Amanda Faria de Figueiredo

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.

The acute myeloid leukemia (AML) subtype M4Eo occurs in 5% of all AML cases and is usually associated with either an inv(16)(p13.1q22) or a t(16;16)(p13.1;q22) chromosomal abnormality. At the molecular level, these abnormalities generate a CBFB-MYH11 fusion gene. Patients with this genetic alteration are usually assigned to a low-risk group and thus receive standard chemotherapy. AML-M4Eo is rarely found in infants. We describe clinical, conventional banding, and molecular cytogenetic data for a 12-month-old baby with AML-M4Eo and a chimeric CBFB-MYH11 fusion gene masked by a novel rearrangement between chromosomes 1 and 16. This rearrangement characterizes a new type of inv(16)(p13.1q22) masked by a chromosome translocation.

Secondary abnormalities involving 1q or 13q and poor outcome in high stage Burkitt leukemia/lymphoma cases with 8q24 rearrangement at diagnosis

Classical Burkitt lymphoma/leukemia (BL/L) presenting L3 morphology is found in 1% of childhood ALL. Recently, it has been described that secondary abnormalities could influence the prognosis of these patients. However, little information is available on these cytogenetic abnormalities and their prognostic importance in BL/L. Here, we report four new childhood BL/L cases associated with duplication within 1q or 13q, which exhibited a very unfavorable therapeutic response. We performed both classical and molecular cytogenetic analysis by multicolor chromosome banding of the secondary abnormalities involving the long arms of chromosome 1 or 13. These patients were previously treated with BFM-90 protocol. All of them died during or after the initial treatment. Here, for the first time, the exact breakpoints of the derivative chromosomes involved were determined at the cytogenetic level as 1q21 and 13q33 each.

A rare cryptic and complex rearrangement leading to MLL-MLLT10 gene fusion masked by del(10)(p12) in a child with acute monoblastic leukemia (AML-M5)

Acute myeloid leukemia (AML) in young children, defined as hose younger than 24 months of age, occurs in 3–5% of all peditric leukemias. Rearrangements involving the MLL gene, located n the 11q23 region, are between the most common cytogenetic berrations found in M4 or M5 AML subtypes. MLL rearrangement s highly heterogeneous with more than 60 different fusion parters described to date. An association between the type of MLL earrangement and prognosis has been reported [1]. Most of the MLL rearrangements result from simple reciproal translocations. However, rearrangements between MLL and LLT10 gene (also AF10) on chromosome 10p12 frequently result rom complex chromosomal rearrangement. Several types of chroosomal rearrangements involving three or more chromosomal reaks, such as inversions and insertions, have been reported. The atter occurs because MLL is transcribed from centromere to telomre and MLLT10 from telomere to centromere [2]. In some instances the accurate recognition of the t(10;11) via anding cytogenetics methods is difficult. Thus, more sophistiated molecular approaches such as multicolor fluorescence in situ ybridization (FISH), specific RT-PCR, and/or genomic PCR methds are required to uncover these MLL rearrangements, especially nusual, complex, and/or cryptic rearrangements [3,4]. Here, we escribe a rare case of cryptic insertion of chromosome 10 mateial in a derivative chromosome 11 in which the combination of everal molecular approaches was decisive to reveal the nature of complex and cryptic rearrangement leading to the MLL-MLLT10 ene fusion in a child with AML-M5.

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

BackgroundChildren 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.ResultsAn 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.ConclusionOur 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).

A complex karyotype masked a cryptic variant t(8;21)(q22;q22) in a child with acute myeloid leukemia

Cytogenetics Department, Bone Marrow Unit, The National Cancer Institute, Rio de Janeiro, RJ, Brazil, Jena University Hospital, Institute of Human Genetics, Jena, Germany, Stem Cell Department, Bone Marrow Unit, National Cancer Institute, Rio de Janeiro, RJ, Brazil, Pediatric Oncohematology Center, Oswaldo Cruz University Hospital, Recife, PE, Brazil, Service of Pediatric Oncohematology, Lagoa’s Hospital, Rio de Janeiro, RJ, Brazil, and Department of Oncology and International Outreach Program, St. Jude Children’s Research Hospital, Memphis, TN, USA

A unique set of complex chromosomal abnormalities in an infant with myeloid leukemia associated with Down syndrome

BackgroundChildren with Down syndrome (DS) have an enhanced risk of developing acute leukemia, with the most common subtype being acute megakaryoblastic leukemia (AMKL). Myeloid leukemia in Down syndrome (ML-DS) is considered a disease with distinct clinical and biological features. There are few studies focusing on the clonal cytogenetic changes during evolution of ML-DS.Case presentationHere, we describe a complex karyotype involving a previously unreported set of chromosomal abnormalities acquired during progression of ML-DS in an infant boy: derivative der(1)t(1;15)(q24;q23), translocation t(4;5)(q26;q33) and derivative der(15)t(7;15)(p21;q23). Different molecular cytogenetic probes and probesets including whole chromosome painting (WCP) and locus specific probes, as well as, multicolor-FISH and multicolor chromosome banding (MCB) were performed in order to characterize the chromosomal abnormalities involved in this complex karyotype. The patient was treated according to the acute myeloid leukemia-Berlin-Frankfurt-Munich-2004 (AML-BFM 2004) treatment protocol for patients with Down syndrome; however, he experienced a poor clinical outcome.ConclusionThe molecular cytogenetic studies performed, allowed the characterization of novel chromosomal abnormalities in ML-DS and possible candidate genes involved in the leukemogenic process. Our findings suggest that the complex karyotype described here was associated with the poor prognosis.

A yet unreported der(11)t(6;11)(p21;q21) included in a complex karyotype of a refractory anemia with ring sideroblasts and poor prognosis.

