The neurobeachin gene spans the common fragile site FRA13A

Common fragile sites are normal constituents of chromosomal structure prone to chromosomal breakage. In humans, the cytogenetic locations of more than 80 common fragile sites are known. The DNA at 11 of them has been defined and characterized at the molecular level. According to the Genome Database, the common fragile site FRA13A maps to chromosome band 13q13.2. Here, we identify the precise genomic position of FRA13A, and characterize the genetic complexity of the fragile DNA sequence. We show that FRA13A breaks are limited to a 650 kb region within the neurobeachin (NBEA) gene, which genomically spans approximately 730 kb. NBEA encodes a neuron-specific multidomain protein implicated in membrane trafficking that is predominantly expressed in the brain and during development.

Preclinical Evaluation of the Breast Cancer Cell-Binding Peptide, p160

PURPOSE

Selective delivery of drugs into the target tissue is expected to result in high drug concentrations in the tissue of interest and therefore enhanced drug efficacy. To develop a peptide-based radiopharmaceutical, we investigated the properties of a peptide with affinity for human breast cancer, which has been selected through phage display.

EXPERIMENTAL DESIGN

The bioactivity of the p160 peptide (VPWMEPAYQRFL) was evaluated in vitro and in vivo. The specific binding to human breast cancer MDA-MB-435 cells was confirmed in competition experiments. Internalization of the peptide was investigated with confocal microscopy. Furthermore, the biodistribution of (131)I-labeled p160 was studied in tumor-bearing mice. In vivo stability was evaluated at different periods after tracer administration using high-performance liquid chromatography analysis.

RESULTS

The binding of (125)I-labeled p160 was inhibited up to 95% by the unlabeled peptide with an IC(50) value of 0.6 micromol/L. In addition, 40% of the total bound activity was found to be internalized into the human breast cancer cells. Although a rapid degradation was seen, biodistribution studies in nude mice showed a higher uptake in tumor than in most of the organs. Perfusion of the animals caused a reduction of the radioligand accumulation in the healthy tissues, whereas the tumor uptake remained constant. A comparison of [(131)I]p160 with a (131)I-labeled Arg-Gly-Asp peptide revealed a higher tumor-to-organ ratio for [(131)I]p160.

CONCLUSIONS

p160 has properties that make it an attractive carrier for tumor imaging and the intracellular delivery of isotopes or chemotherapeutic drugs.

Inferring a tumor progression model for neuroblastoma from genomic data

PURPOSE

The knowledge of the key genomic events that are causal to cancer development and progression not only is invaluable for our understanding of cancer biology but also may have a direct clinical impact. The task of deciphering a model of tumor progression by requiring that it explains (or at least does not contradict) known clinical and molecular evidence can be very demanding, particularly for cancers with complex patterns of clinical and molecular evidence.

MATERIALS AND METHODS

We formalize the process of model inference and show how a progression model for neuroblastoma (NB) can be inferred from genomic data. The core idea of our method is to translate the model of clonal cancer evolution to mathematical testable rules of inheritance. Seventy-eight NB samples in stages 1, 4S, and 4 were analyzed with array-based comparative genomic hybridization.

RESULTS

The pattern of recurrent genomic alterations in NB is strongly stage dependent and it is possible to identify traces of tumor progression in this type of data.

CONCLUSION

A tumor progression model for neuroblastoma is inferred, which is in agreement with clinical evidence, explains part of the heterogeneity of the clinical behavior observed for NB, and is compatible with existing empirical models of NB progression.

Effects of aminosalicylates on thiopurine S-methyltransferase activity: an ex vivo study in patients with inflammatory bowel disease

BACKGROUND

Based on in vitro experiments using recombinant human thiopurine S-methyltransferase this enzyme is inhibited by sulfasalazine (sulphasalazine) and 5-aminosalicylate. Thus, during treatment with azathioprine or mercaptopurine, both metabolized by thiopurine S-methyltransferase, sulfasalazine or 5-aminosalicylate could modify the action of azathioprine/mercaptopurine.

AIMS

To examine whether this interaction is effective under ex vivo conditions.

METHODS

In 18 azathioprine-free patients and in 12 patients on azathioprine the inhibitory potential of sulfasalazine, 5-aminosalicylate and its metabolite (Ac-5-aminosalicylate) was assessed by ex vivo measurement of thiopurine S-methyltransferase in red blood cells.

RESULTS

According to concentration response curves mean IC50 values (microm) for sulfasalazine, 5-aminosalicylate and Ac-5-aminosalicylate have been calculated in three groups of azathioprine-free patients and variable basal levels of thiopurine S-methyltransferase activity (very high, normal and intermediate). In all three groups sulfasalazine was the strongest inhibitor (IC50: 9-17 microm) if compared with 5-aminosalicylate (129-236) and Ac-5-aminosalicylate (58-74). In patients on azathioprine similar IC50 values have been calculated.

CONCLUSIONS

Comparing human plasma concentrations of sulfasalazine (15-77 microm), 5-aminosalicylate (3-14 microm) and Ac-5-aminosalicylate (8-18 microm) with the IC50 values one can assume that only sulfasalazine would have the potential to inhibit thiopurine S-methyltransferase in vivo. However, the therapeutic impact should be proved by clinical studies.

