Hans-Christoph Duba

Evidence from a leukaemia model for maintenance of vascular endothelium by bone-marrow-derived endothelial cells

BACKGROUND Vascular endothelial cells lost from the blood-vessel endothelium through necrosis or apoptosis must be replaced. We investigated in a leukaemia model whether bone-marrow-derived endothelial cells contribute to this maintenance angiogenesis. METHODS We studied six patients with chronic myelogenous leukaemia (CML) carrying the BCR/ABL fusion gene in their bone-marrow-derived cells. We screened endothelial cells generated in vitro from bone-marrow-derived progenitor cells and vascular endothelium in myocardial tissue for the BCR/ABL fusion gene by in-situ hybridisation. For detection of donor-type endothelial cells after transplantation of haemopoietic stem cells, recipient tissue was stained with monoclonal antibodies against donor-type HLA antigens. FINDINGS We identified the BCR/ABL fusion gene in variable proportions (0-56%) of endothelial cells generated in vitro. Endothelial cells expressing the fusion gene were found in the vascular endothelium of a patient. In a recipient of an allogeneic stem-cell transplant, normal donor-type endothelial cells were detected in the vascular endothelium. INTERPRETATION These findings suggest that CML is not solely a haematological disease but originates from a bone-marrow-derived haemangioblastic precursor cell that can give rise to both blood cells and endothelial cells. Moreover, normal bone-marrow-derived endothelial cells can contribute to the maintenance of the blood vascular endothelium. The integration of bone-marrow-derived endothelial cells into the vascular endothelium provides a rationale for developing vascular targeting strategies in vasculopathies, inflammatory diseases, and cancer.

Fluorescence In Situ Hybridization (FISH) on Peripheral Blood Smears for Monitoring Philadelphia Chromosome-Positive Chronic Myeloid Leukemia (CML) During Interferon Treatment: A New Strategy for Remission Assessment

Interferon‐α (IFN‐α) alone or in combination with cytostatic drugs can induce major and durable cytogenetic responses in about 20 to 25% of chronic myeloid leukemia (CML) patients. Since these patients have a significant survival benefit, more frequent follow‐up investigations have become clinically important but require bone marrow (BM) aspirates. The aim of our study was to evaluate interphase fluorescence in situ hybridization (IPF) on peripheral blood (PB) smears as a rapid and reliable method to quantify Ph‐positive myeloid cells. IPF analysis was performed on 49 PB samples from 36 patients in the chronic phase of CML and at different stages of cytogenetic remission. IPF results of 30 PB samples were compared with those from BM aspirates simultaneously obtained from the same patients to evaluate the correlation of Ph‐positive cells. Further, the hypermetaphase FISH (HMF) technique was performed on cultured BM preparations of 31 patients for comparison with IPF results on PB. An excellent correlation was observed between the IPF results obtained on PB and BM samples (r = 0.98, y = x − 0.6, p < 0.0001). The mean difference between HMF from BM, on the one hand, and IPF from PB, on the other hand, was 3.2% (SD = ± 8.4%). Seventy percent of samples were identically classified in one of the four subgroups of cytogenetic response. Thirty percent were classified in neighbouring response groups. We conclude that FISH performed on PB is a rapid and reliable method for assessing the cytogenetic response of CML patients on IFN‐α based therapies, allowing more frequent and less invasive follow‐up investigations although it is not able entirely to replace routine analysis of BM. Genes Chromosomes Cancer 21:90–100, 1998.

An excess of chromosome 1 breakpoints in male infertility.

In a search for potential infertility loci, which might be revealed by clustering of chromosomal breakpoints, we compiled 464 infertile males with a balanced rearrangement from Mendelian Cytogenetics Network database (MCNdb) and compared their karyotypes with those of a Danish nation-wide cohort. We excluded Robertsonian translocations, rearrangements involving sex chromosomes and common variants. We identified 10 autosomal bands, five of which were on chromosome 1, with a large excess of breakpoints in the infertility group. Some of these could potentially harbour a male-specific infertility locus. However, a general excess of breakpoints almost everywhere on chromosome 1 was observed among the infertile males: 26.5 versus 14.5% in the cohort. This excess was observed both for translocation and inversion carriers, especially pericentric inversions, both for published and unpublished cases, and was significantly associated with azoospermia. The largest number of breakpoints was reported in 1q21; FISH mapping of four of these breakpoints revealed that they did not involve the same region at the molecular level. We suggest that chromosome 1 harbours a critical domain whose integrity is essential for male fertility.

