Combined immunophenotyping and FISH identifies the involvement of B-cells in 5q- syndrome

Quantitative evaluation of treatment response to lenalidomide by applying fluorescence in situ hybridization for peripheral blood granulocytes in a patient with 5q- syndrome

The introduction of lenalidomide has significantly improved clinical outcomes in myelodysplastic syndrome (MDS) with isolated interstitial deletion of the long arm of chromosome 5 (del(5q)) (5q– syndrome). These days, MDS with isolated del(5q) includes cases with one additional chromosome abnormality other than monosomy 7 or del(7q), and so we need a better way to monitor tumor cells in each patient than the clinical parameters used to date. An 82-year-old woman with MDS with isolated del(5q) was treated with lenalidomide daily for 21 days in a 4-week cycle. Fluorescence in situ hybridization with CSF1R located at 5q was applied to the peripheral blood samples. Because mature lymphocytes are not involved in the MDS clone, based on the nuclear morphology, polymorphonuclear cells (PMNs) and round-shaped nuclear cells (RSNs) were separately evaluated during treatment. After a single course of treatment, the number of PMNs with del(5q) decreased; by the end of the second course of treatment, both PMNs and RSNs with del(5q) had disappeared. The dynamics of 5q– PMNs is a simple but rapid and reliable indicator to confirm the effect of lenalidomide in MDS with del(5q).

Developing Digital Photomicroscopy

(1) The need for efficient ways of recording and presenting multicolour immunohistochemistry images in a pioneering laboratory developing new techniques motivated a move away from photography to electronic and ultimately digital photomicroscopy. (2) Initially broadcast quality analogue cameras were used in the absence of practical digital cameras. This allowed the development of digital image processing, storage and presentation. (3) As early adopters of digital cameras, their advantages and limitations were recognised in implementation. (4) The adoption of immunofluorescence for multiprobe detection prompted further developments, particularly a critical approach to probe colocalization. (5) Subsequently, whole-slide scanning was implemented, greatly enhancing histology for diagnosis, research and teaching.

Telomere dynamics in patients with del (5q) MDS before and under treatment with lenalidomide

Myelodysplastic syndrome (MDS) associated with an acquired, isolated deletion of chromosome 5q (del (5q) MDS), represent a clonal disorder of hematopoiesis and a clinically distinct entity of MDS. Treatment of del (5q) MDS with the drug lenalidomide has significantly improved quality of life leading to transfusion independence and complete cytogenetic response rates (CCR) in the majority of patients. Telomeres are located at the end of eukaryotic chromosomes and are linked to replicative history/potential as well as genetic (in) stability of hematopoietic stem cells. Here, we analyzed telomere length (TL) dynamics before and under lenalidomide treatment in the peripheral blood and/or bone marrow of del (5q) patients enrolled in the LEMON-5 study (NCT01081431). Hematopoietic cells from del (5q) MDS patients were characterized by significantly shortened TL compared to age-matched healthy controls. Telomere loss was more accelerated in patients with longer disease duration (>2 years) and more pronounced cytopenias. Sequential analysis under lenalidomide treatment revealed that previously shortened TL in peripheral blood cells was significantly "elongated" towards normal levels within the first six months suggesting a shift from clonal del (5q) cells towards normal hematopoiesis in lenalidomide treated MDS patients. Taken together our findings suggest that the development of the del (5q) clone is associated with accelerated telomere shortening at diagnosis. However, upon induction of CCR and reoccurrence of normal hematopoiesis, the lack of a persistent TL deficit argues against telomere-mediated genetic instability neither as a disease-promoting event of del (5q) MDS nor for lenalidomide mediated development of secondary primary malignancies of the hematopoietic system in responding patients.

