Detection of the t(2;5)(p23;q35) chromosomal translocation in large B-cell lymphomas other than anaplastic large cell lymphoma

TTC7A-ALK, a novel ALK fusion variant identified in a patient with metastatic lung adenocarcinoma, exhibits excellent response to crizotinib

Non-small cell lung cancer (NSCLC) remains a leading cause of cancer-related mortality worldwide. ALK gene rearrangement has been identified in 3 % to 5 % of the patients with NSCLC. Thanks to the advancements in second-generation sequencing technology, an increasing number of novel fusion partners have been identified. In our research, we discovered a rare ALK fusion, TTC7A-ALK, in a patient with advanced lung adenocarcinoma using targeted next-generation sequencing (NGS). After being diagnosed with advanced lung adenocarcinoma with TTC7A-ALK fusion, the patient received crizotinib treatment and achieved a progression-free survival of 29 months. Additonanlly, we conducted further functional analyses on this fusion protein to assess its oncogenic potential. Similar to EML4-ALK, the TTC7A-ALK fusion protein can promote the growth of Ba/F3 cells under IL-3-independent conditions in vitro. In vivo studies demonstrate that the TTC7A-ALK fusion protein could enhance the tumorigenesis of NIH3T3 cells in nude mice, which can be suppressed by crizotinib. Mechanistic studies indicated that the ectopic expression of TTC7A-ALK in 293T cells led to the hyperactivation of downstream MAPK and PI3K/Akt pathways, which can be inhibited by crizotinib. Furthermore, upon tumor progression, the patient transitioned to alectinib, which provided rapid symptom relief and controlled the majority of lesions. Conclusionly, we identified and validated TTC7A-ALK as a oncogenic fusion in NSCLC. The patient demonstrated a significant clinical benefit from sequential treatment with crizotinib and alectinib, highlighting TTC7A-ALK as a novel therapeutic target for ALK inhibitors. These findings extend the spectrum of actionable ALK fusions and promote the inclusion of rare fusion detection in clinical diagnostic processes and treatment strategies.

ELP3 Acetyltransferase is phosphorylated and regulated by the oncogenic anaplastic lymphoma kinase (ALK)

Protein lysine acetylation is one of the major posttranslational modifications (PTMs) with several thousands of proteins identified to be acetylated in mammalian tissues. Mechanistic studies have revealed important functions of acetylation in the regulation of protein function. Much less is known on how the acetyltransferases themselves are regulated. In the current study, we discover that the Elongator protein 3 (ELP3) acetyltransferase is modified by tyrosine phosphorylation. We demonstrate that the anaplastic lymphoma kinase (ALK) is the major tyrosine kinase responsible for ELP3 tyrosine phosphorylation. ELP3 is phosphorylated in tumor cells expressing oncogenic NPM–ALK fusion protein. We further identify Tyr202 as the major ALK phosphorylation site in ELP3. Importantly, the introduction of Y202 phosphorylation mutant ELP3 into ALK-positive tumor cells reduced cell growth and impaired gene expression. Collectively, our study reveals a novel regulatory mechanism for ELP3, provides an example that acetyltransferase itself can be regulated by PTM, and suggests a potential target for ALK-positive cancer therapies.

GCC2-ALK as a targetable fusion in lung adenocarcinoma and its enduring clinical responses to ALK inhibitors

OBJECTIVES

ALK, RET and ROS1 fusions have been identified as treatable targets in 5%-15% of non-small-cell lung cancers, and thanks to the advanced sequencing technologies, their new partner genes have been steadily detected. Here we identified a rare fusion of ALK (GCC2-ALK) in a patient with advanced lung adenocarcinoma and monitored the treatment efficacy of ALK inhibitors on this patient. We further performed in vitro functional studies of this fusion protein for evaluating its oncogenic potential.

MATERIALS AND METHODS

The GCC2-ALK fusion gene was identified by targeted next generation sequencing (NGS) from the tumor DNA samples, and its fusion product was confirmed by Sanger sequencing the cDNA product. The functional study of GCC2-ALK was performed in Ba/F3 cells with cell proliferation and viability assays. The activation of downstream signaling pathways of ALK and their responses to crizotinib inhibition were studied in HEK-293 and 293T cells with ectopic expression of GCC2-ALK. In parallel, disease progression in the patient was monitored by computed tomography scanning and targeted NGS of either liquid or tissue biopsy samples throughout and after crizotinib treatment.

RESULTS

Similarly to EML4-ALK, the GCC2-ALK fusion protein promotes IL-3-independent growth of Ba/F3 cells. Ectopic expression of GCC2-ALK leads to hyper-activation of ALK downstream signaling that can be inhibited by crizotinib. Crizotinib treatment of the patient resulted in 18 months of progression free survival without any trace of GCC2-ALK fusion in the liquid biopsies. Re-biopsy of a lung lesion at progression identified the re-occurrence of GCC2-ALK. The patient was then administrated with a second-generation ALK inhibitor, ceritinib, and received partial response until the last follow-up.

CONCLUSION

We identified and functionally validated GCC2-ALK as a constitutively activated fusion in NSCLC. The patient was benefited from crizotinib treatment initially and then ceritinib after progression, suggesting GCC2-ALK as a novel therapeutic target for ALK inhibitors.