Combination of Cytology, Fluorescence In Situ Hybridization for Aneuploidy, and Reverse-Transcriptase Polymerase Chain Reaction for Human Mammaglobin/Mammaglobin B Expression Improves Diagnosis of Malignant Effusions

PURPOSE The identification of malignant cells in effusions by conventional cytology is hampered by its limited sensitivity. The aim of this study was to improve tumor cell detection in effusions by molecular approaches. MATERIALS AND METHODS A total of 157 effusions from patients with tumors and 72 effusions from patients without a history or evidence of malignancy were included in this study. All effusion specimens were evaluated in parallel by cytology, fluorescence in situ hybridization (FISH) for aneuploidy, and reverse-transcriptase polymerase chain reaction (RT-PCR) for expression of human mammaglobin (hMAM) and mammaglobin B (hMAM-B). RESULTS In effusions from patients with tumors, the sensitivities of tumor cell detection by cytology, FISH, and hMAM and hMAM-B detection were 46.2%, 53.3%, 36.4%, and 57.7%, respectively. The corresponding specificities were 94.4%, 97.0%, 87.1%, and 88.6%. Notably, a high percentage of effusions containing malignant cells were in fact transudates, indicating the necessity for molecular diagnostic work-up of transudates collected from patients with tumors. Dependent on the tumor type, the use of appropriate marker combinations improved tumor cell detection in effusions significantly. By combining all four diagnostic tests, a positive test result indicating the presence of malignancy was achieved in 81.1%, with a fairly good specificity of 70.1%. CONCLUSION Molecular techniques are definitely useful to detect malignancy in cytologically negative effusions. Tumor cell detection in effusions can be significantly improved by FISH and PCR techniques applying appropriate molecular markers. This finding should help to improve tumor staging, prognostic assessment, and treatment monitoring.

Comparative genomic hybridization reveals a partial de novo trisomy 6q23-qter in an infant with congenital malformations: delineation of the phenotype.

Abstract We report the use of comparative genomic hybridization (CGH) to define the origin of a small extra segment (unidentifiable by classical cytogenetics) present in a de novo add(13)q34 chromosome that we found in the karyotype of a newly born boy with congenital heart defects, brain anomalies and dysmorphic signs. Initial investigation with fluorescence in situ hybridization (FISH) and a chromosome-13-specific library revealed that the excess material was not derived from chromosome 13. To uncover the origin of the unknown chromosome material, CGH was carried out on DNA isolated from blood lymphocytes of the patient. By using a conventional fluorescence microscope with no digital imaging devices, a single distinct region with gain of fluorescent intensity was observed on distal chromosome 6q. Confirmation of this finding by FISH with a chromosome-6-specific paint and a subtelomeric yeast artificial chromosome clone from 6q26-q27, in combination with the band morphology of the small extra chromosomal segment, allowed us to diagnose the additional material as being derived from chromosome 6q23-qter. FISH with a telomere 13q probe detected a terminal deletion of 13q34-qter on the derivative chromosome 13, indicating that the der(13) was a result of a translocation event. Genotyping of the hypervariable apolipoprotein (a) gene, which lies within 6q26-q27, showed that the additional chromosome 6 material was inherited from the mother. The karyotype of the proposita is therefore: 46,XY,-13,+der(13)t(6;13)(q23;q34) de novo (mat). Our results confirm the usefulness of CGH as an attractive alternative method for the characterization of constitutional small genetic imbalances and contribute to the delineation of the trisomy 6q23-qter phenotype.

