Easy detection of all T cell receptor gamma (TCRG) gene rearrangements by Southern blot analysis: recommendations for optimal results

Successful treatment of severe splenic lymphoma‑associated hemophagocytic syndrome by splenectomy and subsequent chemotherapy: A case report

Hemophagocytic lymphohistiocytosis (HLH) represents a fatal immunopathology derived from excessive inflammatory reactions. In particular, lymphoma-associated hemophagocytic syndrome (LAHS) is associated with a dismal prognosis. The current study presented a challenging case of splenic LAHS. A 71-year-old man presented with fatigue and anorexia. Laboratory test results revealed anemia, thrombocytopenia, lactate dehydrogenase elevation and markedly elevated levels of ferritin (6,210 ng/ml) and soluble interleukin 2 receptor (sIL-2R; 11,328 U/ml). Abdominal computed tomography revealed marked splenomegaly, while fluorodeoxyglucose positron emission tomography revealed increased tracer uptake in the spleen. An elective splenectomy was performed, which led to the diagnosis of B-cell splenic lymphoma with transformation from indolent to aggressive lymphoma. Prior to the splenectomy, thrombocytopenia and hepatic dysfunction with rapidly progressing jaundice appeared, accompanying further elevation of ferritin (25,197 ng/ml) and sIL-2R levels (30,420 U/ml). On postoperative day 5, the patient was transferred to a tertiary care institution and corticosteroid pulse therapy was immediately initiated after establishing the diagnosis of LAHS. Liver dysfunction gradually recovered and subsequent chemotherapy resulted in complete remission with improved performance status. At eight months after the onset, the patient remains alive without any signs of residual lymphoma. Although splenic lymphoma typically manifests with low-grade lymphoma, it can transform into high-grade lymphoma associated with severe complications, such as HLH and multiple organ failure. In this case, splenectomy assisted in not only establishing the diagnosis but also in tumor cytoreduction before commencing chemotherapy. Through interdisciplinary collaboration, the patient was successfully treated by performing a timely splenectomy, followed by steroid pulse therapy and chemotherapy.

EOSAL-CNV for Easy and Rapid Detection of CNVs by Fragment Analysis : EOSAL: A Fast and Reliable New Method for CNV Detection

Copy number variations (CNVs) are a type of genetic variation involving from 50 base pairs (bps) to millions of bps and, in a general point of view, can include alterations of complete chromosomes. As CNVs mean the gain or loss of DNA sequences, their detection requires specific techniques and analysis. We have developed Easy One-Step Amplification and Labeling for CNV Detection (EOSAL-CNV) by fragment analysis in a DNA sequencer. The procedure is based on a single PCR reaction for amplification and labeling of all fragments included. The protocol includes specific primers for the amplification of the regions of interest with a tail in each of the primers (one for forward and another for the reverse primers) together with primers for tail amplification. One of the primers for tail amplification is labeled with a fluorophore, allowing the amplification and labeling in the same reaction. Combination of several tail pairs and labels allows the detection of DNA fragment by different fluorophores and increases the number of fragments that can be analyzed in one reaction. PCR products can be analyzed without any purification on a DNA sequencer for fragment detection and quantification. Finally, simple and easy calculations allow the detection of fragments with deletions or extra copies. The use of EOSAL-CNV allows simplifying and reducing costs in sample analysis for CNV detection.

The Value of Flow Cytometry Clonality in Large Granular Lymphocyte Leukemia

Simple Summary

Large granular lymphocyte (LGL) leukemia, a lymphoproliferative disease, is characterized by an increased frequency of large-sized lymphocytes with typical expression of T-cell receptor (TCR) αβ, CD3, CD8, CD16, CD45RA, and CD57, and with the expansion of one to three subfamilies of the TCR variable β chain reflecting gene rearrangements. Molecular analysis remains the gold standard for confirmation of TCR clonality; however, flow cytometry is time and labor saving, and can be associated with simultaneous investigation of other surface markers. Moreover, Vβ usage by flow cytometry can be employed for monitoring clonal kinetics during treatment and follow-up of LGL leukemia patients.

