Structural alterations in chronic lymphocytic leukaemia. Cytogenetic and FISH analysis

In this study, we described cytogenetics and fluorescence in situ hybridization (FISH) analysis performed in chronic lymphocytic leukaemia (CLL) patients with structural alterations. Results were correlated with clinical characteristics. A total of 38 CLL patients: 16 cases with complex and 22 with simple karyotypes were studied. For comparison of clinical parameters, a control group of 78 CLL patients with normal karyotype and without FISH genomic alterations were also evaluated. We found 38 structural abnormalities not previously described in the literature, 28 (74%) of them were translocations. In cases with complex karyotypes, chromosomes 6, 8 and 13 were the most frequently involved in new alterations (nine each), followed by chromosomes 12, 14 and 15 (six each). Chromosome 8p was particularly involved in losses, being 8p21-pter the commonest region of overlap. Cases with simple karyotypes, showed del(6q) as the most frequent alteration (39%). Del(9)(q11) was recurrent in our series. Analysis of clinical parameters showed significant differences in white blood count (p = 0.005) and platelet count (p = 0.015) between patients with structural alterations and the control group. In addition, patients with structural alterations had a significantly shorter time to first treatment (TFT) (29 months) than the control group (69 months) (p = 0.037). Cases with complex karyotypes had a lower proportion of patients in Rai 0 clinical stage (15.4% vs 75%) (p = 0.005) and higher β2 microglobulin levels (3.3 vs 2.5 µg/mL) (p = 0.037) than those with simple karyotypes. Furthermore, a shorter TFT (13 months) and overall survival (56 months) in the complex karyotypes group compared with controls (69 and 144 months, respectively) (p = 0.015 and p = 0.005, respectively) were also found. Our results support the importance of cytogenetic analysis for clinical outcome in CLL and suggest that the diversity of genomic alterations is much greater than previously appreciated.

Induction of complete and incomplete chromosome aberrations by bleomycin in human lymphocytes

Bleomycin (BLM) is a clastogenic compound, which due to the overdispersion in the cell distribution of induced dicentrics has been compared to the effect of high-LET radiation. Recently, it has been described that in fibroblast derived cell lines BLM induces incomplete chromosome elements more efficiently than any type of ionizing radiation. The objective of the present study was to evaluate in human lymphocytes the induction of dicentrics and incomplete chromosome elements by BLM. Peripheral blood samples have been treated with different concentrations of BLM. Two cytogenetic techniques were applied, fluorescence plus Giemsa (FPG) and FISH using pan-centromeric and pan-telomeric probes. The observed frequency of dicentric equivalents increases linearly with the BLM concentration, and for all BLM concentrations the distribution of dicentric equivalents was overdispersed. In the FISH study the ratio between total incomplete elements and multicentrics was 0.27. The overdispersion in the dicentric cell distribution, and the linear BLM-concentration dependence of dicentrics can be compared to the effect of high-LET radiation, on the contrary the ratio of incomplete elements and multicentrics is similar to the one induced by low-LET radiation (~0.40). The elevated proportion of interstitial deletions in relation to total acentric fragments, higher than any type of ionizing radiation could be a characteristic signature of the clastogenic effect of BLM.

Biological dosimetry in a group of radiologists by the analysis of dicentrics and translocations

The results of a cytogenetic study carried out in a group of nine radiologists are presented. Chromosome aberrations were detected by fluorescence plus Giemsa staining and fluorescence in situ hybridization. Dose estimates were obtained by extrapolating the yield of dicentrics and translocations to their respective dose-effect curves. In seven individuals, the 95% confidence limits of the doses estimated by dicentrics did not include 0 Gy. The 99 dicentrics observed in 17,626 cells gave a collective estimated dose of 115 mGy (95% confidence limits 73-171). For translocations, five individuals had estimated doses that were clearly higher than the total accumulated recorded dose. The 82 total apparently simple translocations observed in 9722 cells gave a collective estimated dose of 275 mGy (132-496). The mean genomic frequencies (x100 +/- SE) of complete and total apparently simple translocations observed in the group of radiologists (1.91 +/- 0.30 and 2.67 +/- 0.34, respectively) were significantly higher than those observed in a matched control group (0.53 +/- 0.10 and 0.87 +/- 0.13, P < 0.01 in both cases) and in another occupationally exposed matched group (0.79 +/- 0.12 and 1.14 +/-0.14, P < 0.03 and P < 0.01, respectively). The discrepancies observed between the physically recorded doses and the biologically estimated doses indicate that the radiologists did not always wear their dosimeters or that the dosimeters were not always in the radiation field.

Genetic abnormalities associated with the t(12;21) and their impact in the outcome of 56 patients with B-precursor acute lymphoblastic leukemia

The ETV6/RUNX1 rearrangement is found in 20-30% of children with B-cell precursor acute lymphoblastic leukemia and is associated with a good outcome. To determine the cytogenetic and molecular abnormalities associated with the ETV6/RUNX1 rearrangement and the influence of this rearrangement in patients' evolution, we analyzed the molecular cytogenetic profiles of 56 children with this rearrangement and B-cell precursor acute lymphoblastic leukemia. Secondary changes detected with conventional cytogenetics and with fluorescence in situ hybridization were found in 71.4% of cases, the most frequent being the loss of the normal ETV6 allele, 12p aberrations, duplication of the fusion gene, and trisomy 21, as in replicating the results of previous studies. In this preliminary series, with a mean follow-up of 69.3 months, secondary abnormalities did not influence patients' outcome. It seems therefore that the prognostic value of the t(12;21) does not vary and that ETV6/RUNX1 rearrangement is an independent indicator of good prognosis.