Cell survival signaling in neuroblastoma

Neuroblastoma is the most common extracranial solid tumor of childhood and is responsible for over 15% of pediatric cancer deaths. Neuroblastoma tumorigenesis and malignant transformation is driven by overexpression and dominance of cell survival pathways and a lack of normal cellular senescence or apoptosis. Therefore, manipulation of cell survival pathways may decrease the malignant potential of these tumors and provide avenues for the development of novel therapeutics. This review focuses on several facets of cell survival pathways including protein kinases (PI3K, AKT, ALK, and FAK), transcription factors (NF-κB, MYCN and p53), and growth factors (IGF, EGF, PDGF, and VEGF). Modulation of each of these factors decreases the growth or otherwise hinders the malignant potential of neuroblastoma, and many therapeutics targeting these pathways are already in the clinical trial phase of development. Continued research and discovery of effective modulators of these pathways will revolutionize the treatment of neuroblastoma.

Cell culture and Drosophila model systems define three classes of anaplastic lymphoma kinase mutations in neuroblastoma

Neuroblastoma is a childhood extracranial solid tumour that is associated with a number of genetic changes. Included in these genetic alterations are mutations in the kinase domain of the anaplastic lymphoma kinase (ALK) receptor tyrosine kinase (RTK), which have been found in both somatic and familial neuroblastoma. In order to treat patients accordingly requires characterisation of these mutations in terms of their response to ALK tyrosine kinase inhibitors (TKIs). Here, we report the identification and characterisation of two novel neuroblastoma ALK mutations (A1099T and R1464STOP), which we have investigated together with several previously reported but uncharacterised ALK mutations (T1087I, D1091N, T1151M, M1166R, F1174I and A1234T). In order to understand the potential role of these ALK mutations in neuroblastoma progression, we have employed cell culture-based systems together with the model organism Drosophila as a readout for ligand-independent activity. Mutation of ALK at position 1174 (F1174I) generates a gain-of-function receptor capable of activating intracellular targets such as ERK (extracellular signal regulated kinase) and STAT3 (signal transducer and activator of transcription 3) in a ligand-independent manner. Analysis of these previously uncharacterised ALK mutants and comparison with ALK^F1174 mutants suggests that ALK mutations observed in neuroblastoma fall into three classes. These classes are: (i) gain-of-function ligand-independent mutations such as ALK^F1174l, (ii) kinase-dead ALK mutants, e.g. ALK^I1250T (Schönherr et al., 2011a) and (iii) ALK mutations that are ligand-dependent in nature. Irrespective of the nature of the observed ALK mutants, in every case the activity of the mutant ALK receptors could be abrogated by the ALK inhibitor crizotinib (Xalkori/PF-02341066), albeit with differing levels of sensitivity.

Novel treatment avenues for peripheral T-cell lymphomas

INTRODUCTION

Peripheral T-cell lymphomas (PTCLs) and natural killer (NK) or T-cell non-Hodgkin's lymphomas (NHLs) are a rare and heterogeneous class of diseases with generally poor prognosis. This work intends to provide a focused primer on clinical diagnosis, current treatment regimens, and novel therapeutic approaches. The recent WHO classification has defined 18 different subtypes of PTCL and NK T-cell lymphomas. Diagnosis is mainly based on histology, flow-cytometric analysis of surface molecules in the blood and bone marrow, cytogenetics/fluorescence in situ hybridization (FISH), and T-cell receptor (TCR) rearrangement. Staging as well as follow-up diagnostic procedures rely on imaging techniques such as computerized tomography (CT) and positron emission tomography (PET). Current chemotherapeutic regimens such as CHOP result in a 60 - 70% response rate; however, 5-year survival is only around 30%. Therefore, new treatment strategies are urgently needed. Currently, different drug classes are under scrutiny.

AREAS COVERED

The authors discuss substances that directly target the tumor cells. The article includes such substances as antimetabolites, antibodies, histone deacetylase inhibitors, tyrosine kinase inhibitors, and immunomodulatory substances such as lenalidomide.

EXPERT OPINION

In the future a close collaboration of geneticists, biochemists, and clinicians together with new technologies such as deep sequencing will allow the refinement of treatment strategies in many diseases including PTCLs and NHLs. This refinement will allow treatments to be prepared according to the need of the individual patient.

The R1275Q neuroblastoma mutant and certain ATP-competitive inhibitors stabilize alternative activation loop conformations of anaplastic lymphoma kinase

Anaplastic lymphoma kinase (ALK) is a receptor tyrosine kinase that, when genetically altered by mutation, amplification, chromosomal translocation or inversion, has been shown to play an oncogenic role in certain cancers. Small molecule inhibitors targeting the kinase activity of ALK have proven to be effective therapies in certain ALK-driven malignancies and one such inhibitor, crizotinib, is now approved for the treatment of EML4-ALK-driven, non-small cell lung cancer. In neuroblastoma, activating point mutations in the ALK kinase domain can drive disease progression, with the two most common mutations being F1174L and R1275Q. We report here crystal structures of the ALK kinase domain containing the F1174L and R1275Q mutations. Also included are crystal structures of ALK in complex with novel small molecule ALK inhibitors, including a classic type II inhibitor, that stabilize previously unobserved conformations of the ALK activation loop. Collectively, these structures illustrate a different series of activation loop conformations than has been observed in previous ALK crystal structures and provide insight into the activating nature of the R1275Q mutation. The novel active site topologies presented here may also aid the structure-based drug design of a new generation of ALK inhibitors.

