TCRα rearrangements identify a subgroup of NKL-deregulated adult T-ALLs associated with favorable outcome

T-cell acute lymphoblastic leukemia (T-ALL) results from leukemic transformation of T-cell precursors arrested at specific differentiation stages, including an 'early-cortical' thymic maturation arrest characterized by expression of cytoplasmic TCRβ but no surface T-cell receptor (TCR) and frequent ectopic expression of the TLX1/3 NK-like homeotic proteins (NKL). We designed a TCRα VJC PCR to identify clonal TCRα rearrangements in 32% of 127 T-ALLs, including 0/52 immature/TCRγδ lineage cases and 41/75 (55%) TCRαβ lineage cases. Amongst the latter, TCRα rearrangements were not identified in 30/54 (56%) of IMβ/pre-αβ early-cortical T-ALLs, of which the majority (21/30) expressed TLX1/3. We reasoned that the remaining T-ALLs might express other NKL proteins, so compared transcript levels of 46 NKL in T-ALL and normal thymic subpopulations. Ectopic overexpression of 10 NKL genes, of which six are unreported in T-ALL (NKX2-3, BARHL1, BARX2, EMX2, LBX2 and MSX2), was detectable in 17/104 (16%) T-ALLs. Virtually all NKL overexpressing T-ALLs were TCRα unrearranged and ectopic NKL transcript expression strongly repressed Eα activity, suggesting that ectopic NKL expression is the major determinant in early-cortical thymic T-ALL maturation arrest. This immunogenetic T-ALL subtype, defined by TCRβ VDJ but no TCRα VJ rearrangement, is associated with a favorable outcome in GRAALL-treated adult T-ALLs.

Methodological aspects of minimal residual disease assessment by flow cytometry in acute lymphoblastic leukemia: A French multicenter study

Background: Minimal residual disease (MRD) assessment provides a powerful prognostic factor for therapeutic stratification in acute lymphoblastic leukemia (ALL). Multiparameter flow cytometry (MFC) has the potential for a rapid and sensitive identification of high risk patients. Our group has previously published that MRD levels analyzed by clone specific Ig/TcR-QPCR and MFC were concordant at a sensitivity of 10-4 . Here we report the MFC methodological aspects from this multi-center experience. Methods: MRD was assessed by MFC in 1030 follow-up samples from 265 pediatric and adult patients with de novo ALL treated in the FRALLE, EORTC or GRALL clinical trials. MRD assessment as applied by the eight participating MFC laboratories is described in detail regarding cell preparation, leukemia-associated immunophenotype (LAIP) markers and data analysis. Samples were obtained from bone marrow (BM) and peripheral blood (PB). Immunostaining was performed after erythrocyte lysis or Ficoll enrichment. Results: This study confirms the applicability of MFC-based MRD assessment in 97% of patients with ALL at the 10-4 cut-off. MRD values after Ficoll enrichment and erythrocyte lysis were found comparable. Higher MRD values were obtained in BM than in PB, especially for B-lineage ALL. Conclusions: Measurement of MRD by MFC at the 10-4 cut-off is applicable within a few hours for almost all patients and using a comparable analytical strategy allows for multicenter collaborative studies. The method can be introduced in a strategy aimed at defining the risk of failure of patients with childhood or adult ALL. © 2014 Clinical Cytometry Society.

EuroFlow standardization of flow cytometer instrument settings and immunophenotyping protocols

The EU-supported EuroFlow Consortium aimed at innovation and standardization of immunophenotyping for diagnosis and classification of hematological malignancies by introducing 8-color flow cytometry with fully standardized laboratory procedures and antibody panels in order to achieve maximally comparable results among different laboratories. This required the selection of optimal combinations of compatible fluorochromes and the design and evaluation of adequate standard operating procedures (SOPs) for instrument setup, fluorescence compensation and sample preparation. Additionally, we developed software tools for the evaluation of individual antibody reagents and antibody panels. Each section describes what has been evaluated experimentally versus adopted based on existing data and experience. Multicentric evaluation demonstrated high levels of reproducibility based on strict implementation of the EuroFlow SOPs and antibody panels. Overall, the 6 years of extensive collaborative experiments and the analysis of hundreds of cell samples of patients and healthy controls in the EuroFlow centers have provided for the first time laboratory protocols and software tools for fully standardized 8-color flow cytometric immunophenotyping of normal and malignant leukocytes in bone marrow and blood; this has yielded highly comparable data sets, which can be integrated in a single database.

