Molecular definition of interstitial deletions of chromosome 13 in leukemic cells

MicroRNA-140-5p inhibits cell proliferation, migration and promotes cell apoptosis in gastric cancer through the negative regulation of THY1-mediated Notch signaling

Studies have highlighted the importance of microRNAs (miRs) in the development of various cancers, including gastric cancer (GC), a commonly occurring malignancy, accompanied by high recurrence and metastasis rate. The aim of the current study was to investigate the role of miR-140-5p in GC. Microarray expression profiles were initially employed to screen the differentially expressed gene related to GC, and the miR regulating the gene was predicted accordingly. The data obtained indicated that thymus cell antigen 1 (THY1) was differentially expressed in GC and confirmed to be a target gene of miR-140-5p. Poorly expressed miR-140-5p and highly expressed THY1 were observed in the GC tissues. SGC-7901 cells were treated with miR-140-5p mimic/inhibitor, siRNA against THY1 and siRNA against Notch1 in order to determine their regulatory roles in GC cell activities. The relationship of miR-140-5p, THY1 and the Notch signaling pathway was subsequently identified. Moreover, cell proliferation, migration, invasion and apoptosis were determined using 3-(4,5-dimethylthiazol-2-yl)-5(3-carboxymethonyphenol)-2-(4-sulfophenyl)-2H-tetrazolium (MTS), wound-healing, transwell assay and flow cytometry, respectively. The overexpression of miR-140-5p and silencing of THY1 resulted in a diminished expression of the Notch signaling pathway-related proteins, as well as inhibited proliferation, migration and invasion of GC cells, enhanced expression of pro-apoptotic proteins in addition to elevated apoptosis rate. Taken together, the present study suggests that miR-140-5p directly targets and negatively regulates THY1 expression and inhibits activation of the Notch signaling pathway, whereby the up-regulation of miR-140-5p inhibits development of GC, highlighting the promise of miR-140-5p as a potential target for GC treatment.

From cellular morphology to molecular and epigenetic anomalies of myelodysplastic syndromes

Myelodysplastic syndromes (MDSs) are a myeloid neoplasm with a propensity for natural evolution or transformation to acute leukemias (AL) over time. Mechanisms for MDS transformation to AL remain poorly understood but are related to genomic instability, which affects the production of the different cell lineages. Genomic instability is also generated by dysfunctional telomeres. Indeed telomeres, the protective ends of chromosomes are the backbone of genome stability. Nuclear telomere remodeling is an early indicator of nuclear remodeling preceding the onset of genomic instability and MDS. This review aims to revisit the pathogenesis and pathophysiology of MDS from morphology and cytogenetics to molecular and epigenetic mechanisms. Furthermore, this review will highlight and discuss recent breakthroughs in dysfunctional telomeres and nuclear telomere architecture roles in the pathogenesis and physiopathology of MDS in the global context of genomic instability.

Rare cytogenetic abnormalities in myelodysplastic syndromes

The karyotype represents one of the main cornerstones for the International Prognostic Scoring System (IPSS) and the revised IPSS-R (IPSS-R) that are most widely used for prognostication in patients with myelodysplastic syndromes (MDS). The most frequent cytogenetic abnormalities in MDS, i.e. del(5q), -7/del(7q), +8, complex karyotypes, or -Y have been extensively explored for their prognostic impact. The IPSS-R also considers some less frequent abnormalities such as del(11q), isochromosome 17, +19, or 3q abnormalities. However, more than 600 different cytogenetic categories had been identified in a previous MDS study. This review aims to focus interest on selected rare cytogenetic abnormalities in patients with MDS. Examples are numerical gains of the chromosomes 11 (indicating rapid progression), of chromosome 14 or 14q (prognostically intermediate to favorable), -X (in females, with an intermediate prognosis), or numerical abnormalities of chromosome 21. Structural abnormalities are also considered, e.g. del(13q) that is associated with bone marrow failure syndromes and favorable response to immunosuppressive therapy. These and other rare cytogenetic abnormalities should be integrated into existing prognostication systems such as the IPSS-R. However, due to the very low number of cases, this is clearly dependent on international collaboration. Hopefully, this article will help to inaugurate this process.