NPM-ALK: The Prototypic Member of a Family of Oncogenic Fusion Tyrosine Kinases

Anaplastic lymphoma kinase (ALK) was first identified in 1994 with the discovery that the gene encoding for this kinase was involved in the t(2;5)(p23;q35) chromosomal translocation observed in a subset of anaplastic large cell lymphoma (ALCL). The NPM-ALK fusion protein generated by this translocation is a constitutively active tyrosine kinase, and much research has focused on characterizing the signalling pathways and cellular activities this oncoprotein regulates in ALCL. We now know about the existence of nearly 20 distinct ALK translocation partners, and the fusion proteins resulting from these translocations play a critical role in the pathogenesis of a variety of cancers including subsets of large B-cell lymphomas, nonsmall cell lung carcinomas, and inflammatory myofibroblastic tumours. Moreover, the inhibition of ALK has been shown to be an effective treatment strategy in some of these malignancies. In this paper we will highlight malignancies where ALK translocations have been identified and discuss why ALK fusion proteins are constitutively active tyrosine kinases. Finally, using ALCL as an example, we will examine three key signalling pathways activated by NPM-ALK that contribute to proliferation and survival in ALCL.

Anaplastic lymphoma kinase in human cancer

The receptor tyrosine kinases (RTKs) play a critical role, controlling cell proliferation, survival, and differentiation of normal cells. Their pivotal function has been firmly established in the pathogenesis of many cancers as well. The anaplastic lymphoma kinase (ALK), a transmembrane RTK, originally identified in the nucleophosmin (NPM)-ALK chimera of anaplastic large cell lymphoma, has emerged as a novel tumorigenic player in several human cancers. In this review, we describe the expression of the ALK-RTK, its related fusion proteins, and their molecular mechanisms of activation. Novel tailored strategies are briefly illustrated for the treatment of ALK-positive neoplasms.

Hypoxia-microRNA-16 downregulation induces VEGF expression in anaplastic lymphoma kinase (ALK)-positive anaplastic large-cell lymphomas

The anaplastic lymphoma kinase (ALK), tyrosine kinase oncogene is implicated in a wide variety of cancers. In this study we used conditional onco-ALK (NPM-ALK and TPM3-ALK) mouse MEF cell lines (ALK+ fibroblasts) and transgenic models (ALK+ B-lymphoma) to investigate the involvement and regulation of angiogenesis in ALK tumor development. First, we observed that ALK expression leads to downregulation of miR-16 and increased Vascular Endothelial Growth Factor (VEGF) levels. Second, we found that modification of miR-16 levels in TPM3-ALK MEF cells greatly affected VEGF levels. Third, we demonstrated that miR-16 directly interacts with VEGF mRNA at the 3'-untranslated region and that the regulation of VEGF by miR-16 occurs at the translational level. Fourth, we showed that expression of both the ALK oncogene and hypoxia-induced factor 1α (HIF1α) is a prerequisite for miR-16 downregulation. Fifth, in vivo, miR-16 gain resulted in reduced angiogenesis and tumor growth. Finally, we highlighted an inverse correlation between the levels of miR-16 and VEGF in human NPM-ALK+ Anaplastic Large Cell Lymphomas (ALCL). Altogether, our results demonstrate, for the first time, the involvement of angiogenesis in ALK+ ALCL and strongly suggest an important role for hypoxia-miR-16 in regulating VEGF translation.

Anaplastic lymphoma kinase: signalling in development and disease

RTKs (receptor tyrosine kinases) play important roles in cellular proliferation and differentiation. In addition, RTKs reveal oncogenic potential when their kinase activities are constitutively enhanced by point mutation, amplification or rearrangement of the corresponding genes. The ALK (anaplastic lymphoma kinase) RTK was originally identified as a member of the insulin receptor subfamily of RTKs that acquires transforming capability when truncated and fused to NPM (nucleophosmin) in the t(2;5) chromosomal rearrangement associated with ALCL (anaplastic large cell lymphoma). To date, many chromosomal rearrangements leading to enhanced ALK activity have been described and are implicated in a number of cancer types. Recent reports of the EML4 (echinoderm microtubule-associated protein like 4)–ALK oncoprotein in NSCLC (non-small cell lung cancer), together with the identification of activating point mutations in neuroblastoma, have highlighted ALK as a significant player and target for drug development in cancer. In the present review we address the role of ALK in development and disease and discuss implications for the future.

ALK-positive diffuse large B-cell lymphoma: report of four cases and review of the literature

We report detailed clinical and pathologic features of four cases of anaplastic lymphoma kinase-positive diffuse large B-cell lymphoma (ALK-DLBCL), a rare entity with only 29 currently reported cases. This study is the third largest of all reported series. Biopsies from four adult patients aged 41, 49, 53, and 71 years (three lymph nodes and one nasopharyngeal mass) exhibited immunoblastic/plasmablastic morphology. By immunohistochemistry and/or flow cytometry, they expressed cytoplasmic ALK-1, CD138, VS38 (3/3), monoclonal cytoplasmic light chain, CD45, EMA, CD4, and CD57 (2/3), and were negative for CD3, CD30, CD56, and TIA-1. Two showed variable CD79a expression, and one had rare CD20(+) cells. Two of three cases exhibited rare CD43(+) reactivity. One case showed scattered cytokeratin(+) cells, which could possibly lead to a misdiagnosis of carcinoma. After CHOP and radiotherapy, two stage I patients were free of disease at 58 and 36 months, whereas a stage IV patient was dead of disease at 22 months.