EuroFlow antibody panels for standardized n-dimensional flow cytometric immunophenotyping of normal, reactive and malignant leukocytes

Most consensus leukemia & lymphoma antibody panels consist of lists of markers based on expert opinions, but they have not been validated. Here we present the validated EuroFlow 8-color antibody panels for immunophenotyping of hematological malignancies. The single-tube screening panels and multi-tube classification panels fit into the EuroFlow diagnostic algorithm with entries defined by clinical and laboratory parameters. The panels were constructed in 2-7 sequential design-evaluation-redesign rounds, using novel Infinicyt software tools for multivariate data analysis. Two groups of markers are combined in each 8-color tube: (i) backbone markers to identify distinct cell populations in a sample, and (ii) markers for characterization of specific cell populations. In multi-tube panels, the backbone markers were optimally placed at the same fluorochrome position in every tube, to provide identical multidimensional localization of the target cell population(s). The characterization markers were positioned according to the diagnostic utility of the combined markers. Each proposed antibody combination was tested against reference databases of normal and malignant cells from healthy subjects and WHO-based disease entities, respectively. The EuroFlow studies resulted in validated and flexible 8-color antibody panels for multidimensional identification and characterization of normal and aberrant cells, optimally suited for immunophenotypic screening and classification of hematological malignancies.

Flow cytometry and IG/TCR quantitative PCR for minimal residual disease quantitation in acute lymphoblastic leukemia: a French multicenter prospective study on behalf of the FRALLE, EORTC and GRAALL

Minimal residual disease (MRD) quantification is widely used for therapeutic stratification in pediatric acute lymphoblastic leukemia (ALL). A robust, reproducible, sensitivity of at least 0.01% has been achieved for IG/TCR clonal rearrangements using allele-specific quantitative PCR (IG/TCR-QPCR) within the EuroMRD consortium. Whether multiparameter flow cytometry (MFC) can reach such inter-center performance in ALL MRD monitoring remains unclear. In a multicenter study, MRD was measured prospectively on 598 follow-up bone marrow samples from 102 high-risk children and 136 adult ALL patients, using IG/TCR-QPCR and 4/5 color MFC. At diagnosis, all 238 patients (100%) had at least one suitable MRD marker with 0.01% sensitivity, including 205/238 samples (86%) by using IG/TCR-QPCR and 223/238 samples (94%) by using MFC. QPCR and MFC were evaluable in 495/598 (83%) samples. Qualitative results (<0.01% or ≥0.01%) concurred in 96% of samples and overall positivity (including <0.01% and nonquantifiable positivity) was concurrent in 84%. MRD values ≥0.01% correlated highly (r(2)=0.87) and 69% clustered within half-a-log(10). QPCR and MFC can therefore be comparable if properly standardized, and are highly complementary. MFC strategies will benefit from a concerted approach, as does molecular MRD monitoring, and will contribute significantly to the achievement of 100% MRD informativity in adult and pediatric ALL.

Prediction of relapse by day 100 BCR-ABL quantification after allogeneic stem cell transplantation for chronic myeloid leukemia

Chronic myeloid leukemia (CML) relapse after allogeneic stem cell transplantation (SCT) is a relatively frequent situation, which is correlated to disease status, time from diagnosis to transplant and T-cell depletion. We evaluated the potential for early minimal residual disease (MRD) BCR-ABL quantification to predict relapse of CML patients receiving allogeneic SCT. Minimal residual disease was analyzed by real-time quantitative reverse transcriptase-polymerase chain reaction (RQ-PCR) at day 100 (d100) in 38 patients with >1 year follow-up after conventional non-T-cell-depleted SCT. Normal ABL control values from 1724 follow-up blood samples were used to define an RQ-PCR amplifiability index and the limits of reliable use of BCR-ABL ratios. We then compared the 14 patients with a high-level d100 BCR-ABL/ABL ratio (> or = 10(-4)) to that of the 24 patients with a negative/low-level ratio (<10(-4)). Despite being comparable for all classical parameters, the incidence of relapse was significantly higher in the high MRD group (11/14 (79%)) compared to that of the low/negative MRD group (7/24 (29%)) (P = 0.009), with d100 MRD values representing an independent risk factor of relapse and disease-free survival, but not of overall survival, in multivariate analysis. These data should facilitate risk-adapted post-transplant immunosuppression and/or tyrosine kinase inhibitor therapy based on an early evaluation of MRD.

