Hyperactivated STAT3 in ALK-positive diffuse large B-cell lymphoma with clathrin-ALK fusion

ALK-positive large B-cell lymphoma: a clinicopathological and molecular characteristics analysis of seven cases

Anaplastic lymphoma kinase-positive large B-cell lymphoma (ALK+ LBCL) is a rare and highly aggressive lymphoma with characteristic ALK rearrangements. Various fusion genes involving ALK have been demonstrated, but the influence of the ALK fusion partners on ALK protein expression and the genetic characteristics of ALK+ LBCL remain relatively unknown. In this study, we conducted an extensive clinicopathological and molecular analysis on seven cases of ALK+ LBCL to explore the correlation between ALK fusion genes and ALK protein expression, thereby enriching the genetic characteristics of this tumour. We integrated the findings from clinical, histopathological/immunophenotypic, and molecular studies, including three samples subjected to next-generation sequencing, and six cases underwent RNA-based ALK fusion gene detection. We identified five distinct types of ALK fusion genes, including CLTC, NPM1, PABPC1, SEC31A, and TFG. Notably, only the NPM1::ALK fusion showed nuclear and cytoplasmic ALK staining, and the remaining four fusion genes resulted in cytoplasmic ALK staining. Our analysis revealed that the CLTC::ALK fusion resulted in a unique cytoplasmic perinuclear Golgi zone focal granular heterogeneous staining pattern of ALK. Additionally, we identified six potentially clinically significant gene mutations, including TET2, CHD2, DTX1, KMT2D, LRP1B, and XPO1. Furthermore, in all cases, the absence of 5-hydroxymethylcytosine (5hmC) was observed. We present seven cases of ALK+ LBCL, discussing the correlation between fusion genes and ALK protein expression, and enhancing our understanding of the genetic attributes of this tumour. This study also shows the loss of 5hmC in nearly all seven ALK+ LBCL cases, independently of TET2 mutations.

Anaplastic lymphoma kinase-positive large B-cell lymphoma (ALK + LBCL): a systematic review of clinicopathological features and management

Anaplastic lymphoma kinase-positive (ALK+) large B-cell lymphoma (LBCL) is a rare CD20-negative aggressive lymphoma. Given its rarity, data on ALK + LBCL are scarce and limited to case reports and small case series. Our systematic review included 184 unique cases published in the literature and shows that ALK + LBCL can affect individuals at any age, has a male predominance and is not associated with chronic viral infections. The malignant cells express ALK, VS38c, BLIMP-1, EMA, c-MYC, and BOB-1. The STAT3/STAT5, PI3K/AKT, PLCG2, and ERK pathways are important in the pathophysiology of ALK + LBCL. The prognosis of ALK + LBCL is poor with a 5-year survival rate of 28%. Early disease stage is associated with better outcomes. ALK inhibitors and other targeted agents could be of value in the treatment of ALK + LBCL. Additional research is needed to better understand, diagnose and treat ALK + LBCL.

Quality Initiative in Clinical Practice: A Single-Institution Appraisal of Quality Metrics in the Management of Newly Diagnosed Diffuse Large B-Cell Lymphoma

Objective

To assess our adherence to treatment guidelines for diffuse large B-cell lymphoma (DLBCL) established by the American Society of Hematology in 2014 through implementation of a quality improvement initiative (QII) at our institution in 2015.

Patients and Methods

Patients with newly diagnosed DLBCL treated from January 1, 2006, through December 31, 2017, were identified. Electronic medical records were reviewed for documentation of American Society of Hematology Practice Improvement Module quality measures (eg, key pathologic features of DLBCL, lymphoma staging, and screening for hepatitis B virus [HBV] infection in patients receiving rituximab-based chemotherapy). We also reviewed assessment of prognosis by revised International Prognostic Index score, testing for hepatitis C virus, HBV, and HIV, chemotherapy education, and the addition of rituximab in the treatment regimen of CD20⁺ DLBCL.