A case of a diffuse large B-cell lymphoma of plasmablastic type associated with the t(2;5)(p23;q35) chromosome translocation

Anaplastic large cell lymphomas are associated with the t(2;5)(p23;q35) chromosome translocation in 40% to 60% of cases, leading to a new chimeric gene NPM-ALK. NPM-ALK positive lymphomas are generally reported to be of either T cell or null phenotype. In this report, we describe a diffuse large B-cell lymphoma associated with the classic t(2;5) translocation and both nuclear and cytoplasmic expression of ALK. The tumor consisted of medium-sized to large immunoblasts and plasmablasts that on immunohistology were negative for CD30, CD20, and CD79a but showed monotypic cytoplasmic expression of lambda light chains. Clonality analysis confirmed B-cell lineage of the tumor cells. The t(2;5)(p23;q35) chromosome translocation was demonstrated as part of a complex karyotypic alteration by classic banding and spectral karyotyping (SKY) analyses. Reverse transcription polymerase chain reaction confirmed rearrangement of NPM and ALK genes. This case exemplifies that the t(2;5) can, albeit rarely, occur in large B-cell lymphomas and is not entirely limited to anaplastic large cell lymphomas of T or null cell phenotypes.

ALK activation by the CLTC-ALK fusion is a recurrent event in large B-cell lymphoma

We present 3 cases of large B-cell lymphoma (LBCL) with a granular cytoplasmic staining for anaplastic lymphoma kinase (ALK). All of the cases showed striking similarities in morphology and immunohistochemical profile characterized by a massive monomorphic proliferation of CD20-/CD138+ plasmablast-like cells. In one of the cases, initially diagnosed as a null-type anaplastic large cell lymphoma (ALCL), the B-cell phenotype became evident only at recurrence. Fluorescent in situ hybridization (FISH) and molecular studies led to the detection of a CLTC-ALK rearrangement in all 3 cases, without any evidence of full-length ALK receptor expression. The associated t(2;17)(p23;q23) was demonstrated in the karyotype of 2 cases. Although a similar CLTC-ALK aberration was previously identified in ALK-positive T-/null cell ALCL and inflammatory myofibroblastic tumor, its association with ALK-positive LBCL seems to be specific and intriguing.

Common ALK gene rearrangement in Asian CD30+ anaplastic large cell lymphoma: an immunohistochemical and fluorescence in situ hybridisation (FISH) study on paraffin-embedded tissue

AIMS

The most common recurrent genetic aberration in anaplastic large cell lymphoma (ALCL) is translocation involving the ALK gene that results in ectopic expression of ALK protein in lymphoid tissue. This study aims to investigate the frequency of ALK gene rearrangement in a series of Asian ALCL.

METHODS

ALK gene rearrangement was detected by immunostaining of ALK protein and fluorescence in situ hybridisation (FISH) targeting at the 2p23 region.

RESULTS

The expression of ALK protein was detected in 24/34 (71%) of the cases, and it was significantly higher in childhood cases (100%) when compared to adult cases (47%). The analyses by FISH were consistent with the results from immunostaining of ALK protein, but the analyses were only successful in 15/34 (44%) cases. FISH analyses detected extra copies of ALK gene in three cases, including one case that expressed ALK protein and showed 2p23 rearrangement.

CONCLUSIONS

The current series revealed a high frequency of ALK gene rearrangement, especially in the children. Immunostaining of ALK protein is a reliable indication of ALK gene rearrangement, and is superior to FISH. However, FISH analysis is useful in detecting other genetic aberrations that are not related to ALK gene rearrangement.

Morphological and phenotypic features in pediatric large cell lymphoma and their correlation with ALK expression and the t(2;5)(p23;q35) translocation

Anaplastic large cell lymphoma (ALCL) was proposed as a clinicopathologic entity over 14 years ago, but has been somewhat controversial due to the variability of its defining features and variable occurrence in different age-groups. To evaluate this entity in a pediatric population, 36 cases of childhood large cell lymphoma were evaluated for abnormalities of the anaplastic lymphoma kinase (ALK) gene that has been associated with ALCL morphology and immunophenotype. ALK abnormalities were evaluated by assay for the t(2;5)(p23;q35) translocation by RT-PCR and/or expression of NPM-ALK fusion protein by immunohistochemistry. Results showed 17 patients to have evidence of ALK gene expression. All of these children (mean age, 9.3 years) had tumors that were of T-cell phenotype (with the exception of a single case of null phenotype) and that expressed CD30. In contrast, 19 children with no evidence of ALK expression were older (mean, 12.7 years), and the majority (12/19) had tumors of B-cell phenotype. CD30 was also diffusely expressed in 8 of these 19 tumors. The difference in mean age between the two groups was statistically significant (P = 0.015). In three cases tested for both ALK and the t(2;5), ALK protein was detected in the absence of the t(2;5) translocation but no cases showed the reverse pattern, consistent with ALK fusion to genes other than NPM or activation of the ALK gene by another mechanism. These findings provide further support that ALK-positive ALCL is a distinct pathologic entity among pediatric large cell lymphomas primarily characterized by expression of T-cell markers, CD30, and EMA, and by a younger mean age.

