Unique morphological spectrum of lymphomas in Nijmegen breakage syndrome (NBS) patients with high frequency of consecutive lymphoma formation

Nijmegen breakage syndrome (NBS) is an autosomal recessive disorder characterized by microcephaly, immunodeficiency, radiation hypersensitivity, chromosomal instability and increased incidence of malignancies. In Poland 105 NBS cases showing mutations in the NBS gene (nibrin, NBN), have been diagnosed, approximately 53% of which have developed cancer, mainly (>90%) lymphoid malignancies. This study is based upon the largest reported group of NBS-associated lymphomas. The predominant lymphoma types found in these 14 NBS children were diffuse large B cell lymphoma (DLBCL) and T cell lymphoblastic lymphoma (T-LBL/ALL), all showing monoclonal Ig/TCR rearrangements. The spectrum of NBS lymphomas is completely different from sporadic paediatric lymphomas and lymphomas in other immunodeficient patients. Morphological and molecular analysis of consecutive lymphoproliferations in six NBS patients revealed two cases of true secondary lymphoma. Furthermore, 9/13 NBS patients with lymphomas analysed by split-signal FISH showed breaks in the Ig or TCR loci, several of which likely represent chromosome aberrations. The combined data would fit a model in which an NBN gene defect results in a higher frequency of DNA misrejoining during double-strand break (DSB) repair, thereby contributing to an increased likelihood of lymphoma formation in NBS patients.

Pitfalls in TCR gene clonality testing: teaching cases

Clonality testing in T-lymphoproliferations has technically become relatively easy to perform in routine laboratories using standardized multiplex polymerase chain reaction protocols for T-cell receptor (TCR) gene analysis as developed by the BIOMED-2 Concerted Action BMH4-CT98-3936. Expertise with clonality diagnostics and knowledge about the biology of TCR gene recombination are essential for correct interpretation of TCR clonality data. Several immunobiological and technical pitfalls that should be taken into account to avoid misinterpretation of data are addressed in this report. Furthermore, we discuss the need to integrate the molecular data with those from immunohistology, and preferably also flow cytometric immunophenotyping, for appropriate interpretation. Such an interactive, multidisciplinary diagnostic model guarantees integration of available data to reach the most reliable diagnosis.

Evaluation of functional single nucleotide polymorphisms of different genes coding for the immunoregulatory molecules in patients with monoclonal large granular lymphocyte lymphocytosis

TCR alpha beta+/CD4+ T-large granular lymphocyte (LGL) lymphocytosis is a subgroup of monoclonal T-LGL lymphoproliferative disorders that are different from the CD8+ TCR alpha beta T-LGL. An increasing evidence supports the involvement of a common antigen-driven mechanism in the etiology of TCR alpha beta+/CD4+ T-LGL. In this study, we tested several polymorphic markers associated with chronic viral infections and autoimmune diseases, including cytotoxic T-lymphocyte antigen-4 (CTLA-4), tumor necrosis factor-alpha (TNF-alpha), interleukin-10 (IL-10), interferon-gamma (IFN-gamma), RANTES, IL-1 alpha, FAS, FAS-ligand (FASL), and NKG2D, to investigate the potential association of these immunogenetic factors with the development of T-LGL. Overall, 38 patients with CD4+ T-LGL were analyzed and compared with a group of both CD8+/TCR alpha beta+ T-LGL patients (n = 43) and a group of control subjects (n = 176). Our results did not show any clear association between the different single nucleotide polymorphisms (SNPs) analyzed and the development of CD4+/TCR alpha beta T-LGL. An increase in the frequency of -380 (AA/GA) TNF-alpha genotype associated with a greater production of this cytokine was found among CD8+ T LGL patients in comparison to the CD4+LGL patients and the control group. Our results suggest that the frequency of SNP of the genes coding for the studied immunoregulatory molecules are not associated with the development of CD4+/TCR alpha beta+ T-LGL.

Undersized, oversized? It is not one-size-fits-all in lymphoid clonality detection

In clonality assessment in lymphoid malignancies expected size ranges of rearranged Ig/TCR PCR products are relevant and should be taken into account. Yet they should not be employed too strictly, as "undersized" and "oversized" products might still represent true rearrangement products. Now that Ig/TCR clonality testing has technically become relatively easy to perform in routine laboratories, correct interpretation becomes essential and preferably should be organized in close interaction between involved scientists.

Concomitant EBV-related B-cell proliferation and juvenile myelomonocytic leukemia in a 2-year-old child

We present a case of a 2-year-old girl, who developed concomitant EBV-related B-cell proliferation and juvenile myelomonocytic leukemia (JMML). JMML was initially not recognized because of predominant B-cell proliferation. The activating N-RAS mutation was retrospectively already detectable at this early stage. Our findings support the hypothesis that EBV may contribute to JMML pathogenesis by stimulating pre-existing malignant clones. However, such stimulation of leukemic clone does not require the direct incorporation of the virus into myeloid progenitors. Most probably a cytokine burst resulting from EBV infection allows expansion of pre-existing malignant myeloid progenitors. Further studies are required to delineate exact mechanisms of EBV-related promotion of the JMML clone.

Immunoglobulin gene rearrangements and the pathogenesis of multiple myeloma

The ability to rearrange the germ-line DNA to generate antibody diversity is an essential prerequisite for the production of a functional repertoire. While this is essential to prevent infections, it also represents the “Achilles heal” of the B-cell lineage, occasionally leading to malignant transformation of these cells by translocation of protooncogenes into the immunoglobulin (Ig) loci. However, in evolutionary terms this is a small price to pay for a functional immune system. The study of the configuration and rearrangements of the Ig gene loci has contributed extensively to our understanding of the natural history of development of myeloma. In addition to this, the analysis of Ig gene rearrangements in B-cell neoplasms provides information about the clonal origin of the disease, prognosis, as well as providing a clinical useful tool for clonality detection and minimal residual disease monitoring. Herein, we review the data currently available on both Ig gene rearrangements and protein patterns seen in myeloma with the aim of illustrating how this knowledge has contributed to our understanding of the pathobiology of myeloma.

Prognostic significance of molecular-cytogenetic abnormalities in pediatric T-ALL is not explained by immunophenotypic differences

Pediatric T-cell acute lymphoblastic leukemia (T-ALL) is characterized by chromosomal rearrangements possibly enforcing arrest at specific development stages. We studied the relationship between molecular-cytogenetic abnormalities and T-cell development stage to investigate whether arrest at specific stages can explain the prognostic significance of specific abnormalities. We extensively studied 72 pediatric T-ALL cases for genetic abnormalities and expression of transcription factors, NOTCH1 mutations and expression of specific CD markers. HOX11 cases were CD1 positive consistent with a cortical stage, but as 4/5 cases lacked cytoplasmatic-beta expression, developmental arrest may precede beta-selection. HOX11L2 was especially confined to immature and pre-AB developmental stages, but 3/17 HOX11L2 mature cases were restricted to the gammadelta-lineage. TAL1 rearrangements were restricted to the alphabeta-lineage with most cases being TCR-alphabeta positive. NOTCH1 mutations were present in all molecular-cytogenetic subgroups without restriction to a specific developmental stage. CALM-AF10 was associated with early relapse. TAL1 or HOX11L2 rearrangements were associated with trends to good and poor outcomes, respectively. Also cases with high vs low TAL1 expression levels demonstrated a trend toward good outcome. Most cases with lower TAL1 levels were HOX11L2 or CALM-AF10 positive. NOTCH1 mutations did not predict for outcome. Classification into T-cell developmental subgroups was not predictive for outcome.

