.0496) and a combination of both (P = 0.0070) were associated with survival of ovarian cancer patients, as evidenced by a univariable proportional hazards model. Multivariable analysis, adjusted to FIGO stage, histological grade and type as well as residual tumor after surgery showed that APE is not independent from "classical" prognostic factors of ovarian cancer. An unexpected observation was the inverse correlation between nuclear and cytoplasmic expression of APE. Tumors with strong cytoplasmic APE reactivity showed a higher fraction of APE-negative nuclei than tumors with weak or negative cytoplasmic APE expression (P = 0.045). This suggests that nuclear translocation of APE is impaired during ovarian carcinogenesis. In conclusion, we have shown that nuclear APE expression increases during tumor progression. This suggests that increased base excision repair capacity and/or APE-mediated activation of transcription factors may contribute to more aggressive proliferation of ovarian carcinomas.
    No preview · Article · Mar 2004 · Gynecologic Oncology

  • No preview · Article · Jan 2004 · Geburtshilfe und Frauenheilkunde
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    ABSTRACT: Overexpression of the receptor tyrosine kinase HER-2/neu is associated with poor prognosis in patients with breast and ovarian cancer. Recent excitement has surrounded the therapeutic effects of HER-2-blocking therapy strategies and has rekindled interest on the molecular mechanisms of HER-2/neu in tumor biology. To study the role of HER-2/neu overexpression in vivo, we used a murine fibroblast cell line (NIH3T3-her2) conditionally expressing human HER-2/neu under control of a tetracycline-responsive promoter. Expression of HER-2 could be down-regulated below detection limit (>625-fold dilution) by exposure of NIH3T3-her2 cells to anhydrotetracycline (ATc). Subcutaneous injection of NIH3T3-her2 cells into nude mice resulted in rapid tumor growth. Mice with mean tumor volumes of 0.2, 0.8, 1.9, and 14.9 cm(3) were treated daily with 10 mg/kg ATc to switch off HER-2/neu expression, producing reductions in tumor size of 100, 98.1, 81.4, and 74.2%, respectively, by 7 days after onset of ATc administration (P = 0.005, Kruskal-Wallis test). Different long-term effects of HER-2 down-regulation were observed when mice with small (0.2 cm(3); n = 7), intermediate (0.8-1.2 cm(3); n = 10) and large (> or =1.9 cm(3); n = 11) tumors received ATc for up to 40 days. Complete remission was observed for 100, 40, and 18% of the small-, intermediate-, and large-sized tumors, respectively (P = 0.003). However, after 20-45 days of ATc administration, recurrent tumor growth was observed for all mice, even in those with previous complete remissions. The time periods for which mean tumor volume could be suppressed to volumes <0.1 cm(3) under ATc administration were 34, 22, 8, and 0 days for tumors with initial volumes of 0.2, 0.8, 1.9 and 14.9 cm(3), respectively (P = 0.005, Kruskal-Wallis test). Interestingly, HER-2 remained below the detection limit in recurrent tumor tissue, suggesting that initially HER-2-dependent tumors switched to HER-2 independence. The "second hits" leading to HER-2-independent tumor growth have not yet been identified. The rapid regression of tumors after down-regulation of HER-2 was explained by two independent mechanisms: (a) a block in cell cycle progression, as evidenced by a decrease in Ki-67 antigen expression from 40% before ATc treatment to 8.3% after 7 days of ATc treatment; and (b) induction of apoptosis as demonstrated by caspase-3 activation and by the terminal deoxynucleotidyltransferase (Tdt)-mediated nick end labeling assay (TUNEL). In conclusion, we have shown that switching off HER-2 may disturb the sensitive balance between cell proliferation and cell death, leading to apoptosis and tumor remission. Tumor remission was dependent on the volume of the tumors before down-regulation of HER-2/neu.
    Full-text · Article · Nov 2003 · Cancer Research
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    ABSTRACT: The purpose of this study was to examine whether exposure to magnetic fields (MFs) relevant for magnetic resonance imaging (MRI) in clinical routine influences cell cycle progression in two tumor cell lines in vitro. HL60 and EA2 cells were exposed to four types of MFs: (i) static MF of 1.5 and 7.05 T, (ii) extremely low frequency magnetic gradient fields (ELFMGFs) with +/- 10 mT/m and 100 Hz, as well as +/- 100 mT/m and 100 Hz, (iii) pulsed high frequency MF in the radiofrequency (RF) range (63.6 MHz, 5.8 microT), and (iv) a combination of (i-iii). Exposure periods ranged from 1 to 24 h. Cell cycle distribution (G(0)/G(1), S, and G(2)/M phases) was analyzed by flow cytometry. Cell cycle analysis did not reveal differences between the exposed and the control cells. As expected, positive controls with irradiated (8 Gy) HL60 and EA2 cells showed a strong G(2)/M arrest. Using conditions that are relevant for patients during MRI, no influence of MFs on cell cycle progression was observed in these cell lines. Care was taken to control secondary parameters of influence, such as vibration by the MR scanner or temperature to avoid false positive results.
    No preview · Article · May 2003 · Bioelectromagnetics