Recent Advances in the 5q- Syndrome

The 5q- syndrome is the most distinct of the myelodysplastic syndromes (MDS) and patients with this disorder have a deletion of chromosome 5q [del(5q)] as the sole karyotypic abnormality. Several genes mapping to the commonly deleted region of the 5q- syndrome have been implicated in disease pathogenesis in recent years. Haploinsufficiency of the ribosomal gene RPS14 has been shown to cause the erythroid defect in the 5q- syndrome. Loss of the microRNA genes miR-145 and miR-146a has been associated with the thrombocytosis observed in 5q- syndrome patients. Haploinsufficiency of CSNK1A1 leads to hematopoietic stem cell expansion in mice and may play a role in the initial clonal expansion in patients with 5q- syndrome. Moreover, a subset of patients harbor mutation of the remaining CSNK1A1 allele. Mouse models of the 5q- syndrome, which recapitulate the key features of the human disease, indicate that a p53-dependent mechanism underlies the pathophysiology of this disorder. Importantly, activation of p53 has been demonstrated in the human 5q- syndrome. Recurrent TP53 mutations have been associated with an increased risk of disease evolution and with decreased response to the drug lenalidomide in del(5q) MDS patients. Potential new therapeutic agents for del(5q) MDS include the translation enhancer L-leucine.

Clonal origin and evolution of myelodysplastic syndrome analyzed by dysplastic morphology and fluorescence in situ hybridization

Myelodysplastic syndromes (MDS) are clonal disorders of hematopoietic stem/progenitor cells. As bone marrow cells are extremely diverse in these disorders, the origin and evolution of MDS clones are difficult to identify and trace. Cellular dysplasia is a distinct morphologic feature; however, whether the dysplastic cells represent abnormal clones or only nonspecific superficial phenomena remains to be clarified. To address this question, 97 patients were examined for dysplasia features, among them bone marrow slides of 16 patients with chromosomal abnormalities were subjected to fluorescence in situ hybridization (FISH) to determine the karyotype of these dysplastic cells. Furthermore, the emerging frequencies of abnormal karyotypes in various differentiated stages of each lineage were also evaluated by a combination of morphological evaluation and FISH karyotyping. Our results indicate that the overall percentage of dysplastic cells does not differ significantly among the WHO subtypes, while the megakaryoid lineage presents the most frequent dysplasia in all subtypes. A positive correlation between dysplastic cells and FISH-detectable abnormal clones was observed, but the dysplastic morphology was not a specific feature of FISH-detectable abnormal clones. FISH-detectable abnormal clones can differentiate into mature granulocytes and erythrocytes, in coexistence with cells originating from the normal clones.

Stem cell origin of myelodysplastic syndromes

Myelodysplastic syndromes (MDS) are common hematologic disorders that are characterized by decreased blood counts due to ineffective hematopoiesis. MDS is considered a 'preleukemic' disorder linked to a significantly elevated risk of developing an overt acute leukemia. Cytopenias can be observed in all three myeloid lineages suggesting the involvement of multipotent, immature hematopoietic cells in the pathophysiology of this disease. Recent studies using murine models of MDS as well as primary patient-derived bone marrow samples have provided direct evidence that the most immature, self-renewing hematopoietic stem cells (HSC), as well as lineage-committed progenitor cells, are critically altered in patients with MDS. Besides significant changes in the number and distribution of stem as well as immature progenitor cells, genetic and epigenetic aberrations have been identified, which confer functional changes to these aberrant stem cells, impairing their ability to proliferate and differentiate. Most importantly, aberrant stem cells can persist and further expand after treatment, even upon transient achievement of clinical complete remission, pointing to a critical role of these cells in disease relapse. Ongoing preclinical and clinical studies are particularly focusing on the precise molecular and functional characterization of aberrant MDS stem cells in response to therapy, with the goal to develop stem cell-targeted strategies for therapy and disease monitoring that will allow for achievement of longer-lasting remissions in MDS.

Acquired EVI1 rearrangement involved in the transformation from 5q- syndrome to pre-B lymphocytic leukemia in a Chinese patient

The anomalous EVI1 rearrangements/t(3;3)(q21;q26) is more frequently found in myelocytic malignancies. 5q- syndrome is a newly defined subtype of myelodysplastic syndrome (MDS) first proposed by the World Health Organization in 2001. Cases of acute lymphocytic leukemia (ALL) with 5q- anomaly or t(3;3)/EVI1 rearrangement have rarely been reported. We report a rare 5q- syndrome case which ultimately transformed to acute lymphocytic leukemia accompanied by a secondary cytogenetic anomaly of t(3;3)(q21;q26) and EVI1 rearrangement around 3 years after the diagnosis of 5q- syndrome. This rare case suggests that the 5q- clone of MDS may originate from a multipotent cell with a capacity to differentiate toward both myeloid and lymphoid lineages. It also indicates that although the t(3;3)/EVI1 rearrangement is mostly related to myelocytic neoplasms, the t(3;3)/EVI1-rearrangement may also play an important role in the development of ALL. The results of the necessary tests must be analyzed sufficiently prior to making a final diagnosis.