Abstract

Large granular lymphocyte (LGL) leukemia is a lymphoproliferative disorder of mature T or NK cells frequently associated with autoimmune disorders and other hematological conditions, such as myelodysplastic syndromes. Immunophenotype of LGL cells is similar to that of effector memory CD8⁺ T cells with T-cell receptor (TCR) clonality defined by molecular and/or flow cytometric analysis. Vβ usage by flow cytometry can identify clonal TCR rearrangements at the protein level, and is fast, sensitive, and almost always available in every Hematology Center. Moreover, Vβ usage can be associated with immunophenotypic characterization of LGL clone in a multiparametric staining, and clonal kinetics can be easily monitored during treatment and follow-up. Finally, Vβ usage by flow cytometry might identify LGL clones silently underlying other hematological conditions, and routine characterization of Vβ skewing might identify recurrent TCR rearrangements that might trigger aberrant immune responses during hematological or autoimmune conditions.

A new diagnostic algorithm using biopsy specimens in adult T-cell leukemia/lymphoma: combination of RNA in situ hybridization and quantitative PCR for HTLV-1

Histopathological distinction between adult T-cell leukemia/lymphoma (ATLL) and other T-cell neoplasms is often challenging. The current gold standard for the accurate diagnosis of ATLL is the Southern blot hybridization (SBH) assay, which detects clonal integration of human T-cell leukemia virus type I (HTLV-1) provirus. However, SBH cannot be performed with small biopsy or formalin-fixed paraffin-embedded (FFPE) tissue samples because this assay requires a large amount of DNA without degradation. Here we developed a new diagnostic algorithm for the accurate diagnosis of ATLL using FFPE samples. This method combines two HTLV-1 detection assays, namely, ultrasensitive RNA in situ hybridization using RNAscope for HTLV-1 bZIP factor (HBZ-RNAscope), and quantitative PCR targeting the tax gene (tax-qPCR). We analyzed 119 FFPE tissue specimens (62 ATLL, and 57 non-ATLL, including 41 HTLV-1 carriers) and compared them with the SBH results using the corresponding fresh-frozen samples. As a result, tax-qPCR had a higher ATLL identification rate than HBZ-RNAscope (88% [52/59], and 63% [39/62], respectively). However, HBZ-RNAscope clearly visualized the localization of HTLV-1-infected tumor cells and its identification rate increased to 94% (17/18) when the analysis was limited to samples up to 2 years old, indicating its usefulness in the daily diagnosis. The diagnostic algorithm combining these two assays successfully evaluated 94% (112/119) of samples and distinguished ATLL from non-ATLL cases including HTLV-1 carriers with 100% sensitivity and specificity. This method is expected to replace SBH and increase the accuracy of the diagnosis of ATLL.

STAT3 mutation and its clinical and histopathologic correlation in T-cell large granular lymphocytic leukemia