Results

Following QII implementation, we saw improvements in most metrics, including reporting of key molecular features (fluorescence in situ hybridization for c-MYC, BCL2, and BCL6, from 45.5% [75 of 165 patients] before QII to 91.7% [22 of 24 patients] after QII; P<.001), screening for HBV (41.8% [69 of 165 patients] to 91.7% [22 of 24 patients]; P<.001) and HIV infections (33.9% [56 of 165 patients] to 87.5% [21 of 24 patients]; P<.0001), providing chemotherapy education (92.7% [153 of 165 patients] to 100%), and use of rituximab for CD20⁺ DLBCL (83.6% [138 of 165 patients] to 100%; P=.05). All patients had positron emission tomography–computed tomography for DLBCL staging, and there was significantly lower use of bone marrow biopsy (P=.011).

Conclusion

Implementating a QII and employing standardized metrics can aid in improving quality of care for patients with newly diagnosed DLBCL and allow opportunities to build and ensure better adherence to evolving patient care guidelines.

Comparative RNA-Sequencing Analysis Benefits a Pediatric Patient With Relapsed Cancer

Clinical detection of sequence and structural variants in known cancer genes points to viable treatment options for a minority of children with cancer.¹ To increase the number of children who benefit from genomic profiling, gene expression information must be considered alongside mutations.^2,3 Although high expression has been used to nominate drug targets for pediatric cancers,^4,5 its utility has not been evaluated in a systematic way.⁶ We describe a child with a rare sarcoma that was profiled with whole-genome and RNA sequencing (RNA-Seq) techniques. Although the tumor did not harbor DNA mutations targetable by available therapies, incorporation of gene expression information derived from RNA-Seq analysis led to a therapy that produced a significant clinical response. We use this case to describe a framework for inclusion of gene expression into the clinical genomic evaluation of pediatric tumors.

ALK-positive Large B-cell Lymphoma: A Clinicopathologic Study of 26 Cases With Review of Additional 108 Cases in the Literature

Anaplastic lymphoma kinase-positive large B-cell lymphoma (ALK LBCL) is a rare, aggressive subtype of diffuse large B-cell lymphoma with characteristic ALK rearrangements. Diagnosis of ALK LBCL can be challenging because of its rarity, unique morphologic characteristics, and unusual immunophenotypic features, which significantly overlap with other hematologic and nonhematologic neoplasms. The purpose of this study is to further explore the clinicopathologic features of ALK LBCL to ensure the awareness and accurate diagnosis of this entity. We retrospectively reviewed the data from 26 cases in our institutions and additional 108 cases from the literature. ALK LBCL typically occurred in the lymph nodes of young and middle-aged, immunocompetent patients. The medium age was 35 years with a male to female ratio of 3.5:1. Vast majority of cases showed immunoblastic and/or plasmablastic morphology. All cases expressed ALK protein with a cytoplasmic granular pattern in most of them. Common B-cell markers (CD20, CD79a, and PAX5) were typically negative, but the tumor cells mostly expressed 2 B-cell transcriptional factors, BOB1 and OCT2. The 5-year overall survival (OS) was 34%, and the median survival was 1.83 years. In patients with stage III/IV disease, the 5-year OS was only 8%. Moreover, patients below 35 years of age had a significantly better OS than those aged 35 years or above.

