The t(8;14)(q24.1;q32), the cytogenetic hallmark of Burkitt’s lymphoma, is also found, but rarely, in cases of chronic lymphocytic leukemia (CLL). Such translocation typically results in a MYC-IGH@ fusion subsequently deregulating and overexpressing MYC on der 14q32. In CLL, atypical rearrangements resulting in its gain or loss, within or outside of IGH@ or MYC locus, have been reported, but their clinical significance remains uncertain. Herein, we report a 67 year-old male with complex cytogenetic findings of apparently balanced t(8;14) and unreported complex rearrangements of IGH@ and MYC loci. His clinical, morphological and immunophenotypic features were consistent with the diagnosis of CLL.
Interphase FISH studies revealed deletions of 11q22.3 and 13q14.3, and an extra copy of IGH@, indicative of rearrangement. Karyotype analysis showed an apparently balanced t(8;14)(q24.1;q32). Sequential GPG-metaphase FISH studies revealed abnormal signal patterns: rearrangement of IGH break apart probe with the 5’-IGH@ on derivative 8q24.1 and the 3’-IGH@ retained on der 14q; absence of MYC break apart-specific signal on der 8q; and, the presence of unsplit 5’-MYC-3’ break apart probe signals on der 14q. The breakpoint on 8q24.1 was found to be at least 400 Kb upstream of 5’ of MYC. In addition, FISH studies revealed two abnormal clones; one with 13q14.3 deletion, and the other, with concurrent 11q deletion and atypical rearrangements. Chromosome microarray analysis (CMA) detected a 7.1 Mb deletion on 11q22.3-q23.3 including ATM, a finding consistent with FISH results. While no significant copy number gain or loss observed on chromosomes 8, 12 and 13, a 455 Kb microdeletion of uncertain clinical significance was detected on 14q32.33. Immunohistochemistry showed co-expression of CD19, CD5, and CD23, positive ZAP-70 expression and absence of MYC expression. Overall findings reveal an apparently balanced t(8;14) and atypical complex rearrangements involving 3’-IGH@ and a breakpoint at least 400 Kb upstream of MYC, resulting in the relocation of the intact 5’-MYC-3’ from der 8q, and apposition to 3’-IGH@ at der 14q. This case report provides unique and additional cytogenetic data that may be of clinical significance in such a rare finding in CLL. It also highlights the utility of conventional and sequential metaphase FISH in understanding complex chromosome anomalies and their association with other clinical findings in patients with CLL. To the best of our knowledge, this is the first CLL reported case with such an atypical rearrangement in a patient with a negative MYC expression.
MYC/IGH; FISH; CLL; Microarray
Gene rearrangement analysis using Southern-blot hybridization technique is a standard method for evaluating clonal receptor gene rearrangement. Both clonality and lineage can be identified in lymphoid neoplasms by the demonstration of one or more rearranged antigen receptor genes of the immunoglobulin supergene family-immunoglobulin and T-cell receptor genes. To evaluate the diagnostic applicability of antigen receptor gene rearrangements in the diagnosis of malignant lymphomas and leukemias, the authors performed a gene rearrangement analysis of 54 cases by southern blot hybridization technique. One or two clonally rearranged bands were detected in the malignant lymphomas and in the lymphoblastic leukemias with a false-negative rate of 13.8%. No clonal, rearranged band was detected in benign reactive hyperplasias, carcinomas or non-lymphocytic leukemias. Rearrangement analysis could resolve the lineage, clonality and stage of differentiation of malignant lymphoid neoplasms.
c-myc is the cellular gene homologous to the transforming sequence of MC29, an acute avian retrovirus. The human c-myc gene was cloned and used to study the structure and expression of c-myc in a variety of human hematopoietic malignancies. In a careful study of 106 patients, c-myc RNA was found to be expressed at elevated levels in tumor cells of 17 leukemia patients and five lymphoma patients. The c-myc gene was found to be rearranged in two lymphomas, an African Burkitt's lymphoma and a non-Hodgkins lymphoma in leukemic phase. The Burkitt's rearrangement involved the insertion of new DNA sequences upstream from the c-myc 5' coding region, presumably replacing the normal c-myc transcriptional promoter. None of the other 104 patients, including 20 with elevated myc expression, exhibited any evidence of a genetic rearrangement involving the c-myc gene. Our results show that there is a subset of hematopoietic malignancies characterized by elevated expression of c-myc. This elevated expression in most cases is not due to obvious genetic changes (rearrangement, amplification) at the c-myc locus nor to chromosomal translocations in the vicinity of this gene.