Although T-cell large granular lymphocytic leukemia (T-LGLL) is a clinically indolent disorder, patients with moderate to severe cytopenia require therapeutic intervention. The recent discovery of STAT3 mutations has shed light on the genetic basis of T-LGLL pathogenesis. However, the association of STAT3 mutational status with patients' clinical, histopathologic, and other laboratory features has not been thoroughly evaluated in T-LGLL. In this study, STAT3 mutations were identified in 18 of 36 patients with T-LGLL (50%), including Y640F (12/18, 66.7%), N647I (3/18, 16.7%), E638Q (1/18, 5.6%), I659L (1/18, 5.6%), and K657R (1/18, 5.6%). Interestingly, pure red cell aplasia was seen exclusively in T-LGLL patients without STAT3 mutations (6/15 in the wild-type STAT3 group versus 0/13 in the mutant STAT3 group; P = .02); these patients also were the only responders to T-LGLL therapy (mainly cyclophosphamide) in wild-type STAT3 group. Patients harboring STAT3 mutations were more prone to rheumatoid arthritis (4/13 versus 0/15 in the wild-type STAT3 group; P = .04), frequently requiring therapy for neutropenia/neutropenia-associated infections, and demonstrated good therapeutic responses to methotrexate. No significant differences were seen in complete blood count, flow cytometric immunophenotypic features, T-cell receptor γ V-J rearrangement repertoire, and bone marrow biopsy morphology among the STAT3-mutation and wild-type groups other than significantly larger tumor burden in patients with STAT3 mutations. The distinct disease association and therapeutic responses observed in patients with mutant and wild-type STAT3 warrant further investigation to elucidate the underlying mechanisms. They also highlight the importance of identifying STAT3 mutational status in patients with T-LGLL, which may aid in clinical therapeutic choice.

Molecular Testing of Lymphoproliferative Disorders: Current Status and Perspectives

Molecular pathologic testing plays an important role for the diagnosis, prognostication and decision of treatment strategy in lymphoproliferative disease. Here, we briefly review the molecular tests currently used for lymphoproliferative disease and those which will be implicated in clinical practice in the near future. Specifically, this guideline addresses the clonality test for B- and T-cell proliferative lesions, molecular cytogenetic tests for malignant lymphoma, determination of cell-of-origin in diffuse large B-cell lymphoma, and molecular genetic alterations incorporated in the 2016 revision of the World Health Organization classification of lymphoid neoplasms. Finally, a new perspective on the next-generation sequencing for diagnostic, prognostic, and therapeutic purpose in malignant lymphoma will be summarized.

Minimal residual disease in acute lymphoblastic leukemia: optimal methods and clinical relevance, pitfalls and recent approaches

After advances in experimental and clinical testing, minimal residual disease (MRD) assay results are considered a determining factor in treatment of acute lymphoblastic leukemia patients. According to MRD assay results, bone marrow (BM) leukemic burden and the rate of its decline after treatment can be directly evaluated. Detailed knowledge of the leukemic burden in BM can minimize toxicity and treatment complications in patients by tailoring the therapeutic dose based on patients' conditions. In addition, reduction of MRD before allo-HSCT is an important prerequisite for reception of transplant by the patient. In direct examination of MRD by morphological methods (even by a professional hematologist), leukemic cells can be under- or over-estimated due to similarity with hematopoietic precursor cells. As a result, considering the importance of MRD, it is necessary to use other methods including flow cytometry, polymerase chain reaction (PCR) amplification and RQ-PCR to detect MRD. Each of these methods has its own advantages and disadvantages in terms of accuracy and sensitivity. In this review article, different MRD assay methods and their sensitivity, correlation of MRD assay results with clinical symptoms of the patient as well as pitfalls in results of these methods are evaluated. In the final section, recent advances in MRD have been addressed.

The evolution of clonality testing in the diagnosis and monitoring of hematological malignancies

Currently, distinguishing between benign and malignant lymphoid proliferations is based on a combination of clinical characteristics, cyto/histomorphology, immunophenotype and the identification of well-defined chromosomal aberrations. However, such diagnoses remain challenging in 10-15% of cases of lymphoproliferative disorders, and clonality assessments are often required to confirm diagnostic suspicions. In recent years, the development of new techniques for clonality detection has allowed researchers to better characterize, classify and monitor hematological neoplasms. In the past, clonality was primarily studied by performing Southern blotting analyses to characterize rearrangements in segments of the IG and TCR genes. Currently, the most commonly used method in the clinical molecular diagnostic laboratory is polymerase chain reaction (PCR), which is an extremely sensitive technique for detecting nucleic acids. This technique is rapid, accurate, specific, and sensitive, and it can be used to analyze small biopsies as well as formalin-fixed paraffin-embedded samples. These advantages make PCR-based approaches the current gold standard for IG/TCR clonality testing. Since the completion of the first human genome sequence, there has been a rapid development of technologies to facilitate high-throughput sequencing of DNA. These techniques have been applied to the deep characterization and classification of various diseases, patient stratification, and the monitoring of minimal residual disease. Furthermore, these novel approaches have the potential to significantly improve the sensitivity and cost of clonality assays and post-treatment monitoring of B- and T-cell malignancies. However, more studies will be required to demonstrate the utility, sensitivity, and benefits of these methods in order to warrant their adoption into clinical practice. In this review, recent developments in clonality testing are examined with an emphasis on highly sensitive systems for improving diagnostic workups and minimal residual disease assessments.

