Individuals with abnormal phenotype and normal G-banding karyotype: improvement and limitations in the diagnosis by the use of 24-colour FISH

The simultaneous identification, by fluorescence in situ hybridisation (FISH), of each chromosome in a distinct colour became feasible a few years ago. The key question in the application of this and many other developments in molecular cytogenetics to clinical situations is whether the results add significant further information that is relevant to the diagnosis. So far, limited data exist regarding how much improvement the technique brings to the diagnosis of phenotypically abnormal individuals in whom no abnormalities have been detected by conventional G-banding analysis. Because of the lack of a conclusive diagnosis, genetic counselling, estimation of recurrence risk and prenatal diagnosis of these individuals and their relatives is problematic. We report a study with 24-colour whole-chromosome painting of 10 familial and 11 isolated cases with abnormal phenotypes and normal G-banding karyotypes. Previously undetected unbalanced translocations were revealed in two cases. The value and current cost-effectiveness of multicolour FISH for cytogenetic diagnosis is discussed.

Nasopharyngeal teratoma and mosaic tetrasomy 1q detected at amniocentesis. A case report and review of the literature

The occurrence of nasopharyngeal teratomas (NPT) is an infrequent event and prenatal detection of such tumors is even rarer. We present a case report and review of the literature (N = 78 cases), in which we describe the cytogenetic, DNA, and pathological findings of a fetus with a mature NPT which was detected prenatally by ultrasound investigation following complaints of severe polyhydramnios by the mother.

Genomic acute myeloid leukemia-associated inv(16)(p13q22) breakpoints are tightly clustered

The inv(16) and related t(16;16) are found in 10% of all cases with de novo acute myeloid leukemia. In these rearrangements the core binding factor beta (CBFB) gene on 16q22 is fused to the smooth muscle myosin heavy chain gene (MYH11) on 16p13. To gain insight into the mechanisms causing the inv(16) we have analysed 24 genomic CBFB-MYH11 breakpoints. All breakpoints in CBFB are located in a 15-Kb intron. More than 50% of the sequenced 6.2 Kb of this intron consists of human repetitive elements. Twenty-one of the 24 breakpoints in MYH11 are located in a 370-bp intron. The remaining three breakpoints in MYH11 are located more upstream. The localization of three breakpoints adjacent to a V(D)J recombinase signal sequence in MYH11 suggests a V(D)J recombinase-mediated rearrangement in these cases. V(D)J recombinase-associated characteristics (small nucleotide deletions and insertions of random nucleotides) were detected in six other cases. CBFB and MYH11 duplications were detected in four of six cases tested.

Prenatal diagnosis of trisomy 13 on fetal cells obtained from maternal blood after minor enrichment

In a pilot study to establish fetal nucleated red blood cell (NRBC) detection in maternal blood, trisomy 13 was diagnosed by FISH analysis at 11 weeks' gestation. The NRBCs were detected after a single-step ficoll density gradient enrichment. In blood samples taken both before and after CVS, 52 and 80 NRBCs, respectively, were found to be positive for fetal haemoglobin. In 47 per cent of these cells, FISH analysis for X and Y chromosomes confirmed the fetal sex. Moreover, 48 per cent of these NRBCs showed three fluorescent signals for a chromosome 13 probe, which confirmed the diagnosis of trisomy 13, previously detected at CVS karyotyping. This is the first report of non-invasive prenatal diagnosis of trisomy 13, i.e., pre-CVS, in the first trimester. The high number of fetal NRBCs detected indicates a connection with aneuploidy, probably due to early impairment of the feto-maternal barrier.

A near false-negative finding of mosaic trisomy 21--a cautionary tale

We report the finding of a mosaic trisomy 21 restricted to the long-term culture of chorionic villi and to one amniotic fluid culture which, if interpreted according to the standard rules for the authentication of mosaicism, would have resulted in a false-negative result. The definitive diagnosis of mosaic Down syndrome was eventually confirmed by cordocentesis and by post-abortion fibroblast cultures.

Development of a preparation and staining method for fetal erythroblasts in maternal blood: simultaneous immunocytochemical staining and FISH analysis

In order to detect fetal nucleated red blood cells (NRBCs) in maternal blood, a protocol was developed which aimed at producing a reliable staining method for combined immunocytochemical and FISH analysis. The technique had to be suitable for eventual automated screening of slides. Chorionic villi washings, cord blood, and maternal blood samples were used for this study. After a density gradient separation and centrifugal cytology, slides were stained either with 3,3-diaminobenzidin (DAB), a marker for heme, or with antibodies against the gamma-chain of fetal hemoglobin (HbF). FISH analysis for both X- and Y-chromosomes was performed on the same slides. Cytocentrifugation provided a controlled cell density on the slides with good cell morphology. Both the DAB and HbF staining were suitable for manual screening of large numbers of slides. The HbF staining, although supposed to be more specific for fetal NRBCs, appeared to be more sensitive to minor changes in preparation. We were eventually able to combine HbF staining with FISH analysis, and produced a detection efficiency of >85% for both X- and Y-chromosome signals. This preparation protocol simplifies the detection of NRBCs in maternal blood. Immunocytochemical staining and FISH analysis can be performed on the same cell with good image contrast, thus facilitating both manual and automated image analysis. This will facilitate the use of this approach for prenatal diagnosis.