Comprehensive analysis of pyrimidine metabolism in 450 children with unspecific neurological symptoms using high-pressure liquid chromatography-electrospray ionization tandem mass spectrometry

To evaluate the significance of inborn metabolic disorders of the pyrimidine degradation pathway, 450 children with unspecific neurological symptoms were comprehensively studied; 200 healthy children were recruited as controls. Uracil and thymine as well as their degradation products in urine were determined with an improved method based on reversed-phase HPLC coupled with electrospray ionization tandem mass spectrometry and detection by multiple-reaction monitoring using stable-isotope-labelled reference compounds as internal standards. From the results of the control group we established age-related reference ranges of all pyrimidine degradation products. In the patient group, two children with dihydropyrimidine dehydrogenase (DPYD) deficiency were identified; one of these was homozygous for the exon 14-skipping mutation of the DPYD gene. In addition, two patients with high uracil, dihydrouracil and beta-ureidopropionate were found to have ornithine transcarbamylase deficiency. In the urine of 9 patients, beta-alanine was markedly elevated owing to treatment with vigabatrin, an irreversible inhibitor of GABA transaminase, which interferes with beta-alanine breakdown. Four patients had exclusively high levels of beta-aminoisobutyrate (beta-AIB) due to a low activity of the D-beta-AIB-pyruvate aminotransferase, probably without clinical significance. In conclusion, quantitative investigation of pyrimidine metabolites in children with unexplained neurological symptoms, particularly epileptic seizures with or without psychomotor retardation, can be recommended as a helpful tool for diagnosis in clinical practice. Sensitive methods and age-related reference ranges enable the detection of partial enzyme deficiencies.

Prediction of clinical outcome using gene expression profiling and artificial neural networks for patients with neuroblastoma

Currently, patients with neuroblastoma are classified into risk groups (e.g., according to the Children's Oncology Group risk-stratification) to guide physicians in the choice of the most appropriate therapy. Despite this careful stratification, the survival rate for patients with high-risk neuroblastoma remains <30%, and it is not possible to predict which of these high-risk patients will survive or succumb to the disease. Therefore, we have performed gene expression profiling using cDNA microarrays containing 42,578 clones and used artificial neural networks to develop an accurate predictor of survival for each individual patient with neuroblastoma. Using principal component analysis we found that neuroblastoma tumors exhibited inherent prognostic specific gene expression profiles. Subsequent artificial neural network-based prognosis prediction using expression levels of all 37,920 good-quality clones achieved 88% accuracy. Moreover, using an artificial neural network-based gene minimization strategy in a separate analysis we identified 19 genes, including 2 prognostic markers reported previously, MYCN and CD44, which correctly predicted outcome for 98% of these patients. In addition, these 19 predictor genes were able to additionally partition Children's Oncology Group-stratified high-risk patients into two subgroups according to their survival status (P = 0.0005). Our findings provide evidence of a gene expression signature that can predict prognosis independent of currently known risk factors and could assist physicians in the individual management of patients with high-risk neuroblastoma.

NOD2 (CARD15) mutations in Crohn's disease are associated with diminished mucosal alpha-defensin expression

BACKGROUND

Mutations in NOD2, a putative intracellular receptor for bacterial peptidoglycans, are associated with a subset of Crohn's disease but the molecular mechanism linking this protein with the disease pathogenesis remains unclear. Human alpha defensins (HD-5 and HD-6) are antibiotic effector molecules predominantly expressed in Paneth cells of the ileum. Paneth cells also express NOD2. To address the hypothesis that the function of NOD2 may affect expression of Paneth cell defensins, we compared their expression levels with respect to NOD2 mutations in Crohn's disease.

METHODS

Forty five Crohn's disease patients (24 with NOD2 mutations, 21 with wild-type NOD2) and 12 controls were studied. Real time reverse transcription-polymerase chain reaction was performed with mucosal mRNA for HD-5, HD-6, lysozyme, secretory phospholipase A2 (sPLA2), tumour necrosis factor alpha, interleukin 8, and human hypoxanthine phosphoribosyltransferase (housekeeping gene). Immunohistochemistry with anti-HD-5 and histological Paneth cell staining were performed in 10 patients with NOD2 mutations or wild-type genotypes.

RESULTS

Ileal expression of HD-5 and HD-6, but not sPLA2 or lysozyme, were diminished in affected ileum, and the decrease was significantly more pronounced in patients with NOD2 mutations. In the colon, HD-5, HD-6, and sPLA2 were increased during inflammation in wild-type but not in NOD2 mutated patients. In both the colon and ileum, proinflammatory cytokines and lysozyme were unaffected by NOD2 status. Immunohistochemistry identified Paneth cells as the sole source of HD-5.

CONCLUSION

As alpha defensins are important in the mucosal antibacterial barrier, their diminished expression may explain, in part, the bacterial induced mucosal inflammation and ileal involvement of Crohn's disease, especially in the case of NOD2 mutations.

cDNA array-CGH profiling identifies genomic alterations specific to stage and MYCN-amplification in neuroblastoma

Background

Recurrent non-random genomic alterations are the hallmarks of cancer and the characterization of these imbalances is critical to our understanding of tumorigenesis and cancer progression.

Results

We performed array-comparative genomic hybridization (A-CGH) on cDNA microarrays containing 42,000 elements in neuroblastoma (NB). We found that only two chromosomes (2p and 12q) had gene amplifications and all were in the MYCN amplified samples. There were 6 independent non-contiguous amplicons (10.4–69.4 Mb) on chromosome 2, and the largest contiguous region was 1.7 Mb bounded by NAG and an EST (clone: 757451); the smallest region was 27 Kb including an EST (clone: 241343), NCYM, and MYCN. Using a probabilistic approach to identify single copy number changes, we systemically investigated the genomic alterations occurring in Stage 1 and Stage 4 NBs with and without MYCN amplification (stage 1-, 4-, and 4+). We have not found genomic alterations universally present in all (100%) three subgroups of NBs. However we identified both common and unique patterns of genomic imbalance in NB including gain of 7q32, 17q21, 17q23-24 and loss of 3p21 were common to all three categories. Finally we confirm that the most frequent specific changes in Stage 4+ tumors were the loss of 1p36 with gain of 2p24-25 and they had fewer genomic alterations compared to either stage 1 or 4-, indicating that for this subgroup of poor risk NB requires a smaller number of genomic changes are required to develop the malignant phenotype.

Conclusions

cDNA A-CGH analysis is an efficient method for the detection and characterization of amplicons. Furthermore we were able to detect single copy number changes using our probabilistic approach and identified genomic alterations specific to stage and MYCN amplification.