Clonal evolution of adult T-cell leukemia/lymphoma takes place in the lymph nodes

Adult T-cell leukemia/lymphoma (ATLL) is the neoplasm caused by human T-cell leukemia virus type 1 (HTLV-1). We performed oligo-array comparative genomic hybridization (CGH) against paired samples comprising peripheral blood (PB) and lymph node (LN) samples from 13 patients with acute ATLL. We found that the genome profiles of the PB frequently differed from those of the LN samples. The results showed that 9 of 13 cases investigated had a log2 ratio imbalance among chromosomes, and that chromosome imbalances were more frequent in LN samples. Detailed analysis revealed that the imbalances were likely caused by the presence of multiple subclones in the LN samples. Five of 13 cases showed homozygous loss regions in PB samples, which were not found in the LN samples, indicating that tumors in the PB were derived from LN subclones in most cases. Southern blot analysis of TCRγ showed that these multiple subclones originated from a common clone. We concluded that in many ATLL cases, multiple subclones in the LNs originate from a common clone, and that a selected subclone among the LN subclones appears in the PB.

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.

Comparative investigations of T cell receptor gamma gene rearrangements in frozen and formalin-fixed paraffin wax-embedded tissues by capillary electrophoresis

AIM

To compare clonal T cell receptor gamma (TCRgamma) gene rearrangements in frozen and formalin-fixed paraffin wax-embedded (FFPE) tissue, using capillary electrophoresis for use in diagnostics, as T cell lymphomas may be difficult to diagnose by conventional methods.

METHODS

The DNA for PCR was extracted from frozen and FFPE tissue, cell lines and blood. PCR primers Vgamma1-8, Vgamma9, Vgamma10 or Vgamma11 (5' end labelled) combined with a mixture of JgammaP1/JgammaP/JgammaP2/Jgamma2 (unlabelled) were used. Monoclonal cases were sequenced and clonality, reproducibility, sensitivity and specificity analyses were carried out.

RESULTS

In all cases the molecular test was found to be in agreement with the histological diagnosis. Discrepancies were found between frozen and FFPE tissue in 18 of 56 (32%) tests. The method was highly reproducible. The sensitivity was found to be 0.5% for cell lines and 1% for patient specimens and the specificity 100%. The junctional region between the Vgamma and Jgamma segments was specific for each patient.

CONCLUSIONS

Capillary electrophoresis of PCR products from frozen and FFPE tissue is suitable for detecting clonal TCRgamma gene rearrangements. It is important, however, to correlate the results with conventional morphological and immunohistochemical 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.

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.

Acute lymphoblastic leukemia followed by a clonally-unrelated EBV-positive non-Hodgkin lymphoma and a clonally-related myelomonocytic leukemia cutis

BACKGROUND

Complicating malignant hematopoietic proliferations might severely hamper the course of acute lymphoblastic leukemia (ALL) in patients with an otherwise good prognosis. It is important to distinguish whether such neoplastic proliferations represent ALL relapses or secondary treatment-related malignancies.

PROCEDURE

We present an 11-year-old girl with precursor-B-ALL in whom maintenance treatment was complicated by an isolated ALL relapse in the brain, nodular lymphoproliferations in the liver, and an isolated myelo-monocytic leukemia cutis. All these hemato-oncologic malignancies occurred in the background of a secondary immunodeficiency, most likely caused by cytotoxic treatment.

