STAT5B Mutations Research Articles

Clinical and laboratory characteristics in patients with myeloid neoplasms complicated with clonal T large granular lymphocyte proliferation

目的探讨髓系肿瘤合并克隆性T大颗粒淋巴细胞（T-LGL）增殖的临床及实验室特征。方法回顾性分析中国医学科学院血液病医院2017年11月至2018年11月收治的5例确诊髓系肿瘤合并克隆性T-LGL增殖患者的临床资料。结果5例患者中位年龄60岁，均存在>6个月的血细胞异常病史。外周血T-LGL绝对计数均<1.0×109/L，LGL免疫表型2例为CD4+CD8−，3例为CD4−CD8+；4例为αβ型T细胞，1例为γδ型T细胞；5例均有克隆性证据；二代测序检测显示1例患者存在STAT3突变，其余4例均为阴性。结论5例髓系肿瘤合并克隆性T-LGL增殖患者起病隐匿，以老年为主，临床以慢性血细胞减少多见。存在克隆性T-LGL，尤其是T-LGL绝对计数<0.5×109/L的患者诊断T大颗粒淋巴细胞白血病需慎重，可能与意义未明的T细胞克隆性疾病部分重叠。STAT3或STAT5b突变检测可能是鉴别两者的主要手段。

STAT3 Mutation Is Associated with STAT3 Activation in CD30+ ALK- ALCL.

Peripheral T-cell lymphomas (PTCL) are a heterogeneous, and often aggressive group of non-Hodgkin lymphomas. Recent advances in the molecular and genetic characterization of PTCLs have helped to delineate differences and similarities between the various subtypes, and the JAK/STAT pathway has been found to play an important oncogenic role. Here, we aimed to characterize the JAK/STAT pathway in PTCL subtypes and investigate whether the activation of the pathway correlates with the frequency of STAT gene mutations. Patient samples from AITL (n = 30), ALCL (n = 21) and PTCL-NOS (n = 12) cases were sequenced for STAT3, STAT5B, JAK1, JAK3, and RHOA mutations using amplicon sequencing and stained immunohistochemically for pSTAT3, pMAPK, and pAKT. We discovered STAT3 mutations in 13% of AITL, 13% of ALK+ ALCL, 38% of ALK− ALCL and 17% of PTCL-NOS cases. However, no STAT5B mutations were found and JAK mutations were only present in ALK- ALCL (15%). Concurrent mutations were found in all subgroups except ALK+ ALCL where STAT3 mutations were always seen alone. High pY-STAT3 expression was observed especially in AITL and ALCL samples. When studying JAK-STAT pathway mutations, pY-STAT3 expression was highest in PTCLs harboring either JAK1 or STAT3 mutations and CD30+ phenotype representing primarily ALK− ALCLs. Further investigation is needed to elucidate the molecular mechanisms of JAK-STAT pathway activation in PTCL.

Insights Into Genetic Landscape of Large Granular Lymphocyte Leukemia.

Large granular lymphocyte leukemia (LGLL) is a chronic proliferation of clonal cytotoxic lymphocytes, usually presenting with cytopenias and yet lacking a specific therapy. The disease is heterogeneous, including different subsets of patients distinguished by LGL immunophenotype (CD8+ Tαβ, CD4+ Tαβ, Tγδ, NK) and the clinical course of the disease (indolent/symptomatic/aggressive). Even if the etiology of LGLL remains elusive, evidence is accumulating on the genetic landscape driving and/or sustaining chronic LGL proliferations. The most common gain-of-function mutations identified in LGLL patients are on STAT3 and STAT5b genes, which have been recently recognized as clonal markers and were included in the 2017 WHO classification of the disease. A significant correlation between STAT3 mutations and symptomatic disease has been highlighted. At variance, STAT5b mutations could have a different clinical impact based on the immunophenotype of the mutated clone. In fact, they are regarded as the signature of an aggressive clinical course with a poor prognosis in CD8+ T-LGLL and aggressive NK cell leukemia, while they are devoid of negative prognostic significance in CD4+ T-LGLL and Tγδ LGLL. Knowing the specific distribution of STAT mutations helps identify the discrete mechanisms sustaining LGL proliferations in the corresponding disease subsets. Some patients equipped with wild type STAT genes are characterized by less frequent mutations in different genes, suggesting that other pathogenetic mechanisms are likely to be involved. In this review, we discuss how the LGLL mutational pattern allows a more precise and detailed tumor stratification, suggesting new parameters for better management of the disease and hopefully paving the way for a targeted clinical approach.