Increased rates of spontaneous sister chromatid exchange in lymphocytes of BRCA2+/- carriers of familial breast cancer clusters

Heterozygous carriers of germ-line mutations of the BRCA2 breast cancer susceptibility gene are predisposed to breast, ovarian, pancreatic and other cancers. The BRCA2 protein is implicated in the maintenance of chromosome stability through its essential function in double-strand DNA repair and recombination. Our previous studies had revealed multiple intrachromosomal rearrangements, duplications, inversions and deletions on 9p23-24 in lymphocytes and fibroblasts of BRCA2+/- members from independently ascertained familial breast cancer clusters. In pursuit of evaluating if there is a subtle genomic instability in BRCA2+/- individuals, we have determined frequencies of spontaneous sister chromatid exchanges (SCEs) in BRCA2 wild-types and BRCA2 mutation carriers of two familial breast cancer clusters. Here, we demonstrate an average increase of 65% of spontaneous SCEs in BRCA2+/- versus BRCA2+/+ family members. In one cluster, the number of metaphases with multiple SCEs was 5-times higher in BRCA2+/- compared to wild-type members, while in the second cluster BRCA2+/- members had 8.9% of metaphases with multiple SCEs compared to a level below detection in BRCA2 wild types. To investigate the correlation between SCE and genomic instability in 9p, we performed fluorescence detection of SCEs and FISH analysis with 9p probes. The frequency of SCE in 9p of BRCA2 mutation carriers was 3-4 fold (P = 0.005) higher compared to BRCA2 wild-types. Collectively, the increased rates of SCE in BRCA2 heterozygous mutation carriers indicate a BRCA2 haploinsufficiency, which might be an important factor for the accumulation of structural chromosomal alterations with the consequence of damage in as yet unidentified genes.

Thioguanine-nucleotides do not predict efficacy of tioguanine in Crohn's disease

BACKGROUND

6-Thioguanine-nucleotides seem to be the active metabolites of thiopurine therapy, and their monitoring has been considered a useful tool for optimizing response in inflammatory bowel diseases. Tioguanine (thioguanine) therapy results in much higher levels of 6-thioguanine-nucleotide levels when compared with azathioprine or mercaptopurine.

AIM

To elucidate the influence of 6-thioguanine-nucleotide and methylated 6-thioguanine-nucleotide levels under tioguanine on efficacy and toxicity in Crohn's disease.

METHODS

6-Thioguanine-nucleotide and methylated 6-tioguanine-nucleotide levels were measured regularly in 26 Crohn's disease patients treated with tioguanine. Nucleotide levels were related to efficacy and toxicity.

RESULTS

6-Thioguanine-nucleotide levels rose very high [median 1241 pmol/8 x 10(8) red blood cells (range 313-1853)]. Methylated 6-thioguanine-nucleotide levels were detected in all patients [491 pmol/8 x 10(8) red blood cells (154-1775)]. 6-Thioguanine-nucleotide and methylated 6-thioguanine-nucleotide concentrations correlated significantly (r = 0.7, P < 0.0001). Nucleotide levels from patients achieving remission (n = 14) did not differ significantly from non-remitters (n = 12) [6-thioguanine-nucleotide: 1077 (599-2160) vs. 1210 (534-4665); methylated 6-thioguanine-nucleotide: 510 (214-1222) vs. 421 (145-1284)]. One patient with intermediate thiopurine S-methyltransferase activity experienced bone marrow toxicity upon dose escalation parallel with excessively high thioguanine-nucleotide levels.

CONCLUSIONS

6-Thioguanine-nucleotide as well as methylated 6-thioguanine-nucleotide levels under tioguanine therapy were not related to efficacy. This suggests that monitoring of 6-thioguanine-nucleotide levels is not a useful tool to predict response to thiopurines.

[Treatment of recurrent neurocardiogenic syncope with cardiac inhibitors with ipratropium bromide]

Pharmacological approaches for the treatment of cardioinhibitory vasovagal syncope are controversially discussed in the literature. In acute treatment of neurocardiogenic syncope, anticholinergics (atropine) are used effectively. Randomised and placebo-controlled clinical trials evaluating the preventive significance of anticholinergic agents in the therapy of cardioinhibitory vasovagal syncope are still missing. We report the case of an 18-year-old male patient with recurrent convulsive, cardioinhibitory neurocardiogenic syncope. Vasovagal syncope occurred predominantly as centrally induced syncope triggered by negative emotions such as fear or by seeing blood. Under resting conditions, the patient revealed increased parasympathetic tone with nocturnal bradycardia of 38 beats/min. In the course of head-up tilt table testing a cardioinhibitory syncope with an asystolic pause of 10 seconds occurred without any prodromes after 10 minutes of upright positioning. In order to inhibit parasympathetic tone, medication with ipratropiumbromide was initiated. Time-variant analysis of heart rate variability (autoregressive model) during head-up tilt table testing showed under the medication with ipratropiumbromide a vagal mediated cardioinhibition to 56 beats/min, but no further sinus arrest. Throughout clinical follow-up of 6 months the patient remained syncope-free under the medication. The usefulness of ipratropiumbromide in inhibiting vagal mediated cardioinhibition will be discussed referring to the case report and to studies evaluating anticholinergic agents in the treatment of neurocardiogenic syncope.

Enhanced expression of MYCN leads to centrosome hyperamplification after DNA damage in neuroblastoma cells

Centrosomes play important roles in cell polarity, regulation of cell cycle and chromosomal stability. Centrosome abnormality is frequently found in many cancers and contributes to chromosomal instability (including aneuploidy, tetraploidy, and/or micronuclei) in daughter cells through the assembly of multipolar or monopolar spindles during mitosis. It has recently been reported that loss of tumor suppressor genes or overexpression of oncogenes causes centrosome hyperamplification. Amplification and overexpression of the MYCN oncogene is found in a subgroup of neuroblastomas. In this study, we examined whether overexpression of MYCN causes centrosome hyperamplification in neuroblastoma cells. We show that ectopic expression of MYCN alone in a neuroblastoma cell line did not cause centrosome hyperamplification. However, centrosome hyperamplification and micronuclei formation were seen in these cells after DNA damage. These findings suggest that overexpression of MYCN abrogates the regulation of the centrosome cycle after DNA damage.