Anaplastic lymphoma kinase-positive large B-cell lymphoma: Clinico-pathological study of 17 cases with review of literature

We retrospectively analysed 17 cases of anaplastic lymphoma kinase-positive large B-cell lymphoma (ALK+, LBCL) according to the morphological, immunohistochemical, molecular and clinical features, using which we intend to elucidate the clinicopathological characteristics of this rare entity. In this study, all cases de facto share common features that defined them as a single entity, and various characteristics may expand the spectrum. Among 15 cases, 60% followed an aggressive clinical course with advanced stage and high IPI scores; the median survival of these patients was only 8 months. An analysis showed that both the IPI score and the Ann Arbor stage were significant prognostic factors. Most patients received a chemotherapy regimen including CHOP, CHOEP, EPOCH, and CVAD, and some also underwent localized radiotherapy. However, ALK+, LBCL cases display a dismal clinical outcome and can only be cured with conventional chemotherapy protocols at the stage of localized disease. Novel front-line intensive chemotherapy regimens should therefore be evaluated in this group of patients.

Role of MYC in B Cell Lymphomagenesis

B cell lymphomas mainly arise from different developmental stages of B cells in germinal centers of secondary lymphoid tissue. There are a number of signaling pathways that affect the initiation and development of B cell lymphomagenesis. The functions of several key proteins that represent branching points of signaling networks are changed because of their aberrant expression, degradation, and/or accumulation, and those events determine the fate of the affected B cells. One of the most influential transcription factors, commonly associated with unfavorable prognosis for patients with B cell lymphoma, is nuclear phosphoprotein MYC. During B cell lymphomagenesis, oncogenic MYC variant is deregulated through various mechanisms, such as gene translocation, gene amplification, and epigenetic deregulation of its expression. Owing to alterations of downstream signaling cascades, MYC-overexpressing neoplastic B cells proliferate rapidly, avoid apoptosis, and become unresponsive to most conventional treatments. This review will summarize the roles of MYC in B cell development and oncogenesis, as well as its significance for current B cell lymphoma classification. We compared communication networks within transformed B cells in different lymphomas affected by overexpressed MYC and conducted a meta-analysis concerning the association of MYC with tumor prognosis in different patient populations.

ALK-driven tumors and targeted therapy: focus on crizotinib

Receptor tyrosine kinases have emerged as promising therapeutic targets for a diverse set of tumors. Overactivation of the tyrosine kinase anaplastic lymphoma kinase (ALK) has been reported in several types of malignancies such as anaplastic large cell lymphoma, inflammatory myofibroblastic tumor, neuroblastoma, and non-small-cell lung carcinoma. Further characterization of the molecular role of ALK has revealed an oncogenic signaling signature that results in tumor dependence on ALK. ALK-positive tumors display a different behavior than their ALK-negative counterparts; however, the specific role of ALK in some of these tumors remains to be elucidated. Although more studies are required to establish selective targeting of ALK as a definitive therapeutic option, initial trials have shown extraordinary results in the majority of cases.

Mechanistic insight into ALK receptor tyrosine kinase in human cancer biology

The burgeoning field of anaplastic lymphoma kinase (ALK) in cancer encompasses many cancer types, from very rare cancers to the more prevalent non-small-cell lung cancer (NSCLC). The common activation of ALK has led to the use of the ALK tyrosine kinase inhibitor (TKI) crizotinib in a range of patient populations and to the rapid development of second-generation drugs targeting ALK. In this Review, we discuss our current understanding of ALK function in human cancer and the implications for tumour treatment.

ALK-positive large B-cell lymphomas express a terminal B-cell differentiation program and activated STAT3 but lack MYC rearrangements

