Monosomy 20: a nonrandom finding in childhood acute lymphoblastic leukemia

An acquired stable variant of a dicentric dic(9;20) and complex karyotype in a Syrian childhood B-acute lymphoblastic leukemia case

BACKGROUND

About 25 years ago, the acquired chromosome abnormality dicentric dic(9;20)(p11 ~ 13;q11) was seen described as a non-random aberration in B-cell precursor acute lymphoblastic leukemia (BCP-ALL). Yet, about 200 cases were reported. However, dicentric dic(9;20) is a subtle abnormality which easily may be mixed up with monosomy 20 and/or del(9p). The dicentric dic(9;20) can be found as a sole chromosomal abnormality or can be masked within complex rearrangements; also, a dicentric dic(9;20) is often associated with mono- or biallelic loss of CDKN2A gene.

CASE PRESENTATION

Here we report a case of 16-year-old male diagnosed with a de novo pre-B-ALL. Molecular approaches (array-based multicolor banding (aMCB) and array comparative genomic hybridization (aCGH)) were applied, and a unique complex karyotype involving six chromosomes was identified. It included three previously unreported chromosomal aberrations: dicentric dic(9;20;X), deletion del(7)(p22.2p15.2) and dicentric dic(7;13). The dicentric dic(9;20;X) also led to monoallelic loss of tumor suppressor gene CDKN2A. After successful chemotherapeutic treatment the patient experienced a relapse with a secondary ALL without complex karyotype but a deletion del(19)(p13). Unfortunately, the patient died after 17 months of the initial diagnosis.

CONCLUSIONS

To the best of our knowledge, a comparable childhood ALL associated with such complex karyotype and deletion del(19)(p13) in secondary ALL was not previously reported. Thus, the complex karyotype with dicentrc dic(9;20;X) seems to indicate for a poor prognosis.

Characterisation of dic(9;20)(p11?13;q11) in childhood B-cell precursor acute lymphoblastic leukaemia by tiling resolution array-based comparative genomic hybridisation reveals clustered breakpoints at 9p13.2 and 20q11.2

Although the dic(9;20)(p11-13;q11) is a recurrent chromosomal abnormality in paediatric B-cell precursor acute lymphoblastic leukaemia (BCP ALL), occurring in approximately 2% of the cases, its molecular genetic consequences have not been elucidated. In the present study, high-resolution genome-wide array-based comparative genomic hybridisation (array-CGH) and fluorescence in situ hybridisation (FISH) were used to characterise the 9p and 20q breakpoints (BPs) in seven childhood BCP ALLs with dic(9;20), which was shown to be unbalanced in all of them, resulting in loss of 9p13.2-pter. Five of the cases had loss of 20q11.2-qter, whereas two displayed gain of 20cen-pter. All BPs on 9p clustered in a 1.5 Mb segment of the sub-band 9p13.2; in three of the cases, the 20q BPs mapped to three adjacent clones covering a distance of 350 kb at 20q11.2. Thus, the aberration should be designated dic(9;20)(p13.2;q11.2). One of the ALLs, shown to have a complex dic(9;20), was further investigated by FISH, revealing a rearrangement of the haemapoietic cell kinase isoform p61 (HCK) gene at 20q11. The disruption of HCK may result in a fusion gene or in loss of function. Unfortunately, lack of material precluded further analyses of HCK. Thus, it remains to be elucidated whether dic(9;20)(p13.2;q11.2) leads to a chimaeric gene or whether the functionally important outcome is loss of 9p and 20q material.

Cytogenetic and fluorescence in situ hybridization analyses of hematologic malignancies in Korea

Cytogenetic analysis was performed in 86 cases of hematologic malignancy, using conventional cytogenetic analysis and fluorescence in situ hybridization (FISH) analysis at two university hospitals in Korea between 1993 and 1995. In addition to well-known anomalies, some unusual abnormalities were found, such as t(17;22), trisomy 9 combined with t(14;17), (2;7) and Philadelphia chromosome in CML; t(1;12), t(11;22), t(9;17), and t(12;21) in AML; trisomy 11 in MDS; t(2;9) and complex t(8;8;13;14) in ALL. The results of FISH analysis in interphase nuclei using a translocation probe for CML and APL showed more than 85% positive cells in CML, and 75% positive cells in APL.