RESULTS AND CONCLUSIONS

Using a stepwise molecular approach, we were able to demonstrate that the liver infiltrates were Epstein-Barr virus (EBV)-positive, contained monoclonal mature B-cells with immunoglobulin heavy chain gene (IGH) gene rearrangements unrelated to the primary ALL, and thus represented a true secondary non-Hodgkin lymphoma (NHL). In contrast, the skin infiltrates consisted of myelo-monocytic cells with clonal IGH and T-cell receptor gamma gene rearrangements, identical to the precursor-B-ALL blasts at diagnosis. Thus, the disease course of the precursor-B-ALL patient was complicated by two different isolated extramedullary relapses (brain and skin) and a secondary EBV(+) B-NHL.

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.

Comparative analysis of T-cell receptor gene rearrangements at diagnosis and relapse of T-cell acute lymphoblastic leukemia (T-ALL) shows high stability of clonal markers for monitoring of minimal residual disease and reveals the occurrence of second T-ALL

A total of 28 children and nine adults with relapsed T-ALL were analyzed for the configuration of their T-cell receptor (TCR) and TAL1 genes at diagnosis and relapse to evaluate their stability throughout the disease course. A total of 150 clonal TCR and TAL1 gene rearrangements were identified in the 37 patients at diagnosis. In 65% of cases all rearrangements and in 27% of cases most rearrangements found at diagnosis were preserved at relapse. Two children with unusually late T-ALL recurrences displayed completely different TCR gene rearrangement sequences between diagnosis and relapse. This indicates that a proportion of very late T-ALL recurrences might represent second T-ALL. Specifically, 88% of clonal rearrangements identified at diagnosis in truly relapsed T-ALL were preserved at relapse. This is significantly higher as compared to previously studied precursor-B-ALL ( approximately 70%). Thus, from biological point of view, immunogenotype of T-ALL is more stable as compared with precursor-B-ALL. The overall stability of TCR gene rearrangements was higher in adult T-ALL (97%) than in childhood T-ALL (86%). Based on the stability of TCR gene rearrangements, we propose a strategy for PCR target selection (TCRD+TAL1 --> TCRB --> TCRG), which probably allows reliable minimal residual disease detection in all T-ALL patients.

Age-related patterns of immunoglobulin and T-cell receptor gene rearrangements in precursor-B-ALL: implications for detection of minimal residual disease

Detailed Southern blot and PCR analysis of Ig heavy (IGH), Ig kappa (IGK), T-cell receptor delta (TCRD), and TCR gamma (TCRG) genes were performed in 289 children with precursor-B-ALL in order to determine age-related Ig/TCR patterns and their implications for detection of minimal residual disease (MRD). Overall, IGH, IGK, TCRD, and TCRG gene rearrangements were detected in 98, 62, 90, and 58% of patients, respectively. The frequency of IGH and TCRD rearrangements was independent of rearrangements in one of the other three loci, whereas Ig kappa deleting element and TCRG rearrangements preferentially coincided. Southern blot analysis showed that oligoclonality of IGH, IGK, and TCRD was interrelated, that is, oligoclonality in one locus was related with a higher chance of oligoclonality in another locus. Combined Southern blot and PCR analysis revealed that Ig/TCR patterns were age related: children younger than 3 years or older than 10 years showed a higher prevalence of incomplete IGH rearrangements and a lower prevalence of IGK deletions, TCRG rearrangements, and TCRD rearrangements than children between 3 and 10 years. In addition, IGH oligoclonality was more frequent in the younger and older children. These age-related differences probably reflect ALL subsets with different cellular origin and differences in the duration of the preleukemic phase between the initial and final leukemogenetic hit. The more immature Ig/TCR gene rearrangement pattern in children younger than 3 years or older than 10 years resulted in relatively low numbers of potential MRD-PCR targets per patient, particularly if only monoclonal rearrangements were taken into account. These data provide insight into the immunobiological characteristics of Ig/TCR gene rearrangements in childhood precursor-B-ALL and form a useful basis for designing improved strategies for the identification and selection of MRD-PCR targets.

