Mithun Vinod Shah

Network model of survival signaling in large granular lymphocyte leukemia

T cell large granular lymphocyte (T-LGL) leukemia features a clonal expansion of antigen-primed, competent, cytotoxic T lymphocytes (CTL). To systematically understand signaling components that determine the survival of CTL in T-LGL leukemia, we constructed a T-LGL survival signaling network by integrating the signaling pathways involved in normal CTL activation and the known deregulations of survival signaling in leukemic T-LGL. This network was subsequently translated into a predictive, discrete, dynamic model. Our model suggests that the persistence of IL-15 and PDGF is sufficient to reproduce all known deregulations in leukemic T-LGL. This finding leads to the following predictions: (i) Inhibiting PDGF signaling induces apoptosis in leukemic T-LGL. (ii) Sphingosine kinase 1 and NFκB are essential for the long-term survival of CTL in T-LGL leukemia. (iii) NFκB functions downstream of PI3K and prevents apoptosis through maintaining the expression of myeloid cell leukemia sequence 1. (iv) T box expressed in T cells (T-bet) should be constitutively activated concurrently with NFκB activation to reproduce the leukemic T-LGL phenotype. We validated these predictions experimentally. Our study provides a model describing the signaling network involved in maintaining the long-term survival of competent CTL in humans. The model will be useful in identifying potential therapeutic targets for T-LGL leukemia and generating long-term competent CTL necessary for tumor and cancer vaccine development.

Molecular profiling of LGL leukemia reveals role of sphingolipid signaling in survival of cytotoxic lymphocytes

T-cell large granular lymphocyte (LGL) leukemia is characterized by clonal expansion of CD3(+)CD8(+) cells. Leukemic LGLs correspond to terminally differentiated effector-memory cytotoxic T lymphocytes (CTLs) that escape Fas-mediated activation-induced cell death (AICD) in vivo. The gene expression signature of peripheral blood mononuclear cells from 30 LGL leukemia patients showed profound dysregulation of expression of apoptotic genes and suggested uncoupling of activation and apoptotic pathways as a mechanism for failure of AICD in leukemic LGLs. Pathway-based microarray analysis indicated that balance of proapoptotic and antiapoptotic sphingolipid-mediated signaling was deregulated in leukemic LGLs. We further investigated sphingolipid pathways and found that acid ceramidase was constitutively overexpressed in leukemic LGLs and that its inhibition induced apoptosis of leukemic LGLs. We also showed that S1P(5) is the predominant S1P receptor in leukemic LGLs, whereas S1P(1) is down-regulated. FTY720, a functional antagonist of S1P-mediated signaling, induced apoptosis in leukemic LGLs and also sensitized leukemic LGLs to Fas-mediated death. Collectively, these results show a role for sphingolipid-mediated signaling as a mechanism for long-term survival of CTLs. Therapeutic targeting of this pathway, such as use of FTY720, may have efficacy in LGL leukemia.

Therapeutic efficacy of FTY720 in a rat model of NK-cell leukemia

NK-cell leukemia is a clonal expansion of NK cells. The illness can occur in an aggressive or chronic form. We studied cell lines from human and rat NK-cell leukemias (aggressive NK-cell leukemia) as well as samples from patients with chronic NK-cell leukemia to investigate pathogenic mechanisms. Here we report that Mcl-1 was overexpressed in leukemic NK cells and that knockdown of Mcl-1 induced apoptosis in these leukemic cells. In vitro treatment of human and rat NK leukemia cells with FTY720 led to caspase-dependent apoptosis and decreased Mcl-1 expression in a time- and-dose-dependent manner. These biologic effects could be inhibited by blockade of reactive oxygen species generation and the lysosomal degradation pathway. Lipidomic analyses after FTY720 treatment demonstrated elevated levels of sphingosine, which mediated apoptosis of leukemic NK cells in vitro. Importantly, systemic administration of FTY720 induced complete remission in the syngeneic Fischer rat model of NK-cell leukemia. Therapeutic efficacy was associated with decreased expression of Mcl-1 in vivo. These data demonstrate that therapeutic benefit of FTY720 may result from both altered sphingolipid metabolism as well as enhanced degradation of a key component of survival signaling.

The root of many evils: indolent large granular lymphocyte leukaemia and associated disorders.