Dicentric (9;20)(p11;q11) identified by fluorescence in situ hybridization in four pediatric acute lymphoblastic leukemia patients

Four children with acute lymphocytic leukemia (ALL) and a dic(9;20) are described. All four patients were diagnosed with pre-B-cell All, and the three for whom information was available were CD10+. Age at diagnosis ranged from 23 months to 12 years. All patients achieved remission, with two in continuous remission for 2 years 6 months and 3 years, one patient relapsed, dying 3 years 2 months after diagnosis, and one patient was lost to follow-up. These four patients were initially diagnosed as having a deletion of 9p and loss of one chromosome 20. Re-examination of the karyotypes indicated a possible dic(9;20). The dicentric chromosome was verified using dual-color fluorescence in situ hybridization (FISH) with centromeric probes for chromosomes 9 and 20 on interphase nuclei. Three of the four patients had multiple chromosomal abnormalities in addition to the translocation; one was hypodiploid, one was pseudodiploid, and two were hyperdiploid. This dicentric chromosome was recently described in four adult and nine pediatric patients with ALL [8, 9]. All reported patients had CD10+ pre-B-cell All, and achieved remission, as was the case for our four pediatric dic(9;20) patients. Two of our three patients for whom follow-up is available are in continuous remission as were two adults and five pediatric patients in the previous reports. These studies confirm the dic(9;20) as a recurring abnormality in ALL. Due to the subtle nature of the translocation, FISH is very useful in confirming the chromosomal abnormality.

Acute lymphoblastic leukemia. A comprehensive review with emphasis on biology and therapy

BACKGROUND

Acute lymphoblastic leukemia (ALL) is the most common malignancy in children. It is now curable in 60-70% of children. Most of the current understanding of the biology and treatment of ALL originates from studies of children. In adults, although much progress has been achieved, ALL is curable in only 20-35% of patients.

METHODS

A review of the biology and treatment of ALL from the English literature was performed.

RESULTS

Immunophenotypic and cytogenetic analyses of ALL have contributed to a more rational classification of ALL. These analyses have identified subgroups with poor prognosis or with different therapeutic requirements. Overall, 60-70% of adults with ALL have poor prognostic features, including older age, a high leukocyte count, non-T-cell immunophenotype, Ph-positive genotype, and longer time to achieve a complete remission. These patients have a cure rate of 20-25%, whereas those without these risk factors, have a 60-70% probability of survival. The use of more intensive induction regimens with growth factor support may improve survival rates. Also, intensive consolidation-intensification may improve survival rates. Most patients benefit from maintenance therapy, but the dose schedule must be optimized. Central nervous system (CNS) prophylaxis is beneficial, particularly for patients with a high risk for CNS relapse and when introduced early during induction of remission. Patients with high risk characteristics may benefit from allogeneic bone marrow transplantation (BMT) during first remission, and all other patients may benefit from it during first or subsequent relapse. Autologous BMT may be a valuable option for poor compliant patients.

CONCLUSIONS

Although the prognosis of patients with ALL has improved markedly during the past decades, newer strategies, including more dose-intensive therapy, the search for new drugs, and more target-specific therapy, are needed to improve the current cure rates.

Presenting characteristics of trisomy 8 as the primary cytogenetic abnormality associated with childhood acute lymphoblastic leukemia. A Pediatric Oncology Group (POG) Study (8600/8493)

Although trisomy 8 is the single most common numerical abnormality in acute myeloid leukemia (AML), relatively few cases with acute lymphoblastic leukemia (ALL) and trisomy 8 have been reported. We report the clinical and laboratory features of seven children with ALL and trisomy 8 as the sole cytogenetic abnormality and review nine similar cases from the literature. Among the children studied by the Pediatric Oncology Group (POG) with newly diagnosed ALL, only 0.3% had trisomy 8 as the sole abnormality. Four of our patients had T-cell ALL and three had early pre-B ALL. Presenting clinical features were typical for the respective immunophenotypes. Six of the seven children achieved complete remission. Our study suggest that trisomy 8 is an infrequent, recurring abnormality among children with ALL, which appears to be associated with a T-cell immunophenotype.

Monosomy 20 in childhood acute lymphoblastic leukemia

We report two cases of acute lymphoblastic leukemia (ALL) with loss of chromosome 20 as the only karyotypic abnormality detected in the blast cells. The first patient is a 12-year-old boy studied at diagnosis. He represents the only case of monosomy 20 in our series of 90 pediatric ALL successfully karyotyped at diagnosis. In the second patient, monosomy 20 was detected at the second hematologic relapse, 12 years after the initial diagnosis; cytogenetic studies were not performed at disease onset.