Characterization of six marker chromosomes by comparative genomic hybridization

We applied comparative genomic hybridization (CGH) in six patients with de novo prenatal or postnatal extra marker chromosomes (MC). In four cases, MCs were mosaic and in one of them, the MC was detected in less than 50% of the cells. In three cases, CGH identified the origin of the extra MCs. In the other three, two prenatal cases and one child with an abnormal phenotype, CGH showed normal profiles. Among these cases, a normal profile and entirely C-band positive was identified suggesting that MC did not contain euchromatin. Genetic imbalances detected by CGH were as follow: a gain of 8p10-p12 in a boy with facial dysmorphism, hyperactivity and speech delay, a gain of 8q10-q12 in a healthy man with a history of spontaneous abortions, and a gain of 15q11-q13 in a girl with speech delay, and motor skill and object manipulation difficulties. Clinical data of these patients were compared with those reported in the literature. We conclude that CGH is a very useful and powerful tool for characterizing prenatal or postnatal MCs, even when the mosaicism is present and the MCs are present in less than 50% of the cells.

Analysis of Translocations in Stable Cells and their Implications in Retrospective Biological Dosimetry

The aim of the present study was to evaluate the influence of the exclusion of cells with unstable aberrations in the elaboration of dose-effect curves for translocations and their implications in biological dosimetry of past exposures. To establish dose-effect curves, peripheral blood samples were irradiated with 60Co gamma rays at ten different doses and the yield of translocations analyzed by FISH was considered in all cells and in stable cells (those without dicentrics, acentrics or rings). To discriminate transmissible translocations, the dose- effect curve for total apparently simple translocations in stable cells was chosen as the reference. In stable cells, dose- effect curves for apparently simple translocations without pseudosimple and complex-derived one-way patterns, tAbtBa and total translocations were obtained. None of these curves differed from the reference curve. When all cells were considered, only the curve for total translocations was significantly different from the reference curve. From the results obtained it can be concluded that the use of dose-effect curves for apparently simple translocations in stable cells and in all cells will give similar dose estimates in retrospective biological dosimetry studies. However, the use of dose-effect curves for total translocations in all cells will lead to underestimations of the dose mainly at high doses.

ETV6/RUNX1 rearrangement in childhood B-precursor acute lymphoblastic leukemia with normal karyotypes or without cytogenetic results

The ETV6/RUNX1 rearrangement (also known as TEL/AML1) was evaluated in 39 children with B-precursor acute lymphoblastic leukemia (ALL) who had a normal karyotype or lack of mitoses. Forty-one point six percent of patients with normal karyotypes and 66.6% of patients without mitoses presented with the ETV6/RUNX1 rearrangement. In addition to this rearrangement, eight patients showed loss of the normal ETV6 allele; of three patients without mitoses, two showed an extra signal of the RUNX1 gene and the third showed the fusion gene duplicated and loss of the normal ETV6 allele. One patient without the ETV6/RUNX1 rearrangement and without mitoses showed two extra signals of the RUNX1 gene.

Effect of DMSO on radiation-induced chromosome aberrations analysed by FISH

The purpose of the present work was to determine if the described reduction in the frequency of radiation-induced chromosome aberrations by DMSO is homogeneous within different human chromosomes. Blood samples were irradiated with 4 Gy of X-rays in absence and presence of 0.5 M DMSO. FISH painting was carried out independently for human chromosomes 1, 2, 3, 4, 7, 11 and 12. The observed frequencies of apparently simple translocations and dicentrics for all these chromosomes, showed a homogeneous reduction when the irradiation was done in the presence of DMSO. Moreover, a better fit between the observed and expected frequencies was obtained when (DNA content)2/3 was used to calculate the expected frequencies, instead of just the DNA content. This result supports the idea that for exchange type aberrations, a better adjustment is obtained when the surface area of spherical chromosome territories is considered.

Turner syndrome: Evaluation of prenatal diagnosis in 19 European registries

This study evaluated the prenatal diagnosis of Turner syndrome by ultrasound examination in an unselected population from all over Europe. Data from 19 congenital malformation registries from 11 European countries were analyzed. Turner syndrome was diagnosed in 125 cases (7.2%) in a total of 1,738 chromosome abnormalities. Sixty-seven percent of cases were detected prenatally by ultrasound examination due to the presence of congenital defects. The most frequent anomalies were cystic hygroma (59.5%) and hydrops fetalis (19%). The most frequent karyotype was 45,X (81.6%) followed by different types of mosaicism (16.8%). Significant differences in congenital defects (P = 0.0003) were observed between 45,X karyotypes and 45,X mosaicism cases. Prenatal counseling for 45,X mosaicism should take into account the expectation of a milder phenotype. In 78.6% of cases diagnosed by ultrasound examination due to congenital anomalies, the pregnancy was terminated. Prenatal detection of Turner syndrome by ultrasound examination was high in this unselected population.

AML1 amplification in a child with acute lymphoblastic leukemia

We report a case of de novo acute lymphoblastic leukemia with tandem amplification of the AML1 gene located in a chromosome marker that originated from chromosome 21 and a long event-free survival.

DNA hypermethylation at the D17S5 locus is not a frequent event in human urothelial cancer

OBJECTIVE

To analyse the DNA methylation status and the loss of heterozygosity (LOH) at the D17S5 locus (17p13.3) in urothelial cancer.

MATERIALS AND METHODS

DNA methylation was assayed and LOH analysed by Southern blotting in a series of 33 transitional cell carcinomas of the bladder and renal pelvis.

RESULTS

DNA hypermethylation and LOH at the D17S5 locus were detected in six (18%) and 17 (52%) of the tumours, respectively. The six cases with DNA hypermethylation were of the papillary type, and four also had LOH at this locus.

CONCLUSION

In contrast to other epithelial tumours, DNA hypermethylation at the D17S5 locus is not a frequent event in human urothelial cancer.