The human androgen receptor X-chromosome inactivation assay for clonality diagnostics of natural killer cell proliferations

Clonality is a frequently exploited characteristic of lymphoid malignancies. However, in the natural killer (NK) cell subset of large granular lymphocyte proliferations, clonality is difficult to prove because of the lack of specific genetic markers, such as immunoglobulin or T-cell receptor gene rearrangements. The human androgen receptor (HUMARA) assay, a polymerase chain reaction-based X-chromosome inactivation assay, is a potential diagnostic tool in these disorders. Although there is much experience with X-chromosome inactivation assays in myeloid proliferations, these assays have found only very limited application in clonality assessment of NK cell proliferations. We applied the HUMARA assay in laboratory diagnostics for detection of clonality in NK cell proliferations. We describe its test performance and report three cases in which clonality of NK cell populations was investigated by use of this assay. Our results demonstrate the usefulness of the HUMARA assay in the diagnostic workup of NK cell proliferations.

Distinct gene expression profiles of acute myeloid/T-lymphoid leukemia with silenced CEBPA and mutations in NOTCH1

Gene expression profiling of acute myeloid leukemia (AML) allows the discovery of previously unrecognized molecular entities. Here, we identified a specific subgroup of AML, defined by an expression profile resembling that of AMLs with mutations in the myeloid transcription factor CCAAT/enhancer-binding protein alpha (C/EBPalpha), while lacking such mutations. We found that in these leukemias, the CEBPA gene was silenced, which was associated with frequent promoter hypermethylation. The leukemias phenotypically showed aberrant expression of T-cell genes, of which CD7 was most consistent. We identified 2 mechanisms that may contribute to this phenotype. First, absence of Cebpa led to up-regulation of specific T-cell transcripts (ie, Cd7 and Lck) in hematopoietic stem cells isolated from conditional Cebpa knockout mice. Second, the enhanced expression of TRIB2, which we identify here as a direct target of the T-cell commitment factor NOTCH1, suggested aberrantly activated Notch signaling. Putatively activating NOTCH1 mutations were found in several specimens of the newly identified subgroup, while a large set of control AMLs was mutation negative. A gene expression prediction signature allowed the detection of similar cases of leukemia in independent series of AML.

The C-MYB locus is involved in chromosomal translocation and genomic duplications in human T-cell acute leukemia (T-ALL), the translocation defining a new T-ALL subtype in very young children

The C-Myb transcription factor is essential for hematopoiesis, including in the T-cell lineage. The C-Myb locus is a common site of retroviral insertional mutagenesis, however no recurrent genomic involvement has been reported in human malignancies. Here, we identified 2 types of genomic alterations involving the C-MYB locus at 6q23 in human T-cell acute leukemia (T-ALL). First, we found a reciprocal translocation, t(6;7)(q23;q34), that juxtaposed the TCRB and C-MYB loci (n = 6 cases). Second, a genome-wide copy-number analysis by array-based comparative genomic hybridization (array-CGH) identified short somatic duplications that include C-MYB (MYB(dup), n = 13 cases of 84 T-ALL, 15%). Expression analysis, including allele-specific approaches, showed stronger C-MYB expression in the MYB-rearranged cases compared with other T-ALLs, and a dramatically skewed C-MYB allele expression in the TCRB-MYB cases, which suggests that a translocation-driven deregulated expression may overcome a cellular attempt to down-regulate C-MYB. Strikingly, profiling of the T-ALLs by clinical, genomic, and large-scale gene expression analyses shows that the TCRB-MYB translocation defines a new T-ALL subtype associated with a very young age for T-cell leukemia (median, 2.2 years) and with a proliferation/mitosis expression signature. By contrast, the MYB(dup) alteration was associated with the previously defined T-ALL subtypes.

Different chromosomal breakpoints impact the level of LMO2 expression in T-ALL

The t(11;14)(p13;q11) is presumed to arise from an erroneous T-cell receptor delta TCRD V(D)J recombination and to result in LMO2 activation. However, the mechanisms underlying this translocation and the resulting LMO2 activation are poorly defined. We performed combined in vivo, ex vivo, and in silico analyses on 9 new t(11;14)(p13;q11)-positive T-cell acute lymphoblastic leukemia (T-ALL) as well as normal thymocytes. Our data support the involvement of 2 distinct t(11;14)(p13;q11) V(D)J-related translocation mechanisms. We provide compelling evidence that removal of a negative regulatory element from the LMO2 locus, rather than juxtaposition to the TCRD enhancer, is the main determinant for LMO2 activation in the majority of t(11;14)(p13;q11) translocations. Furthermore, the position of the LMO2 breakpoints in T-ALL in the light of the occurrence of TCRD-LMO2 translocations in normal thymocytes points to a critical role for the exact breakpoint location in determining LMO2 activation levels and the consequent pressure for T-ALL development.

Selective retention of herpes simplex virus-specific T cells in latently infected human trigeminal ganglia

Primary infection with herpes simplex virus 1 (HSV-1) and varicella zoster virus (VZV) results in lifelong latent infections of neurons in sensory ganglia such as the trigeminal ganglia (TG). It has been postulated that T cells retained in TG inhibit reactivation of latent virus. The acquisition of TG specimens of individuals within hours after death offered the unique opportunity to characterize the phenotype and specificity of TG-resident T cells in humans. High numbers of activated CD8(+) T cells expressing a late effector memory phenotype were found to reside in latently infected TG. The T cell infiltrate was oligoclonal, and T cells selectively clustered around HSV-1 but not VZV latently infected neurons. Neuronal damage was not observed despite granzyme B expression by the neuron-interacting CD8(+) T cells. The TG-resident T cells, mainly CD8(+) T cells, were directed against HSV-1 and not to VZV, despite neuronal expression of VZV proteins. The results implicate that herpesvirus latency in human TG is associated with a local, persistent T cell response, comprising activated late effector memory CD8(+) T cells that appear to control HSV-1 latency by noncytolytic pathways. In contrast, T cells do not seem to be directly involved in controlling VZV latency in human TG.

