Overexpression of Syk tyrosine kinase in peripheral T-cell lymphomas

Spleen tyrosine kinase contributes to acute renal allograft rejection in the rat

Kidney allografts induce strong T-cell and antibody responses which mediate acute rejection. Spleen tyrosine kinase (Syk) is expressed by most leucocytes, except mature T cells, and is involved in intracellular signalling following activation of the Fcγ-receptor, B-cell receptor and some integrins. A role for Syk signalling has been established in antibody-dependent native kidney disease, but little is known of Syk in acute renal allograft rejection. Sprague-Dawley rats underwent bilateral nephrectomy and received an orthotopic Wistar renal allograft. Recipient rats were treated with a Syk inhibitor (CC0482417, 30 mg/kg/bid), or vehicle, from 1 h before surgery until being killed 5 days later. Vehicle-treated recipients developed severe allograft failure with marked histologic damage in association with dense leucocyte infiltration (T cells, macrophages, neutrophils and NK cells) and deposition of IgM, IgG and C3. Immunostaining identified Syk expression by many infiltrating leucocytes. CC0482417 treatment significantly improved allograft function and reduced histologic damage, although allograft injury was still clearly evident. CC0482417 failed to prevent T-cell infiltration and activation within the allograft. However, CC0482417 significantly attenuated acute tubular necrosis, infiltration of macrophages and neutrophils and thrombosis of peritubular capillaries. In conclusion, this study identifies a role for Syk in acute renal allograft rejection. Syk inhibition may be a useful addition to T-cell-based immunotherapy in renal transplantation.

Pathogenetic and diagnostic significance of microRNA deregulation in peripheral T-cell lymphoma not otherwise specified

Peripheral T-cell lymphomas not otherwise specified (PTCLs/NOS) are rare and aggressive tumours whose molecular pathogenesis and diagnosis are still challenging. The microRNA (miRNA) profile of 23 PTCLs/NOS was generated and compared with that of normal T-lymphocytes (CD4+, CD8+, naive, activated). The differentially expressed miRNA signature was compared with the gene expression profile (GEP) of the same neoplasms. The obtained gene patterns were tested in an independent cohort of PTCLs/NOS. The miRNA profile of PTCLs/NOS then was compared with that of 10 angioimmunoblastic T-cell lymphomas (AITLs), 6 anaplastic large-cell lymphomas (ALCLs)/ALK+ and 6 ALCLs/ALK−. Differentially expressed miRNAs were validated in an independent set of 20 PTCLs/NOS, 20 AITLs, 19 ALCLs/ALK− and 15 ALCLs/ALK+. Two hundred and thirty-six miRNAs were found to differentiate PTCLs/NOS from activated T-lymphocytes. To assess which miRNAs impacted on GEP, a multistep analysis was performed, which identified all miRNAs inversely correlated to different potential target genes. One of the most discriminant miRNAs was selected and its expression was found to affect the global GEP of the tumours. Moreover, two sets of miRNAs were identified distinguishing PTCL/NOS from AITL and ALCL/ALK−, respectively. The diagnostic accuracy of this tool was very high (83.54%) and its prognostic value validated.

Calling in SYK: SYK's dual role as a tumor promoter and tumor suppressor in cancer

SYK (spleen tyrosine kinase) is well-characterized in the immune system as an essential enzyme required for signaling through multiple classes of immune recognition receptors. As a modulator of tumorigenesis, SYK has a bit of a schizophrenic reputation, acting in some cells as a tumor promoter and in others as a tumor suppressor. In many hematopoietic malignancies, SYK provides an important survival function and its inhibition or silencing frequently leads to apoptosis. In cancers of non-immune cells, SYK provides a pro-survival signal, but can also suppress tumorigenesis by restricting epithelial-mesenchymal transition, enhancing cell-cell interactions and inhibiting migration.

Syk interacts with and phosphorylates nucleolin to stabilize Bcl-x(L) mRNA and promote cell survival

The Syk protein tyrosine kinase, a well-characterized regulator of immune cell function, plays an increasingly recognized role in tumorigenesis as a promoter of cell survival in both hematological and nonhematological malignancies. We show here that the expression of Syk in MCF7 or MDA-MB-231 breast cancer cells or in DG75 B-lymphoma cells protects cells from apoptosis induced by oxidative or genotoxic stress by stabilizing the mRNA for Bcl-x(L), an antiapoptotic protein. Syk binds robustly to nucleolin and phosphorylates it on tyrosine, enhancing its ability to bind the Bcl-x(L) mRNA. Consequently, reducing the level of nucleolin by RNA interference attenuates the ability of Syk to protect cells from stress-induced cell death.

Angioimmunoblastic T-cell lymphoma in Taiwan shows a frequent gain of ITK gene

Angioimmunoblastic T-cell lymphoma (AITL) is an aggressive peripheral T-cell lymphoma (PTCL) of follicular helper T-cell origin and is rare in Taiwan. There are overlapping features of AITL and peripheral T-cell lymphoma with a follicular growth pattern (PTCL-F). Around one fifth of PTCL-F exhibits t(5;9)(q33;q22)/ITK-SYK chromosomal translocation, which is essentially absent in AITL. We retrospectively investigated 35 cases of AITL from Taiwan with histopathology review, immunohistochemistry, in situ hybridization for Epstein-Barr virus (EBV) and fluorescence in situ hybridization (FISH) for t(5;9)(q33;q22)/ITK-SYK and correlated the results with overall survival. Twenty-six cases of not otherwise specified PTCL (PTCL-NOS) were also examined by FISH for comparison. Most AITL patients were male (69%) and elderly (median age at 67 years) with frequent bone marrow involvement (53%), high Ann Arbor stages (77%), and elevated serum lactate dehydrogenase (68%). Most cases (80%) showed a typical CD4+/CD8- phenotype and in 90% cases there were scattered EBV-positive B-cells (less than 10% cells). None of these cases showed t(5;9)(q33;q22)/ITK-SYK translocation by FISH. Gain of ITK and SYK gene was identified in 38% and 14% tumors, respectively, but both were not associated with overall survival. Performance status < 2 was associated with a better outcome but not the other clinicopathological factors. All PTCL-NOS cases were negative for ITK-SYK translocation with similar rates (38% and 12%, respectively) of gains at ITK and SYK loci as that of AITL. In this so far the largest series of AITL from Taiwan, we reported the clinicopathological features and FISH findings on ITK and SYK genes. We confirmed the absence of t(5;9)(q33;q22)/ITK-SYK translocation, which may serve as an additional differential diagnostic tool from PTCL-F when present. PTCL-NOS shared a similar pattern of ITK and SYK gains with AITL. More studies are warranted to elucidate the roles of SYK and ITK and other genes in the lymphomagenesis of AITL in Taiwan.