Fusion gene transcripts and Ig/TCR gene rearrangements are complementary but infrequent targets for PCR-based detection of minimal residual disease in acute myeloid leukemia

PCR-based monitoring of minimal residual disease (MRD) in acute leukemias can be achieved via detection of fusion gene transcripts of chromosome aberrations or detection of immunoglobulin (Ig) and T cell receptor (TCR) gene rearrangements. We wished to assess whether both PCR targets are complementary in acute myeloid leukemia (AML). We investigated 105 consecutive AML cases for the presence of fusion gene transcripts by reverse transcriptase polymerase chain reaction (RT-PCR): AML1-ETO associated with t(8;21), CBFB-MYH11 with inv(16), PML-RARA with t(15;17), BCR-ABL with t(9;22), and MLL-AF4 with t(4;11). In 17 out of 105 AML cases (16%), fusion gene transcripts were found. Ninety-five of these AML patients (13 with fusion gene transcripts) were also investigated for the presence of IGH, IGK, TCRG and TCRD rearrangements by Southern blot and/or PCR heteroduplex analysis and sequencing. In nine out of 95 patients (9.5%), such rearrangements were found. Combined data revealed that only one patient with a fusion gene transcript had a coexistent Ig/TCR rearrangement. The nine AML patients with Ig/TCR rearrangements, as well as five additional AML patients from a previous study were investigated in more detail, revealing that Ig/TCR rearrangements in AML are immature and unusual. The presence of Ig/TCR rearrangements in AML did not correlate with RAG gene expression levels as determined by real-time quantitative PCR. In conclusion, fusion gene transcripts and Ig/TCR rearrangements are infrequent, but complementary MRD-PCR targets in AML.

Basic helix-loop-helix proteins E2A and HEB induce immature T-cell receptor rearrangements in nonlymphoid cells

T-cell receptor (TCR) gene rearrangements are mediated via V(D)J recombination, which is strictly regulated during lymphoid differentiation, most probably through the action of specific transcription factors. Investigated was whether cotransfection of RAG1 and RAG2 genes in combination with lymphoid transcription factors can induce TCR gene rearrangements in nonlymphoid human cells. Transfection experiments showed that basic helix-loop-helix transcription factors E2A and HEB induce rearrangements in the TCRD locus (Ddelta2-Ddelta3 and Vdelta2-Ddelta3) and TCRG locus (psi Vgamma7-Jgamma2.3 and Vgamma8-Jgamma2.3). Analysis of these rearrangements and their circular excision products revealed some peculiar characteristics. The Vdelta2-Ddelta3 rearrangements were formed by direct coupling without intermediate Ddelta2 gene segment usage, and most Ddelta2-Ddelta3 recombinations occurred via direct coupling of the respective upstream and downstream recombination signal sequences (RSSs) with deletion of the Ddelta2 and Ddelta3 coding sequences. Subsequently, the E2A/HEB-induced TCR gene recombination patterns were compared with those in early thymocytes and acute lymphoblastic leukemias of T- and B-lineage origin, and it was found that the TCR rearrangements in the transfectants were early (immature) and not necessarily T-lineage specific. Apparently, some parts of the TCRD (Vdelta2-Ddelta region) and TCRG genes are accessible for recombination not only in T cells, but also in early B-cells and even in nonlymphoid cells if the appropriate transcription factors are present. The transfection system described here appeared to be useful for studying the accessibility of immunoglobulin and TCR genes for V(D)J recombination, but might also be applied to study the induction of RSS-mediated chromosome aberrations.

