A novel variant translocation t(2;13) (p23;q34) in Ki-1 large cell anaplastic lymphoma

Analysis of gene expression profile of TPM3-ALK positive anaplastic large cell lymphoma reveals overlapping and unique patterns with that of NPM-ALK positive anaplastic large cell lymphoma

Anaplastic large cell lymphoma (ALCL) comprises a group of non-Hodgkin lymphomas characterized by the expression of the CD30/Ki-1 antigen. A subset of ALCL is characterized by chromosomal translocations involving the anaplastic lymphoma kinase (ALK) gene on chromosome 2. While the most common translocation is the t(2;5)(p23;q35) involving the nucleophosmin (NPM) gene on chromosome 5, up to 12 other translocations partners of the ALK gene have been identified. One of these is the t(1;2)(q25;p23) which results in the formation of the chimeric protein TPM3-ALK. While several of the signaling pathways induced by NPM-ALK have been elucidated, those involved in ALCLs harboring TPM3-ALK are largely unknown. In order to investigate the expression profiles of ALCLs carrying the NPM-ALK and TPM3-ALK fusions, we carried out cDNA microarray analysis of two ALCL tissue samples, one expressing the NPM-ALK fusion protein and the other the TPM3-ALK fusion protein. RNA was extracted from snap-frozen tissues, labeled with fluorescent dyes and analyzed using cDNAs microarray containing approximately 9,200 genes and expressed sequence tags (ESTs). Quantitative fluorescence RT-PCR was performed to validate the cDNA microarray data on nine selected gene targets. Our results show a significant overlap of genes deregulated in the NPM-ALK and TPM-ALK positive lymphomas. These deregulated genes are involved in diverse cellular functions, such as cell cycle regulation, apoptosis, proliferation, and adhesion. Interestingly, a subset of the genes was distinct in their expression pattern in the two types of lymphomas. More importantly, many genes that were not previously associated with ALK positive lymphomas were identified. Our results demonstrate the overlapping and unique transcriptional patterns associated with the NPM-ALK and TPM3-ALK fusions in ALCL.

Anaplastic lymphoma kinase proteins in growth control and cancer

The normal functions of full-length anaplastic lymphoma kinase (ALK) remain to be completely elucidated. Although considered to be important in neural development, recent studies in Drosophila also highlight a role for ALK in gut muscle differentiation. Indeed, the Drosophila model offers a future arena for the study of ALK, its ligands and signalling cascades. The discovery of activated fusion forms of the ALK tyrosine kinase in anaplastic large cell lymphoma (ALCL) has dramatically improved our understanding of the pathogenesis of these lymphomas and enhanced the pathological diagnosis of this subtype of non-Hodgkin's lymphoma (NHL). Likewise, the realisation that a high percentage of inflammatory myofibroblastic tumours express activated-ALK fusion proteins has clarified the causation of these mesenchymal neoplasms and provided for their easier discrimination from other mesenchymal-derived inflammatory myofibroblastic tumour (IMT) mimics. Recent reports of ALK expression in a range of carcinoma-derived cell lines together with its apparent role as a receptor for PTN and MK, both of which have been implicated in tumourigenesis, raise the possibility that ALK-mediated signalling could play a role in the development and/or progression of a number of common solid tumours. The therapeutic targeting of ALK may prove to have efficacy in the treatment of many of these neoplasms.

Molecular characterization of a new ALK translocation involving moesin (MSN-ALK) in anaplastic large cell lymphoma