MYCN in neuronal tumours

MYCN is a member of the MYC family of oncogenes that encode nuclear proteins serving as transcription factors. Activation of MYC family genes, usually by genetic damage with the consequence of enhanced expression of a wild-type protein, has been found to participate in human and animal cancers. While activation of the MYC oncogene does not show an association with a particular cancer type, genetic damage involving MYCN has high preference for tumours of neuroectodermal derivation. In the vast majority of cases, the activation mechanism involves the increase of the MYCN gene dosage, either by amplification resulting in up to several hundred gene copies or by more subtle mechanisms, like duplication or polyploidization. In neuroblastoma, amplified MYCN is a strong prognostic indicator of poor prognosis, particularly in localized tumors where patients with normal MYCN gene dosage fare quite well. Identification of amplified MYCN in neuroblastomas has marked the clinical debut of oncogenes, and MYCN status now is being used world wide as a standard marker for neuroblastoma stratification.

Exciton dephasing in quantum dot molecules

We have measured the exciton dephasing time in InAs/GaAs quantum dot molecules having different interdot barrier thicknesses in the temperature range from 5 to 60 K, using a highly sensitive four-wave mixing heterodyne technique. At 5 K dephasing times of several hundred picoseconds are found. Moreover, a systematic dependence of the dephasing dynamics on the barrier thickness is observed. These results show how the quantum-mechanical coupling of the electronic wave functions in the molecules affects both the exciton radiative lifetime and the exciton-acoustic phonon interaction.

Neuroblastoma-derived sulfhydryl oxidase, a new member of the sulfhydryl oxidase/Quiescin6 family, regulates sensitization to interferon gamma-induced cell death in human neuroblastoma cells

In neuroblastoma cells, apoptotic programs can be activated by cytokines and cytostatic drugs. Apoptotic dysfunction confers resistance against therapeutic drugs and is a major complication for achieving optimal therapy response. Deregulated expression of the MYCN gene is a critical determinant in neuroblastoma progression, and one of the pleiotropic functions of the MYCN protein is cellular sensitization to cytokine-induced and drug-induced apoptosis. By using the functional approach of technical knockout (TKO), we have identified five genes that regulate sensitization for IFN-gamma-induced cell death. Most efficient among them is the newly identified SOXN (neuroblastoma-derived sulfhydryl oxidase), which comprises 12 exons and maps to 9q34.3. SOXN encodes a putative protein of 698 amino acids that contains a signal sequence, a protein-disulfide-isomerase-type thioredoxin and a yeast ERV1 domain and is highly homologous to members of the sulfhydryl oxidase/Quiescin6 family. The SOXN protein is predominantly located in the plasma and in the nuclear membrane. Antisense SOXN confers resistance to IFN-gamma-induced apoptosis. In contrast, ectopic overexpression of sense-SOXN sensitizes the cells to induced cell death. These results identify SOXN as a major player in regulating the sensitization of neuroblastoma cells for IFN-gamma-induced apoptosis.

Aflatoxin B1 aldehyde reductase (AFAR) genes cluster at 1p35-1p36.1 in a region frequently altered in human tumour cells

Alterations of the distal portion of the short arm of chromosome 1 (1p) are among the earliest abnormalities of human colorectal tumours. Recently, we have cloned the Aflatoxin B1 aldehyde reductase (AFAR) gene from a smallest region of overlapping deletion that is frequently (48%) hemizygously deleted in sporadic colorectal cancer. AFAR is expressed in a broad range of tissues. Its closely related rat protein is the major factor conferring resistance of rats towards aflatoxin B1-induced liver carcinogenesis. Here, we have identified cDNAs covering two additional human AFAR-related genes localized in close proximity to the previously described AFAR at 1p35-36. We have analysed their structure and tissue-related expression. One of them, AFAR3, carries a Selenocysteine-Insertion Element (SECIS)-like structure that during translation may recode an in-frame TGA-stop codon to a selenocysteine. Two additional AFAR-pseudogenes are localized at Xq25 and 1p12, respectively. AFAR exon sequences share an identity of DNA and amino acids of more than 78%. Also large blocks of intronic sequences can be up to 98.6% identical. Knowledge of the AFAR genes and their structure will be essential in genetic and functional studies, where discrimination of the genes and proteins is a prerequisite for evaluating their individual functions.

Remission maintenance by tioguanine in chronic active Crohn's disease

BACKGROUND

Tioguanine may offer an alternative for immunosuppression in chronic active Crohn's disease. Recently, we have shown that tioguanine is effective in inducing rapid remission.

AIM

To evaluate the role of tioguanine in the maintenance of remission in chronic active Crohn's disease.

METHODS

A follow-up study was performed to investigate the long-term efficacy and safety of and tolerance to tioguanine in chronic active Crohn's disease. Sixteen patients who had successfully received 6-tioguanine for remission induction were enrolled. The reasons for immunosuppressive therapy were steroid dependence (n = 10), steroid refractoriness (n = 6) and intolerance (n = 6) or refractoriness (n = 1) to azathioprine. After remission induction therapy for 6 months, patients were treated for another 6 months with a daily dose of 20-40 mg tioguanine. Primary outcomes were remission (Crohn's disease activity index < 150) and complete steroid reduction in steroid-dependent patients at 12 months. Laboratory controls of white blood count and liver enzymes, as well as erythrocyte tioguanine nucleotide levels, were performed regularly.

RESULTS

After 12 months of treatment, 14 of 16 (88%) patients were in remission, and 12 of these were completely free of systemic steroids. Adverse events during maintenance therapy included photosensitivity (one patient), minor viral infections (one), headache (four) and mild alopecia (one). One patient developed elevated liver enzymes, splenomegaly and thrombocytopenia, indicative of nodular regenerative hyperplasia of the liver.