Molecular and flow cytometric analysis of the Vbeta repertoire for clonality assessment in mature TCRalphabeta T-cell proliferations

Clonality assessment through Southern blot (SB) analysis of TCRB genes or polymerase chain reaction (PCR) analysis of TCRG genes is important for diagnosing suspect mature T-cell proliferations. Clonality assessment through reverse transcription (RT)-PCR analysis of Vbeta-Cbeta transcripts and flow cytometry with a Vbeta antibody panel covering more than 65% of Vbeta domains was validated using 28 SB-defined clonal T-cell receptor (TCR)alphabeta(+) T-ALL samples and T-cell lines. Next, the diagnostic applicability of the V(beta) RT-PCR and flow cytometric clonality assays was studied in 47 mature T-cell proliferations. Clonal Vbeta-Cbeta RT-PCR products were detected in all 47 samples, whereas single Vbeta domain usage was found in 31 (66%) of 47 patients. The suspect leukemic cell populations in the other 16 patients showed a complete lack of Vbeta monoclonal antibody reactivity that was confirmed by molecular data showing the usage of Vbeta gene segments not covered by the applied Vbeta monoclonal antibodies. Nevertheless, this could be considered indirect evidence for the "clonal" character of these cells. Remarkably, RT-PCR revealed an oligoclonal pattern in addition to dominant Vbeta-Cbeta products and single Vbeta domain expression in many T-LGL proliferations, providing further evidence for the hypothesis raised earlier that T-LGL derive from polyclonal and oligoclonal proliferations of antigen-activated cytotoxic T cells. It is concluded that molecular Vbeta analysis serves to assess clonality in suspect T-cell proliferations. However, the faster and cheaper Vbeta antibody studies can be used as a powerful screening method for the detection of single Vbeta domain expression, followed by molecular studies in patients with more than 20% single Vbeta domain expression or large suspect T-cell populations (more than 50%-60%) without Vbeta reactivity.

Molecular discrimination between relapsed and secondary acute lymphoblastic leukemia: proposal for an easy strategy

BACKGROUND

Discrimination between late relapse of acute lymphoblastic leukemia (ALL) and secondary ALL might be clinically important, because the former might still respond favorably to chemotherapy and/or bone marrow transplantation, whereas secondary ALL is associated with poor prognosis.

PROCEDURE

We present a pre-B-ALL patient in whom disease recurred 2 years after completion of treatment. Differences in cytomorphology and immunophenotyping raised a suspicion of secondary ALL. We performed detailed molecular studies of immunoglobulin and T-cell receptor genes for discrimination between relapsed and secondary ALL.

RESULTS

Southern blot analysis showed an oligoclonal immunoglobulin heavy chain (IGH) gene configuration at diagnosis and a monoclonal configuration at relapse. The size of one of the rearranged bands at relapse was identical to one of the faint rearranged bands at diagnosis. However, heteroduplex PCR analysis demonstrated that none of the clonal IGH gene rearrangements at diagnosis and at relapse was fully identical. Sequencing of several clonal PCR products revealed an identical DH6-13<-->JH6b junction shared by two different rearrangements at diagnosis and one rearrangement at relapse, thereby proving the clonal relationship between diagnosis and late relapse in this patient.

CONCLUSIONS

We propose a stepwise molecular approach for discrimination between relapsed and secondary ALL based on the rapid and cheap heteroduplex PCR technique, including mixing of clonal (homoduplex) PCR products identified at diagnosis and at relapse. Direct sequencing and comparative sequence analysis of IGH gene rearrangements at diagnosis and at relapse should be regarded as an ultimate standard, but can be limited to the rare cases, in which no identical clonal PCR products at diagnosis and at relapse were detected with the mixed heteroduplex PCR analyses.

Flow cytometric analysis of the Vbeta repertoire in healthy controls

BACKGROUND

Analysis of the T-cell receptor (TCR)-Vbeta repertoire has been used for studying selective T-cell responses in autoimmune disease, alloreactivity in transplantation, and protective immunity against microbial and tumor antigens. For the interpretation of these studies, we need information about the Vbeta repertoire usage in healthy individuals.