Cancer Activating Mutations in STAT5B: Elucidating the Impact on Protein Structure and Dynamics using Atomistic Molecular Simulations

Cancer Activating Mutations in STAT5B: Elucidating the Impact on Protein Structure and Dynamics using Atomistic Molecular Simulations

STAT3 Mutations and Anemia with Pure Red Cell Aplasia Are the Distinctive Features of T Cell Receptor Gamma Delta Type Large Granular Lymphocyte Leukemia

Large granular lymphocytic leukemia (LGLL) is a heterogenous group of disorders. The clinical presentations of LGLL are highly variable; it may present with neutropenia or anemia, complicated with recurrent infections, autoimmune diseases such as rheumatoid arthritis, and neurological symptoms, requiring therapeutic interventions. It may present only with indolent laboratory changes without any symptoms. The cytological phenotypes of LGLL also vary and they commonly include CD8+TCR αβ-type, CD4+TCR αβ-type, and NK cell-type. NK cell-type LGLL is designated as chronic lymphoproliferative disorder of NK cells (CLPD-NK). TCR γδ-type LGLL (γδT-LGLL) is even rarer and it often confers cytopenia. The genetic backgrounds of LGLL with CD8+TCRαβ-type, CD4+TCRαβ-type and NK cell-type have been elucidated with the recent sequencing technologies. JAK/STAT signaling genes and chromatin-modifying genes were frequently mutated in the non-leukemic counterpart of the lymphoid malignancies with γδ TCR immunophenotypes, such as hepatosplenic T-cell lymphoma, monomorphic epitheliotropic intestinal T-cell lymphoma and primary cutaneous gamma delta T-cell lymphoma. However, the genetic basis of γδT-LGLL and the genetic-phenotypic associations remain unclear. The aim of this study is to identify clinical and genetic characteristics of γδT-LGLL in comparison with other LGL leukemias. In total, 56 LGLL patients were recruited; six patients with γδT-LGLL, 25 CD8+ TCRαβ type, 8 CD4+TCR αβ type and 17 CLPD-NK, in this study. All cases were negative for EBV. The median age of patients with γδT-LGLL was 48 years old and five of them were male. The median LGL counts and hemoglobin level were 1.81 ×109/L (range; 0.60-4.42) and 5.8 g/dL (range; 3.0-11.2), respectively. All patients with γδT-LGLL had anemia and/or neutropenia, although no patients were thrombocytopenic. 4 patients presented with pure red cell aplasia. Common immunophenotypes of γδT cells were CD2+ CD3+ CD4-CD7+. 3 patients were CD8+. CD16, CD56 and CD57 were positive in 3, 0, and 1 patient, respectively. γδT cells of all patients showed a monoclonal pattern of TCRγ gene rearrangements with BioMed 2 protocol. We performed amplicon sequencing of entire coding regions of STAT3, STAT5B and TNFAIP3 genes and allele-specific PCR for several hot spot regions of STAT3 and STAT5B genes using extracted DNA from mononuclear cells of peripheral blood. Mutations in STAT3 and TNFAIP3 were identified in 100% (6/6) and 17% (1/6), respectively. Among the10 STAT3 mutations identified, 5 were located in the SH-2 domain, while other 3 were in coiled-coiled domain and the other 2 were in the DNA binding domain. The median variant allele frequencies of STAT3 was 2.0% (0.7-22.6) and STAT3 mutations were restricted to sorted γδT cells in all 3 patients examined. No patient was positive for STAT5B mutations, including N642H and Y665F with allele specific PCRs. One of 5 patients who were treated with cyclosporin A was refractory. Two patients were treated with cyclophosphamide, showing clinical improvements. The patients with γδT-LGLL were younger than those with other types of LGLL (P=0.048) and anemia and STAT3 mutations were significantly more frequent in γδT-LGLL (P value; 0.003 and 0.02, respectively). PRCA was a consistent cause of anemia in γδT-LGLL. Low frequency of STAT5B mutations among γδT-LGLL patients was in contrast to other aggressive γδT cell lymphoma in which STAT5B frequently mutated. The clinical characteristics of γδT-LGLL patients may be defined by younger age and the anemia due to pure red cell aplasia, and the frequent STAT3 mutations might be a novel molecular marker for γδT-LGLL. Disclosures Yamane: Pfizer: Research Funding; Celgene: Honoraria; Bristol-Meyers Squibb: Research Funding; Chugai Pharmaceutical: Consultancy, Research Funding; Astellas Pharma: Research Funding; Eli Lily and Company: Research Funding. Ishida:Eli Lily and Company: Research Funding; Astellas Pharma: Research Funding; Pfizer: Research Funding; Bristol-Meyers Squibb: Research Funding; Chugai Pharmaceutical: Consultancy, Research Funding; Celgene: Honoraria.

Characterizing the Anti-Apoptotic Dependencies of T-Cell Prolymphocytic Leukemia Identifies HDAC and JAK/STAT Pathway Inhibitors As Promising Combination Partners to Augment Bcl-2 Targeted Killing By Venetoclax

Characterizing the Anti-Apoptotic Dependencies of T-Cell Prolymphocytic Leukemia Identifies HDAC and JAK/STAT Pathway Inhibitors As Promising Combination Partners to Augment Bcl-2 Targeted Killing By Venetoclax

The Clinical and Functional Relevance of the Transforming AKT E17K Mutation in T-ALL

