A lineage-specific STAT5BN642H mouse model to study NK-cell leukemia.

ABSTRACT: Patients with T- and natural killer (NK)-cell neoplasms frequently have somatic STAT5B gain-of-function mutations. The most frequent STAT5B mutation is STAT5BN642H, which is known to drive murine T-cell leukemia, although its role in NK-cell malignancies is unclear. Introduction of the STAT5BN642H mutation into human NK-cell lines enhances their potential to induce leukemia in mice. We have generated a mouse model that enables tissue-specific expression of STAT5BN642H and have selectively expressed the mutated STAT5B in hematopoietic cells (N642Hvav/+) or exclusively in NK cells (N642HNK/NK). All N642Hvav/+ mice rapidly develop an aggressive T/NKT-cell leukemia, whereas N642HNK/NK mice display an indolent NK-large granular lymphocytic leukemia (NK-LGLL) that progresses to an aggressive leukemia with age. Samples from patients with NK-cell leukemia have a distinctive transcriptional signature driven by mutant STAT5B, which overlaps with that of murine leukemic N642HNK/NK NK cells. To our knowledge, we have generated the first reliable STAT5BN642H-driven preclinical mouse model that displays an indolent NK-LGLL progressing to aggressive NK-cell leukemia. This novel in vivo tool will enable us to explore the transition from an indolent to an aggressive disease and will thus permit the study of prevention and treatment options for NK-cell malignancies.

Clinical features and prognosis of chronic natural killer cell lymphoproliferative disorders.

OBJECTIVE: To analyze the current treatment status and prognostic regression of the chronic NK cell lymphoproliferative disorder (CLPD-NK). METHODS: We retrospectively analyzed the clinical features, treatment and prognosis of 18 patients with CLPD-NK who were treated at our Hospital between September 2016 and September 2022. RESULTS: Eighteen patients were included: three patients were treated with chemotherapy, five patients underwent immune-related therapy, one patient was treated with glucocorticoids alone, five patients were administered granulocyte colony-stimulating factor, blood transfusion therapy, or anti-infection therapy, followed by observation and follow-up, and four patients were observed without treatment. Fifteen patients survived, including two patients who achieved complete remission (CR) and seven patients who achieved partial remission (PR), of whom one patient progressed to Aggressive NK-cell leukemia (ANKL) and sustained remission after multiple lines of treatment; three patients were not reviewed, of which one patient was still in active disease, three patients developed hemophagocytic syndrome during treatment and eventually died, one of them had positive Epstein-Barr virus (EBV) expression. The 5-years overall survival rate was 83%. CONCLUSION: Most patients with CLPD-NK have inert progression and a good prognosis, whereas some patients have a poor prognosis after progressing to ANKL and combined with hemophagocytic syndrome. Abnormal NK cells invading the center suggest a high possibility of ANKL development, and immunosuppressants and hormones are effective treatments for this disease.

The constitutive activation of STAT3 gene and its mutations are at the crossroad between LGL leukemia and autoimmune disorders.

Type T Large Granular Lymphocyte Leukemia (T-LGLL) is a chronic disorder characterized by the abnormal proliferation of clonal cytotoxic T cells. The intriguing association of T-LGLL with autoimmune and inflammatory diseases, the most prominent example being rheumatoid arthritis, raises questions about the underlying pathophysiologic relationships between these disorders which share several biological and clinical features, most notably neutropenia, which is considered as a clinical hallmark. Recent progress in molecular genetics has contributed to a better understanding of pathogenetic mechanisms, thus moving our knowledge in the field of LGL leukemias forward. Focusing on the constitutive activation of STAT3 pathway and the well-established role of STAT3 mutations in T-LGLL, we herein discuss whether the T cell clones occurring in comorbid conditions are the cause or the consequence of the immune-inflammatory associated events. Overall, this review sheds light on the intricate relationships between inflammation and cancer, emphasizing the importance of the STAT3 gene and its activation in the pathophysiology of these conditions. Gaining a deeper understanding of these underlying mechanisms seeks to pave the way for the development of novel targeted therapies for patients affected by inflammation-related cancers.

Pro-inflammatory cells sustain leukemic clonal expansion in T-cell large granular lymphocyte leukemia.

