From www.bloodjournal.org by guest on February 6, 2015. For personal use only. Formation of a Hyperdiploid Karyotype in Childhood Acute Lymphoblastic Leukemia By Norio Onodera, Norah R. McCabe, and Charles M. Rubin Hyperdiploidy with 250 chromosomes is a frequent and distinct karyotypic pattern in the malignant cells of children with acute lymphoblastic leukemia. To understand better the mechanism of formation of the hyperdiploid karyotype, we studied 15 patients using 20 DNA probes that detect restriction fragment length polymorphisms. We first examined disomic chromosomes for loss of heterozygosity. Two patients had widespread loss of heterozygosity on all informative disomic chromosomes, and represent cases of nearhaploid leukemia in which the chromosomes doubled. One other patient had loss of heterozygosity limited t o chromosome 3; in this patient all of seven other informative disomic chromosomes retained heterozygosity. Loss of heterozygosity was not detected in the remaining 12 patients on a total of 87 informative disomic chromosomes. We then examined tetrasomic chromosomes for parental dosage. Of the 13 patients in whom widespread loss of heterozygosity was not present, 11 patients had tetrasomy 21; 10 of 11 (91%) had an equal dose of maternal and paternal alleles on chromosome 21 and only 1 of 11 (99’0) had an unequal dose of parental alleles in a 3:l ratio. These results suggest that the hyperdiploid karyotype usually arises by simultaneous gain of chromosomes from a diploid karyotype during a single abnormal cell division, and occasionally by doubling of chromosomes from a near-haploid karyotype. The hyperdiploidy in cases without widespread loss of heterozygosity is not caused by stepwise or sequential gains from a diploid karyotype or by losses from a tetraploid karyotype; the former should result in a 3 : l parental dosage for 67% of tetrasomic chromosomes (9% observed) and the latter should result in loss of heterozygosity for 33% of disomic chromosomes (1% observed). Additional studies of the molecular basis for this leukemia subtype are warranted. 0 1992by The American Society of Hematology. A tion of a chromosomal homologue containing a specific mutation that provides the cell with a proliferative advantage in a dose-dependent manner. This hypothesis invokes the presence of independent mutations on each of the affected chromosomes. Alternatively, a single mutation or a single carcinogenic event may lead to the hyperdiploid state as a secondary effect. Finally, a gene mutation may not be critical to the development of hyperdiploidy; instead, the gain of certain chromosomes may enhance proliferation of early lymphoid cells through a change in dosage or relative dosage of a set of genes. Here we report 15 patients with hyperdiploid ALL with > 50 chromosomes including two patients reported previ0us1y.~~ We used restriction fragment length polymorphisms to address the pathophysiology of the disease. We provide strong evidence to support the view that the hyperdiploid karyotype occurs as a sudden gain of multiple chromosomes. HYPERDIPLOID karyotype is observed in 23% to 42% of newly diagnosed children with acute lymphoblastic leukemia These patients are generally divided into two subgroups, namely, those with a chromosome number of 47 to 49 and those with >50 chromosomes. The hyperdiploidy 2 50 group has a nonrandom pattern of chromosomal gain. Nearly all of the patients have a chromosome number of 51 to 65 with a peak at 55.7 Frequently gained chromosomes (in more than half of the cases) are chromosomes 4, 6, 10, 14, 17, 18, 20, 21, and X, and rarely gained chromosomes (less than 10% of the cases) are