INTRODUCTION. The importance of IL-7R signaling has been thoroughly studied in the context of both normal T-cell development and leukemogenesis. Upon IL-7 induced heterodimerization of the IL-7Rα and the γc chain, downstream signaling routes regulate survival and proliferation of differentiating T-cells. JAK-STAT, MAPK-ERK and PI3K-AKT pathways are aberrantly activated in T-cell acute lymphoblastic leukemia (T-ALL) patients by recurrent gain-of-function mutations of the IL-7R signaling pathway. IL-7R signaling mutations are a result of mutations in IL7Ra, JAK1/3, PTPN11, NF1, STAT5B, N/KRAS, PI3K or AKT that are found in nearly 35% of pediatric T-ALL patients and are associated with steroid resistance and inferior event-free survival. Here we focus on downstream AKT activation in relation to cellular transformation and steroid resistance. We previously demonstrated that AKTE17K transforms IL3-dependent BaF3 cells in contrast to wild type AKT, while wild type AKT drives steroid resistance in SUP-T1 T-ALL cells in contrast to mutant AKTE17K. AIM. Our aim was to identify functional differences between AKT and AKTE17K molecules in respect to cellular transformation and steroid resistance. We assessed activation level, cellular localization and downstream signaling events that may explain these functional differences. RESULTS. For this study, we used doxycycline-inducible SUP-T1 cell lines that overexpress wild type AKT or mutant AKTE17K molecules. Using immunohistochemistry, we revealed abundant cytoplasmic localization of wild type AKT but predominant plasma membrane localization of AKTE17K and extends previous findings by others. Furthermore, we found evidence for phosphorylation of wild type AKT on serine-473 (S473) and threonine-308 (T308) residues in both cytoplasmic and nuclear fractions, indicating that part of induced AKT becomes activated. In contrast, expression of AKTE17K was accompanied with abundant phosphorylation of T308 while having relatively low levels of S473 phosphorylation. The T308/S473 phosphorylation ratio was 5 times higher for AKTE17K compared to wild type AKT. These results are in line with current views on AKT activation that S473 phosphorylation facilitates the opening of the AKT pleckstrin homology domain and membrane docking, after which AKT is phosphorylated (activated) on the T308 residue by PDK1. The constitutive plasma membrane localization and open conformation of AKTE17K as a result of its E17K pleckstrin homology domain mutation leaves it independent of S473 phosphorylation and results in enhanced T308 phosphorylation by PDK1. Consequently, AKTE17K mutant cells may exhibit reduced cellular sensitivity to allosteric AKT inhibitors but not to type I ATP-competitive inhibitors. Indeed, SUP-T1 cells expressing wild type AKT or mutant AKTE17K are equally sensitivity to the ATP-competitive AZD5363 inhibitor, but AKTE17K cells display reduced sensitivity to the MK2206 allosteric inhibitor compared to AKT wild type cells. In an attempt to explain enhanced steroid resistance by expression of wild type AKT but not mutant AKTE17K, we found no differences in AKT-mediated S134 phosphorylation of the NR3C1 steroid receptor or impaired nuclear import of NR3C1 following steroid treatment (Piovan et al., Cancer Cell 2013). This indicates that AKT induces steroid resistance by other mechanisms in our SUP-T1 cell system. CONCLUSIONS. In contrast to wild type AKT overexpression, we demonstrated that AKTE17K has (i) transforming activity, (ii) does not yield cellular resistance to steroid treatment, (iii) is predominantly localized at the plasma membrane, (iv) has high T308 over S473 phosphorylation and (v) is less sensitive to the MK2206 allosteric AKT-inhibitor. These observed differences are likely caused by the constitutively open AKTE17K conformation. Since no differences in NR3C1 phosphorylation or nuclear shuttling were observed in our model, we hypothesize other mechanisms underlie the provoked steroid resistance by AKT wild type overexpression. To identify these novel mechanisms, we are currently performing an unbiased phospho-protein array to identify differentially phosphorylated AKT substrates. Disclosures No relevant conflicts of interest to declare.

PF479 CLINICAL AND BIOLOGICAL PREDICTORS OF OUTCOME IN LARGE GRANULAR LYMPHOCYTE LEUKEMIA: A SINGLE CENTER EXPERIENCE OF 205 PATIENTS