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    ABSTRACT: Recently, the combination of ionizing radiation with inhibitors of angiogenesis has been reported to improve tumor eradication compared to treatment with irradiation alone. However, the mechanisms of this effect have not been defined. For this purpose [corrected] we established a non-small cell lung cancer model in nude mice. Tumor vascularization was visualized in vivo by MRI using gadolinium-DTPA as contrast agent. Further, cryosections were produced as close as possible to the MRI slice positions. Since we were interested in examining the formation of a recurrent tumor, irradiation was performed with a single fraction of 4 Gy. This dose caused a partial remission followed by recurrent tumor growth 25 to 35 days after therapy. The process of partial remission as well as formation of the recurrent tumor was examined in 28 nude mice analysing the following parameters: (i) contrast agent enhancement using high-resolution MRI, (ii) proliferation of tumor cells and fibroblasts using Ki-67 immunohistochemistry and (iii) formation of microvessels using CD31 immunohistochemistry. The latter analyses led to differentiation of three stages. Stage 1 (day 1 to day 15 after irradiation) was characterized by increasing areas of dead cell mass in hematoxylin-eosin-stained slides that corresponded to a decrease in tumor cell proliferation as well as contrast agent enhancement in MRI. The percentage of Ki-67-positive tumor cells decreased from initially 45.1% +/- 6.0% (mean +/- standard deviation) to 1.4% +/- 1.2% (mean +/- standard deviation) on day 15. Stage 2 (day 6 to day 20 after irradiation; overlapping with stage 1) was characterized by proliferation of fibroblasts leading to formation of fibrotic septae with abundant microvessels. Already during late stage 2, MRI identified new contrast agent enhancing areas. Stage 3 (day 20 to day 40 after irradiation) was characterized by new tumor cell proliferation. Interestingly, tumor cells almost exclusively proliferated in the direct neighbourhood of the fibrotic septae that had been formed in stage 2. Obviously, proliferation of fibroblasts and blood vessels was a condition prior to formation of recurrent tumor tissue. Thus, our results are in contrast with the view that tumors or recurrent tumors begin as avascular masses that later induce neovascularization. With respect to clinical practice, our results suggest that: (i) adjuvant anti-angiogenic therapy should not be limited to the day of irradiation but should cover a critical period until day 5 to day 20 after radiotherapy, (ii) adjuvant therapy should also include inhibition of fibroblast proliferation and (iii) MRI can identify a recurrent tumor 10 to 15 days before occurrence of new tumor growth.
    No preview · Article · Mar 2002 · Anticancer research
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    ABSTRACT: Mutagenic and co-mutagenic effects of static, pulsed bipolar gradient, and high-frequency magnetic fields, as well as combinations of them, were examined using the Ames test. The Ames test using Salmonella typhimurium bacteria, wild-type strain RTA, preincubation assay, without metabolic activation, was performed. All combinations of magnetic fields were tested with and without co-exposure to N-methyl-N'-nitro-N-nitrosoguanidine and benzo[a]pyrene-4,5-oxide, ethylene oxide, carboplatin, or cisplatin. As expected, chemical mutagens caused a clear-cut increase of the revertants in the Ames test. However, neither the static fields nor a combination of a static magnetic field with the time-varying bipolar gradient field or a pulsed high-frequency magnetic field caused an alteration in the number of revertants in the Ames test. No co-mutagenic effect of any magnetic field combination was observed. In conclusion, magnetic fields used during clinical magnetic resonance imaging (MRI) were neither mutagenic nor co-mutagenic.
    No preview · Article · Jan 2002 · Journal of Magnetic Resonance Imaging
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    ABSTRACT: DNA topoisomerases are nuclear enzymes inducing transient breaks in the DNA allowing DNA strands or double helices to pass through each other. The clinically used DNA topoisomerase II-poison etoposide is known to induce DNA double strand breaks leading to chromosomal aberrations and leukemias. Recently, some alarming studies have been published, suggesting that maternal exposure to low doses of dietary topoisomerase II-poisons, including bioflavonoids such as genistein or quercetin, may contribute to the development of infant leukemia: approximately 80% of infants with acute myelogenous leukemia (AML) and acute lymphoblastic leukemia (ALL) have chromosome translocations involving the MLL (mixed lineage leukemia) gene. It has been shown that antineoplastic chemotherapy with the leukemogenic topoisomerase II-poison etoposide induced identical chromosomal aberrations involving the MLL gene compared to children with infant leukemia. Interestingly, the MLL cleavage sites induced by etoposide colocalized with the cleavage sites observed in infant leukemia. In addition, an almost 10-fold higher risk of infant AML has been reported for mothers consuming relatively high levels of topoisomerase II-poison containing foods. These observations are relevant, since many foods contain topoisomerase II-poisons, predominantly soy and soy products, but also coffee, wine, tea, cocao, as well as some fruits and vegetables. Further studies on the role of dietary topoisomerase II-poisons are urgently required. If the causal relationship between dietary exposure to topoisomerase II-poisons and infant leukemia will be confirmed, care should be taken to reduce exposure to critical foods during pregnancy.
    Preview · Article · Jan 2002 · EXCLI Journal