chromosomes 1, 2, 3, 12, and 16.8Typically, the affected chromosomes are present in three copies (trisomic). However, chromosome 21, the most frequently gained ~ h r o m o s o m e , often ~ ~ 3 ~is~tetrasomks ~~ The presence of hyperdiploidy > 50 correlates strongly with good risk features, including age between 3 and 7 years old, white blood cell (WBC) count less than 10 X 109/L, French-American-British (FAB) Cooperative Group subtype L1,l and common ALL antigen (CALLA, CD10) positive early pre-B p h e n ~ t y p e .Patients ~ with hyperdiploidy 2 50 have the longest disease-free survival compared with any other cytogenetic group.1° Recently, we reported two cases of childhood ALL with hyperdiploidy > 50 in whom the hyperdiploid leukemic clone arose from a near-haploid clone through doubling of the chromosomes.ll We verified this mechanism by demonstration of widespread loss of heterozygosity on all disomic chromosomes (chromosomes present in two copies). However, in the majority of cases of hyperdiploid ALL, the mechanism leading to the increased number of chromosomes is unknown. Possibilities include development of tetraploidy with subsequent loss of chromosomes, gains of individual chromosomes in a stepwise or sequential fashion, or simultaneous gain of multiple chromosomes in a single abnormal cell division. Also, unknown is the biologic significance of hyperdiploidy to the leukemic process.12 The extra chromosomes may result from selection for cells undergoing nondisjuncBlood, Vol80, No 1 (July 1). 1992: pp 203-208 MATERIALS AND METHODS Patients. All patients were children with ALL and a hyperdiploid karyotype with 2 5 0 chromosomes. The patients were se- From the Depa rtments of Pediatiics and Medicine, University of Chicago, Chicago, IL; and the Children’s Medical Center, Iwate Prefectural Kitakami Hospital, Kitakami, Iwate, Japan. Submitted January IO, 1992; accepted March 3, 1992. Supported in part by Grant CA42557 (to Dr. Janet D. Rowley) from the National Institute of Health and Grant DE-FG02-86ER60408 (to Dr. Janet D. Rowley) from the Department of E n e w . C.M.R. is a Pew Scholar in the Biomedical Sciences. Address reprint requests to Charles M. Rubin, MD, Department of Pediatrics, University of Chicago, 5841 S Maryland Ave, MC 4060, Chicago, IL 60637. The publication costs of this article were defrayed in part by page charge payment. This article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. section I734 solely to indicate this fact. 0 1992 by The American Society of Hematology. 0006-4971I92 I8001 -0002$3.00 10 203 From www.bloodjournal.org by guest on February 6, 2015. For personal use only. ONODERA, McCABE, AND RUBIN 204 lected on the basis of availability of cryopreserved leukemic bone marrow containing 2 85% blasts. One patient (patient 6) had only 61% blasts in the leukemic sample. Features of the patients are shown in Table 1. Twelve patients were studied at diagnosis and three patients (patients 4, 6, and 10) were studied at relapse. Two patients (patients 2 and 6) were reported in a previous publication" and are investigated further in this study. Cytogenetic analysis. Cytogenetic analysiswas performed using a trypsin-Giemsa banding technique. Cells were obtained from bone marrow and/or peripheral blood before initiation of chemotherapy. Metaphase cells from direct preparations and/or shortterm (24 and 48 hours) unstimulated cultures were examined. Chromosomal abnormalities were described according to the International System for Human Cytogenetic N0menc1ature.l~ Molecular analysis. DNA was extracted from clyopreserved buRy coat cells from bone marrow at diagnosis or relapse of