T-cell large granular lymphocyte leukemia (T-LGLL) is a chronic lymphoproliferative disorder characterized by the clonal expansion of T-cell large granular lymphocytes (T-LGL). Immunophenotypic and genotypic features contribute to discriminate symptomatic (CD8+ STAT3-mutated T-LGLL) from clinically indolent patients, this latter group including CD8+ wildtype (wt), CD4+ STAT5B-mutated and wt cases. T-LGL lymphoproliferation is sustained both by somatic gain-offunction mutations (i.e., STAT3 and STAT5B) and by pro-inflammatory cytokines, but little information is available on the activity of T-LGLL non-leukemic cells. In this study, we characterized pro-inflammatory cells in the peripheral blood of T-LGLL patients and analyzed their role in supporting the leukemic growth. In symptomatic patients we found that cell populations not belonging to the leukemic component showed a discrete pro-inflammatory pattern. In particular, CD8+ STAT3-mutated cases showed a skewed Th17/Treg ratio and an abnormal distribution of monocyte populations characterized by increased intermediate and non-classical monocytes. We also demonstrated that monocytes released high levels of interleukin-6 after CCL5 stimulation, a chemokine specifically expressed only by leukemic LGL. Conversely, in asymptomatic cases an altered distribution of monocyte populations was not detected. Moreover, T-LGLL patients' monocytes showed abnormal activation of signaling pathways, further supporting the different pathogenic role of monocytes in patients in discrete clinical settings. Altogether, our data contribute to deepening the knowledge on the different cell subtypes in T-LGLL, focusing particularly on non-leukemic cell populations and thus offering the rationale for new therapeutic strategies.

Prevalence of STAT3 mutations in patients with rheumatoid arthritis-associated T-cell large granular lymphocytic leukaemia and Felty syndrome.

OBJECTIVES: Neutropenia is a key presentation of Felty syndrome (FS) and rheumatoid arthritis (RA)-associated T-cell large granular lymphocytic (T-LGL) leukaemia. Clonal rearrangement of T-cell receptor (TCR) gene supports the diagnosis of T-LGL leukaemia but not FS. Mutations in the signal transducer and activator of transcription 3 (STAT3) gene are highly specific for T-LGL leukaemia, but their prevalence in FS remains poorly clarified. METHODS: The study included 100 patients with RA and unexplained neutropenia. TCR rearrangements were examined in blood (100 cases), bone marrow (47 cases), and spleen (12 cases) using the BIOMED-2 protocol. Patients were stratified into RA-associated T-LGL leukaemia cohort if a clonal TCR rearrangement was identified in any of the tested patient samples, and into FS cohort in other cases. Mutations in the STAT3 were examined using next-generation sequencing (NGS) technology in blood (100 cases), bone marrow (37 cases), and spleen (7 cases). RESULTS: STAT3 mutations were identified in 71% (49/69) patients with RA-associated T-LGL leukaemia and in 10% (3/31) patients with FS (p=4.7×10-8). Three samples from the RA-associated T-LGL leukaemia cohort and 5 samples from the FS cohort had STAT3 mutations in the absence of clonal TCR rearrangement. CONCLUSIONS: The results suggest that STAT3 mutations are significantly less common in FS than in RA-associated T-LGL leukaemia. Moreover, NGS can detect clones undetectable by fragment analysis. We speculate that in patients with RA and neutropenia, the detection of STAT3 mutations can point to T-LGL leukaemia even in the absence of clonal TCR rearrangement.

TOX as a new diagnostic marker for T cell large granular lymphocytic leukaemia.

AIMS: T cell large granular lymphocytic leukaemia (T-LGLL) is a rare disorder that may underlie otherwise unexplained cytopenias. The identification of T-LGLL cells in bone marrow biopsies can be a challenge, because a robust immunohistochemistry marker is lacking. The markers currently in use (granzyme B, TIA-1 and CD8) are difficult to interpret or lack specificity. Therefore, we investigated whether immunohistochemistry for thymocyte selection-associated high-mobility group box (TOX), a transcription factor that associates with chronic T cell stimulation, could be a reliable tool for the identification of T-LGLL cells. METHODS AND RESULTS: In this retrospective study, expression of TOX in CD8+ cells in bone marrow biopsies of T-LGLL patients (n = 38) was investigated and compared to bone marrow of controls with reactive T cell lymphocytosis (n = 10). All biopsies were evaluated for TOX staining within the CD8-positive T cell population. The controls were essentially negative for TOX, whereas all T-LGLL cases were positive (median = 80%, range = 10-100%), even when bone marrow involvement was subtle. CONCLUSION: TOX is a highly sensitive marker for the neoplastic cells of T-LGLL and we recommend its use, especially in the diagnostic work-up of patients with unexplained cytopenias.

