Temporal association of marrow eosinophilia with inversion of chromosome 16 in recurrent blast crises of chronic myelogenous leukemia

Coexistence of p210BCR-ABL and CBFβ-MYH11 fusion genes in myeloid leukemia: A report of 4 cases

Numerous acquired molecular and cytogenetic abnormalities are strongly associated with hematological malignancies. The breakpoint cluster region-ABL proto-oncogene 1 (BCR-ABL) rearrangement leads to a p210 chimeric protein in typical chronic myeloid leukemia (CML), whereas 17-25% of patients with acute lymphocytic leukemia and 0.9-3% patients with de novo acute myeloid leukemia (AML) carry a p190BCR-ABL fusion protein. Cases of patients with AML/CML carrying two specific primary molecular changes, BCR-ABL and core binding factor-β-myosin heavy chain 11 (CBFβ-MYH11) fusion genes have been rarely reported. The present study aimed to understand the nature and mechanism of this particular type of leukemia through case reports and literature review. A total of four patients who were diagnosed as AML/CML with BCR-ABL and CBFβ-MYH11 fusion genes in the First Affiliated Hospital of Soochow University (Suzhou, China) between January 2004 and December 2012 were examined. Morphological analysis of bone marrow cells, flow cytometry, quantitative polymerase chain reaction of p210BCR-ABL and CBFβ-MYH11 transcripts as well as cytogenetic and fluorescence in situ hybridization analyses were performed. A total of 4 patients who exhibited fusion of p210BCR-ABL and CBFβ-MYH11 were identified. A single patient (case 1) was first diagnosed CML-acute phase (AP), which progressed rapidly to CML-blast crisis (BC), and three patients (cases 2, 3 and 4) were diagnosed with AML with bone marrow eosinophilia at first presentation with no evidence of previous onset of CML. All cases achieved remission following conventional chemotherapy/hematological stem cell transplantation combined with the inhibitor of tyrosine kinase (TKI) maintenance therapy. The patients with CML carrying and expressing BCR-ABL and CBFβ-MYH11 fusion genes appeared more likely to rapidly progress to AP or BC. Therefore, the product of the CBFβ-MYH11 fusion gene may serve an important role in the transformation of CML. The co-expression of p210BCR-ABL and CBFβ-MYH11 fusion genes in myeloid leukemia may be a molecular event occurring not only during the development of CML, but also in AML.

Myeloid neoplasms with concurrent BCR-ABL1 and CBFB rearrangements: A series of 10 cases of a clinically aggressive neoplasm

Chronic myeloid leukemia (CML) is defined by the presence of t(9;22)(q34;q11.2)/BCR-ABL1. Additional chromosomal abnormalities confer an adverse prognosis and are particularly common in the blast phase of CML (CML-BP). CBFB rearrangement, particularly CBFB-MYH11 fusion resulting from inv(16)(p13.1q22) or t(16;16)(p13.1;q22), is an acute myeloid leukemia (AML)-defining alteration that is associated with a favorable outcome. The co-occurrence of BCR-ABL1 and CBFB rearrangement is extremely rare, and the significance of this finding remains unclear. We identified 10 patients with myeloid neoplasms harboring BCR-ABL1 and CBFB rearrangement. The study group included six men and four women with a median age of 51 years (range, 20-71 years). The sequence of molecular alterations could be determined in nine cases: BCR-ABL1 preceded CBFB rearrangement in seven, CBFB rearrangement preceded BCR-ABL1 in one, and both alterations were discovered simultaneously in one patient. BCR-ABL1 encoded for p210 kD in all cases in which BCR-ABL1 preceded CBFB rearrangement; a p190 kD was identified in the other three cases. Two patients were treated with the FLAG-IDA regimen (fludarabine, cytarabine, idarubicin, and G-CSF) and tyrosine kinase inhibitors (TKI); seven with other cytarabine-based regimens and TKIs, and one with ponatinib alone. At last follow up (median, 16 months; range 2-85), 7 of 10 patients had died. The co-existence of BCR-ABL1 and CBFB rearrangement is associated with poor outcome and a clinical course similar to that of CML-BP, and unlike de novo AML with CBFB rearrangement, suggesting that high-intensity chemotherapy with TKI should be considered in these patients.