Gains on 9p are common genomic aberrations in idiopathic myelofibrosis: a comparative genomic hybridization study

Ideopathic myelofibrosis (IMF) is a chronic myeloproliferative disorder resulting in bone marrow fibrosis as a consequence of growth factor release from clonal haematopoiesis. Conventional cytogenetic analysis identifies abnormalities in approximately a third of cases at diagnosis, although rarely uncovers unique, primary genetic events. We have used comparative genomic hybridization (CGH) to study 25 IMF cases and have compared the results with conventional cytogenetics. Metaphase cells were available for analysis in 13 cases, of which seven showed an abnormal karyotype. CGH chromosomal profiles showed imbalances in 21 of 25 cases. The most frequent aberrations were gains of 9p (12 cases), 2q (seven cases), 3p (seven cases), chromosome 4 (seven cases), 12q (seven cases), 13q (eight cases). The main losses were at 17q and occurred in six cases. The results for CGH and cytogenetics were matched for one case only. Investigation of IMF by CGH suggests that genomic aberrations are much more common than has been previously indicated by conventional cytogenetic analysis and occur in the majority of cases. Gains of 9p were the most frequent finding, occurring in 50% of patients and suggests that genes on 9p may play a crucial role in the pathogenesis of IMF.

Cytogenetic findings in adult de novo acute myeloid leukaemia. A population-based study of 303/337 patients

During a 10-year period (1992-2001) in the region of Southern Denmark, 337 patients aged 15 years or older (range 16-93 years, median 67 years) were diagnosed with acute myeloid leukaemia (AML). Cytogenetic analysis was carried out in 90%, of whom 53% had clonal chromosome aberrations. Some 24% and 31% had only numerical or structural abnormalities respectively. The remaining patients showed both types of abnormalities. Ploidy levels in decreasing order were: pseudodiploidy, 41%; hyperdiploidy, 32%; and hypodiploidy, 27%. Pseudodiploidy characterizes type M3 (70%) and hypodiploidy M6 (56%). Recurrent cytogenetic abnormalities--t(8;21), t(15;17) and inv(16)--were found in 3.3%, 3.3% and 2.0% of all patients respectively. Prognostically intermediate and adverse aberrations were found in 39% and 44%, respectively, of those with an abnormal karyotype. Rare recurrent aberrations were found in two patients in this material. A previously described non-recurrent abnormality was found to be recurrent in one patient [der(20)t(11;20)(q13.2;p13)]. New, previously undescribed abnormalities were found in 41 patients. Statistically significant correlations were found between t(15;17) and young age (P < 0.001), inv(16) and young age (P < 0.006), -17 and M6 (P = 0.007), and M6 and complex karyotype with five or more unrelated aberrations (P = 0.004). We conclude that this truly population-based cytogenetic study of adult AML showed distributions of chromosome abnormalities that differ from those described so far.

One allele deletion of the RB1 gene in a case of refractory anemia with del(13)(q12q14): a fluorescence in situ hybridization study of the RB1 gene

The tumor suppressor gene RB1 is known to be located on chromosome band 13q14. We investigated the involvement of the RB1 gene in a case of refractory anemia with del(13)(q12q14) by florescence in situ hybridization (FISH) analysis using the RB1 locus (13q14) DNA probe. Bone marrow cells derived from this patient exhibited a single signal of the RB1 gene in 58 of 100 bone marrow cells, as determined by interphase FISH analysis. Hematopoietic colony-forming assays showed that the absolute number of erythroid, myeloid, and mixed colonies was comparable to that of normal subjects. FISH analysis of selected colonies revealed that only a single signal for the RB1 gene was detected in five of five granulocyte macrophage-colony-forming units (CFUs), four of five erythroid burst-forming units, and two of four mixed CFUs (total 11/14: 78.6%). Thus, the majority of hematopoietic progenitor cells lacked one allele of the RB1 gene, suggesting that in this particular case the RB1 gene played an important role in abnormal hematopoiesis.

Mutational analysis of class III receptor tyrosine kinases (C-KIT, C-FMS, FLT3) in idiopathic myelofibrosis

Genomic DNA from patients with idiopathic myelofibrosis (IMF) was screened by polymerase chain reaction (PCR) and conformation sensitive gel electrophoresis (CSGE) for mutations in the C-KIT gene (60 patients), as well as the C-FMS and FLT3 genes (40 patients). Intronic primers were used to amplify the entire coding region of both the C-KIT and C-FMS genes, and selected regions of the FLT3 gene. CSGE and direct DNA sequencing detected all previously reported as well as several novel polymorphisms in each of the genes. A novel c-fms exon 9 mutation (Gly413Ser) was detected in two patients. Its functional significance remains to be determined. The c-kit mutation Asp52Asn, previously described in two of six IMF patients in Japan, was not detected in this study. In addition, the reported c-fms mutations involving codons 301 and 969 were not identified. Therefore, in contrast to acute myeloid leukaemia, mutations in RTKs class III do not appear to play a significant pathogenetic role in idiopathic myelofibrosis.

