Cytogenetics of childhood acute nonlymphocytic leukemia

Rare Hematologic Malignancies and Pre-Leukemic Entities in Children and Adolescents Young Adults

There are a variety of rare hematologic malignancies and germline predispositions syndromes that occur in children and adolescent young adults (AYAs). These entities are important to recognize, as an accurate diagnosis is essential for risk assessment, prognostication, and treatment. This descriptive review summarizes rare hematologic malignancies, myelodysplastic neoplasms, and germline predispositions syndromes that occur in children and AYAs. We discuss the unique biology, characteristic genomic aberrations, rare presentations, diagnostic challenges, novel treatments, and outcomes associated with these rare entities.

Rare cytogenetic abnormalities and their clinical relevance in pediatric acute leukemia of Saudi Arabian population

Background

Childhood Acute Leukemia (AL) is characterized by recurrent genetic aberrations in 60% of AML cases and 90% of ALL cases. Insufficient data exists of rare cytogenetic abnormalities in AL. Therefore, we tested rare cytogenetic abnormalities occurring in childhood AL and its effect on clinical prognosis in patients diagnosed at our institution from 2010 to 2017.

Results

Among 150 cases of AL, we detected 9 cases with rare chromosomal abnormalities. We found two hypodiploid (2n-) cases: 2n-,t (5;14)(q31;q32) and t (3;11;19)(q21;q23;q13.1) in ALL patients. AML patients showed t (7;14)(q22;q32), t (11;17)(p15;q21), t (11;20) (p15;q11), t (12;17)(q15;q23) and t (11;20)(p15;q11). Both t (1;15)(q10;q10) and t (17;19)(q21;p13.3) occurred in a case with biphenotypic AL. Complete remission (CR) status was attained in 3 patients and 6 patients never attained CR or relapsed/demised.

Conclusion

The study highlighted that rare cytogenetic abnormalities are associated with a poor prognosis. This finding is not well reported in the literature suggesting that ongoing cytogenetic studies for rare abnormalities associated with pediatric leukaemia are warranted.

Prognostic impact of t(16;21)(p11;q22) and t(16;21)(q24;q22) in pediatric AML: a retrospective study by the I-BFM Study Group

To study the prognostic relevance of rare genetic aberrations in acute myeloid leukemia (AML), such as t(16;21), international collaboration is required. Two different types of t(16;21) translocations can be distinguished: t(16;21)(p11;q22), resulting in the FUS-ERG fusion gene; and t(16;21)(q24;q22), resulting in RUNX1-core binding factor (CBFA2T3). We collected data on clinical and biological characteristics of 54 pediatric AML cases with t(16;21) rearrangements from 14 international collaborative study groups participating in the international Berlin-Frankfurt-Münster (I-BFM) AML study group. The AML-BFM cohort diagnosed between 1997 and 2013 was used as a reference cohort. RUNX1-CBFA2T3 (n = 23) had significantly lower median white blood cell count (12.5 × 10⁹/L, P = .03) compared with the reference cohort. FUS-ERG rearranged AML (n = 31) had no predominant French-American-British (FAB) type, whereas 76% of RUNX1-CBFA2T3 had an M1/M2 FAB type (M1, M2), significantly different from the reference cohort (P = .004). Four-year event-free survival (EFS) of patients with FUS-ERG was 7% (standard error [SE] = 5%), significantly lower compared with the reference cohort (51%, SE = 1%, P < .001). Four-year EFS of RUNX1-CBFA2T3 was 77% (SE = 8%, P = .06), significantly higher compared with the reference cohort. Cumulative incidence of relapse was 74% (SE = 8%) in FUS-ERG, 0% (SE = 0%) in RUNX1-CBFA2T3, compared with 32% (SE = 1%) in the reference cohort (P < .001). Multivariate analysis identified both FUS-ERG and RUNX1-CBFA2T3 as independent risk factors with hazard ratios of 1.9 (P < .0001) and 0.3 (P = .025), respectively. These results describe 2 clinically relevant distinct subtypes of pediatric AML. Similarly to other core-binding factor AMLs, patients with RUNX1-CBFA2T3 rearranged AML may benefit from stratification in the standard risk treatment, whereas patients with FUS-ERG rearranged AML should be considered high-risk.

Global characteristics of childhood acute promyelocytic leukemia

Acute promyelocytic leukemia (APL) comprises approximately 5-10% of childhood acute myeloid leukemia (AML) cases in the US. While variation in this percentage among other populations was noted previously, global patterns of childhood APL have not been thoroughly characterized. In this comprehensive review of childhood APL, we examined its geographic pattern and the potential contribution of environmental factors to observed variation. In 142 studies (spanning >60 countries) identified, variation was apparent-de novo APL represented from 2% (Switzerland) to >50% (Nicaragua) of childhood AML in different geographic regions. Because a limited number of previous studies addressed specific environmental exposures that potentially underlie childhood APL development, we gathered 28 childhood cases of therapy-related APL, which exemplified associations between prior exposures to chemotherapeutic drugs/radiation and APL diagnosis. Future population-based studies examining childhood APL patterns and the potential association with specific environmental exposures and other risk factors are needed.