BCR-ABL-positive acute myeloid leukemia: a new entity? Analysis of clinical and molecular features

BCR-ABL-positive acute myeloid leukemia (AML) is a rare subtype of AML that is now included as a provisional entity in the 2016 revised WHO classification of myeloid malignancies. Since a clear distinction between de novo BCR-ABL+ AML and chronic myeloid leukemia (CML) blast crisis is challenging in many cases, the existence of de novo BCR-ABL+ AML has been a matter of debate for a long time. However, there is increasing evidence suggesting that BCR-ABL+ AML is in fact a distinct subgroup of AML. In this study, we analyzed all published cases since 1975 as well as cases from our institution in order to present common clinical and molecular features of this rare disease. Our analysis shows that BCR-ABL predominantly occurs in AML-NOS, CBF leukemia, and AML with myelodysplasia-related changes. The most common BCR-ABL transcripts (p190 and p210) are nearly equally distributed. Based on the analysis of published data, we provide a clinical algorithm for the initial differential diagnosis of BCR-ABL+ AML. The prognosis of BCR-ABL+ AML seems to depend on the cytogenetic and/or molecular background rather than on BCR-ABL itself. A therapy with tyrosine kinase inhibitors (TKIs) such as imatinib, dasatinib, or nilotinib is reasonable, but-due to a lack of systematic clinical data-their use cannot be routinely recommended in first-line therapy. Beyond first-line treatment of AML, the use of TKI remains an individual decision, both in combination with intensive chemotherapy and/or as a bridge to allogeneic stem cell transplantation. In each single case, potential benefits have to be weighed against potential risks.

Coexistence of inversion 16 and the Philadelphia chromosome comprising P190 BCR/ABL in chronic myeloid leukemia blast crisis

A 63-year-old woman presented with leukocytosis (278 × 10(9)/L) with 72% blasts. Bone marrow blast cells showed cytogenetic abnormality with 46,XX, t(9;22), inv(16). Despite achievement of hematological remission by induction chemotherapy, Philadelphia chromosome did not disappear; chronic myeloid leukemia (CML) in blast crisis (BC) was thus diagnosed. The P190 BCR/ABL fusion transcript was detected. Imatinib mesylate introduced a hematological remission of short duration; however, infiltration into the central nervous system occurred, and the patient died 7 months after presentation. Coexistence of inv(16) and t(9:22) has been described in CML-BC and de novo AML, and CML-BC patients always carry P210 BCR/ABL, while de novo AML patients usually have P190 BCR/ABL. To the best of our knowledge, this is the first report of CML-BC with inv(16) and P190 BCR/ABL. We discuss this case with reference to the literature.

Inherited pericentric inversion of chromosome 16 in chronic phase of chronic myeloid leukaemia

The simultaneous occurrence of two specific acquired chromosomal abnormalities in chronic or acute leukaemias is rare. Inherited chromosomal abnormalities are also rare events in the general population. In chronic myeloid leukaemia (CML), characterised by the t(9;22)(q34;q11), the inv(16)(p13q22) has been described associated with the acceleration of disease or onset of blast crisis. We report on a patient with chronic phase of CML and both acquired t(9;22)(q34;q11) and inherited inv(16)(p13q22), who obtained a complete remission of the disease after bone marrow transplant. Therefore, it is worth to comment that an additional chromosomal abnormality in disease does not obligatory mean transformation of the disease to a more aggressive form, since chromosomal abnormalities are also seen in normal individuals.

Pathogenesis of acute myeloid leukaemia and inv(16)(p13;q22): a paradigm for understanding leukaemogenesis?

Acute myeloid leukaemia (AML) has been proposed to arise from the collaboration between two classes of mutation, a class I, or proliferative, mutation and a class II, or blocking, mutation. A limitation of this so-called 'two-hit' hypothesis has been the lack of identifiable proliferative and blocking mutations in most AML cases. However, it is now known that the CBFbeta-MYH11 fusion gene in AML and inv(16), by disrupting the normal transcription factor activity of core binding factor (CBF), functions as a class II mutation. In addition, nearly 70% of patients with AML and inv(16) are known to possess mutually exclusive mutations of the receptor tyrosine kinases (RTKs), c-KIT and FLT3, as well as RAS genes, that provide a class I, or proliferative, signal. AML and inv(16), therefore, is one of the best understood of the acute leukaemias at the genetic level and so provides a paradigm for the 'two-hit' hypothesis of leukaemogenesis. This paper reviews the recent advances in the molecular pathology of AML and inv(16) and discusses possible therapeutic implications of the current pathogenetic model.