METHODS

We analyzed blood T-lymphocyte (sub)populations of 36 healthy controls (age range: from neonates to 86 years) with a carefully selected most complete panel of 22 Vbeta monoclonal antibodies, which together recognized 70-75% of all blood TCRalphabeta(+) T lymphocytes. Subsequently, we developed a six-tube test kit with selected Vbeta antibody combinations for easy and rapid detection of single ("clonal") Vbeta domain usage in large T-cell expansions.

RESULTS

The mean values of the Vbeta repertoire usage were stable during aging in blood TCRalphabeta(+) T lymphocytes as well as in the CD4(+) and CD8(+) T-cell subsets, although the standard deviations increased in the elderly. The increased standard deviations were caused by the occurrence of oligoclonal T-cell expansions in the elderly, mainly consisting of CD8(+) T lymphocytes. The 15 detected T-cell expansions did not reach 40% of total TCRalphabeta(+) T lymphocytes and represented less than 0.4 x 10(9) cells per liter in our study. Vbeta usage of the CD4(+) and CD8(+) subsets was comparable for most tested Vbeta domains, but significant differences (P < 0.01) between the two subsets were found for Vbeta2, Vbeta5.1, Vbeta6.7, Vbeta9.1, and Vbeta22 (higher in CD4(+)), as well as for Vbeta1, Vbeta7.1, Vbeta14, and Vbeta23 (higher in CD8(+)). Finally, single Vbeta domain expression in large T-cell expansions can indeed be detected by the six-tube test kit.

CONCLUSIONS

The results of our study can now be used as reference values in studies on distortions of the Vbeta repertoire in disease states. The six-tube test kit can be used for detection of single Vbeta domain expression in large T-cell expansions (>2.0 x 10(9)/l), which are clinically suspicious of T-cell leukemia.

T cell receptor gamma (TCRG) gene rearrangements in T cell acute lymphoblastic leukemia refelct 'end-stage' recombinations: implications for minimal residual disease monitoring

The T cell receptor gamma (TCRG) gene configuration was established in a large series of 126 T cell acute lymphoblastic leukemia (T-ALL) patients using combined Southern blotting (SB) and heteroduplex PCR analyses. The vast majority of TALL (96%) displayed clonal TCRG gene rearrangements, with biallelic recombination in 91% of patients. A small immature subgroup of CD3- T-ALL (n = 5) had both TCRG genes in germline configuration, three of them having also germline TCRD genes. In five patients (4%) combined SB and PCR results indicated oligoclonality. In five rearrangements detected by SB, the Vgamma gene segment could not be identified suggesting illegitimate recombination. Altogether, 83% of TCRG gene rearrangements involved either the most upstream Vgamma2 gene (including four cases with interstitial deletion of 170 bp in Vgamma2) and/or the most downstream Jgamma2.3 segment, which can be perceived as 'end-stage' recombinations. Comparative analysis of the TCRG gene configuration in the major immunophenotypic subgroups indicated that TCRgammadelta+ T-ALL display a less mature immunogenotype as compared to TCRalphabeta+ and most CD3- cases. This was reflected by a significantly increased usage of the more downstream Vgamma genes and the upstream Jgamma1 segments. Comparison between adult and pediatric T-ALL patients did not show any obvious differences in TCRG gene configuration. The high frequency, easy detectability, rare oligoclonality, and frequent 'end-stage' recombinations make TCRG gene rearrangements principal targets for PCR-based detection of minimal residual disease (MRD) in T-ALL. We propose a simple heteroduplex PCR strategy, applying five primer combinations, which results in the detection of approximately 95% of all clonal TCRG gene rearrangements in T-ALL. This approach enables identification of at least one TCRG target for MRD monitoring in 95% of patients, and even two targets in 84% of T-ALL.