Frequency of structural abnormalities of the long arm of chromosome 12 in myelofibrosis with myeloid metaplasia

Among cytogenetic studies of 205 patients diagnosed as myelofibrosis with myeloid metaplasia, we found seven cases with structural abnormalities of the long arm of chromosome 12. The karyotype showed six balanced translocations, that is, t(4;12)(q33;q21), t(5;12)(p14;q21), t(1;12)(q22;q24), t(12;17)(q24;q11), t(7;12) (p11;q24), and t(1;12)(p12;q24), as well as other cytogenetic abnormalities such as del(12)(q21;q24) and inv(12) (p12q24). Some isolated cases involving the 12q21 region have also been described in the literature. Importance of rearrangement of chromosome 12 in 12q21 or 12q24 is underlined by the authors suggesting a proto-oncogene accountable mechanism of leukemogenesis.

Pathogenesis and management of idiopathic myelofibrosis

Idiopathic myelofibrosis is the least common and carries the worst prognosis of the chronic myeloproliferative disorders. The primary disease process is a clonal haematopoietic stem cell disorder which results in a chronic myeloproliferation and an atypical megakaryocyte hyperplasia. In contrast, the characteristic stromal proliferation is a reactive phenomenon, resulting from the inappropriate release of megakaryocyte/platelet-derived growth factors, including PDGF, TGF-beta bFGF and calmodulin. The median survival is approximately 4 years, although individual survival varies greatly. A variety of prognostic schema have been developed which enable the identification of high-risk patients, for whom bone marrow transplantation should be considered. Management for the majority of patients, however, is directed towards the alleviation of symptoms and improvement in quality of life. This review summarizes the recent advances in our understanding of the disease's pathogenesis and discusses the limited therapeutic options available to clinicians.

Detection of RB1 deletions by fluorescence in situ hybridization in malignant hematologic disorders

We evaluated the usefulness of fluorescence in situ hybridization (FISH) using different-colored commercial RB1 and 13qter DNA probes to identify RB1 deletions in interphase nuclei of bone marrow from 24 patients with agnogenic myeloid metaplasia (AMM), 20 patients with multiple myeloma (MM), 21 patients with other hematologic malignancies, and 25 normal bone marrow transplant (BMT) donors. Based on the 25 normal BMT donors, the upper boundary for the normal percentage of nuclei with one RB1 signal was 6.5%. Based on eight specimens known to have a deletion of 13q14 by cytogenetic studies, the lower limit of abnormal for the percentage of nuclei with one RB1 signal was 12.5%. More than 12.5% of nuclei had a single RB1 signal in 7/24 (29%) patients with AMM and 3/20 (15%) patients with MM. None of the 21 patients with hematologic malignancies other than AMM or MM had more than 12.5% nuclei with loss of RB1. The results of this study suggest that FISH with RB1 probes is useful to detect loss of RB1 in interphase nuclei from patients with hematologic disorders who have chromosome abnormalities involving 13q14. Thus, FISH with probes for RB1 is efficacious to investigate the pathogenesis of RB1 in malignant neoplasms and is a useful adjunct to conventional cytogenetic studies in clinical practice when abnormalities of 13q14 are involved.

Molecular Delineation of 13q Deletion Boundaries in 20 Patients With Myeloid Malignancies

Fluorescent in situ hybridization (FISH) analysis with a panel of DNA probes for 13q13.1-q14.3 was performed on 20 cases of myeloid malignancies, of which 17 showed a del(13)(q) and three had translocations affecting 13q. By chromosome morphology, deletions consistently involved bands q14 and q21. In addition to confirming the chromosome data, FISH allowed us to delineate a commonly deleted region that was flanked by YAC 833A2 and YAC 854D4. Three cases with 13q translocations unexpectedly showed accompanying cryptic microdeletions of 13q, and in one case the commonly deleted region could be narrowed to a genomic segment, which includes YAC 937C7, RB1, and YAC 745E3. Homozygous deletions were not detected. This region overlaps with the smallest deleted region of 13q14 in chronic lymphocytic leukemia.

Molecular Delineation of 13q Deletion Boundaries in 20 Patients With Myeloid Malignancies

Fluorescent in situ hybridization (FISH) analysis with a panel of DNA probes for 13q13.1-q14.3 was performed on 20 cases of myeloid malignancies, of which 17 showed a del(13)(q) and three had translocations affecting 13q. By chromosome morphology, deletions consistently involved bands q14 and q21. In addition to confirming the chromosome data, FISH allowed us to delineate a commonly deleted region that was flanked by YAC 833A2 and YAC 854D4. Three cases with 13q translocations unexpectedly showed accompanying cryptic microdeletions of 13q, and in one case the commonly deleted region could be narrowed to a genomic segment, which includes YAC 937C7, RB1, and YAC 745E3. Homozygous deletions were not detected. This region overlaps with the smallest deleted region of 13q14 in chronic lymphocytic leukemia.