ALK-positive large B-cell lymphoma is an aggressive lymphoid neoplasm characterized by a monomorphic proliferation of immunoblast-like cells expressing a plasmablastic phenotype and carrying ALK rearrangements. MYC rearrangements are frequent in plasmablastic lymphomas, advanced plasma cell myelomas and a subgroup of diffuse large B-cell lymphomas, but their presence in ALK-positive large B-cell lymphomas is unknown. MYC expression is downregulated by BLIMP1, a master modulator of plasma cell differentiation. BLIMP1 and MYC are upregulated by STAT3, a signal transducer activated by ALK. To determine the role of BLIMP1, MYC and STAT3 in the pathogenesis of ALK-positive large B-cell lymphomas, we investigated MYC rearrangement and the expression of MYC, phosphorylated STAT3, BLIMP1, PAX5 and XBP1 in 12 ALK-positive large B-cell lymphomas. All cases expressed ALK with a granular cytoplasmic pattern. Nine cases had a split signal consistent with an ALK rearrangement. Three additional cases showed a deletion of the 5' or 3' end of the ALK probe consistent with cryptic translocation. PAX5 was virtually negative in all cases tested, whereas BLIMP1 was expressed in all tumors and XBP1 in 11 of 12. Phosphorylated STAT3 was observed in all cases with a strong and diffuse nuclear pattern. MYC rearrangements were not identified in any tumor, but MYC gains and amplification were detected in six cases and one case, respectively. MYC protein was expressed in all tumors independently of MYC gene alterations. These results indicate that ALK-positive large B-cell lymphomas express a complete plasmablastic differentiation program but, contrary to plasmablastic lymphomas, do not have MYC rearrangements. STAT3 is constantly activated and may be an alternative mechanism to promote MYC expression in these tumors. The relevance of the ALK/STAT3 pathway in the pathogenesis of ALK-positive large B-cell lymphomas may offer an attractive target for new therapies.

Understanding MYC-driven aggressive B-cell lymphomas: pathogenesis and classification

MYC is a potent oncogene initially identified as the target of the t(8;14)(q24;q32) chromosome translocation in Burkitt lymphoma. MYC gene alterations have been identified in other mature B-cell neoplasms that are usually associated with an aggressive clinical behavior. Most of these tumors originate in cells that do not normally express MYC protein. The oncogenic events leading to MYC up-regulation seem to overcome the inhibitory effect of physiological repressors such as BCL6 or BLIMP1. Aggressive lymphomas frequently carry additional oncogenic alterations that cooperate with MYC dysregulation, likely counteracting its proapoptotic function. The development of FISH probes and new reliable antibodies have facilitated the study of MYC gene alterations and protein expression in large series of patients, providing new clinical and biological perspectives regarding MYC dysregulation in aggressive lymphomas. MYC gene alterations in large B-cell lymphomas are frequently associated with BCL2 or BCL6 translocations conferring a very aggressive behavior. Conversely, MYC protein up-regulation may occur in tumors without apparent gene alterations, and its association with BCL2 overexpression also confers a poor prognosis. In this review, we integrate all of this new information and discuss perspectives, challenges, and open questions for the diagnosis and management of patients with MYC-driven aggressive B-cell lymphomas.

Understanding MYC-driven aggressive B-cell lymphomas: pathogenesis and classification

MYC is a potent oncogene initially identified as the target of the t(8;14)(q24;q32) chromosome translocation in Burkitt lymphoma. MYC gene alterations have been identified in other mature B-cell neoplasms that are usually associated with an aggressive clinical behavior. Most of these tumors originate in cells that do not normally express MYC protein. The oncogenic events leading to MYC up-regulation seem to overcome the inhibitory effect of physiological repressors such as BCL6 or BLIMP1. Aggressive lymphomas frequently carry additional oncogenic alterations that cooperate with MYC dysregulation, likely counteracting its proapoptotic function. The development of FISH probes and new reliable antibodies have facilitated the study of MYC gene alterations and protein expression in large series of patients, providing new clinical and biological perspectives regarding MYC dysregulation in aggressive lymphomas. MYC gene alterations in large B-cell lymphomas are frequently associated with BCL2 or BCL6 translocations conferring a very aggressive behavior. Conversely, MYC protein up-regulation may occur in tumors without apparent gene alterations, and its association with BCL2 overexpression also confers a poor prognosis. In this review, we integrate all of this new information and discuss perspectives, challenges, and open questions for the diagnosis and management of patients with MYC-driven aggressive B-cell lymphomas.

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.