Clinical characteristics and treatment outcomes of Asian patients with T-cell large granular lymphocytic Leukemia: a single-center analysis of 67 cases.

Large granular lymphocytic (LGL) leukemia is a clonal lymphoproliferative disorder of LGLs derived from cytotoxic T lymphocytes or natural killer cells. However, the clinical features and treatment responses are still not fully understood because of the rarity of the disease. To describe and assess a cohort of patients with T-cell large granular lymphocytic leukemia (T-LGLL). Single-center, retrospective, observational study. We retrospectively collected the clinical data of patients diagnosed with T-LGLL at Seoul National University Hospital since 2006. We included 67 patients in this study. The median age at diagnosis was 60 years. Additionally, 37 patients (55%) were symptomatic, and 25 (37%) had splenomegaly; 54 patients (81%) required treatment. Cyclophosphamide (n = 35), methotrexate (n = 25), and cyclosporin A (n = 19) were used most frequently for treatment, and their overall response rates were similar: cyclophosphamide (77%), methotrexate (64%), and cyclosporin A (63%). Splenomegaly was associated with an increased response rate to first-line therapy and a decreased complete response rate. Thrombocytopenia was associated with decreased response rates to cyclophosphamide, methotrexate, cyclosporin A, and steroids. In contrast, a high LGL number (> 2000/µL) in the peripheral blood smear was associated with increased response rates to cyclophosphamide, methotrexate, cyclosporin A, and steroids. This study describes the clinical features and treatment outcomes of patients with T-LGLL, providing valuable information for clinical decision-making regarding T-LGLL treatment.

T-cell large granular lymphocytic leukemia in Vietnam: Using microscope-to-screen videoconferencing to improve diagnosis.

OBJECTIVES: Leukemia diagnosis in Vietnam is limited by a lack of hematopathology training and expert consultation as well as the cost of high-magnification digitization of hematology slides. Screen-sharing software allows international collaboration with experienced hematopathologists for improved diagnostic accuracy. METHODS: A hematopathology education and consultation program was proposed for Vietnam hospitals. By appointment, pathologists in Vietnam with access to a microscope camera, imaging software, and high-speed internet were invited to review slides and data with a volunteer board-certified hematopathologist in the United States using secure videoconferencing software. A single hospital in southern Vietnam assigned a pathologist proficient in English to access this service. All consultations from this site with clinicopathologic information were logged. After a 2-year period of online consultation, case slides for selected diagnoses were reviewed under the microscope in Vietnam to assess concordance. RESULTS: In total, 135 consultations were logged, 53 of which were for blood and bone marrow. T-cell large granular lymphocytic leukemia (T-LGLL) was 1 of the most frequent bone marrow consultation-related diagnoses; all diagnoses of this entity were confirmed by in-person microscopy (100% concordance). A records search and physician surveys found no prior documented diagnoses of T-LGLL made in Vietnam before this education and consultation program. CONCLUSIONS: Our virtual consultation model has improved patient care in Vietnam by providing correct diagnoses to inform best practices in treatment. As a result of our program, the first Vietnam diagnoses of T-LGLL were made and may help expand on the literature in this area. This model could provide cost-effective, real-time consultation and education services for pathologists in underserved communities.

The complex relationship between large granular lymphocyte leukemia and rheumatic disease.