Fetal cell detection in maternal blood: a study in 236 samples using erythroblast morphology, DAB and HbF staining, and FISH analysis

A protocol to detect fetal nucleated red blood cells (NRBCs) was tested in 217 pregnant women and in 19 nonpregnant controls. All the pregnant women were sampled after chorionic villus sampling (CVS); 20 were also sampled pre-CVS. NRBC recognition was based upon morphology by using staining of hemoglobin with 3,3-diaminobenzidin (DAB) or by immunocytochemical staining for fetal hemoglobin (HbF). This was combined with FISH analysis for both the X- and Y-chromosomes on the same cells. Progressive refinement of the methods increased the number of cases where NRBCs were detected from 53% (DAB) to 75% and 78% for DAB and HbF staining, respectively, with on average 43 NRBCs (range, 1-220). DAB gave a slightly higher yield than HbF in the lower cell count range (<25). In 6 out of 18 controls, NRBCs were detected with DAB, vs. 1 out of 19 (5%) with HbF. FISH analysis in 41 cases resulted in correct sex prediction in 80% (DAB) and 89% (HbF), respectively. Our data demonstrated an increase of cases with NRBCs (30% to 75%), as well as a rise of the mean number of NRBCs (6 to 29 cells), after CVS. We conclude that DAB staining is a straightforward way to screen for the presence of NRBCs in maternal blood, but is not specific for NRBCs of fetal origin. HbF immunophenotyping is a reliable marker for fetal NRBCs, which detected slightly fewer NRBCs than DAB-staining, but improved sex prediction and significantly reduced false-positive results. CVS at 10-13 weeks of gestation causes a significant increase of NRBCs in maternal blood. These data indicate that further refinement of NRBC detection is needed before application of noninvasive prenatal diagnosis using maternal blood is feasible.

Detection of CBP rearrangements in acute myelogenous leukemia with t(8;16)

The CREB-binding protein (CBP) is a large nuclear protein that regulates many signal transduction pathways and is involved in chromatin-mediated transcription. The translocation t(8;16)(p11;p13.3) consistently disrupts two genes: the CBP gene on chromosome band 16p13.3 and the MOZ gene on chromosome band 8p11. Although a fusion of these two genes as a result of the translocation is expected, attempts at detecting the fusion transcript by reverse transcriptase polymerase chain reaction (RT-PCR) have proven difficult; to date, only one in-frame CBP/MOZ fusion transcript has been reported. We therefore sought other reliable means of detecting CBP rearrangements. We applied fluorescence in situ hybridization (FISH) and Southern blot analyses to a series of AML patients with a t(8;16) and detected DNA rearrangements of both the CBP and the MOZ loci in all cases tested. All six cases examined for CBP rearrangements have breakpoints within a 13 kb breakpoint cluster region at the 5' end of the CBP gene. Additionally, we used a MOZ cDNA probe to construct a surrounding cosmid contig and detect DNA rearrangements in three t(8;16) cases, all of which display rearrangements within a 6 kb genomic fragment of the MOZ gene. We have thus developed a series of cosmid probes that consistently detect the disruption of the CBP gene in t(8;16) patients. These clones could potentially be used to screen other cancer-associated or congenital translocations involving chromosome band 16p13.3 as well.

A second case of hexasomy 8 in myelodysplastic syndrome

Tetrasomy 8 is a rare form of acquired aneuploidy found exclusively in the myeloid leukemias. Hexasomy 8 is even rarer: only one case has been reported, thus far. We describe here the second case of hexasomy 8 as the sole abnormality in an elderly female patient with myelodysplastic syndrome (MDS).

Pitt-Rogers-Danks syndrome and Wolf-Hirschhorn syndrome are caused by a deletion in the same region on chromosome 4p 16.3

Recently, a deletion of chromosome 4pter was found in three patients with Pitt-Rogers-Danks syndrome. We investigated two of these patients, by means of DNA and FISH studies, together with two additional patients with Pitt-Rogers-Danks syndrome, to determine the critical region of the deletion in these patients and to compare this with the critical region in Wolf-Hirschhorn syndrome. All four patients showed terminal deletions of chromosome 4p of different sizes. One of them appeared to have an unbalanced karyotype caused by a cryptic translocation t(4;8) in the mother, resulting in a deletion of chromosome 4pter and a duplication of chromosome 8pter. The localisation of the Wolf-Hirschhorn critical region has been confined to approximately 1 Mb between D4S43 and D4S115. Our study shows that the deletions in four patients with the Pitt-Rogers-Danks syndrome overlap the Wolf-Hirschhorn critical region and extend beyond this in both directions. This study, combined with the fact that our third patient, who was previously described as a Pitt-Rogers-Danks patient, but who now more closely resembles a Wolf-Hirschhorn patient, makes it likely that Pitt-Rogers-Danks and Wolf-Hirschhorn syndromes are different clinical phenotypes resulting from a deletion in the same microscopic region on chromosome 4p16.