Idiopathic myelofibrosis: pathogenesis, natural history and management

Idiopathic myelofibrosis is a chronic myeloproliferative disorder characterized by bone marrow fibrosis, extramedullary haematopoiesis and a leucoerythroblastic blood picture. The marrow fibrosis results from an increased deposition of various interstitial and basement membrane glycoproteins, including collagen types I, III, IV, V and VI, fibronectin, vitronectin, laminin and tenascin. In addition, a marked neovascularization is present, even in the early proliferative phase of the disease. In contrast to the clonal haematopoiesis, the increased bone marrow stromal tissue is thought to be a reactive phenomenon, resulting from the inappropriate release of megakaryocyte/platelet-derived growth factors, including PDGF, TGF-beta, EGF, bFGF and calmodulin. Recent cytogenetic studies have highlighted three defects, namely del(13q), del(20q) and partial trisomy 1q, that account for nearly 70% of all abnormalities at diagnosis, and suggests that in many patients gene loss and/or inactivation may be an important pathogenetic mechanism. The median survival is approximately 4 years, although individual survival varies greatly. Prognostic schema enable the identification of patients with a limited life expectancy, for whom bone marrow transplantation should be considered. However, for the majority of patients therapy is supportive and consists of blood transfusions, androgens to sustain erythropoiesis, cytoreductive agents to prevent thrombocythaemia and, in carefully selected cases, splenectomy. The role for a number of experimental therapies, such as vitamin D3 analogues, alpha and gamma interferons and erythropoietin has yet to be defined.

Genetic analysis of chromosome 13 deletions in BCR/ABL negative chronic myeloproliferative disorders

Chromosomal deletions of band 13q14 occur recurrently in BCR/ABL negative chronic myeloproliferative disorders (CMPD), including myelosclerosis with myeloid metaplasia (MMM), polycythemia vera (PV), essential thrombocythemia (ET), juvenile chronic myeloid leukemia (JCML), and the so-called BCR/ABL- chronic myeloid leukemia (CML). The RBI tumor suppressor locus, mapping to 13q14, has long since been hypothesized as the important gene. In this report, we have determined the frequency of 13q14 deletions at the molecular level in a large panel of BCR/ABL- CMPD at different disease stages and performed a detailed genetic analysis of gross rearrangements/deletions and point mutations of the RBI gene in these disorders. Our data show that molecular deletions of 13q14 are detected in a relatively large fraction of BCR/ABL- CMPD (38%), that they appear to be more frequent in MMM than in other BCR/ABL- CMPD, and that they may be present at diagnosis or occur during blastic evolution of the neoplasia. The RBI gene displayed a germline configuration in all BCR/ABL- CMPD tested, suggesting that 13q14 deletions in these disorders affect a tumor suppressor locus distinct from RBI.

Karyotypic and ras gene mutational analysis in idiopathic myelofibrosis

Karyotypic analysis was performed in a total of 69 patients with well-characterized idiopathic myelofibrosis. Karyotypic abnormalities were detected in 46% of cases examined during the chronic phase (29/63); with three abnormalities, del(13q), del(20q) and partial trisomy 1q, accounting for 75% of all abnormalities at diagnosis. The absence of del(5q), trisomy 8 and 21, as well as the rarity of monosomy 7, contrasts with pooled published data and may reflect our exclusion of closely related disorders, in particular MDS with fibrosis. Chromosomal aberrations increased to approximately 90% (8/9) in patients analysed during acute transformation. Mutational activation of codons 12, 13 and 61 of N-, Ha- and Ki-ras genes were assessed by polymerase chain reaction and hybridization with synthetic non-radioactive digoxigenin-labelled probes. Three mutations were detected in samples of peripheral blood DNA taken from 50 patients during the chronic phase of their disease: one N12 Asp (GGT-->GAT) and two N12 Ser (GGT-->AGT) mutations. The results from this study indicate that karyotypic abnormalities are present in at least 29% of cases at diagnosis and that del(13q), del(20q) and partial trisomy 1q are the most frequent findings. Ras mutations were relatively infrequent (6%) and appeared restricted to the N-ras gene. Karyotypic analysis at diagnosis was found to be of prognostic significance.