Background:Large Granular Lymphocyte Leukemia (LGLL) is a rare chronic lymphoproliferative disorder characterized by the expansion of LGLs. Among LGLL, WHO 2016 classification recognizes a CD3+ T‐LGLL and a CD3‐ Chronic Lymphoproliferative disorder of Natural Killer cells (CLPD‐NK), accounting for 85% and 15% of cases respectively. Moreover, according to the T cell receptor rearrangement, the Tαβ and Tγδ subsets can be identified. From a clinical point of view, LGLL is a heterogeneous disease with some patients being asymptomatic and other developing cytopenias, mostly neutropenia. The aetiology is still unknown but a constitutive activation of JAK/STAT pathway is involved in LGL proliferation, supported by the evidence of somatic STAT3 and STAT5b mutations in approximately 40% of patients. We previously demonstrated that in T‐LGLL STAT3 mutations are associated to symptomatic disease.Aims:The aim of this study is to analyse clinical and biological features of a large cohort of LGLL patients to identify prognostic markers affecting patients’ outcome.Methods:From 1992 to 2018, clinical and biological data of 205 patients affected by LGLL have been collected. STAT3 exon 21 mutation analysis and STAT5b exon 16–18 mutation analysis was performed by Sanger sequencing.Results:In our cohort, median age at diagnosis was 58 years. By phenotype, 129/205 (62.9%) patients were affected by Tαβ LGLL, 23/205 (11.2%) by Tγδ LGLL, and 36/205 (17.6%) by CLPD‐NK. Moreover, 17 patients (8.3%) were characterized by a bi‐phenotypical variant, identified by a concomitant T/NK or Tαβ/Tγδ clone. According to CD4 and CD8 expression, Tαβ LGLL was further classified in CD4‐/CD8+ LGLL (CD8+ T‐LGLL, 84/205, 41%) and CD4+/CD8dim/neg LGLL (CD4+ T‐LGLL, 45/205, 21.9%).Neutropenia (Absolute Neutrophil's Count, ANC&lt;1,500/mm3) was the most relevant feature (78/205, 38%), severe neutropenia (ANC&lt;500/mm3) being present in 20.5% of patients. Anemia (Hb&lt;120 g/L, 27/205, 13.2%), severe anemia (Hb&lt;90 g/L, 20/205, 9.8%) and thrombocytopenia (PLTs &lt;100.000/mm3, 12/205, 4.8%) were less recurring. 44 patients (21.5%) were affected by concomitant autoimmune/inflammatory disease, mostly autoimmune hemolytic anemia and rheumatoid arthritis.DNA samples of 166 and 152 patients were available for STAT3 and STAT5b mutations analysis, respectively. STAT3 mutations were detected in 47 patients (28.3%), with higher frequency in CD8+ Tαβ LGLL towards Tγδ LGLL (60% vs 25%, p = 0.0232) and CLPD‐NK (60% vs 5.8%, p &lt; 0.0001). At variance, STAT5b mutations were found in 15 patients (9.8%), mostly in CD4+ Tαβ LGLL (12/35 cases available, 34.3%) and in 3 cases were Tγδ LGLL. Interestingly, STAT3 and STAT5b mutations were mutually exclusive in CD8+ and CD4+ Tαβ LGLL.With a median follow up of 8 years, median overall survival (OS) of our cohort was not reached. Major features associated to reduced OS were ANC&lt;500/mm3 (267 months vs not reached, p = 0.0297), severe anemia (144 months vs not reached, p &lt; 0.0001), treatment requirement (214 vs not reached, p = 0.0011) and presence of STAT3 mutations (267 months vs not reached, p = 0.0113) (Figure 1, Panel A to D). No significant survival differences were found between STAT5b mutated and wild‐type patients (not reached vs 267 months, p = 0.3514).Summary/Conclusion:Our results confirmed the remarkable biological and clinical heterogeneity of LGLL. We identified clinical and biological features associated to reduced OS in LGLL patients and, for the first time, we demonstrated the dismal impact of STAT3 mutations in patients’ survival, suggesting that this marker should be regarded as a potential target of therapy.image

Molecular profile of early-stage and advanced-stage of renal cell cancer in China.

e16071 Background: The mutation spectrum has been extensively studied in Renal Cell Cancer (RCC), a heterogeneous disease. While major investigations have focused on metastatic RCC (mRCC). This study intended to explore the molecular characteristics between early-stage (stage I/Ⅱ) and advanced-stage (Ⅲ/Ⅳ) of RCC patients (pts). Methods: 36 tumor specimens were obtained from individual pts diagnosed RCC, including 22 tissues paired with blood samples. Somatic mutations were identified via targeted next generation sequencing with Acornmed panel including 808 genes associated with tumor development. Sequencing data were analyzed to call tumor specific single nucleotide variants (SNV), small insertions and deletions (InDels), copy number alterations (CNA) and chromosomal rearrangements. Clinical data of a cohort from TCGA who had RCC was collected and analyzed. Results: Among the 36 pts enrolled, 61% were early-stage group and 39% were advanced-stage group. The most frequently mutated genes in RCC were VHL (50%), PBRM1 (14%), BAP1 (11%), TP53 (11%) and PIK3CA (6%). Truncating mutations were the most frequent alterations accounting for 66% (33/50) of genetic alterations. Mutations in VHL, BAP1, PBRM1 and TP53 were shared by both early and advanced RCC. While mutations in PIK3CA, CDKN2C, EGFR, FAMCA, GRIN2A, KDM6A, SOX17, TSC1 and APC were only detected in early stage group. KNSTRN, KRAS, MYD88, NF2, ATM, PTEN and STAT5B mutations were only detected in advanced group. Among 22 plasma samples, genomic alterations were detected in 40.9% (9/22) of pts postoperatively, such as TP53, PIK3CA, PTEN, and APC. Functional annotation clustering revealed that 4/9 in these genes were tumor suppressors, which negatively regulated apoptosis. Pts with genomic alterations in TP53 (p = 0.0034), PIK3CA (p = 0.0015) or PTEN (p = 0.00017) had worse OS significantly (TCGA). Conclusions: VHL, PBRM1, BAP1 were the most important driver genes mainly detected in all stages of RCC. The heterogeneity between early and advanced-stage may be related with clinical status. Gene alterations in plasma ctDNA postoperatively should have the potential to stratify patients with different prognostic outcome.

