Acute myeloid leukemia with MLL rearrangements: clinicobiological features, prognostic impact and value of flow cytometry in the detection of residual leukemic cells

Abstract

The MLL gene, located at 11q23 band, is frequently disrupted by different chromosomal rearrangements that occur in a variety of hematological malignancies. MLL rearrangements are associated with distinct clinical features and a poor prognosis. The aim of this study was to analyze the incidence and the prognostic significance of MLL rearrangements in a consecutive series of adult AML patients and to determine the immunophenotypic features of these cases. The identification of abnormal immunophenotypes could be used for the detection of minimal residual disease (MRD). Ninety-three adult patients with de novo acute myeloid leukemia (AML) were analyzed by Southern blot in order to detect MLL rearrangements (MLL+). RT-PCR and genomic long-range PCR were performed to further characterize MLL partial tandem duplication (PTD) in those patients in whom conventional karyotype did not show 11q23 chromosomal translocations. All the patients were homogeneously immunophenotyped at diagnosis. MLL rearrangements were detected in 13 (14%) patients. Four patients (5%) showed 11q23 translocations by karyotypic conventional analysis. Nine patients (10%) revealed PTD of MLL and one patient showed a MLL cleavage pattern. The MLL+ patients usually expressed myeloid and monocytic antigens CD33 (12/13 cases), CD13 (9/13), CD117 (9/13), CD64 (11/13) and in some cases CD14 (4/11). HLA-DR was also positive in (12/13). Eight out of 13 cases expressed the stem cell marker CD34. Only one patient revealed lymphoid marker reactivity (CD7) and CD56 was expressed in 5/13 cases. All the MLL+ patients showed at least one aberrant phenotype at diagnosis, which allowed us to set out a simple panel for the MRD studies. Twenty-seven samples from eight patients in morphologic complete remission (CR) were analyzed using the aberrant immunologic combinations detected at diagnosis. Phenotypically abnormal cells were detected in all the patients who subsequently relapsed, whereas only one patient with MRD+ remained in CR. Owing to the high level of residual leukemic cells, the MLL+ patients showed a short CR duration and a poor survival. In conclusion, immunophenotyping may be a suitable approach to investigating MRD status in AML patients with PTD of the MLL gene.

Clinical outcome of de novo acute myeloid leukaemia patients with normal cytogenetics is affected by molecular genetic alterations: a concise review

“…In the first large study of CN-AML, 11% of patients had the MLL-PTD, and their CRD, but not OS, was significantly shorter compared with CRD of patients without MLL-PTD (median, 7AE1 vs. 23AE2 months, P ¼ 0AE01) (Caligiuri et al, 1998). Several, but not all (Steudel et al, 2003), subsequent studies confirmed these results (Schnittger et al, 2000;Döhner et al, 2002;Muñoz et al, 2003; Table I). The largest hitherto reported series comprised 221 CN-AML patients, 18 (7AE7%) of whom harboured MLL-PTD.…”

“…By the use of molecular genetic techniques, such as reverse transcription polymerase chain reaction (RT-PCR), global gene expression profiling and/or direct sequencing, several recurring molecular alterations of prognostic significance have now been identified in patients with cytogenetically normal AML (CN-AML) (Mró zek et al, 2007). These include gene mutations, such as the internal tandem duplication (ITD) of the FLT3 gene (Nakao et al, 1996;Kottaridis et al, 2001;Whitman et al, 2001;Fröhling et al, 2002;Kainz et al, 2002;Schnittger et al, 2002;Thiede et al, 2002;Beran et al, 2004), the partial tandem duplication (PTD) of the MLL gene (Schichman et al, 1994;Caligiuri et al, 1998;Schnittger et al, 2000;Döhner et al, 2002;Shiah et al, 2002;Muñoz et al, 2003), and mutations of the CEBPA (Pabst et al, 2001;Preudhomme et al, 2002;Fröhling et al, 2004) and NPM1 genes (Boissel et al, 2005;Döhner et al, 2005;Falini et al, 2005;Schnittger et al, 2005;Suzuki et al, 2005;Thiede et al, 2006) (Fig 1). Likewise, adverse prognosis has been associated with overexpression of single genes, such as BAALC (Tanner et al, 2001;Baldus et al, 2003Baldus et al, , 2006aBienz et al, 2005), ERG and MN1 (Heuser et al, 2006).…”

Identification of T-lymphocytic leukemia–initiating stem cells residing in a small subset of patients with acute myeloid leukemic disease

“…As the success of developing effective treatments that eliminate LICs in leukemia patients relies on the ability to detect the presence of all subtypes of LICs in patient samples, specific attention should be placed on using xenograft models to detect heterogeneous human LICs where MLL mutations (MLL-AFX1 specifically) may provide a diagnostic marker. As AML patients with MLL translocations are 62% more likely to lack therapeutic response to pan-AML treatment approaches, 32 we further suggest that therapeutic approaches that combat lymphoid leukemias 33 have remission-induction potential in AML patients with MLL-AFX mutations.…”

The heterogeneity of pediatric MLL-rearranged acute myeloid leukemia

“…This is in contrast to the frequency of MLL-PTD, which is equally low in pediatric AML, ranging from 1 to 10% depending on the screening method, 13,[37][38][39] as well as in adult AML, in the range of 5-10%. 37,[40][41][42][43][44][45][46][47] The different translocation partners of the rearranged MLL gene So far, more than 60 different fusion partners of MLL have been identified. Approximately 50% of pediatric AML cases with an MLL rearrangement consist of t(9;11)(p22;q23).…”