Banding and molecular cytogenetic studies detected a CBFB-MYH11 fusion gene that appeared as abnormal chromosomes 1 and 16 in a baby with acute myeloid leukemia FAB M4-Eo

Complex karyotype defined by molecular cytogenetic FISH and M-FISH in an infant with acute megakaryoblastic leukemia and neurofibromatosis

Acute myeloid leukemia in childhood is a heterogeneous group of diseases, and different epidemiologic factors are involved in the etiopathogenesis. Genetic syndromes are one of the predisposing factors of acute myeloid leukemia (AML), including Down syndrome, Bloom syndrome, and neurofibromatosis. Acute megakaryoblastic leukemia (AMKL) is the main subtype in Down syndrome infants, and acquired chromosomal anomalies are closely related to the physiopathology of the illness. The main chromosomal anomalies in AMKL are structural, such as t(1;22); however, complex karyotypes are also common. Here we describe the case of an infant with neurofibromatosis developing AMKL with a complex karyotype including 5q and 17q deletions, TP53 deletion, and an unusual unbalanced chromosomal translocation t(11;19)(q13;p13), leading to three copies of the MLL gene.

Molecular cytogenetic studies characterize a near-triploid complex karyotype in a child with acute lymphoblastic leukemia

High hyperdiploidy with modal chromosome numbers between 50 and 65 is common in childhood acute lymphoblastic leukemia (ALL), occurring in 25-30% of the cases. This chromosomal constitution is associated with a very good prognosis. By contrast, near triploidy and tetraploidy are found in <1% of childhood ALL. Given the sparseness of this group, the associated chromosomal abnormalities and their prognostic implications have not yet been studied in detail. Here, we describe clinical and molecular cytogenetic findings in a child with ALL who had a near-triploid complex karyotype, with loss and gain of chromosomes, including extra copies of the same derivative chromosomes. These findings suggest a random nondisjunction mechanism for near triploidy in the present case.

A case of childhood acute myeloid leukemia AML (M5) with a neocentric chromosome neo(1)(qter-->q23 approximately 24::q23 approximately 24-->q43-->neo-->q43-->qter) and tetrasomy of chromosomes 8 and 21

Hyperdiploidy is rarely observed in childhood acute myeloid leukemia (AML). Described here is the case of a 2(1/2)-year-old girl with AML-M5 and 51 chromosomes characterized by double tetrasomy of chromosomes 8 and 21 and also a neocentric derivative chromosome neo(1)(qter-->q23 approximately 24::q23 approximately 24-->q43-->neo-->q43-->qter). Little is known about the prognostic significance of these chromosomal abnormalities in childhood AML. In the actual case, complete remission was achieved after chemotherapy, which continued for 7 months. No acquired neocentric chromosome 1 has been described previously, even though neocentromere formation has been reported for other chromosomes in neoplasms.

Unbalanced chromosome 1 abnormalities leading to partial trisomy 1q in four infants with Down syndrome and acute megakaryocytic leukemia

Background

Children with Down syndrome (DS) have an increased risk of childhood acute leukemia, especially acute megakaryoblastic leukemia (AMKL) also called acute myeloid leukemia (AML) type M7. Here four yet unreported infants with such malignancies are reported.

Results

An unbalanced translocation involving chromosome 1 was identified by GTG banding in all cases. These were characterized in more detail by molecular cytogenetic approaches. Additional molecular analysis revealed in three of the four cases mutations in exon 2 of the GATA binding protein 1 (globin transcription factor 1), located in Xp11.23.

Conclusion

Our results corroborate that abnormalities of chromosome 1 are common in DS-associated AMKL. Whether this chromosomal region contains gene(s) involved in hematopoietic malignant transformation remains to be determined.

A new chromosomal three-way rearrangement involving MLL masked by a t(9;19)(p11;p13) in an infant with acute myeloid leukemia

Infants diagnosed with acute myelogenous leukemia (AML) are likely to have subtypes M4 or M5 characterized by 11q23 abnormalities like a t(9;11)(p22;q23). Detection of all possible types of chromosomal abnormalities, including mixed lineage leukemia (MLL) gene rearrangements at 11q23, is of importance for the identification of biological subgroups, which might differ in drug resistance and/or clinical outcome. Here, we report the clinical, conventional banding and molecular cytogenetics data of a 6-month-old boy with an AML-M5 presenting with a unique cryptic rearrangement involving the MLL gene: a three-way t(9;19;11)(p11.2;p13.1;q23).

Advances in molecular genetics and treatment of core-binding factor acute myeloid leukemia

PURPOSE OF REVIEW

Core-binding factor (CBF) acute myeloid leukemia (AML) is among the most common cytogenetic subtypes of AML, being detected in approximately 13% of adults with primary disease. Although CBF-AML is associated with a relatively favorable prognosis, only one-half of the patients are cured. Herein we review recent discoveries of genetic and epigenetic alterations in CBF-AML that may represent novel prognostic markers and therapeutic targets and lead to improvement of the still disappointing clinical outcome of these patients.

RECENT FINDINGS

Several acquired gene mutations and gene-expression and microRNA-expression changes that occur in addition to t(8;21)(q22;q22) and inv(16)(p13q22)/t(16;16)(p13;q22), the cytogenetic hallmarks of CBF-AML, have been recently reported. Alterations that may represent cooperative events in CBF-AML leukemogenesis include mutations in the KIT, FLT3, JAK2 and RAS genes, haploinsufficiency of the putative tumor suppressor genes TLE1 and TLE4 in t(8;21)-positive patients with del(9q), MN1 overexpression in inv(16) patients, and epigenetic and posttranscriptional silencing of CEBPA. Genome-wide gene-expression and microRNA-expression profiling identifying subgroups of CBF-AML patients with distinct molecular signatures, different clinical outcomes, or both, have also been reported.

SUMMARY

Progress has been made in delineating the genetic basis of CBF-AML that will likely result in improved prognostication and development of novel, risk-adapted therapeutic approaches.