Inversion-associated translocations in acute myelomonocytic leukemia with eosinophilia

Spectral karyotyping and fluorescence in situ hybridization analyses identified a novel three-way translocation involving inversion 16 in therapy-related acute myeloid leukemia M4eo

We report a novel three-way translocation involving inversion 16 and chromosome 12 at bands 16p13, 16q22, and 12q24 in a patient with therapy-related acute myeloid leukemia (AML)-M4eo. Conventional G-banding of bone marrow cells at diagnosis was suggestive of inv(16)(p13q22) and a translocation of chromosomes 12 and 16. The presence of inv(16) was confirmed by reverse-transcription polymerase chain reaction (RT-PCR) analysis, which corresponded to the type A CBFB-MYH11 chimeric transcript. Spectral karyotyping (SKY) analysis clearly identified a reciprocal translocation between chromosomes 12 and 16. In addition, dual-color fluorescence in situ hybridization (FISH) analysis revealed a fusion signal for the CBFB and MYH11 probes and a signal for the MYH11 probe on the der(16) chromosome, as well as a signal for the CBFB probe on the der(12) chromosome. Thus, the karyotype was refined to 46,XX,der(12)t(12;16)(q24;q22),der(16)inv(16)(p13q22)t(12;16). Although we could not establish that this complex chromosomal aberration occurred either as a one-step, three-way event, or a sequential event with inv(16)(p13q22) followed by t(12;16)(q24;q22), SKY in combination with FISH and RT-PCR analyses successfully detected this complex chromosome abnormality in the patient.

Chromosome 16 inversion-associated translocations in acute myeloid leukemia elucidated using a dual-color CBFB DNA probe

We describe two cases of acute myelomonocytic leukemia with eosinophilia (AML-M4Eo) that were diagnosed with an inv(16)(p13q22) based on conventional cytogenetics (CC) and fluorescence in situ hybridization (FISH) technique using a chromosome 16p arm specific paint probe. Additional FISH analysis with a dual-color CBFB DNA probe showed that the 3' portion of the CBFB gene was translocated to chromosome 10p13 in the first patient and 1p36 in the other. These two cases indicate that some inv(16)(p13q22) identified by CC and FISH with chromosome arm-specific painting probe may represent cases of inversion-associated translocation. We suggest that all cases with inv(16)(p13q22) should be investigated by FISH with appropriate probes for a possible translocation of 16q22-->qter to another chromosome.

Genetic profile of acute myeloid leukemia

Understanding genomic events and the cascade of their effects in cell function is crucial for identifying distinct subsets of acute myeloid leukemia and developing new therapeutic strategies. Conventional cytogenetics, fluorescence in situ hybridization investigations and molecular studies have provided much information over the past few years. This review will focus on major genomic mechanisms in acute myeloid luekemia and on the genes implicated in the pathogenesis of specific subtypes.

A novel variant three-way translocation of inversion 16 in a case of AML-M4eo following low dose methotrexate therapy

We report a case of acute myelomonocytic leukemia with eosinophilia (AML-M4eo) in a 65-year-old man following low dose methotrexate treatment for pemphigus vulgaris. Cytogenetic studies at diagnosis revealed a complex karyotype including a reciprocal translocation between 11q14.2 and 16q22, an inversion of chromosome 16(p13.1q22), and an apparently terminal deletion of 7q31. The presence of inv(16) was confirmed by reverse transcription-polymerase chain reaction which demonstrated a Type A fusion transcript derived from the core binding factor (CBF) beta and the smooth muscle myosin heavy chain (MYH11) genes. The patient was in complete hematologic and cytogenetic remission 6 months following intensive chemotherapy. Because AML-M4eo with inv(16) has a favorable prognosis, molecular studies should be performed in case the identification of inv(16) by conventional cytogenetics is difficult due to a complex karyotype.

CALM-AF10 fusion gene in leukemias: simple and inversion-associated translocation (10;11)

A translocation (10;11)(p12;q14) was observed in two children, one with acute eosinophilic leukemia and the other with acute T-cell lymphoblastic leukemia. The presence of CALM-AF10 fusion was ascertained by reverse transcriptase-polymerase chain reaction (RT-PCR) analysis. Fluorescence in situ hybridization (FISH) analysis showed that AF10 gene splitting was associated with partial inversion of chromosome 11 in the first patient. In addition, FISH analysis also determined the orientation of the CALM gene, 5' telomere to 3' centromere on 11q.

Uneven frequencies of secondary chromosomal abnormalities in acute myeloid leukemias with t(8;21), t(15;17), and inv(16)

The types and incidences of secondary chromosomal abnormalities were analyzed in three subtypes of leukemia with recurrent abnormalities, translocations t(8;21), t(15;17), and inversion inv(16). The main types of clonal secondary abnormalities were similar to those described in the literature, loss of sex chromosome associated with t(8;21), trisomy 8 with t(15;17), and trisomies 8 or 22 with inv(16). On the whole, the incidence of clonal abnormalities was significantly higher in t(8;21) leukemia than in the two other subtypes. This difference was not related to a chromosomal instability peculiar to this leukemia subtype, because the incidence of nonclonal abnormalities was the same in the three types of leukemia studied. The significance of secondary clonal abnormalities remains speculative. A careful comparative analysis of structural rearrangements of the chromosomes usually involved in secondary abnormalities must be carried out as a first step to identify the key genes altered.