Refractory anemia with ring sideroblasts (RARS) is a subtype of myelodysplastic syndrome (MDS) [1]. RARS is associated with a relatively good prognosis; cytopenias are generally slow progressing and only 15% of the cases progress to acute leukemia. Cytogenetically, RARS is characterized mainly by isolated chromosomal abnormalities, and complex karyotypes are rare [1,2]. Here,we describe a yet unreported der(11)t(6;11)(p21;q21) in a 64-year-old man showing a complex karyotype and presenting with RARS; this complex karyotype was associated with a poor prognosis. Physical examination showed normal cardiorespiratory function and the absence of adeno visceromegalies. A blood count revealed anemia (hemoglobin 9.1 g/dl), thrombocytopenia (platelets 21 × 10/l), white blood cells 8.9 × 10/l and 4% blast cells. Myelogramanalysis showed an intense hypercellular pattern, hyperplasia, intense dyserythropoiesis and more than 90% ring sideroblasts. The diagnosis was MDS-RARS. The patient had a very poor outcome, evolving rapidly to acute myeloid leukemia (AML) followed by death one month later. Cytogenetic banding analysis showed a complex karyotype: 42,XY,-6,add(11)(q25),add(13)(p11),dic(15;21)(q10;q10), -17,-18,-21[7]/42,XY,del(3)(p21),-6, add(11)(q25),add(13)(p11), dic(15;21)(q10;q10),-17,-18,-21[2]/46,XY[2] (Fig. 1A). Fluorescence in situ hybridization (FISH) was performed using whole chromosome painting (WCP) probes for chromosomes 3, 6, 11, 13, 15, 17, 18 and 21 and partial chromosome painting (PCP) probes for 6q, 6p, 3p and 3q. FISH was also performed to investigate alterations in the mixed lineage leukemia (MLL) gene and in the ataxia telangiectasia mutated (ATM) genes. Multicolor banding (MCB) was performed for chromosomes 6, 11, 13, 15, 17 and 21, as previously reported [3]. Overall, the molecular cytogenetic analysis characterized the complex chromosomal alterations as follows: add(11)(q25) is a der(11)t(6;11)(11pter →11q21::6p12→6p21.3::6q12–6qter), add(13)(p11) is a dic(13;17) (17pter→17q25::13p11→13qter), del(3)(p21) could be redefined as der(3)(:p25→p21::p11→q11::q25→qter) and a part of chromosome 3 was involved in a more complex rearrangement with chromosome 17 as dic(3;17)(17qter→17p11.2::3p25→3p21::3p11→3q11::3q25 →3qter) dic(15;21) could be redefined as dic(15;21)(p11.2;p11.2). Patients with RARS represent 25% of all MDS cases in adult patients. The types of chromosomal abnormalities in RARS have been previously reported to be+8,−7, 20qand−5 [1]. The patient in this study had a very complex karyotype that has not yet been described in MDS. We used the advancedMulticolor Banding (MCB)methodology to characterize the chromosomal abnormalities and the breakpoints of these rearrangements. It was possible to observe that chromosome 11 had lost a part of its long arm (11q22–25) and the additional band belonged to chromosome 6 (Fig. 1B). In this chromosomal rearrangement, almost all of chromosome 6 was translocated to 11q. Chromosome 6 was broken in region p21.3 to q12 and lost the 6p22–23 region. Interestingly, chromosome 6 lost its centromere, most likely during the translocation.

An unusual cytogenetic rearrangement originating from two different abnormalities in chromosome 6 in a child with acute promyelocytic leukemia.

Acute promyelocytic leukemia (APL) is usually associated with a favorable outcome, but about 10% of patients tend to relapse. The genetic hallmark of APL is a balanced translocation involving chromosomes 15 and 17, and the PML-RARa gene fusion is found in more than 90% of these cases. Other chromosomal abnormalities are commonly found in APL, but their clinical significance has yet to be determined. Here we report a case of childhood APL that was studied by conventional cytogenetics along with molecular cytogenetic techniques. The patient showed a complex karyotype with an unusual cytogenetic rearrangement originating from two different abnormalities in a single chromosome 6. Our case is an exceptional example of a cryptic cytogenetic anomaly in APL and underscores the importance of detailed genetic characterization.

Molecular characterization of KMT2A fusion partner genes in 13 cases of pediatric leukemia with complex or cryptic karyotypes

In pediatric acute leukemias, reciprocal chromosomal translocations frequently cause gene fusions involving the lysine (K)‐specific methyltransferase 2A gene (KMT2A, also known as MLL). Specific KMT2A fusion partners are associated with the disease phenotype (lymphoblastic vs. myeloid), and the type of KMT2A rearrangement also has prognostic implications. However, the KMT2A partner gene cannot always be identified by banding karyotyping. We sought to identify such partner genes in 13 cases of childhood leukemia with uninformative karyotypes by combining molecular techniques, including multicolor banding FISH, reverse‐transcriptase PCR, and long‐distance inverse PCR. Of the KMT2A fusion partner genes, MLLT3 was present in five patients, all with acute lymphoblastic leukemia, MLLT1 in two patients, and MLLT10, MLLT4, MLLT11, and AFF1 in one patient each. Reciprocal reading by long‐distance inverse PCR also disclosed KMT2A fusions with PITPNA in one patient, with LOC100132273 in another patient, and with DNA sequences not compatible with any gene in three patients. The most common KMT2A breakpoint region was intron/exon 9 (3/8 patients), followed by intron/exon 11 and 10. Finally, multicolor banding revealed breakpoints in other chromosomes whose biological and prognostic implications remain to be determined. We conclude that the combination of molecular techniques used in this study can efficiently identify KMT2A fusion partners in complex pediatric acute leukemia karyotypes. Copyright