The majority of anaplastic large cell lymphomas (ALCL) are associated with chromosomal abnormalities affecting the anaplastic lymphoma kinase (ALK) gene which result in the expression of hybrid ALK fusion proteins in the tumor cells. In most of these tumors, the hybrid gene comprises the 5' region of nucleophosmin (NPM) fused in frame to the 3' portion of ALK, resulting in the expression of the chimeric oncogenic tyrosine kinase NPM-ALK. However, other variant rearrangements have been described in which ALK fuses to a partner other than NPM. Here we have identified the moesin (MSN) gene at Xq11-12 as a new partner of ALK in a case of ALCL which exhibited a distinctive membrane-restricted pattern of ALK labeling. The hybrid MSN-ALK protein had a molecular weight of 125 kd and contained an active tyrosine kinase domain. The unique membrane staining pattern of ALK is presumed to reflect association of moesin with cell membrane proteins. In contrast to other translocations involving the ALK gene, the ALK breakpoint in this case occurred within the exonic sequence coding for the juxtamembrane portion of ALK. Identification of the genomic breakpoint confirmed the in-frame fusion of the whole MSN intron 10 to a 17 bp shorter juxtamembrane exon of ALK. The breakpoint in der(2) chromosome showed a deletion, including 30 bp of ALK and 36 bp of MSN genes. These findings indicate that MSN may act as an alternative fusion partner for activation of ALK in ALCL and provide further evidence that oncogenic activation of ALK may occur at different intracellular locations.

Pathobiology of NPM-ALK and variant fusion genes in anaplastic large cell lymphoma and other lymphomas

Despite its clinical and histological heterogeneity, anaplastic large cell lymphoma (ALCL) is now a well-recognized clinicopathological entity accounting for 2% of all adult non-Hodgkin's lymphomas (NHL) and about 13% of pediatric NHL. Immunophenotypically, ALCL are of T cell (predominantly) or Null cell type; by definition, cases expressing B cell antigens are officially not included in this entity. The translocation (2;5)(p23;q35) is a recurring abnormality in ALCL; 46% of the ALCL patients bear this signature translocation. This translocation creates a fusion gene composed of nucleophosmin (NPM) and a novel receptor tyrosine kinase gene, named anaplastic lymphoma kinase (ALK). The NPM-ALK chimeric gene encodes a constitutively activated tyrosine kinase that has been shown to be a potent oncogene. The exact pathogenetic mechanisms leading to lymphomagenesis remain elusive; however, the synopsis of evidence obtained to date provides an outline of likely scenarios. Several t(2;5) variants have been described; in some instances, the breakpoints have been cloned and the genes forming a new fusion gene with ALK have been identified: ATIC-ALK, TFG-ALK and TPM3-ALK. Cloning the translocation breakpoint and identifying the ALK and NPM genes provided tools for screening material from patients with ALCL using various approaches at the chromosome, DNA, RNA, or protein level: positive signals in the reverse transcriptase-polymerase chain reaction (RT-PCR) and the immunostaining with anti-ALK monoclonal antibodies (McAb) serve as the most convenient tests for detection of the t(2;5) NPM-ALK since the fusion gene and ALK protein expression do not occur in normal or reactive lymphoid tissue. The wide range of NPM-ALK positivity reported in different series appears to be dependent on the inclusion and selection criteria of the ALCL cases studied. Overall, however, 43% of ALCL cases were NPM-ALK+ (83% of pediatric ALCL vs 31% of adult ALCL). Occasional non-ALCL B cell lymphomas (4%) with diffuse large cell and immunoblastic histology and Hodgkin's disease cases (3%) were NPM-ALK-, but these data are questionable. The aggregate results indicate that, in contrast to primary nodal (systemic) ALCL, the t(2;5) may be present in only 10-20% of primary cutaneous ALCL and rarely, if at all, in lymphomatoid papulosis, a potential precursor lesion; however, these 10-20% positive cases were not confirmed by anti-ALK McAb immunostaining and may represent an overestimate. Positivity for NPM-ALK is associated to various degrees with the following parameters: 44% and 45% of ALCL cases with T cell and Null cell immunophenotype, respectively, are positive, whereas only 8% of cases with a B cell immunoprofile are positive; the mean age of positive patients is significantly younger than that of negative patients; positive cases carry a better overall prognosis (but not in all studies). Recently, the homogenous category of ALK lymphoma ('ALKoma') has emerged as a distinct pathological entity within the heterogenous group of ALCL. The fact that patients with ALK lymphomas experience significantly better overall survival than ALK- ALCL demonstrates further that analysis of ALK expression has important prognostic implications. The term ALK lymphoma signifies a switch in the use of the diagnostic criteria: cases are selected on the basis of a genetic abnormality (the ALK rearrangement), instead of the review of morphological or immunophenotypical features which are clearly more prone to disagreement and controversy. Since its initial description in 1985 ALCL has become one of the best characterized lymphoma entities.

