A case of acute monocytic leukemia with t(11;17) involving a rearrangement of MLL-1 and a region proximal to the RARA gene

Monocytic Acute Myeloid Leukemias with KM2TA Translocations to Chromosome 17q that May Clinically Mimic Acute Promyelocytic Leukemia

OBJECTIVE

Acute promyelocytic leukemia (APL) with variant RARA translocation, eg, t(11;17), is not sensitive to all-trans retinoic acid and requires distinct chemotherapy. However, there are some leukemic entities that may mimic aspects of the clinical and/or laboratory picture of APL and cause confusion because of karyotype nomenclature. Therefore, recognition of such entities may be of therapeutic and prognostic significance.

METHODS

We present 2 cases of acute myeloid leukemia (AML) with t(11;17) that were clinically concerning for APL based primarily on clinical presentation but were ultimately diagnosed as AML with monocytic differentiation.

RESULTS

Both leukemias harbored KMT2A translocations, one located near but not involving RARA and the other with SEPT9.

CONCLUSION

In leukemias that clinically and/or immunophenotypically mimic APL, identification of specific gene translocations can lead to the correct diagnosis and may carry therapeutic/prognostic implications.

Bioinformatic prediction and functional characterization of human KIAA0100 gene

Our previous study demonstrated that human KIAA0100 gene was a novel acute monocytic leukemia-associated antigen (MLAA) gene. But the functional characterization of human KIAA0100 gene has remained unknown to date. Here, firstly, bioinformatic prediction of human KIAA0100 gene was carried out using online softwares; Secondly, Human KIAA0100 gene expression was downregulated by the clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated (Cas) 9 system in U937 cells. Cell proliferation and apoptosis were next evaluated in KIAA0100-knockdown U937 cells. The bioinformatic prediction showed that human KIAA0100 gene was located on 17q11.2, and human KIAA0100 protein was located in the secretory pathway. Besides, human KIAA0100 protein contained a signalpeptide, a transmembrane region, three types of secondary structures (alpha helix, extended strand, and random coil) , and four domains from mitochondrial protein 27 (FMP27). The observation on functional characterization of human KIAA0100 gene revealed that its downregulation inhibited cell proliferation, and promoted cell apoptosis in U937 cells. To summarize, these results suggest human KIAA0100 gene possibly comes within mitochondrial genome; moreover, it is a novel anti-apoptotic factor related to carcinogenesis or progression in acute monocytic leukemia, and may be a potential target for immunotherapy against acute monocytic leukemia.

Molecular dissection of t(11;17) in acute myeloid leukemia reveals a variety of gene fusions with heterogeneous fusion transcripts and multiple splice variants

The majority of translocations that involve the long arms of chromosomes 11 and 17 in acute myeloid leukemia appear identical on the cytogenetic level. Nevertheless, they are diverse on the molecular level. At present, two genes are known in 11q23 and four in 17q12-25 that generate five distinct fusion genes: MLL-MLLT6/AF17, MLL-LASP1, MLL-ACACA or MLL-SEPT9/MSF, and ZBTB16/PLZF-RARA. We analyzed 14 cases with a t(11;17) by fluorescence in situ hybridization and molecular genetic techniques and determined the molecular characteristics of their fusion genes. We identified six different gene fusions that comprised seven cases with a MLL-MLLT6/AF17, three with a MLL-SEPT9/MSF, and one each with MLL-LASP1, MLL-ACACA, and ZBTB16/PLZF-RARA fusions. In the remaining case, a MLL-SEPT6/Xq24 fusion suggested a complex rearrangement. The MLL-MLLT6/AF17 transcripts were extremely heterogeneous and the detection of seven different in-frame transcript and splice variants enabled us to predict the protein domains relevant for leukemogenesis. The putative MLL-MLLT6 consensus chimeric protein consists of the AT-hook DNA-binding, the methyltransferase, and the CXXC zinc-finger domains of MLL and the highly conserved octapeptide and the leucine-zipper dimerization motifs of MLLT6. The MLL-SEPT9 transcripts showed a similar high degree of variability. These analyses prove that the diverse types of t(11;17)-associated fusion genes can be reliably identified and delineated with a proper combination of cytogenetic and molecular genetic techniques. The heterogeneity of transcripts encountered in cases with MLL-MLLT6/AF17 and MLL-SEPT9/MSF fusions clearly demonstrates that thorough attention has to be paid to the appropriate selection of primers to cover all these hitherto unrecognized fusion variants.

Identification of a chromosomal breakpoint and detection of a novel form of an MLL-AF17 fusion transcript in acute monocytic leukemia with t(11;17)(q23;q21)

More than 40 genes have been reported as translocation partners of the mixed lineage leukemia gene (MLL) in hematologic malignancies. AF17 was identified earlier than most other MLL translocation partners. On the other hand, there is only 1 report of an MLL-AF17 fusion transcript in acute myeloid leukemia (AML). Here we describe a 40-year-old man with a diagnosis of AML involving t(11;17)(q23;q21). We identified a chromosomal breakpoint for t(11;17)(q23;q21) at MLL intron 6 and AF17 intron 8. Although the previously reported form of the MLL-AF17 fusion transcript was not detected by reverse transcriptase-polymerase chain reaction (PCR) analysis, a novel form of an MLL-AF17 fusion transcript joining MLL exon 6 to AF17 exon 9 was detected by complementary DNA panhandle PCR. The fact that 2 forms of MLL-AF17 retain the leucine zipper domain of AF17 suggests that the dimerization domain of AF17 is critical for leukemogenesis by the MLL-AF17 fusion gene.