Advances in the 5q- syndrome

The 5q- syndrome is the most distinct of all the myelodysplastic syndromes with a clear genotype/phenotype relationship. The significant progress made during recent years has been based on the determination of the commonly deleted region and the demonstration of haploinsufficiency for the ribosomal gene RPS14. The functional screening of all the genes in the commonly deleted region determined that RPS14 haploinsufficiency is the probable cause of the erythroid defect in the 5q- syndrome. A mouse model of the human 5q- syndrome has now been created by chromosomal engineering involving a large-scale deletion of the Cd74-Nid67 interval (containing RPS14). A variety of lines of evidence support the model of ribosomal deficiency causing p53 activation and defective erythropoiesis, including most notably the crossing of the "5q- mice" with p53-deficient mice, thereby ameliorating the erythroid progenitor defect. Emerging evidence supports the notion that the p53 activation observed in the mouse model may also apply to the human 5q- syndrome. Other mouse modeling data suggest that haploinsufficiency of the microRNA genes miR-145 and miR-146a may contribute to the thrombocytosis seen in the 5q- syndrome. Lenalidomide has become an established therapy for the 5q- syndrome, although its precise mode of action remains uncertain.

Myelodysplastic syndromes: biology and treatment

Optimal management of patients with myelodysplastic syndromes (MDS) requires an insight into the biology of the disease and the mechanisms of action of the available therapies. This review focuses on low-risk MDS, for which chronic anaemia and eventual progression to acute myeloid leukaemia are the main concerns. We cover the updated World Health Organization classification, the latest prognostic scoring system, and describe novel findings in the pathogenesis of 5q- syndrome. We perform in depth analyses of two of the most widely used treatments, erythropoietin and lenalidomide, discussing mechanisms of action, reasons for treatment failure and influence on survival.

Integrated genomic analysis implicates haploinsufficiency of multiple chromosome 5q31.2 genes in de novo myelodysplastic syndromes pathogenesis

Deletions spanning chromosome 5q31.2 are among the most common recurring cytogenetic abnormalities detectable in myelodysplastic syndromes (MDS). Prior genomic studies have suggested that haploinsufficiency of multiple 5q31.2 genes may contribute to MDS pathogenesis. However, this hypothesis has never been formally tested. Therefore, we designed this study to systematically and comprehensively evaluate all 28 chromosome 5q31.2 genes and directly test whether haploinsufficiency of a single 5q31.2 gene may result from a heterozygous nucleotide mutation or microdeletion. We selected paired tumor (bone marrow) and germline (skin) DNA samples from 46 de novo MDS patients (37 without a cytogenetic 5q31.2 deletion) and performed total exonic gene resequencing (479 amplicons) and array comparative genomic hybridization (CGH). We found no somatic nucleotide changes in the 46 MDS samples, and no cytogenetically silent 5q31.2 deletions in 20/20 samples analyzed by array CGH. Twelve novel single nucleotide polymorphisms were discovered. The mRNA levels of 7 genes in the commonly deleted interval were reduced by 50% in CD34+ cells from del(5q) MDS samples, and no gene showed complete loss of expression. Taken together, these data show that small deletions and/or point mutations in individual 5q31.2 genes are not common events in MDS, and implicate haploinsufficiency of multiple genes as the relevant genetic consequence of this common deletion.