Large granular lymphocytes (LGL) leukaemia can arise from either natural killer (NK) cells or cytotoxic T lymphocytes (CTL). The T‐cell form of LGL leukaemia has significant overlap with other haematological disorders and autoimmune diseases. Here we provide an overview of LGL biology. We also focus discussion on the indolent LGL leukaemia related disorders and their causal relationships. We then discuss the potential relationships and distinctions between indolent LGL leukaemia and non‐malignant clonal lymphocyte expansion that occur in otherwise healthy individuals, especially elder people. Copyright

Acid ceramidase is upregulated in AML and represents a novel therapeutic target

There is an urgent unmet need for new therapeutics in acute myeloid leukemia (AML) as standard therapy has not changed in the past three decades and outcome remains poor for most patients. Sphingolipid dysregulation through decreased ceramide levels and elevated sphingosine 1-phosphate (S1P) promotes cancer cell growth and survival. Acid ceramidase (AC) catalyzes ceramide breakdown to sphingosine, the precursor for S1P. We report for the first time that AC is required for AML blast survival. Transcriptome analysis and enzymatic assay show that primary AML cells have high levels of AC expression and activity. Treatment of patient samples and cell lines with AC inhibitor LCL204 reduced viability and induced apoptosis. AC overexpression increased the expression of anti-apoptotic Mcl-1, significantly increased S1P and decreased ceramide. Conversely, LCL204 induced ceramide accumulation and decreased Mcl-1 through post-translational mechanisms. LCL204 treatment significantly increased overall survival of C57BL/6 mice engrafted with leukemic C1498 cells and significantly decreased leukemic burden in NSG mice engrafted with primary human AML cells. Collectively, these studies demonstrate that AC plays a critical role in AML survival through regulation of both sphingolipid levels and Mcl-1. We propose that AC warrants further exploration as a novel therapeutic target in AML.

Epigenetic therapy overcomes treatment resistance in T cell prolymphocytic leukemia

Epigenetic drugs can overcome resistance to monoclonal antibodies in T-PLL and activate therapeutic targets for antibody-drug conjugates. A second chance for leukemia therapy T cell prolymphocytic leukemia (T-PLL) is a rare and aggressive type of leukemia, which is usually difficult to treat. Alemtuzumab, a monoclonal anti-CD52 antibody, is currently used to treat this disease, but patients quickly develop resistance to alemtuzumab or do not respond to it altogether. Now, Hasanali et al. show that epigenetic therapy can help overcome drug resistance in T-PLL patients. In addition, the epigenetic drugs frequently up-regulated CD30 on the surface of leukemia cells, which allowed subsequent successful treatment with brentuximab vedotin, an antibody-drug conjugate targeting CD30. The findings suggest a new treatment regimen for this challenging disease and demonstrate a potential approach to successfully combining epigenetic and immunotherapy. T cell prolymphocytic leukemia (T-PLL) is a rare, mature T cell neoplasm with distinct features and an aggressive clinical course. Early relapse and short overall survival are commonplace. Use of the monoclonal anti-CD52 antibody alemtuzumab has improved the rate of complete remission and duration of response to more than 50% and between 6 and 12 months, respectively. Despite this advance, without an allogeneic transplant, resistant relapse is inevitable. We report seven complete and one partial remission in eight patients receiving alemtuzumab and cladribine with or without a histone deacetylase inhibitor. These data show that administration of epigenetic agents can overcome alemtuzumab resistance. We also report epigenetically induced expression of the surface receptor protein CD30 in T-PLL. Subsequent treatment with the anti-CD30 antibody–drug conjugate brentuximab vedotin overcame organ-specific (skin) resistance to alemtuzumab. Our findings demonstrate activity of combination epigenetic and immunotherapy in the incurable illness T-PLL, particularly in the setting of previous alemtuzumab therapy.

Never Say Die: Survival Signaling in Large Granular Lymphocyte Leukemia

Large granular lymphocyte (LGL) leukemia is a rare disorder of mature cytotoxic T or natural killer cells. Large granular lymphocyte leukemia is characterized by the accumulation of cytotoxic cells in blood and infiltration in the bone marrow, liver, and spleen. Herein, we review clinical features of LGL leukemia. We focus our discussion on known survival signals believed to play a role in the pathogenesis of LGL leukemia and their potential therapeutic implications.

Haploidentical Transplantation for Older Patients with Acute Myeloid Leukemia and Myelodysplastic Syndrome