leukemia. In eight patients (patients 1, 2, 5, 6, 11, 12, 14, and 15) DNA was extracted from fresh mononuclear cells of peripheral blood or cryopreserved buRy coat cells from bone marrow during complete remission; this nonleukemic material represented constitutional DNA. Restriction endonuclease digestion, electrophoresis, Southern blotting, radiolabeling of probes, and DNA hybridization were performed according to standard procedures. Informative probes were those showing two different alleles. In patients in whom we did not have a sample of nonleukemic DNA, we could not distinguish between a noninformative probe and loss of heterozygositywhen only one polymorphicband was observed. Densitometry was used to quantify the intensity of bands on exposures of Southern blots. Densitometly was performed by transmittal of the image to a computer using a CCD camera CX-77 (SONY, Tokyo, Japan) and the program MacVision (Koala Technologies, Morgan Hill, CA). The image was analyzed further by the program Densitometly on a Disk (Amoco Corporation, Naperville, IL). When quantifying the intensity of bands for VNTR (variable number of tandem repeats) probes, a mathematical correction was made.14 The intensity of lower bands in the autoradiogram were corrected by the following formula: lower band intensity x upper band size/lower band size. Probes. The 20 probes used to detect DNA restriction fragment length polymorphismsare described in Tables 2 and 3. Additional information and references are listed in the report of the 10th International Workshop on Human Gene Mapping.15Probes p2.1, p21-4U, pG95-al-lla, and pPW228C were gifts from Drs Ellen Solomon, Gordon D. Stewart, Bradley N. White, and Integrated Genetics (Framingham, MA), respectively. Probes CRI-R59 and CRLL427 were purchased from Collaborative Research Inc (Bedford, MA). The remaining probes were obtained from the American Type Culture Collection (ATCC; Rockville, MD). Probes pMCT118, cYNA13, pYNH24, pTBAB5-7, pEFD64.1, pJCZ67, pMHZ10, pCMM6, and pMCT15 were deposited at ATCC by Drs Ray White and Yusuke Nakamura. Probes pCMW-1, p79-2-23, pGSH8, and 26C and p21.3 were deposited by Drs David Ledbetter, Michael Litt, Gordon D. Stewart, and A. Millington-Ward, respectively. RESULTS Karyoypes. The results of cytogenetic analyses are described in Table l. All 15 patients had one or more abnormal clones with 50 to 60 chromosomes. Thirteen patients had typical hyperdiploidy in which most of the affected chromosomes were present in three copies (trisomic), and two patients (patients 2 and 6) were atypical because nearly all affected chromosomes were tetrasomic. All 15 patients had extra copies of chromosomes 21 and X. Extra copies of chromosomes 4, 6, 10, 14, 17, and 18 were observed in more than 10 of the patients. Thirteen patients had tetrasomy 21 (patients 1 through 13). Some chromosomes were not gained in any of the cases including chromosomes 1, 2, 3, 7, 15, and 16; thus, these chromosomes were always disomic. Fourteen of 15 patients were disomic for chromosomes 9,11,13,19, and 20. Structural abnormalities were observed in five patients. Two patients (patients 3 and 9) had partial duplication of the long arm of chromosome 1, one patient (patient 10) had Table 1. Cytogenetic Studies of 15 PatientsWith ALL and a Hyperdiploid Karyotype Sex State of Disease No. of Metaphase Cells Examined 4 5 7 M F F Diagnosis Diagnosis Diagnosis 33 32 33 4 5 3 10 F F Relapse Diagnosis 31 22 6t 7 8 9 18 3 18 3 M M F M Relapse Diagnosis Diagnosis Diagnosis 21 12 22 20 10 9 M Relapse 21 11 12 13 14 15 1 2 3 2 2 M M M M M Diagnosis Diagnosis Diagnosis Diagnosis Diagnosis 12 13 19 11 26 Patient Age (yrs) 1 2' 3 *Reported as Patient 1 in reference 11. tReported as Patient 2 in reference 11. Karotypes 46,XY (85%)/56,XY,+X,+4,+5,+6,+ 14,+ 17,+ 18,+21,+21,+22 (15%) 46,XX (81%)/50,XX,+ 18, 18, 21, +21 (19%) 46,XX (18%)/54,XX,+X.