Acute lymphoblastic leukemia is predominantly found in children. It is a neoplasm of precursor cells or lymphoblasts committed to either a B- or T-cell lineage. The immature cells in B-acute lymphoblastic leukemia/lymphoma can be small or medium sized with scant or moderate cytoplasm and typically express B-cell markers such as CD19, cytoplasmic CD79a, and TdT without surface light chains. These markers, along with cytogenetic studies, are vital to the diagnosis, classification, and treatment of these neoplasms. We present an unusual case of a precursor B-cell ALL, in an 82-year-old woman, who presented with pancytopenia and widespread lymphadenopathy. The cells show L3 morphology (Burkitt-like lymphoma) with coexpression of TdT and surface light chains in addition to an MYC gene translocation and Philadelphia chromosome.
Rearrangements of oncogenes c-myc and c-abl were detected by non-radioactive hybridisation in a case of Burkitt's lymphoma/leukaemia. The surface phenotype of Burkitt's cells were positive for CD19, CD20, HLA-DR, CD14, CD33 and surface immunoglobulin markers. Although cytogenetic analysis was not performed, the c-myc and heavy immunoglobulin genes had the same 14.2 kilobase EcoRI molecular size fragment, suggesting a possible t(8;14) translocation which is a common marker of this malignancy. The c-abl oncogene was also rearranged in DNA digested BamHI and EcoRI. The physiopathological implications of the rearranged c-abl gene are unknown, this being the first case, as for as is known, of Burkitt's lymphoma/leukaemia with a rearranged c-abl gene.
A highly malignant human T-cell receptor (TCR) gamma/delta+ T-cell leukemia was shown to have a productive rearrangement of the TCR delta locus on one chromosome 14 and a novel t(8;14)(q24;q11) rearrangement involving the J delta 1 gene segment on the other chromosome 14. Chromosome walking coupled with pulsed-field gel electrophoretic (PFGE) analysis determined that the TCR J delta 1 gene fragment of the involved chromosome was relocated approximately 280 kb downstream of the c-myc proto-oncogene locus found on chromosome band 8q24. This rearrangement was reminiscent of the Burkitt's lymphoma variants that translocate to a region identified as the pvt-1 locus. Sequence comparison of the breakpoint junctions of interchromosomal rearrangements in T-cell leukemias involving the TCR delta-chain locus revealed novel signal-like sequence motifs, GCAGA(A/T)C and CCCA(C/G)GAC. These sequences were found on chromosome 8 at the 5' flanking site of the breakpoint junction of chromosome 8 in the TCR gamma/delta leukemic cells reported here and also on chromosome 1 in T-cell acute lymphocytic leukemia patients carrying the t(1;14)(p32;q11) rearrangement. These results suggest that (i) during early stages of gamma delta T-cell ontogeny, the region 280 kb 3' of the c-myc proto-oncogene on chromosome 8 is fragile and accessible to the lymphoid recombination machinery and (ii) rearrangements to both 8q24 and 1p32 may be governed by novel sequence motifs and be subject to common enzymatic mechanisms.
The 8p11 myeloproliferative syndrome (EMS), also called stem cell leukemia/lymphoma (SCLL), is a relatively rare condition characterized in its typical form by the occurrence, either simultaneously or sequentially, of a bcr/abl-negative myeloproliferative disorder and a lymphoma, usually a precursor T lymphoblastic lymphoma. The disease most often terminates in acute myeloid leukemia which is resistant to conventional chemotherapy. The defining cytogenetic abnormality, a translocation at the 8p11 locus, always involves the fibroblast growth factor 1 (FGFR1) gene. To date, eight partner genes have been identified in association with FGFR1 rearrangements. The most frequent FGFR1 translocation partner is the zinc finger gene ZNF198 located at 13q11. The t(8;13)(p11;q11) disrupts intron 8 of the FGFR1 gene and fuses proline-rich and zinc finger domains of the ZNF198 gene with the cytoplasmic tyrosine kinase domain of FGFR1. Oligomerization of the fusion protein occurs, with subsequent activation of downstream signal transduction pathways, culminating in neoplastic cell transformation. This review describes the historical development of the EMS/SCLL and outlines its cytogenetic abnormalities and molecular mechanisms with an illustrative case.