Mosaicism of the 5q deletion as assessed by interphase FISH is a common phenomenon in MDS and restricted to myeloid cells

Interstitial deletion of chromosome 5q is a common cytogenetic abnormality observed in MDS. We have used fluorescence in situ hybridization (FISH) to determine accurately the percentage of cytogenetically abnormal peripheral blood cells. YAC and cosmid probes localized to chromosome 5q were hybridized to interphase nuclei from purified polymorphonuclear cells (PMNs) from six MDS patients with chromosome 5 deletions. Per patient, 25-67% of the cells exhibited one signal for the 5q31-q33 specific probes IL-4, D5S207 and c-fms. This percentage was constant for the various probes utilized for each patient. Hybridization of the same probes to PMNs from healthy individuals and hybridization of probes (D5S39 and D5S498) localized outside the deleted segments to PMNs of the patients, resulted in 90-95% nuclei with two signals. In addition, FACS-purified peripheral blood cells were investigated by FISH using the IL-4 cosmid. This demonstrated that the hybridization pattern in monocytes was similar to that observed in PMNs, whereas T-lymphocytes showed no loss of signals. These results indicate that a subfraction of the myeloid progenitor cells have acquired the 5q deletion.

Prenatal and postnatal investigation of a case with Miller-Dieker syndrome due to a familial cryptic translocation t(17;20) (p13.3;q13.3) detected by fluorescence in situ hybridization

We present here a case report of a fetus with a kidney anomaly and dilated occipital horns, detected initially by echoscopy at 29 weeks' amenorrhoea. After 31 weeks of gestation, the proband was born with clinical symptoms of Miller-Dieker syndrome. This was subsequently confirmed by fluorescence in situ hybridization (FISH), but not by conventional cytogenetic analysis. FISH using a cocktail of cosmids (c197-2, c197-4, c197-9) from the Miller-Dieker critical region showed a deletion of 17p13.3 in one homologue of chromosome 17. Additional FISH studies revealed a subtle 17p;20q translocation in the father, his sister, and the paternal grandmother. Hence, our patient is a carrier of an unbalanced 17;20 translocation resulting in a partial deletion of 17p and a partial trisomy 20q. Whenever kidney anomalies and dilated occipital horns are observed together with polyhydramnios during prenatal ultrasound examination, the possibility of Miller-Dieker syndrome should be suspected. In such cases, prenatal and/or postnatal chromosome studies should also include FISH analysis with the appropriate probes.

Simple method for detection of MYH11 DNA rearrangements in patients with inv(16)(p13q22) and acute myeloid leukemia

The pericentric inversion on chromosome 16 [inv(16)(p13q22)] and related t(16;16)(p13;q22) are recurrent aberrations associated with acute myeloid leukemia (AML) M4 Eo. Both abberations result in a fusion of the core binding factor beta (CBFB) and smooth muscle myosin heavy chain gene (MYH11). A selected genomic 6.9-kb BamHl probe detects MYH11 DNA rearrangements in 18 of 19 inv(16)/t(16;16) patients tested using HindIII digested DNA. The rearranged fragments were not detectable after remission in two cases tested, while they were present after relapse in one of these two cases tested.

A case of isodicentric 7p as sole abnormality in a patient with acute myeloid leukemia

The detection of isochromosomes in the leukemias and in solid tumors has been well described in the literature, the most common being the i(17q), which is found in the blast crisis of CML and terminal stages of acute myeloid leukemia. Reports of isochromosome 7 have, however, been less well represented, particularly isochromosomes of the short arm of chromosome 7, which represent approximately 1% of all reported isochromosomes in neoplasia. We present here a case report of an elderly female patient with AML-M2 who manifested an idic(7p) in the majority of her bone marrow cells. Fluorescence in situ hybridization (FISH) studies with both centromere-7--and chromosome-7--specific DNA probes verified the diagnosis of idic(7p). To the best of our knowledge, this is the first report of this type of leukemia with an acquired idic(7p) as the sole cytogenetic abnormality.

Molecular, cytogenetic, and phenotypic studies of a constitutional reciprocal translocation t(5;10)(q22;q25) responsible for familial adenomatous polyposis in a Dutch pedigree

Familial adenomatous polyposis (FAP) is an inherited predisposition to colorectal cancer caused by germline mutations in the adenomatous polyposis coli (APC) gene located on chromosome segment 5q21-q22. We detected a germline rearrangement of the APC gene in a Dutch FAP family by screening genomic DNA samples with APC cDNA probes. Subsequent molecular and cytogenetic studies revealed a constitutional reciprocal translocation t(5;10)(q22;q25) that resulted in the disruption of the APC gene. Southern blot and polymorphic marker analysis indicated that part of the APC gene had been deleted. Analysis of the APC protein product indicated that the translocation breakpoint did not lead to the formation of a detectable truncated APC protein but apparently resulted in a null allele. Evaluation of the clinical phenotypes in the patients suggested that they exhibited features of an unusual form of FAP characterized by a slightly delayed age of onset of colorectal cancer and a reduced number of colorectal polyps. The latter were mainly sessile and were located predominantly in the proximal colon. To our knowledge, this is the first description of FAP caused by a reciprocal translocation disrupting the APC gene.

RT-PCR diagnosis of patients with acute nonlymphocytic leukemia and inv(16)(p13q22) and identification of new alternative splicing in CBFB-MYH11 transcripts

As acute nonlymphocytic leukemia (ANLL) with inv(16) (p13q22) or t(16;16)(p13;q22) has been shown to result from the fusion of transcription factor subunit core binding factor (CBFB) to a myosin heavy chain (MYH11), we sought to design methods to detect this rearrangement using reverse transcriptase-polymerase chain reaction (RT-PCR). In all of 27 inv(16)(p13q22) and four t(16;16)(p13;q22) cases tested, a chimeric CBFB-MYH11 transcript coding for an in-frame fusion protein was detected. In a more extensive RT-PCR analysis with different primer pairs, we detected a second new chimeric CBFB-MYH11 transcript in 10 of 11 patients tested. The CBFB-MYH11 reading frame of the second transcript was maintained in one patient but not in the others. We show that the different CBFB-MYH11 transcripts in one patient arise from alternative splicing. Translation of the transcript in which the CBFB-MYH11 reading frame is not maintained leads to a slightly truncated CBFB protein.