+4,+6,+14,+17,+18,+21,+21 (6l%)/ 55,XX,+X,+4,+6,+ 14,+ 17,+ 18,+ 19,+21,+21 (12%)/ 56,XX,+X,+4,+6,+ lo,+ 14,+ 15,+ 17,+ 18,+21,+21, dup(l)(q21 + q44) (9%) 46,XX (3%)/56,XX,+X,+4,+6,+8,+10,+14,+18,+18,+21,+21 (97%) 46,XX (41%)/54,XX,+X,+4,+12,+14,+17,+18,+21,+21 (55%)/ 55,XX,+X,+4,+ 12,+ 13,+ 14,+ 17,+ 18,+21,+21 (4%) 46,XY (90%) 60,XY. +X,+Y,+5,+5,+8,+8,+9,+9,+14,+14,+19,+20,+21,+21 (10%) 46,XY (58%)/56,XY, +X, +Y,+4,+6,+ I O , 14,+ 17, 18, 21, 21 (42%) 46,XX (32%)/56,XX,+X,+4,+6,+10,+14,+17,+18,+21,+21,+mar(68%) 46,XY (30%)/55,XY,+X,+4,+6,+10,+14,+17,+18,+21,+21,d~p(1)(q21 + q32)(40%)/ 56,XY,+X,+Y,+4,+6,+10,+14,+17,+18,+21,+21,dup(1)(q21 + q32) (30%) 46,XY (81%)/55,XY,+X,+4,+5,+6,+14,+14,+17,+18,+12,+21,del(12)(p11p12),dic(21; 21)( pl3; p l 3 ) (19%) 46,XY (50%)/54,XY, +X,+6,+ 13, 14, 17,+ 18, 21, +21 (50%) 46,XY (46%)/60,XY,+X,+4,+5,+6,+8,+10,+11,+12,+14,+17,+18,+21,+21,+22 (54%) 53,XY,+X,+4,+6,+14,+21,+21,+1nar (100%) 46,XY (45%)/56,XY,+X,+4,+6.+8,+10,+14,+17,+18,+21,+22 (55%) 46,XY (88%)/53,XY,+X.+Y,+6,+14,+ 17,+ 18,+21 (12%) + + + + + + + + + From www.bloodjournal.org by guest on February 6, 2015. For personal use only. FORMATION OF A HYPERDIPLOID KARYOTYPE 205 Table 2 Analysh of DNA Polymorphhs on Dlsomk Chromosomes In 15 PatientsWith AU and a HyperdiploidKarotype Maintenanceor Loss of Heterozygosityin Leukemic DNA Probea Patient MaP Location Locus Symbol Name 1 2 3 4 5 6 IP lq 2P 2pterq32.3 3pter-p21 3q 7q 9q llp13-pl5 15pter-q13 16q24 2oq DlS80 DlS74 D2S47 D2S44 D3S12 D3S42 078396 D9Sll DllS150 D15S24 D16S7 D20S19 pMCTl18. cYNA13. pTBAB5-7. pYNH24' CRI-R59 pEFD64.1' pJCZ67. CMHZlO' ~2.1' pCMW-1. p79-2-23. pCMM6. M M M M M M NI L M M M M M M M L L L L L L NI T L NI L T M M M M M M - M L L NI L L L L L NI M M M M NI - NI M M M M - M M M M M M M M M M M M M M 7 8 9 - 1 0 - - M M M - M M M M M - - M M M M - - M M - M M M M 1 1 2 1 3 1 4 15 NI M NI M NI NI M M M M M M NI M M M L L M M M NI M M M M M M M M M NI M M M M M M NI M NI M NI M M M - - M M M M M - 1 M M M - M M M M NI M T M M M M M M M Abbreviations: M, maintenance of heterozygosity; L, loss of heterozygosity; NI, not informative; T, trisomic or tetrasomic, not evaluated; -, unknown because of lack of availability of constitutional nonleukemic DNA or not tested. VNTR probe. Table 3. Analysh of DNA Polymorphlrmson Chromosome 21 In 13 PatientsWith A U and a HyperdlploldKaryotwe Associated With Tetrasomy 21 Contributionof ParentalAllele8 Probes Patient Map Location Locus Symbol Name 1 2 3 4 21pte~q21.1 21qll 21q11.2-q21.2 21q11.2-q21.2 21q21.1-qter 21q22.1-q22.2 21q22.1-qter 21q22.3 D21S26 D21S110 D21S1 D21S11 D21S24 D21S17 D21S113 D21S112 26C 21dU pPW228C pG95-al-lla p21.3 pGSH8 pMCT15 CRI-L427' U U U U E E - E € E - u U U U - 5 - E E - - - - E E E E - - - € 8 7 8 9 € € € E - E - - € - E ' - - E E - € E - E 11 12 - € - - E E - € € € - 10 E € E E - E € 13 E E E E - - - E E - - E E - E E E - E Abbreviations: U, unequal; E, equal; -, unknown because only one band was observed or not tested. VNTR probe. 