Integrated genome-wide genotyping and gene expression profiling reveals BCL11B as a putative oncogene in acute myeloid leukemia with 14q32 aberrations

Acute myeloid leukemia is a neoplasm characterized by recurrent molecular aberrations traditionally demonstrated by cytogenetic analyses. We used high density genome-wide genotyping and gene expression profiling to reveal acquired cryptic abnormalities in acute myeloid leukemia. By genome-wide genotyping of 137 cases of primary acute myeloid leukemia, we disclosed a recurrent focal amplification on chromosome 14q32, which included the genes BCL11B, CCNK, C14orf177 and SETD3, in two cases. In the affected cases, the BCL11B gene showed consistently high mRNA expression, whereas the expression of the other genes was unperturbed. Fluorescence in situ hybridization on 40 cases of acute myeloid leukemia with high BCL11B mRNA expression [2.5-fold above median; 40 out of 530 cases (7.5%)] revealed 14q32 abnormalities in two additional cases. In the four BCL11B-rearranged cases the 14q32 locus was fused to different partner chromosomes. In fact, in two cases, we demonstrated that the focal 14q32 amplifications were integrated into transcriptionally active loci. The translocations involving BCL11B result in increased expression of full-length BCL11B protein. The BCL11B-rearranged acute myeloid leukemias expressed both myeloid and T-cell markers. These biphenotypic acute leukemias all carried FLT3 internal tandem duplications, a characteristic marker of acute myeloid leukemia. BCL11B mRNA expression in acute myeloid leukemia appeared to be strongly associated with expression of other T-cell-specific genes. Myeloid 32D(GCSF-R) cells ectopically expressing Bcl11b showed decreased proliferation rate and less maturation. In conclusion, by an integrated approach involving high-throughput genome-wide genotyping and gene expression profiling we identified BCL11B as a candidate oncogene in acute myeloid leukemia.

Pediatric acute myeloid leukemia with t(8;16)(p11;p13), a distinct clinical and biological entity: a collaborative study by the International-Berlin-Frankfurt-Munster AML-study group

In pediatric acute myeloid leukemia (AML), cytogenetic abnormalities are strong indicators of prognosis. Some recurrent cytogenetic abnormalities, such as t(8;16)(p11;p13), are so rare that collaborative studies are required to define their prognostic impact. We collected the clinical characteristics, morphology, and immunophenotypes of 62 pediatric AML patients with t(8;16)(p11;p13) from 18 countries participating in the International Berlin-Frankfurt-Münster (I-BFM) AML study group. We used the AML-BFM cohort diagnosed from 1995-2005 (n = 543) as a reference cohort. Median age of the pediatric t(8;16)(p11;p13) AML patients was significantly lower (1.2 years). The majority (97%) had M4-M5 French-American-British type, significantly different from the reference cohort. Erythrophagocytosis (70%), leukemia cutis (58%), and disseminated intravascular coagulation (39%) occurred frequently. Strikingly, spontaneous remissions occurred in 7 neonates with t(8;16)(p11;p13), of whom 3 remain in continuous remission. The 5-year overall survival of patients diagnosed after 1993 was 59%, similar to the reference cohort (P = .14). Gene expression profiles of t(8;16)(p11;p13) pediatric AML cases clustered close to, but distinct from, MLL-rearranged AML. Highly expressed genes included HOXA11, HOXA10, RET, PERP, and GGA2. In conclusion, pediatric t(8;16)(p11;p13) AML is a rare entity defined by a unique gene expression signature and distinct clinical features in whom spontaneous remissions occur in a subset of neonatal cases.

RUNX1 translocations and fusion genes in malignant hemopathies

The RUNX1 gene, located in chromosome 21q22, is crucial for the establishment of definitive hematopoiesis and the generation of hematopoietic stem cells in the embryo. It contains a 'Runt homology domain' as well as transcription activation and inhibition domains. RUNX1 can act as activator or repressor of target gene expression depending upon the large number of transcription factors, coactivators and corepressors that interact with it. Translocations involving chromosomal band 21q22 are regularly identified in leukemia patients. Most of them are associated with a rearrangement of RUNX1. Indeed, at present, 55 partner chromosomal bands have been described but the partner gene has solely been identified in 21 translocations at the molecular level. All the translocations that retain Runt homology domains but remove the transcription activation domain have a leukemogenic effect by acting as dominant negative inhibitors of wild-type RUNX1 in transcription activation.

Acute myeloid leukemia with t(16;21)(q24;q22) and eosinophilia: case report and review of the literature

The t(16;21)(q24;q22), a rare chromosomal translocation involving chromosome 21 in de novo and therapy-related acute myeloid leukemia (AML), produces a RUNX1-CBFA2T3 fusion gene (previously AML1-MTG16) fusion gene. The translocation has been reported in 20 patients with AML, with eosinophilia present in 3 cases. Here we report a pediatric case of t(16;21)(q24;q22) in de novo AML with eosinophilia and suggest that eosinophilia is a hematologic characteristic of at least a subpopulation of AML with t(16;21)(q24;q22). A 4-year-old Korean girl was admitted with complaints of pale appearance and dizziness, and was diagnosed with acute myelomonocytic leukemia. On admission, laboratory evaluation revealed hemoglobin at 3.3 g/dL, platelets at 9.0 x 10(9)/L, and white blood cells at 9.1 x 10(9)/L with 10% eosinophils and 1% blasts. The bone marrow aspirate contained 31% blasts and 11% eosinophils. Flow cytometric analysis revealed the expression of CD13, CD14, CD19, CD33, CD34, and HLA-DR by the leukemic blasts. The karyotype was 47,XX, + 8,t(16;21)(q24;q22)[18]/46,XX[2]. Interphase fluorescence in situ hybridization analysis with a dual-color, dual-fusion translocation LSI AML1/ETO probe set for RUNX1 and RUNX1T1 produced three signals for each probe in 90% of interphases, but no fusion signals. We confirmed the presence of RUNX1-CBFA2T3 fusion transcripts with reverse transcriptase-polymerase chain reaction, using primers AML1ex5f1 and MTG16r2.