Cerebellar and brainstem hypoplasia in a child with a partial monosomy for the short arm of chromosome 5 and partial trisomy for the short arm of chromosome 10

A child with hypoplasia of the cerebellum and brainstem in association with an unbalanced translocation, resulting in a partial deletion of the short arm of chromosome 5 and a partial trisomy of the short arm of chromosome 10, is described. A balanced translocation was present in his mother and maternal grandmother. A maternal uncle had died at the age of 4 years with the same clinical picture. After reviewing the literature, we conclude that the monosomy 5p is the most likely cause for this malformation. We suggest that the possible existence of chromosomal anomalies should always be considered in the differential diagnosis of hypoplasia of the cerebellum and/or brainstem.

Proliferation and cytogenetic analysis of hairy cell leukemia upon stimulation via the CD40 antigen

Using the CD40 system, in vitro proliferation of hairy cell leukemia (HCL) was examined in 43 patients. In this culture system, cells were stimulated by interleukin-4 (IL-4) and anti-CD40 monoclonal antibodies (MoAbs) that were added in soluble form or were cross-linked via their Fc part using Fc gamma RII-transfected mouse fibroblast cells. Proliferation was induced and confirmed by 3H-thymidine incorporation in 14 cases and by the presence of metaphases in 42 cases. 3H-thymidine incorporation showed a heterogeneous pattern: cross-linking of anti-CD40 gave the highest proliferation in 8 cases; in 11 cases, stimulation with anti-CD40 MoAbs alone, without cross-linking also resulted in proliferation; the addition of IL-4 further enhanced 3H-thymidine incorporation in 5 cases, but suppressed this phenomenon in 5 other cases. The CD40 system proved to be very effective in obtaining cytogenetic data. With a success rate of 42 of 43 patients tested, we found clonal abnormalities in 8 cases (19%) and nonclonal abnormalities with involvement of one or two abnormal metaphases in another 7 cases. The chromosomes most frequently involved in the abnormal karyotypes, both structurally and numerically, were chromosomes 5, 7, and 14. By fluorescence-activated cell-sorting analysis of the cultured cells, and by immunophenotypic analysis of metaphase spreads, T-cell growth could be excluded and the HCL-lineage confirmed. Stimulation via the CD40 antigen is an excellent tool for growing hairy cell leukemia cells.

Somatic pairing of centromeres and short arms of chromosome 15 in the hematopoietic and lymphoid system

Normal human bone marrow and peripheral blood leukocytes as well as malignant cells from a variety of leukemias and lymphomas, demonstrate somatic pairing of centromeres and p arms of chromosome 15 during interphase. This phenomenon, effected by sequences on the p arm and requiring the intranuclear transport of spatial domains for at least one of the homologs, was not seen in amniotic fluid cells, uterine cervical tissue or in tissue fibroblasts. These studies contribute to the recent evidence of somatic pairing of homologous chromosomes in man and provide support for mobile chromosomal domains in interphase. It appears that sequences on the p arm of chromosome 15, possibly the nucleolar organizing genes, are uniquely important in the maturation of benign and malignant cells of hemato-lymphopoietic origin.

A gene for a myosin peptide is disrupted by the inv(16)(p13q22) in acute nonlymphocytic leukemia M4Eo

Chromosome 16 aberrations are well known in acute nonlymphocytic leukemia (ANLL). The most frequent chromosome 16 aberration in ANLL subtype M4Eo is the inv(16)(p13q22). Recently, we showed that in 5 inv(16) patients with ANLL M4Eo the short arm breakpoints are clustered within a 14-kb genomic EcoRI fragment. We report here the identification of a gene situated in the 14-kb fragment. The gene, which codes for a myosin peptide, is disrupted by the inversion of chromosome 16 in the 5 patients. To the best of our knowledge, this is the first report of a myosin gene disrupted in leukemia.

Detection of monosomy 7 and trisomy 8 in myeloid neoplasia: a comparison of banding and fluorescence in situ hybridization

Fluorescence in situ hybridization (FISH) is a powerful tool for detection of numerical and structural chromosomal aberrations. We have compared conventional banding techniques and FISH for the detection of monosomy 7 (-7) and trisomy 8 (+8) in 89 patients with myeloid malignancies. Of these patients, 21 had -7, 30 had +8, four had both, and 34 had no aberrations or aberrations other than -7 or +8 as assessed by banding techniques. Sequential samples were available in 23 patients. Alphoid DNA probes specific for chromosomes no. 7 and 8 were used for FISH. As controls, 10 normal bone marrow (BM) samples were hybridized with the chromosomes no. 7 and 8 probes, and in addition all tumor samples were hybridized with a chromosome no. 1 specific probe. The cut-off value for -7 was 18% one-spot cells, and for +8 was 3% three-spot cells. FISH analysis of 44 samples with -7 or +8, and at least 10 metaphases evaluated, showed that the proportions of aberrant metaphase cells mirrored the interphase clone sizes. Most samples with nonclonal metaphase aberrations, including those with only a few metaphases, had increased numbers of aberrant interphase cells: 20% to 80% for -7, and 3% to 43% for +8. Interphase cytogenetics of the 34 samples without -7 or +8 did not show significant cell populations with -7 or +8. In four patients, -7 or +8 could not be confirmed by FISH due to additional structural aberrations, marker chromosomes, or wrongly interpreted banding results. As FISH will be used more and more in cytogenetic diagnosis, clinical follow-up, and therapy monitoring, it will be necessary to standardize FISH procedures and supplement the Standing Committee on Human Cytogenetic Nomenclature (ISCN) definitions of a clone with criteria specifically for in situ hybridization.