Getting Syk: spleen tyrosine kinase as a therapeutic target

Spleen tyrosine kinase (Syk) is a cytoplasmic protein tyrosine kinase well known for its ability to couple immune cell receptors to intracellular signaling pathways that regulate cellular responses to extracellular antigens and antigen-immunoglobulin (Ig) complexes of particular importance to the initiation of inflammatory responses. Thus, Syk is an attractive target for therapeutic kinase inhibitors designed to ameliorate the symptoms and consequences of acute and chronic inflammation. Its more recently recognized role as a promoter of cell survival in numerous cancer cell types ranging from leukemia to retinoblastoma has attracted considerable interest as a target for a new generation of anticancer drugs. This review discusses the biological processes in which Syk participates that have made this kinase such a compelling drug target.

Hepatosplenic γδ T-cell lymphoma: an overview

Peripheral T-cell lymphomas are a heterogeneous group of lymphoid malignancies. Among these, hepatosplenic γδ T-cell lymphoma (HTCL) represents an aggressive and treatment-resistant subgroup for which new avenues of treatment are critically needed. HTCL is characterized by primary extranodal distribution of the malignant cells with typical intrasinusoidal infiltration of the liver, spleen, and bone marrow, which results in hepatosplenomegaly and peripheral blood cytopenias. Another characteristic feature is the expression of γδ T-cell receptors. HTCL exhibits a rapid progressive course and an extremely poor response to currently known therapeutic strategies, with a 5-year overall survival rate of only 7%. In this review, we discuss the clinical, pathologic, and molecular characteristics of this disease, along with the challenges that are associated with its diagnosis and treatment.

How I treat the peripheral T-cell lymphomas

The peripheral T-cell lymphomas (PTCLs) encompass a heterogeneous group of diseases that have generally been associated with poor prognosis. The most common PTCLs, peripheral T-cell lymphoma, not otherwise specified, angioimmunoblastic T-cell lymphoma, and anaplastic lymphoma kinase (ALK)-negative anaplastic large cell lymphoma (ALK-negative), despite their unique presentations and histologies, are currently treated similarly. Here we discuss our general approach to the treatment of the most common PTCLs. Based on the best data currently available, which include retrospective analyses and phase 2 prospective studies, our approach has involved cyclophosphamide, doxorubicin, vincristine, prednisone-based therapy followed by consolidation in first remission with autologous stem cell transplant. This treatment strategy likely improves the outcome for patients compared with historical series; however, progression-free survival rates remain disappointing, ranging from 40% to 50%. This is currently an exciting time in the treatment of PTCL due to the advent of recently approved drugs as well as new targeted agents currently under investigation. In addition, gene expression profiling is allowing for a better understanding of underlying disease biology, improved diagnostic accuracy, and prognostication in PTCL. As a result, over the next few years, we expect a significant shift in our management of these diseases with a move toward more individualized therapy leading to improved outcomes.

T-cell receptor signaling in peripheral T-cell lymphoma - a review of patterns of alterations in a central growth regulatory pathway

T-cell receptor (TCR) signaling is pivotal in T-cell development and function. In peripheral T-cell lymphomas/leukemias (PTCL/L), histogenesis, transforming events, epidemiology, and clinical presentation are also closely linked to TCR-mediated influences. After reviewing the physiology of normal TCR signaling and cellular responses, we describe here the association of subgroups of PTCL/L with specific patterns of TCR activation as relevant tumor-initiating and/or tumor-sustaining programs. We identify PTCL/L with a functionally intact TCR machinery in which stimulation is possibly incited by exogenous antigens or autoantigens. Distinct from these are tumors with autonomous oncogenic signaling by dysregulated TCR components uncoupled from extrinsic receptor input. A further subset is characterized by transforming events that activate molecules acting as substitutes for TCR signaling, but triggering similar downstream cascades. We finally discuss the consequences of such a functional model for TCR-targeted therapeutic strategies including those that are being tested in the clinic and those that still require further development.

Treatment of peripheral T-cell lymphoma: are we data driven or driving the data?

Peripheral T-cell lymphomas (PTCL) are a group of uncommon and heterogeneous malignancies arising from a postthymic or mature T-lymphocyte. The treatment of PTCL remains a challenging endeavor. Compared with the more common aggressive B-cell lymphomas, more patients with PTCL will be refractory to initial therapy and those who achieve responses often will have shorter progression-free survival. Despite retrospective data that suggest that anthracycline-based multiagent chemotherapy regimens may not provide a benefit compared with nonanthracycline regimens, nonanthracycline-based regimens, with the notable exception of L-asparaginase regimens for extranodal NK/T-cell lymphoma, have been disappointing so far. Based on phase II evidence and subset analyses available, we believe that the addition of etoposide to standard regimens and consolidation of first remissions with autologous stem cell transplantation (autoSCT) provides the best outcome in patients with PTCL and currently use CHOEP followed by ASCT for eligible patients with the common PTCL subtype: PTCL-NOS, AITL, and ALK negative ALCL. For those with ALK-positive ALCL standard CHOP or CHOEP is appropriate with consideration of ASCT only for those with high-risk disease. Other strategies to incorporate additional agents, such as with dose-adjusted EPOCH or sequential CHOP-ICE regimens are logical options; however, they lack the supporting literature of CHOEP. Whereas the above recommendation is our current off-protocol approach, with the possible exception of low risk ALK positive ALCL, none of these choices is supported by strong enough data to supplant a well-conceived clinical trial as the truly preferred strategy in PTCL. The novel agents, romidepsin, pralatrexate, and brentuximab vedotin, are currently approved in the relapsed/refractory setting. These agents are being studied as additions or substitutions for other agents in up-front multiagent chemotherapy regimens. In the relapsed/refractory setting, both pralatrexate and romidepsin remain well-studied choices with some patients achieving a response with durability. Clinical trials of new agents in PTCL continue to be a valuable option and an important part of routine patient management as progressive disease often is seen. Lastly, we believe patients with relapsed/refractory PTCL should be considered for allogeneic stem cell transplantation if a suitable response is demonstrated and a willing donor is available.