CONCLUSIONS

In responders to tioguanine, the drug appears to be very effective in maintaining remission of chronic active Crohn's disease. Unfortunately, long-term hepatotoxicity seems to be an unpredictable and potentially severe adverse drug reaction. Therefore, to date, tioguanine cannot be recommended for general use outside clinical trials.

Activated clotting time or activated partial thromboplastin time as the method of choice for patients undergoing neuroradiological intervention

We evaluated the role of the activated clotting time (ACT) and activated partial thromboplastin time (APTT), both currently available as bedside tests, for monitoring anticoagulation following bolus injection of 2500 or 5000 IU heparin in 21 patients undergoing neuroradiological procedures. APTT was measured using the CoaguChek Pro device compared to the laboratory standard measurement and ACT comparing CoaguChek Pro to Hemochron Celite and Kaolin. Statistical analysis was performed using Bablok-Passing regression. Despite heparin doses of 2500-5000 IU APTT measurements were out of range in 67% of patients using CoaguChek Pro and in 76.5% of patients using the laboratory measurement. ACT was reliably determined in all patients. The correlation between the different devices (CoaguChek Pro vs. Hemochron Celite r=0.69, Kaolin r=0.78) and assays (Hemochron Celite/Kaolin r=0.85) was good. ACT ranged from 141-417 s measured by CoaguChek Pro and 138-320 s measured by Hemochron Celite and 172-381 s using Hemochron Kaolin. These results indicate that ACT is the method of choice for monitoring anticoagulation in neuroangiographic procedures.

Yaf2 inhibits Myc biological function

The proto-oncogenes of the myelocytomatosis viral oncogene homolog (MYC) family, including MYC, MYCN and MYCL, encode nuclear proteins that act as transcription factors. The Myc protein is the best studied member of this family and is involved in cell cycle regulation, differentiation and cell death. We have previously demonstrated that the zinc-finger protein Yaf2 interacts with the central region of MycN and enhances MycN dependent transcriptional activation. Here we show that Yaf2 also binds to the Myc protein in vivo and in vitro. In contrast to the activating effect on MycN function, Yaf2 inhibits Myc mediated transactivation and transformation. This differential influence on two members of the Myc family gives insight into a new mechanism to modulate the biological activities of Myc transcription factors.

6-thioguanine--efficacy and safety in chronic active Crohn's disease

BACKGROUND

: Azathioprine and mercaptopurine are commonly used in chronic active Crohn's disease. They share the disadvantage of a delayed onset of action and potentially serious side-effects, and are metabolized to thioguanine nucleotides which are thought to be the active metabolites. The direct use of 6-thioguanine may offer a more rapid and safer alternative. We conducted an open prospective study to investigate the efficacy and safety of 6-thioguanine in chronic active Crohn's disease.

METHODS

: Thirty-seven patients with chronic active Crohn's disease and a Crohn's disease activity index of > 150 were enrolled in this study. Inclusion criteria were steroid dependence (n = 19), steroid refractoriness (n = 9) and/or intolerance (n = 16) or refractoriness (n = 6) to azathioprine. Patients were treated with 40 mg/day of 6-thioguanine for 24 weeks; a dose escalation to 80 mg was allowed at week 12. Remission was defined as a Crohn's disease activity index of < 150 associated with a decrease of > 70 points; response was defined as a decrease of > 70 points in the Crohn's disease activity index.

RESULTS

: In the intention-to-treat analysis, 13 of 37 patients achieved remission (35%). Twelve of these 13 patients achieved remission after 4 weeks. Fifty-seven per cent of patients (21/37) achieved a response. The mean Crohn's disease activity index decreased from 284 +/- 74 to 153 +/- 101. 6-Thioguanine was more effective in azathioprine-intolerant than in azathioprine-refractory patients. Twelve of 16 patients intolerant to azathioprine tolerated 6-thioguanine. Adverse events included phototoxicity, pancreatitis, headache, nausea, alopecia, arthralgia, minor infections and reversible elevation of transaminases. Six patients required discontinuation of medication, two because of leucopenia.

CONCLUSIONS

: In this patient group with chronic active Crohn's disease, 6-thioguanine appeared to be effective with acceptable short-term toxicity, but long-term controlled trials are clearly needed to further define its role.

6-thioguanine--efficacy and safety in chronic active Crohn's disease

BACKGROUND

: Azathioprine and mercaptopurine are commonly used in chronic active Crohn's disease. They share the disadvantage of a delayed onset of action and potentially serious side-effects, and are metabolized to thioguanine nucleotides which are thought to be the active metabolites. The direct use of 6-thioguanine may offer a more rapid and safer alternative. We conducted an open prospective study to investigate the efficacy and safety of 6-thioguanine in chronic active Crohn's disease.

METHODS

: Thirty-seven patients with chronic active Crohn's disease and a Crohn's disease activity index of > 150 were enrolled in this study. Inclusion criteria were steroid dependence (n = 19), steroid refractoriness (n = 9) and/or intolerance (n = 16) or refractoriness (n = 6) to azathioprine. Patients were treated with 40 mg/day of 6-thioguanine for 24 weeks; a dose escalation to 80 mg was allowed at week 12. Remission was defined as a Crohn's disease activity index of < 150 associated with a decrease of > 70 points; response was defined as a decrease of > 70 points in the Crohn's disease activity index.

RESULTS

: In the intention-to-treat analysis, 13 of 37 patients achieved remission (35%). Twelve of these 13 patients achieved remission after 4 weeks. Fifty-seven per cent of patients (21/37) achieved a response. The mean Crohn's disease activity index decreased from 284 +/- 74 to 153 +/- 101. 6-Thioguanine was more effective in azathioprine-intolerant than in azathioprine-refractory patients. Twelve of 16 patients intolerant to azathioprine tolerated 6-thioguanine. Adverse events included phototoxicity, pancreatitis, headache, nausea, alopecia, arthralgia, minor infections and reversible elevation of transaminases. Six patients required discontinuation of medication, two because of leucopenia.

CONCLUSIONS

: In this patient group with chronic active Crohn's disease, 6-thioguanine appeared to be effective with acceptable short-term toxicity, but long-term controlled trials are clearly needed to further define its role.