Monoclonal TCR-Vbeta13.1+/CD4+/NKa+/CD8-/+dim T-LGL lymphocytosis: evidence for an antigen-driven chronic T-cell stimulation origin

Monoclonal TCRalphabeta(+)/CD4+ T-large granular lymphocyte (T-LGL) lymphocytosis is a T-cell disorder with a restricted TCR-Vbeta repertoire. In the present study we explored the potential association between the expanded TCR-Vbeta families, the CDR3 sequences of the TCR-Vbeta gene, and the HLA genotype of patients with monoclonal TCRalphabeta(+)/CD4+ T-LGL lymphocytosis. For that purpose, 36 patients with monoclonal TCRalphabeta(+)/CD4+ T-LGL lymphocytosis (15 TCR-Vbeta13.1 versus 21 non-TCR-Vbeta13.1) were selected. For each patient, both the HLA (class I and II) genotype and the DNA sequences of the VDJ-rearranged TCR-Vbeta were analyzed. Our results show a clear association between the TCR-Vbeta repertoire and the HLA genotype, all TCR-Vbeta13.1(+) cases being HLA-DRB1*0701 (P = .004). Interestingly, the HLA-DR7/TCR-Vbeta13.1-restricted T-cell expansions displayed a highly homogeneous and strikingly similar TCR arising from the use of common TCR-Vbeta gene segments, which shared (1) unique CDR3 structural features with a constantly short length, (2) similar combinatorial gene rearrangements with frequent usage of the Jbeta1.1 gene, and (3) a homolog consensus protein sequence at recombination junctions. Overall, these findings strongly support the existence of a common antigen-driven origin for monoclonal CD4+ T-LGL lymphocytosis, with the identification of the exact peptides presented to the expanded T cells deserving further investigations.

Human T-cell lines with well-defined T-cell receptor gene rearrangements as controls for the BIOMED-2 multiplex polymerase chain reaction tubes

The BIOMED-2 multiplex polymerase chain reaction (PCR) tubes for analysis of immunoglobulin and T-cell receptor (TCR) gene rearrangements have recently been introduced as a reliable and easy tool for clonality diagnostics in suspected lymphoproliferations. Quality and performance assessment of PCR-based clonality diagnostics is generally performed using human leukemia/lymphoma cell lines as controls. We evaluated the utility of 30 well-defined human T-cell lines for quality performance testing of the BIOMED-2 PCR primers and protocols. The PCR analyses of the TCR loci were backed up by Southern blot analysis. The clonal TCRB, TCRG and TCRD gene rearrangements were analyzed for gene segment usage and for the size and composition of their junctional regions. In 29 out of 30 cell lines, unique clonal TCR gene rearrangements could be easily detected. Besides their usefulness in molecular clonality diagnostics, these cell lines can now be authenticated based on their TCR gene rearrangement profile. This enables their correct use in molecular clonality diagnostics and in other cancer research studies.

Improved reliability of lymphoma diagnostics via PCR-based clonality testing: — Report of the BIOMED-2 Concerted Action BHM4-CT98-3936

The diagnosis of malignant lymphoma is a recognized difficult area in histopathology. Therefore, detection of clonality in a suspected lymphoproliferation is a valuable diagnostic criterion. We have developed primer sets for the detection of rearrangements in the B- and T-cell receptor genes as reliable tools for clonality assessment in lymphoproliferations suspected for lymphoma. In this issue of Leukemia, the participants of the BIOMED-2 Concerted Action CT98-3936 report on the validation of the newly developed clonality assays in various disease entities. Clonality was detected in 99% of all B-cell malignancies and in 94% of all T-cell malignancies, whereas the great majority of reactive lesions showed polyclonality. The combined BIOMED-2 results are summarized in a guideline, which can now be implemented in routine lymphoma diagnostics. The use of this standardized approach in patients with a suspect lymphoproliferation will result in improved diagnosis of malignant lymphoma.

Powerful strategy for polymerase chain reaction-based clonality assessment in T-cell malignancies Report of the BIOMED-2 Concerted Action BHM4 CT98-3936

Polymerase chain reaction (PCR) assessment of clonal T-cell receptor (TCR) and immunoglobulin (Ig) gene rearrangements is an important diagnostic tool in mature T-cell neoplasms. However, lack of standardized primers and PCR protocols has hampered comparability of data in previous clonality studies. To obtain reference values for Ig/TCR rearrangement patterns, 19 European laboratories investigated 188 T-cell malignancies belonging to five World Health Organization-defined entities. The TCR/Ig spectrum of each sample was analyzed in duplicate in two different laboratories using the standardized BIOMED-2 PCR multiplex tubes accompanied by international pathology panel review. TCR clonality was detected in 99% (143/145) of all definite cases of T-cell prolymphocytic leukemia, T-cell large granular lymphocytic leukemia, peripheral T-cell lymphoma (unspecified) and angioimmunoblastic T-cell lymphoma (AILT), whereas nine of 43 anaplastic large cell lymphomas did not show clonal TCR rearrangements. Combined use of TCRB and TCRG genes revealed two or more clonal signals in 95% of all TCR clonal cases. Ig clonality was mostly restricted to AILT. Our study indicates that the BIOMED-2 multiplex PCR tubes provide a powerful strategy for clonality assessment in T-cell malignancies assisting the firm diagnosis of T-cell neoplasms. The detected TCR gene rearrangements can also be used as PCR targets for monitoring of minimal residual disease.

Polymerase chain reaction-based clonality testing in tissue samples with reactive lymphoproliferations: usefulness and pitfalls. A report of the BIOMED-2 Concerted Action BMH4-CT98-3936

Lymphoproliferations are generally diagnosed via histomorphology and immunohistochemistry. Although mostly conclusive, occasionally the differential diagnosis between reactive lesions and malignant lymphomas is difficult. In such cases molecular clonality studies of immunoglobulin (Ig)/T-cell receptor (TCR) rearrangements can be useful. Here we address the issue of clonality assessment in 106 histologically defined reactive lesions, using the standardized BIOMED-2 Ig/TCR multiplex polymerase chain reaction (PCR) heteroduplex and GeneScan assays. Samples were reviewed nationally, except 10% random cases and cases with clonal results selected for additional international panel review. In total 75% (79/106) only showed polyclonal Ig/TCR targets (type I), whereas another 15% (16/106) represent probably polyclonal cases, with weak Ig/TCR (oligo)clonality in an otherwise polyclonal background (type II). Interestingly, in 10% (11/106) clear monoclonal Ig/TCR products were observed (types III/IV), which prompted further pathological review. Clonal cases included two missed lymphomas in national review and nine cases that could be explained as diagnostically difficult cases or probable lymphomas upon additional review. Our data show that the BIOMED-2 Ig/TCR multiplex PCR assays are very helpful in confirming the polyclonal character in the vast majority of reactive lesions. However, clonality detection in a minority should lead to detailed pathological review, including close interaction between pathologist and molecular biologist.