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.

Anaplastic large-cell lymphomas of B-cell phenotype are anaplastic lymphoma kinase (ALK) negative and belong to the spectrum of diffuse large B-cell lymphomas

There is controversy in the literature as to whether anaplastic large-cell lymphoma of B-cell phenotype is related to the t(2;5)-positive T- or 'null' cell lymphoma of the same morphology. We report a study of 24 lymphomas with morphological features of anaplastic large-cell lymphoma which expressed one or more B-cell markers and lacked T-lineage markers. Clinical features were more in keeping with large B-cell lymphoma than with classical t(2;5)-positive anaplastic large-cell lymphoma, and immunostaining for anaplastic lymphoma kinase (ALK) protein provided no evidence for the (2;5) translocation (or one of its variants). The staining patterns for CD20 and CD79 were typical of diffuse large B-cell lymphoma, CD30 expression was variable, and most cases (15/22) lacked epithelial membrane antigen (EMA). These findings support the view that 'B-cell anaplastic large-cell lymphoma' is unrelated to t(2;5)-positive (ALK-positive) lymphoma, and that it represents a morphological pattern occasionally encountered among diffuse large B-cell lymphomas. By the same reasoning, most tumours diagnosed as 'ALK-negative anaplastic large-cell lymphoma of T-cell or null phenotype' probably belong to the spectrum of peripheral T-cell lymphomas.

Anaplastic large cell lymphoma: a clinicopathologic analysis

The clinicopathologic features of anaplastic large cell lymphoma (ALCL) are reviewed. ALCL is a heterogeneous group of tumours, and histologic examination alone is not adequate in providing useful prognostic information. However, using a combination of clinical, phenotypic, and genotypic features, several distinct clinicopathologic entities have been identified. A subset of ALCL as presently defined is characterized by a balanced translocation, t(2;5)(p23;q35), resulting in a novel fusion protein (NPM-ALK) that can be readily detected by immunohistochemical methods using antibodies against the ALK protein. Detection of ALK protein, along with other methods for demonstrating the t(2;5), has assisted in identifying a distinct biologic entity within the heterogeneous group of ALCL with significant prognostic implications. It is important to separate these from cases of ALK-negative ALCL, which have a poorer prognosis, and cases of primary cutaneous ALCL, which have an excellent prognosis.

Prognostic Significance of Anaplastic Lymphoma Kinase (ALK) Protein Expression in Adults With Anaplastic Large Cell Lymphoma

Anaplastic large cell lymphoma (ALCL) is an aggressive lymphoma that is frequently associated with the t(2;5)(p23;q35), resulting in expression of a fusion protein, nucleophosmin-anaplastic lymphoma kinase (NPM-ALK), which can be detected by either monoclonal or polyclonal antibodies to the ALK protein. The clinical features of adults with ALCL are incompletely described, and the prognostic factors that are useful for predicting survival remain unclear. This report describes the clinical and laboratory findings in 70 adults with systemic ALCL who were treated with curative intent. We attempted to identify the clinical and pathological factors of prognostic importance, including the International Prognostic Index (IPI), immunophenotype, and expression of the ALK protein. The median age of the patients was 49 years (range, 15 to 75). There were 26 women and 44 men with a median follow-up of 50 months for living patients. Advanced stage was present in 56% and B symptoms were noted in 70% of the patients. Immunostains showed that 46% of the cases had a T-cell phenotype, 36% a null phenotype, and 18% a B-cell phenotype. The expression of ALK protein was found in 51% of the cases. The IPI factors were evenly distributed between the ALK+ and ALK− groups, except that the ALK+ patients were younger (median age, 30 v 61 years; P < .002). The ALK+ cohort included cases with null (44%), T-cell (42%), and B-cell (14%) phenotypes. All 10 cases with cytogenetic or molecular evidence of a t(2;5) were ALK+. The 5-year overall survival (OS) of the entire cohort was 65%. The 5-year OS of the ALK+ and ALK− cases was 79% and 46%, respectively (P < .0003). Analysis of only the T-cell/null cases (n = 57) showed a 5-year OS of 93% for the ALK+ cases and only 37% for the ALK− cases (P < .00001). Univariate analysis of the clinical features showed that age ≤60 years (P < .007), a normal serum lactate dehydrogenase (LDH) (P < .00001), a good performance status (Eastern Cooperative Oncology Group [ECOG] <2) (P< .03), ≤1 extranodal site of disease (P < .012), and an IPI score ≤3 (P < .00001) were associated with improved OS. Although a younger age correlated with ALK positivity, multivariate analysis showed that only a normal serum LDH (P < .00001), an IPI score of ≤3 (P < .0005), and ALK protein expression (P < .005) predicted independently for an improved OS. We conclude that ALCL is a heterogeneous disorder. However, ALK protein expression is an independent predictor of survival and serves as a useful biologic marker of a specific disease entity within the spectrum of ALCL.