ALK Signaling and Target Therapy in Anaplastic Large Cell Lymphoma

The discovery by Morris et al. (1994) of the genes contributing to the t(2;5)(p23;q35) translocation has laid the foundation for a molecular based recognition of anaplastic large cell lymphoma and highlighted the need for a further stratification of T-cell neoplasia. Likewise the detection of anaplastic lymphoma kinase (ALK) genetic lesions among many human cancers has defined unique subsets of cancer patients, providing new opportunities for innovative therapeutic interventions. The objective of this review is to appraise the molecular mechanisms driving ALK-mediated transformation, and to maintain the neoplastic phenotype. The understanding of these events will allow the design and implementation of novel tailored strategies for a well-defined subset of cancer patients.

Anaplastic lymphoma kinase-positive large B-cell lymphoma: an underrecognized aggressive lymphoma

Anaplastic lymphoma kinase-(ALK-) positive large B-cell lymphoma (ALK+ LBCL) is a rare, aggressive tumor characterized by an immunoblastic or plasmablastic morphologic appearance, expression of ALK, CD138, CD45, EMA, and often IgA by immunohistochemistry, and characteristic chromosomal translocations or rearrangements involving the ALK locus. The morphologic and immunophenotypic overlap of this tumor with other hematologic and nonhematologic malignancies may result in misdiagnosis. The tumor has been identified in both pediatric and adult populations and demonstrates a male predominance. Presentation is most often nodal, particularly cervical. No association with immunocompromise or geographic location has been recognized. The most common gene rearrangement is between clathrin and ALK (t(2;17)(p23;q23)), resulting in the CLTC-ALK chimeric protein, although other fusions have been described. Response to conventional chemotherapy is poor. The recent introduction of the small molecule ALK inhibitor, crizotinib, may provide a potential new therapeutic option for patients with this disease.

Large B-cell lymphomas with plasmablastic differentiation: a biological and therapeutic challenge

Plasmablastic differentiation can be found in a variety of large B-cell lymphomas, including plasmablastic lymphoma, ALK-positive large B-cell lymphoma, primary effusion lymphoma, large B-cell lymphoma arising in human herpesvirus-8 (HHV-8)-associated multicentric Castleman disease and diffuse large B-cell lymphoma (DLBCL) with partial plasmablastic phenotype. These tumors are characterized by acquisition of the transcriptional profile of plasma cells (with overexpression of PRDM1/Blimp1 and XBP1s, in concert with extinction of the B-cell differentiation program) by proliferating immunoblasts. This particular biological entity, i.e. large B-cell lymphoma with plasmablastic differentiation, is almost always associated with an aggressive clinical behavior. This review summarizes the current knowledge of the biological basis of plasmablastic differentiation in large B-cell lymphomas, the diagnostic borders with DLBCL and multiple myeloma, the associated adverse molecular events (with concomitant MYC, p53 and ALK alterations) and the potential therapeutic targets so far identified (including the unfolded protein response pathway). The highly aggressive nature of these lymphomas and the relative paucity of molecular data available highlight the need for deeper insights into the molecular pathogenesis of large B-cell lymphomas with plasmablastic differentiation in order to identify new and effective alternative treatments.

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.

Inhibition of anaplastic lymphoma kinase (ALK) activity provides a therapeutic approach for CLTC-ALK-positive human diffuse large B cell lymphomas

ALK positive diffuse large B-cell lymphomas (DLBCL) are a distinct lymphoma subtype associated with a poor outcome. Most of them feature a t(2;17) encoding a clathrin (CLTC)-ALK fusion protein. The contribution of deregulated ALK-activity in the pathogenesis and maintenance of these DLBCLs is not yet known. We established and characterized the first CLTC-ALK positive DLBCL cell line (LM1). LM1 formed tumors in NOD-SCID mice. The selective ALK inhibitor NVP-TAE684 inhibited growth of LM1 cells in vitro at nanomolar concentrations. NVP-TAE684 repressed ALK-activated signalling pathways and induced apoptosis of LM1 DLBCL cells. Inhibition of ALK-activity resulted in sustained tumor regression in the xenotransplant tumor model. These data indicate a role of CLTC-ALK in the maintenance of the malignant phenotype thereby providing a rationale therapeutic target for these otherwise refractory tumors.