Suitability of FISH painting techniques for the detection of partial-body irradiations for biological dosimetry

Peripheral blood was irradiated with 2, 3, 4 or 5 Gy of X rays and was mixed with nonirradiated blood at five different dilutions to simulate partial-body irradiations. Analysis by FISH was performed using whole-chromosome painting probes for chromosomes 1, 4 and 11 in combination with a pancentromeric probe. Chromosome aberrations affecting the painted fraction were classified according to the PAINT nomenclature; other unstable aberrations affecting the unpainted material were also recorded. To evaluate the suitability of painting for dose assessment in partial-body irradiations, the ability of the u test and a proposed s test to detect the expected overdispersion and the similarity between the real doses and the doses estimated using Dolphin's approach were considered. For short-term biodosimetry, compared with solid-stained dicentric analyses, the suitability of FISH painting techniques for the detection of partial-body exposures is reduced, because of the decrease in the frequency of aberrations detected by FISH and in the number of cells with two or more aberrations. For reconstruction of past doses, when only complete apparently simple translocations in cells free of unstable aberrations were considered, the detection of the overdispersion and the accuracy of dose estimations were dramatically reduced. In a partial-body exposure, as the original dose increased, the whole-body dose estimated a long time after irradiation would tend to be lower, and the difference from the original dose would tend to be greater.

Genetic evolution in the metastatic progression of human pancreatic cancer studied by CGH

Metastases are thought to be derived from emerging clones within primary tumors. Although the concept of the clonal evolution of cancer is well defined, the genetic grounds and significance of this process in human cancer progression are still poorly understood. To gain insight into the genetic basis and clonal evolution underlying the metastatic progression of human pancreatic cancer in vivo, we analyzed by comparative genomic hybridization (CGH) chromosomal imbalances in seven metastases originated in nude mice and their three corresponding orthotopically xenografted human pancreatic tumors. All metastases were found to be closely related to the corresponding orthotopic implant, adding many additional changes to the already altered copy number profile of the pancreatic tumors. Recurrent metastasis-specific alterations included gains at 16cen-q22 and 17q21-qter. CGH results from paired specimens strongly suggest that the majority of additional genetic alterations present in metastases are likely to be present in subclones in the primary tumor.

Detection of chromosomal imbalances in papillary bladder tumors by comparative genomic hybridization

OBJECTIVES

To identify those genetic alterations that are associated with bladder cancer invasion and progression.

METHODS

A total of 30 specimens of transitional cell carcinoma of the bladder were analyzed by comparative genomic hybridization. The results were compared and summarized with previously reported studies.

RESULTS

The most frequent chromosome changes detected in our series of tumors were losses in 9q, 9p, 8p, and 11p and gains in 8q, 1q, 20q, and 11q. Three regions of deletion on chromosome 9 were delineated, at 9p21-p22, 9q13-q22, and 9q31-q34. Gains in 1q and losses on 11p were significantly more frequent in pT1G2 tumors than in superficial (pTa) ones. In our study, the most striking differences were seen between pT1G3 and pT1G2 tumors. Gains on 10p and 6p and losses at 5q, 6q, and 18q were significantly more frequent in the former.

CONCLUSIONS

A summary of our results and those available from published reports suggest that several groups of chromosomal imbalances may be associated with specific steps along bladder cancer progression. These genetic changes assume two different patterns: those that are shared, but are more intensive in one stage than in the other, and those such as a gain on 3p that are unique to invasive tumors.

Comparative genomic hybridization analysis of transitional cell carcinomas of the renal pelvis

We used comparative genomic hybridization to analyze 10 primary tumor samples from patients with transitional cell carcinoma of the renal pelvis. The most frequent loss was located at 9q, that is, in 50% of the tumors. Gains of DNA sequences were most frequently observed in chromosome regions 1q21 approximately q23, 2p23 approximately p25, 8q21.1 approximately q22 and in the whole chromosome 20. High level amplifications at 1q21 approximately q25, 6p22 approximately p23, 8q21 approximately q22, 8q22 approximately q24.1, 11q13, and 12q14 approximately q21 were detected. Most of these regions have previously been reported to be involved in transitional cell carcinoma of the bladder, thus confirming the importance of an increasing number of chromosome imbalances in the development and progression of this type of tumors.

Fetal and placenta chromosome constitution in 237 pregnancy losses

The aim of the study was to carry out cytogenetic analyses in pregnancy losses. Samples of cartilage and placenta tissue were obtained prospectively from 237 pregnancy losses of more than 16 weeks of gestation (130 stillbirths, 97 induced abortions and 10 early neonatal deaths). Cartilage culture was performed in 222 samples and placental culture was initiated in 224. The overall culture success rate was 83.5%, 72.3% in stillbirths, 97% in induced abortions and 100% in early neonatal death. An abnormal karyotype was detected in 52 cases: 6.9% in stillbirths, 43.6% in induced abortions and 20% in early neonatal deaths. The rate of discrepancy between the prenatal cytogenetic results in amniotic fluid and the post-termination karyotype was 3%. The tissue of choice for cytogenetic analysis was cartilage in induced abortions and early neonatal death, and placenta in stillbirth. The majority of cases had a chromosome abnormality: multiple congenital anomalies in 74.6%, and a single major anomaly in 9.7%.

Cytogenetic analyses by fluorescence in situ hybridization (FISH) in hospital workers occupationally exposed to low levels of ionizing radiation

An occupationally exposed population has been studied to evaluate the suitability of FISH painting techniques to detect chronic exposures to very low doses of ionizing radiation by the analysis of translocations. Whole-chromosome painting probes for chromosomes 1, 4 and 11 in combination with a pancentromeric probe have been employed. For comparison, a matched control population has also been studied. The mean genomic frequencies per 100 cells of total translocations in the control and exposed populations were 0.90 +/- 0.12 and 1.04 +/- 0.11, respectively. In the occupationally exposed population, no correlation between the frequencies of translocations and the doses received was found. When the two populations were compared, no significant differences were observed for the frequencies of the different chromosomal abnormalities examined. The absence of differences between control and exposed populations could be attributed to the very low-dose exposures recorded in the occupationally exposed population and to the wide range of individual frequencies of translocations observed.