2 a (W 4.4 2a 2.0 6 b a 5 ------13 - -3 -7 8 --1 b a 14 b a b a b 15 a 12 11 b a b a 4 b a a a a a 9 1 0 a a - - \ \ Fig 1. Reatrktlon fragment length polymorphh analysis of chromosome 2 In I w k m k wlls (lanes a) and nonlwkemk wlh (lanes b). lanes am labeled with the petlent number. DNA was digested with Mspl and hvbrldlzedwith probe pYNH24, which recognizes a VMR polymorphism on chromosome 2. The faint bands In the lanes containing DNA from leukemic cells of patients 2 and 8 represent residual normal bone marrow cells present in the samples. From www.bloodjournal.org by guest on February 6, 2015. For personal use only. ONODERA, McCABE, AND RUBIN 206 (kb) 3.0 - 2.0 - 5 1 2 4 1 2 4 10 11 12 13 C l 9 A (kb) 6.1 - 4.1 - 5 9 1 0 11 12 13 c 2 c3 B (kb) C 18.5 12.3 - 1 3 6 7 0 IrUyI-1,- a partial deletion of the short arm of chromosome 12 and a dicentric chromosome 21, and two patients (patients & dnd 13) had marker chromosomes. Analysis of wstrictionji-ament length polymorphism. We first examined chromosomes present in two copies for loss of heterozygosity. Two patients (patients 2 and 6) had widespread loss of heterozygosity on all informative disomic chromosomes, and represent cases of near-haploid ALL in which the chromosomes doubled." Eight probes from eight chromosomes demonstrated loss of heterozygosity in patient 2 and eight probes from five chromosomes Flg 2. Rsmiction fragment lengthpolymorphismanalysbusing probes from chromosome 21. Lanes containing DNA from leukemic samples are labeled with the patient number. Lanes C1, CZ, and C3 contain DNA from the blood of healthy controls. (A) DNA was digested with EcoM and hybridizedwith probe pG95a l - l l a . (B) DNA was digested with -1 and hybridized with a VNTR probe CRI-l.427. (C) DNA was digested with B@ll and hybridized with probe pGSHB. Results of densitometry of them autoradiograms are shown in Table 4. demonstrated loss of heterozygosity in patient 6. One patient (patient 15) had loss of heterozygosity limited to chromosome 3; this was demonstrated separately with probes for the short and long arms of chromosome 3. Eight loci on seven other disomic chromosomes in patient 15 retained heterozygosity. Loss of heterozygosity was not detected in the remaining 12 patients; a total of 106 informative loci on 87 disomic chromosomes retained both parental alleles (Fig 1 and Table 2). We then examined the parental dosage of chromosome 21, when it was present in four copies. Eight probes for From www.bloodjournal.org by guest on February 6, 2015. For personal use only. FORMATION OF A HYPERDIPLOID KARYOTYPE chromosome 21 were used; informative results were obtained with three or more probes in all cases. Of the 13 patients without widespread loss of heterozygosity, 11 patients had tetrasomy 21; 10 of 11 (91%) had an equal dose of maternal and paternal alleles on chromosome 21 and 1 of 11 (9%) had an unequal dose in a 3:l ratio. In all patients the relative parental contribution was consistent at several positions on chromosome 21 (Fig 2 and Table 3). Results of densitometry for the three autoradiograms in Fig 2 are shown in Table 4. Patient 1 had an approximately 3:l ratio in the density of the two allelic bands in autoradiograms made with three probes from chromosome 21. Two other patients (patients 3 and 5) and normal controls had an approximately equal ratio in the same experiments. DISCUSSION The results of this study provide molecular data pertinent to the mechanism of formation of a hyperdiploid karyotype with 250 chromosomes in childhood ALL. We have considered four possible routes by which a normal diploid precursor cell might become hyperdiploid: (1) development of near-haploidy followed by doubling of the chromosomes; (2) development of tetraploidy with subsequent loss of chromosomes; (3) gains of individual chromosomes in a sequential fashion through multiple independent nondisjunction events; and (4) simultaneous gain of multiple chromosomes in a single abnormal cell division. We have demonstrated the occasional occurrence of route 1 in patients 2 and 6.l' There is widespread loss