Prognostic Significance of Anaplastic Lymphoma Kinase (ALK) Protein Expression in Adults With Anaplastic Large Cell Lymphoma

Anaplastic large cell lymphoma (ALCL) is an aggressive lymphoma that is frequently associated with the t(2;5)(p23;q35), resulting in expression of a fusion protein, nucleophosmin-anaplastic lymphoma kinase (NPM-ALK), which can be detected by either monoclonal or polyclonal antibodies to the ALK protein. The clinical features of adults with ALCL are incompletely described, and the prognostic factors that are useful for predicting survival remain unclear. This report describes the clinical and laboratory findings in 70 adults with systemic ALCL who were treated with curative intent. We attempted to identify the clinical and pathological factors of prognostic importance, including the International Prognostic Index (IPI), immunophenotype, and expression of the ALK protein. The median age of the patients was 49 years (range, 15 to 75). There were 26 women and 44 men with a median follow-up of 50 months for living patients. Advanced stage was present in 56% and B symptoms were noted in 70% of the patients. Immunostains showed that 46% of the cases had a T-cell phenotype, 36% a null phenotype, and 18% a B-cell phenotype. The expression of ALK protein was found in 51% of the cases. The IPI factors were evenly distributed between the ALK+ and ALK− groups, except that the ALK+ patients were younger (median age, 30 v 61 years; P < .002). The ALK+ cohort included cases with null (44%), T-cell (42%), and B-cell (14%) phenotypes. All 10 cases with cytogenetic or molecular evidence of a t(2;5) were ALK+. The 5-year overall survival (OS) of the entire cohort was 65%. The 5-year OS of the ALK+ and ALK− cases was 79% and 46%, respectively (P < .0003). Analysis of only the T-cell/null cases (n = 57) showed a 5-year OS of 93% for the ALK+ cases and only 37% for the ALK− cases (P < .00001). Univariate analysis of the clinical features showed that age ≤60 years (P < .007), a normal serum lactate dehydrogenase (LDH) (P < .00001), a good performance status (Eastern Cooperative Oncology Group [ECOG] <2) (P< .03), ≤1 extranodal site of disease (P < .012), and an IPI score ≤3 (P < .00001) were associated with improved OS. Although a younger age correlated with ALK positivity, multivariate analysis showed that only a normal serum LDH (P < .00001), an IPI score of ≤3 (P < .0005), and ALK protein expression (P < .005) predicted independently for an improved OS. We conclude that ALCL is a heterogeneous disorder. However, ALK protein expression is an independent predictor of survival and serves as a useful biologic marker of a specific disease entity within the spectrum of ALCL.

Malignant histiocytic disorders in children. Clinical and therapeutic approaches with a nosologic discussion

Malignant histiocytic disorders, other than leukemias, are extremely rare in childhood. Despite unresolved nosologic and terminologic difficulties, they should be classified according to the lineage of the aberrant cells in a given tumor. There are no common and typical clinical presentations, nor are there established treatment modalities available. For the disseminated forms, aggressive systemic treatment modalities--similar if not identical to those used for large cell anaplastic lymphomas--appear to be the best treatment option. For the localized forms, which are primarily dendritic cell sarcomas, a more localized and individualized therapy is appropriate.

The t(2;5) in human lymphomas

A recurrent, reciprocal balanced translocation, t(2;5) (p23;q35), has been recognized in CD30+ anaplastic large-cell lymphomas (ALCL), a newly recognized subtype comprising approximately 5% of all non-Hodgkin's lymphoma (NHL). This translocation creates a novel fusion protein, NPM-ALK, which has transforming properties in vitro and can cause large-cell lymphoma in vivo when transfected into murine bone marrow. Multiple techniques including reverse transcriptase-polymerase chain reaction (RT-PCR) amplification of NPM-ALK fusion transcripts, genomic DNA-PCR, RNA in situ hybridization, and fluorescence in situ hybridization (FISH) of metaphase chromosomes and interphase nuclei, and immunohistochemical detection of the 80 kilodalton protein (p80) derived from the NPM-ALK fusion have enabled surveys of normal and lymphoma tissues for evidence of the translocation. These studies suggest that expression of ALK protein, a novel orphan receptor tyrosine kinase, is normally confined to the nervous system. In lymphoma, NPM-ALK expression is most often seen in young patients with the monomorphic or small-cell variant of ALCL who present with advanced stage disease and have tumors with a CD30+, T- or null-cell phenotype. It is less frequently detected in older patients and in ALCL of pleomorphic histology. In addition, expression of NPM-ALK has been found in occasional CD30 negative B-cell lymphomas with diffuse large cell or immunoblastic histology. NPM-ALK is rarely, if ever, detected in Hodgkin's disease or secondary ALCL. Although initially found in primary nodal ALCL, recent studies suggest that NPM-ALK expression may occur in lymphoma at extranodal sites, including the skin; it remains controversial, however, whether CD30+ primary cutaneous lymphoma and its benign counterpart, lymphomatoid papulosis (LyP), express NPM-ALK in some cases. A retrospective study has suggested that expression of NPM-ALK is associated with a better overall 5-year survival; these results must be confirmed in prospective studies of patients with uniform staging and therapy to more fully understand the clinical significance of the t(2;5) and its novel chimeric protein, NPM-ALK.