Cytogenetic sensitivity of three Fanconi anemia heterozygotes to bleomycin and ionizing radiation

It is well known that Fanconi anemia (FA) patients show a hypersensitivity to the effect of cross-linking agents such as mitomycin C and diepoxybutane, while the sensitivity of these patients to ionizing radiation is controversial. Fanconi anemia heterozygotes do not show a hypersensitivity to the above-mentioned agents. However, bleomycin it is used to identify mutagen sensitive individuals, especially among head and neck cancer patients. We present here a preliminary study in which the mean frequencies of bleomycin-induced chromatid breaks (ctb) from three FA heterozygotes (X = 0.90, range 0.80-1.01) and 11 controls (X = 0.40, range 0.21-0.66) differ significantly (P<.001), indicating a high sensitivity to bleomycin of G(2) lymphocytes from these three FA heterozygotes. An increased sensitivity was not observed after exposure of G0 lymphocytes to 2 Gy of ionizing radiation.

Follow-up by cytogenetic and fluorescence in situ hybridization analysis of allogeneic bone marrow transplantation in two children with Fanconi's anaemia in transformation

Results of bone marrow transplantation (BMT) in patients with Fanconi's anaemia (FA) in transformation are very poor and only a few cases with favourable outcome have been reported. We present the follow-up of two FA-myelodysplastic syndrome (MDS) patients with monosomy 7 and complex karyotype implicating chromosome 1. Both relapsed with acute myeloid leukaemia (AML) following an allogeneic BMT from an HLA-identical brother. The patients showed clonal cytogenetic evolution coinciding with the leukaemic transformation. In one patient, fluorescence in situ hybridization using X and Y chromosome probes detected an increase of host cells before clinical relapse. Both patients received a successful second allogeneic BMT from the same donor using a more intensive treatment regimen and remain in clinical and cytogenetic remission more than 3 years later.

DNA copy number changes and evaluation of MYC, IGF1R, and FES amplification in xenografts of pancreatic adenocarcinoma

We analyzed eight samples of xenografted human pancreatic tumors and two metastases developed in mice by comparative genomic hybridization (CGH). The most recurrent changes were: gains on chromosomes 8 (8q24-qter; 7/8 cases), 15 (15q25-q26; 6/8 cases), 16 (16p in 6/8 cases; 16q in 5/8 cases), 20 (20q; 6/8 cases), and 19 (19q; 5/8 cases); and losses on chromosomes 18 (18q21; 6/8 cases), 6 (6q16-q21 and 6q24-qter; 5/8 cases each), and 9 (9p23-pter; 5/8 cases). The two metastases maintained the aberrations of the original pancreatic tumor plus gain of 11q12-q13 and 22q. Loss of heterozygosity analysis was carried out for 10p14-pter, a region that was lost in 3/8 samples. All of them presented allelic imbalance for all the informative loci. Fluorescence in situ hybridization and Southern analysis were performed to test some candidate oncogenes in 8q24 (MYC) and 15q25-qter (IGF1R and FES). Two of seven tumors showed high-level amplification of MYC relative to the centromere (> 3-fold), another two tumors had low-level amplification (1.5- to 3.0-fold), and one displayed 5.5 MYC signals/cell. In relation to the FES gene, low-level amplification was found in three tumors. Southern analysis showed five cases with a low-level amplification of IGF1R. Our data suggest that either few extra gene copies may be enough for cancer progression or other genes located in these regions are responsible for the amplifications found by CGH.

Origin of trisomy 21 in Down syndrome cases from a Spanish population registry

We have carried out a population-based study on the origin of the extra chromosome 21 in 38 families with Down syndrome (DS) offspring in El Vallès (Spain). From 1991 to 1994, a higher prevalence of DS (22.7/10000 live births, stillbirths and induced abortions) was found compared to the majority of EUROCAT registries. The distribution of trisomy 21 by origin was 88% maternal (90.6% meiosis I, 6.2% meiosis II, 3.1% maternal mosaicism), 5.6% paternal (50% meiosis I, 50% meiosis II) and 5.6% mitotic. The percentage of parental mosaicism was 2.7%. These percentages are similar to those previously reported. Recombination study revealed a maternal meiosis I genetic map of 32.68 cM (approximately one-half the length of the normal female map). Mean maternal age among non-recombinant cases involving MI errors was significantly lower (31.1 years) than among those cases showing one observable crossover (36.1 years) (P<0.05); this could support the hypothesis that 'achiasmate' chromosomes may be subject to aberrant segregation regardless of maternal age.

Comparison of X-ray dose-response curves obtained by chromosome painting using conventional and PAINT nomenclatures

PURPOSE

The compare the suitability of PAINT and conventional nomenclature systems for the construction of chromosome aberration dose-effect curves for X-rays using FISH techniques, and to compare these curves with those based on solid-stained dicentrics analysed in first division metaphases by the FPG technique.

MATERIALS AND METHODS

Blood samples were irradiated at 0.1, 0.25, 0.50, 0.75, 1, 1.5, 2, 3, 4 and 5 Gy 180 kV X-rays. FISH painting was performed using probes for chromosomes 1, 4 and 11 in combination with a pan-centromeric probe.

RESULTS

Translocations showed a higher background frequency than dicentrics. This influences the ratio of translocations:dicentrics at the lower doses and the uncertainties of dose-effect curves for translocations. The dose-effect curves for dicentrics obtained by FISH and solid stain were in close agreement.