CALM-AF10+ T-ALL expression profiles are characterized by overexpression of HOXA and BMI1 oncogenes

The t(10;11)(p13;q14-21) is found in T-ALL and acute myeloid leukemia and fuses CALM (Clathrin-Assembly protein-like Lymphoid-Myeloid leukaemia gene) to AF10. In order to gain insight into the transcriptional consequences of this fusion, microarray-based comparison of CALM-AF10+ vs CALM-AF10- T-ALL was performed. This analysis showed upregulation of HOXA5, HOXA9, HOXA10 and BMI1 in the CALM-AF10+ cases. Microarray results were validated by quantitative RT-PCR on an independent group of T-ALL and compared to mixed lineage leukemia-translocated acute leukemias (MLL-t AL). The overexpression of HOXA genes was associated with overexpression of its cofactor MEIS1 in CALM-AF10+ T-ALL, reaching levels of expression similar to those observed in MLL-t AL. Consequently, CALM-AF10+ T-ALL and MLL-t AL share a specific HOXA overexpression, indicating they activate common oncogenic pathways. In addition, BMI1, located close to AF10 breakpoint, was overexpressed only in CALM-AF10+ T-ALL and not in MLL-t AL. BMI1 controls cellular proliferation through suppression of the tumor suppressors encoded by the CDKN2A locus. This locus, often deleted in T-ALL, was conserved in CALM-AF10+ T-ALL. This suggests that decreased CDKN2A activity, as a result of BMI1 overexpression, contributes to leukemogenesis in CALM-AF10+ T-ALL. We propose to define a HOXA+ leukemia group composed of at least MLL-t, CALM-AF10 and HOXA-t AL, which may benefit from adapted management.

DEK-CAN molecular monitoring of myeloid malignancies could aid therapeutic stratification

The t(6;9)(p23;q34) is a recurrent chromosomal abnormality observed in 1% of acute myelogenous leukemia (AML), which generates a fusion transcript between DEK and CAN/NUP214 genes. We used a DEK-CAN real-time quantitative (RQ)-PCR strategy to analyze 79 retrospective and prospective samples from 12 patients. Five patients reached DEK-CAN negativity (sensitivity 10(-5)); all underwent early allogeneic hematopoietic stem cell transplantation (median 5.5 months from diagnosis) with some demonstrating molecular positivity at the time of allograft. All four cases in CCR with adequate follow-up (median 18.5 months, range 13--95) demonstrate persistent molecular negativity, whereas all seven patients with persistent DEK-CAN positivity died at a median of 12 months from diagnosis (range 7--27). We conclude that DEK-CAN molecular monitoring by RQ-PCR in t(6;9) malignancies is a useful tool for individual patient management and that molecular negativity is indispensable for survival, but should not be a prerequisite for allografting in this rare, poor prognosis, subset of AML.

IgH DJ rearrangements within T-ALL correlate with cCD79a expression, an immature/TCRγδ phenotype and absence of IL7Rα/CD127 expression

cCD79a and IgH VDJ/DJ rearrangements are considered to be relatively specific for B lymphoid precursors. We looked for both in cCD3+, CD7+, CD19- T-ALLs classified by TCR status into alphabeta or gammadelta/immature (IM) lineages, with individualization of HOX11L2+ T-ALLs since they represent an intermediate alphabeta/gammadelta category. cCD79a was expressed at low levels in 47% of T-ALL and was most frequent in IMgamma T-ALLs. IgH rearrangements were common in gammadelta/IM (45%) and HOX11L2+ (35%) T-ALLs compared to HOX11L2-negative cases (3%; P<0.001). CD127 (IL7Ralpha) expression was also more common in the gammadelta/IM lineage but its expression was virtually mutually exclusive of IgH rearrangement. Low-level cCD79a expression alone should therefore not be interpreted as evidence of B lineage affiliation in immature leukemias. gammadelta/IM lineage T-ALLs potentially include two distinct categories: predominantly IgH+, cCD79a+, CD127- cases which retain gammadelta and B lymphoid potential and IgH-, cCD79a-, CD127+ cases with restricted T lineage potential.

[Application of molecular biology techniques to malignant haematology]

Malignant hemopathies, although heterogeneous in their prognosis and oncogenesis, represent an interesting model for studying cancer genesis mechanisms in man through the recurrent presence of genetic abnormalities involved in oncogenesis and the availability of tumour material. Nowadays, molecular biology techniques are very much used for the diagnosis, the treatment and the follow-up of these diseases. Firstly used for research, the new techniques have completely changed our ability to characterise malignant hemopathies and to understand the cancer-inducing processes, permitting us to perform the biological assessment of patients with malignant hemopathies, the diagnosis, and to estimate and follow the outcome of patients after treatment. At a more fundamental level, the structural and functional analysis of the deregulated genes implied in leukaemia and lymphoma has improved our knowledge and understanding of oncogenic and physiologic mechanisms significantly.

t(5;14)/HOX11L2-positive T-cell acute lymphoblastic leukemia. A collaborative study of the Groupe Français de Cytogénétique Hématologique (GFCH)