8p11 myeloproliferative syndrome; stem cell leukemia/lymphoma; FGFR1
Plasmablastic lymphoma (PBL) is a rare acquired immunodeficiency syndrome-associated non-Hodgkin’s lymphoma (AIDS-NHL), with predilection for the mucosa of oral cavity. It usually has a plasmablastic morphology, expressing plasma cell-associated antigens with weak or absent expression of B-cell-associated markers. To further define the immunophenotypic and molecular genetics of these tumors, we investigated two cases of plasmablastic lymphomas of the head and neck for c-myc gene rearrangement and immunoglobulin heavy chain (IgVH) hypermutation status. For the first time we report a case of AIDS-related PBL that, by fluorescence in situ hybridization (FISH), shows a c-myc gene rearrangement. Although current literature suggests that most cases of c-myc gene rearranged AIDS-NHL are Burkitt’s lymphoma, our case has an immunophenotype characteristic for PBL. In this case, IgVH hypermutation analysis showed a somatic hypermutation, indicative of germinal center transit. The concurrent B-cell immunophenotype of BCL-6−/CD138+/MUM-1+ also suggests a post-germinal center B-cell origin of this lymphoma. The immunophenotype of our second case (BCL-6−/CD138+/MUM-1+) also suggests a post-germinal center B-cell origin. However, IgVH hypermutation analysis was not possible in this case.
Plasmablastic lymphoma; Acquired immunodeficiency syndrome-associated non-Hodgkin’s lymphoma; c-myc gene rearrangement; Immunoglobulin variable heavy chain hypermutation status
Myc is a well known driver of lymphomagenesis, and Myc-activating chromosomal translocation is the recognized hallmark of Burkitt lymphoma, an aggressive form of non-Hodgkin's lymphoma. We developed a model that mimics this translocation event by inserting a mouse Myc cDNA gene into the immunoglobulin heavy chain locus, just upstream of the intronic Eμ enhancer. These mice, designated iMycEμ, readily develop B-cell lymphoma. To study the mechanism of Myc-induced lymphoma, we analyzed signaling pathways in lymphoblastic B-cell lymphomas (LBLs) from iMycEμ mice, and an LBL-derived cell line, iMycEμ-1.
Nuclear factor-κB (NF-κB) and signal transducer and activator of transcription 3 (STAT3) were constitutively activated in iMycEμ mice, not only in LBLs but also in the splenic B-lymphocytes of young animals months before tumors developed. Moreover, inhibition of either transcription factor in iMycEμ-1 cells suppressed growth and caused apoptosis, and the abrogation of NF-κB activity reduced DNA binding by both STAT3 and Myc, as well as Myc expression. Inhibition of STAT3 signaling eliminated the activity of both NF-κB and Myc, and resulted in a corresponding decrease in the level of Myc. Thus, in iMycEμ-1 cells NF-κB and STAT3 are co-dependent and can both regulate Myc. Consistent with this, NF-κB and phosphorylated STAT3 were physically associated with one another. In addition, LBLs and iMycEμ-1 cells also showed constitutive AKT phosphorylation. Blocking AKT activation by inhibiting PI3K reduced iMycEμ-1 cell proliferation and caused apoptosis, via downregulation of NF-κB and STAT3 activity and a reduction of Myc levels. Co-treatment with NF-κB, STAT3 or/and PI3K inhibitors led to additive inhibition of iMycEμ-1 cell proliferation, suggesting that these signaling pathways converge.
Our findings support the notion that constitutive activation of NF-κB and STAT3 depends on upstream signaling through PI3K, and that this activation is important for cell survival and proliferation, as well as for maintaining the level of Myc. Together, these data implicate crosstalk among NF-κB, STAT3 and PI3K in the development of iMycEμ B-cell lymphomas.