The elastin gene is disrupted in a family with a balanced translocation t(7;16)(q11.23;q13) associated with a variable expression of the Williams-Beuren syndrome

The Williams-Beuren syndrome (WBS) is a complex developmental disorder with multisystemic manifestations including supravalvular aortic stenosis (SVAS), a so-called elfin face, a hoarse voice, and a specific cognitive phenotype. Most WBS patients have a >1 Mb deletion on one of their chromosomes 7 in q11 but except for elastin, whose haploinsufficiency causes the cardiovascular malformations, it is unknown which genes in the deletion area contribute to the phenotype. We have investigated a family with a cytogenetically balanced translocation t(7;16)(q11.23;q13) in which affected individuals manifested a broad spectrum of clinical phenotypes ranging from a hoarse voice as the only feature to the full WBS phenotype. Molecular cytogenetic and DNA sequence analyses of the translocation breakpoint showed that the cytogenetic rearrangement disrupts the elastin gene locus within intron 5 in the exact same manner in all translocation carriers. The recently described large inversion of the 7q11.23 region was not present in this family. Our data demonstrate that disruption of the elastin gene by a translocation breakpoint may cause classical WBS, atypical WBS, SVAS, or no recognisable phenotype, and provide a clear example for extensive phenotypic variability associated with a position effect in humans.

Cytogenetic Characterization of 22 Human Renal Cell Tumors in Relation to a Histopathological Classification

In this study, cytogenetic and fluorescence in situ hybridization analyses were performed on 22 sporadic, unilateral primary renal cell tumors. The tumors were classified according to cell types, growth patterns, and grades of malignancy. A feeder layer technique was used for the cell culture of 13 clear-cell carcinomas, 4 chromophilic carcinomas, 3 chromophobe carcinomas, 1 oncocytoma, and 1 spindle-shaped pleomorphic carcinoma. Eighty-six percent (19/22) of renal tumors showed clonal abnormalities. The most frequent finding in the 15 male patients was loss of chromosome Y (9/15). In 3/15, it was the only observed aberration. The second most visible aberration was regional loss or entire loss of chromosome 9, which was detected in 36% (8/22) of the cases. Four cases showed loss of chromosome 9 and 4 cases a deletion of the short arm with breakpoints on 9p11 and 9p21. Loss of 3p material was observed in 32% (7/22) of the cases but only in 2/13 patients with clear-cell carcinoma. Gain of chromosome 12 or 12p was observed in 27% (6/22). In 23% (5/22) of the patients, gain of whole or partial chromosomes 2, 5, and 7 was found. Less-frequent findings were loss of chromosomes 8, 14, and 21; gain of chromosome 16; and structural abnormalities of chromosome 1 (each 18%; 4/22). Only some of the karyotypes described as typical for the various renal tumor types were confirmed. In contrast with previous reports, chromosome 3 and 9 aberrations did not allow differentiation between tumor types in our study.

Nail patella syndrome in a cytogenetically balanced t(9;17)(q34.1;q25) carrier

Nail patella syndrome (NPS) is an autosomal dominant disorder characterized by dysplasia of the nails and patella, decreased mobility of the elbow, iliac horns and in some cases nephropathy. Linkage studies have localized the NPS locus to chromosome 9q34 within a 1–2 cM interval between D9S60 and the adenylate kinase gene (AK1), but the gene has remained elusive. We have identified a balanced t(9;17)(q34.1;q25) associated with NPS. By using FISH with probes from 9q the breakpoint region was narrowed to a 17.0 cM interval between D9S262 and ABL, which includes the NPS critical region. The patient showed the typical clinical features of NPS such as hypoplastic, deep-set nails, a dislocated elbow, iliac horns, and a polygonal patella. This suggests that the translocation has resulted from a break within or near the NPS gene, causing defective expression. The translocation in our patient may aid in the identification of the NPS gene.