of heterozygosity on all disomic chromosomes. A strong suspicion of this mechanism is raised by the karyotype in these cases. Specifically, all chromosomes are present in either two or four copies in the hyperdiploid clone. These cases probably are classified best with near-haploid cases, which have a relatively unfavorable prognosis. The evidence produced by our study does not favor route 2. If a diploid cell were to become tetraploid and subsequently lose chromosomes, 33% of disomic chromosomes in the hyperdiploid cell should have loss of heterozygosity. This statement assumes that the chromosomes are lost independent of the parental origin. In fact, we observed loss of heterozygosity in only 1 of 95 (1%) of disomic chromosomes in patients with the typical form of the hyperdiploidy. It is possible that selection against loss of heterozygosity led in part to these results. Nevertheless, our best interpretation of the data is inconsistent with development of tetraploidy followed by loss of chromosomes. Route 3 also is not supported by our results. With independent gains of chromosomes by multiple nondisjunction events, it is predicted that 33% of instances of tetrasomy would be characterized by a 2:2 parental dosage and 67% by a 3:l dosage. Our findings, which were derived from 11 patients with tetrasomy 21, were that 10 of 11 (91%) of the tetrasomies consisted of two maternal and two 207 Table 4. Densitometryof Polymorphic Bands Produced by Three Probes From Chromosome 21 Ratio of Intensity (upper band:lower band) Fig 2A Patient 1 Patient 3 Patient 5 Control 1 Cohtrol2 Control 3 2.86:l.OO Fig 2B* Fig 2C 1.00:3.56 - - 1.00:2.52 1.18:I.OO 1 .oo: 1.45 1.33:l.OO 1.07:l.OO - - 1.12:1.00 1 .oo: 1.02 - - - - *VNTR probe was used; mathematical correction was made according to the relative band size (see Materials and Methods and reference 14). paternal copies of chromosome 21 and 1 of 11 (9%) consisted of an unbalanced 3:l parental dosage. These data suggest that the double gain of chromosome 21 occurs in a single cell division as the result of a double nondisjunction; this would consistently result in a 2:2 dosage. We suggest that the chromosomal gains observed in typical cases of hyperdiploid ALL occur in one step during one aberrant cell division (route 4). Supportive of this idea are the cytogenetict6 and DNA content studies17of cases of hyperdiploid ALL, which show distinct populations of normal and hyperdiploid cells, but do not show a gradation of intermediate cells. It is difficult to propose a pathophysiologic basis for a sudden gain of chromosomes in a cell. It is possible that it is a reflection of the primary carcinogenic insult to the cell, whether that be an unprovoked error of the mitotic apparatus or an imposed perturbance by an exogenous agent. In either case the insult does not appear to be sustained, because the abnormal karyotype, once formed, is uniform and stable in the malignant cell population, It remains unclear whether the hyperdiploid karyotype itself contributes directly to the malignant process. Our data do not support the possibility presented in the introduction that all of the extra chromosomes contain mutations that give the cells a proliferative advantage. If this were the case, the tetrasomic chromosomes should have a 3:l parental dosage. Also, we failed to identify a consistent defective chromosomal region through an extensive search for loss of heterozygosity. In two patients we found widespread loss of heterozygosity and in one patient we found loss of heterozygosity limited to chromosome 3; whether loss of tumor suppressor gene function played a role in these cases is unknown. Additional