Hypereosinophilia, either clonal or reactive, has been described in association with multiple hematological malignancies. We describe a case of a patient presenting with hypereosinophilia that evolved into T-cell lymphoblastic lymphoma. Complete remission was achieved with chemotherapy; however, hypereosinophilia recurred 5 months later in association with myeloblastic bone marrow infiltration and without evidence of lymphoblastic lymphoma relapse. Cytogenetic analysis of the bone marrow showed a complex translocation involving chromosomes 7, 12, and 16. A rearrangement of ETV6 gene (12p13) was demonstrated by FISH studies, thus confirming the clonality of this population. The association of lymphoblastic lymphoma, eosinophilia, and myeloid hyperplasia has been described in disorders with FGFR1 rearrangements. We hypothesize that other clonal eosinophilic disorders lacking this rearrangement could behave in a similar fashion through different pathogenic mechanisms.
The most common recurrent cytogenetic abnormalities in T-lymphoblastic leukemia (T-acute lymphoblastic leukemia [T-ALL]) involve T-cell receptor (TCR) loci and a variety of partner genes, including HOX11, HOX11L2, MYC, and TAL1. In this report, we present a rare case involving simultaneous translocation of the TCR α/δ loci with different partner loci (Xq22 and 12p13); this resulted in a poor prognosis. Chromosomal analysis showed 46,Y,t(X;14)(q22;q11.2),t(12;14)(p13;q11.2) and FISH analysis by using a T-cell receptor alpha delta DNA probe, Split Signal (DakoCytomation, Denmark), showed translocations at the same TCR α/δ locus on both chromosomes. FISH with 2 bacterial artificial chromosome clones showed break apart signal, which suggests involvement of the IRS4 gene. To our knowledge, this is the first report of T-ALL in which both TCR α/δ loci were translocated with different partner loci, and 1 of the partner loci, Xq22, was a rare translocation partner locus that included IRS4 gene.
T-lymphoblastic leukemia; Simultaneous translocation of TCR loci; IRS4 gene
Follicular lymphoma (FL) is a common form of non-Hodgkin lymphoma with an ability to transform into a more aggressive disease, albeit infrequently to B-lymphoblastic leukemia/lymphoma. While t(14;18)(q32;q21) has been associated with approximately 90% cases of FL, that alteration alone is insufficient to cause FL and associated mutations are still being elucidated. The transformation of FL to B-lymphoblastic leukemia generally includes the dysregulation of MYC gene expression, typically through IGH rearrangement. Such cases of “double-hit” leukemia/lymphoma with both BCL2 and MYC translocations warrant further study as they are often not identified early, are associated with a poor prognosis, and are incompletely understood in molecular terms. Here we describe a patient with a diagnosis of FL that transformed to B-lymphoblastic leukemia. Detailed cytogenetic characterization of the transformed specimen using karyotype, fluorescence in situ hybridization, microarray and gene rearrangement analyses revealed a complex karyotype comprised principally of whole chromosome or whole arm copy number gains or losses. Smaller, single-gene copy number alterations identified by microarray were limited in number, but included amplification of a truncated EP300 gene and alterations in NEIL1 and GPHN. Analyses defined the presence of an IGH/BCL2 fusion due to a translocation as well as a MYC/IGH fusion due to an insertion, with both rearrangements involving the same IGH allele. The data illustrate the value in characterizing double-hit lymphoma cases with both traditional and novel technologies in the detailed cytogenetic workup.
Follicular lymphoma; Transformation; B-Lymphoblastic leukemia; Translocation; Microarray
We report a case of untreated non-Hodgkin's lymphoma with histologic progression over 1 yr from a low-grade, small cleaved follicular center cell lymphoma to a high-grade, small noncleaved follicular center cell lymphoma. Both lymphomas had identical immunoglobulin (Ig) heavy-chain joining gene (JH), kappa light-chain joining gene, and bcl-2 gene rearrangements, indicating the clonal identity of the two tumors. The Ig heavy chain locus on one chromosome 14 was involved in an initial t(14; 18) translocation as shown by comigrating JH and bcl-2 rearrangements. However, the oncogene c-myc was in the germline configuration in the initial lymphoma but had one allele rearranged near the 3' end of exon I in the high-grade tumor; DNA sequence analysis was consistent with a chromosomal breakpoint at that site. The presence of the c-myc rearrangement in the high-grade tumor suggest a role for c-myc in the clonal evolution of the low-grade tumor into a more aggressive lymphoma. The coexistence of both bcl-2 gene and c-myc oncogene rearrangements in the same tumor is unusual, with only a few cases reported. Furthermore, this case is unique in the direct demonstration of the histologic and clinical progression of a human lymphoma associated with the sequential rearrangement of the bcl-2 gene and the c-myc oncogene.