CONCLUSION

For short-term biological dosimetry purposes by FISH, the use of dic(BA) (PAINT nomenclature) or total dicentrics (conventional nomenclature) should give similar dose estimates. For dose reconstruction, the use of total or complete translocations result in similar uncertainties.

Follow-up of chimerism in children with hematological diseases after allogeneic hematopoietic progenitor cell transplants

Using in situ hybridization with an X and Y chromosome probe mixture, 106 bone marrow samples from 38 patients with malignant and non-malignant hematological diseases who received sex-mismatched allogeneic hematopoietic progenitor cell transplants (PCT) in a single institution within short-term intervals (1, 3, 6, 12, 24 and >24 months) have been sequentially studied. The patients received either HLA-identical (n = 31) or non-identical (n = 7) PCT. Twenty-six children showed donor chimerism, 10 children showed mixed chimerism (MC) and two children presented autologous reconstitution. Chimerism status with different parameters has been related (age, sex, donor, disease status before PCT, conditioning regimen, GVHD prophylaxis, relapse, GVHD and survival). Our results indicate that female patients (P = 0.011) and a less intensive conditioning regimen (P = 0.039) are significantly associated with the MC status. Mixed chimerism is not, per se, significantly associated with leukemia relapse but an increase of the MC is indicative of clinical relapse.

Study of allelic losses on 3p, 6q, and 17p in human urothelial cancer

Forty-eight transitional cell carcinomas of the bladder and three transitional cell carcinomas of the renal pelvis were examined for loss of heterozygosity (LOH) on chromosomes 3p, 6q, and 17p. The most frequent allelic loss was seen on 17p (18/36, 50%) followed by 6q (6/22, 27%), and 3p (5/22, 23%). In cases with LOH at more than one locus, the same DNA sample often varied in degree of signal reduction for missing alleles. This observation indicates that LOH studies can serve to detect intratumor heterogeneity. No correlation was found between allelic losses at these chromosome arms and tumor grade and stage. Allelic losses on 6q were associated with tumors having a solid growth pattern; in this kind of tumors, allelic losses on 3p were associated with invasion.

Analysis of 3p allelic losses in renal cell carcinomas: comparison with cytogenetic results

We performed a study of loss of heterozygosity (LOH) at 3p by restriction fragment length polymorphism analysis in a series of 22 renal tumors. In 11 cases, molecular results could be compared with those of cytogenetic studies. The highest frequency of allelic losses at 3p was seen in clear cell non-papillary renal tumors, whereas none of the papillary renal cell carcinomas showed LOH at 3p. Allelic losses on 3p were found to be independent of tumor grade or stage or both. One case analyzed showed a discrepancy between cytogenetic and LOH studies. This tumor displayed rearrangements of chromosome 3 and no LOH at the c-RAF-1 (close to the Von Hippel Lindau gene) locus.

Relationship between the DNA content of human chromosomes and their involvement in radiation-induced structural aberrations, analysed by painting

PURPOSE

To study the relationship between the DNA content of human chromosomes and their involvement in radiation-induced structural chromosome aberrations.

MATERIAL AND METHODS

Human lymphocytes were cultured after exposure to 5 Gy of X-rays. FISH-painting was performed for all human chromosomes.

RESULTS

The results indicate that with the exception of chromosome 20, there was a good fit between the DNA content and the number of exchange-type aberrations and the number of breaks. However, there was a significant tendency for short chromosomes to be more affected than expected and for long chromosomes to be less affected than expected. A better fit was observed when, instead of DNA content, the surface area of the chromosome territories obtained from a spherical model was taken into consideration.

CONCLUSIONS

The tendency for short chromosomes to be more involved and long chromosomes to be less involved in exchange-type aberrations could be related not only to their DNA content but also to their interphase territory surface area.

Cytogenetic studies in fetal blood

In order to assess the effectiveness and reliability of cytogenetic diagnosis provided by fetal blood, we report the first 186 cases of fetal blood sampling performed for rapid karyotype between 19-37 weeks of pregnancy in our Prenatal Diagnosis Unit. The overall diagnostic success rate was 98%, achieving 100% in the last period of the study. Chromosomal anomalies were detected in 16% (29/182) of the fetuses. In malformed fetuses this rate increased from 8-9% in isolated malformation or markers of aneuploidy to 50% in multiple malformations. In pregnancies in which a previous cytogenetic study in amniotic fluid was inconclusive, fetal blood made it possible to obtain a definitive result, with no discrepancies found at phenotypic follow-up examination. Interestingly enough, one of the four previously defined as pseudomosaicisms was found to be a non-mosaic in fetal blood, and only 1 of 4 mosaicisms was confirmed in fetal blood. In conclusion, cytogenetic analysis of fetal blood samples appears to be effective, rapid and reliable to establish the fetal karyotype in selected cases.

Hamster origin of metaphases with multiple chromosome rearrangements in first cleavage human-hamster embryos

Laboratories using the human sperm-hamster egg fertilization system to analyse sperm chromosomes obtain, sporadically, metaphases with multiple aberrations. Due to the high number of aberrations, these metaphases cannot be fully karyotyped. In some of them, one or several human chromosomes can be identified, guaranteeing the human origin of the whole metaphase. However, in others, none of the chromosomes can be recognized as human. This latter type of grossly rearranged metaphases is characterized by complex chromatid exchanges, multifragmented chromosomes and pulverized chromosome material. Using fluorescent in-situ hybridization techniques (FISH) with either human or hamster genomic DNA probes, we examined the origin of this second type of metaphase with multiple chromatid exchanges and fragmented chromosomes. Our study demonstrates that all of them hybridize with hamster genomic DNA probes and not with human DNA, proving their hamster origin. Since some of these metaphases seem to be diploid, we suggest that they may arise from hamster eggs that have failed to complete meiosis and have not extruded the second polar body.