Inv(2)(p23q35) in anaplastic large-cell lymphoma induces constitutive anaplastic lymphoma kinase (ALK) tyrosine kinase activation by fusion to ATIC, an enzyme involved in purine nucleotide biosynthesis

The non-Hodgkin lymphoma (NHL) subtype anaplastic large-cell lymphoma (ALCL) is frequently associated with a t(2;5)(p23;q35) that results in the fusion of the ubiquitously expressed nucleophosmin (NPM) gene at 5q35 to the anaplastic lymphoma kinase (ALK) gene at 2p23, which is not normally expressed in hematopoietic tissues. Approximately 20% of ALCLs that expressALK do not contain the t(2;5), suggesting that other genetic abnormalities can result in aberrant ALK expression. Here we report the molecular characterization of an alternative genetic means of ALK activation, the inv(2)(p23q35). This recurrent abnormality produces a fusion of the amino-terminus of 5-aminoimidazole-4-carboxamide ribonucleotide formyltransferase/IMP cyclohydrolase (ATIC), a bifunctional homodimeric enzyme that catalyzes the penultimate and final steps of de novo purine nucleotide biosynthesis, with the intracellular portion of the ALK receptor tyrosine kinase. RT-PCR analysis of 5 ALCL tumors that contained the inv(2) revealed identical ATIC-ALK fusion cDNA junctions in all of the cases. Transient expression studies show that theATIC-ALK fusion transcript directs the synthesis of an approximately 87-kd chimeric protein that is localized to the cytoplasm, in contrast to NPM-ALK, which typically exhibits a cytoplasmic and nuclear subcellular distribution. ATIC-ALK was constitutively tyrosine phosphorylated and could convert the IL-3–dependent murine hematopoietic cell line BaF3 to cytokine-independent growth. Our studies demonstrate an alternative mechanism for ALK involvement in the genesis of NHL and suggest that ATIC-ALK activation results from ATIC-mediated homodimerization. In addition, expected decreases in ATIC enzymatic function in ATIC-ALK–containing lymphomas may render these tumors more sensitive to antifolate drugs such as methotrexate.

ATIC-ALK: A novel variant ALK gene fusion in anaplastic large cell lymphoma resulting from the recurrent cryptic chromosomal inversion, inv(2)(p23q35)

The subset of CD30-positive anaplastic large cell lymphomas (ALCL) with the NPM-ALK gene fusion arising from the t(2;5)(p23;q35) forms a distinct clinical and prognostic entity. Recently, various cytogenetic, molecular, and protein studies have provided evidence for the existence of several types of variant ALK fusions in up to 20% of ALK+ ALCL, of which only one, a TPM3-ALK fusion resulting from a t(1;2)(q25;p23), has so far been cloned. A cryptic inv(2)(p23q35) has been described as another recurrent cytogenetic alteration involving ALK and an unidentified fusion partner in some ALCL. In a screen for variant ALK gene fusions, we identified two ALCL that were negative for NPM-ALK by reverse transcriptase-polymerase chain reaction, but were positive for cytoplasmic ALK with both polyclonal and monoclonal antibodies to the ALK tyrosine kinase domain, consistent with ALK deregulation by an alteration other than the t(2;5) Case 1 was a T-lineage nodal and cutaneous ALCL in a 52-year-old woman, and Case 2 was a T-lineage nodal ALCL in a 12-year-old girl. FISH analysis confirmed ALK rearrangement in both cases. An inverse polymerase chain reaction approach was then used to identify the ALK translocation partner in Case 1. We found an in-frame fusion of ALK to ATIC, a gene previously mapped to 2q34-q35. We then confirmed by DNA polymerase chain reaction the localization of ATIC to yeast artificial chromosome (YAC) 914E7 previously reported to span the 2q35 break in the inv(2)(p23q35). FISH analysis in Case 1 confirmed rearrangement of YAC 914E7 and fusion to ALK. The ATIC-ALK fusion was confirmed in Case 1 and also identified in Case 2 by conventional reverse transcriptase-polymerase chain reaction using ATIC forward and ALK reverse primers. ATIC encodes an enzyme involved in purine biosynthesis which, like other fusion partners of ALK, is constitutively expressed and appears to contain a dimerization domain. ATIC-ALK fusion resulting from the inv(2)(p23q35) thus provides a third mechanism of ALK activation in ALK+ ALCL.