To accurately estimate the incidence of HOX11L2 expression, and determine the associated cytogenetic features, in T-cell acute lymphoblastic leukemia (T-ALL), the Groupe Français de Cytogénétique Hématologique (GFCH) carried out a retrospective study of both childhood and adult patients. In total, 364 patients were included (211 children </=15 years and 153 adults), and 67 (18.5%) [47 children (22.4%) and 20 adults (13.1%)] were shown to either harbor the t(5;14)q35;q32) translocation or express the HOX11L2 gene or both. Most of the common hematological parameters did not show significant differences within positive and negative populations, whereas the incidence of CD1a+/CD10+ and cytoplasmic CD3+ patients was significantly higher in positive than in negative children. Out of the 63 positive patients investigated by conventional cytogenetics, 32 exhibited normal karyotype, whereas the others 31 showed clonal chromosome abnormalities, which did not include classical T-ALL specific translocations. Involvement of the RANBP17/HOX11L2 locus was ascertained by fluorescence in situ hybridization in six variant or alternative (three-way translocation or cytogenetic partner other than 14q32) translocations out of the 223 patients. Our results also show that HOX11L2 expression essentially occurs as a result of a 5q35 rearrangement, but is not associated with another identified T-ALL specific recurrent genetic abnormality, such as SIL-TAL fusion or HOX11 expression.

Refractory coeliac sprue is a diffuse gastrointestinal disease

BACKGROUND

Refractory coeliac sprue (RCS) with an immunophenotypically aberrant clonal intraepithelial lymphocyte (IEL) population is considered a cryptic form of intestinal T cell lymphoma.

AIMS

To investigate the distribution of the abnormal and monoclonal IEL population in the digestive tract of RCS patients.

PATIENTS AND METHODS

We compared the frequency of lymphocytic gastritis (LG) and lymphocytic colitis (LC), together with IEL phenotype and T cell clonality, in gastric and colonic samples from 15 adults with RCS (all with aberrant CD3 intracytoplasmic(+) surface(-) CD8(-) clonal IELs on duodenojejunal biopsies), 18 patients with active coeliac disease (ACD), and 10 patients with coeliac disease (CD) on a gluten free diet (GFD-CD) by means of immunohistochemistry and multiplex polymerase chain reaction amplification of the T cell receptor gamma gene (TCR-gamma) rearrangement. Blood samples of nine RCS patients were also tested for clonality.

RESULTS

LG was found in 9/14 (64%), 11/18 (61%), and 3/10 (30%) patients with RCS, ACD, and GFD-CD, respectively, while LC was found in 6/11 (55%), 3/4 (75%), and 2/3 (66%) patients. Contrary to CD, all samples from patients with LG and LC showed an aberrant IEL phenotype. Monoclonal TCR-gamma rearrangements were detected in 8/13 (62%), 8/10 (80%), and 4/9 (44%) of gastric, colonic, and blood samples, respectively, from RCS patients, while in CD patients such rearrangements were only found in 2/25 (8%) gastric samples.

CONCLUSION

The immunophenotypically aberrant monoclonal IEL population present in the small intestine of patients with RCS frequently disseminates to the blood and the entire gastrointestinal epithelium, suggesting that this is a diffuse gastrointestinal disease.

Typical essential thrombocythaemia does not express bcr-abelson fusion transcript

Essential thrombocythaemia (ET) is a chronic myeloproliferative disorder (MPD) characterized by an elevated platelet count and no identifiable underlying primary cause. According to the diagnostic criteria of the Polycythemia Vera Study Group (PVSG), ET lacks features diagnostic for other MPDs, including the Philadelphia chromosome (Ph) or bcr-abl rearrangement. Recently, some authors have reported bcr-abl transcript positivity in ET patients, but these findings remain controversial. The aim of this study was to investigate whether the bcr-abl transcript could be found in ET patients and to verify the hypothesis of a new ET variant. ET patients (n = 121) with a median age at diagnosis of 55 years were enrolled. The bcr-abl transcript status was examined by multiplex reverse transcription-polymerase chain reaction. Only two cases were positive for bcr-abl, one of which had the Ph at diagnosis. The positive bcr-abl transcript was associated, in both cases, with mild basophilia at diagnosis. After a median follow-up of 43 months (0-309 months), two patients in the bcr-abl-negative group developed Ph and bcr-abl-negative acute myeloid leukaemia (AML). In contrast, one of the two patients in the bcr-abl-positive group died from AML 13 years after diagnosis. In conclusion, our data on a large group of patients shows the rarity of the bcr-abl transcript in well-established ET. However, a subset of patients with apparent ET and basophilia may express the transcript and may constitute a novel entity intermediate between chronic myeloid leukaemia (CML) and typical ET. A prospective study is warranted in order to define better the clinical and biological characteristics of bcr-abl-expressing ET.