The outcome of molecular-cytogenetic subgroups in pediatric T-cell acute lymphoblastic leukemia: a retrospective study of patients treated according to DCOG or COALL protocols

BACKGROUND AND OBJECTIVES

Subgroups of T-cell acute lymphoblastic leukemia (T-ALL), defined according to recurrent cytogenetic aberrations, may have different prognoses. The aim of this study was to determine the prognostic relevance of molecular-cytogenetic abnormalities in pediatric patients using quantitative real-time polymerase chain reaction and fluorescence in situ hybridization.

DESIGN AND METHODS

The patients were assigned to TAL1, HOX11/TLX1, HOX11L2/TLX3, or CALM-AF10 subgroups. The cytogenetic subgroups were characterized in relation to immunophenotype and the expression of aberrantly expressed transcription factors.

RESULTS

In our cohort study, CALM-AF10 was associated with an immature immunophenotype and poor outcome (p=0.005). HOX11L2 was associated with both immunophenotypically immature cases as well as cases committed to the gammadelta-lineage. HOX11L2 was significantly associated with poor outcome (p=0.01), independently of the expression of CD1 or the presence of NOTCH1 mutations. TAL1 abnormalities were associated with alphabeta-lineage commitment, and tended to be associated with a good outcome. Cells in HOX11 cases resembled early CD1-positive cortical thymocytes without expression of Cytbeta and TCR molecules. In relation to the expression of early T-cell transcription factors, high TAL1 levels were found in immunophenotypically-advanced cases, whereas high LYL1 levels were found in immature subgroups.

INTERPRETATION AND CONCLUSIONS

The reported outcomes for HOX11L2-rearranged T-ALL cases are conflicting; the prognostic impact may depend on the therapy given. In our cohort, this cytogenetic aberration was associated with a poor outcome. Our data on CALM-AF10 rearranged T-ALL, albeit based on only three patients, suggest that this type of leukemia is associated with a poor outcome.

CD38 as a prognostic factor in B cell chronic lymphocytic leukaemia (B-CLL): comparison of three approaches to analyze its expression

BACKGROUND

Increased CD38 expression by leukemic cells has been suggested as an adverse prognostic factor in B-CLL. Several approaches have been proposed to quantify its level of expression by flow cytometry.

METHODS

We compared the use of (i) the percentage of CD38 positive cells, (ii) CD38 antibodies bound per cell (ABC), and (iii) a semi-quantitative method based on the shape of the CD38 histogram, within a cohort of 78 B-CLL patients.

RESULTS

A decreased overall survival was seen with >30% CD38 positivity among B-CLL cells, with CD38 ABC >100, and with bimodal or unimodal, strongly positive CD38 histograms. However, patients with unimodal weakly positive CD38 histograms also showed a significantly reduced survival as did patients with intermediate proportions (i.e. 5-30%) of CD38+ cells. Furthermore, within the group with <5% CD38 positivity among their B-CLL cells, 84% of patients showed prognostically favourable mutated IGVH gene segments and 100% had low ZAP70 gene expression. For 5-30% CD38 positivity, these proportions were 50 and 83%, while for >30% CD38 positivity, these proportion were only 28 and 56%, respectively.

CONCLUSIONS

We found a simple method of quantitation of CD38 expression (i.e., >5% CD38 positivity among B-CLL cells) to be sufficient to identify patients with an unfavourable prognosis. The level of CD38 expression as defined with this method correlated well with the IGVH mutation status and ZAP70 gene expression.

Antigen receptors and somatic hypermutation in B-cell chronic lymphocytic leukemia with Richter's transformation

BACKGROUND AND OBJECTIVES

Activation-induced cytidine deaminase is essential for somatic hypermutation and class switch recombination of the immunoglobulin genes in B cells. It has been proposed that aberrant targeting of the somatic hypermutation machinery is instrumental in initiation and progression of B-cell non Hodgkin's lymphomas. In this study, we investigated the B-cell receptor and the role of the somatic hypermutation machinery in B-cell chronic lymphocytic leukemias (B-CLL) prior to and after transformation to a lymphoma of a higher malignancy grade (Richter's transformation).

DESIGN AND METHODS

We investigated the activity of the somatic hypermutation machinery in nine B-CLL and secondary diffuse large B-cell lymphomas by measuring the expression of activation-induced cytidine deaminase, in combination with mutation analysis of immunoglobulin (Ig) and non-Ig genes. Furthermore, the structure of the antigen receptors of B-CLL known to have developed a Richter's syndrome (RS B-CLL) was analyzed by comparing the most variable region of the Ig, the CDR3 region, to CDR3 sequences present in GenBank.

RESULTS

Ig variable heavy chain (IgV(H)) gene studies revealed that Richter's transformation occurs almost exclusively in unmutated B-CLL. Furthermore, activated-induced cytidine deaminase expression and somatic hypermutation activity of most RS B-CLL were found to be higher than those of control (non-transforming) B-CLL. Finally, comparison of the IgVH-CDR3 regions showed a remarkable amino acid sequence homology between two RS B-CLL of our panel and two RS B-CLL described in the literature.

INTERPRETATIONS AND CONCLUSIONS

The combined findings suggest a role for the Ig gene diversification apparatus during Richter's transformation and show that distinct RS-B-CLL may recognize recurrent antigenic epitopes.

Split-signal FISH for detection of chromosome aberrations

Chromosome aberrations are frequently observed in hematopoietic malignancies. These aberrations can deregulate expression of an oncogene, resulting in aberrant expression or overexpression, or they can form leukemia-specific chimeric fusion proteins. Detection of chromosome aberrations is an important tool for classification of the malignancy and for the definition of risk groups, which need different treatment protocols. We developed rapid and sensitive split-signal fluorescent in situ hybridization (FISH) assays for frequently occuring chromosome aberrations. The split-signal FISH approach uses two differentially labeled probes, located in one gene at opposite sites of the breakpoint region. In normal karyotypes, two co-localized green/red signals are visible, but a translocation results in a split of one of the co-localized signals. Split-signal FISH has three main advantages over the classical fusion-signal FISH approach, which uses of two labeled probes located in two genes. First, the detection of a chromosome aberration is independent of the involved partner gene. Second, split-signal FISH allows the identification of the partner gene or chromosome region if metaphase spreads are present, and finally it reduces false-positivity.