TRK-Fused Gene (TFG) Is a New Partner of ALK in Anaplastic Large Cell Lymphoma Producing Two Structurally DifferentTFG-ALK Translocations

Anaplastic large cell lymphoma (ALCL) is associated with the t(2;5)(p23;q35), which generates the NPM-ALK fusion gene encoding an 80-kD protein. Several studies have suggested that genes other than NPM may be fused to theALK gene. Here we have identified TRK-fused gene (TFG) as a new ALK partner in 2 ALCL, 1 of which exhibited a t(2;3)(p23;q21). In these cases, TFG was involved in 2 different fusion genes, TFG-ALKS andTFG-ALKL, coding respectively 85-kD and 97-kD chimeric proteins. The ALK breakpoint in these translocations was the same as in the classic t(2;5) translocation. These 2 proteins were both active in an in vitro tyrosine kinase assay showing that the new cloned cDNA sequences are translated into chimeric proteins with functional activity. These findings indicate thatTFG can provide an alternative to NPM as a fusion partner responsible for activation of the ALK and the pathogenesis of ALCL.

t(1;2)(q21;p23) and t(2;3)(p23;q21): Two Novel Variant Translocations of the t(2;5)(p23;q35) in Anaplastic Large Cell Lymphoma

Cytogenetic investigations in two cases of anaplastic large cell lymphoma (ALCL) showed novel variants of the classical (2;5)(p23;q35) translocation, namely a t(1;2)(q21;p23) and a t(2;3)(p23;q21). The tumor cells in both cases gave positive immunohistochemical labeling for ALK protein (with both monoclonal and polyclonal antibodies), demonstrating that these translocations induce aberrant expression of this kinase and suggesting that genes other than NPM can activate the ALK gene in ALCL. These two cases were shown by an in vitro kinase assay to express ALK kinases (104 kD and 97 kD, respectively), which differed in size from the classical NPM-ALK fusion product (80 kD). Moreover, ALK expression was confined to the cytoplasm of the tumor cells in each case, supporting the hypothesis that the observed nuclear localization of NPM-ALK in classical ALCL is not the site of oncogenic activity of the ALK kinase.

Biochemical detection of novel anaplastic lymphoma kinase proteins in tissue sections of anaplastic large cell lymphoma

The (2;5) translocation, found in many T-cell and null cell anaplastic large cell lymphomas (ALCLs), creates a hybrid gene encoding the 80-kd NPM-ALK protein. Typically neoplastic cells show labeling of both nucleus and cytoplasm for anaplastic lymphoma kinase (ALK) and for the N-terminus of nucleophosmin (NPM). However, 10-20% of cases exhibit cytoplasmic labeling only for ALK, indicating the probable presence of variants of the classical (2;5) translocation that do not involve the NPM gene. We report the detection (using Western blotting and an in vitro kinase assay) in seven such ALCL cases, of ALK proteins with molecular masses of 85 kd, 97 kd (one case exhibiting a (2;3)(p23;q21) translocation), 104 kd (one case carried a (1;2)(q21;p23) translocation), and 113 kd. Tyrosine kinase activity was detected in four of these proteins, but the N-terminal portion of NPM could not be detected. These results show how ALCL cases that express ALK proteins other than NPM-ALK can be detected by sensitive biochemical techniques using routine cryostat sections.