One of the best analyzed tumor-specific cytogenetic abnormalities is the t(8;14) chromosomal translocation observed in cases of Burkitt's and undifferentiated lymphomas (ULs), and acute lymphoblastic leukemias (ALLs). Here we analyze the cloned (8;14) chromosomal breakpoint of the UL cell line EW 36. We show that the region of chromosome 8 involved in the translocation is situated near a site previously demonstrated to harbor a cluster of endemic Burkitt's lymphoma breakpoints, approximately 50 kb 5' of MYC. In those cases, we demonstrated that malfunction of the V-D-J recombinase generated the translocations. However, in this case the isotype switch mechanism of translocation is implicated: at the breakpoint, S mu/S gamma and C gamma sequences are found on chromosome 14. Thus, the features of the EW 36 t(8;14) breakpoint are consonant with our model for B-cell lymphomagenesis which relates the precursor cell that gives rise to malignancy, the mechanism of translocation, and the phenotype of the tumor.
An in vitro culture of FLEB14 cells, an Epstein-Barr virus-transformed B cell precursor containing the germ line immunoglobulin genes, gave rise to a uniclonally expanded variant, FLEB14 delta 3, which was rearranged at the immunoglobulin heavy-chain gene locus. Cytogenetic analysis showed that FLEB14 delta 3 had a novel reciprocal translocation, t(6;14)(q15;q32). Molecular cloning of the rearranged DNA fragments and determination of their nucleotide sequence revealed that the recombination event was reciprocal, imprecise, and nonhomologous and took place in the S mu region, like those found in Burkitt's lymphoma cells. We propose a molecular model to explain this genetic event which may be relevant to class switch recombination. The translocated sequence of chromosome 6 did not contain any known oncogenes, although the sequence is conserved among mammals. FLEB14 delta 3 did not show tumorigenicity.
Acute lymphoblastic leukemia (ALL) is generally regarded as a clonal disease in which a single abnormal progenitor cell gives rise to neoplastic progeny. Five of 463 cases of childhood ALL with adequately banded leukemic cells were found to have two cytogenetically independent cell populations. In addition, two of the four cases tested had more than two rearranged immunoglobulin genes and (or) T cell receptor genes. To investigate the clonality of these unusual leukemias, we examined the neoplastic cells for X-linked markers extrinsic to the disease. Leukemic cells from each of the three patients heterozygous for an X-linked, restriction fragment length polymorphism showed a single active parental allele, suggesting that both apparently independent cell populations developed from a common progenitor. These cases provide evidence that leukemogenesis involves a multistep process of mutation and suggest that karyotypic abnormalities may be a late event of malignant transformation.
Reciprocal translocations involving the immunoglobulin loci and the cellular oncogene MYC are hallmark mutations of the human postgerminal center B cell neoplasm, Burkitt’s lymphoma. They are occasionally found in other B cell lymphomas, as well. Translocations involving the heavy chain locus (IGH) place the MYC gene either in cis with both the intronic enhancer Eµ and the IGH 3′ regulatory region (3′RR) or in cis with only the 3′RR. The result is deregulated MYC expression. Recent studies have led to some controversy as to when, during B lymphocyte development, IGH/MYC chromosome translocations take place. A related issue, relevant not only to lymphoma development but also to normal controls on IGH gene expression, is the stage, during B lymphocyte development, at which the 3′RR is capable of activating MYC expression. We have developed mice transgenic for a human MYC (hMYC) gene under control of the four core enhancers from the mouse Igh 3′RR. Unlike other transgenic mouse models where premature and inappropriate MYC expression disrupts normal B cell development, the hMYC transgene in these studies carries a mutation that prohibits MYC protein synthesis. As a result, hMYC expression can be analyzed in all of the normal B cell compartments. Our data show that hMYC is expressed almost exclusively in B-lineage cells and is induced to high levels as soon as bone marrow cells reach the immature B cell stage.