INTRODUCTION: Large granular lymphocytic (LGL) leukemia is a rare lymphoproliferative disorder characterized by an expansion of clonal T or NK lymphocytes. Neutropenia-related infections represent the main clinical manifestation. Even if the disease follows an indolent course, most patients will ultimately need treatment in their lifetime. Interestingly, LGL leukemia is characterized by a high frequency of autoimmune disorders with rheumatoid arthritis being the most frequent. AREAS COVERED: This review covers the pathophysiology, clinic-biological features and the advances made in the treatment of LGL leukemia. A special focus will be made on the similarities in the pathophysiology of LGL leukemia and the frequently associated rheumatic disorders. EXPERT OPINION: Recent advances in the phenotypic and molecular characterization of LGL clones have uncovered the key role of JAK-STAT signaling in the pathophysiology linking leukemic cells expansion and autoimmunity. The description of the molecular landscape of T- and NK-LGL leukemia and the improved understanding of the associated rheumatic disorders open the way to the development of new targeted therapies effective on both conditions.

A simplified prognostic score for T-cell large granular lymphocyte leukaemia.

BACKGROUND: T-cell large granular lymphocyte leukaemia (T-LGLL) generally has a favourable prognosis, but a small proportion of patients are facing a relatively short survival time. This study aimed to identify clinical factors associated with survival in patients with T-LGLL and develop a predictive model for guiding therapeutic decision-making. MATERIALS AND METHODS: We conducted a retrospective study on 120 patients with T-LGLL. Lasso regression was performed for feature selection followed by univariate and multivariate Cox regression analysis. A decision tree algorithm was employed to construct a model for predicting overall survival (OS) in T-LGLL. RESULTS: The median age of diagnosis for the entire cohort was 59 years, and 76.7% of patients reported disease-related symptoms. After a median follow-up of 75 months, the median OS was not reached. The 5-year OS rate was 82.2% and the 10-year OS rate was 63.8%. Multivariate analysis revealed that an Eastern Cooperative Oncology Group performance status over two and a platelet count below 100 × 109/L were independently associated with worse OS, leading to the development of a simplified decision tree model. The model's performance was adequate when internally validated. The median OS of the high- and intermediate-risk- risk groups was 43 and 100 months respectively, whereas the median OS of the low-risk group was not reached. Furthermore, we found that immunosuppressive agent-based conventional treatment was unsatisfactory for our high-risk patients. CONCLUSIONS: Our model is an easily applicable clinical scoring system for predicting OS in patients with T-LGLL. However, external validation is essential before implementing it widely.

Possible Concomitant Aggressive NK Cell Leukemia and EBV-positive T-cell lymphoma; Using the online beta version of WHO-HAEM5 and videoconferencing software to make diagnoses accessible in an emerging economy.

BACKGROUND: Using the World Health Organization Classification 5th edition (beta version online; WHO-HAEM5bv) in emerging economies is key to global healthcare equity. Although there may be ongoing updates, hesitancy in accepting and reporting these diagnoses in publication conflicts with the WHO's commitment to global accessibility. Aggressive NK cell leukemia (ANKL) and systemic EBV-positive T-cell lymphoma of childhood (SEBVTCL) with CD4-positive immunophenotype are both rare entities, are most described in Asians and East Asians, are associated with prior systemic chronic active EBV disease (CAEBV), and presentation with Hemophagocytic Lymphohistiocytosis (HLH). Recognizing and diagnosing any one of these entities requires not only training and experience in hematopathology, but good cooperation between clinical physicians and all areas of the laboratory. We describe a 30-year-old woman who presented to a Vietnam hospital and was rapidly diagnosed with ANKL, SEBVTCL, and HLH using WHO-HAEM5bv essential criteria, aided by expert consultation from a United States (US) board certified hematopathologist in real-time using video conferencing software. METHODS: Zoom™ videoconferencing software; Immunohistochemistry; flow cytometric immunophenotyping; polymerase chain reaction (PCR), Next Generation Sequencing (NGS). RESULTS: At the time of hospital admission, automated complete blood count (CBC) with differential count showed slight anemia, slight lymphocytosis, and moderate thrombocytopenia. HIV serology was negative. Whole blood PCR for EBV was positive showing 98,000 copies/ml. A lymph node biopsy revealed histology and immunohistochemistry consistent with the online beta version WHO-HAEM5 classification of SEBVTCL arising in CAEBV. Blood and bone marrow studies performed for staging revealed no histologic or immunohistochemical evidence of T-cell lymphoma in the bone marrow core, however, atypical blood smear lymphocyte morphology and blood immunophenotyping by flow cytometry were consistent with WHO-HAEM5 classification of ANKL. NGS revealed no evidence of genetic variant(s) associated with HLH in Vietnam. All laboratory studies were performed at Blood Transfusion Hematology Hospital (BTHH) in Ho Chi Minh City Vietnam. CONCLUSION: Although Vietnam, an emerging economy, currently lacks the laboratory infrastructure to more rigorously confirm a rare synchronous presentation of two distinct EBV-driven T/NK cell neoplasms, these two concomitant diagnoses were made using only laboratory techniques available in Vietnam with the help of WHO-HAEM5bv and real-time video consultation by a US hematopathologist.