Haploinsufficiency of RPS14 in 5q- syndrome is associated with deregulation of ribosomal- and translation-related genes

We have previously demonstrated haploinsufficiency of the ribosomal gene RPS14, which is required for the maturation of 40S ribosomal subunits and maps to the commonly deleted region, in the 5q- syndrome. Patients with Diamond-Blackfan anaemia (DBA) show haploinsufficiency of the closely related ribosomal protein RPS19, and show a consequent downregulation of multiple ribosomal- and translation-related genes. By analogy with DBA, we have investigated the expression profiles of a large group of ribosomal- and translation-related genes in the CD34(+) cells of 15 myelodysplastic syndrome (MDS) patients with 5q- syndrome, 18 MDS patients with refractory anaemia (RA) and a normal karyotype, and 17 healthy controls. In this three-way comparison, 55 of 579 ribosomal- and translation-related probe sets were found to be significantly differentially expressed, with approximately 90% of these showing lower expression levels in the 5q- syndrome patient group. Using hierarchical clustering, patients with the 5q- syndrome could be separated both from other patients with RA and healthy controls solely on the basis of the deregulated expression of ribosomal- and translation-related genes. Patients with the 5q- syndrome have a defect in the expression of genes involved in ribosome biogenesis and in the control of translation, suggesting that the 5q- syndrome represents a disorder of aberrant ribosome biogenesis.

Immature and mature monocyte-derived dendritic cells in myelodysplastic syndromes of subtypes refractory anemia or refractory anemia with ringed sideroblasts display an altered cytokine profile

Dendritic cells (DC) are pivotal for T cell-mediated immunity. We investigated the early and terminal maturation of monocyte-derived DC (MoDC) in myelodysplastic syndromes (FAB subtypes refractory anemia (MDS-RA) or refractory anemia with ringed sideroblasts (MDS-RARS)). Immature MoDC were obtained by culture of monocytes with GM-CSF and IL-4 for 8 days. To obtain mature MoDC, TNF-alpha was added during the final three culture days. T cell proliferation and T cell cytokine secretion in mixed lymphocyte reactions (MLR) unveiled a strong reduction of allostimulatory capacity of mature but also of immature MoDC from MDS patients. Immature MoDC from MDS patients exhibited an almost normal immunophenotype, but secreted substantially less IL-12 and more IL-10 in response to LPS/IFN-gamma than normal controls. Terminal addition of TNF-alpha to GM-CSF/IL-4 treated monocytes failed to extinguish cytokine production by MDS MoDC and failed to induce the expected membrane upregulation of costimulatory and other ligands as in normal controls. While our data provide further support for previous studies that have indicated an impaired differentiation of immature towards mature MoDC, they also clearly demonstrate a qualitatively and quantitatively altered cytokine secretion at the level of immature MoDC, which may in part explain the reduced allostimulatory capacity of these cells. These alterations may contribute to immune modulation of the clinical phenotype of marrow failure in MDS, and may have to be considered when designing DC-based immunotherapeutic strategies for MDS.

The molecular signature of MDS stem cells supports a stem-cell origin of 5q myelodysplastic syndromes

Global gene expression profiling of highly purified 5q-deleted CD34+CD38(-)Thy1+ cells in 5q- myelodysplastic syndromes (MDSs) supported that they might originate from and outcompete normal CD34+CD38(-)Thy1+ hematopoietic stem cells. Few but distinct differences in gene expression distinguished MDS and normal stem cells. Expression of BMI1, encoding a critical regulator of self-renewal, was up-regulated in 5q- stem cells. Whereas multiple previous MDS genetic screens failed to identify altered expression of the gene encoding the myeloid transcription factor CEBPA, stage-specific and extensive down-regulation of CEBPA was specifically observed in MDS progenitors. These studies establish the importance of molecular characterization of distinct stages of cancer stem and progenitor cells to enhance the resolution of stage-specific dysregulated gene expression.

Lenalidomide inhibits the malignant clone and up-regulates the SPARC gene mapping to the commonly deleted region in 5q- syndrome patients