RUNX1-MTG16 fusion gene in acute myeloblastic leukemia with t(16;21)(q24;q22): case report and review of the literature

We report here a 73-year old female who was admitted for hematomas, dyspnea, and fever. Hematological data showed pancytopenia with 9% blast cells positive for CD13, CD33, CD34, HLAD2, and myeloperoxydase. A diagnosis of acute myeloid leukemia (AML) type 2 (FAB classification) was made. Banding cytogenetic techniques performed on bone marrow cells showed a 48,XX,+8,+9,del(9)(q22q33)x2 ,t(16;21)(q24;q22)[20]/46,XX[2] karyotype. Fluorescence in situ hybridization (FISH) with BACs covering the RUNX1 (alias AML1) (band 21q22) and MTG16 (band 16q24) gene showed a fusion of both genes. The t(16;21)(q24;q22) has been described in 16 AML cases, including ours. Eleven patients had received chemotherapy for a previous cancer, most of them were been treated with DNA-topoisomerase II inhibitors known to be associated with chromosomal translocations involving the RUNX1 gene. The significant homology between MGT16 and MTG8 suggests that the RUNX1-MTG16 fusion gene induced by the t(16;21)(q24;q22) is a variant of the RUNX1-MTG8 that shares similar activity.

Myelodysplastic syndromes with isolated deletion of the long arm of the chromosome X as a sole cytogenetic change

Deletions of Xq are extremely rare events in myelodysplastic syndromes (MDS) patients and were previously described in five patients, in two of them as a sole chromosome abnormality. We found isolated del(Xq) in 3 of 127 MDS patients with clonal chromosome changes. Detailed analysis of clinical and morphological data of presented and previously published cases indicates the following: (1) del(X)(q24) and del(X)(q13) are nonrandom chromosomal abnormalities in MDS; (2) MDS with deletions of Xq affect exclusively females ages 46-65; and (3) deletions of Xq are associated with refractory anemia with excess blasts (RAEB) and indicate an unfavorable prognosis.

Genomic assessment of pediatric acute leukemia

Advances in molecular genetics have revolutionized our understanding of acute myeloid and lymphoblastic leukemia. Structural and numerical chromosomal aberrations are common, and their detection is vital for leukemia diagnosis, risk stratification, and monitoring of response to therapy. Fusion proteins resulting from chromosomal translocations are necessary but not sufficient for leukemogenesis, and there is intense research activity to elucidate the cooperating molecular abnormalities that may be suitable targets for novel therapeutic approaches. Candidate gene approaches have identified mutations in kinases and transcription factors in a proportion of patients, but more comprehensive genomic approaches are required. Gene expression profiling accurately classifies known subtypes of acute leukemia and has highlighted potentially leukemogenic abnormalities in gene expression. Newer techniques, such as single-nucleotide polymorphism arrays to analyze changes in gene copy number and zygosity, cancer genome sequencing, and RNA interference, are promising tools to identify mutations, although at present, data from these approaches are limited. This review provides an overview of these techniques in clinical practice and as research tools to develop new therapeutic approaches in pediatric leukemia.

Rearrangement of the MLL gene in acute myeloblastic leukemia: report of two rare translocations

Band 11q23 is known to be involved in translocations and insertions with a variety of partner chromosomes. They lead to MLL rearrangement, resulting in a fusion with numerous genes. We report here 2 male adults in whom a diagnosis of acute myelomonoblastic leukemia (FAB M4) and acute monoblastic leukemia (FAB M5) was made. Conventional cytogenetic techniques showed a 45,XY,t(1;11)(p32;q23),-7 karyotype in the first case and a 46,XY, t(11;17)(q23;q21) in the second case. Fluorescent in situ hybridization (FISH) with a specific MLL probe showed the gene to be disrupted, the 3' region being translocated on the derivative chromosomes 1 and 17, respectively. Fourteen and 24 patients, including ours, with acute myeloblastic leukemia associated with a t(1;11)(p32;q23) and a t(11;17)(q23;q21), respectively have been reported in the literature. Several patients with the latter translocation have also been identified to have acute lymphoblastic leukemia (ALL). Although both translocations are preferentially associated with monocytic differentiation, the t(11;17)(q23;q21) is more common in adults and has been reported in many patients with ALL, compared to the t(1;11)(p32;q23).

Cytogenetics in acute leukemia

Cytogenetic analyses in acute myeloid leukemia (AML) and acute lymphoblastic leukemia (ALL) have revealed a great number of non-random chromosome abnormalities. In many instances, molecular studies of these abnormalities identified specific genes implicated in the process of leukemogenesis. The more common chromosome aberrations have been associated with specific laboratory and clinical characteristics, and are now being used as diagnostic and prognostic markers guiding the clinician in selecting the most effective therapies. Specific chromosome aberrations and their molecular counterparts have been included in the World Health Organization classification of hematologic malignancies, and together with morphology, immunophenotype and clinical features are used to define distinct disease entities. However, the prognostic importance of less frequent recurrent aberrations in AML and ALL, both primary and secondary, is still to be determined. This review summarizes current views on clinical relevance of major cytogenetic findings in adult AML and ALL.