TCRgammadelta+ large granular lymphocyte leukemias reflect the spectrum of normal antigen-selected TCRgammadelta+ T-cells

T-cell large granular lymphocytes (LGL) proliferations range from reactive expansions of activated T cells to T-cell leukemias and show variable clinical presentation and disease course. The vast majority of T-LGL proliferations express TCRalphabeta. Much less is known about the characteristics and pathogenesis of TCRgammadelta+ cases. We evaluated 44 patients with clonal TCRgammadelta+ T-LGL proliferations with respect to clinical data, immunophenotype and TCR gene rearrangement pattern. TCRgammadelta+ T-LGL leukemia patients had similar clinical presentations as TCRalphabeta+ T-LGL leukemia patients. Their course was indolent and 61% of patients were symptomatic. The most common clinical manifestations were chronic cytopenias - neutropenia (48%), anemia (23%), thrombocytopenia (9%), pancytopenia (2%) - and to a lesser extent splenomegaly (18%). Also multiple associated autoimmune (34%) and hematological (14%) disorders were found. Leukemic LGLs were predominantly positive for CD2, CD5, CD7, CD8, and CD57, whereas variable expression was seen for CD16, CD56, CD11b, and CD11c. The Vgamma9/Vdelta2 immunophenotype was found in 48% of cases and 43% of cases was positive for Vdelta1, reflecting the TCR-spectrum of normal TCRgammadelta+ T-cells in adult PB. Identification of the well-defined post-thymic Vdelta2-Jdelta1 selection determinant in all evaluable Vgamma9+/Vdelta2+ patients, is suggestive of common (super)antigen involvement in the pathogenesis of these TCRgammadelta+ T-LGL leukemia patients.

The effect of a novel recombination between the homeobox gene NKX2-5 and the TRD locus in T-cell acute lymphoblastic leukemia on activation of the NKX2-5 gene

BACKGROUND AND OBJECTIVES

The NK-like homeobox gene (NKX2-5/CSX) plays a crucial role in cardiac development but is not normally expressed in hematopoietic cells. Here, we describe for the first time a fusion between NKX2-5 and the T-cell receptor delta locus (TRD) resulting in NKX2-5 activation in a case of T-cell acute lymphoblastic leukemia (T-ALL).

DESIGN AND METHODS

Genomic DNA from a T-ALL patient with an atypical rearrangement, detected by Southern blotting, was analyzed by ligation-mediated polymerase chain reaction (PCR) with TRD-specific primers. Expression of NKX2-5 was analyzed by real-time quantitative PCR in the T-ALL case with the NKX2-5-TRD rearrangement, 18 other cases of T-ALL, three T-ALL derived cell lines, two non-hematopoietic cell lines, peripheral blood mononuclear cells from six healthy individuals and sorted thymocyte subsets.

RESULTS

Sequence analysis of ligation-mediated PCR products revealed a novel rearrangement between the third diversity segment of the TRD locus (TRDD3) and a region on chromosome 5q35.1 located 32 kb downstream of the NKX2-5/CSX gene. As a result of this recombination NKX2-5 was placed under influence of the TRD enhancer, resulting in strong ectopic NKX2-5 expression. High NKX2-5 expression was also found in the T-cell lines PEER and CCRF-CEM, which harbor an NKX2-5-BCL11B rearrangement, and in the embryonic kidney cell line 293. NKX2-5 was not expressed in any of the major thymocyte subsets, in normal peripheral blood mononuclear cells, or in the majority (17/18) of the other cases of T-ALL.

INTERPRETATION AND CONCLUSIONS

Our finding of overexpression of yet another homeobox gene in T-ALL further supports the hypothesis that homeobox genes play an important role in malignant transformation of particular types of T-ALL.

The predictive value of lipoprotein lipase for survival in chronic lymphocytic leukemia

BACKGROUND AND OBJECTIVES

The mutational status of the immunoglobulin heavy chain variable region genes (IGVH) is a strong indicator of prognosis in B-cell chronic lymphocytic leukaemia (CLL). Since the determination of the IGVH mutation status is very labor-intensive, alternative prognostically relevant markers would facilitate CLL diagnostics.

DESIGN AND METHODS

Ten genes were selected from previously published gene expression profiling studies based on their differential expression in IGVH mutated versus unmutated cases of CLL, and tested with real-time quantitative polymerase chain reaction (RQ-PCR) in unpurified samples from 130 CLL patients. To ascertain potential contaminating effects by normal hematopoietic cells, the expression levels of the selected genes were determined in normal monocytes, B cells, T cells, NK cells and granulocytes.

RESULTS

The selected genes, i.e., ZAP70, LPL, SPG20, ADAM29, NRIP1, AKAP12, DMD, SEPT10, TPM2 and CLECSF2, showed prognostic significance. In multivariate logistic regression analysis expression levels of LPL, ZAP70, ADAM29 and SEPT10 were the most predictive for IGVH mutational status. In univariate analysis the expression of LPL was the best predictor. For survival, expression of LPL was the strongest prognostic factor. In combination with the three cytogenetic markers associated with a poor prognosis, i.e., deletions 17p13, 11q22 and trisomy 12, expression of LPL and IGVH mutational status performed equally well with regard to their predictive value for survival, both being more predictive than ZAP70.

INTERPRETATION AND CONCLUSIONS

This study demonstrates that LPL expression is a predictor for survival in CLL, and for this purpose is as good as IGVH mutational status and more reliable than ZAP70 expression when tested in unpurified CLL samples.

Recombination in the Human IGK Locus

The human IGK locus is probably the most complex of all antigen-receptor loci because of the presence of many elements that can be involved in V(D)J recombination. Next to classical Vkappa-Jkappa recombinations and deletional recombinations involving Kde (intron-Kde, Vkappa-Kde), JkappaRSS-intronRSS signal joints and Vkappa-intronRSS and JkappaRSS-Kde pseudohybrid joints are observed in human B-cell malignancies and also in normal human B cells. These recombinations occur in an ordered and tightly regulated way. Although DNA (de)methylation, histone (de)acetylation, and nuclear positioning all play a role in this regulation, much is still to be learned about the exact factors involved. One of these factors seems to be E2A that is known to be important in B-cell development and has a direct role in the induction of human endogenous IGK recombination. Contrary to the human IGH locus, aberrant recombinations resulting in chromosomal translocations are not very frequent in the human IGK locus. Despite this, IGK recombinations have diagnostic and clinical implications, being important PCR targets for clonality and MRD studies.

BIOMED-2 multiplex immunoglobulin/T-cell receptor polymerase chain reaction protocols can reliably replace Southern blot analysis in routine clonality diagnostics

To establish the most sensitive and efficient strategy of clonality diagnostics via immunoglobulin and T-cell receptor gene rearrangement studies in suspected lymphoproliferative disorders, we evaluated 300 samples (from 218 patients) submitted consecutively for routine diagnostics. All samples were studied using the BIOMED-2 multiplex polymerase chain reaction (PCR) protocol. In 176 samples, Southern blot (SB) data were also available, and the two types of molecular results were compared. Results of PCR and SB analysis of both T-cell receptor and immunoglobulin loci were concordant in 85% of samples. For discordant results, PCR results were more consistent with the final diagnosis in 73% of samples. No false-negative results were obtained by PCR analysis. In contrast, SB analysis failed to detect clonality in a relatively high number of samples, mainly in cases of low tumor burden. We conclude that the novel BIOMED-2 multiplex PCR strategy is of great value in diagnosing patients with suspected B- and T-cell proliferations. Because of its higher speed, efficiency, and sensitivity, it can reliably replace SB analysis in clonality diagnostics in a routine laboratory setting. Just as with SB results, PCR results should always be interpreted in the context of clinical, immunophenotypical, and histopathological data.