Lymphoid blastic crisis of chronic myelogenous leukaemia with inv(16)(p13;q22)

We report a case of chronic myelogeneous leukaemia (CML) in B-lineage lymphoid blastic crisis (BC) having chromosome abnormality, inv(16)(p13;q22) in addition to Philadelphia chromosome, in 20/20 marrow metaphase. Inv(16)(p13;q22) was not observed in cells of chronic phase or accelerate phase. Abnormalities of chromosome 16, including inv(16)(p13;q22), del(16)(q22) and t(16;16)(p13;q22), have been reported mostly in acute myelomonocytic leukaemia (AML), (FAB M4-Eo), and some in CML-BC and myelodysplastic syndrome (MDS) cases. Most of the cases showed increase of myelomonocytic components and abnormal eosinophils with dysplastic granules in the bone marrow (BM). However, our case was diagnosed as lymphoid BC without increase of myelomonocytic components, although some abnormal eosinophilia was seen. To date, lymphoid BC of CML having inv(16)(p13;q22) abnormality has not been reported. The case presented here could be a clue to understand the pathophysiology of inv(16)(p13;q22) leukaemia.

Clinical syndromes of transformation in clonal hematologic disorders

The majority of clonal hematologic syndromes, including lymphoproliferative, myeloproliferative, and myelodysplastic disorders, tend to undergo transformation. However, the frequency of transformation varies widely. For example, transformation is almost invariable in chronic myelogenous leukemia, but it is infrequent in other myeloproliferative disorders. Similarly, transformation occurs in approximately 33% of follicular lymphomas but less commonly in other lower-grade lymphomas. At a genetic level, although some secondary lesions are seen across the spectrum of transformation syndromes (such as loss of function of p53 and p15/p16), there is considerable intra- and interdisease variability, with no common denominator. This review of the literature will discuss these transformations, noting their frequency, pathologic changes observed, clinical syndromes described, underlying genetic correlates, and prognostic and therapeutic implications.

Inversion of chromosome 16 in accelerated phase of chronic myeloid leukaemia: report of a case and review of the literature

A patient with a Philadelphia chromosome-positive (Ph+) chronic myeloid leukemia (CML) developed a blast crisis (FAB subtype AML-M2) without a monocytic involvement. Karyotype showed the presence of inv(16)(p13;q22) in addition to Ph, in 16/20 marrow metaphases.

Detection of a dup(17q) and inv(16) by fluorescence in situ hybridization in acute myelomonocytic leukemia

Two cases of acute myelomonocytic leukemia (AMMoL) of FAB type M4Eo are described in which a primary subclone containing a dup(17)(q21q25) and a subclone containing dup(17)(q21q25), inv(16)(p13q22) were seen in one patient, and -7, dup(17)(q21q25) in another. Fluorescence in situ hybridization (FISH) was carried out for the confirmation of the duplicated segment and breakpoint of inv(16). Inv(16) is a well known anomaly in AMMoL, whereas dup(17q) is rare though as not yet confirmed, this anomaly could be a nonrandom or novel change in AMMoL.

Identification of the chimeric protein product of the CBFB-MYH11 fusion gene in inv(16) leukemia cells

An expressed gene formed by fusion between the CBFB transcription factor gene and the smooth muscle myosin heavy chain gene MYH11 is consistently detected by reverse transcription polymerase chain reaction (RT-PCR) in patients who have acute myeloid leukemia (AML) subtype M4Eo with an inversion of chromosome 16. We have previously shown that a CBFB-MYH11 cDNA construct can produce a chimeric protein and transform NIH 3T3 cells. However, the presence of the chimeric protein in patient cells has not been demonstrated previously. Here, we show that such chimeric proteins can be identified in vivo, primarily in the nuclei of the leukemic cells, by use of antibodies against the C-terminus of the smooth muscle myosin heavy chain and the fusion junction peptide. A very high molecular weight protein/DNA complex is generated when nuclear extracts from patient cells are used in electrophoretic mobility shift assays, as seen in NIH 3T3 cells transfected with the CBFB-MYH11 cDNA. Immunofluorescence staining shows that the proteins are organized in vivo into novel structures within cell nuclei. One isoform of the transcript of the CBFB-MYH11 fusion gene, containing the MHC204 C-terminus, was the predominant from in all five cases studied.