Twins with different personalities: STAT5B\u2014but not STAT5A\u2014has a key role in BCR/ABL-induced leukemia

Deregulation of the Janus kinase/signal transducers and activators of transcription (JAK/STAT) signaling pathway is found in cancer with STAT5A/B controlling leukemic cell survival and disease progression. As mutations in STAT5B, but not STAT5A, have been frequently described in hematopoietic tumors, we used BCR/ABL as model systems to investigate the contribution of STAT5A or STAT5B for leukemogenesis. The absence of STAT5A decreased cell survival and colony formation. Even more drastic effects were observed in the absence of STAT5B. STAT5B-deficient cells formed BCR/ABL+ colonies or stable cell lines at low frequency. The rarely evolving Stat5b−/− cell lines expressed enhanced levels of BCR/ABL oncoprotein compared to wild-type cells. In line, Stat5b−/− leukemic cells induced leukemia with a significantly prolonged disease onset, whereas Stat5a−/− cells rapidly caused a fatal disease superimposable to wild-type cells. RNA-sequencing (RNA-seq) profiling revealed a marked enhancement of interferon (IFN)-α and IFN-γ signatures in Stat5b−/− cells. Inhibition of IFN responses rescued BCR/ABL+ colony formation of Stat5b−/−-deficient cells. A downregulated IFN response was also observed in patients suffering from leukemia carrying STAT5B mutations. Our data define STAT5B as major STAT5 isoform driving BCR/ABL+ leukemia. STAT5B enables transformation by suppressing IFN-α/γ, thereby facilitating leukemogenesis. Our findings might help explain the high frequency of STAT5B mutations in hematopoietic tumors.

Somatic Mutations in T Cells As Possible Regulators of Immunodeficiency

▪The pathogenesis of common variable immunodeficiency (CVID) and many other immunodeficiencies is elusive, and no cure for these diseases exists. The characteristic features of CVID are immunoglobulin deficiency and recurrent infections, but autoimmunity co-manifests in 30% and lymphoproliferation in 50% of CVID cases. The failure to produce sufficient quantities of immunoglobulins is attributed to B cells, but as T cells are critical players in adaptive immune response and autoimmune disease, they have also suggested to play a role in CVID. As monogenic germline mutations account only for 2-10% of CVID cases, the etiology of CVID remains unknown in most cases.To study if somatic mutations in T cells contribute to immunodeficiencies, we recruited patients with broad immune dysregulation: 8 patients with late-onset CVID, and 9 patients with other type of immunodeficiency and/or severe autoimmunity. All patients signed informed consent and the declaration of Helsinki principles were followed. Study design and key patient characteristics are depicted in the Figure. To discover somatic mutations in T cells, we sequenced both CD4+ and CD8+ cells with a custom gene panel comprising of 2500 immune-related genes with an average coverage of 500x. Somatic variants were identified using the GATK MuTect2 toolset by using a panel of 21 healthy controls' CD4+ and CD8+ cells as a background. Variants were called using paired samples (CD4+ vs CD8+ and vice versa). This approach identifies variants that have occurred in mature T cells. To complement this approach, we performed variant calling also in single-sample mode to identify variants originating from hematopoietic progenitors.Paired-sample analyses revealed 44 somatic mutations in mature T cells in 10/17 (59%) patients: 30 (68%) in CD8+ and 14 (32%) in CD4+ cells. The mutations included 2 frameshift-, 37 missense-, and 5 nonsense variants. In silico tools (both Polyphen-2 and SIFT) predicted 19 (51%) of the missense mutations to be damaging. The Catalogue Of Somatic mutations In Cancer (COSMIC) database included 9/44 (20%) of all mutations. Also, pathway analysis annotated 20% of the mutated genes to be involved in inflammatory response regulation, 27.5% in protein phosphorylation regulation, and 22.5% in positive regulation of cell proliferation. Interesting mutation findings included two patients with STAT5B mutations (N418K and T628S) with a low variant-allele (VAF) frequencies (3.2-3.6% in CD4+ cells), one patient with a KRAS T58I mutation (VAF 7.9% in CD8+), and two patients with distinct C5AR1 mutations (R197W and T62M). Complementing the paired-sample variant calling strategy, single-sample analyses revealed mutations associated with clonal hematopoiesis with low VAFs (2.2-5.5%) in T cells in 4 (23.5%) patients. Three patients had DNMT3A mutations and one patient 4 distinct TET2 mutations (2 nonsense-, 1 frameshift-, and 1 missense mutations).CD4+ and CD8+ T-cell receptor (TCR) repertoires were profiled with deep TCR beta chain (TCRB) sequencing. Healthy controls' CD4+ and CD8+ cells (n=27) were used as comparators. Although some CVID patients harbor major (17-20% of CD8+) T-cell clones, overall CD4+ or CD8+ clonality did not significantly differ from age-matched healthy controls. As a marker of selective pressure, CVID patients' CD4+ and CD8+ cells harbored more clones that shared a CDR3 amino-acid but had distinct nucleotide CDR3 sequences than healthy controls (7.0% vs 3.3% of all amino-acid rearrangements, p=0.021 for CD8+; 4.3% vs 3.5% p=0.013 for CD4+). These TCRs were not enriched with pathogen-specific (such as cytomegalovirus or Epstein-Barr virus) TCRs. Moreover, high CD4+ clonality was associated with a lower frequency of switched-memory-B cells.In conclusion, somatic mutations in T cells occurred in 59% of patients with immunodeficiency in this study, and some of the mutated genes (such as STAT5B) have previously been implicated for the pathogenesis of autoimmunity and lymphoproliferation. Also, clonal hematopoiesis in T cells was discovered in 23.5% of patients. The overall T-cell clonality was not increased, but CVID patients showed slight selective pressure in the TCR repertoire. Our results demonstrate that further research on somatic mutations in immunodeficiencies is needed, as they may contribute to disease pathogenesis in a subset of immunodeficiency patients. DisclosuresMartelius:Gilead: Other: lecture fee; Octapharma: Other: travel grant; CSL Behring: Other: lecture fee and travel grant; MSD: Other: lecture fee and travel grant; Sanguin: Other: travel grant and grants. Kankainen:Medix Biochemica: Consultancy. Seppänen:CSL Behring: Other: Chairing and speaker fees. Mustjoki:Ariad: Research Funding; Pfizer: Honoraria, Research Funding; Bristol-Myers Squibb: Honoraria, Research Funding; Celgene: Honoraria; Novartis: Honoraria, Research Funding.