Clathrin heavy chain gene fusions expressed in human cancers: analysis of cellular functions

Clathrin is a protein expressed ubiquitously that has important functions in membrane trafficking and mitosis. Two different gene fusions involving clathrin heavy chain (CHC) have been described in human cancers. These involve either anaplastic lymphoma kinase (ALK) or transcription factor binding to IGHM enhancer 3 (TFE3) and raise the possibility that altered clathrin function in cells expressing the fusion proteins could contribute to oncogenesis. In the present study, we tested the functions of CHC-ALK and CHC-TFE3 in endocytosis and mitosis. CHC-ALK is comparable to full-length CHC in both functions indicating that malignant transformation in cells expressing CHC-ALK is not because of any change in clathrin function. CHC-TFE3 is not functional in endocytosis, but can substitute for CHC in mitosis. CHC-TFE3 causes prolonged interphase that is attributed to the TFE3 portion of the protein. We also describe how CHC-TFE3 is a dimer. This suggests that clathrin's proposed role in intermicrotubule bridging can be fulfilled not only by trimers but also by dimers. Finally, this study shows that the membrane trafficking and mitotic functions of clathrin are independent and separable.

Suppression of STAT5A increases chemotherapeutic sensitivity in imatinib-resistant and imatinib-sensitive K562 cells

STAT proteins are cytoplasmic transcription factors that are involved in the regulation of numerous cellular activities such as cell growth, differentiation, and survival. In this study, we aimed to identify the expression pattern of STAT genes in imatinib-sensitive and -resistant K562 cells, and further, to reveal the effects of STAT5A siRNA knockdown on cell growth and apoptosis induction. The XTT cell proliferation assay showed that both sensitive and resistant K562 cells were sensitized to imatinib upon transfection with STAT5A siRNA. Caspase-3 enzyme activity was increased significantly in both cells. These results may open up new opportunities to overcome chemotherapeutic resistance in leukemia.

ALK-positive large B-cell lymphomas with cryptic SEC31A-ALK and NPM1-ALK fusions

We report 2 ALK-positive large B-cell lymphoma cases showing granular cytoplasmic and cytoplasmic/nuclear ALK immunostaining in which cryptic ALK rearrangements were identified by fluorescent in situ hybridization and molecular analysis. In the first case, the ALK-involving t(2;3)(p23;q27) masked the cryptic SEC31A-ALK fusion generated by an insertion of the 5' end of SEC31A (4q21) upstream of the 3' end of ALK. This rearrangement was associated with loss of the 5' end of ALK and duplication of SEC31A-ALK on der(20). In the second case with complex rearrangements of both chromosomes 2, a submicroscopic NPM1-ALK fusion created by insertion of the 3' end of ALK into the NPM1 locus was evidenced. Further studies of SEC31A-ALK showed that this variant fusion transforms IL3-dependent Ba/F3 cells to growth factor independence, and that the ALK inhibitor TAE-684 reduces cell proliferation and kinase activity of SEC31A-ALK and its downstream effectors ERK1/2, AKT, STAT3 and STAT5.

NF-kappaB/STAT3/PI3K signaling crosstalk in iMyc E mu B lymphoma

Background

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 iMyc^Eμ, readily develop B-cell lymphoma. To study the mechanism of Myc-induced lymphoma, we analyzed signaling pathways in lymphoblastic B-cell lymphomas (LBLs) from iMyc^Eμ mice, and an LBL-derived cell line, iMyc^Eμ-1.

