Heterogeneity of lineage involvement by trisomy 8 in myelodysplastic syndrome. A multiparameter analysis combining conventional cytogenetics, DNA in situ hybridization, and bone marrow culture studies

Trisomy 8, a Cytogenetic Abnormality in Myelodysplastic Syndromes, Is Constitutional or Not?

Isolated trisomy 8 is not considered presumptive evidence of myelodysplastic syndrome (MDS) in cases without minimal morphological criteria. One reason given is that trisomy 8 (+8) can be found as a constitutional mosaicism (cT8M). We tried to clarify the incidence of cT8M in myeloid neoplasms, specifically in MDS, and the diagnostic value of isolated +8 in MDS. Twenty-two MDS and 10 other myeloid neoplasms carrying +8 were studied. Trisomy 8 was determined in peripheral blood by conventional cytogenetics (CC) and on granulocytes, CD3+ lymphocytes and oral mucosa cells by fluorescence in situ hybridization (FISH). In peripheral blood CC, +8 was seen in 4/32 patients. By FISH, only one patient with chronic myelomonocytic leukemia showed +8 in all cell samples and was interpreted as a cT8M. In our series +8 was acquired in all MDS. Probably, once discarded cT8M by FISH from CD3+ lymphocytes and non-hematological cells, +8 should be considered with enough evidence to MDS.

Clonogenic acute myelogenous leukemia cells are heterogeneous with regard to regulation of differentiation and effect of epigenetic pharmacological targeting

Differentiation-inducing therapy with the DNA-methylation inhibitor Decitabine (5'-aza-deoxycytidine) and histone deacetylase (HDAC) inhibitors are now considered in acute myelogenous leukemia (AML). We investigated the in vitro effects of Decitabine and two structurally unrelated HDAC inhibitors (Sodium 4-phenyl butyrate, Tricostatin A) on clonogenic AML cells. Based on morphological criteria we identified four major colony types: (i) non-erythroid colonies, (ii) erythroid colonies that were detected only for a subset of patients and could be further sub classified into mature and immature forms, and (iii) intermediate colonies. Erythroid differentiation was associated with low CD34 expression. The colonies showed differences in morphology, viability, cell cycle distribution and expression of differentiation markers. Both Decitabine and the two HDAC inhibitors altered AML cell expression of differentiation markers, whereas the drugs did not have any major influence on cell cycle distribution. However, the pharmacological effects differed between the four colony subsets, and differences were also detected between the two HDAC inhibitors. We conclude that clonogenic AML cells can be classified into well-defined subsets based on their differentiation, and these subsets differ in their biological characteristics as well as their response to pharmacological targeting of epigenetic regulation.

Trisomy 8 as the sole chromosomal aberration in acute myeloid leukemia and myelodysplastic syndromes

Trisomy 8 as the sole abnormality is the most common karyotypic finding in acute myeloid leukemia (AML) and myelodysplastic syndromes (MDS), occurring in approximately 5% and 10% of the cytogenetically abnormal cases, respectively. However, despite the high frequency of +8, much remains to be elucidated as regards its epidemiology, etiology, clinical impact, association with other chromosomal abnormalities, cell of origin, and functional and pathogenetic consequences. Here, we summarize and review these various aspects of trisomy 8, focusing on AMLs and MDS harboring this abnormality as a single change.

Genetic testing in the myelodysplastic syndromes: molecular insights into hematologic diversity

The myelodysplastic syndromes (MDS) are associated with a diverse set of acquired somatic genetic abnormalities. Bone marrow karyotyping provides important diagnostic and prognostic information and should be attempted in all patients who are suspected of having MDS. Fluorescent in situ hybridization (FISH) studies on blood or marrow may also be valuable in selected cases, such as patients who may have 5q- syndrome or those who have undergone hematopoletic stem cell transplantation. The MDS-associated cytogenetic abnormalities that have been defined by karyotyping and FISH studies have already contributed substantially to our current understanding of the biology of malignant myeloid disorders, but the pathobiological meaning of common, recurrent chromosomal lesions such as del(5q), del(20q), and monosomy 7 is still unknown. The great diversity of the cytogenetic findings described in MDS highlights the molecular heterogeneity of this cluster of diseases. We review the common and pathophysiologically interesting genetic abnormalities associated with MDS, focusing on the clinical utility of conventional cytogenetic assays and selected FISH studies. In addition, we discuss a series of well-defined MDS-associated point mutations and outline the potential for further insights from newer techniques such as global gene expression profiling and array-based comparative genomic hybridization.