Lenalidomide in Combination with CHOP in Patients with Angioimmunoblastic T-Cell Lymphoma (AITL): Final Analysis of Clinical and Molecular Data of a Phase 2 Lysa Study

Lenalidomide in Combination with CHOP in Patients with Angioimmunoblastic T-Cell Lymphoma (AITL): Final Analysis of Clinical and Molecular Data of a Phase 2 Lysa Study

Genetic and Transcriptomic Variation Linked to Neutrophil Granulocyte-Macrophage Colony-Stimulating Factor Signaling in Pediatric Crohn's Disease.

Granulocyte-macrophage colony-stimulating factor auto-antibodies (GMAbs) suppress neutrophil-extrinsic GM-CSF signaling and increase risk for stricturing behavior in Crohn's disease (CD). We aimed to define clinical, genomic, and functional associations with neutrophil-intrinsic GM-CSF signaling. Missense mutations in CSF2RA, CSF2RB, JAK2, STAT5A, and STAT5B were identified using whole-exome sequencing in 543 pediatric inflammatory bowel disease (IBD) patients. Neutrophil-intrinsic GM-CSF signaling was defined using the GM-CSF-induced STAT5 stimulation index (GMSI) in 180 pediatric IBD patients and 26 non-IBD controls. Reduced GM-CSF signaling (GMSI-Lo) was defined as the 20th percentile within the control group. Variation in neutrophil phospho-protein abundance, bacterial killing, and the global pattern of gene expression with the GMSI was determined. We validated 18 potentially damaging missense mutations in CSF2RA and CSF2RB. CSF2RA A17G carriage increased from 10% in those with intact neutrophil GMSI to 32% in those with low GMSI (P = 0.02). The frequency of reduced Staphylococcus aureus killing increased from 17% in those with intact neutrophil GMSI to 35% in GMSI-Lo neutrophils (P = 0.043). Crohn's disease neutrophils with low GMSI exhibited specific alterations in phospho-protein networks and genes regulating cytokine production, wound healing, and cell survival and proliferation. Stricturing behavior increased from 7% in patients with both low GMAb and intact GMSI to 64% in patients with both elevated GMAb and low GMSI (P < 0.0001). Low/normal neutrophil-intrinsic GM-CSF signaling is associated with CSF2RA missense mutations, alterations in gene expression networks, and higher rates of disease complications in pediatric CD.

Dominant-negative STAT5B mutations cause growth hormone insensitivity with short stature and mild immune dysregulation

Growth hormone (GH) insensitivity syndrome (GHIS) is a rare clinical condition in which production of insulin-like growth factor 1 is blunted and, consequently, postnatal growth impaired. Autosomal-recessive mutations in signal transducer and activator of transcription (STAT5B), the key signal transducer for GH, cause severe GHIS with additional characteristics of immune and, often fatal, pulmonary complications. Here we report dominant-negative, inactivating STAT5B germline mutations in patients with growth failure, eczema, and elevated IgE but without severe immune and pulmonary problems. These STAT5B missense mutants are robustly tyrosine phosphorylated upon stimulation, but are unable to nuclear localize, or fail to bind canonical STAT5B DNA response elements. Importantly, each variant retains the ability to dimerize with wild-type STAT5B, disrupting the normal transcriptional functions of wild-type STAT5B. We conclude that these STAT5B variants exert dominant-negative effects through distinct pathomechanisms, manifesting in milder clinical GHIS with general sparing of the immune system.