Fluorescence in situ hybridization identifies inversion 16 masked by t(10;16)(q24;q22), t(7;16)(q21;q22), and t(2;16)(q37;q22) in three cases of AML-M4Eo

Bone marrow or peripheral blood from three patients had a t(10;16)(q24;q22), t(7;16) (q21;p13.1), and t(2;16)q37;q22), respectively. In all cases, fluorescence in situ hybridization confirmed an inv(16) masked by the translocation. The three patients were diagnosed with acute myelomonocytic leukemia and increased eosinophils. Because inv(16) has a favorable prognosis, identification of masked inv(16) will promote improved management of these cases. Therefore, all cases that have atypical rearrangement of chromosome 16 should be investigated for a possible inversion.

Chromosome 16 inversion-associated translocation: two new cases

Two patients with chromosome 16 inversion-associated translocation were studied with conventional cytogenetic and fluorescence in situ hybridization (FISH) techniques. The same chromosome 16 was involved in inversion and translocation in both patients. The chromosome translocation breakpoint was located within the heterochromatin of chromosome 16 but outside the alpha satellite domain in the t(10;16) of the first patient, whereas it was outside the heterochromatin area in the second case with t(1;16). These two types of rearrangements may be due to different mechanisms and illustrate the possible difficulties in recognizing the chromosome 16 inversion without FISH studies.

Variant three-way translocation of inversion 16 in AML-M4Eo confirmed by fluorescence in situ hybridization analysis

The inv(16) and t(16;16) characterize a subgroup of acute myelomonocytic leukemia (AML) with distinct morphological features and a favorable prognosis. Both cytogenetic abnormalities result in a fusion of CBF beta at 16q22 and MYH11 gene at 16p13, whose detection by PCR and fluorescence in situ hybridization (FISH) is useful for diagnosis and monitoring of the disease. Variant translocations of inv(16)/t(16;16) are very rare and whether they are also associated with a favorable prognosis is unknown. We report a patient presenting with typical AML-M4Eo and a three-way translocation of inv(16) involving 16p13, 16q22, and 3q22. FISH studies on bone marrow (BM) chromosomes using CBFB and MYH11 DNA probes revealed a fusion of CBFB and MYH11 on 16q of the der(16), as well as a signal from MYH11 on 16p but not from CBFB; normal signals for both probes were present on the normal 16. Neither of these labeled probes was on the der(3), but the translocation between the der(3) and der(16) was confirmed by using a chromosome 16 painting probe. Molecular analysis of BM cells using RT-PCR identified a CBFB-MYH11 fusion transcript type D. After achieving complete remission, the patient relapsed. We conclude that FISH and PCR are feasible tools to distinguish cases with variant abnormalities of inv(16) from cases with other chromosome 16 abnormalities. Variant abnormalities of inv(16) may be not associated with favorable prognosis.

FISH identifies inv(16)(p13q22) masked by translocations in three cases of acute myeloid leukemia

The inv(16)(p13q22) masked by different translocations was detected by fluorescence in situ hybridization (FISH) and confirmed by molecular analysis in three adult patients presenting with acute myeloid leukemia (AML)-M2 (cases 1 and 3) and M4Eo (case 2). Cytogenetic analysis revealed 47,XX,t(9;16)(p23;p13),+22 (case 1); 46,XX,t(1;16)(p32;p13) (case 2); and 46,XY,?del(16)(q22) (case 3). Using a panel of probes for chromosomes 1, 9, 16, and 20 as well as probes to detect inv(16), i.e., two cosmid contigs hybridizing proximally and distally to the 16p13 breakpoint, FISH demonstrated inv(16) involving the derivative 16 as well as reciprocal translocations between 16q22-qter and 9p24 (case 1), 1p32 (case 2), and 20q13 (case 3). In addition, a small interstitial del(16)(p13p13) proximal to the MYH11 breakpoint was detected in case 1. Reverse transcriptase-polymerase chain reaction (RT-PCR) and Southern blot analysis showed a CBFB-MYH11 fusion transcript and MYH11 rearrangement, respectively, in all three cases. We conclude that: 1) inv(16) can be masked by other structural abnormalities involving chromosome 16; 2) some of the so-called variant translocations not explored at the molecular level may in fact represent a masked inv(16); and 3) FISH, RT-PCR, and Southern blot analyses are reliable tools to detect masked inv(16) and should be applied in all AML cases with structural changes of chromosome 16.

Cohabiting t(12;22) and inv(3) primary rearrangements in an acute myelomonocytic leukemia (FAB M4) cell line

We describe the cytogenetic characterization of MUTZ-3, the first continuous cell line to be established from acute myelomonocytic leukemia (FAB M4) cells, exhibiting recurrent chromosomal rearrangements associated with this disease category. MUTZ-3 was established from peripheral blood taken at presentation from a 29-year-old male patient and carries the t(12;22)(p13.2;q11.2) associated with acute myelomonocytic leukemia (AMMoL), the inv(3)(q21.2q26.3) associated with multilineage acute myeloid leukemias (AML), and the inv(7)(p 14q35) associated with ataxia telangiectasia (A-T). There was no evidence that the patient was an A-T heterozygote. The breakpoint on chromosome 22 mapped between 5' BCR and D22S39, consistent with the G-banding assignment. Both inversions were translocation-associated and may be further examples of an association previously described in AML FAB M4eo with inv(16). We suggest that the combination of inv(3)/t(3;3) with t(12;22) may represent a new, nonrandom association in AML.