Engraftment of NOD/SCID-beta2 microglobulin null mice with multilineage neoplastic cells from patients with myelodysplastic syndrome

The development of immunodeficient mouse xenograft models has greatly facilitated the investigation of some human hematopoietic malignancies, but application of this approach to the myelodysplastic syndromes (MDSs) has proven difficult. We now show that cells from most MDS patients (including all subtypes) repopulate nonobese diabetic-severe combined immunodeficient (scid)/scid-beta2 microglobulin null (NOD/SCID-beta2m(-/-)) mice at least transiently and produce abnormal differentiation patterns in this model. Normal marrow transplants initially produce predominantly erythroid cells and later predominantly B-lymphoid cells in these mice, whereas most MDS samples produced predominantly granulopoietic cells. In 4 of 4 MDS cases, the regenerated cells showed the same clonal markers (trisomy 8, n = 3; and 5q-, n = 1) as the original sample and, in one instance, regenerated trisomy 8(+) B-lymphoid as well as myeloid cells were identified. Interestingly, the enhanced growth of normal marrow obtained in NOD/SCID-beta2m(-/-) mice engineered to produce human interleukin-3, granulocyte-macrophage colony-stimulating factor, and Steel factor was seen only with 1 of 7 MDS samples. These findings support the concept that human MDS originates in a transplantable multilineage hematopoietic stem cell whose genetic alteration may affect patterns of differentiation and responsiveness to hematopoietic growth factors. They also demonstrate the potential of this new murine xenotransplant model for future investigations of MDS.

Pentasomy 8q in therapy-related myelodysplastic syndrome due to cyclophosphamide therapy for fibrosing alveolitis

Trisomy 8/8q is a common cytogenetic event in myelocytic malignancies, ranging from myelodysplastic syndrome (MDS) to acute myelocytic leukemia (AML) to blastic transformation of chronic myelocytic leukemia. Isochromosome 8q results in the same gene dosage effect. Duplication of i(8q), resulting in pentasomy 8q, has been reported only in two cases of AML. A patient with fibrosing alveolitis on prolonged cyclophosphamide treatment developed therapy-related MDS. Karyotyping, FISH, and CGH analysis showed a duplicated i(8q) among other complex abnormalities. The clinical features of 11 cases of myelocytic leukemia with pentasomy and hexasomy 8/8q were summarized. Compared with trisomy and tetrasomy 8, significant features included reduced median survival (90 days), treatment refractoriness (even with transplantation), monocytic differentiation, trilineage dysplasia, and radiation or toxin exposure. Increasing copy numbers of chromosome 8/8q may therefore be a marker of advanced leukemic evolution, exposure to toxins, underlying myelodysplasia, and an overall poor prognosis.

Incidence and significance of cryptic chromosome aberrations detected by fluorescence in situ hybridization in acute myeloid leukemia with normal karyotype