46,XY del(18)(q21.3q22.2) with mosaicism of r(18) and a milder form of the 18q- syndrome

A mosaic karyotype: 46,XY,del(18)(q21.3q22.2)/47,XY,del(18) (q21.3q22.2)+ marker, was found in a mentally retarded male with a mild form of the 18q- syndrome and aplasia of the right thumb. By fluorescent in situ hybridisation, the marker chromosome could be identified as a ring chromosome no. 18.

Rubinstein-Taybi syndrome caused by submicroscopic deletions within 16p13.3

The Rubinstein-Taybi syndrome (RTS) is a well-defined complex of congenital malformations characterized by facial abnormalities, broad thumbs and big toes, and mental retardation. The breakpoint of two distinct reciprocal translocations occurring in patients with a clinical diagnosis of RTS was located to the same interval on chromosome 16, between the cosmids N2 and RT1, in band 16p13.3. By using two-color fluorescence in situ hybridization, the signal from RT1 was found to be missing from one chromosome 16 in 6 of 24 patients with RTS. The parents of five of these patients did not show a deletion of RT1, indicating a de novo rearrangement. RTS is caused by submicroscopic interstitial deletions within 16p13.3 in approximately 25% of the patients. The detection of microdeletions will allow the objective conformation of the clinical diagnosis in new patients and provides an excellent tool for the isolation of the gene causally related to the syndrome.

t(5;12)(q31;p12). A clinical entity with features of both myeloid leukemia and chronic myelomonocytic leukemia

We report two patients with a myeloproliferative disorder (Philadelphia chromosome-negative chronic myeloid leukemia) and t(5;12)(q31;p12). Until now, only three cases of a translocation (5;12)(q31;p12) have been reported. All investigators had problems classifying their patient's disease into one of the well-defined entities of either MPD or myelodysplastic disorders. We postulate that this translocation may represent a subgroup of patients with features of both chronic myeloid leukemia and chronic myelomonocytic leukemia (CMMoL).

Effect of mast cell growth factor (c-kit ligand) on clonogenic leukemic precursor cells

Mast cell growth factor (MGF), the ligand for the c-kit receptor, has been shown to be a hematopoietic growth factor that preferentially stimulates the proliferation of immature hematopoietic progenitor cells (HPC). We studied the effect of MGF on the in vitro growth of clonogenic leukemic precursor cells in the presence or absence of interleukin-3 (IL-3), granulocyte-macrophage colony-stimulating factor (GM-CSF), and/or erythropoietin (EPO). Leukemic blood and bone marrow cells from patients with various types of acute myeloid leukemia (AML), chronic myeloid leukemia (CML) in chronic phase, as well as bone marrow samples from patients with myelodysplastic syndromes (MDS) were studied. MGF as a single factor did not induce significant colony formation by clonogenic leukemic precursor cells. In the presence of IL-3 and/or GM-CSF, MGF weakly stimulated the colony formation by clonogenic precursor cells from patients with AML. In contrast, in the presence of IL-3 and/or GM-CSF, MGF strongly induced both size and number of leukemic colonies from patients with CML in chronic phase. Furthermore, in the presence of EPO, MGF strongly stimulated erythroid colony formation by CML precursor cells. Cytogenetic analysis of the colonies showed that all metaphases after 1 week of culture were derived from the leukemic clone. In patients with MDS, MGF strongly stimulated myeloid colony formation in the presence of IL-3 and/or GM-CSF (up to fourfold), and erythroid colony formation in the presence of EPO (up to eightfold). Not only the number, but also the size of the colonies increased. In the presence of MGF, the percentage of normal metaphases increased in three patients tested after 1 week of culture compared with the initial suspension, suggesting that the normal HPC were preferentially stimulated compared with the preleukemic precursor cells. In the absence of exogenous EPO and in the presence of 10% human AB serum, MGF in the presence of IL-3 and/or GM-CSF induced erythroid colony formation from normal bone marrow and patients with MDS or CML, illustrating that MGF greatly diminished the EPO requirement for erythroid differentiation. These results indicate that MGF may be a candidate as a hematopoietic growth factor to stimulate normal hematopoiesis in patients with acute myeloid leukemia, or with myelodysplastic syndromes.