Molecular heterogeneity at the breakpoints of smaller 20q deletions

Deletions of the long arm of chromosome 20 [del(20q)] are recurring abnormalities in patients with myeloid disorders. Although variable in size, these deletions are usually interstitial. With the object of defining a commonly deleted region for smaller 20q deletions, we used quantitative Southern blot analysis complemented by restriction fragment length polymorphism (RFLP) analysis to determine the copy number at 15 loci spanning 20q. The proximal breakpoints of three such deletions were found to separate HCK and the growth hormone releasing factor (GHRF) locus near the centromeric boundary of band 20q11.2. The distal breakpoints were localized to the vicinity of the D20S22 locus in band q13.1. A candidate tumor suppressor gene, RBL2, and the SRC oncogene were both located within the commonly deleted region. Six loci in terminal region q13.2-q13.3 were conserved on these del(20q) chromosomes, thereby confirming that the deletions were interstitial. Molecular heterogeneity at one and possibly both deletion breakpoints rules out the pathological involvement of loci at these sites. Instead, loss of a tumor suppressor locus from within the commonly deleted region may contribute to deregulated hemopoiesis.

Cytogenetic deletion maps of hematologic neoplasms: circumstantial evidence for tumor suppressor loci

Research in oncogenetics has led to the identification of two major classes of tumor-associated genes, oncogenes and tumor suppressor genes. In a wide variety of solid tumor types, mutations of both groups of genes have been implicated in the tumorigenic process. In hematologic neoplasms, on the other hand, most attention has focused on illegitimate activation of oncogenes, e.g., deregulation leading to disturbed transcriptional activity and structural rearrangements resulting in hybrid genes. Whether loss or mutational inactivation of tumor suppressor genes also plays an essential role in the genesis of tumors of the hematopoietic system has received less attention. Because such inactivation can be the result of karyotypically detectable loss of chromosomal material, cytogenetic studies may prove helpful in pinpointing genomic sites that harbor tumor suppressor genes. The present study is based on a total of 12,473 cytogenetically abnormal hematologic neoplasms reported in the literature to date. Among these, we selected the 6,422 cases with sole clonal chromosomal abnormalities in order to include only aberrations of importance in the genesis, rather than in the progression, of these neoplasms. All tumors with monosomies or structural abnormalities resulting in loss of chromosomal material were compiled, and for every such structural aberration, i.e., deletion, unbalanced translocation, isochromosome, and ring chromosome, the chromosome bands lost were ascertained. This cytogenetic deletion mapping revealed that the most commonly lost chromosomes were Y and 7 in acute myeloid leukemia (AML), myelodysplastic syndromes (MDS), and chronic myeloproliferative disorders (MPD); X, Y, 7, 20, and 21 in acute lymphocytic leukemia (ALL); X, Y, and 17 in chronic lymphoproliferative disorders (LPD); and X and Y in non-Hodgkin's lymphoma (NHL). Chromosome segments/bands lost due to unbalanced structural abnormalities in at least 5% of the cases were 5q13-33, 7q22-36, 9q13-31, 11q23-25, 12p12-13, 17p11-13, and 20q11-13 in AML; 5q13-35 and 20q11-13 in MDS; 5q22-23, 7q22, 13q12-22, 17p11-13, and 20q11-13 in MPD; 6q15-27, 9p11-24, 12p12-13, and 19p13 in ALL; 6q16-27, 11q21-25, 13q13-14, and 14q32 in LPD; and 6q21-27, 11q13-25, and 14q24-32 in NHL. Based on these findings, three conclusions can be drawn. First, there is no good correspondence between total and partial monosomies, the only exception being -7 and 7q-, both of which are common in myeloid neoplasms. This indicates different pathogenetic effects of total and partial losses.(ABSTRACT TRUNCATED AT 400 WORDS)

Evidence for a new tumour suppressor locus (DBM) in human B-cell neoplasia telomeric to the retinoblastoma gene

Roughly 25% of human B-cell chronic lymphocytic leukaemias (CLL) are characterized by a chromosomal lesion involving 13q14. This region contains the retinoblastoma gene (RB1). We have used a variety of techniques to determine whether RB1 or some other locus is the critical region in 11 cases of low grade B-cell malignancy (mainly CLL), all with deletions or translocations involving 13q14. In all cases, except the one with minimal disease, there was deletion or a structural lesion in the region of D13S25, with at least 4 cases showing homozygous disruption. We conclude that D13S25 lies close to a tumour suppressor locus whose inactivation contributes to the initiation or progression of low grade B-cell malignancy. This locus is located at least 530 kilobases telomeric to RB1.