  • No preview · Article · Jul 2001
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    ABSTRACT: Aim of our study was to investigate the efficacy of 7 F cryoprobes for percutaneous use morpho- and histologically, to examine the role of apoptosis after cryotherapy, and to compare contrast-enhanced MRI with histopathological findings at different time intervals in a tumor-mouse model. Percutaneous cryotherapy was performed in 15 immunocompromised nude mice with subcutaneously implanted tumors using the non-small-cell lung cancer cell line Lu 1. In group a) 7 mice were sacrificed after definite time intervals and histological examinations were done for evaluation of necrosis and apoptosis (HE; TUNEL assay); 2 mice are in long-term follow-up. In group b) in 6 mice tumor destruction and perfusion before and after freezing were investigated with native and contrast-enhanced MR imaging (T1- and T2-weighted spin-echo) and compared with histopathological findings. Histological control were done in 2 untreated mice. We observed fast tumor-reduction within two weeks (ca. 50%). On long-term follow-up (> 6 months) no recurrence has been noticed so far. Tumors were well vascularized prior to treatment and did not-show contrast enhancement an any time after cryotherapy. A narrow contrast-enhanced zone was seen on the tumor border subcutaneously as a sign of peripheral hyperemia and central vascular stasis after cryotherapy. On histology there was evidence of both apoptosis and necrosis. We have established a tumor-mouse model for further investigations. Two minutes freezing of a 2-cm tumor in the mouse model is sufficient for tumor ablation with scarred healing. Apoptosis may play a role in cryotherapy of experimental tumors. Contrast-enhanced MRI is suitable for the estimation of the cryolasion.
    No preview · Article · Jul 2001 · RöFo - Fortschritte auf dem Gebiet der R

Publication Stats

541 Citations
96.21 Total Impact Points


  • 2000-2008
    • Johannes Gutenberg-Universität Mainz
      • • III. Department of Medicine
      • • Department of Ecology
      • • Institute of Toxicology
      • • Klinik und Poliklinik für Radioonkologie und Strahlentherapie
      Mayence, Rheinland-Pfalz, Germany
  • 2004
    • University of Leipzig
      • Rudolf Boehm Institute of Pharmacology and Toxicology
      Leipzig, Saxony, Germany