Allogeneic stem cell transplantation with HLA-matched donors is increasingly used for older patients with acute myeloid leukemia (AML) and myelodysplastic syndrome (MDS). It remains unclear if haploidentical stem cell transplantation (haploSCT) is a suitable option for older patients with this disease. We analyzed 43 patients with AML/MDS (median age, 61 years) who underwent a haploSCT at our institution. All patients received a fludarabine-melphalan-based reduced-intensity conditioning regimen and post-transplant cyclophosphamide-based graft-versus-host disease (GVHD) prophylaxis. Except for 1 patient who had early death, the remaining 42 patients (98%) engrafted donor cells. The cumulative incidences of grades II to IV and III to IV acute GVHD at 6 months were 35% and 5%, respectively, and chronic GVHD at 2 years was 9%. After a median follow-up of 19 months, 2-year overall survival, progression-free survival (PFS), and relapse incidence were 42%, 42%, and 24%, respectively. Best PFS (74% at 2 years) was seen in patients with intermediate-/good-risk cytogenetics, in first or second remission (hazard ratio, .4; P = .05), and with a younger donor (≤40 years; hazard ratio, .2; P = .01). In conclusion, these data suggest that haploidentical transplantation is safe and effective for older AML/MDS patients. Disease status, cytogenetics, and younger donor age are predictors for improved survival in older patients receiving a haploidentical transplant.

Clinical and Radiologic Responses to Cladribine for the Treatment of Erdheim-Chester Disease

Importance While cladribine is best known for the treatment of hairy cell leukemia and other lymphoid cancers, it also has activity against myeloid neoplasms, such as Erdheim-Chester disease (ECD). Objective To assess the efficacy of cladribine (2-chloro-2′-deoxyadenosine) in the treatment of ECD. Design, Setting, and Participants This study was a single-institution retrospective medical record review from January 1, 1998, to April 6, 2016, at a tertiary academic medical center. In all eligible cases, the diagnosis of ECD was made using clinical criteria in conjunction with histopathologic findings. Exposure Cladribine therapy in first-line treatment or later. Main Outcomes and Measures Two response criteria were used, clinical and radiological. For clinical response, the following criteria were used: complete response (complete resolution of symptoms attributed to ECD), partial response (partial resolution of symptoms attributed to ECD), stable disease (no change in symptoms attributed to ECD), and progressive disease (worsening of symptoms attributed to ECD). For radiological response, the following categories were used: complete response (complete resolution of proven or suspected lesion due to ECD), partial response (partial resolution of proven or suspected lesion due to ECD), stable disease (no significant change in proven or suspected lesion due to ECD for ≥3 months), and progressive disease (progression or worsening of proven or suspected lesion due to ECD). Results A total of 63 adult patients with confirmed ECD were identified. Their median age at diagnosis of ECD was 54 years (age range, 18-80 years), and 67% (42 of 63) were male. Cladribine was the most commonly used chemotherapeutic agent and was administered in 21 of 63 patients (33%). Their median age at the time of cladribine therapy was 62 years (age range, 40-78 years). Cladribine was used as the first-line treatment in 9 patients and as later-line treatment in the remaining 12 patients. The median number of cycles of cladribine administered was 2.5 (range, 1-6). The overall clinical response rate was 52% (9 of 17) (6% [1 of 17] complete response and 46% [8 of 17] partial response), with 18% (3 of 17) stable disease and 30% (5 of 17) progressive disease. Among patients who responded to cladribine therapy, the median duration of clinical response was 9 months (range, 6-129 months), with ongoing response in 2 patients. The overall radiological response rate was 54% (8 of 15) (all partial response), with 26% (4 of 15) stable disease and 20% (2 of 15) progressive disease. Treatment-related adverse effects included 2 infectious complications (pneumonia and central line infection, both requiring hospitalization) and 2 hematologic adverse effects (grade 4 neutropenia and thrombocytopenia, and grade 3 neutropenia, both requiring therapy discontinuation). Conclusions and Relevance Cladribine has moderate clinical efficacy in the treatment of ECD and can be considered a treatment option in cases without the BRAF V600E mutation. It is generally well tolerated and may result in a durable response.

A population-based study of large granular lymphocyte leukemia

Large granular lymphocyte (LGL) leukemia is a lymphoproliferative disorder of cytotoxic cells. T-cell LGL (T-LGL) leukemia is characterized by accumulation of cytotoxic T cells in blood and infiltration of the bone marrow, liver or spleen. Population-based studies have not been reported in LGL leukemia. We present clinical characteristics, natural history and risk factors for poor survival in patients with LGL leukemia using the Surveillance, Epidemiology, and End Results Program (SEER) and the United States National Cancer Data Base (NCDB). LGL leukemia is an extremely rare disease with the incidence of 0.2 cases per 1 000 000 individuals. The median age at diagnosis was 66.5 years with females likely to be diagnosed at 3 years earlier compared with males. Analysis of patient-level data using NCDB (n=978) showed that 45% patients with T-LGL leukemia required some form of systemic treatment at the time of diagnosis. T-LGL leukemia patients have reduced survival compared with general population, with a median overall survival of 9 years. Multivariate analysis showed that age >60 years at the time of diagnosis and the presence of significant comorbidities were independent predictors of poor survival.