A novel t(6;14)(q25-q27;q32) in acute myelocytic leukemia involves the BCL11B gene

Cytogenetic studies in a patient with acute myelocytic leukemia (AML) revealed as the sole karyotypic alteration a half-cryptic rearrangement, identified with 48-color combined binary ratio-labeled fluorescence in situ hybridization (pq-COBRA-FISH) as a reciprocal t(6;14)(q?;q?). The breakpoints were later assigned on the basis of G-banding to t(6;14)(q25-q26;q32). FISH experiments using genomic probes showed that the breakpoint on 14q32.2 was within bacterial artificial chromosome RP11-782I5 and revealed BCL11B as the only candidate gene in the region. BCL11B is a homolog to BCL11A (2p13), a highly conserved gene implicated in mouse and human leukemias. To our knowledge, this is the first report implicating BCL11B in hematological malignancies. Because of lack of material, the translocation partner remains unknown.

Translocation (X;20)(q13.1;q13.3) as a primary chromosomal finding in two patients with myelocytic disorders

Reports of X chromosome translocations, as primary chromosomal changes associated with hematologic disorders, remain relatively uncommon. Herein, we report the detection, by conventional cytogenetic methods, of a cytogenetically identical t(X;20) in two different patients with hematologic disorders (probable myelodysplasia and polycythemia vera/acute myelocytic leukemia). In both cases, this translocation appeared as the primary clonal chromosome abnormality, with breakpoints occurring in the long arms of both the X chromosome and chromosome 20 (Xq13.1 and 20q13.3, respectively). Further characterization and comparison of the translocation chromosome products of these two cases by use of fluorescence in situ hybridization techniques is also described. Similar previously reported cytogenetically cases and the potential that this specific rearrangement may represent a nonrandom chromosomal finding are discussed.

Novel clonal der(8)t(8;14)(p11;q11),del(9)(q13q22) and t(14;22) (q13;q13) in a patient with fulminant adult T-cell leukemia/lymphoma

We describe a 70-year-old man with fulminant adult T-cell leukemia/lymphoma. He died of progressive disease 1 week after the onset of symptoms. The integrated viral DNA of human T-lymphotropic virus type I was detected in the bone marrow aspirate by polymerase chain reaction. Cytogenetic analysis of bone marrow cells showed novel clonal aberrations consisting of 46,XY,der(8)t(8;14)(p11;q11),del(9) (q13q22),t(14;22)(q13;q13).

Antigen expression patterns reflecting genotype of acute leukemias

Multi-parameter flow cytometry, molecular genetics, and cytogenetic studies have all contributed to new classification of leukemia. In this review we discuss immunophenotypic characteristics of major genotypic leukemia categories. We describe immunophenotype of: B-lineage ALL with MLL rearrangements, TEL/AML1, BCR/ABL, E2A/PBX1 translocations, hyperdiploidy, and myc fusion genes; T-ALL with SCL gene aberrations and t(5;14) translocation; and AML with AML1/ETO, PML/RARalpha, OTT/MAL and CBFbeta/MYH11 translocations, trisomies 8 or 11 and aberrations of chromosomes 7 and 5. Whereas some genotypes associate with certain immunophenotypic features, others can present with variable immunophenotype. Single molecules (as NG2, CBFbeta/SMMHC and PML/RARalpha proteins) associated with or derived from specific translocations have been described. More often, complex immunophenotype patterns have been related to the genotype categories. Most known associations between immunophenotype and genotype have been defined empirically. Therefore, these associations should be validated in independent patient cohorts before they can be widely used for prescreening of leukemia. Progress in our knowledge on leukemia will show how the molecular-genetic changes modulate the immunophenotype as well as how the expressed protein molecules further modulate cell behavior.

21q22 balanced chromosome aberrations in therapy-related hematopoietic disorders: report from an international workshop

The International Workshop on the relationship between prior therapy and balanced chromosome aberrations in therapy-related myelodysplastic syndromes (t-MDS) and therapy-related acute leukemia (t-AL) identified 79 of 511 (15.5%) patients with balanced 21q22 translocations. Patients were treated for their primary disease, including solid tumors (56%), hematologic malignancy (43%), and juvenile rheumatoid arthritis (single case), by radiation therapy (5 patients), chemotherapy (36 patients), or combined-modality therapy (38 patients). 21q translocations involved common partner chromosomes in 81% of cases: t(8;21) (n = 44; 56%), t(3;21) (n = 16; 20%), and t(16;21) (n = 4; 5%). Translocations involving 15 other partner chromosomes were also documented with involvement of AML1(CBFA2/RUNX1), identifying a total of 23 different 21q22/AML1 translocations. The data analysis was carried out on the basis of five subsets of 21q22 cases, that is, t(8;21) with and without additional aberrations, t(3;21), t(16;21), and other 21q22 translocations. Dysplastic features were present in all 21q22 cases. Therapy-related acute myeloid leukemia (t-AML) at presentation was highest in t(8;21) (82%) and lowest in t(3;21) (37.5%) patients. Cumulative drug dose exposure scores for alkylating agents (AAs) and topoisomerase II inhibitors indicated that t(3;21) patients received the most intensive therapy among the five 21q22 subsets, and the median AA score for patients with secondary chromosome 7 aberrations was double the AA score for the entire 21q22 group. All five patients who received only radiation therapy had t(8;21) t-AML. The median latency and overall survival (OS) for 21q22 patients were 39 and 14 months (mo), compared to 26 and 8 mo for 11q23 patients, 22 and 28 mo for inv(16), 69 and 7 mo for Rare recurring aberrations, and 59 and 7 mo for Unique (nonrecurring) balanced aberration (latency P < or = 0.016 for all pairwise comparisons; OS, P < or = 0.018 for all pairwise comparisons). The percentages of 21q22 patients surviving 1 year, 2 years, and 5 years were 58%, 33%, and 18%, respectively. Noticeable differences were observed in median OS between 21q22 patients (n = 7) receiving transplant (BMT) (31 mo) compared to 21q22 patients who received intensive non-BMT therapy (n = 46) (17 mo); however, this was nonsignificant because of the small sample size (log-rank, P = 0.33). t-MDS/t-AML with balanced 21q22 aberrations was associated with prior exposure to radiation, epipodophyllotoxins, and anthracyclines, dysplastic morphologic features, multiple partner chromosomes, and longer latency periods when compared to 11q23 and inv(16) t-MDS/AML Workshop subgroups. In general, patients could be divided into two prognostic risk groups, those with t(8;21) (median OS, 19 mo) and those without t(8;21) (median OS, 7 mo) leukemia (log-rank, P = 0.0007).