Preferential integration of a transfected marker gene into spontaneously expressed fragile sites of a breast cancer cell line

Common fragile sites are non-randomly distributed unstable chromosomal regions thought to be hot spots for recombination. They appear as gaps, breaks and triradial figures when cells are cultured under conditions that inhibit replication or repair of DNA. The removal of replication-inhibitory challenges is followed by repair activation to restore the DNA damage at the fragile site. The breast cancer cell line MDA-MB-436 has a spontaneous and non-random expression pattern of fragile sites that appear to be related to the complex pattern of chromosomal rearrangements. The high frequency of which fragile sites are spontaneously activated should make MDA-MB-436 cells a powerful tool to study in greater detail the DNA sequences of a multiplicity of fragile sites. Here, we have explored if the DNA at spontaneously activated fragile sites in MDA-MB-436 cells can be genetically tagged by the repair-mediated insertion of an exogenously supplied drug resistance gene. The cells were transfected with pSV2Neo, stably transfected clones were selected with neomycin, and the sites of pSV2Neo integration were determined by fluorescent in situ hybridization. Eighty-eight of 100 isolated clones had a non-random distribution of a total of 112 pSV2Neo integrations. Of these, 95 integrations (85%) coincide with the position at which non-random gaps and breaks appear in the MDA-MB-436 cells. Forty-nine (44%) of the 112 integrations appeared to be at position of known fragile sites, 46 (41%) were at the non-random chromosomal sites not previously described as "true" fragile sites. It is possible, however, that these non-random instabilities signal of genomic regions equivalent to fragile sites, that either have not previously been detected due to low level expression or that are activated in a tissue- or cell-type-specific manner. Collectively, our results show a preferential integration of exogenous DNA into fragile sites and other non-random regions of high genomic instability in MDA-MB-436 cells. This approach has provided a platform for the efficient targeted cloning and characterization of a substantial number of both common fragile sites and other non-random instability regions possibly related to breast cancer, and possibly also to other types of cancer.

Ataxin-2 promotes apoptosis of human neuroblastoma cells

Neuroblastoma is a highly heterogeneous tumor of young children. Although many advances have been made towards understanding the molecular mechanisms dictating the phenotypic heterogeneity, the prognosis of children with neuroblastoma, particularly of progressively growing variants, has remained dire. About 10% of neuroblastomas regress spontaneously, probably by apoptosis, while another 20% have amplified the MYCN gene resulting in a poor prognosis. In pursuit of identifying cell death-associated genes in neuroblastoma, we encountered the SCA2 gene, coding for ataxin-2, as an important player. Here, we report that enforced expression of wild-type ataxin-2, but not of mutant ataxin-2, sensitizes neuroblastoma cells for apoptosis. In line with this, higher levels of ataxin-2 were detected in apoptotic cells compared to nonapoptotic cells. Neuroblastoma tumors with amplified MYCN contain significantly less ataxin-2 protein than tumors without amplified MYCN. Collectively, our data suggest that ataxin-2 has an important role in regulating the susceptibility of neuroblastoma cells to apoptotic stimuli in vitro and in vivo.

Safe treatment of thiopurine S-methyltransferase deficient Crohn's disease patients with azathioprine

Thiopurine S-methyltransferase (TPMT) deficient patients develop life threatening haematotoxicity (for example, pancytopenia) when treated with a standard dose of azathioprine (AZA) and 6-mercaptopurine (6-MP) due to excessive accumulation of cytotoxic metabolites. At present, it is generally recommended that these patients should not receive AZA or 6-MP treatment for inflammatory bowel disease. We report for the first time that Crohn's disease patients with TPMT deficiency can be successfully treated with AZA. We illustrate this with three cases where treatment has been successful and toxicity has been avoided by carefully titrating the drug dose. Thus very low TPMT activity demands pharmacogenetically guided dosing.

["Off-label" prescribing of drugs in the ambulatory care of children and adolescents]

BACKGROUND AND OBJECTIVE

Hospitalised children receive up to 90 % of their drug prescriptions without ("unlicensed use") or outside ("off-label use") the terms of their product license. As no data are available for pediatric outpatients in Germany, we determined "off-label" use in a representative cohort of children and adolescents.

PATIENTS AND METHODS

We analyzed 1.74 million prescriptions, written from January 1 st through March 31 st, 1999, to 455 661 children and adolescents aged 0 to 16 years by 6886 specialists in pediatric, general or internal medicine. All prescriptions were covered by the public health insurance, Allgemeine Ortskrankenkasse, (AOK) Baden-Wuerttemberg. License status of 1 592 006 identifiable prescriptions comprising more than 10 000 differently branded drugs was determined in 5 age groups and in different groups of the Anatomical Therapeutical Chemical Classification (ATC). As reference documents for licensing status we used the "Fachinformation" (summary of product characteristics), the "Rote" and "Gelbe" Liste, respectively.

RESULTS

13.2 %, i. e. 210 528 of the 1.59 million prescriptions, were "off-label". 75 % of these "off-label" prescriptions were due to a lack of information on pediatric use in the summary of product characteristics. The highest "off-label" fractions were found in drugs topically used in eyes and ears (78.6 %), dermatological (57.9 %), cardiovascular drugs (55.2 %), drugs für musculoskeletal (45.2 %) and urogenital disorders (48.5 %) and antidepressants (36.6 %).

CONCLUSION

"Off-label" prescribing in outpatient children is less frequent than in pediatric inpatients. Considering the high absolute number of prescriptions however, 13.2 % cannot be neglected. Doctors prescribing drugs for children and adolescents should be aware of their actual licensing status because of its medical and legal consequences.