ALK-Positive Lymphoma: A Single Disease With a Broad Spectrum of Morphology

The t(2;5)(p23;q35) translocation, associated with anaplastic large-cell lymphoma (ALCL), results in the expression of a chimeric NPM-ALK protein that can be detected by the ALK1 monoclonal antibody. This report describes the morphologic and phenotypic spectrum of 123 cases of lymphoma that all express ALK protein. The results provide strong evidence that the morphologic patterns of ALCL described in previous reports as representing possible subtypes of ALCL, eg, common type, lymphohistiocytic, or small cell patterns, are morphologic variants of the same disease entity. All of these morphologic patterns could be found within this series, and in some patients different subtypes coexisted in a single biopsy or were found in successive biopsies from a single patient. The link between these morphologic subtypes is further reinforced by the presence in all cases of a highly characteristic large cell, with an eccentric nucleus and an eosinophilic paranuclear region. We suggest that this cell can be considered as a major distinguishing feature of ALK-positive lymphomas. Another characteristic of these tumors was the perivascular pattern of neoplastic cell infiltration seen in a significant number of cases. In addition to ALK protein, all tumors expressed epithelial membrane antigen and lacked CD15, features that may be of value in differentiating ALCL from Hodgkin's disease. In the majority of cases (84%), malignant cells showed both a cytoplasmic and nuclear staining for ALK1 and thus presumably carried the 2;5 translocation, but staining was restricted to the cytoplasm in a few cases, suggesting that translocations other than t(2;5) may induce expression of ALK protein. We conclude from this study that ALK-positive neoplasms represent a distinct entity. Because their morphology is often neither anaplastic nor large cell, we suggest that they should henceforward be referred to as ALK lymphomas.

ALK-Positive Lymphoma: A Single Disease With a Broad Spectrum of Morphology

The t(2;5)(p23;q35) translocation, associated with anaplastic large-cell lymphoma (ALCL), results in the expression of a chimeric NPM-ALK protein that can be detected by the ALK1 monoclonal antibody. This report describes the morphologic and phenotypic spectrum of 123 cases of lymphoma that all express ALK protein. The results provide strong evidence that the morphologic patterns of ALCL described in previous reports as representing possible subtypes of ALCL, eg, common type, lymphohistiocytic, or small cell patterns, are morphologic variants of the same disease entity. All of these morphologic patterns could be found within this series, and in some patients different subtypes coexisted in a single biopsy or were found in successive biopsies from a single patient. The link between these morphologic subtypes is further reinforced by the presence in all cases of a highly characteristic large cell, with an eccentric nucleus and an eosinophilic paranuclear region. We suggest that this cell can be considered as a major distinguishing feature of ALK-positive lymphomas. Another characteristic of these tumors was the perivascular pattern of neoplastic cell infiltration seen in a significant number of cases. In addition to ALK protein, all tumors expressed epithelial membrane antigen and lacked CD15, features that may be of value in differentiating ALCL from Hodgkin's disease. In the majority of cases (84%), malignant cells showed both a cytoplasmic and nuclear staining for ALK1 and thus presumably carried the 2;5 translocation, but staining was restricted to the cytoplasm in a few cases, suggesting that translocations other than t(2;5) may induce expression of ALK protein. We conclude from this study that ALK-positive neoplasms represent a distinct entity. Because their morphology is often neither anaplastic nor large cell, we suggest that they should henceforward be referred to as ALK lymphomas.

t(2;5) positive lymphoma with peripheral blood involvement

We report two cases of CD30 and t(2;5) positive lymphomas with peripheral blood (PB) involvement. Case one demonstrated the histological appearance of a diffuse large cell lymphoma with disease in the bone marrow (BM) and PB. Immunoperoxidase stains of the BM for CD30 proved to be of value in detecting disease. RT-PCR for the t(2;5) translocation product was positive in the PB, BM and lymph node. Case two had a typical anaplastic large cell lymphoma (ALCL) morphology, with a suboptimal BM biopsy, but abnormal circulating cells in the PB showing the presence of the NPM/ALK fusion product demonstrated by RT-PCR. The first case demonstrates that not all CD30 positive and t(2;5)-associated lymphomas have an anaplastic appearance. Routine staining for CD30 and EMA in BM biopsies is useful for pathological staging. The significance of the t(2;5) in defining a specific histological subtype is unclear. RT-PCR for the t(2;5) is a more sensitive test to detect disease in PB and BM as compared with light microscopy. The clinical significance of molecular staging for patients with ALCL using RT-PCR needs to be evaluated.