The coexistence of CCND1/IGH and MYC rearrangements in mantle cell lymphoma (MCL) is a rare finding associated with a very poor prognosis. In this study, a patient with blastoid variant (MCL) is reported. The disease was clinically aggressive and refractory to chemotherapy, and the patient only survived for 1 month following diagnosis. Conventional cytogenetic study, FISH, and multicolor FISH (mFISH) demonstrated the involvement of the BCL1/CCND1 locus in a complex translocation, t(3;11)(q25;p15)t(11;14)(q13;q32). In addition, subclonal abnormalities in the 8q24 region, manifested as a t(8;14)(q24;q32)/MYC rearrangement, were identified. To the best of our knowledge, this is the first MCL case in Korea bearing these complex genomic aberrations.
Mantle cell lymphoma; CCND1; MYC
Mature B-cell lymphomas with both BCL2 and MYC translocations are known as “double hit” lymphomas. These lymphomas are aggressive and show high proliferation rate due to the growth advantages provided by MYC and BCL2 translocation and overexpression. Mantle cell lymphoma (MCL) is a neoplasm of mature B-lymphocytes with characteristic t(11;14) and subsequent Cyclin D1 overexpression. Secondary cytogenetic changes are frequent in MCL, but MYC translocation has only been rarely reported. In this study, we report four cases of MCL with MYC translocation or MYC gene amplification detected by conventional cytogenetics, fluorescence in situ hybridization and whole genome single nucleotide polymorphism (SNP) array, and determined the clinicopathologic features. Our study provides further evidence supporting the concept of “double hit” MCL with co-involvement of MYC gene rearrangement and/or amplification and CCND1 gene rearrangement.
Mantle cell lymphoma; double hit lymphoma; MYC; 8q24; translocation; amplification
Approximately 5–10% of diffuse large B-cell lymphomas (DLBCL) harbor a 8q24/MYC rearrangement (MYC
+). We determined the prognostic significance of MYC rearrangement in patients with relapsed/refractory DLBCL prospectively treated by R-ICE or R-DHAP followed by high-dose therapy and autologous stem cell transplantation. Twenty-eight (17%) of the 161 patients analyzed presented a MYC
+ rearrangement, targeted as either simple hit (25%) or complex hits (n=75%) including MYC/BCL2, MYC/BCL6, and MYC/BCL2/BCL6. Results were statistically highly concordant in matched primary and relapsed biopsies (n=45). Compared to the MYC
− DLBCL patients, the MYC
+ DLBCL patients presented with a more elevated lactico-deshydrogenase level (p=.0006) and a more advanced age-adjusted international pronostic index (p=.0039). The 4-year PFS and OS were significantly lower in the MYC
+ DLBCL patients than those in the MYC
− DLBCL patients, with rates of 18% vs. 42% (p=.0322), and of 29% vs. 62% (p=.0113), respectively. Type of treatment, R-DHAP or R-ICE had no impact on survivals, with 4-year PFS rates of 17% vs. 19% and 4-year OS rates of 26% vs. 31%. In conclusion, MYC rearrangement is an early event in DLBCL. MYC
+ DLBCL patients have a significant inferior prognosis than MYC
− DLBCL patients. Their outcome was not influenced by the proposed salvage therapy.