The amino terminus targets the mixed lineage leukemia (MLL) protein to the nucleolus, nuclear matrix and mitotic chromosomal scaffolds

The mixed-lineage leukemia gene (MLL) is associated with more than 25 chromosomal translocations involving band 11q23 in diverse subtypes of human acute leukemia. Conditional expression of a 50 kDa amino terminal fragment spanning the AT hook motifs of MLL (MLL3AT) causes cell cycle arrest, upregulation of p21Cip1 and p27KiP1 and partial monocytic differentiation of the monoblastic U937 cell line, suggesting a major role for MLL3AT in MLL-AF9-induced myelomonocytic differentiation. In this study, we analyzed the subcellular localization of conditionally expressed MLL3AT in both U937 and HeLa cell lines. Immunofluorescence staining, confocal laser scanning microscopy and immunoelectron microscopy indicated that MLL3AT, like endogenous MLL, localized in the nucleoplasm in a punctate pattern of distribution, including regions attached to the nuclear envelope and the periphery of the nucleolus. We found that MLL3AT and endogenous MLL were present in interphase nuclear matrices and colocalized with topoisomerase II to mitotic chromosomal scaffolds. Nucleoplasm and nucleolar localization was observed even for MLL-AF9 and MLL-AF4 conditionally expressed chimeric proteins, suggesting a common target conferred by the amino terminus of MLL to many if not all the chimeric MLL proteins. The nuclear matrix/scaffold association suggests a role for the amino terminus of MLL in the modulation of chromatin structure, leading to epigenetic effects on the maintenance of gene expression.

Deletion of Xq23 is a recurrent karyotypic abnormality in acute myeloid leukemia

Deletion of chromosome Xq23 has been reported in a number of solid tumors, including soft tissue sarcoma, malignant melanoma, astrocytoma, and adenocarcinoma. The deleted Xq often occurs in a setting of very complex karyotypic changes. A similar abnormality has also been described in rare cases of acute myeloid leukemia (AML) but in no other hematologic malignancies. In this study, we report the occurrence of del(X)(q23) in two cases of AML.

Spontaneous remission of congenital leukemia: a case for conservative treatment

A newborn infant with spontaneous remission of congenital leukemia cutis is described and a literature review of this uncommon phenomenon is provided. In view of the unusual and unpredictable behavior of this disease, chemotherapy should be withheld unless there is evidence of an 11q23 translocation or progressive disease. Otherwise, overall survival does not appear to be affected by adopting a conservative approach. Because of occasional late relapses, long-term follow-up is recommended. The biologic basis underlying spontaneous remission of congenital leukemia is unknown; therefore, molecular or molecular cytogenetic analysis of DNA obtained from a skin biopsy is recommended.

Translocation (12;17)(q13;q23) in de novo acute myeloid leukemia with trilineage myelodysplasia

12q13 abnormalities have been reported to be associated with a variety of benign and malignant solid tumors. Recently, they have been shown to be a nonrandom karyotypic change in acute myeloid leukemia. We report a case of de novo acute myeloid leukemia with trilineage myelodysplasia showing t(12;17)(q13;q23) as the sole chromosomal abnormality. A review of the literature indicates that 12q13 translocation in acute myeloid leukemia is often associated with concomitant dysmyelopoietic changes. There is also evidence to suggest that 12q13 translocation occurs more frequently in acute myeloid leukemia with a prior history of mutagenic exposure or karyotypic indicators of secondary leukemia.

Comparative genomic hybridization and conventional cytogenetic analyses in childhood acute myeloid leukemia

Comparative genomic hybridization (CGH) analysis was performed on bone marrow specimens from 19 children with acute myeloid leukemia (AML) at diagnosis. The results of CGH were compared to those of conventional cytogenetic analysis. The most common CGH aberrations were gains of whole chromosomes 6 and 8, both of which appeared three times. Two losses were seen twice; losses of whole chromosomes 7 and X. The CGH findings were concordant with the results of conventional karyotyping. CGH did not add new information to the karyotypes. Since no high-level amplification was found among the samples and standard karyotyping was highly successful, we do not advocate routine use of CGH in the diagnostic evaluation of childhood AML.