A New Fusion Gene TPM3-ALK in Anaplastic Large Cell Lymphoma Created by a (1;2)(q25;p23) Translocation

Anaplastic large cell lymphomas (ALCL) are frequently associated with the t(2;5)(p23;q35). This translocation fuses the nucleophosmin (NPM) gene at 5q35, which encodes a nucleolar protein involved in shuttling ribonucleoproteins from the cytoplasm to the nucleus, to the anaplastic lymphoma kinase (ALK) gene at 2p23, encoding a tyrosine kinase receptor. In this report, we describe a typical case of ALCL whose malignant cells exhibited a novel (1;2)(q25;p23) translocation. These cells expressed ALK protein, but, in contrast to t(2;5)-positive ALCL (which show cytoplasmic, nuclear, and nucleolar staining), labeling was restricted to the malignant cell cytoplasm. Using a polymerase chain reaction (PCR)-based technique to walk on chromosome 2 from the known ALK gene across the breakpoint, we showed that the gene involved at 1q25 is TPM3, encoding a nonmuscular tropomyosin. We subsequently identified, using reverse transcription-PCR analysis of cases showing similar ALK cytoplasm-restricted staining, fusion of the ALK andTPM3 genes in 2 other cases of ALCL. The TPM3 gene has been previously found in papillary thyroid carcinomas as a fusion partner with the TRK kinase gene. We showed that TPM3 is constitutively expressed in lymphoid cell lines, suggesting that, in these t(1;2)-bearing ALCL cases, the TPM3 gene contributes an active promoter for ALK expression. Activation of the ALK catalytic domain probably results from homodimerization of the hybrid protein TPM3-ALK, through the TPM3 protein-protein interaction domain. The present cases of ALCL associated with a novel t(1;2)(q25;p23) demonstrate that at least one fusion partner other than NPM can activate the intracytoplasmic domain of the ALK kinase.

A New Fusion Gene TPM3-ALK in Anaplastic Large Cell Lymphoma Created by a (1;2)(q25;p23) Translocation

Anaplastic large cell lymphomas (ALCL) are frequently associated with the t(2;5)(p23;q35). This translocation fuses the nucleophosmin (NPM) gene at 5q35, which encodes a nucleolar protein involved in shuttling ribonucleoproteins from the cytoplasm to the nucleus, to the anaplastic lymphoma kinase (ALK) gene at 2p23, encoding a tyrosine kinase receptor. In this report, we describe a typical case of ALCL whose malignant cells exhibited a novel (1;2)(q25;p23) translocation. These cells expressed ALK protein, but, in contrast to t(2;5)-positive ALCL (which show cytoplasmic, nuclear, and nucleolar staining), labeling was restricted to the malignant cell cytoplasm. Using a polymerase chain reaction (PCR)-based technique to walk on chromosome 2 from the known ALK gene across the breakpoint, we showed that the gene involved at 1q25 is TPM3, encoding a nonmuscular tropomyosin. We subsequently identified, using reverse transcription-PCR analysis of cases showing similar ALK cytoplasm-restricted staining, fusion of the ALK andTPM3 genes in 2 other cases of ALCL. The TPM3 gene has been previously found in papillary thyroid carcinomas as a fusion partner with the TRK kinase gene. We showed that TPM3 is constitutively expressed in lymphoid cell lines, suggesting that, in these t(1;2)-bearing ALCL cases, the TPM3 gene contributes an active promoter for ALK expression. Activation of the ALK catalytic domain probably results from homodimerization of the hybrid protein TPM3-ALK, through the TPM3 protein-protein interaction domain. The present cases of ALCL associated with a novel t(1;2)(q25;p23) demonstrate that at least one fusion partner other than NPM can activate the intracytoplasmic domain of the ALK kinase.

Detection of Normal and Chimeric Nucleophosmin in Human Cells

In anaplastic large-cell lymphoma (ALCL), the (2;5) chromosomal translocation creates a fusion gene encoding the 80-kD NPM-ALK hybrid protein. This report describes three new monoclonal antibodies, two of which recognize, by Western blotting, the N-terminal portion of NPM present in the NPM-ALK fusion protein and also in two other NPM fusion proteins (NPM-RAR and NPM-MLF1). The third antibody recognizes the C-terminal portion (deleted in NPM-ALK) and reacts only with wild-type NPM. The three antibodies immunostain wild-type NPM (in paraffin-embedded normal tissue samples) in cell nuclei and in the cytoplasm of mitotic cells. Cerebral neurones, exceptionally, show diffuse cytoplasmic labeling. In contrast to normal tissues, the two antibodies against the N-terminal portion of NPM labeled the cytoplasm of neoplastic cells, in four ALK-positive ALCL, reflecting their reactivity with NPM-ALK fusion protein, whereas the antibody to the C-terminal NPM epitope labeled only cell nuclei. Immunocytochemical labeling with these antibodies can therefore confirm that an ALK-positive lymphoma expresses NPM-ALK (rather than a variant ALK-fusion protein) and may also provide evidence for chromosomal anomalies involving the NPM gene other than the classical (2;5) translocation.