To better define the incidence and significance of cryptic chromosome lesions in acute myeloid leukemia (AML), fluorescence in situ hybridization (FISH) studies were performed in interphase cells and, when appropriate, in metaphase cells and in morphologically intact BM smears. Fifty-five adult de novo AML (group A) and 27 elderly AML or AML after myelodysplastic syndrome (AML-MDS) (group B) were tested using probes detecting the following anomalies: -5, -7, +8, deletions of 5q31, 7q31, 12p13/ETV6, 17p13/p53, 20q11. All the patients had a normal karyotype in more than 20 cells and tested negative for the common AML-associated fusion genes. No patient in group A was found to carry occult chromosome anomalies, whereas 8/27 patients in group B (P < 0.0001) showed 5q31 or 7q31 deletion (three cases each), a 17p13/p53deletion or trisomy 8 (one case each) in 33-60% interphase cells. Metaphase cells showed only one hybridization signal at 5q31 (three cases) and 7q31 (one case), whereas two normal signals at 7q31 and chromosome 8 centromeres were seen in two patients with 7q deletion and trisomy 8 in interphase cells. The majority of blast cells (76-94%) carried the chromosome anomaly in all cases; erythroid involvement in a minority of cells was seen in three patients. In group B, the presence of occult chromosome anomalies was associated with exposure to myelotoxic agents in the workplace (5/8 cases vs 3/19, P = 0.026) and with a lower complete remission rate (0/6 patients vs 7/12, P = 0.024). We arrived at the following conclusions: (1) cryptic chromosome deletions in the order of a few hundred kb magnitude may be found in a fraction of elderly AML or MDS-related AML and not in de novo adult AML with normal karyotype; (2) these chromosome lesions are usually represented by submicroscopic rearrangements; (3) they display a specific pattern of cell-lineage involvement arguing in favor of their role in the outgrowth of the leukemic blast cells; (4) they are associated with a history of exposure to myelotoxic agents in the workplace and, possibly, with resistance to induction treatment.

Pure red cell aplasia developing into myeloproliferation with myelodysplasia and subsequent leukemia after cyclosporin A therapy

We describe a very rare case of a patient who presented with red cell aplasia that later developed into myeloproliferation with myelodysplasia and eventually leukemia. A 63-year-old man presented with anemia and reticulocytopenia in May 1997. A bone marrow examination revealed erythroid aplasia with normal production of myeloid cells and megakaryocytes with a normal karyotype. After the diagnosis of pure red cell aplasia was made, the patient was treated with prednisolone and then with cyclosporin A (CyA). Two weeks after the initiation of CyA treatment, the peripheral reticulocyte count began to increase with a regrowth of erythroid cells in the bone marrow. Meanwhile, the peripheral white blood cell and platelet counts also increased to more than 10,000/microL and 1,000,000/microL, respectively. Examination of a bone marrow aspirate in December 1997 revealed myelodysplastic changes with trisomy 8. Despite the discontinuation of CyA and the administration of 1-beta-D-arabinofuranosylcytosine stearyl monophosphate, leukemia developed in August 1998. In September 1998, the patient died of sepsis during a neutropenic period that followed remission-induction therapy. In the mechanism of pathogenesis, CyA may induce upon pure red cell aplasia a secondary myeloproliferative disorder with myelodysplasia and leukemia. An alternative possibility is that CyA reduces autoimmune-mediated suppression of the underlying stem cell disorder and that the result of this reduction is the manifestation of myeloproliferation and leukemia.

Expansion of trisomy 8 and Sweet syndrome in a prolonged course of aplastic anemia

We describe a 17-year-old boy with aplastic anemia who had Sweet syndrome develop with increasing expansion of trisomy 8. The diagnosis of aplastic anemia was made at 6 years of age. Cytopenias partially responded to danazol therapy. Cytogenetic studies of bone marrow (BM) cells were normal until the detection of trisomy 8 at 14 years of age. This clone increased with the progression of cytopenias. Cell sorting and fluorescence in situ hybridization analysis revealed that trisomy 8 was present only in nonlymphoid elements. When the patient was 17 years of age, Sweet syndrome developed. BM study showed myelodysplastic features, in which trisomy 8 occupied 74% of BM cells with additional chromosomal changes. Trisomy 8 may contribute to the late transformation of myeloid lineages in BM failure.

Clinical importance of interphase cytogenetics detecting occult chromosome lesions in myelodysplastic syndromes with normal karyotype