Molecular diagnostics of T-cell lymphoproliferative disorders

T-cell neoplasms include both mature T-cell leukemias and lymphomas and immature proliferations of precursor T cells. Molecular laboratories routinely assay suspected T-cell proliferations for evidence of clonality. In addition, some T-cell neoplasms are characterized by recurrent structural abnormalities that can be readily identified by such techniques as fluorescence in situ hybridization. New massively parallel sequencing technologies have led to the identification of numerous recurrent gene mutations in T-cell neoplasms. These findings are reviewed. As new technologies become implemented in molecular diagnostic laboratories and as targeted therapies are developed, it is anticipated that more extensive genomic characterization of T-cell neoplasms will be routinely performed in the future.

Premature terminal differentiation protects from deregulated lymphocyte activation by ITK-Syk

The development of hematopoietic neoplasms is often associated with mutations, altered gene expression or chromosomal translocations. Recently, the t(5, 9)(q33;q22) translocation was found in a subset of peripheral T cell lymphomas and was shown to result in an IL-2-inducible kinase-spleen tyrosine kinase (ITK-Syk) fusion transcript. In this study, we show that T cell-specific expression of the ITK-Syk oncogene in mice leads to an early onset and aggressive polyclonal T cell lymphoproliferation with concomitant B cell expansion and systemic inflammation by 7-9 wk of age. Because this phenotype is strikingly different from previous work showing that ITK-Syk expression causes clonal T cell lymphoma by 20-27 wk of age, we investigated the underlying molecular mechanism in more detail. We show that the reason for the severe phenotype is the lack of B-lymphocyte-induced maturation protein-1 (Blimp-1) induction by low ITK-Syk expression. In contrast, high ITK-Syk oncogene expression induces terminal T cell differentiation in the thymus by activating Blimp-1, thereby leading to elimination of oncogene-expressing cells early in development. Our data suggest that terminal differentiation is an important mechanism to prevent oncogene-expressing cells from malignant transformation, as high ITK-Syk oncogene activity induces cell elimination. Accordingly, for transformation, a specific amount of oncogene is required, or alternatively, the induction of terminal differentiation is defective.

Misregulation of pre-mRNA alternative splicing in cancer

Alternative splicing of mRNA precursors enables one gene to produce multiple protein isoforms with differing functions. Under normal conditions, this mechanism is tightly regulated in order for the human genome to generate proteomic diversity sufficient for the functional requirements of complex tissues. When deregulated, however, cancer cells take advantage of this mechanism to produce aberrant proteins with added, deleted, or altered functional domains that contribute to tumorigenesis. Here, we discuss aspects of alternative splicing misregulation in cancer, focusing on splicing events affected by deregulation of regulatory splicing factors and also recent studies identifying mutated components of the splicing machinery.

SIGNIFICANCE

An increasing body of evidence indicates that aberrant splicing of mRNA precursors leads to production of aberrant proteins that contribute to tumorigenesis. Recent studies show that alterations in cellular concentrations of regulatory splicing factors and mutations in components of the core splicing machinery provide major mechanisms of misregulation of mRNA splicing in cancer. A better understanding of this misregulation will potentially reveal a group of novel drug targets for therapeutic intervention.

CD30-positive peripheral T-cell lymphomas share molecular and phenotypic features

Peripheral T-cell lymphoma, not otherwise specified is a heterogeneous group of aggressive neoplasms with indistinct borders. By gene expression profiling we previously reported unsupervised clusters of peripheral T-cell lymphomas, not otherwise specified correlating with CD30 expression. In this work we extended the analysis of peripheral T-cell lymphoma molecular profiles to prototypical CD30(+) peripheral T-cell lymphomas (anaplastic large cell lymphomas), and validated mRNA expression profiles at the protein level. Existing transcriptomic datasets from peripheral T-cell lymphomas, not otherwise specified and anaplastic large cell lymphomas were reanalyzed. Twenty-one markers were selected for immunohistochemical validation on 80 peripheral T-cell lymphoma samples (not otherwise specified, CD30(+) and CD30(-); anaplastic large cell lymphomas, ALK(+) and ALK(-)), and differences between subgroups were assessed. Clinical follow-up was recorded. Compared to CD30(-) tumors, CD30(+) peripheral T-cell lymphomas, not otherwise specified were significantly enriched in ALK(-) anaplastic large cell lymphoma-related genes. By immunohistochemistry, CD30(+) peripheral T-cell lymphomas, not otherwise specified differed significantly from CD30(-) samples [down-regulated expression of T-cell receptor-associated proximal tyrosine kinases (Lck, Fyn, Itk) and of proteins involved in T-cell differentiation/activation (CD69, ICOS, CD52, NFATc2); upregulation of JunB and MUM1], while overlapping with anaplastic large cell lymphomas. CD30(-) peripheral T-cell lymphomas, not otherwise specified tended to have an inferior clinical outcome compared to the CD30(+) subgroups. In conclusion, we show molecular and phenotypic features common to CD30(+) peripheral T-cell lymphomas, and significant differences between CD30(-) and CD30(+) peripheral T-cell lymphomas, not otherwise specified, suggesting that CD30 expression might delineate two biologically distinct subgroups.

Loss of TCR-beta F1 and/or EZRIN expression is associated with unfavorable prognosis in nodal peripheral T-cell lymphomas

Nodal peripheral T-cell lymphoma (nodal PTCL) has an unfavorable prognosis, and specific pathogenic alterations have not been fully identified. The biological and clinical relevance of the expression of CD30/T-cell receptor (TCR) genes is a topic under active investigation. One-hundred and ninety-three consecutive nodal PTCLs (89 angioimmunoblastic T-cell lymphomas (AITL) and 104 PTCL-unspecified (PTCL-not otherwise specified (NOS)) cases) were analyzed for the immunohistochemical expression of 19 molecules, involving TCR/CD30 pathways and the associations with standard prognostic indices. Mutually exclusive expression was found between CD3 and TCR-beta F1 with CD30 expression. Taking all PTCL cases together, logistic regression identified a biological score (BS) including TCR molecules (TCR-beta F1 and EZRIN) that separates two subgroups of patients with a median survival of 34.57 and 5.20 months (P<0.001). Multivariate analysis identified BS and the prognostic index for PTCL (PIT) score as independent prognostic factors. This BS maintained its significance in multivariate analysis only for the PTCL-NOS subgroup of tumors. In AITL cases, only a high level of ki67 expression was related to prognosis. A BS including molecules involved in the TCR signaling pathway proved to be an independent prognostic factor of poor outcome in a multivariate analysis, specifically in PTCL-NOS patients. Nevertheless, validation in an independent series of homogeneously treated PTCL patients is required to confirm these data.