STAT5 inhibition induces TRAIL/DR4 dependent apoptosis in peripheral T-cell lymphoma.

Peripheral T-cell lymphoma (PTCL) is a rare, aggressive, heterogeneous, Non-Hodgkin's lymphoma with poor prognosis and inadequate response to current therapies. Recent sequencing studies indicate a prevalence of activating mutations in the JAK/STAT signaling pathway. Oncogenic mutations in STAT5B, observed in approximately one third of cases of multiple different PTCL subtypes, correlate with inferior patient outcomes. Therefore, interest in the development of therapeutic strategies for targeting STAT5 in PTCL is warranted. In this study, we show that the drug pimozide inhibits STAT5 in PTCL, leading to apoptotic cell death by means of the TRAIL/DR4 dependent extrinsic apoptotic pathway. Pimozide induced PTCL cell death is caspase 8 dependent, increases the expression of the TRAIL receptor, DR4, on the surface of pre-apoptotic PTCL cells, and enhances TRAIL induced apoptosis in a TRAIL dependent manner. In parallel, we show that mRNA and protein levels of intrinsic pathway BCL-2 family members and mitochondrial membrane potential remain unaffected by STAT5 knockdown and/or inhibition. In primary PTCL patient samples, pimozide inhibits STAT5 activation and induces apoptosis. Our data support a role for STAT5 inhibition in PTCL and implicate potential utility for inhibition of STAT5 and activation of the extrinsic apoptotic pathway as combination therapy in PTCL.

27 CLINICAL AND GENOMIC CORRELATES OF NEUTROPHIL GRANULOCYTE-MACROPHAGE COLONY STIMULATING FACTOR SIGNALING IN PEDIATRIC CROHN DISEASE

Neutralizing Granulocyte-Macrophage Colony Stimulating Factor auto-antibodies (GMAb) suppress neutrophil extrinsic GM-CSF signaling and increase risk for stricturing behavior in Crohn’s Disease (CD). We aimed to define clinical, genomic, and functional associations with neutrophil intrinsic GM-CSF signaling in pediatric-onset CD. Missense mutations in CSF2RA, CSF2RB, JAK2, STAT5A, and STAT5B were identified using whole exome sequencing (WES) in 543 pediatric Inflammatory Bowel Disease (IBD) patients. Neutrophil intrinsic GM-CSF signaling was defined using the GM-CSF induced STAT5 stimulation index (GMSI) in 180 pediatric IBD patients and 26 non-IBD controls. Reduced GM-CSF signaling (GMSI Lo) was defined as the 20th percentile within the control group. Variation in neutrophil phospho-protein abundance, bacterial killing, and the global pattern of gene expression with the GMSI was determined. We validated 18 potentially damaging missense mutations in CSF2RA and CSF2RB. CSF2RA A17G carriage increased from 10% in those with intact neutrophil GMSI to 32% in those with low GMSI (p=0.02). The frequency of reduced Staph Aureus killing increased from 17% in in those with intact neutrophil GMSI to 35% in GMSI Lo neutrophils (p=0.043). CD neutrophils with low GMSI exhibited specific alterations in phospho-protein networks and genes regulating cytokine production, wound healing, and cell survival and proliferation. Stricturing behavior increased from 7% in CD patients with both low GMAb and intact GMSI to 64% in patients with both elevated GMAb and low GMSI (p<0.0001). Low normal neutrophil intrinsic GM-CSF signaling is associated with CSF2RA missense mutations, alterations in cellular phospho-protein and gene expression networks, and higher rates of disease complications in pediatric CD. These data may inform new therapeutic approaches including ex vivo priming of myeloid cells by GM-CSF.

Hepatosplenic T-cell Lymphoma: a review of clinicopathologic features, pathogenesis, and prognostic factors

Hepatosplenic T-cell lymphoma (HSTCL) is a rare and clinically aggressive type of T-cell lymphoma that arises most often in adolescents and young adults. Patients with HSTCL commonly present with B-symptoms and cytopenias, which may suggest a diagnosis of acute leukemia initially. Patients present with extranodal disease involving the spleen, liver and bone marrow; lymphadenopathy is usually absent. The lymphoma cells can show a spectrum of cell sizes and are of T-cell lineage, often negative for CD4 and CD8 and positive for T-cell receptor γδ or, less often, αβ. Recent studies have identified gene mutations in oncogenic pathways that are likely involved in pathogenesis and may be targets for therapy. Mutations in STAT3 or STAT5B lead to activation of the JAK/STAT pathway, and mutations involving SETD2, IN080 and ARID1 are involved in chromatin modification. Currently, there is no consensus standard of care for HSTCL patients, although several studies support a role for allogeneic hematopoietic stem cell transplant. Although patients with HSTCL are best treated in the context of clinical trials, the rarity of these neoplasms likely necessitates a multi-institutional approach. In this review, we focus on the clinicopathologic and genetic characteristics of HSTCL. We also discuss the differential diagnosis and therapeutic approaches.