At diagnosis, approximately half of myelodysplastic (MDS) patients presents a normal karyotype by conventional cytogenetic analysis (CCA). Fluorescent in situ hybridization (FISH) is more sensitive than CCA allowing for the detection of minor clones and of submicroscopic lesions. We have analyzed by FISH 101 MDS patients with normal karyotype for the occurrence of the abnormalities which are most frequently observed in MDS (ie -5/5q-, -7/7q-, +8, 17p-). In 18 patients, 15 to 32% of interphase cells were found to carry one FISH abnormality. Six patients presented trisomy 8, five had del(5)(q31), five del(7)(q31), one monosomy 7 and one del(17)(p13). FISH abnormalities were more frequently observed among patients with an increased percentage of bone marrow blasts (P = 0.001). FISH abnormalities were also associated with a higher rate of progression into AML (13/18 vs 12/83, P < 0.001) and were predictive for a worse prognosis (P < 0.001). Multivariate analysis indicated that FISH positivity and IPSS risk group were independent predictors for a poor survival (P = 0.0057 and 0.0123, respectively) and for leukemic transformation (P = 0.0006 and 0.035, respectively). Leukemic transformation in FISH-positive patients was associated in all cases with an expansion of the abnormal clone. Our data demonstrated that a significant proportion of MDS patients with normal karyotype presented, if analyzed by FISH, clones of cytogenetically abnormal cells which played a determinant role in the progression of the disease. The presence of FISH abnormalities identified a group of MDS patients with normal karyotype characterized by an inferior prognosis.

High rate of CAD gene amplification in human cells deficient in MLH1 or MSH6

MutS and MutL homologs have been implicated in multiple genetic stabilization pathways. The activities participate in the correction of DNA biosynthetic errors, are involved in cellular responses to certain types of DNA damage, and serve to ensure the fidelity of genetic recombination. We show here that the rate of CAD (carbamyl-P synthetase/aspartate transcarbamylase/dihydroorotase) gene amplification is elevated 50- to 100-fold in human cell lines deficient in MLH1 or MSH6, as compared with mismatch repair-proficient control cells. Fluorescence in situ hybridization indicates that these amplification events are the probable consequence of unequal sister chromatid exchanges involving chromosome 2, as well as translocation events involving other chromosomes. These results implicate MutS alpha and MutL alpha in the suppression of gene amplification and suggest that defects in this genetic stabilization function may contribute to the cancer predisposition associated with mismatch repair deficiency.

Acquisition of secondary structural chromosomal changes in pediatric ewing sarcoma is a probable prognostic factor for tumor response and clinical outcome

BACKGROUND

The Ewing sarcoma (ES) group of tumors commonly have the t(11;22)(q24;q12) or other rearrangements involving 22q12. In addition to these consistent aberrations, both numeric and structural aberrations have been reported: namely gains of chromosomes 8 and 12, the unbalanced translocation t(1;16), and deletions at the short arm of chromosome 1.

METHODS

To evaluate the frequency and to study the prognostic implications of some of these aberrations in children, the authors performed a pilot study of 26 ES pediatric patients by classic cytogenetics and/or interphase fluorescence in situ hybridization (FISH) and compared these data with clinical parameters.

RESULTS

Gains of chromosomes 8 and 12 were detected, by interphase FISH, in 48% (10 of 21) and 38% (6 of 16) of the tumors, respectively, and this was not significant with respect to treatment response. Statistical analysis revealed that the presence of additional secondary structural chromosomal aberrations was associated with an unfavorable outcome (P = 0.0034 as an independent prognostic value as an unfavorable marker). Presence of metastasis at diagnosis also was found to be associated with poor outcome (P = 0.0131). Spectral karyotyping analysis was shown to facilitate the detection of more complex structural chromosomal aberrations in a representative ES tumor.

CONCLUSIONS

It is important to determine whether additional structural chromosomal aberrations are present in ES tumors because it appears that a more complex karyotype with multiple chromosomal aberrations is associated with poor outcome in ES.

Trisomy 8 and monosomy 7 detected in bone marrow using primed in situ labeling, fluorescence in situ hybridization, and conventional cytogenetic analyses. A study of 54 cases with hematological disorders