Targeting the SYK-BTK axis for the treatment of immunological and hematological disorders: recent progress and therapeutic perspectives

Spleen Tyrosine Kinase (SYK) and Bruton's Tyrosine Kinase (BTK) are non-receptor cytoplasmic tyrosine kinases that are primarily expressed in cells of hematopoietic lineage. Both are key mediators in coupling activated immunoreceptors to downstream signaling events that affect diverse biological functions, from cellular proliferation, differentiation and adhesion to innate and adaptive immune responses. As such, pharmacological inhibitors of SYK or BTK are being actively pursued as potential immunomodulatory agents for the treatment of autoimmune and inflammatory disorders. Deregulation of SYK or BTK activity has also been implicated in certain hematological malignancies. To date, from a clinical perspective, pharmacological inhibition of SYK activity has demonstrated encouraging efficacy in patients with rheumatoid arthritis (RA), while patients with relapsed or refractory chronic lymphocytic leukemia (CLL)/small lymphocytic lymphoma (SLL) have benefited from covalent inhibitors of BTK in early clinical studies. Here, we review and discuss recent insights into the emerging role of the SYK-BTK axis in innate immune cell function as well as in the maintenance of survival and homing signals for tumor cell progression. The current progress on the clinical development of SYK and BTK inhibitors is also highlighted.

More epigenetic hits than meets the eye: microRNAs and genes associated with the tumorigenesis of retinoblastoma

Retinoblastoma (RB), a childhood neoplasia of the retinoblasts, can occur unilaterally or bilaterally, with one or multiple foci per eye. RB is associated with somatic loss of function of both alleles of the tumor suppressor gene RB1. Hereditary forms emerge due to germline loss of function mutations in RB1 alleles. RB has long been the prototypic “model” cancer ever since Knudson's “two-hit” hypothesis. However, a simple two-hit model for RB is challenged by an increasing number of studies documenting additional hits that contribute to RB development. Here we review the genetics and epigenetics of RB with a focus on the role of small non-coding RNAs (microRNAs) and on novel findings indicating the relevance of DNA methylation in the development and prognosis of this neoplasia. Studies point to an elaborated landscape of genetic and epigenetic complexity, in which a number of events and pahtways play crucial roles in the origin and prognosis of RB. These include roles for microRNAs, inprinted loci, and parent-of-origin contributions to RB1 regulation and RB progression. This complexity is also manifested in the structure of the RB1 locus itself: it includes numerous repetitive DNA segments and retrotransposon insertion elements, some of which are actively transcribed from the RB1 locus. Altogether, we conclude that RB1 loss of function represents the tip of an iceberg of events that determine RB development, progression, severity, and disease risk. Comprehensive assessment of personalized RB risk will require genetic and epigenetic evaluations beyond RB1 protein coding sequences.

Trivanillic polyphenols with anticancer cytostatic effects through the targeting of multiple kinases and intracellular Ca2+ release

Cancer cells exhibit de-regulation of multiple cellular signalling pathways and treatments of various types of cancers with polyphenols are promising. We recently reported the synthesis of a series of 33 novel divanillic and trivanillic polyphenols that displayed anticancer activity, at least in vitro, through inhibiting various kinases. This study revealed that minor chemical modifications of a trivanillate scaffold could convert cytotoxic compounds into cytostatic ones. Compound 13c, a tri-chloro derivative of trivanillic ester, displayed marked inhibitory activities against FGF-, VEGF-, EGF- and Src-related kinases, all of which are implicated not only in angiogenesis but also in the biological aggressiveness of various cancer types. The pan-anti-kinase activity of 13c occurs at less than one-tenth of its mean IC₅₀in vitro growth inhibitory concentrations towards a panel of 12 cancer cell lines. Of the 26 kinases for which 13c inhibited their activity by >75%, eight (Yes, Fyn, FGF-R1, EGFR, Btk, Mink, Ret and Itk) are implicated in control of the actin cytoskeleton organization to varying degrees. Compound 13c accordingly impaired the typical organization of the actin cytoskeleton in human U373 glioblastoma cells. The pan-anti-kinase activity and actin cytoskeleton organization impairment provoked by 13c concomitantly occurs with calcium homeostasis impairment but without provoking MDR phenotype activation. All of these anticancer properties enabled 13c to confer therapeutic benefits in vivo in a mouse melanoma pseudometastatic lung model. These data argue in favour of further chemically modifying trivanillates to produce novel and potent anticancer drugs.

Follicular T-cell lymphoma: a member of an emerging family of follicular helper T-cell derived T-cell lymphomas

Unlike B-cell lymphomas, where knowledge of normal B-cell origin and differentiation has greatly contributed to their classification, the current classification of peripheral T-cell lymphomas is limited by a lack of understanding of their cellular origin. In the current World Health Organization classification of lymphomas, follicular T-cell lymphoma was formally recognized as a morphologic variant of peripheral T-cell lymphoma, not otherwise specified. There is growing evidence, however, that follicular T-cell lymphoma may be a unique clinicopathologic entity based on its morphologic features and derivation from follicular helper T-cells. In addition, there are abundant recent data supporting the concept that follicular helper T-cells can give rise to other types of T-cell lymphoma, including angioimmunoblastic T-cell lymphoma, primary cutaneous CD4+ small/medium T-cell lymphoma, and a subset of neoplasms, in addition to follicular T-cell lymphoma, currently classified as peripheral T-cell lymphoma, not otherwise specified. In this review, we focus primarily on the clinicopathologic, immunophenotypic, and molecular features of follicular T-cell lymphoma and discuss its potential relationship with other types of T-cell lymphoma thought to be derived from follicular helper T-cells.