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.

A high-density SNP genomewide linkage scan for chronic lymphocytic leukemia-susceptibility loci

Chronic lymphocytic leukemia (CLL) and other B-cell lymphoproliferative disorders (LPDs) show clear evidence of familial aggregation, but the inherited basis is largely unknown. To identify a susceptibility gene for CLL, we conducted a genomewide linkage analysis of 115 pedigrees, using a high-density single-nucleotide polymorphism (SNP) array containing 11,560 markers. Multipoint linkage analyses were undertaken using both nonparametric (model-free) and parametric (model-based) methods. Our results confirm that the presence of high linkage disequilibrium (LD) between SNP markers can lead to inflated nonparametric linkage (NPL) and LOD scores. After the removal of high-LD SNPs, we obtained a maximum NPL of 3.14 (P=.0008) on chromosome 11p11. The same genomic position also yielded the highest multipoint heterogeneity LOD (HLOD) score under both dominant (HLOD 1.95) and recessive (HLOD 2.78) models. In addition, four other chromosomal positions (5q22-23, 6p22, 10q25, and 14q32) displayed HLOD scores >1.15 (which corresponds to a nominal P value <.01). None of the regions coincided with areas of common chromosomal abnormalities frequently observed for CLL. These findings strengthen the argument for an inherited predisposition to CLL and related B-cell LPDs.

New insights on human T cell development by quantitative T cell receptor gene rearrangement studies and gene expression profiling

To gain more insight into initiation and regulation of T cell receptor (TCR) gene rearrangement during human T cell development, we analyzed TCR gene rearrangements by quantitative PCR analysis in nine consecutive T cell developmental stages, including CD34⁺ lin⁻ cord blood cells as a reference. The same stages were used for gene expression profiling using DNA microarrays. We show that TCR loci rearrange in a highly ordered way (TCRD-TCRG-TCRB-TCRA) and that the initiating Dδ2-Dδ3 rearrangement occurs at the most immature CD34⁺CD38⁻CD1a⁻ stage. TCRB rearrangement starts at the CD34⁺CD38⁺CD1a⁻ stage and complete in-frame TCRB rearrangements were first detected in the immature single positive stage. TCRB rearrangement data together with the PTCRA (pTα) expression pattern show that human TCRβ-selection occurs at the CD34⁺CD38⁺CD1a⁺ stage. By combining the TCR rearrangement data with gene expression data, we identified candidate factors for the initiation/regulation of TCR recombination. Our data demonstrate that a number of key events occur earlier than assumed previously; therefore, human T cell development is much more similar to murine T cell development than reported before.

Clonal identity between skin and synovial tissue in a case of mycosis fungoides with polyarthritis

Polyarthritis in the presence of a cutaneous T-cell lymphoma is a rare phenomenon. We describe a case of mycosis fungoides with development of a symmetric erosive polyarthritis of the small hand joints and feet, diagnosed as rheumatoid arthritis. An identical monoclonal T-cell population in the skin and in the synovium was detected by T-cell receptor gene rearrangement analysis, illustrating articular dissemination of lymphoma cells. Differentiating mycosis fungoides-associated arthritis from rheumatoid arthritis may have important implications for treatment. Based on this case, the relevant literature, and the newest disease concepts, pathogenic mechanisms and therapeutic options of mycosis fungoides-associated arthritis are discussed.

Disruption of the BCL11B gene through inv(14)(q11.2q32.31) results in the expression of BCL11B-TRDC fusion transcripts and is associated with the absence of wild-type BCL11B transcripts in T-ALL

T-cell acute lymphoblastic leukemia (T-ALL) is associated with chromosomal aberrations characterized by juxtaposition of proto-oncogenes to T-cell receptor gene loci (TCR), resulting in the deregulated transcription of these proto-oncogenes. Here, we describe the molecular characterization of a novel chromosomal aberration, inv(14)(q11.2q32.31), in a T-ALL sample, involving the recently described BCL11B gene and the TCRD locus. The inversion joined the 5' part of BCL11B, including exons 1-3, to the TRDD3 gene segment of the TCRD locus, whereas the reciprocal breakpoint fused the TRDV1 gene segment to the fourth exon of BCL11B. The TRDV1-BCL11B joining region was 1344 bp long and contained fragments derived from 20q11.22, 3p21.33 and from 11p12, indicating the complex character of this aberration. A strong expression of in-frame transcripts with truncated BCL11B and TCRD constant region (TRDC) were observed, but in contrast to normal T cells and other T-ALL samples, no wild-type BCL11B transcripts were detected in the T-ALL sample. Screening of 37 other T-ALLs revealed one additional case with expression of the BCL11B-TRDC fusion transcript. As BCL11B appears to play a key role in T-cell differentiation, BCL11B disruption and disturbed expression may contribute to the development of T-cell malignancies in man.

Unraveling the consecutive recombination events in the human IGK locus

In addition to the classical Vkappa-Jkappa, Vkappa-kappa deleting element (Kde), and intron-Kde gene rearrangements, atypical recombinations involving Jkappa recombination signal sequence (RSS) or intronRSS elements can occur in the Igkappa (IGK) locus, as observed in human B cell malignancies. In-depth analysis revealed that atypical JkappaRSS-intronRSS, Vkappa-intronRSS, and JkappaRSS-Kde recombinations not only occur in B cell malignancies, but rather reflect physiological gene rearrangements present in normal human B cells as well. Excision circle analysis and recombination substrate assays can discriminate between single-step vs multistep rearrangements. Using this combined approach, we unraveled that the atypical Vkappa-intronRSS and JkappaRSS-Kde pseudohybrid joints most probably result from ongoing recombination following an initial aberrant JkappaRSS-intronRSS signal joint formation. Based on our observations in normal and malignant human B cells, a model is presented to describe the sequential (classical and atypical) recombination events in the human IGK locus and their estimated relative frequencies (0.2-1.0 vs < 0.03). The initial JkappaRSS-intronRSS signal joint formation (except for Jkappa1RSS-intronRSS) might be a side event of an active V(D)J recombination mechanism, but the subsequent formation of Vkappa-intronRSS and JkappaRSS-Kde pseudohybrid joints can represent an alternative pathway for IGK allele inactivation and allelic exclusion, in addition to classical Ckappa deletions. Although usage of this alternative pathway is limited, it seems essential for inactivation of those IGK alleles that have undergone initial aberrant recombinations, which might otherwise hamper selection of functional Ig L chain proteins.