Combined immunophenotyping and DNA in situ hybridization to study lineage involvement in patients with myelodysplastic syndromes

Clonality of myeloid and lymphoid cell fractions obtained from peripheral blood (PB) or bone marrow (BM) of five patients with a myelodysplastic syndrome (MDS), was studied by combined immunophenotypic analysis and DNA in situ hybridization. This novel technique enables quantitative and direct analysis of cytogenetic alterations in nondividing cells of distinct cell lineages. Four patients with a trisomy 8 and one patient with a translocation (1;7) were studied. For cell lineage determination, antibodies specific for progenitor cells (CD34), myeloid cells (CD15), monocytes (63D3), T cells (CD3), and B cells (CD19,20,22) were used. In one patient with a trisomy 8, BM cells were available and the erythroid lineage could be studied. For detection of cytogenetic aberrations, we used chromosome-specific repetitive DNA probes. In three patients, all nonlymphoid cells carried the cytogenetic abnormality; in two patients, mosaicism within these lineages was suggested by the relative low numbers (35% to 55%) of aberrant cells. None of the T or B cells of the five patients carried the chromosomal aberrations. We conclude that combined immunophenotyping and in situ hybridization is a feasible technique to study lineage involvement. Our data suggest that the chromosomal aberrations studied in MDS are restricted to the myeloid lineages.

Extensive cross-homology between the long and the short arm of chromosome 16 may explain leukemic inversions and translocations

Specific rearrangements of chromosome 16 are well known in acute nonlymphocytic leukemia with abnormal eosinophils. While mapping cosmids relative to breakpoints in chromosome 16 in leukemic cells with fluorescence in situ hybridization (FISH), we have identified three areas of extensive cross-homology between 16p and 16q. Three cosmids among 99 tested showed two large signals on the short arm and one signal on the long arm of chromosome 16. A fourth cosmid showed mainly two signals on the short arm. With the 16p-specific cosmid we can demonstrate that the breakpoints of a pericentric inversion and a reciprocal (16;16) translocation, both of which are characteristic for acute leukemia, map to the most distal of two blocks on the short arm. We suggest that there may be at least two distinct repetitive elements specific for chromosome 16 interdigitated on 16p. The presence of a similar repeat in the short, as well as the long arm of the chromosome, may play a role in the origin of chromosome 16 rearrangements in acute leukemia.

Nonradioactive in situ hybridisation of the translocation t(1;7) in myeloid malignancies

Bone marrow cells of four patients with t(1;7) and myelodysplasia or acute myeloid leukemia were analyzed using nonradioactive in situ hydridisation. As probes, centromeric alphoid DNA sequences of chromosomes 1 and 7, a satellite DNA probe for 1q12, and chromosome-specific libraries of chromosomes 1 and 7 were used. The breakpoints of the t(1;7)(p11;p11) as determined by banding analysis could be studied more accurately, and the recently proposed designation t(1;7)(cen;cen) was confirmed in all four cases. Colocalization of alphoid DNA sequences of chromosomes 1 and 7 by double target in situ hybridisation was demonstrated in metaphase cells and also in interphase nuclei. The in situ hybridisation method described is applicable for the screening of peripheral blood cells or archival material.

Effect of subcutaneously administered human recombinant erythropoietin on erythropoiesis in patients with myelodysplasia

In a phase II study, 12 patients with a myelodysplastic syndrome (MDS) and anaemia (nine transfusion-dependent) were treated with recombinant human erythropoietin (rHuEpo) to assess the therapeutic effect on erythropoiesis and on transfusion requirement. Patients with a low risk of developing acute leukaemia were included, i.e. refractory anaemia (RA), RA with ringed sideroblasts (RARS) and RA with excess blasts (RAEB), providing the percentage of myeloblasts in the bone marrow did not exceed 10%. Recombinant HuEpo treatment was initiated at a dose of 50 units/kg body weight and administered subcutaneously three times weekly. At 3-week intervals the dose was increased with 50 units/kg per injection, until after 15 weeks a maximum dose of 250 units/kg three times weekly was reached. All patients completed the study. Recombinant HuEpo was well tolerated and no serious side effects were seen. There was no evidence of the emergence of a new malignant clone in response to rHuEpo as shown by sequential karyotyping. In none of the patients was an increase in haemoglobin level or a diminished red blood cell transfusion requirement seen. In four out of 10 evaluable sequential bone marrow smears, an increase in erythropoiesis was seen, suggesting stimulation of ineffective red cell production. One of these patients also showed a rise in reticulocyte count. The number of erythroid progenitor cells (BFU-E and CFU-E) in blood and bone marrow was not affected by rHuEpo treatment. Also no change in the number of myeloid progenitor cells (CFU-GM) in blood and bone marrow was noted. In conclusion, subcutaneous treatment with rHuEpo at dosages up to 250 units/kg body weight (three times weekly) fails to increase the haemoglobin level or to diminish the transfusion requirement in patients with MDS and anaemia. It is unclear whether higher doses of rHuEpo are effective or whether patients with less severe anaemia who are transfusion independent, have a higher likelihood of response.

Improved interpretation of complex chromosomal rearrangements by combined GTG banding and in situ suppression hybridization using chromosome-specific libraries and cosmid probes

Chromosome aberrations of a hypodiploid ovarian carcinoma cell line (modal chromosome number 38) having a complex karyotype were analyzed using biotinylated DNA library probes that specifically hybridize to chromosomes 3, 6, 7, 8, 11, 13, and 16 from telomere (pter) to telomere (qter). A series of cosmid probes localized to the short arm of chromosome 16 were used to further investigate one of the two aberrant chromosomes 16 present in this cell line. The competitive in situ suppression (CISS) hybridization of DNA-libraries was mostly performed subsequent to GTG-banding of the same metaphase cell in order to interpret the hybridization signals optimally. This combined approach made it possible to detect the origin of chromosomal material that could not be identified using GTG-banding. Furthermore, the in situ hybridization techniques appeared to be helpful in the characterization of complex translocations and for accurate breakpoint determination.