Biological dosimetry in simulated in vitro partial irradiations

The assessment by biological dosimetry of the dose received in cases of partial-body exposure to ionizing radiation can be underestimated because irradiated lymphocytes are mixed with non-irradiated ones. To determine if the exposure affects the whole body or only part of it, it may be useful to know the distribution of cells with more than one dicentric chromosome. We established a dose-effect calibration curve for X-rays by analysis of chromosome aberrations. Moreover, in the present work, 20 partial irradiations for four different doses of X-rays (2, 3, 4 and 5 Gy) have been simulated by mixing irradiated and non-irradiated blood in different proportions. In all cases, the 95% confidence intervals of the estimated dose included the real dose of irradiation. However, some difficulties were found for the estimation of the fraction of irradiated cells. In the present study, D0 = 3.8 allows to obtain the best fit between the estimated and the real fraction of irradiated cells.

Dose-response relationship for the induction of chromosomal abnormalities in gamma-irradiated human spermatozoa

The cytogenetic effects of in vitro irradiation on human spermatozoa have been studied by the interspecific in vitro fertilization system between human sperm and hamster oocytes. Semen samples from three healthy men were irradiated at doses of 0.00, 0.10, 0.25, 0.50, 1.00, 2.00, and 4.00 Gy. A total of 340 chromosome complements derived from non-irradiated human spermatozoa and 987 complements from irradiated spermatozoa were analyzed after sequential uniform stain-G banding. Both the frequency of spermatozoa with structural chromosome abnormalities, and the incidence of such abnormalities per cell, showed strong dose-effect relationships that were best expressed by linear-quadratic equations: Y = 0.06413(+/-0.00475) + 0.1982(+/-0.00833)D - 0.00763(+/-0.00204)D2 and Y = 0.07385(+/-0.00838) + 0.23329(+/-0.03124)D + 0.02317(+/-0.00955)D2, respectively. When analyzing separately unrejoined and rejoined structural abnormalities, we found that the incidence of unrejoined lesions was four times higher than the incidence of rejoined anomalies. The induction of unrejoined abnormalities showed a linear, dose-dependent increase, whereas the incidence of rejoined abnormalities showed a quadratic, dose-dependent increase. The distribution of radiation-induced breakpoints was also analyzed. Breakpoints were found to be randomly distributed among chromosomes, but a clustering of breakpoints in G-negative bands was found: 71.5% of breakpoints were located in G-negative bands, and 28.5% in G-positive bands.

Recurrent gains of 1q, 8 and 12 in the Ewing family of tumours by comparative genomic hybridization

Comparative genomic hybridization (CGH) was used to detect copy number changes of DNA sequences in the Ewing family of tumours (ET). We analysed 20 samples from 17 patients. Fifteen tumours (75%) showed copy number changes. Gains of DNA sequences were much more frequent than losses, the majority of the gains affecting whole chromosomes or whole chromosome arms. Recurrent findings included copy number increases for chromosomes 8 (seven out of 20 samples; 35%), 1q (five samples; 25%) and 12 (five samples; 25%). The minimal common regions of these gains were the whole chromosomes 8 and 12, and 1q21-22. High-level amplifications affected 8q13-24, 1q and 1q21-22, each once. Southern blot analysis of the specimen with high-level amplification at 1q21-22 showed an amplification of FLG and SPRR3, both mapped to this region. All cases with a gain of chromosome 12 simultaneously showed a gain of chromosome 8. Comparison of CGH findings with cytogenetic analysis of the same tumours and previous cytogenetic reports of ET showed, in general, concordant results. In conclusion, our findings confirm that secondary changes, which may have prognostic significance in ET, are trisomy 8, trisomy 12 and a gain of DNA sequences in 1q.

Decreased sensitivity to the cytogenetic effects of bleomycin in individuals occupationally exposed to ionizing radiation

In the present work, 12 individuals occupationally exposed to ionizing radiation and 11 unexposed ones were studied to determine the cytogenetic effect of a challenge dose of bleomycin on their phytohemagglutinin stimulated lymphocytes. After bleomycin treatment, the frequencies of chromatid breaks and gaps were significantly lower in the exposed population (p < 0.025 for both types of chromatid alterations). These results could indicate that occupational exposure to ionizing radiation can induce an adaptive response that can be detected by a subsequent treatment with bleomycin.

Chromosome aberrations in human spermatozoa treated with Ca2+ ionophore A23187

Incorporation of A23187 ionophore into the human-hamster fertilization system clearly improves the ability of human spermatozoa to penetrate zona-free hamster oocytes. Thus, an increasing number of laboratories working in human sperm cytogenetics have substituted classical incubation with Biggers-Whitten-Whittingham (BWW) medium plus human serum albumin (HSA) by pretreatment of spermatozoa with calcium ionophore A23187 which directly induces the acrosome reaction in spermatozoa. However, there have been no formal studies on the effects of this ionophore pretreatment. To determine whether calcium ionophore could affect the cytogenetic characteristics of human spermatozoa we compared A23187-treated spermatozoa with controls (only incubated with BWW + HSA) by analysing a total of 447 sperm chromosome complements from two normal donors. Our results show that there are no statistical differences in the frequency and the types of human sperm chromosomal abnormalities between the two methods of sperm treatment. Thus, ionophore A23187 seems not to affect the cytogenetic characteristics of human spermatozoa, and the results of laboratories using either sperm capacitation in BWW + HSA or acrosome reaction by calcium ionophore can be compared.

[Cytogenetic study of 121 patients suffering from various hematologic neoplasms using the in situ hybridization technique]

PURPOSE

In situ hybridization (ISH) is an efficient tool for detecting chromosomal abnormalities in haemopoietic malignancies. Structural and numerical changes typical of most pathological entities can be detected using chromosome-specific probes on interphase or metaphase cells by means of this technique.