studies of the molecular basis for this leukemia subtype are needed. ACKNOWLEDGMENT We thank Drs Michelle M. Le Beau, Janet D. Rowley, Manuel 0. Diaz, and Robert Burnett for helpful discussions; Dr Stefan Bohlander for assistance with the densitometry; and Drs Ellen Solomon, Gordon D. Stewart, Bradley N. White, and Integrated Genetics (Framingham, MA) for gifts of probes. REFERENCES 1. Kaneko Y, Rowley JD, Variakojis D, Chilcote RR, Check I, 2. Heerema NA, Palmer GG, Baehner R L Karyotypic and Sakurai M: Correlation of karyotype with clinical features in acute clinical findings in a consecutive series of children with acute lymphoblastic leukemia. Cancer Res 422918,1982 lymphoblastic leukemia. Cancer Genet Cytogenet 17:165, 1985 From www.bloodjournal.org by guest on February 6, 2015. For personal use only. 208 3. Prigogina EL, Puchkova GP, Mayakova S A Nonrandom chromosomal abnormalities in acute lymphoblastic leukemia of childhood. Cancer Genet Cytogenet 32:183,1988 4. Pui CH, Williams DL, Robertson PK, Raimondi SC, Behm FG, Lewis SH, Rivera GK, Kalwinski DK, Abromowitch M, Crist WM, Murphy SB: Correlation of karyotype and immunophenotype in childhood acute lymphoblasticleukemia. J Clin Oncol6:56,1988 5. 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Harnden DG, Klinger HP (eds): ISCN, An International System for Human Cytogenetic Nomenclature; published in collaboration with Cytogenet Cell Genet, Karger, Basel, 1985; also in Birth Defects: Original Article Series, Vol 21, No 1, March of Dimes Birth Defects Foundation, New York, NY, 1985 14. Yamada T, Shippey CA, Martineau M, Secker-Walker LM: Demonstration of acquired hemizygosity and clonality in acute lymphoblastic leukemia with chromosome 7 abnormalities using hypervariable DNA probes. Genes Chromosomes Cancer 2:88, 1990 15. Kidd ICK, Bowcock AM, Schmidtke J, Track RK, Riccinti F, Hutching G, Bale A, Pearson P, Willard H F Tenth International Workshop on Human Gene Mapping: Report of the DNA committee and catalogs of cloned and mapped genes and DNA polymorphisms. Cytogenet Cell Genet 51:622,1989 16. Williams DL, Tsiatis A, Brodeur GM, Look TA, Melvin SL, Bowman WP, Kalvinsky DK, Rivera G, Dahl G Prognostic importance of chromosome number in 136 untreated children with acute lymphoblasticleukemia. Blood 60:864, 1982 17. Look AT, Robertson PK, Williams DL, Rivera GK, Bowman WP, Pui CH, Ochs J, Abromowitch M, Kalwinsky D, Dahl GV, George S, Murphy S B Prognostic importance of blast cell DNA content in childhood acute lymphoblasticleukemia. Blood 65:1079, 1985 From www.bloodjournal.org by guest on February 6, 2015. For personal use only. 1992 80: 203-208 Formation of a hyperdiploid karyotype in childhood acute lymphoblastic leukemia [see comments] N Onodera, NR McCabe and CM Rubin Updated information and services can be found at: http://www.bloodjournal.org/content/80/1/203.full.html Articles on similar topics can be found in the following Blood collections Information about reproducing this article in parts or in its entirety may be found online at: http://www.bloodjournal.org/site/misc/rights.xhtml#repub_requests Information about ordering reprints may be found online at: http://www.bloodjournal.org/site/misc/rights.xhtml#reprints Information about subscriptions and ASH membership may be found online at: http://www.bloodjournal.org/site/subscriptions/index.xhtml Blood (print ISSN 0006-4971, online ISSN 1528-0020), is published weekly by the American Society of Hematology, 2021 L St, NW, Suite 900, Washington DC 20036. Copyright 2011 by The American Society of Hematology; all rights reserved.
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