Trisomy 8 and monosomy 7 are the two most frequent aneuploidies found in hematological disorders such as myelodysplastic syndrome (MDS) and acute myeloid leukemia (AML). In this study, primed in situ labeling (PRINS), fluorescence in situ hybridization (FISH) and conventional cytogenetic approaches were used to investigate 54 cases of hematopoietic disorders. Of these cases, there were 22 cases of trisomy 8, 2 cases of tetrasomy 8, 14 cases of monosomy 7, and 16 cases with two copies of both chromosomes 7 and 8. PRINS was carried out in interphase nuclei of bone marrow samples using primers that can specifically detect alpha-satellite DNA sequences of chromosomes 7 and 8. In parallel, using the alpha-satellite probes for chromosomes 7 and 8, FISH was performed for all the cases. PRINS and FISH techniques showed similar specificity and sensitivity. In comparison to FISH, PRINS is more advantageous since it is a faster, easier, and more cost-effective technique. Additionally, for most of the cases, a higher proportion of aneuploidy was detected in metaphases using conventional cytogenetics, as compared to the one found in interphase nuclei identified with PRINS and FISH techniques. In other words, for these cases, the cells with trisomy 8 or monosomy 7, had a distinct proliferative advantage compared to the disomic cell population. Therefore, to better quantify the proportion of aneuploid cells in bone marrow, we recommend to investigate the frequency of aneuploidy in nuclei using PRINS, rather than studying only the dividing cells as detected by conventional cytogenetic techniques.

Molecular genetics and cytogenetics of myeloproliferative disorders

The myeloproliferative disorders are believed to represent clonal malignancies resulting from transformation of a pluripotent stem cell. X-inactivation patterns of peripheral blood cells have been proposed as a useful diagnostic tool but this method is limited by the finding of a clonal X-inactivation pattern in a significant proportion of normal elderly women. There is no pathognomonic chromosomal abnormality associated with the myeloproliferative disorders. However, consistent acquired cytogenetic changes include del(20q), del(13q), trisomy 8 and 9 and duplication of segments of 1q, all of which have been observed at diagnosis or before cytoreductive therapy and therefore represent early lesions which contribute to the pathogenesis of these disorders. Although, the acquired molecular defects underlying most myeloproliferative disorders have not yet been elucidated, translocations associated with the rare 8p11 syndrome have permitted identification of a novel fusion protein. The role of a number of candidate genes in the other myeloproliferative disorders has also been studied, but no mutations have been identified so far. It is likely that a number of genes will be involved, given the varied phenotypes of the diseases. Identification of causal genes will be of considerable interest to both clinicians, who currently lack a specific and sensitive diagnostic test, and scientists interested in fundamental issues of stem cell behaviour.

Detection of minimal residual disease in an AML patient with trisomy 8 using interphase fish

Patients with acute myeloid leukemia (AML) or myelodysplastic syndrome (MDS) often exhibit clonal chromosomal abnormalities. Using a probe for the centromeric region of chromosome 8, fluorescence in situ hybridization (FISH) on interphase cells was used to detect trisomy 8 in an AML patient whose leukemia was characterised by the karyotype 47, XY, +8, del(9) (q21.1q32). We have demonstrated using FISH the presence of the trisomy at all stages of the patient's disease course (including remission, peripheral blood cell harvest and relapse), whereas conventional karyoptypic analysis was only able to detect the trisomy at diagnosis and clinical relapse. We have also shown using immunophenotyping, cell sorting and FISH, that the trisomic cells in this patient were restricted to the CD34+ subset of blood and bone marrow and could not be found in the CD 34-, T or B cell compartment. Overall we have shown FISH to be a rapid, quantitative method for the detection of cells with numerical chromosome abnormalities. FISH analysis of interphase cells provides valuable information on the status of the whole population, rather than just cycling cells, and can be applied successfully to monitor the level of leukemic cells.

Detection of trisomy 8 using conventional cytogenetic techniques and interphase FISH analysis in 34 myeloid disorders: a comparative study

Trisomy for chromosome 8 is one of the most common chromosome abnormalities detected in myeloid disorders. However, and despite its great incidence, its biologic significance remains poorly understood. Recently, some reports have shown the existence of masked trisomy 8 in myeloid disorders. To try to detect occult trisomy 8, we performed a study in which 34 myeloid disorders with apparent normal karyotypes using conventional cytogenetic techniques were analyzed using fluorescence in situ hybridization (FISH) analysis. Masked trisomy 8 was not detected in any of the 34 cases studied. This suggests that trisomy 8 may be a rare event in myeloid disorders in which an optimal conventional cytogenetic analysis has been performed. The acquisition of trisomy 8 either in early neoplastic stages in some cases or in late neoplastic stages in others and the absence of masked trisomy 8 suggest that this chromosome alteration may not be essential to the development of myeloid disorders.