Myelodysplastic syndromes (MDSs) are a group of hematopoietic stem cell disorders characterized by ineffective hematopoiesis and peripheral blood cytopenias. Lenalidomide has dramatic therapeutic effects in patients with low-risk MDS and a chromosome 5q31 deletion, resulting in complete cytogenetic remission in >60% of patients. The molecular basis of this remarkable drug response is unknown. To gain insight into the molecular targets of lenalidomide we investigated its in vitro effects on growth, maturation, and global gene expression in isolated erythroblast cultures from MDS patients with del(5)(q31). Lenalidomide inhibited growth of differentiating del(5q) erythroblasts but did not affect cytogenetically normal cells. Moreover, lenalidomide significantly influenced the pattern of gene expression in del(5q) intermediate erythroblasts, with the VSIG4, PPIC, TPBG, activin A, and SPARC genes up-regulated by >2-fold in all samples and many genes involved in erythropoiesis, including HBA2, GYPA, and KLF1, down-regulated in most samples. Activin A, one of the most significant differentially expressed genes between lenalidomide-treated cells from MDS patients and healthy controls, has pleiotropic functions, including apoptosis of hematopoietic cells. Up-regulation and increased protein expression of the tumor suppressor gene SPARC is of particular interest because it is antiproliferative, antiadhesive, and antiangiogenic and is located at 5q31-q32, within the commonly deleted region in MDS 5q- syndrome. We conclude that lenalidomide inhibits growth of del(5q) erythroid progenitors and that the up-regulation of SPARC and activin A may underlie the potent effects of lenalidomide in MDS with del(5)(q31). SPARC may play a role in the pathogenesis of the 5q- syndrome.

Classification of chronic myeloid disorders: From Dameshek towards a semi-molecular system

Hematological malignancies are phenotypically organized into lymphoid and myeloid disorders, although such a distinction might not be precise from the standpoint of lineage clonality. In turn, myeloid malignancies are broadly categorized into either acute myeloid leukemia (AML) or chronic myeloid disorder (CMD), depending on the presence or absence, respectively, of AML-defining cytomorphologic and cytogenetic features. The CMD are traditionally classified by their morphologic appearances into discrete clinicopathologic entities based primarily on subjective technologies. It has now become evident that most CMD represent clonal stem cell processes where the primary oncogenic event has been characterized in certain instances; Bcr/Abl in chronic myeloid leukemia, FIP1L1-PDGFRA or c-kit(D816V) in systemic mastocytosis, rearrangements of PDGFRB in chronic eosinophilic leukemia, and rearrangements of FGFR1 in stem cell leukemia/lymphoma syndrome. In addition, Bcr/Abl-negative classic myeloproliferative disorders are characterized by recurrent JAK2(V617F) mutations, whereas other mutations affecting the RAS signaling pathway molecules have been associated with juvenile myelomonocytic leukemia. Such progress is paving the way for a transition from a histologic to a semi-molecular classification system that preserves conventional terminology, while incorporating new information on molecular pathogenesis.

Delineation by molecular cytogenetics of 5q deletion breakpoints in myelodyplastic syndromes and acute myeloid leukemia

Deletions of 5q in myelodysplastic syndromes (MDS) and acute myeloid leukemia (AML) are of different extents and the majority map to sub-bands 5q13.3 and 5q33.1. To further pinpoint these deletions, we have performed a detailed interphase fluorescence in situ hybridization (I-FISH) analysis with precisely mapped BAC probes. Eleven MDS and two AML patients with a sole cytogenetically visible del(5q) were studied. The proximal deletion endpoints were localized between 75 and 86 megabases (Mb) (5q13, five times), 86 and 96 Mb (5q14 approximately q15, four times), and at various sites in the other four. The distal breakpoints mapped between 153 and 155 Mb (5q33.2, five times), 156 and 158 Mb (5q33.3, three times), 158 and 164 Mb (5q34, two times), and 164 and 181 Mb (telomere) in three. The largest deletion was approximately 70 Mb and the smallest was 43 Mb. These studies show that cytogenetically similar appearing deletions in 5q are highly variable in molecular terms. We also found that in MDS cases with a blast count between 0 and 13%, cells with a del(5q) were present in 24-90% of interphase (nondividing) cells and in 30-100% of metaphase (dividing) cells. In the two AML patients with a blast count of 30 and 80%, del(5q) was found in 35 and 95% interphase cells and 95 and 100% of metaphase cells, respectively. This demonstrates that a low blast count can be associated with a high proportion of 5q- cells in the bone marrow.

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.