Validation of BIOMED-2 multiplex PCR tubes for detection of TCRB gene rearrangements in T-cell malignancies

The BIOMED-2 Concerted Action BMH4-CT98-3936 on 'Polymerase chain reaction (PCR)-based clonality studies for early diagnosis of lymphoproliferative disorders' developed standardized PCR protocols for detection of immunoglobulin (Ig) and T-cell receptor (TCR) rearrangements, including TCR beta (TCRB). As no comparable TCRB PCR method pre-existed and only a limited number of samples was tested within the BIOMED-2 study, we initiated this study for further validation of the newly developed TCRB PCR approach by comparing PCR data with previously generated Southern blot (SB) data in a series of 66 immature (ALL) and 36 mature T-cell malignancies. In 91% of cases, concordant PCR and SB results were found. Discrepancies consisted of either failure to detect SB-detected TCRB rearrangements by PCR (6.5%) or detection of an additional non-SB defined rearrangement (2.5%). In 99% of cases (99/100), at least one clonal TCRB rearrangement was detected by PCR in the SB-positive cases. A predominance of complete Vbeta-Jbeta rearrangements was seen in TCRalphabeta(+) T-cell malignancies and CD3-negative T-ALL (100 and 90%, respectively), whereas in TCRgammadelta(+) T-ALL, more incomplete Dbeta-Jbeta TCRB rearrangements were detected (73%). Our results underline the reliability of this new TCRB PCR method and its strategic applicability in clonality diagnostics of lymphoproliferative disorders and MRD studies.

Two dual-color split signal fluorescence in situ hybridization assays to detect t(5;14) involving HOX11L2 or CSX in T-cell acute lymphoblastic leukemia

BACKGROUND AND OBJECTIVES

The t(5;14)(q35;q32) is a novel cryptic translocation in pediatric T-cell acute lymphoblastic leukemia (T-ALL), involving HOX11L2 or CSX on 5q35. The 14q32 breakpoints are heterogeneous. Because the t(5;14)(q35;q32) is hard to detect using conventional karyotyping, it is easily missed in routine diagnostics. Here we describe the development and application of split signal fluorescence in situ hybridization (FISH) assays for both HOX11L2 and CSX, for detection of t(5;14) possibly present in T-ALL patients.

DESIGN AND METHODS

We developed and validated two split signal FISH assays for metaphase and interphase detection of t(5;14) in T-ALL patients. We also investigated the involvement of IGH on 14q32. In addition, HOX11L2 and SIL-TAL1 expression was studied using reverse transcription polymerase chain reaction (RT-PCR).

RESULTS

The FISH assays were validated on cell lines and T-ALL patients. We did not identify cases with a t(5;14)(q35;q32) involving CSX, but we did identify 5 cases of t(5;14) involving HOX11L2 out of 32 T-ALL cases studied; in each case the 14q32 breakpoint was found to be centromeric to the IGH region. All 5 positive cases showed HOX11L2 expression, as did 1 case without t(5;14)(q35;q32). Cases with t(5;14)(q35;q32) involving HOX11L2 did not show TAL1 abnormalities, whereas 5 HOX11L2 negative cases did.

INTERPRETATION AND CONCLUSIONS

Using the newly developed and validated FISH probe sets, we identified 5 new cases of t(5;14) involving HOX11L2 both on metaphases and interphases. The incidence of the t(5;14)(q35;q32) involving CSX is probably low. RT-PCR results suggest that TAL1 and HOX11L2 expression, or TAL1 aberrations and the t(5;14)(q35;q32) involving HOX11L2 are mutually exclusive.

Split-signal FISH for detection of chromosome aberrations in acute lymphoblastic leukemia

Chromosome aberrations are frequently observed in precursor-B-acute lymphoblastic leukemias (ALL) and T-cell acute lymphoblastic leukemias (T-ALL). These translocations can form leukemia-specific chimeric fusion proteins or they can deregulate expression of an (onco)gene, resulting in aberrant expression or overexpression. Detection of chromosome aberrations is an important tool for risk classification. We developed rapid and sensitive split-signal fluorescent in situ hybridization (FISH) assays for six of the most frequent chromosome aberrations in precursor-B-ALL and T-ALL. The split-signal FISH approach uses two differentially labeled probes, located in one gene at opposite sites of the breakpoint region. Probe sets were developed for the genes TCF3 (E2A) at 19p13, MLL at 11q23, ETV6 at 12p13, BCR at 22q11, SIL-TAL1 at 1q32 and TLX3 (HOX11L2) at 5q35. In normal karyotypes, two colocalized green/red signals are visible, but a translocation results in a split of one of the colocalized signals. Split-signal FISH has three main advantages over the classical fusion-signal FISH approach, which uses two labeled probes located in two genes. First, the detection of a chromosome aberration is independent of the involved partner gene. Second, split-signal FISH allows the identification of the partner gene or chromosome region if metaphase spreads are present, and finally it reduces false-positivity.

Receptor editing and marginal zone B cell development are regulated by the helix-loop-helix protein, E2A

Previous studies have indicated that the E2A gene products are required to initiate B lineage development. Here, we demonstrate that E2A^+/− B cells that express an autoreactive B cell receptor fail to mature due in part to an inability to activate secondary immunoglobulin (Ig) light chain gene rearrangement. Both RAG1/2 gene expression and RS deletion are severely defective in E2A^+/− mice. Additionally, we demonstrate that E2A^+/− mice show an increase in the proportion of marginal zone B cells with a concomitant decrease in the proportion of follicular B cells. In contrast, Id3-deficient splenocytes show a decline in the proportion of marginal zone B cells. Based on these observations, we propose that E-protein activity regulates secondary Ig gene rearrangement at the immature B cell stage and contributes to cell fate determination of marginal zone B cells. Additionally, we propose a model in which E-proteins enforce the developmental checkpoint at the immature B cell stage.

Clonal proliferation of T-Cell large granular lymphocytes

BACKGROUND

T-cell large granular lymphocyte (T-LGL) leukemia is a disorder only rarely reported in children. We diagnosed a new case of a clonal T-LGL proliferation in a 6-year-old girl presenting with severe neutropenia and pure red blood cell aplasia (PRCA).

PROCEDURE

Flow cytometric analysis including TCR-Vbeta repertoire analysis and molecular studies using reverse transcriptase polymerase chain reaction (RT-PCR), PCR heteroduplex analysis and GeneScan analysis were performed to investigate the clonal nature of the T-LGL.

RESULTS

Flow cytometric analysis revealed a Vbeta3 clonal nature. Molecular studies identified a clonal Vbeta3-Cbeta RT-PCR product. Both PCR heteroduplex analysis and GeneScan analysis found clonal TCRB and TCRG gene rearrangements.

CONCLUSIONS

An underlying T-LGL leukemia should be investigated in the diagnostic evaluation of acquired PRCA and neutropenia in young children. Both flow cytometric and molecular analyses can be used to establish the clonal nature of T-LGL.