Detection of Normal and Chimeric Nucleophosmin in Human Cells

In anaplastic large-cell lymphoma (ALCL), the (2;5) chromosomal translocation creates a fusion gene encoding the 80-kD NPM-ALK hybrid protein. This report describes three new monoclonal antibodies, two of which recognize, by Western blotting, the N-terminal portion of NPM present in the NPM-ALK fusion protein and also in two other NPM fusion proteins (NPM-RAR and NPM-MLF1). The third antibody recognizes the C-terminal portion (deleted in NPM-ALK) and reacts only with wild-type NPM. The three antibodies immunostain wild-type NPM (in paraffin-embedded normal tissue samples) in cell nuclei and in the cytoplasm of mitotic cells. Cerebral neurones, exceptionally, show diffuse cytoplasmic labeling. In contrast to normal tissues, the two antibodies against the N-terminal portion of NPM labeled the cytoplasm of neoplastic cells, in four ALK-positive ALCL, reflecting their reactivity with NPM-ALK fusion protein, whereas the antibody to the C-terminal NPM epitope labeled only cell nuclei. Immunocytochemical labeling with these antibodies can therefore confirm that an ALK-positive lymphoma expresses NPM-ALK (rather than a variant ALK-fusion protein) and may also provide evidence for chromosomal anomalies involving the NPM gene other than the classical (2;5) translocation.

A new variant chromosomal translocation t(2;2)(p23;q23) in CD30+/Ki-1+ anaplastic large cell lymphoma

A case with a complex chromosome abnormality with a t(2;2)(p23;q23) in CD30+/Ki-1+ anaplastic large cell lymphoma (ALCL) is described. This chromosome aberration has not been reported previously in neoplastic diseases and was associated with T-cell phenotype and involvement of the nasopharynx by the tumour.

Primary Ki-1-positive anaplastic large-cell lymphoma: a distinct clinicopathologic entity

The morphology of anaplastic large-cell lymphoma (ALCL) is associated with a clinical syndrome of peripheral lymphadenopathy (> 80%) and frequent extranodal disease (> 40%) in children and young adults (median age < 40 yrs.). Skin lesions occur in more than 20% of patients; other extranodal sites are bone, soft tissue, gastro-intestinal tract, lung, and pleura. Marrow involvement is infrequent (< 10%). Features that distinguish ALCL from Hodgkin's disease (HD) are noncontiguous nodal disease (> 50%), infrequent mediastinal mass (< 20%), and frequent inguinal lymphadenopathy (> 40%). Most patients present with stage III/IV disease. Stage is highly predictive of achieving complete remission, disease-free survival, and overall survival. Localized skin lesions have an excellent prognosis and occasional spontaneous regressions are noted. Distinctive histopathologic features of ALCL are partial lymph node involvement with sinus infiltration, sparing of B-cell regions, and tumor cell pleomorphism. Other features are high mitotic rate, necrosis, fibrosis, and plasma cell infiltrates. Morphologic variants of ALCL resemble carcinoma, syncytial variant of nodular sclerosing HD, true histiocytic lymphoma or interdigitating cell sarcoma, and mycosis fungoides. ALCL can be distinguished from these morphologically similar disorders by immunophenotype (CD30+, CD45+, CD15-, EMA+, BNH9+, keratin-, lysozyme-). A recurrent cytogenetic translocation, t(2;5) (p23; q35), has been observed among morphologic variants, including a small-cell-predominant variant and tumor cell line which contains a spectrum of small cerebriform and large anaplastic CD30+ cells. 70% of ALCL cases are of T-cell lineage, 15% B, 5% T/B, and 10% undefined.(ABSTRACT TRUNCATED AT 250 WORDS)