Circulating myeloid and lymphoid precursor dendritic cells are clonally involved in myelodysplastic syndromes

Circulating myeloid and lymphoid precursor dendritic cell (pDC) counts were determined in peripheral blood from 22 patients with myelodysplastic syndromes (MDS) by a single-platform flow cytometric protocol. The absolute count of myeloid and lymphoid pDC, as well as their relative number (as proportion of mononuclear cells or total leukocytes) was significantly lower in MDS (n=22) than in healthy controls (n=41). In 11 patients with chromosomal aberrations, purified pDC were examined by interphase fluorescence in situ hybridization. This revealed clonal involvement of myeloid as well as lymphoid pDC in all of them. These data therefore strongly suggest that myeloid and lymphoid pDC share a common precursor. Whether reduced peripheral blood counts of pDC contribute to the immunological abnormalities observed in MDS remains to be investigated.

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.

Monitoring treatment efficiency in MDS at the molecular level; possibilities now and in the future

Myelodysplastic syndromes (MDS) are a heterogeneous group of bone marrow (BM) diseases. MDS patients suffer from bone marrow failure because of the expansion of a malignant clone, resulting in abnormal differentiation of blood cells and severe pancytopenias. MDS patients have a high propensity for the development of acute myeloid leukemia (AML). During the last few years it has become increasingly clear that MDS is a stem cell disease. Two methods have generally been used to study the clonal origin of MDS bone marrow cells. First, the combination of fluorescent in situ hybridization (FISH) in combination with cell sorting has been used to study MDS specific numerical chromosomal aberrations in various cell types. Secondly, the determination of the X-chromosome inactivation patterns (XCIP) in different cell types of female MDS patients has been used to study clonality irrespective of the presence of a disease-specific marker. Both techniques have also been used to monitor treatment efficiency. Both methods showed that a molecular remission occurred in approximately half of the patients who achieved complete clinical remission after intensive antileukemic treatment, depending on the study and the type of treatment. In case of cytogenetic analysis this proved to be of prognostic significance. This review discusses the advantages and disadvantages of both techniques for the determination of clonality at diagnosis as well as for the assessment of treatment efficiency in past and in ongoing clinical trials. Future directions and possibilities for further research are also discussed.

Increased apoptosis in bone marrow B lymphocytes but not T lymphocytes in myelodysplastic syndrome

The hallmark of myelodysplastic syndrome (MDS) is enhanced apoptosis in myeloid, erythroid, and megakaryocytic cells in the bone marrow leading to ineffective hematopoiesis. Recent studies suggested that immunological and microenvironmental factors play a role in the pathophysiology of this disease. We report a significant increase in apoptosis in bone marrow B lymphocytes in MDS as compared to that found in acute myeloid leukemia and healthy controls. Furthermore, we demonstrate that patients with refractory anemia with excess blasts in transformation (RAEB-T) had apoptosis levels in lymphocytes similar to those seen in other subtypes of MDS. Our findings suggest that the alterations in B lymphocytes in the form of increased apoptosis can be seen in MDS and support the concept that immune modulation plays a role in the pathophysiology of MDS.

Wilms tumor gene peptide-based immunotherapy for patients with overt leukemia from myelodysplastic syndrome (MDS) or MDS with myelofibrosis

The Wilms tumor gene, WT1, is overexpressed not only in leukemias and myelodysplastic syndrome (MDS) but also in various types of solid tumors, including lung and breast cancer, and the WT1 protein is a tumor antigen for these malignancies. In clinical trials of WT1 peptide-based cancer immunotherapy, patients with overt leukemia from MDS or MDS with myelofibrosis were injected intradermally with 0.3 mg of an HLA-A*2402-restricted, 9-mer WT1 peptide emulsified with Montanide ISA51 adjuvant. Only a single dose of WT1 vaccination resulted in an increase in WT1-specific cytotoxic T-lymphocytes, which was followed by a rapid reduction in leukemic blast cells. Severe leukopenia and local erythema at the injection sites of WT1 peptide were observed as adverse effects. These results have provided us with the first clinical evidence suggesting that WT1 peptide-based immunotherapy is an attractive treatment for patients with leukemias or MDS.