Disruption of the methyltransferase-like 23 gene METTL23 causes mild autosomal recessive intellectual disability

We describe the characterization of a gene for mild nonsyndromic autosomal recessive intellectual disability (ID) in two unrelated families, one from Austria, the other from Pakistan. Genome-wide single nucleotide polymorphism microarray analysis enabled us to define a region of homozygosity by descent on chromosome 17q25. Whole-exome sequencing and analysis of this region in an affected individual from the Austrian family identified a 5 bp frameshifting deletion in the METTL23 gene. By means of Sanger sequencing of METTL23, a nonsense mutation was detected in a consanguineous ID family from Pakistan for which homozygosity-by-descent mapping had identified a region on 17q25. Both changes lead to truncation of the putative METTL23 protein, which disrupts the predicted catalytic domain and alters the cellular localization. 3D-modelling of the protein indicates that METTL23 is strongly predicted to function as an S-adenosyl-methionine (SAM)-dependent methyltransferase. Expression analysis of METTL23 indicated a strong association with heat shock proteins, which suggests that these may act as a putative substrate for methylation by METTL23. A number of methyltransferases have been described recently in association with ID. Disruption of METTL23 presented here supports the importance of methylation processes for intact neuronal function and brain development.

Improving tumor cell detection in pleural effusions by interphase cytogenetics.

In a recent review article on the diagnostic workup of pleural effusions, the usefulness of cytology and several other diagnostic approaches (e.g., the differentiation of exudates and transudates) was discussed (1). At this time, cytology is still the only diagnostic step accepted in the routine staging procedures of malignant disease according to the International Union Against Cancer/American Joint Committee on Cancer TNM-Classification (2). However, new, molecularbased methods to improve the diagnostic yield in effusions are encouraged (3). The introduction of new techniques complementing cytology is desirable since cytology is diagnostic for malignancy in about 50% of effusions from patients with known malignant disease, with a remarkable variation according to primary site of the neoplasm (reviewed in Table 1). This is explained by the regular presence of a reactive background with activated mesothelial cells in effusions, making a distinction from truly malignant cells difficult. One of many charcteristics of malignancy is aneuploidy, which is detectable by flow and image cytometry. Using these techniques, it was possible to reclassify a percentage of cytologically reactive effusions as being malignant (4,5). Another, rather laborious technique used to detect aneuploidy in effusions is cytogenetic evaluation by metaphase karyotyping (6). We were able to demonstrate that tumor cell detection in effusions is significantly improved when interphase cytogenetics by fluorescence in situ hybridisation (FISH) are performed simultaneously with conventional cytology (7). This is possible since: 1) malignancies are harbouring chromosomal changes in the vast majority of cases (8); and 2) primary tumors and their corresponding metastases usually are tightly related clonally, with identical or at least similar patterns of aberrations present (7). As reported previously in Clinical Cytometry (9), we were able to enhance the performance of FISH diagnostics in effusions by using dual-color FISH and establishing stringent criteria to identify tumor cells at low concentration. Here, we briefly present the results of FISH-diagnostics in 194 consecutive pleural effusions obtained from 166 patients with various malignancies (Table 2). This is an update, since parts of this entire series of pleural effusions were reported previously (7). The effusions were drawn for diagnostic or therapeutic reasons, and aliquots were subjected to routine cytologic and FISH evaluations. FISH-genotyping of effusions was approved by the local ethics committee. Using dual-color FISH evaluation, numerical ploidy status for several chromosomes (always including chromosomes 11 and 17) was determined and aneuploidy above cut-off was diagnostic for true malignancy (9). Cytology and FISH showed malignancy in 99 (51%) and 116 (59.8%) of the 194 pleural effusions, respectively (P 0.025; McNemar’s test). FISH was negative in 17 of the 99 cytologically malignant effusions (17.1%), whereas FISH was positive in 34 of the 95 cytologically negative effusions (35.8%). (Fig. 1) Combined evaluation by cytology and FISH identified tumor cells in 116 of the 194 pleural effusions (68.6%), which is significantly superior to cytologic evaluation only (51%, see above; P 0.0001, McNemar’s test). The contribution of FISH to improving tumor cell detection is highlighted in pleural effusions originating from patients with breast and bronchial carcinoma, where malignancy was detected by combination of cytology and FISH in 75.7% and 77.4% of effusions, respectively. This was significantly superior to cytologic evaluation only (diagnostic for malignancy in 59.5% and 54.8% of effusions, respectively; P 0.0001).