A peptide-based biosensor assay to detect intracellular Syk kinase activation and inhibition

Spleen tyrosine kinase (Syk) has been implicated in a number of pathologies including cancer and rheumatoid arthritis and thus has been pursued as a novel therapeutic target. Because of the complex relationship between Syk's auto- and other internal phosphorylation sites, scaffolding proteins, enzymatic activation state and sites of phosphorylation on its known substrates, the role of Syk's activity in these diseases has not been completely clear. To approach such analyses, we developed a Syk-specific artificial peptide biosensor (SAStide) to use in a cell-based assay for direct detection of intracellular Syk activity and inhibition in response to physiologically relevant stimuli in both laboratory cell lines and primary splenic B cells. This peptide contains a sequence derived from known Syk substrate preference motifs linked to a cell permeable peptide, resulting in a biosensor that is phosphorylated in live cells in a Syk-dependent manner, thus serving as a reporter of Syk catalytic activity in intact cells. Because the assay is compatible with live, primary cells and can report pharmacodynamics for drug action on an intended target, this methodology could be used to facilitate a better understanding of Syk's function and the effect of its inhibition in disease.

Genome-wide analysis reveals recurrent structural abnormalities of TP63 and other p53-related genes in peripheral T-cell lymphomas

Peripheral T-cell lymphomas (PTCLs) are aggressive malignancies of mature T lymphocytes with 5-year overall survival rates of only ∼ 35%. Improvement in outcomes has been stymied by poor understanding of the genetics and molecular pathogenesis of PTCL, with a resulting paucity of molecular targets for therapy. We developed bioinformatic tools to identify chromosomal rearrangements using genome-wide, next-generation sequencing analysis of mate-pair DNA libraries and applied these tools to 16 PTCL patient tissue samples and 6 PTCL cell lines. Thirteen recurrent abnormalities were identified, of which 5 involved p53-related genes (TP53, TP63, CDKN2A, WWOX, and ANKRD11). Among these abnormalities were novel TP63 rearrangements encoding fusion proteins homologous to ΔNp63, a dominant-negative p63 isoform that inhibits the p53 pathway. TP63 rearrangements were seen in 11 (5.8%) of 190 PTCLs and were associated with inferior overall survival; they also were detected in 2 (1.2%) of 164 diffuse large B-cell lymphomas. As TP53 mutations are rare in PTCL compared with other malignancies, our findings suggest that a constellation of alternate genetic abnormalities may contribute to disruption of p53-associated tumor suppressor function in PTCL.

Genetic alterations in systemic nodal and extranodal non-cutaneous lymphomas derived from mature T cells and natural killer cells

Mature (peripheral) T-cell and natural killer (NK)-cell lymphomas comprise a series of rather different neoplasms. Based on morphologic, immunophenotypic, genetic, and clinical data, the World Health Organization classification recognizes more than 20 entities or provisional entities. The variable clinical presentations, the objective recognition and pathological stratification, the difficulties regarding treatment, and the hardly predictable response to therapy indicate that the management of these entities requires novel tools. In contrast to B-cell lymphomas or precursor T-cell neoplasms, few recurrent translocations have been identified so far in T-cell non-Hodgkin's and NK-cell lymphomas. Additionally, some of the entities recognized by the World Health Organization classification are very rare and very scarce molecular data are available for T-cell lymphomas. Here, we have reviewed published reports focusing on the genetic lesions and gene expression profiling underlying systemic nodal and extranodal non-cutaneous mature T-cell and NK-cell lymphomas. We also provide a summary of new agents in clinical development and outline some future directions.

Enforced expression of Lin28b leads to impaired T-cell development, release of inflammatory cytokines, and peripheral T-cell lymphoma

LIN28A and LIN28B, the mammalian homologs of lin-28, are implicated in malignant transformation in part because of their ability to promote degradation of the let-7 family of miRs. In the present study, we show that overexpression of Lin28b in vivo leads to an aggressive peripheral T-cell lymphoma (PTCL) characterized by widespread infiltration of parenchymal organs with malignant CD4(+) cells. Similar to patients with PTCL, Lin28b-transgenic mice show signs of inflammation such as eosinophilia, increased C-reactive protein, release of inflammatory cytokines, and pleural effusion. The PTCLs that develop in Lin28b mice are derived from activated T cells and show decreased let-7 expression, increased Il6 expression, activation of NF-κB, and infiltration of B cells, all resulting in an inflammatory microenvironment. In addition, LIN28B is overexpressed 7.5-fold in PTCL patient samples compared with activated CD4(+) cells. The results of the present study demonstrate for the first time that Lin28b can transform primary cells in vivo, identify a previously unsuspected link between Lin28b and PTCL, and provide a unique animal model for the study of PTCL biology and therapy.

Clinicopathologic analysis of peripheral T-cell lymphoma, follicular variant, and comparison with angioimmunoblastic T-cell lymphoma: Bcl-6 expression might affect progression between these disorders

We examined clinicopathologic findings in 17 cases of peripheral T-cell lymphoma, follicular variant (f-PTCL), and compared these findings with angioimmunoblastic T-cell lymphoma (AITL) to determine whether they were identical to the spectrum of changes seen in AITL and how each of the findings in f-PTCL were related to the characteristics of AITL. Almost all f-PTCL cases showed pathologic characteristics of AITL and immunohistochemical positivities in lymphoma cells for CD4, CD10, Bcl-6, PD-1, and CXCL13. Except for pathologic characteristics, clinicopathologic findings in f-PTCL had few significant differences from AITL. The positive rate for Bcl-6 expression in neoplastic cells was significantly associated with the frequency of polymorphic infiltrates, vascular proliferation, B-immunoblasts, clear cells, Epstein-Barr virus-positive lymphocytes, hepatosplenomegaly, and skin rash. Our study confirmed the continuity between f-PTCL and AITL. Moreover, Bcl-6 expression in f-PTCL was statistically associated with the characteristics of AITL.