Results

Nuclear factor-κB (NF-κB) and signal transducer and activator of transcription 3 (STAT3) were constitutively activated in iMyc^Eμ 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 iMyc^Eμ-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 iMyc^Eμ-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 iMyc^Eμ-1 cells also showed constitutive AKT phosphorylation. Blocking AKT activation by inhibiting PI3K reduced iMyc^Eμ-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 iMyc^Eμ-1 cell proliferation, suggesting that these signaling pathways converge.

Conclusions

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 iMyc^Eμ B-cell lymphomas.

Frequent STAT3 activation is associated with Mcl-1 expression in nasal NK-cell lymphoma

Nasal natural killer (NK)-cell lymphoma was resistant to various antitumor agents. Although high expression of p-glycoprotein has been reported, other molecular mechanism of the chemo-resistance is largely unknown. Activation of STAT3 and expression of major apoptosis-related proteins Bcl-2, Bcl-x, and Mcl-1 were analyzed by immunohistochemistry. Effects of STAT3 inhibitor AG490 on NK-YS cell line were analyzed by Western blotting and flow cytometric apoptosis assay. STAT3 was activated in six of the nine nasal NK-cell lymphomas (67%). In contrast, STAT3 activation was detected in 35% of diffuse large B-cell lymphoma (DLBCL) and in 10% of follicular lymphoma (FL). Frequent activation of STAT3 was significantly correlated with Mcl-1 expression in nasal NK-cell lymphoma, i.e., Mcl-1 was positive in five of six STAT3-active cases and negative in all three STAT3-inactive ones. In DLBCL, not only six out of seven STAT3-active cases (86%) but also eight out of thirteen STAT3-inactive cases (62%) were positive for Mcl-1 expression. Latent membrane protein-1 was positive in four nasal NK-cell lymphomas, among which three cases showed intermediate STAT3 activation. Inhibition of STAT3 activation by JAK inhibitor AG490 decreased Mcl-1 expression and induced apoptosis in STAT3-active NK-YS cells. Serum starvation rather increased the Mcl-1 level in NK-YS cells, and this effect was also canceled by AG490. These results suggest that activation of STAT3-Mcl-1 axis may play a role in the chemotherapy resistance of nasal NK-cell lymphoma. The pathway may be one of the future therapeutic targets of this intractable disease.

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

Background

Anaplastic lymphoma kinase-positive diffuse large B-cell lymphoma (ALK-DLBCL) is a rare lymphoma with several clinicopathological differences from ALK-positive anaplastic large cell lymphoma (ALCL). The latest WHO classification of lymphomas recognizes ALK-DLBCL as a separate entity.

Methods

A comprehensive comparison was made between the clinical and pathological features of the 4 cases reported and those found in an extensive literature search using MEDLINE through December 2008.

Results

In our series, three cases were adults and one was pediatric. Two cases had primary extranodal disease (multifocal bone and right nasal fossa). Stages were I (n = 1), II (n = 1), III (n = 1) and IV (n = 1). Two cases had increased LDH levels and three reported B symptoms. IPI scores were 0 (n = 1), 2 (n = 2) and 3 (n = 1). All cases exhibited plasmablastic morphology. By immunohistochemistry, cases were positive for cytoplasmic ALK, MUM1, CD45, and EMA; they marked negative for CD3, CD30 and CD20. Studies for EBV and HHV-8 were negative. The survival for the patients with stage I, II, III and IV were 13, 62, 72 and 11 months, respectively.

Conclusion

ALK-DLBCL is a distinct variant of DLBCL with plasmacytic differentiation, which is characterized by a bimodal age incidence curve, primarily nodal involvement, plasmablastic morphology, lack of expression of CD20, aggressive behavior and poor response to standard therapies, although some cases can have prolonged survival as the cases reported in this study. ALK-DLBCL does not seem associated to immunosuppression or the presence of EBV or HHV8. Further prospective studies are needed to optimize therapies for this entity.