De novo acute B-cell leukemia with translocation t(14;18): an entity with a poor prognosis

Three cases of de novo acute B-cell lymphoblastic leukemia are presented, all with an unusual phenotype, involvement of translocation t(14;18) and additional chromosomal abnormalities, including translocation t(8;14) and deletion of chromosome 9. In contrast to normal FAB-L2 or FAB-L3 acute lymphoblastic leukemia (ALL), these leukemias did not express cytoplasmatic and membranous immunoglobulin. The combination of translocation t(14;18) and additional chromosomal events on the other chromosome 14 account for the lack of immunoglobulin expression. In one case a low grade follicular lymphoma was found next to a high grade Burkitt type ALL. The translocation t(14;18) takes place as a mistake in the VDJH joining in pre-B cells in the bone marrow. It is proposed that some cases of de novo ALL may arise as a blast crisis induced by genetic events, secondary to the primary t(14;18) translocation. This type of ALL seems to have a poor prognosis.

Two distinct loci on the short arm of chromosome 16 are involved in myeloid leukemia

We report a case of acute nonlymphocytic leukemia (ANLL) M5 with the characteristic t(8;16)(p11;p13). The breakpoint in the short arm was regionally localized using nonradioactive in situ hybridization with a series of cosmids of chromosome 16. The results show that a difference exists between the breakpoint in chromosome 16(p13) in this t(8;16) and the breakpoint involved in the short arm in the characteristic inversion 16 (p13;q22)) that occurs in ANLL M4eo. Two different loci appear to be involved in these chromosomal rearrangements.

A new non-Hodgkin's B-cell line (DoHH2) with a chromosomal translocation t(14;18)(q32;q21)

A spontaneously growing EBV-negative B-cell line (DoHH2) was established from the pleural fluid cells of a 60-year-old man with centroblastic/centrocytic non-Hodgkin's lymphoma, that had transformed into an immunoblastic lymphoma. The pleural fluid cells and the DoHH2 cells expressed IgG lambda, were reactive with CD10 and CD19 monoclonal antibodies, and showed by cytogenetic analysis 48,XY, +7, +del(12)(q24), t(14;18)(q32;q21). Southern blot analysis of mini-satellite DNA patterns, and of rearrangements of the immunoglobulin genes and bcl-2, confirmed that the cell line was derived from the patient's clonal lymphoma cells. Direct nucleotide sequence analysis on polymerase chain reaction (PCR) products of the t(14;18) junction revealed an identical sequence for the JH-bcl-2 junction at JH6 and in the major breakpoint region of bcl-2 in both the original tumor cells and the DoHH2 cell line. The cell line was valuable as a standard quantification control for PCR analysis of the t(14;18) breakpoint. Titration experiments demonstrated the detection of up to one tumor cell in 10(5) normal blood lymphocytes.

Detection of trisomy 8 in hematological disorders by in situ hybridization

An alphoid repetitive DNA (D8Z2) probe specific for the pericentromeric region of chromosome 8 was used to detect extra copies of chromosome 8 in bone marrow cells obtained from 10 patients with hematological disorders and five controls. Numerical aberrations of chromosome 8 were established by conventional banding techniques. Trisomy 8 was found in four patients with myelodysplastic syndrome (MDS) and three with acute myeloid leukemia (AML). Three additional patients with MDS exhibited an extra chromosome 8 in only one metaphase. In five of the seven trisomy cases, the presence of the trisomy 8 clone was confirmed by in situ hybridization (ISH). In one case of AML with trisomy 8, detected by GTG-banding, no significant numbers of cells containing three spots were found using the alphoid repetitive probe; however, hybridization with a chromosome 8-specific library revealed that the alleged extra chromosome 8 was a translocation chromosome containing only the long arm of chromosome 8. Due to a lack of material, it was not possible to achieve optimal ISH results on the trisomy 8 bone marrow cells of patient 7. In the three MDS patients with a single trisomy 8 metaphase, a slight, albeit significant, increase of trisomy 8 interphase cells was found with ISH. We conclude that this probe is useful for cytogenetic studies. Moreover, ISH, in general, is a powerful tool for precise classification of chromosomal aberrations and can also contribute significantly to the clinical evaluation of patients with hematological disorders.

Sequential development of peripheral T-cell lymphoma in the course of chronic myelogenous leukemia

A patient is described with chronic myelogenous leukemia (CML) and an unusual karyotype 46XY,t(Y;12) (q11;p12), whose clinical course was complicated by T-cell lymphoma 5 years later. At that time bone marrow cells showed an additional karyotypic abnormality 46XY,t(Y;12) (q11;p12) del(7) (pter-p21), which remained unchanged until blastic transformation of the CML 8 months later. The bone marrow biopsy specimen, which revealed the blastic transformation of the CML, also showed evidence for localization of T-cell lymphoma. This case, added to two previously reported cases of the concurrence of CML and T-cell lymphoma, suggests a relationship between the two diseases, which is discussed.