Adult; Aged; Antibodies, Monoclonal, Murine-Derived; administration & dosage; adverse effects; Antineoplastic Combined Chemotherapy Protocols; administration & dosage; adverse effects; Carmustine; administration & dosage; adverse effects; Chemotherapy, Adjuvant; Cisplatin; administration & dosage; adverse effects; Combined Modality Therapy; Cytarabine; administration & dosage; adverse effects; Dexamethasone; administration & dosage; adverse effects; Etoposide; administration & dosage; adverse effects; Female; Genes, myc; physiology; Hematopoietic Stem Cell Transplantation; methods; Humans; Ifosfamide; administration & dosage; adverse effects; Immunotherapy; Lymphoma, Large B-Cell, Diffuse; drug therapy; genetics; mortality; therapy; Male; Melphalan; administration & dosage; adverse effects; Middle Aged; Podophyllotoxin; administration & dosage; adverse effects; Salvage Therapy; Transplantation, Autologous; Treatment Failure; Young Adult
Transgenic mice that contain constructs of the L-myc gene under the transcriptional control of the immunoglobulin heavy chain enhancer (E mu) develop thymic hyperplasia and are predisposed to T cell lymphomas. Here we describe a second form of malignancy that occurs in aging E mu L-myc transgenic mice. The mean latency period for the development of this malignancy is longer compared with the E mu L-myc T cell lymphomas but the overall incidence is increased threefold. The histopathological morphology is that of a highly malignant mesenchymal neoplasm that closely resembles human fibrous histiocytoma. The tumor cells were classified as myelomonocytic on the basis of several lineage-specific markers and the lack of rearrangements of the immunoglobulin heavy chain and the T cell receptor beta loci. Cultured tumor cells produce macrophage colony-stimulating factor (M-CSF) protein and express the M- CSF receptor, suggesting the involvement of an autocrine loop in this malignancy. Similar to the E mu L-myc T cell lymphomas, these tumors show high-level transgene expression but no detectable levels of endogenous c-myc mRNA, directly implicating the deregulated expression of L-myc in the generation of this malignancy. E mu L-myc myelomonocytic tumors show consistent trisomy of chromosome 16, implicating this as a secondary event in the development of this tumor. In the light of recent findings that L-myc is expressed in human myeloid leukemias and in several human myeloid tumor cell lines, the results described here might implicate L-myc in the development of naturally occurring myeloid neoplasias.
Moloney murine leukemia virus-induced rat T-cell lymphomas harbor proviruses integrated near c-myc and near Mlvi-1/Mis-1/Pvt-1, another locus of common integration which maps 270 kilobases 3' of c-myc. In this report, we present the characterization of a new locus of common integration in Moloney murine leukemia virus-induced T-cell lymphomas (Mlvi-4) which maps 30 kilobases 3' of c-myc, between c-myc and Mlvi-1. The Mlvi-4 locus, whose chromosomal map location is conserved in rats, mice, and humans, is also the target of chromosomal rearrangements in a variety of animal and human tumors. Evidence presented elsewhere shows that provirus integration in Mlvi-4 enhances the expression of c-myc and Mlvi-1 by cis-acting mechanisms operating over long distances of genomic DNA. In this manuscript, we show that provirus integration in the Mlvi-4 locus activates, by promoter insertion, one additional gene which maps immediately 3' to the cluster of the Mlvi-4 proviruses and which is transcribed in the same orientation as c-myc, giving rise to 3- and 10-kilobase mRNA transcripts. The Mlvi-4 gene is also expressed in normal thymus and spleen at very low levels, giving rise to 3- and 5.5-kilobase messages. Although Mlvi-4 is expressed in normal thymus, it is not expressed in Moloney murine leukemia virus-induced T-cell lymphomas corresponding to several stages of T-cell differentiation, but lacking a provirus in this locus. This suggests that Mlvi-4 may be expressed only in a subpopulation of T cells. We conclude that provirus insertion in Mlvi-4 activates c-myc and two additional genes, Mlvi-1 and Mlvi-4, whose expression is restricted to, and may be developmentally regulated in, T cells. Since Mlvi-4 is the target of genetic changes in a great variety of human and animal neoplasms, these results are critical for our understanding of oncogenesis.