Retrovirus-Mediated Gene Transfer of NPM-ALK Causes Lymphoid Malignancy in Mice

Approximately 5% to 10% of all non-Hodgkin's lymphomas contain a t(2; 5)(p23; q35) chromosomal rearrangement, which we have previously shown results in the generation of the fusion protein nucleophosmin-anaplastic lymphoma kinase (NPM-ALK). To assess the transforming potential of NPM-ALK in an animal model, we infected 5-fluorouracil–treated murine bone marrow using retroviral stocks and transplanted this infected marrow into lethally irradiated BALB/cByJ mice. Male mice were transplanted with bone marrow from female donors at 10 weeks of age, with 7 of the animals receiving marrow infected with a retroviral construct, pSRαMSVtkneo-NPM-ALK, that contains the human NPM-ALK cDNA, and 4 serving as a control group, receiving “empty” pSRαMSVtkneo-infected marrow. Whereas all mice in the control group were alive and well up to 11 months after transplantation, 4 of the 7 mice transplanted with marrow containing the NPM-ALK construct developed lymphoma within 4 to 6 months. Tumors arose in the mesenteric lymph nodes, with metastases to the lungs, kidneys, liver, spleen, and the paraspinal area. When cells from the tumors and bone marrow were transplanted into sublethally irradiated secondary recipients, 10 of these 13 mice developed tumors within 9 months. Immunoblot analysis of cell lysates using an ALK polyclonal antibody showed NPM-ALK expression in all tumors examined. Histologically, the tumors were composed of a uniform population of large immunoblastic cells with basophilic cytoplasm, centrally placed nuclei, and distinct nucleoli. Genotypic analysis showed that the tumors were B-lineage and clonal, with rearrangements of the Ig heavy- and κ light-chain loci and no rearrangements of the T-cell receptor β locus. Immunocytochemical studies confirmed the presence of IgM heavy chains and κ light chains within the tumor cells. Thus, in this retroviral gene transfer model, NPM-ALK expression in mice causes B-lineage large-cell lymphoma, suggesting a direct causative role for this activated fusion tyrosine kinase in human lymphoma.

Contemporary classification of histiocytic disorders. The WHO Committee On Histiocytic/Reticulum Cell Proliferations. Reclassification Working Group of the Histiocyte Society

Pathologists and pediatric hematologist/ oncologists of the World Health Organization's Committee on Histiocytic/Reticulum Cell Proliferations and the Reclassification Working Group of the Histiocyte Society present a classification of the histiocytic disorders that primarily affect children. Nosology, based on the lineage of lesional cells and biological behavior, is related to the ontogeny of histiocytes (macrophages and dendritic cells of the immune system). Dendritic cell-related disorders of varied biological behavior are dominated by Langerhans cell histiocytosis, but separate secondary proliferations of dendritic cells must be differentiated. Juvenile xanthogranuloma represents a disorder of dermal dendrocytes, another dendritic cell of skin. The hemophagocytic syndromes are the most common of the macrophage-related disorders of varied biological behavior. Guidelines for distinguishing the exceedingly rare malignant diseases of histiocytes from large cell lymphomas through the use of a battery of special studies are provided.

Cytotoxic Cell Antigen Expression in Anaplastic Large Cell Lymphomas of T- and Null-Cell Type and Hodgkin's Disease: Evidence for Distinct Cellular Origin

Anaplastic large cell lymphoma (ALCL) is composed of large, frequently bizarre, cells of T- or null-cell phenotype that show a preferential sinusoidal growth pattern and consistent CD30 positivity. Whether these tumors represent a single entity or several, and what the exact cell origin, is controversial. Recently, granzyme B, a cytotoxic granule component, was reported in a small percentage of ALCL, suggesting that some cases may originate from cytotoxic lymphocytes. To further investigate this possibility, we performed an immunohistochemical study of 33 ALCLs of T- and null-cell type, using monoclonal antibodies to cytotoxic cell-associated antigens, including CD8, CD56, CD57, and the cytotoxic granular proteins perforin and TIA-1. In addition, CD4 expression was also evaluated. ALCL cases included 27 classical systemic forms and variants, 3 primary cutaneous (PC) forms, and 3 acquired immunodeficiency syndrome-associated forms. Cytotoxic antigen expression was also studied in 51 cases of Hodgkin's disease (HD) and 17 large B-cell lymphomas (LBCLs) with anaplastic cytomorphology and/or CD30 positivity. We found that 76% of ALCLs, representing all subtypes except the PC forms, expressed either TIA-1, perforin, or both proteins. Expression of TIA-1 and perforin were highly correlated (P < .001). On the basis of their immunophenotypic profiles, several subtypes of cytotoxic antigen positive and negative ALCL could be recognized. Fifty-five percent of ALCLs (18 of 33) displayed an immunophenotypic profile consistent with cytotoxic T cells. Six cases expressed cytotoxic granular proteins in the absence of lineage specific markers, and one case expressed both T-cell – and natural killer cell–like markers. These 7 cases (21%) were placed into a phenotypic category of cytotoxic lymphocytes of unspecified subtype. Twenty-four percent (8 cases) of ALCLs were cytotoxic granule protein negative. All but one of these displayed a T-cell phenotype. Cytotoxic granule protein expression did not correlate with the presence of the NPM-ALK fusion transcript. Only 10% of the 51 HD cases were found to be TIA-1+, and none expressed perforin. Cytotoxic antigen expression was absent in LBCL. The expression of cytotoxic granule proteins in the majority of ALCL implies a cytotoxic lymphocyte phenotype and suggests that most cases originate from lymphocytes with cytotoxic potential. Furthermore, the demonstration of cytotoxic cell related proteins may be a useful addition to the current panel of antibodies used to distinguish ALCL, HD, and anaplastic LBCL.