Loss of a FYN-regulated differentiation and growth arrest pathway in advanced stage neuroblastoma

Tumor stage, age of patient, and amplification of MYCN predict disease outcome in neuroblastoma. To gain insight into the underlying molecular pathways, we have obtained expression profiles from 94 primary neuroblastoma specimens. Advanced tumor stages show a characteristic expression profile that includes downregulation of multiple genes involved in signal transduction through Fyn and the actin cytoskeleton. High expression of Fyn and high Fyn kinase activity are restricted to low-stage tumors. In culture, expression of active Fyn kinase induces differentiation and growth arrest of neuroblastoma cells. Expression of Fyn predicts long-term survival independently of MYCN amplification. Amplification of MYCN correlates with deregulation of a distinct set of genes, many of which are target genes of Myc. Our data demonstrate a causal role for Fyn kinase in the genesis of neuroblastoma.

Genetic parameters of neuroblastomas

Neuroblastoma is a malignant childhood tumor of migrating neuroectodermal cells derived from the neural crest and destined for the adrenal medulla and the sympathetic nervous system. The biological behavior of neuroblastomas is extremely variable and in some respects unique. Neuroblastomas tend to regress spontaneously in a portion of infants or to differentiate into a benign ganglioneuroma in some older patients. Unfortunately, in the majority of patients neuroblastoma is metastatic at the time of diagnosis, and it usually undergoes rapid progression with a fatal outcome. The mechanisms leading to this diverse clinical behavior of neuroblastomas are largely unclear. From the analysis of tumors at the cytogenetic and molecular level non-random genetic changes have been identified, including ploidy changes, amplification of the oncogene MYCN, deletions of chromosome 1p, gains of chromosome arm 17q, and deletions of 11q as well as of other genomic regions that allow tumors to be classified into subsets with distinct biological features and clinical behavior. MYCN status is widely accepted for therapy stratification. Additional genetic parameters are currently under investigation to refine risk assessment, but so far the molecular monitoring tools for prediction of therapy response and disease outcome are still incomplete. This should lead to more risk-adapted therapies according to the clinical-genetic parameters by which individual tumors are characterized. This review aims at discussing the role of genomic changes in neuroblastomas of diverse biological and clinical types.

Arginine-glycine-aspartic acid (RGD)-peptide binds to both tumor and tumor-endothelial cells in vivo

Targeting tumor cells or tumor vasculature by peptides is a promising strategy for delivering cytotoxic drugs for cancer therapy. The identification of efficient targeting peptides depends on the availability of informative methods for determining cellular binding specificities. Here, we have used fluorescence-activated cell-sorting (FACS) analysis in combination with an isopentane freezing method to show targeted binding of the Arg-Gly-Asp (RGD)-4C-peptide labeled with FITC, not only to endothelial cells but also to tumor cells in human breast cancer xenografts grown in nude mice. Nontumorous cells showed only background binding. This study suggests, that the RGD-4C-peptide can target tumor endothelial cells as well as tumor cells. Consequently, it should be possible to design a combination therapy approach against both targets.

Fluorescence in situ hybridization analyses of chromosome band 1p36 in neuroblastoma detect two classes of alterations

Chromosomal alterations in 1p36 were investigated in 196 neuroblastoma tumors using fluorescence in situ hybridization. Additionally, by using the same technique, it was determined whether MYCN was amplified in 149 of these. The most frequent finding was a deletion in 1p36, leading to monosomy of this region (29 cases, 15%). Furthermore, we found tumors with at least two intact copies of chromosome 1 and additional 1p36-deleted copies. Altogether, 21 tumors (11%) displayed this imbalance of 1p36. Similar to the cases with deletion, imbalances were predominantly found in stage 4 tumors (81%), and they were significantly associated with an increased patient age (P = 0.01). Nearly all 1p-deleted tumors showed amplification of MYCN (24/27 analyzed samples, 89%), whereas only 8 of 21 (38%) with imbalance did. Eight cases with imbalance were investigated for loss of heterozygosity (LOH) using microsatellite markers in 1p35-36. Only 4 displayed 1p36 LOH, whereas the remaining 4 were heterozygous. Both patients with deletion of 1p and with imbalance had a poor outcome [3-year rate of event-free-survival (EFS): 33 +/- 15% and 41 +/- 15%], which was significantly worse compared to the outcome of patients without 1p alterations (3-year EFS: 70 +/- 5%; P = 0.01 and P = 0.0059). We conclude that besides monosomic short arm deletions, imbalance of 1p36 is a strong marker of a poor prognosis in neuroblastoma and not necessarily associated with MYCN amplification and LOH.

Amplified MYCN in human neuroblastoma: paradigm for the translation of molecular genetics to clinical oncology

Increase in the dosage of cellular oncogenes by DNA amplification is a frequent genetic alteration of cancer cells. In neuroblastoma, amplification of the gene MYCN has been associated with aggressively growing cancers and is an indicator for poor prognosis. MYCN amplification is of predictive value in identifying patients with neuroblastoma who require specific therapeutic regimens and those who do not benefit from chemotherapy.