11q13 is a cytogenetically promiscuous site in hematologic malignancies

11q13 translocation has been described in mantle cell lymphoma in the form of t(11;14) (q13;q32), with rearrangement and over-expression of the cyclin D1 gene. Recently, an association between 11q13 and acute myeloid leukemia is recognized. We describe the occurrence of 11q13 translocations in both acute leukemias and myelodysplastic syndrome, and suggest that other genetic mechanisms unrelated to cyclin D1 may be involved in the tumorigensis. Furthermore, 11q13 appears to be a cytogenetically promiscuous site involved in reciprocal translocations with different chromosomes in both myeloid and lymphoid malignancies.

Improved outcome of acute myeloid leukaemia in Down's syndrome

OBJECTIVE

To review the clinical features, treatment, and outcome of children in the UK with Down's syndrome and acute myeloid leukaemia (AML).

DESIGN

A retrospective study of 59 children with Down's syndrome and AML presenting between 1987 and 1995. Data were obtained from hospital case notes, trial records, and by questionnaire.

RESULTS

The patients were unusually young (median age, 23 months) with a predominance of megakaryoblastic AML. Two of the seven infants who presented with abnormal myelopoesis aged 2 months or younger achieved complete spontaneous remission. Most of the older children with AML (32 of 52) were treated on recognised intensive protocols but 13 received individualised treatment and seven symptomatic treatment alone. Only four received a bone marrow transplant (BMT) in first remission. For the 45 older children who received chemotherapy the overall survival was 55% (median follow up 4.5 years). Patients on individualised protocols had a similar overall survival and toxic death rate but marginally higher relapse rate than those on standard (intensive) protocols. Children with Down's syndrome treated on the national AML 10 trial had a similar overall survival (70% v 59%) at five years to children of comparable age without Down's syndrome: their improved relapse risk (12% v 38%) offset the slight increase in deaths as a result of treatment toxicity (19% v 11%).

CONCLUSION

Neonates with Down's syndrome and abnormal myelopoesis may achieve spontaneous remission, and older children with Down's syndrome and AML can be treated successfully with intensive chemotherapy, without BMT.

Chromosomal rearrangements in childhood acute myeloid leukemia and myelodysplastic syndromes

Recurrent chromosomal abnormalities present in the malignant cells of children with acute myeloid leukemia (AML) and myelodysplastic syndromes (MDS) often correlate closely with specific clinical and biologic characteristics of the disease. Certain unique cytogenetic rearrangements are associated with distinct morphologic leukemic subtypes. These rearrangements should be detectable in most children with AML and MDS with the use of complementary molecular techniques such as fluorescence in situ hybridization (FISH), Southern blotting, and polymerase chain reaction. Apart from the diagnostic assessment, cytogenetic findings sometimes predict clinical outcome and thus also serve as prognostic parameters, which may affect the therapeutic decision. Alternative classifications of AML that take into account the genetic information are being proposed. Cytogenetic and molecular analyses may allow clinicians to more appropriately direct types of treatment. Abnormal fusion transcripts and chimeric proteins derived from karyotypic abnormalities now are being also targeted by novel therapeutic approaches.

Documentation of EWS gene rearrangements by fluorescence in-situ hybridization (FISH) in frozen sections of Ewing's sarcoma-peripheral primitive neuroectodermal tumor

Prompt and accurate diagnosis of small round cell tumors warrants ancillary studies. Recently, two-color fluorescence in-situ hybridization (FISH) using probes for specific gene rearrangements has gained wide acceptance. EWS gene rearrangements, present in essentially 100% of Ewing's Sarcoma/peripheral primitive neuroectodermal tumor, were evaluated by FISH on frozen sections (FS) of tumor biopsies from 10 patients, plus a negative control, and in seven other malignant neoplasms of childhood. 4mu FS were hybridized overnight, using a single EWS gene-specific probe spanning the EWS breakpoint. We identified EWS rearrangements in 8 of 10 cases (80%) of Ewing's Sarcoma/pPNET. There are no known false positives in diploid or near-diploid tumors, or in any of the non-EWS tumors tested; the uncommon false negative can be confirmed by RT-PCR. Hyperdiploid cases with multiple copies of chromosome 22 may be better evaluated by two-color FISH. This is the first use on FS biopsy material of a single probe for EWS, capable of detecting all known EWS rearrangements, in ES and other tumors. Utilization of this ancillary technique on FS for ES/pPNET and other tumors with distinctive chromosomal translocation is highly specific, reliable, expeditious (24-36 hours) and cost-effective.

Molecular monitoring of minimal residual disease in acute myeloblastic leukemia with t(8;21) by RT-PCR

The t(8;21) is one of the most common translocations in acute myeloid leukaemia (AML) occurring in approximately 20% of adult and 40% of paediatric AML-M2. This translocation fuses the AML1 gene on chromosome 21q to the MTG8 (ETO) gene on chromosome 8q to produce the fusion gene AML1-MTG8. Transcripts for the AML1-MTG8 fusion gene have been detected in the majority of patients in remission by qualitative RT-PCR methods. Thus for such patients these methods are unsuitable for monitoring minimal residual disease (MRD). Furthermore, the diverse form of transcripts for this fusion gene was found in patients at different phases of their disease, which rules out the usefulness of the expression of any particular set of transcripts as a marker for monitoring MRD in those patients. On the other hand a quantitative RT-PCR method we developed, was able to assess the effectiveness of treatment and predict relapse up to four months before the onset of haematological relapse. This method should distinguish patients in stable remission from those at high risk of relapse and therefore identify patients who would require additional or new treatment such as BMT.