AML bearing the translocation t(11;17)(q23;q21): involvement of MLL and a region close to RARA, with no differentiation response to retinoic acid

We describe a case of acute myeloid leukemia (AML) bearing the translocation t(11;17)(q23;q21). The morphological phenotype represented a monoblastic leukemia, AML French-American-British (FAB) M5a. Further analysis of the translocation revealed an involvement of the mixed-lineage leukemia (MLL) gene and a region closely proximal to the retinoic acid (RA) receptor alpha (RARA) gene. AMLs involving both a rearranged MLL and the 17q21 region, in which the RARA gene is located, have only been described in some individual cases. The functional role of this translocation is still unknown. Rearrangements of the MLL (11q23) gene in AML are usually related to the morphological phenotype FAB M5. In general, they are associated with an adverse prognosis. In acute promyelocytic leukemia, the translocation (15;17)(q22;q11-21) involving the RARA leads to a maturation arrest that can be overcome by RA, often inducing remission. In other forms of AML, however, the effects of RA are limited and diverse. To study whether RA might have a therapeutical potential in our case, we performed an in vitro analysis of RA effects on AML cells. We found that RA leads to enhanced cell death and up-regulation of CD38 and CD117. However, no hints of RA-induced in vitro differentiation were visible. Our data indicate that in AML cells bearing the t(11;17)(q23;q21), a differentiation arrest that is overcome by RA is not present. On the contrary, RA induces alterations in cellular regulation that are similar to the RA-induced changes observed in early hematogenic progenitors; thus, a possible therapeutical benefit of RA in such cases remains open.

Two cases of acute myeloid leukemia with t(11;17) associated with varying morphology and immunophenotype: rearrangement of the MLL gene and a region proximal to the RARα gene

This report describes 2 cases of acute myeloid leukemia (AML), which based on the WHO classification would be classified as AML with an 11q23 (MLL) abnormality, but with contrasting morphologic and immunophenotypic profiles. One case had monocytic features (morphologically and immunophenotypically) with a t(11;17)(q23;q21), a previously identified variant translocation in acute promyelocytic leukemia (APL). The second case had morphologic and immunophenotypic features of APL associated with a t(11;17)(q23;q25). In both cases, fluorescence-in-situ hybridization (FISH) analysis demonstrated that the 11q23 breakpoint involved the MLL gene, but RARalpha was not involved in the 17q breakpoints. These cases illustrate the importance of FISH analysis to confirm the presence of a particular recurring rearrangement.

Rearrangement of the MLL gene in acute myeloblastic leukemia: report of two rare translocations

Band 11q23 is known to be involved in translocations and insertions with a variety of partner chromosomes. They lead to MLL rearrangement, resulting in a fusion with numerous genes. We report here 2 male adults in whom a diagnosis of acute myelomonoblastic leukemia (FAB M4) and acute monoblastic leukemia (FAB M5) was made. Conventional cytogenetic techniques showed a 45,XY,t(1;11)(p32;q23),-7 karyotype in the first case and a 46,XY, t(11;17)(q23;q21) in the second case. Fluorescent in situ hybridization (FISH) with a specific MLL probe showed the gene to be disrupted, the 3' region being translocated on the derivative chromosomes 1 and 17, respectively. Fourteen and 24 patients, including ours, with acute myeloblastic leukemia associated with a t(1;11)(p32;q23) and a t(11;17)(q23;q21), respectively have been reported in the literature. Several patients with the latter translocation have also been identified to have acute lymphoblastic leukemia (ALL). Although both translocations are preferentially associated with monocytic differentiation, the t(11;17)(q23;q21) is more common in adults and has been reported in many patients with ALL, compared to the t(1;11)(p32;q23).

Rearrangement of the MLL gene and a region proximal to the RARalpha gene in a case of acute myelocytic leukemia M5 with a t(11;17)(q23;q21)

A case of acute myelocytic leukemia (AML) M5 subtype (French-American-British classification), in a 13-year-old girl showed the abnormal karyotype 46,XX,t(11;17)(q23;q21) in all bone marrow cells analyzed. Rearrangements involving 11q23 are frequent in cases of AML M5 and often involve the MLL gene. Nevertheless, t(11;17)(q23;q21) is very rare in this type of leukemia. In acute promyelocytic leukemia, the RARalpha gene, located at 17q21, is involved in almost all cases. Fluorescence in situ hybridization studies revealed a deletion of the C-terminal part of the MLL gene and a translocation of the RARalpha gene on the derivative chromosome 11, proximal to the remaining part of the MLL gene. However, hybridization with the LSI RARA dual color break-apart rearrangement probe showed that the RARalpha gene was not rearranged in this translocation. This is the first study reporting a t(11;17)(q23;q21) with a deletion distal to MLL gene exon 6 in a case of AML M5. Furthermore, this is the second study that strongly suggests the implication of a gene proximal and close to the RARalpha locus in a case of AML M5. According to these results, the discovery of new fusion partner genes of MLL and the precise characterization of t(11;17) will be important for the understanding of neoplastic cell differentiation in AML M5.