B-cell lymphomas with concurrent IGH-BCL2 and MYC rearrangements, also known as “double-hit” lymphomas (DHL), are rare neoplasms characterized by highly aggressive clinical behavior, complex karyotypes, and a spectrum of pathological features overlapping with Burkitt lymphoma (BL), diffuse large B-cell lymphoma (DLBCL) and B-lymphoblastic lymphoma/leukemia (B-LBL). The clinical and pathological spectrum of this rare entity, including comparison to other high-grade B-cell neoplasms, has not been well defined. We conducted a retrospective analysis of clinical and pathologic features of 20 cases of DHL seen at our institution during a 5-year period. In addition, we performed case-control comparisons of DHL with BL and International Prognostic Index (IPI)-matched DLBCL. The 11 men and 9 women had a median age of 63.5 years (range 32-91). Six patients had a history of grade 1-2 follicular lymphoma (FL); review of the prior biopsy specimens in 2 of 5 cases revealed blastoid morphology. Eighteen patients had Ann Arbor stage 3 or 4 disease and all had elevated serum lactate dehydrogenase (LDH) levels at presentation. Extranodal disease was present in 17/20 (85%), bone marrow involvement in 10/17 (59%) and central nervous system (CNS) disease in 5/11 (45%). Nineteen patients were treated with combination chemotherapy, of whom 18 received rituximab and 14 received CNS-directed therapy. Fourteen patients (70%) died within 8 months of diagnosis. Median overall survival in the DHL group (4.5 months) was inferior to both BL (p=0.002) and IPI-matched DLBCL (p=0.04) control patients. Twelve DHL cases (60%) were classified as B-cell lymphoma, unclassifiable, with features intermediate between DLBCL and BL, 7 cases (35%) as DLBCL, not otherwise specified, and 1 case as B-LBL. Distinguishing features from BL included expression of Bcl2 (p<0.0001), Mum1/IRF4 (p=0.006), Ki-67 <95% (p<0.0001), and absence of EBV-EBER (p=0.006). DHL commonly contained the t(8;22) rather than the t(8;14) seen in most BL controls (p=0.001), and exhibited a higher number of chromosomal aberrations (p=0.0009). DHL is a high-grade B-cell neoplasm with a poor prognosis, resistance to multi-agent chemotherapy, and clinical and pathological features distinct from other high-grade B-cell neoplasms. Familiarity with the morphologic and immunophenotypic spectrum of DHL is important in directing testing to detect concurrent IGH-BCL2 and MYC rearrangements when a karyotype is unavailable. The aggressive clinical behavior and combination of genetic abnormalities seen in these cases may warrant categorization as a separate entity in future classifications and call for novel therapeutic approaches.
MYC; BCL2; diffuse large B-cell lymphoma; Burkitt lymphoma; cytogenetics; high-grade B-cell lymphoma
We have studied recombinatorial events of the T cell receptor delta and gamma chain genes in hematopoietic malignancies and related these to normal stages of lymphoid differentiation. T cell receptor delta gene recombinatorial events were found in 91% of acute T cell lymphoblastic leukemia, 68% of non-T, non-B lymphoid precursor acute lymphoblastic leukemia (ALL) and 80% of mixed lineage acute leukemias. Mature B-lineage leukemias and acute nonlymphocytic leukemias retained the T-cell receptor delta gene in the germline configuration. The incidence of T cell receptor gamma and delta was particularly high in CD10+CD19+ non-T, non-B lymphoid precursor ALL. In lymphoid precursor ALL, T cell receptor delta was frequently rearranged while T cell receptor gamma was in the germline configuration. This suggests that TCR delta rearrangements may precede TCR gamma rearrangements in lymphoid ontogeny. In T-ALL, only concordant T cell receptor delta and gamma rearrangements were observed. Several distinct rearrangements were defined using a panel of restriction enzymes. Most of the rearrangements observed in T-ALL represented joining events of J delta 1 to upstream regions. In contrast, the majority of rearrangements in lymphoid precursor ALL most likely represented D-D or V-D rearrangements, which have been found to be early recombinatorial events of the TCR delta locus. We next analyzed TCR delta rearrangements in five CD3+TCR gamma/delta+ ALL and cell lines. One T-ALL, which demonstrated a different staining pattern with monoclonal antibodies against the products of the TCR gamma/delta genes than the PEER cell line, rearranges J delta 1 to a currently unidentified variable region.
The Burkitt lymphoma cell line KK124, which contains a reciprocal t(8;22) translocation, was shown to have rearranged in a region 3' to the c-myc proto-oncogene on chromosome 8 and 5' to the lambda constant region on chromosome 22. The breakpoint was cloned and sequenced, revealing that c-myc and a portion of its 3' region abutted a complete lambda variable gene that had undergone V-J recombination. Since this cell line expresses kappa light chain, this lambda rearrangement violates the previously proposed hierarchy of immunoglobulin gene rearrangement. A novel duplication of normal chromosome 8 sequences was also found at the breakpoint. The first exon of c-myc and its flanking sequence from the translocated allele was sequenced and compared with a normal counterpart. Extensive mutation was found within the first exon in contrast to its 3' and 5' flanking regions. S1 nuclease analysis revealed that it was the translocated c-myc being expressed and that there was a promoter shift from P2 to P1. The detailed structural analysis of this cell line provides clues concerning mechanisms of chromosomal translocation and c-myc deregulation in Burkitt lymphomas.