27 CLINICAL AND GENOMIC CORRELATES OF NEUTROPHIL GRANULOCYTE-MACROPHAGE COLONY STIMULATING FACTOR SIGNALING IN PEDIATRIC CROHN DISEASE

Neutralizing Granulocyte-Macrophage Colony Stimulating Factor auto-antibodies (GMAb) suppress neutrophil extrinsic GM-CSF signaling and increase risk for stricturing behavior in Crohn’s Disease (CD). We aimed to define clinical, genomic, and functional associations with neutrophil intrinsic GM-CSF signaling in pediatric-onset CD. Missense mutations in CSF2RA, CSF2RB, JAK2, STAT5A, and STAT5B were identified using whole exome sequencing (WES) in 543 pediatric Inflammatory Bowel Disease (IBD) patients. Neutrophil intrinsic GM-CSF signaling was defined using the GM-CSF induced STAT5 stimulation index (GMSI) in 180 pediatric IBD patients and 26 non-IBD controls. Reduced GM-CSF signaling (GMSI Lo) was defined as the 20th percentile within the control group. Variation in neutrophil phospho-protein abundance, bacterial killing, and the global pattern of gene expression with the GMSI was determined. We validated 18 potentially damaging missense mutations in CSF2RA and CSF2RB. CSF2RA A17G carriage increased from 10% in those with intact neutrophil GMSI to 32% in those with low GMSI (p=0.02). The frequency of reduced Staph Aureus killing increased from 17% in in those with intact neutrophil GMSI to 35% in GMSI Lo neutrophils (p=0.043). CD neutrophils with low GMSI exhibited specific alterations in phospho-protein networks and genes regulating cytokine production, wound healing, and cell survival and proliferation. Stricturing behavior increased from 7% in CD patients with both low GMAb and intact GMSI to 64% in patients with both elevated GMAb and low GMSI (p<0.0001). Low normal neutrophil intrinsic GM-CSF signaling is associated with CSF2RA missense mutations, alterations in cellular phospho-protein and gene expression networks, and higher rates of disease complications in pediatric CD. These data may inform new therapeutic approaches including ex vivo priming of myeloid cells by GM-CSF.

Somatic STAT3 mutations in Felty syndrome: an implication for a common pathogenesis with large granular lymphocyte leukemia.

Felty syndrome is a rare disease defined by neutropenia, splenomegaly, and rheumatoid arthritis. Sometimes the differential diagnosis between Felty syndrome and large granular lymphocyte leukemia is problematic. Recently, somatic STAT3 and STAT5B mutations were discovered in 30–40% of patients with large granular lymphocyte leukemia. Herein, we aimed to study whether these mutations can also be detected in Felty syndrome, which would imply the existence of a common pathogenic mechanism between these two disease entities. We collected samples and clinical information from 14 Felty syndrome patients who were monitored at the rheumatology outpatient clinic for Felty syndrome. Somatic STAT3 mutations were discovered in 43% (6/14) of Felty syndrome patients with deep amplicon sequencing targeting all STAT3 exons. Mutations were located in the SH2 domain of STAT3, which is a known mutational hotspot. No STAT5B mutations were found. In blood smears, overrepresentation of large granular lymphocytes was observed, and in the majority of cases the CD8+ T-cell receptor repertoire was skewed when analyzed by flow cytometry. In bone marrow biopsies, an increased amount of phospho-STAT3 positive cells was discovered. Plasma cytokine profiling showed that ten of the 92 assayed cytokines were elevated both in Felty syndrome and large granular lymphocyte leukemia, and three of these cytokines were also increased in patients with uncomplicated rheumatoid arthritis. In conclusion, somatic STAT3 mutations and STAT3 activation are as frequent in Felty syndrome as they are in large granular lymphocyte leukemia. Considering that the symptoms and treatment modalities are also similar, a unified reclassification of these two syndromes is warranted.

STAT5BN642H is a driver mutation for T cell neoplasia.

STAT5B is often mutated in hematopoietic malignancies. The most frequent STAT5B mutation, Asp642His (N642H), has been found in over 90 leukemia and lymphoma patients. Here, we used the Vav1 promoter to generate transgenic mouse models that expressed either human STAT5B or STAT5BN642H in the hematopoietic compartment. While STAT5B-expressing mice lacked a hematopoietic phenotype, the STAT5BN642H-expressing mice rapidly developed T cell neoplasms. Neoplasia manifested as transplantable CD8+ lymphoma or leukemia, indicating that the STAT5BN642H mutation drives cancer development. Persistent and enhanced levels of STAT5BN642H tyrosine phosphorylation in transformed CD8+ T cells led to profound changes in gene expression that were accompanied by alterations in DNA methylation at potential histone methyltransferase EZH2-binding sites. Aurora kinase genes were enriched in STAT5BN642H-expressing CD8+ T cells, which were exquisitely sensitive to JAK and Aurora kinase inhibitors. Together, our data suggest that JAK and Aurora kinase inhibitors should be further explored as potential therapeutics for lymphoma and leukemia patients with the STAT5BN642H mutation who respond poorly to conventional chemotherapy.