PATIENTS AND METHODS

In this report we present chromosome analysis combining conventional cytogenetics with ISH in 121 patients affected with different haematological diseases. We have studied 92 patients with B-chronic lymphoproliferative disorders (B-CLPD), 11 myelodysplastic syndromes (MDS), 17 acute nonlymphocytic leukaemias (ANLL), 1 acute lymphocytic leukaemia and 1 aplastic anaemia. The ISH was carried out with two kind of biotin-labeled probes: a) 8 and 12 centromeric alpha satellite probes and b) whole painting chromosome (WPC) library probes from all the chromosomes except numbers 10, 16, 21, X and Y.

RESULTS

The cytogenetic analysis of B-CLPD has been hampered by several problems. These leukaemic cells have very low spontaneous mitotic activity and the cell response to mitogens is often poor, unpredictable and variable. Even so, an extra chromosome 12 (+ 12) is one of the most frequent abnormal karyotypes reported. ISH and chromosome 12 specific biotinylated alpha satellite DNA probe was applied in 84 patients with B-CLPD. Among 50 patients with typical chronic lymphocytic leukaemia (CLL) the ISH studies showed two signals of hybridization in the 50 cases. By conventional cytogenetics 9 out of 18 atypical CLL showed chromosomal abnormalities and 7 of them trisomy 12. ISH detected trisomy 12 in 11 of these cases. Trisomy 8 is the most frequent karyotypic change in MDS and ANLL. Cytogenetic results revealed a clear extra copy of chromosome 8 in 13 cases. In all of these trisomic cases, the presence of trisomy 8 clone was confirmed by ISH. ISH revealed trisomy 8 not detected by conventional cytogenetics in 7 cases. The yield of trisomy is much higher with the ISH technique than with conventional cytogenetics. Finally, conventional cytogenetics combined with CISS (chromosomal in situ suppression) hybridization was performed in 15 patients affected with different haematological diseases showing structural aberrations, complex karyotypes or marker chromosomes.

CONCLUSIONS

Our results show that ISH can detect both numerical and structural chromosome changes with high specificity and reliability. The fact that chromosome spreads of very poor quality can now be included in such analysis is the decisive advantage of this approach.

Analysis of radiation-induced micronuclei in two-cell human-hamster embryos using telomeric and centromeric FISH probes

Simultaneous, fluorescent in situ hybridization using a centromeric human alpha satellite DNA probe and a telomeric DNA probe was used to analyze the chromosome content of micronuclei induced in two-cell human-hamster embryos by in vitro gamma-ray irradiation of human spermatozoa. In unirradiated samples, about 26% of micronuclei were centromere positive, indicating that both structural chromosome aberrations and numerical changes are involved in the spontaneous production of micronuclei. After exposure of spermatozoa to radiation, a significant increase in the number of micronuclei was found. About 77% of induced micronuclei contained only telomeric signals suggesting that they originated from acentric fragments. However, both centromere-positive and centromere-negative micronuclei increased with radiation dose. These results are consistent with the well known clastogenic effect of ionizing radiation and with its weak aneugenic effect.

Cytogenetic characterization of a familial papillary renal cell carcinoma

We describe the first case of a familial renal cell carcinoma cytogenetically characterized as a papillary renal cell carcinoma. Cytogenetic and molecular studies were performed on primary renal cell carcinomas and normal kidney tissue from two members of the same family. Both patients showed a normal constitutional karyotype. The two tumors analyzed from the first patient showed the numerical chromosome alterations characteristic of papillary renal cell carcinomas. From the four tumors analyzed in the second patient, three of them presented the cytogenetic pattern of papillary renal cell tumors, and the fourth showed only structural chromosome abnormalities with the presence of a del(7)t(7;7) or dup(7) in all metaphases analyzed. Chromosome 3 was cytogenetically unaffected in all tumors from both patients, and restriction fragment length polymorphism analysis performed with probe pEFD145 (3p21.1-p23) did not detect any loss of heterozygosity.

Isochromosome 14q in childhood acute lymphoblastic leukemia

We report a case of childhood acute lymphoblastic leukemia (ALL) with an isochromosome 14q as the sole abnormality. A review of the literature revealed that isochromosome 14 has not been previously reported in ALL. The prognostic significance of this abnormality is compared with that of other hematologic disorders with trisomy 14.

Occupational exposure to radiation induces an adaptive response in human lymphocytes

The in vitro pretreatment of phytohaemagglutinin stimulated human lymphocytes with tritiated thymidine or with low doses of X-rays induces a response that makes these cells less susceptible to further genetic damage induced by subsequent high doses of radiation. This phenomenon has been called 'Adaptive Response' because it is similar to the one described in E. coli. In the present study, we describe that lymphocytes irradiated in vitro at 2 Gy, from individuals occupationally exposed to X and gamma rays, show lower frequencies of dicentrics than those from non-occupationally exposed individuals irradiated in the same conditions. Our results could indicate that an adaptive response can also be induced in lymphocytes in vivo by very low occupational doses of radiation, and that for biological dosimetry purposes it is necessary to know the individual's history of exposure to mutagens.