Molecular features of hepatosplenic T-cell lymphoma unravels potential novel therapeutic targets

The pathogenesis of hepatosplenic T-cell lymphoma (HSTL), a rare entity mostly derived from γδ T cells and usually with a fatal outcome, remains largely unknown. In this study, HSTL samples (7γδ and 2αβ) and the DERL2 HSTL cell line were subjected to combined gene-expression profiling and array-based comparative genomic hybridization. Compared with other T-cell lymphomas, HSTL had a distinct molecular signature irrespective of TCR cell lineage. Compared with peripheral T-cell lymphoma, not otherwise specified and normal γδ T cells, HSTL overexpressed genes encoding NK-cell-associated molecules, oncogenes (FOS and VAV3), the sphingosine-1-phosphatase receptor 5 involved in cell trafficking, and the tyrosine kinase SYK, whereas the tumor-suppressor gene AIM1 (absent in melanoma 1) was among the most down-expressed. We found highly methylated CpG islands of AIM1 in DERL2 cells, and decitabine treatment induced a significant increase in AIM1 transcripts. Syk was present in HSTL cells and DERL2 cells contained phosphorylated Syk and were sensitive to a Syk inhibitor in vitro. Genomic profiles confirmed recurrent isochromosome 7q (n = 6/9) without alterations at the SYK and AIM1 loci. Our results identify a distinct molecular signature for HSTL and highlight oncogenic pathways that offer rationale for exploring new therapeutic options such as Syk inhibitors and demethylating agents.

Clinical significance of elevated spleen tyrosine kinase expression in nasopharyngeal carcinoma

BACKGROUND

Spleen tyrosine kinase (Syk) is a nonreceptor tyrosine kinase and often aberrantly expressed in human cancers. However, Syk expression pattern has not yet been investigated in nasopharyngeal carcinoma (NPC).

METHODS

Samples of 223 NPC tissues were immunohistochemically stained for Syk expression and survival analysis was then performed. Interaction and co-localization of Syk with Epstein-Barr virus encoded latent membrane protein 2A (LMP2A) was explored.

RESULTS

High expression of Syk was detected in 24% of NPC cases, and correlated significantly with T classification, local recurrence, a lower 5-year survival rate, and a lower 5-year disease-free survival (DFS) rate. Syk expression was a significant, independent prognosis predictor for patients with NPC. LMP2A induced Syk expression in NPC and LMP2A high expression correlated with Syk high expression in NPC clinical samples.

CONCLUSION

High expression of Syk, which results partly from LMP2A expression in NPC, is associated with tumor recurrence and poor prognosis of patients with NPC.

A novel retinoblastoma therapy from genomic and epigenetic analyses

Retinoblastoma is an aggressive childhood cancer of the developing retina that is initiated by the biallelic loss of RB1. Tumours progress very quickly following RB1 inactivation but the underlying mechanism is not known. Here we show that the retinoblastoma genome is stable, but that multiple cancer pathways can be epigenetically deregulated. To identify the mutations that cooperate with RB1 loss, we performed whole-genome sequencing of retinoblastomas. The overall mutational rate was very low; RB1 was the only known cancer gene mutated. We then evaluated the role of RB1 in genome stability and considered non-genetic mechanisms of cancer pathway deregulation. For example, the proto-oncogene SYK is upregulated in retinoblastoma and is required for tumour cell survival. Targeting SYK with a small-molecule inhibitor induced retinoblastoma tumour cell death in vitro and in vivo. Thus, retinoblastomas may develop quickly as a result of the epigenetic deregulation of key cancer pathways as a direct or indirect result of RB1 loss.

Tricky and Terrible T-Cell Tumors: These are Thrilling Times for Testing: Molecular Pathology of Peripheral T-Cell Lymphomas

Peripheral T-cell lymphomas (PTCLs) encompass a group of rare and usually clinically aggressive diseases. The classification and diagnosis of these diseases are compounded by their marked pathological heterogeneity and complex clinical features. With the exception of ALK-positive anaplastic large cell lymphoma (ALCL), which is defined on the basis of ALK rearrangements, genetic features play little role in the definition of other disease entities. In recent years, hitherto unrecognized chromosomal translocations have been reported in small subsets of PTCLs, and genome-wide array-based profiling investigations have provided novel insights into their molecular characteristics. This article summarizes the current knowledge on the best-characterized genetic and molecular alterations underlying the pathogenesis of PTCLs, with a focus on recent discoveries, their relevance to disease classification, and their management implications from a diagnostical and therapeutical perspective.

Pathology and biology of peripheral T-cell lymphomas

Peripheral T-cell lymphomas (PTCLs) represent a heterogeneous group of more than 20 neoplastic entities derived from mature T cells and natural killer (NK) cells involved in innate and adaptive immunity. With few exceptions these malignancies, which may present as disseminated, predominantly extranodal or cutaneous, or predominantly nodal diseases, are clinically aggressive and have a dismal prognosis. Their diagnosis and classification is hampered by several difficulties, including a significant morphological and immunophenotypic overlap across different entities, and the lack of characteristic genetic alterations for most of them. Although there is increasing evidence that the cell of origin is a major determinant for the delineation of several PTCL entities, however, the cellular derivation of most entities remains poorly characterized and/or may be heterogeneous. The complexity of the biology and pathophysiology of PTCLs has been only partly deciphered. In recent years, novel insights have been gained from genome-wide profiling analyses. In this review, we will summarize the current knowledge on the pathobiological features of peripheral NK/T-cell neoplasms, with a focus on selected disease entities manifesting as tissue infiltrates primarily in extranodal sites and lymph nodes.

Peripheral T-cell lymphoma

Peripheral T-cell lymphomas (PTCLs) are a heterogeneous group of clinically aggressive diseases associated with poor outcome. Studies that focus specifically on PTCL are emerging, with the ultimate goal of improved understanding of disease biology and the development of more effective therapies. However, one of the difficulties in classifying and studying treatment options in clinical trials is the rarity of these subtypes. Various groups have developed lymphoma classifications over the years, including the World Health Organization, which updated its classification in 2008. This article briefly reviews the major lymphoma classification schema, highlights contributions made by the collaborative International PTCL Project, discusses prognostic issues and gene expression profiling, and outlines therapeutic approaches to PTCL. These include the standard chemotherapeutic regimens and other modalities incorporating antifolates, conjugates, histone deacetylase inhibitors, monoclonal antibodies, nucleoside analogs, proteasome inhibitors, and signaling inhibitors. As this review emphasizes, the problem has now evolved into an abundance of drugs and too few patients available to test them. Collaborative groups will aid in future efforts to find the best treatment strategies to improve the outcome for patients with PTCL.