Fluorescence in situ hybridization for the study of cell lineage involvement in myelodysplastic syndromes with chromosome 5 anomalies

Fluorescence in situ hybridization (FISH) with a locus-specific dual DNA probe (LSI EGR-1SO/D5S23SG) for chromosome 5 was used in combination with morphology to study bone marrow cell lineage involvement of the abnormal chromosomal clone in 13 patients with deletion 5q [del(5q)], either as a sole aberration or as part of a complex karyotype, and in six cases with monosomy 5 by metaphase cytogenetics, all with complex karyotypes including 2-6 marker chromosomes. In the monosomy 5 group, only one case displayed the expected one orange and one green (1O + 1G) FISH pattern in a majority of the cells. The other five patients instead showed 1O + 2G FISH signals in 17-86% of the bone marrow cells, which is the typical pattern for del(5q). In the del(5q) group, 26-98% of the bone marrow cells exhibited 1O + 2G FISH signals. All patients showed clonal involvement of the myeloid cell lineages, including the megakaryocytes in a few cases, whereas lymphoid cells generally exhibited the normal 2O + 2G FISH pattern. No difference was seen between patients with 5q- syndrome, those with del(5q) and a complex karyotype, and the monosomy 5 group. We were thus unable to confirm the recent suggestion that B-cells are a part of the abnormal clone in MDS with del(5q). Furthermore, true monosomy 5 seems to be rare in MDS.

Involvement and functional impairment of the CD34(+)CD38(-)Thy-1(+) hematopoietic stem cell pool in myelodysplastic syndromes with trisomy 8

Clonality studies of mature cells suggest that the primary transformation event in myelodysplastic syndrome (MDS) most frequently occurs in a myeloid-restricted progenitor, a hypothesis supported by recent studies of purified CD34(+)Thy1(+) hematopoietic stem cells (HSCs) in cases with trisomy 8 (+8). In contrast, we recently demonstrated that a lymphomyeloid HSC is the target for transformation in MDS cases with del(5q), potentially reflecting heterogeneity within MDS. However, since +8 is known to frequently be a late event in the MDS transformation process, it remained a possibility that CD34(+)CD38(-)Thy1(+) HSC disomic for chromosome 8 might be part of the MDS clone. In the present studies, although a variable fraction of CD34(+)CD38(-)Thy1(+) cells were disomic for chromosome 8, they did not possess normal HSC activity in long-term cultures and nonobese diabetic-severe combined immunodeficiency (NOD-SCID) mice. Mixing experiments with normal CD34(+)CD38(-) cells suggested that this HSC deficiency was intrinsic and not mediated by indirect mechanisms. Furthermore, investigation of 4 MDS cases with combined del(5q) and +8 demonstrated that the +8 aberration was always secondary to del(5q). Whereas del(5q) invariably occurs in CD34(+)CD38(-)Thy-1(+) HSCs, the secondary +8 event might frequently arise in progeny of MDS HSCs. Thus, CD34(+)CD38(-)Thy1(+) HSCs are invariably part of the MDS clone also in +8 patients, and little HSC activity can be recovered from the CD34(+) CD38(-)Thy1(+) HSC. Finally, in advanced cases of MDS, the MDS reconstituting activity is exclusively derived from the minor CD34(+)CD38(-) HSC population, demonstrating that MDS stem cells have a similar phenotype as normal HSCs, potentially complicating the development of autologous transplantation for MDS.

Molecular, cytogenetic and genetic abnormalities in MDS and secondary AML

Myelodysplasia (MDS) is a clonal disease, which increases with age, suggesting that multiple steps are required for the evolution of the condition. Approximately 30% of MDS evolve into acute myelogenous leukemia (AML). In this review, we intend to delineate the genetic events, which may drive this sequence and therefore we will focus primarily on cytogenetic abnormalities where the genes have been identified and oncogenes and suppressor genes that have been implicated. In terms of the biological mechanisms, which characterise this process, it is generally thought that the MDS cell has impaired differentiation, and has increased apoptosis. As the disease progresses in addition, the cells have increased proliferation. As the disease evolves, the population of cells, which predominate remain immature, have decreased apoptosis and in many cases, upregulate anti-apoptotic genes and have deregulated proliferation as the number of blast cells increase. Etiological factors, which contribute to the development of leukemia, include therapeutic agents administered for a primary malignancy. The cytogenetic abnormalities, predisposition factors and genes involved in secondary leukemia will also be reviewed.