Translocation (10;11)(p13;q13) and MLL gene rearrangement in a case of AML (M5a) with aggressive leukemia cutis

A male patient with a secondary acute monocytic leukemia whose leukemia cells had a t(10;11)(p13;q13) chromosomal abnormality is described. Gene analysis disclosed that the patient's leukemia cells had MLL gene rearrangement. His leukemia cells responded poorly to chemotherapy, and the patient developed an unusual aggressive leukemia cutis. A t(10;11)(p13;q13) chromosomal abnormality that expresses MLL gene rearrangement has not been reported previously in secondary leukemia.

Acute myeloblastic leukemia associated with trisomy 8 and translocation 8;21 in a child with Down syndrome

The present study examined an 11-year-old girl with Down syndrome who suffered from acute myeloblastic leukemia (AML) preceded by preleukemic pancytopenia. Chromosomal analysis of leukemic cells revealed a chromosome change at t(8;21) and trisomy 8 associated with constitutional trisomy 21. Treatment with antineoplastic agents led to complete remission.

A recurrent translocation, t(16;21)(q24;q22), associated with acute myelogenous leukemia: identification by fluorescence in situ hybridization

Chromosome fluorescence in situ hybridization (FISH) analyses were performed on bone marrow cells in 3 adult patients with MDS or AML with a (16;21)(q24;q22) translocation. FISH analyses with AML1 probes at 21q22 proved in all 3 patients splitting of the AML1 gene at a region spanning exons 5 and 6 and the translocation of its 5' segment to distal 16q. Chromosome painting FISH analysis in patient 1 proved the translocation of the distal 21q segment to 16q, but it failed to prove the presumed translocation of the distal 16q segment to 21q, most likely because of its small size.

Molecular cytogenetics of childhood acute myelogenous leukaemias

Chromosome abnormalities of childhood acute myeloblastic leukaemia, observed at least in 70-80% of cases, are presently recognized as important parameters for diagnostic, prognostic and follow-up purposes. These abnormalities are numerical, structural or both numerical and structural. They are also classified in "primary" abnormalities, usually more or less related with one subtype of leukaemia, and "secondary" abnormalities thought to appear in a second time. Chromosome abnormalities of childhood acute myeloblastic leukaemia (AML) are not basically qualitatively different from those of adult AML. The main difference lies in the incidence of the various types of abnormalities, and these differences appear to be more marked for age extremes such as infants and elderly patients. In total, 3 common abnormalities are more frequently observed in childhood than in adult AML; t(8;21) in AML-M2, monosomy 7 in AML-M4, der(11q) in AML-M5. In addition, molecular rearrangements associated with chromosomal abnormalities are dependent on the type of rearrangement and not on age. As in adult AML, the prognostic value of chromosome abnormalities has been diversely evaluated; some anomalies seem to be related to a shorter survival than others independent of the various therapeutic protocols used. In the present work, chromosome abnormalities of childhood AML have been reviewed according to cytologic subtypes as well as to some clinical settings. Special attention has been paid to abnormalities frequently or exclusively encountered in children.

Detection of chimeric mRNAs by reverse transcriptase-polymerase chain reaction for diagnosis and monitoring of acute leukemias with 11q23 abnormalities

Recurrent translocations involving chromosome band 11q23 are often found in human acute leukemias. Recently, the MLL gene on 11q23 and 10 partner genes involved in these translocations have been cloned and characterized. We performed a reverse transcriptase-polymerase chain reaction (RT-PCR) to detect the resultant der(11) chimeric mRNAs of the 3 types of 11q23 translocations including t(4;11), t(9;11), or t(11;19), in 14 leukemia patients with MLL gene rearrangements. At diagnosis or relapse, chimeric mRNA could be detected in all of the 4 patients with t(4;11), 2 of 3 with t(9;11), 2 of 3 with t(11;19), and 1 of 4 with unsuccessful karyotype. In 5 patients, we could monitor minimal residual disease (MRD) serially through the clinical course. One patient, in whom chi-meric mRNA was detected during complete remission (CR) just after the induction chemotherapy, relapsed within 2 months and died, while 2 patients in which chimeric mRNA was not detected remained in CR from 10-23 months. These findings suggest that RT-PCR is a useful approach for detecting which partner gene is involved in the translocation and monitoring MRD in patients with MLL gene rearrangement. Nonetheless, the clinical relevance of MRD evaluation by RT-PCR monitoring remains controversial. Long-term and prospective investigation of a larger series of patients is needed to confirm the clinical significance of monitoring MRD by RT-PCR method.

Is t(6;14) a non-random translocation in childhood acute mixed lineage leukemia?

We report a case of childhood acute mixed lineage leukemia (AMLL) with a translocation t(6;14)(q25;q32) as the main clonal abnormality. A comparison of this case with another one with similar cytogenetics and clinical findings may suggest that t(6;14)(q25;q32) is a non-random occurrence in childhood AMLL.

A t(9;11) translocation in childhood acute mixed leukemia

We present the case of a child with acute lymphoid leukemia (ALL) who was morphologically classified as FAB L1 (PAS and peroxidase were negative). Remission was achieved with an ALL-type protocol (GBTLI). Five months after the discontinuation of therapy, the patient presented mixed leukemia (CD10, CD19, CD13 and CD33 were positive) with t (9;11) (p21;q23) translocation. Unfortunately, as cytogenetic and immunophenotype studies were not performed at diagnosis, two possibilities could be considered for the relapse; secondary mixed leukemia with clonal chromosome changes, or mixed leukemia from the beginning.