Design and standardization of PCR primers and protocols for detection of clonal immunoglobulin and T-cell receptor gene recombinations in suspect lymphoproliferations: report of the BIOMED-2 Concerted Action BMH4-CT98-3936

In a European BIOMED-2 collaborative study, multiplex PCR assays have successfully been developed and standardized for the detection of clonally rearranged immunoglobulin (Ig) and T-cell receptor (TCR) genes and the chromosome aberrations t(11;14) and t(14;18). This has resulted in 107 different primers in only 18 multiplex PCR tubes: three VH-JH, two DH-JH, two Ig kappa (IGK), one Ig lambda (IGL), three TCR beta (TCRB), two TCR gamma (TCRG), one TCR delta (TCRD), three BCL1-Ig heavy chain (IGH), and one BCL2-IGH. The PCR products of Ig/TCR genes can be analyzed for clonality assessment by heteroduplex analysis or GeneScanning. The detection rate of clonal rearrangements using the BIOMED-2 primer sets is unprecedentedly high. This is mainly based on the complementarity of the various BIOMED-2 tubes. In particular, combined application of IGH (VH-JH and DH-JH) and IGK tubes can detect virtually all clonal B-cell proliferations, even in B-cell malignancies with high levels of somatic mutations. The contribution of IGL gene rearrangements seems limited. Combined usage of the TCRB and TCRG tubes detects virtually all clonal T-cell populations, whereas the TCRD tube has added value in case of TCRgammadelta(+) T-cell proliferations. The BIOMED-2 multiplex tubes can now be used for diagnostic clonality studies as well as for the identification of PCR targets suitable for the detection of minimal residual disease.

Somatostatin receptors in malignant lymphomas: targets for radiotherapy?

Somatostatin (SS) receptor (sst) scintigraphy is widely used in the visualization of neuroendocrine tumors expressing sst, and radiotherapy using radionuclide-labeled SS analogs has been introduced for treatment of patients with neuroendocrine tumors. Previous sst scintigraphy studies revealed that malignant lymphomas can also be visualized using this technique. The question has been addressed whether lymphomas might also be possible targets for radiotherapy using radionuclide-labeled SS analogs. Therefore, we investigated in vitro the characteristics of lymphoma tissues and lymphoid cell lines to evaluate whether lymphomas can be targets for radiotherapy.

METHODS

Six orbital lymphomas, 2 Hodgkin's lymphomas, and 2 non-Hodgkin's lymphomas from the neck region were collected. Reverse transcriptase polymerase chain reaction (RT-PCR) and quantitative RT-PCR were performed to detect and quantify the expression of sst(1-5) mRNA. Receptor autoradiography studies using [(125)I-Tyr(3)]octreotide were performed to evaluate binding to sst on cryostat sections of lymphomas. Immunohistochemistry was used to investigate expression of sst(2) and sst(3). Membrane binding studies and in vitro internalization experiments using [(125)I-Tyr(3)]octreotide were performed to study binding and uptake of [(125)I-Tyr(3)]octreotide by lymphoid cell lines (JY, TMM, APD) and primary cells derived from a B-cell-derived chronic lymphatic leukemia.

RESULTS

A selective expression of sst(2) and sst(3) messenger RNA (mRNA) was demonstrated. By quantitative RT-PCR, expression levels of sst(2) and sst(3) mRNA were relatively low. Autoradiography studies revealed low binding of [(125)I-Tyr(3)]octreotide, whereas immunoreactivity could not be detected for sst(2) and sst(3) by immunohistochemistry. On the lymphoid cell lines only low numbers of high-affinity SS binding sites were found. In vitro, uptake of [(125)I-Tyr(3)]octreotide by these cells was also very low.

CONCLUSION

On the basis of our findings, we conclude that lymphomas do not appear to be candidates for radiotherapy using radionuclide-labeled SS analogs. However, lymphomas are highly radiosensitive tumors and further clinical studies should be performed to evaluate whether the low receptor density is sufficient for targeting treatment in these tumors.

Regulation of MHC class II expression in human T-cell malignancies

Expression of major histocompatibility complex (MHC) class II molecules in human activated T cells is under normal circumstances regulated exclusively by the CIITA-PIII subtype of the class II transactivator (CIITA). In this study, we show that the absence of MHC class II expression in leukemic T cells was due to a lack of expression of CIITA, whereas in T-lymphoma cells, expression of CIITA correlated with expression of MHC class II. Interestingly, activation of a CIITA-promoter (P)III-reporter construct was not affected in leukemic T cells. This revealed that the absence of endogenous CIITA expression was not caused by a lack of transcription factors critical for CIITA-PIII activation but suggests the involvement of an epigenetic silencing mechanism. Subsequent analysis showed that the lack of human leukocyte antigen-DR (HLA-DR) expression correlated with hypermethylation of CIITA-PIII in leukemic T-cell lines and in primary T-cell acute lymphoblastic leukemia (T-ALL) and a T-cell prolymphocytic leukemia (T-PLL). Treatment of leukemic T-cell lines with a demethylation agent showed re-expression of CIITA-PIII and HLA-DRA. Furthermore, in vitro methylation of CIITA-PIII and subsequent assessment of CIITA-PIII activity in Jurkat leukemic T cells resulted in reduction of constitutive and CREB-1 (cyclic adenosine monophosphate [cAMP]-response element binding protein 1)-induced promoter activity. Together, these results argue for an important role of DNA hyper-methylation in the control of CIITA expression in leukemic T cells.

DNA microarrays for comparison of gene expression profiles between diagnosis and relapse in precursor-B acute lymphoblastic leukemia: choice of technique and purification influence the identification of potential diagnostic markers

Microarrays for gene expression profiling are rapidly becoming important research tools for the identification of novel markers, for example, for novel classification of leukemias and lymphomas. Here, we review the considerations and infrastructure for microarray experiments. These considerations are illustrated via a microarray-based comparison of gene expression profiles of paired diagnosis-relapse samples from patients with precursor-B acute lymphoblastic leukemia (ALL), who relapsed during therapy or after completion of treatment. Initial experiments showed that several seemingly differentially expressed genes were actually derived from contaminating non-leukemic cells, particularly myeloid cells and T-lymphocytes. Therefore, we purified the ALL cells of the diagnosis and relapse samples if their frequency was lower than 95%. Furthermore, we observed in earlier studies that extra RNA amplification leads to skewing of particular gene transcripts. Sufficient (non-amplified) RNA of purified and paired diagnosis-relapse samples was obtained from only seven cases. The gene expression profiles were evaluated with Affymetrix U95A chips containing 12 600 human genes. These diagnosis-relapse comparisons revealed only a small number of genes (n=6) that differed significantly in expression: mostly signaling molecules and transcription factors involved in cell proliferation and cell survival were highly upregulated at relapse, but we did not observe any increase in drug-resistance markers. This finding fits with the observation that tumors with a high proliferation index have a poor prognosis. The genes that changed between diagnosis and relapse are currently not in use as diagnostic or disease progression markers, but represent potential new markers for such applications. Leukemia (2003) 17, 1324-1332. doi:10.1038/sj.leu.2402974