Evolutionary conservation of zebrafish linkage group 14 with frequently deleted regions of human chromosome 5 in myeloid malignancies

Recurring interstitial loss of all or part of the long arm of chromosome 5, del(5q), is a hallmark of myelodysplastic syndrome and acute myeloid leukemia. Although the genes affected by these changes have not been identified, two critically deleted regions (CDRs) are well established. We have identified 76 zebrafish cDNAs orthologous to genes located in these 5q CDRs. Radiation hybrid mapping revealed that 33 of the 76 zebrafish orthologs are clustered in a genomic region on linkage group 14 (LG14). Fifteen others are located on LG21, and two on LG10. Although there are large blocks of conserved syntenies, the gene order between human and zebrafish is extensively inverted and transposed. Thus, intrachromosomal rearrangements and inversions appear to have occurred more frequently than translocations during evolution from a common chordate ancestor. Interestingly, of the 33 orthologs located on LG14, three have duplicates on LG21, suggesting that the duplication event occurred early in the evolution of teleosts. Murine orthologs of human 5q CDR genes are distributed among three chromosomes, 18, 11, and 13. The order of genes within the three syntenic mouse chromosomes appears to be more colinear with the human order, suggesting that translocations occurred more frequently than inversions during mammalian evolution. Our comparative map should enhance understanding of the evolution of the del(5q) chromosomal region. Mutant fish harboring deletions affecting the 5q CDR syntenic region may provide useful animal models for investigating the pathogenesis of myelodysplastic syndrome and acute myeloid leukemia.

Molecular cytogenetics

Refinements in cytogenetic techniques over the past 30 years have allowed the increasingly sensitive detection of chromosome abnormalities in haematological malignancies. In particular, the advent of fluorescence in situ hybridization techniques has provided significant advances in both diagnosis and research of leukaemias. The application of new multicolour karyotyping techniques has allowed the complete dissection of complex chromosome rearrangements and provides the prospect of identifying new recurrent chromosome rearrangements. Both comparative genomic hybridization and interphase fluorescence in situ hybridization avoid the use of metaphase chromosomes altogether and have allowed the genetic analysis of previously intractable targets. Recent developments in comparative genomic hybridization to DNA microarrays provide the promise of high resolution and automated screening for chromosomal imbalances. Rather than replacing conventional cytogenetics, however, these techniques have extended the range of cytogenetic analyses when applied in a complementary fashion.

Clonality in the myelodysplastic syndromes

The myelodysplastic syndromes (MDSs) comprise a heterogeneous group of stem cell disorders involving cytopenia and dysplastic changes in 3 hematopoietic lineages. Although it is accepted that MDS is a clonal disorder, the exact nature of the involvement of multipotent stem cells and progenitor cells has not been resolved. Most clonality studies of MDS support the proposal that the primary neoplastic event occurs, in most patients, at the level of a committed myeloid progenitor cell, capable of differentiation into multiple myeloid lineages. The extent of the involvement of T and B lymphocytes in MDS remains controversial. Much of the variation reported may result from disease heterogeneity and technical issues such as skewed methylation patterns occurring in studies analyzing X-chromosome inactivation patterns (XCIP) and possible impurities in lymphocyte preparation. A great deal of the evidence in support of T-lymphocyte involvement in MDS has been generated by XCIP studies, and some of these data need to be treated with caution, especially data from studies in which appropriate controls were omitted. In contrast, B-lymphocyte involvement in some patients with MDS is based on studies using more robust technology including combined immunophenotyping and fluorescence in situ hybridization. Clonality studies involving myeloid and lymphoid cells in MDS have yielded discrepant results with regard to the potential involvement of multipotent (lympho-myeloid) hematopoietic stem cells (HSCs). However, failure to detect a clonal marker in all cells of all lineages does not preclude multipotent-HSC involvement. Some recent studies have produced compelling evidence to show that, in some patients with MDS, the multipotent HSC is the target of the primary neoplastic event. It now seems probable that MDS arises in multipotent HSCs more commonly than previously recognized. Such data not only provide important new insights into the biology of MDS but also may have therapeutic implications. The determination of whether multipotent HSCs are involved in the MDS clone may be important for the use of autologous stem cell transplantation in these patients.