Pharmacokinetic considerations in the treatment of inflammatory bowel disease

This review describes the pharmacokinetics of the major drugs used for the treatment of inflammatory bowel disease. This information can be helpful for the selection of a particular agent and offers guidance for effective and well tolerated regimens. The corticosteroids have a short elimination half-life (t1/2beta) of 1.5 to 4 hours, but their biological half-lives are much longer (12 to 36 hours). Most are moderate or high clearance drugs that are hepatically eliminated, primarily by cytochrome P450 (CYP) 3A4-mediated metabolism. Prednisone and budesonide undergo presystemic elimination. Any disease state or comedication affecting CYP3A4 activity should be taken into account when prescribing corticosteroids. Depending on the preparation used, 10 to 50% of an oral or rectal dose of mesalazine is absorbed. Rapid acetylation in the intestinal wall and liver (t1/2beta 0.5 to 2 hours) and transport probably by P-glycoprotein affect mucosal concentrations of mesalazine, which apparently determine clinical response. Any clinical condition influencing the release and topical availability of mesalazine might modify its therapeutic potential. Metronidazole has high (approximately 90%) oral bioavailability, with hepatic elimination characterised by a t1/2beta of 6 to 10 hours and a total clearance of about 4 L/h/kg. Ciprofloxacin is largely excreted unchanged both renally (about 45% of dose) and extrarenally (25%), with a relatively short t1/2beta (3.5 to 7 hours). Thus, renal function affects the systemic availability of ciprofloxacin. Both mercaptopurine and its prodrug azathioprine are metabolised to active compounds (6-thioguanine nucleotides; 6-TGN) by hypoxanthine-guanine phosphoribosyltransferase and to inactive metabolites by the polymorphically expressed thiopurine S-methyltransferase (TPMT) and xanthine oxidase. Patients with low TPMT activity have a higher risk of developing haemopoietic toxicity. Both mercaptopurine and azathioprine have a short t1/2beta (1 to 2 hours), but the t1/2beta of 6-TGN ranges from 3 to 13 days. Therapeutic response seems to be related to 6-TGN concentration. Almost complete bioavailability has been observed after intramuscular and subcutaneous administration of methotrexate, which is predominantly (85%) excreted as unchanged drug with a t1/2beta of up to 50 hours. Thus, renal function is the major determinant for disposition of methotrexate. Cyclosporin is slowly and incompletely absorbed. It is extensively metabolised by CYP3A4/5 in the liver and intestine (median t1/2beta and clearance 7.9 hours and 0.46 L/h/kg, respectively), and inhibitors and inducers of CYP3A4 can modify response and toxicity. Infliximab is predominantly distributed to the vascular compartment and eliminated with a t1/2beta between 10 and 14 days. No accumulation was observed when it was administered at intervals of 4 or 8 weeks. Methotrexate may reduce the clearance of infliximab from serum.

The N-myc and c-myc downstream pathways include the chromosome 17q genes nm23-H1 and nm23-H2

Gain of chromosome 17q material is the most frequent genetic abnormality in neuroblastomas. The common region of gain is at least 375 cR large, which has precluded the identification of genes with a role in neuroblastoma pathogenesis. Neuroblastoma also frequently show amplification of the N-myc oncogene, which correlates closely with 17q gain. Both events are strong predictors of unfavorable prognosis. To identify genes that are part of the N-myc downstream pathway, we constructed SAGE libraries of an N-myc transfected and a control cell line. This identified the chromosome 17q genes nm23-H1 and nm23-H2 as being 6-10 times induced in the N-myc expressing cells. Northern and Western blot analysis confirmed this up-regulation. Time-course experiment shows that both genes are induced within 4 h after N-myc is switched on. Furthermore, we demonstrate also that c-myc can up-regulate nm23-H1 and nm23-H2 expression. Neuroblastoma tumor and cell line panels reveal a striking correlation between N-myc amplification and mRNA and protein expression of both nm23 genes. We show that the nm23 genes are located at the edge of the common region of chromosome 17q gain previously described in neuroblastoma cell lines. Our findings suggest that nm23-H1 and nm23-H2 expression is increased by 17q gain in neuroblastoma and can be further up-regulated by myc overexpression. These observations suggest a major role for nm23-H1 and nm23-H2 in tumorigenesis of unfavorable neuroblastomas.

[Evaluation of CHILI teleradiology network 4 years after clinical implementation]

The CHILI teleradiology network has more than 60 installations in Germany and the USA. Radiological images and cardiological multiframe series are exchanged in clinical routine. This article investigates in what way and how often the system is used. This is done by means of accounting files that are produced automatically by the system. User functions, transmission protocols, data quantity, frequencies and time of data transmission and teleconferences are evaluated and discussed in this paper. Different application scenarios have been identified and are described and analyzed as well. An important result is, that the system is not merely an emergency system. Instead, it is used in daily routine as a multifunctional, multimodality workstation with advanced features for teleradiology and telecardiology.

BRCA2: a genetic risk factor for breast cancer

The identification of the breast cancer susceptibility genes BRCA1 and BRCA2 a few years ago has been greeted with great excitement and has raised hopes that they might illuminate the common mechanisms of this disease. Today we have to recognize that these expectations remain unfulfilled. Mutations in BRCA1 and BRCA2 account only for a relatively small proportion of breast cancers, even within the group of familiar clusters, they seem to be virtually non-existing in sporadic breast cancers. A substantial proportion of familiar breast cancer clusters has failed to provide evidence for an association with mutations in either BRCA1 or BRCA2, thus we have to look forward to the identification of additional breast cancer susceptibility genes. What has been most disappointing is that the mutation status of BRCA1/2 can provide only limited information for cancer risk. Initial assessments had indicated a risk of close to 90% for mutation carriers to develop breast cancer until age 75 - a value that turned out to be restricted to high-risk families in which the BRCA1 and BRCA2 genes had been genomically mapped. In unselected clusters the risk appears much lower, some estimates suggest less than 40%. Both BRCA1 and BRCA2 large encode proteins that appear to have a plethora of functions, with a conspicuous association to DNA repair and DNA recombination, and probably transcription activation. Defects in DNA repair can result in cancer predisposition syndromes and are recognized as being instrumental in cancer progression. Central questions have remained unanswered: What is the function of damaged BRCA1 and BRCA2 genes in breast cancer risk? What is the basis of large variations of risk conferred to the patients by identical mutations? How can the predictive value of mutation surveys be increased?

Targeting the function of mature dendritic cells by human cytomegalovirus: a multilayered viral defense strategy

Human cytomegalovirus (HCMV) can suppress and evade the immune system. We have identified as a mechanism the ability of HCMV to infect dendritic cells (DC), which initiate the antiviral immune response. HCMV-infected DC show enhanced expression of costimulatory molecules. In contrast, MHC molecules are partially downregulated, leading to a reduced antigen-presenting capacity. Moreover, the apoptosis-inducing ligands CD95L (FasL) and tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL) are upregulated, thereby enabling HCMV-infected DC to delete activated T lymphocytes. This additional layer of viral defense is complemented by nondeletional mechanisms, which suppress surviving T cells. Thus, infection of DC allows the virus to blunt the antiviral T cell response by a multilayered defense strategy and could play a pivotal role in HCMV-triggered immunosuppression.