Cytogenetic survey of 53 Moroccan patients with acute myeloblastic leukemia

We present a cytogenetic survey of chromosome aberrations for 53 Moroccan patients with acute myeloblastic leukemia (AML). Our 53 patients were 2 to 70 years old with 31 men and 22 women. The cytogenetic study was performed with the following three methods: first, relative proportion of normal (N) or abnormal (A) metaphases; second, presence of specific or random abnormalities; and third, karyotype complexity. Among 36 patients (67%) with a chromosomal abnormality, 18 (34%) showed a specific aberration. We have found t(9;22) in three patients (5%), chromosome 5 or 7 abnormality in six (11%), del(11)(q23) in three (6%), +21 in four (8%), and +8 in two (4%). Specific translocations associated with FAB type were found: t(8;21) with AML2 in 12 patients (23%) and t(9;11) with AML5 in one (2%). Rare abnormalities were also found: one patient with t(7;21) associated with AML2 and another patient with r(1) ring associated with AML1. We concluded that our study in a Moroccan population confirmed the relation between some specific abnormalities and the FAB classification. We have found a higher incidence for t(8;21) than usually described. Finally, we have identified chromosomal abnormalities t(7;21)(q22;p11) and r(1), rarely described before.

The biological significance of the multidrug resistance gene MRP in inversion 16 leukemias

Multidrug resistance represents an important mechanism by which leukaemic and solid tumour cells escape cell death after exposure to anthracyclines and other natural products. Acute myeloid leukaemia (AML) associated with the inversion chromosome 16: inv(16)(p13q22) has a favourable prognosis and is known to be chemosensitive. The inversion chromosome is seen in a number of FAB subclasses but is most commonly associated with acute myelomonocytic leukaemia with abnormal eosinophils, M4Eo. It results in the creation of a fusion between the myosin heavy chain gene (MYH11) on the short arm and the gene for a transcription factor, core binding factor beta (CBFB) on the long arm. In a subset of these inv(16) AML patients, inversion also results in loss of the gene for the multidrug resistance protein (MRP) at the short arm breakpoint. This gene maps to 16p13.13, centromeric to the primary short arm breakpoint, separated from MYH11 by a distance of approximately 150kb. Deletion of the MRP gene has been demonstrated by in situ hybridisation, gene dosage studies and by loss of heterozygosity of a flanking microsatellite marker (D16S405). Twenty two patients with inv(16) leukaemia were analysed for deletion of the MRP gene. Deletion of the gene was detected in seven patients, fourteen patients showed retention of the gene and in one case the findings were indeterminate. Clinical data from 13 of these patients were analysed revealing deletion of the MRP gene to be significantly associated with longer time from diagnosis until failure (death or relapse from complete remission) in these patients (p = 0.007). From this work and the growing literature concerning MRP, it appears likely that the deletion of an MRP allele, may favourably affect the biology of inv(16) AML and may have important prognostic implications.

Contribution of immunophenotypic and genotypic analyses to the diagnosis of acute leukemia

Diagnostic accuracy in acute leukemia (AL) can be improved if traditional morphology and cytochemistry are supplemented with immunophenotypic and genotypic analyses. This multiparameter approach is of crucial importance for the management of patients, as it enables the identification of leukemic syndromes with distinct biological features and response to treatment. Immunophenotyping using monoclonal antibodies has been universally accepted as a useful adjunct to morphological criteria. This technique is particularly valuable in diagnosing and subclassifying acute lymphoblastic leukemia and is also essential in certain types of acute myeloid leukemia (AML), such as AML with minimal differentiation or acute megakaryoblastic leukemia. Cytogenetic findings can be quite helpful in establishing the correct diagnosis and can add information of prognostic significance. A number of specific chromosomal abnormalities have been recognized that are very closely, and sometimes uniquely, associated with morphologically and clinically distinct subsets of leukemia. An even more basic understanding of normal and malignant hematopoietic cells has begun to evolve as molecular biology begins to unravel gene misprogramming by Southern and Northern blot analysis, the polymerase chain reaction, and fluorescence in situ hybridization. With the extensive use of these techniques it has become apparent that a proportion of leukemias exhibit the biologically relevant molecular defect in the absence of a karyotypic equivalent. On the other hand, apparently uniform chromosomal abnormalities such as the t(1;19) (q23;p13), t(9;22) (q33;q11), t(8;14) (q24;q32), or t(15;17) (q21;q21) may differ at the molecular level. Data collected from these modern technologies have introduced a greater complexity, which needs to be taken into consideration to improve both the diagnostic precision and the reproducibility of current classifications.

Characterization of a t(10;11)(p13-14;q14-21) in the monoblastic cell line U937

Previous analysis of the monoblastic cell line U937 has shown that several sublines contain a rearranged chromosome arm 11q. In order to determine the true nature of the rearrangement, fluorescence in situ hybridization (FISH) was carried out with various combinations of single copy anonymous markers, clones containing genes, a chromosome 10 paint, and an 11 centromere specific sequence. The rearrangement was deduced to be a reciprocal translocation between chromosomes 10 and 11 described as t(10;11)(p13-14;q14-21). The breakpoint on chromosome 11 is telomeric to the INT2 gene and the pHS11 probe at 11q13, and centromeric to the marker D11S36 localized to 11q14.3-q22.1 and the MLL gene at 11q23. Similar translocations have been reported in various acute leukemias, principally of the monocytic lineage, and also in T-cell precursor acute lymphocytic leukemias. Further characterization of the genetic rearrangements in U937 may lead to the isolation of genes important in leukemogenesis and provide an in vitro system for their study.