Alternative splicing of SYK regulates mitosis and cell survival

Most human genes produce multiple mRNA isoforms through alternative splicing. However, the biological relevance of most splice variants remains unclear. In this study, we evaluated the functional impact of alternative splicing in cancer cells. We modulated the splicing pattern of 41 cancer-associated splicing events and scored the effects on cell growth, viability and apoptosis, identifying three isoforms essential for cell survival. Specifically, changing the splicing pattern of the spleen tyrosine kinase gene (SYK) impaired cell-cycle progression and anchorage-independent growth. Notably, exposure of cancer cells to epithelial growth factor modulated the SYK splicing pattern to promote the pro-survival isoform that is associated with cancer tissues in vivo. The data suggest that splicing of selected genes is specifically modified during tumor development to allow the expression of isoforms that promote cancer cell survival.

Diagnosis of Nodal Peripheral T-Cell Lymphomas

Lymph node-based peripheral T-cell lymphomas are rare and exhibit a morphologic spectrum that overlaps with reactive lymphoid hyperplasia, B-cell lymphomas, and Hodgkin lymphoma, presenting a diagnostic challenge. This review focuses on the major categories of lymph node-based peripheral T-cell lymphomas recognized by the 2008 World Health Organization Classification of Tumours of Haematopoietic and Lymphoid Tissues. Diagnostic strategies for approaching T-cell neoplasms using a combined clinical, morphologic, immunophenotypic, and genetic approach are presented. Practical information to aid in distinguishing peripheral T-cell lymphomas from other hematologic malignancies and benign conditions is provided.

New strategies in peripheral T-cell lymphoma: understanding tumor biology and developing novel therapies

Peripheral T-cell lymphomas (PTCL) constitute a group of heterogeneous diseases that are uncommon, representing, in Western countries, only approximately 10% of all non-Hodgkin lymphomas. They are typically associated with a poor prognosis compared with their B-cell counterparts and are much less well understood with respect to tumor biology, owing to their rarity and biologic heterogeneity, and to the fact that characteristic cytogenetic abnormalities are few compared with B-cell lymphomas. Although the outcome for patients with anaplastic large cell lymphoma (ALCL), particularly anaplastic lymphoma kinase (ALK)-positive ALCL, is good, other types of PTCLs are associated with a poor prognosis, even with aggressive anthracycline-based chemotherapy. In this respect, there is a need for new approaches in these diseases, and this review focuses on and explores recent experience with novel therapies in PTCL.

New targets of therapy in T-cell lymphomas

T-cell lymphomas (TCL) are characterized by poor response to chemotherapy and generally poor outcome. While molecular profiling has identified distinct biological subsets and therapeutic targets in B-cell lymphomas, the molecular characterization of TCL has been slower. Surface markers expressed on malignant T-cells, such as CD2, CD3, CD4, CD25, and CD52 were the first TCL-specific therapeutic targets to be discovered. However, the presence of these receptors on normal T-cells means that monoclonal antibody (mAb)- or immunotoxin (IT)-based therapy in TCL inevitably results in variable degrees of immunosuppression. Thus, although some mAbs/IT have significant activity in selected subsets of TCL, more specific agents that target signaling pathways preferentially activated in malignant T-cells are needed. One such novel class of agents is represented by the histone deacetylase (HDAC) inhibitors. These molecules selectively induce apoptosis in a variety of transformed cells, including malignant T-cells, both in vitro and in vivo. Several HDAC inhibitors have been studied in TCL with promising results, and have recently been approved for clinical use. Immunomodulatory drugs, such as interferons and Toll Receptor (TLR) agonists have significant clinical activity in TCL, and are particularly important in the treatment of primary cutaneous subtypes (CTCL). Although most classical cytotoxic drugs have limited efficacy against TCL, agents that inhibit purine and pyrimidine metabolism, known as nucleoside analogues, and novel antifolate drugs, such as pralatrexate, are highly active in TCL. With improved molecular profiling of TCL novel pharmacological agents with activity in TCL are now being discovered at an increasingly rapid pace. Clinical trials are in progress and these agents are being integrated in combination therapies for TCL, both in the relapsed/refractory setting as well as front line.

The SYK tyrosine kinase: a crucial player in diverse biological functions

Spleen tyrosine kinase (SYK) is known to have a crucial role in adaptive immune receptor signalling. However, recent reports indicate that SYK also mediates other, unexpectedly diverse biological functions, including cellular adhesion, innate immune recognition, osteoclast maturation, platelet activation and vascular development. SYK is activated by C-type lectins and integrins, and activates new targets, including the CARD9-BCL-10-MALT1 pathway and the NLRP3 inflammasome. Studies using Drosophila melanogaster suggest that there is an evolutionarily ancient origin of SYK-mediated signalling. Moreover, SYK has a crucial role in autoimmune diseases and haematological malignancies. This Review summarizes our current understanding of the diverse functions of SYK and how this is being translated for therapeutic purposes.

Disturbed expression of the T-cell receptor/CD3 complex and associated signaling molecules in CD30+ T-cell lymphoproliferations

BACKGROUND

CD30(+) T-cell lymphoproliferations comprise a spectrum of clinically heterogeneous entities, including systemic anaplastic large cell lymphomas (ALK(-) and ALK(+)) and primary cutaneous CD30(+) T-cell lymphoproliferative disorders. While all these entities are characterized by proliferation of highly atypical, anaplastic CD30(+) T cells, the expression of T-cell specific antigens in the tumor cells is not consistently detectable.

DESIGN AND METHODS

We evaluated biopsies from 19 patients with primary cutaneous CD30(+) lymphoproliferative disorders, 38 with ALK(-) and 33 with ALK(+) systemic anaplastic large cell lymphoma. The biopsies were examined for the expression of T-cell receptorαβ/CD3 complex (CD3γ, δ, ε, ζ), transcription factors regulating T-cell receptor expression (ATF1, ATF2, TCF-1, TCF-1α/LEF-1, Ets1), and molecules of T-cell receptor-associated signaling cascades (Lck, ZAP-70, LAT, bcl-10, Carma1, NFATc1, c-Jun, c-Fos, Syk) using immunohistochemistry.