Induction of micronuclei in human sperm-hamster egg hybrids at the two-cell stage after in vitro gamma-irradiation of human spermatozoa

The efficiency of the micronucleus test to assess radiation-induced chromosomal damage in human spermatozoa has been investigated. Micronuclei were scored in human sperm-hamster egg hybrids at the two-cell stage, after exposure of human spermatozoa to in vitro gamma-rays at doses of 0.00, 0.10, 0.25, 0.50, 1.00, 2.00, and 4.00 Gy. The relationship between the yield of micronuclei per two-cell stage as well as the percentage of two-cell stages with micronuclei and the different doses of irradiation were fitted to linear equations. To evaluate whether scoring micronuclei is useful for the quantification of chromosomal damage occurring in human spermatozoa, induced micronuclei at the different doses of sperm irradiation were compared to the induction of breaks and fragments in sperm-derived chromosomes. After interspecific fertilization of zona-free hamster oocytes by irradiated spermatozoa, a total of 699 fertilized eggs at the two-cell stage and a total of 387 sperm-derived complements were analyzed. The incidence of fertilized eggs with micronuclei at the two-cell stage coincided well with the incidence of sperm-derived chromosome breaks and fragments (e.g., 8.9% vs. 6.7% in the 0.25 Gy group and 52.8% vs. 58.6% in the 4.00 Gy group). A similar correlation was found between the number of micronuclei per two-cell stage and the number of breaks and fragments per sperm complement (0.09 vs. 0.07 in the 0.25 Gy group and 0.71 vs. 0.81 in the 4.00 Gy group). The results show that this test system can be used for the quantification of spontaneous or induced chromosomal damage in human spermatozoa.

Human origin of micronuclei in human x hamster two-cell embryos

Using fluorescence in situ hybridization techniques with either human or hamster genomic DNA probes, we studied the origin of micronuclei in two-cell hybrid embryos obtained from hamster oocytes and gamma-irradiated human spermatozoa. Our study demonstrates that over 99% of micronuclei hybridize with human DNA probes and not with hamster DNA, revealing their human origin. Thus, the micronucleus test represents a good method to evaluate genetic damage in human germ cells, since it is simpler and faster than sperm chromosome studies.

Establishment and validation of a dose-effect curve for gamma-rays by cytogenetic analysis

A dose-effect curve obtained by analysis of dicentric chromosomes after irradiation of peripheral blood samples, from one donor, at 11 different doses of gamma-rays is presented. For the elaboration of this curve, more than 18,000 first division metaphases have been analyzed. The results fit very well to the linear-quadratic model. To validate the curve, samples from six individuals (three controls and three occupationally exposed persons) were irradiated at 2 Gy. The results obtained, when compared with the curve, showed that in all cases the 95% confidence interval included the 2 Gy dose, with estimated dose ranges from 1.82 to 2.19 Gy.

A case of transitional cell carcinoma of the bladder with a del(9)(q11q21.2)

Monosomy for chromosome 9, as well as loss of heterozygosity for markers on this chromosome, has been detected in a high percentage of transitional cell carcinomas (TCC) of the bladder. We report a case of a TCC of the bladder with an interstitial del(9)(q11q21.2) that could be indicative of the presence of a putative tumor-suppressor gene related to bladder tumor progression. To elucidate the role of chromosome 9 in bladder tumors, it would be interesting to study a possible loss of heterozygosity in this chromosome region.

Cytogenetic analysis of lymphocytes from hospital workers occupationally exposed to low levels of ionizing radiation

Cytogenetic studies were performed in lymphocytes from hospital workers exposed to low doses of radiation (1.6-42.71 mSv). When compared with controls, exposed workers showed a significant increase in structural chromosome-type aberrations, acentric fragments being the most frequent alteration. Our results suggest that acentric fragments are good indicators of exposure to very low doses of radiation, although no dose-effect correlation was observed. The incidence of numerical abnormalities (hyperdiploidy) was significantly increased.

[Selective chromosome painting using in situ hybridization]

A method of in situ hybridization with entire chromosome-specific DNA libraries for visualizing individual human chromosomes has been developed and applied to the detection of structural aberrations in both metaphase and interphase cells. Unlabeled human genomic DNA is used to inhibit the cross-hybridization of repetitive sequences in the library that bind to multiple chromosomes. The remaining single-stranded DNA is hybridized to specimens of interest and detected with fluorescent or enzyme labeled biotin conjugates following post-hybridization washes. This general approach is called "chromosome painting" or "chromosomal in situ suppression (CISS)" hybridization. In the present report, DNA inserts from recombinant libraries from chromosomes 1, 4, and 9 has been applied on controls and patients in order to decorate specifically their complementary chromosomes. Numerical changes, deletions and chromosomal translocations involving these chromosomes can be strikingly visualized.

New chromosomal abnormality. t(1;19;?) in a case of B-chronic lymphocytic leukemia

Cytogenetic analysis was performed on peripheral blood cells stimulated with interleukin 6 (IL-6), lipopolysaccharide from Escherichia coli (LPS), phytohemagglutinin (PHA), pokeweed mitogen (PWM) and tetradecanoyl-phorbol-acetate (TPA), in a patient with B-chronic lymphocytic leukemia, showing a t(1;19;?) translocation as the sole abnormality. To our knowledge, this translocation has not been described before in any human neoplasia. In this case, the poor response to therapy (survival time 4 months) suggested that t(1;19;?) could be related to an aggressive course of the disease.

Cytogenetic studies in acute nonlymphocytic leukemia

Cytogenetic studies were performed in 74 untreated patients with acute nonlymphocytic leukemia (ANLL) between 1985 and 1988. Among 56 patients who were examined successfully at the time of diagnosis, 36 had abnormal karyotypes (64.2%). The distribution of chromosome abnormalities was uneven, according to the categories of the French-American-British (FAB) nomenclature. The highest frequency of chromosome abnormalities was observed in ANLL M4 with bone marrow (BM) eosinophilia (M4Eo). Numerical changes were observed in 11 cases; chromosome 8 was most frequently gained (11 patients), whereas chromosome 7 was most frequently lost (4 patients). Structural rearrangements were detected in 18 patients. Involvement of 16q22 was noted in 7 patients, 5q- was noted in 5, t(8;21) in 3, t(1;7) in 2, del(20) in 2, and involvement of 11q23 was noted in 2. The inversion of chromosome 16 was restricted to the M4Eo subtype. This study identified a novel abnormality [inv(2) (p11.2q11.2)] that had not been reported previously by other investigators.