[Large granular lymphocytic leukemia and its association with immune dysregulation].

Large granular lymphocytic (LGL) leukemia is a chronic lymphoproliferative disease of cytotoxic T cells or NK cells with LGL morphology and frequently complicated cytopenia and/or different autoimmune diseases, which often require medical interventions, although LGL leukemia itself is seldom lethal. Immunologic dysregulations in LGL leukemia contribute to the development of complications, for example, neutropenia with the involvement of Fas ligand system and, in pure red cell aplasia, which is a common complication among the patients of East Asian origin, impairing erythroid developments by cytotoxic T cells. Rheumatoid arthritis (RA) is the most prevalent nonhematological consequence, and Felty syndrome, a rare form of RA, and T-LGL leukemia have a lot in common. When patients have LGL leukemia-associated complications, immunosuppressive medication is a mainstay of treatment. Characteristic mutational features in STAT3, STAT5B, CCL22, and other genes in specific subtypes of LGL leukemia have been detected, that would be associated with immunologically mediated molecular pathogenesis in LGL leukemia, and these new findings may help in creating optimal diagnostic approaches or novel therapies for LGL leukemia.

[Clinical Characteristics of Aggressive NK-Cell Leukemia].

OBJECTIVE: To explore and summarize the clinical characteristics and treatment of aggressive NK-cell leukemia (ANKL), and provide new insights for clinical diagnosis and treatment of this disease. METHODS: The clinical data of 7 patients with ANKL admitted to the First Affiliated Hospital of Wannan Medical College from March 2014 to July 2021 were retrospectively analyzed, and their clinical characteristics, laboratory and imaging results, treatment and outcomes were analyzed. RESULTS: Among the 7 patients, 5 were males and 2 were females, with a median age of 47 (33-69) years old. The morphology of bone marrow cells in 7 patients showed similar large granular lymphocytes. Immunophenotyping revealed abnormal NK cells in 5 cases. By the end of follow-up, 6 cases died and 1 case survived, with a median survival time of 76.9 (4-347) days. CONCLUSION: ANKL is a rare disease with short course and poor prognosis. If combined with hemophagocytic syndrome (HPS), the prognosis is even worse. There is no unified treatment method at present, and the use of PD-1 inhibitors may prolong the survival in some patients.

Genomic landscape of T-large granular lymphocyte leukemia and chronic lymphoproliferative disorder of NK cells: a single institution experience.

LGLL is a rare and chronic lymphoproliferative disorder including T-LGLL and CLPD-NK. Here, we investigated the genomic profiles of LGLL with a focus on STAT3 and STAT5B mutations in a cohort of 49 patients (41 T-LGLL, 8 CLPD-NK). Our study indicated that STAT3 was identified in 38.8% (19/49) of all patients, while STAT5B occurred in only 8.2% (4/49) of patients. We found that STAT3 mutations were associated with lower ANC in T-LGLL patients. The average number of pathogenic/likely pathogenic mutations in STAT3/STAT5B-mutated patients was significantly higher than that in WT patients (1.78 ± 1.17 vs 0.65 ± 1.36, p = 0.0032). Additionally, TET2-only mutated T-LGLL (n = 5) had a significant reduction in platelet values compared with the WT (n = 16) or STAT3-only mutated T-LGLL (n = 12) (p < 0.05). In conclusion, we compared the somatic mutational landscape between STAT3/STAT5B WT and mutated patients and correlate with their distinct clinical characteristics.