RESULTS

In comparison to the pattern in 20 peripheral T-cell lymphomas, not otherwise specified, we detected a highly disturbed expression of the T-cell receptor/CD3 complex, TCF-1, TCF-1α/LEF-1, Lck, ZAP-70, LAT, NFATc1, c-Jun, c-Fos and Syk in most of the systemic anaplastic large cell lymphomas. In addition, primary cutaneous CD30(+) lymphoproliferative disorders showed such a similar expression pattern to that of systemic anaplastic large cell lymphomas, that none of the markers we investigated can reliably distinguish between these CD30(+) T-cell lymphoproliferations.

CONCLUSIONS

Severely altered expression of the T-cell receptor/CD3 complex, T-cell receptor-associated transcription factors and signal transduction molecules is a common characteristic of systemic and cutaneous CD30(+) lymphoproliferations, although the clinical behavior of these entities is very different. Since peripheral T-cell lymphomas, not otherwise specified retain the full expression program required for functioning T-cell receptor signaling, the differential expression of a subset of these markers might be of diagnostic utility in distinguishing peripheral T-cell lymphomas, not otherwise specified from the entire group of CD30(+) lymphoproliferations.

Peripheral T cell lymphoma: new model + new insight

The nonreceptor tyrosine kinase SYK has recently received a good deal of attention as a critical oncogene in various hematologic malignancies. A newly developed model of peripheral T cell lymphoma (PTCL) using the ITK-SYK fusion gene should serve as a powerful tool to dissect the signaling cascades important for SYK-associated malignancy in the context of t(5;9) PTCL.

The fusion kinase ITK-SYK mimics a T cell receptor signal and drives oncogenesis in conditional mouse models of peripheral T cell lymphoma

Peripheral T cell lymphomas (PTCLs) are highly aggressive malignancies with poor prognosis. Their molecular pathogenesis is not well understood and small animal models for the disease are lacking. Recently, the chromosomal translocation t(5;9)(q33;q22) generating the interleukin-2 (IL-2)–inducible T cell kinase (ITK)–spleen tyrosine kinase (SYK) fusion tyrosine kinase was identified as a recurrent event in PTCL. We show that ITK-SYK associates constitutively with lipid rafts in T cells and triggers antigen-independent phosphorylation of T cell receptor (TCR)–proximal proteins. These events lead to activation of downstream pathways and acute cellular outcomes that correspond to regular TCR ligation, including up-regulation of CD69 or production of IL-2 in vitro or deletion of thymocytes and activation of peripheral T cells in vivo. Ultimately, conditional expression of patient-derived ITK-SYK in mice induces highly malignant PTCLs with 100% penetrance that resemble the human disease. Our work demonstrates that constitutively enforced antigen receptor signaling can, in principle, act as a powerful oncogenic driver. Moreover, we establish a robust clinically relevant and genetically tractable model of human PTCL.

Signal transduction inhibitor therapy for lymphoma

Current research in lymphoma is focused on two areas of lymphoma biology-the signal transduction pathways used to maintain the growth of malignant lymphocytes and the role of the tumor microenvironment in lymphoma growth and survival. This review focuses on three signaling pathways: the phosphatidylinositol 3-kinase/mammalian target of rapamycin (PI3K/mTOR) pathway, the B-cell receptor/spleen tyrosine kinase (BCR/Syk) pathway, and the protein kinase C-beta (PKC-β) pathway, known to be important to lymphoma cells. The mTOR inhibitors temsirolimus and everolimus have demonstrated antitumor activity in all types of lymphoma, the Syk inhibitor fostamatinib has activity in diffuse large B-cell lymphoma and chronic lymphocytic leukemia, and the PKC-β inhibitor enzastaurin is being used as consolidation therapy after remission in diffuse large B-cell lymphoma. This review discusses the biology behind the development of each new agent and the results of initial clinical trials. The goal is to provide the hematologist/oncologist background information on these new agents and understand their current and potential role in the management of patients.

Comparison of the anti-allergic activity of Syk inhibitors with optimized Syk siRNAs in FcepsilonRI-activated RBL-2H3 basophilic cells

Spleen tyrosine kinase (Syk) binds ITAM-bearing receptors in a wide variety of cell types. One such example is the activation of mast cells, basophils and eosinophils via the stimulation of the FcepsilonRI receptor by IgE/allergen complexes. The possible role of Syk in inflammatory signaling cascades has led to the development of pharmacological agents designed to block the Syk catalytic domain as potential novel therapeutics. Whilst the enzymatic activity of Syk lends towards the design of small-molecule inhibitors, other attention has focused on the possibility of targeting Syk expression using anti-sense oligonucleotides as an alternate means of anti-inflammatory therapy. In this study, we compared the ability of multiple optimized Syk siRNA sequences and small-molecule Syk inhibitors to block FcepsilonRI-mediated signal transduction, degranulation and TNFalpha secretion in the basophilic cell line RBL-2H3. We also characterized the specificity of each siRNA sequence with regards to off-target induction of the interferon-inducible gene IFIT1. We identified a single siRNA sequence, which displayed a favorable profile of efficient Syk knockdown, blockage of FcepsilonRI-mediated signal transduction, degranulation and TNFalpha secretion and a lack of IFIT1 induction. The effect of this siRNA was comparable to that of the Syk kinase domain inhibitors BAY61-3606 and R406. The identification of an active and specific Syk siRNA could be a basis for the development of therapeutic Syk siRNAs against inflammatory diseases.

Proteomic and genetic approaches identify Syk as an AML target

Cell-based screening can facilitate the rapid identification of compounds inducing complex cellular phenotypes. Advancing a compound toward the clinic, however, generally requires the identification of precise mechanisms of action. We previously found that epidermal growth factor receptor (EGFR) inhibitors induce acute myeloid leukemia (AML) differentiation via a non-EGFR mechanism. In this report, we integrated proteomic and RNAi-based strategies to identify their off-target, anti-AML mechanism. These orthogonal approaches identified Syk as a target in AML. Genetic and pharmacological inactivation of Syk with a drug in clinical trial for other indications promoted differentiation of AML cells and attenuated leukemia growth in vivo. These results demonstrate the power of integrating diverse chemical, proteomic, and genomic screening approaches to identify therapeutic strategies for cancer.