[Chimerism pattern following allogeneic bone marrow transplantation; a retrospective study of the connection with post-transplantation complications]

Allogeneic bone marrow transplantation is generally followed by disappearance of all host haematopoietic cells and replacement by donor cells, resulting in complete chimerism. In some cases, however, residual host cells can be detected after transplantation; this is called partial chimerism. We have analysed the chimerism pattern in 106 patients, by erythrocyte antigen typing, erythrocyte and leucocyte isoenzymes, immunoglobulin allotyping and karyotyping of bone marrow and blood. Recipients of a T cell-depleted marrow transplant exhibited partial chimerism significantly more often. In most cases this involved T lymphocytes, sometimes in combination with other cell populations. Persisting B lymphocytes of host origin were detected only in recipients of a T cell-depleted marrow graft. No relationship was found between chimerism pattern and GVHD, interstitial pneumonitis, relapse of the underlying disease or disease free survival.

Rapid detection of chromosome 16 inversion in acute nonlymphocytic leukemia, subtype M4: regional localization of the breakpoint in 16p

The pericentric inversion of chromosome 16 characteristic for acute nonlymphocytic leukemia, subtype M4, was detected in five patients by means of nonradioactive in situ hybridization of complete cosmids. First, five cosmids situated along the short arm of chromosome 16 were used to map the breakpoint of the inversion distal to the rare folate-sensitive fragile site FRA16A. Then, the use of two cosmids on either side of the breakpoint, combined with a probe specific for the centromeric region of chromosome 16, readily detected the inversion, even in poor metaphase spreads.

Detection of the Philadelphia chromosome in interphase nuclei

Double fluorescence in situ hybridization was used to detect Philadelphia (Ph) chromosomes in interphase nuclei and metaphases of patients with chronic myeloid leukemia. Application of cosmid probes for 3' ABL and 5' BCR sequences gave better results than libraries for chromosomes 9 and 22. The present approach may provide an alternative method for monitoring minimal residual disease in Ph+ CML patients.

Combined GTG-banding and nonradioactive in situ hybridization improves characterization of complex karyotypes

Nonradioactive in situ hybridization (ISH) using biotinylated centromere probes for chromosomes 1, 6, 7, 10, 16, 17, 18, and the X, respectively, was combined with GTG-banding to study cytogenetic changes in two different ovarian cancer cell lines. ISH was performed after GTG-banding on the same metaphase. The use of a low trypsin concentration (0.01%) in the banding procedure was essential for subsequent ISH. This combined approach allows the detection of subtle chromosomal rearrangements and appears to aid the identification of marker chromosomes.

der(1)t(1;9): a specific chromosome abnormality in polycythemia vera? Cytogenetic and in situ hybridization studies

Two patients with polycythemia vera and an extra der(1)t(1;9) chromosome are reported. In one patient this was found as the sole abnormality. The other patient originally presented with trisomy 9 but later developed an extra der(1) during the further course of the disease with disapperance of the extra chromosome 9. In situ hybridization studies on this latter patient proved that the centromere of chromosome 1 was involved in the formation of the derivative chromosome.

Y chromosome specific probes identify breakpoint in a 45,X/46,X,del(Y)(pter----q11.1:) karyotype of an infertile male

An infertile male patient with a 45,X peripheral blood karyotype and a 45,X/46,X,del(Y)(pter----q11.1:) mosaic skin fibroblast karyotype is described. Steroid sulphatase (STS) activity was normal. Recombinant DNA studies using Y chromosome specific probes suggest that almost the entire long arm of the Y chromosome is deleted.

[Prenatal fetal blood group determination using chorionic villi biopsy]

The presence or absence of Rhesus D, c and Kell antigens on foetal red blood cells was determined in the first trimester of pregnancy on erythrocytes obtained by chorionic villi sampling. Pregnancies in 15 severely sensitized women (9 Rh D, 5 Kell and I Rh c) with a poor obstetric history and a partner heterozygous for the offending antigen were examined. A conclusive diagnosis could be made in 13 of the 15 cases studied.

Translocation t(14;18) in B cell lymphomas as a cause for defective immunoglobulin production

Although follicle center cell (FCC) lymphomas represent mature B cells, a considerable percentage do not have detectable Ig production. We have used Southern blotting and the polymerase chain reaction (PCR) to study the involvement of translocations t(14;18) and t(8;14) in causing defective Ig production in 16 Ig- FCC-derived lymphomas and three Ig- B cell acute lymphoblastic leukemias. In 6 of 19 cases, a t(14;18) was present with the other allele either deleted or in germline. In two cases a t(14;18) and a t(8;14) affected both Ig alleles, as confirmed by karyotyping. In two other cases, rearrangement of both bcl-2 on chromosome 18 and c-myc on chromosome 8 were found as well. Although cytogenetic proof was not available, the latter was probably involved in t(8;14). Restriction map analysis of one more case showed rearrangement on the pseudo-JH3 gene on one allele and t(14;18) on the other. Thus, in 11 of 19 cases, defective Ig H chain production could be explained by the inactivation of both Ig H chain genes due to translocation of one allele, in combination with deletions or defective rearrangements of the other allele. In contrast, in 28 of 30 Ig+ lymphomas, one functional Ig H chain allele was found, either in, or not in, combination with t(14;18). In two cases a single rearranged Ig H chain allele was found in combination with rearrangement of bcl-2. No comigration of the single Ig rearrangement with bcl-2, however, was found both by Southern blotting and PCR, suggesting a variant bcl-2 translocation, which leaves the Ig H chain allele functionally intact.