Purification Method of Extracellular Vesicles Derived from Human T-Cell Leukemia Virus Type 1-Infected Cells without Virions.

To mediate intercellular communication, cells produce extracellular vesicles (EVs). These EVs transport many biomolecules such as proteins, nucleic acids, and lipids between cells and regulate pathophysiological actions in the recipient cell. However, EVs and virus particles produced from virus-infected cells are of similar size and specific gravity; therefore, the separation and purification of these two particles is often controversial. When analyzing the physiological functions of EVs from virus-infected cells, the presence or absence of virus particle contamination must always be verified. The human T-cell leukemia virus type 1 (HTLV-1)-infected cell line, MT-2, produces EVs and virus particles. Here, we validated a method for purifying EVs from MT-2 cell culture supernatants while avoiding HTLV-1 viral particle contamination. EV fractions were collected using a combination of immunoprecipitation with Tim-4, which binds to phosphatidylserine, and polymer precipitation. The HTLV-1 viral envelope protein, gp46, was not detected in the EV fraction. Proteomic analysis revealed that EV-constituted proteins were predominant in this EV fraction. Furthermore, the EVs were found to contain the HTLV-1 viral genome. The proposed method can purify EVs while avoiding virus particle contamination and is expected to contribute to future research on EVs derived from HTLV-1-infected cells.

Thymic-Epithelial-Cell-Dependent Microenvironment Influences Proliferation and Apoptosis of Leukemic Cells.

T-cell acute lymphoblastic leukemia (T-ALL) is a hematological cancer characterized by the infiltration of immature T-cells in the bone marrow. Aberrant NOTCH signaling in T-ALL is mainly triggered by activating mutations of NOTCH1 and overexpression of NOTCH3, and rarely is it linked to NOTCH3-activating mutations. Besides the known critical role of NOTCH, the nature of intrathymic microenvironment-dependent mechanisms able to render immature thymocytes, presumably pre-leukemic cells, capable of escaping thymus retention and infiltrating the bone marrow is still unclear. An important challenge is understanding how leukemic cells shape their tumor microenvironment to increase their ability to infiltrate and survive within. Our previous data indicated that hyperactive NOTCH3 affects the CXCL12/CXCR4 system and may interfere with T-cell/stroma interactions within the thymus. This study aims to identify the biological effects of the reciprocal interactions between human leukemic cell lines and thymic epithelial cell (TEC)-derived soluble factors in modulating NOTCH signaling and survival programs of T-ALL cells and TECs. The overarching hypothesis is that this crosstalk can influence the progressive stages of T-cell development driving T-cell leukemia. Thus, we investigated the effect of extracellular space conditioned by T-ALL cell lines (Jurkat, TALL1, and Loucy) and TECs and studied their reciprocal regulation of cell cycle and survival. In support, we also detected metabolic changes as potential drivers of leukemic cell survival. Our studies could shed light on T-cell/stroma crosstalk to human leukemic cells and propose our culture system to test pharmacological treatment for T-ALL.

Co-Culture and Transduction of Murine Thymocytes on Delta-Like 4-Expressing Stromal Cells to Study Oncogenes in T-Cell Leukemia.

Transduced mouse immature thymocytes can be differentiated into T cells in vitro using the delta-like 4-expressing bone marrow stromal cell line co-culture system (OP9-DL4). As retroviral transduction requires dividing cells for transgene integration, OP9-DL4 provides a suitable in vitro environment for cultivating hematopoietic progenitor cells. This is particularly advantageous when studying the effects of the expression of a specific gene during normal T cell development and leukemogenesis, as it allows researchers to circumvent the time-consuming process of generating transgenic mice. To achieve successful outcomes, a series of coordinated steps involving the simultaneous manipulation of different types of cells must be carefully performed. Although these are very well-established procedures, the lack of a common source in the literature often means a series of optimizations are required, which can be time-consuming. This protocol has been shown to be efficient in transducing primary thymocytes followed by differentiation on OP9-DL4 cells. Detailed here is a protocol that can serve as a quick and optimized guide for the co-culture of retrovirally transduced thymocytes on OP9-DL4 stromal cells.

Depletion of RNASEH2 Activity Leads to Accumulation of DNA Double-strand Breaks and Reduced Cellular Survivability in T Cell Leukemia.

Ribonuclease H2 (RNase H2) is a member of the ribonuclease H family of enzymes involved in removal of RNA from RNA-DNA hybrids as well as ribonucleotides which get misincorporated into the genomic DNA. Recent studies have shown that RNase H2 function is also needed for successful DNA repair through NHEJ events where DNA pol µ uses ribonucleotides during the gap filling stage. Mammalian RNase H2 is composed of three subunits, RNASEH2A, RNASEH2B and RNASEH2C. There have been studies suggesting changes in expression of these genes in various cancers of breast, prostate, colon, liver, and kidney. In this study, we have investigated the functional role of RNASEH2A and RNASEH2B in leukemic T-cells, MOLT4 and Jurkat. shRNA mediated knockdown of RNASEH2A/ RNASEH2B expression led to reduced cell survival and increase in apoptotic cell population. Importantly, knockdown of RNASEH2A or RNASEH2B, led to cell cycle arrest at S phase and increased number of 53BP1 foci due to abrogation of NHEJ. Interestingly, RNASEH2A or RNASEH2B depleted cells showed significantly retarded DSB repair kinetics compared to scrambled shRNA control, when exposed to ionizing radiation suggesting that NHEJ is abrogated due to loss of RNASEH2 activity in T-ALL cells. Thus, we uncover the importance of RNase H2 function in leukemic cells and suggest that it can be targeted for cancer therapy.

Azoxystrobin Induces Apoptosis and Cell Cycle Arrest in Human Leukemia Cells Independent of p53 Expression.

BACKGROUND/AIM: Azoxystrobin (AZOX), a methoxyacrylate derivative, has potent antimicrobial and antitumor activities. Here, we report the anticancer effects of AZOX on the p53-negative human myelogenous leukemia cell line HL-60RG and the p53 positive human T-cell leukemia cell line MOLT-4F. MATERIALS AND METHODS: Using both leukemia cells, the anticancer effect of AZOX treatment was analyzed throughout the cell cycle. RESULTS: AZOX damaged both cell lines dose-dependently, and the cell damage rates were almost the same in both lines. Cell cycle distribution analysis showed that the treated MOLT-4F cells arrested at the S phase, whereas HL-60RG cells increased during the subG1 phase, suggesting that cell death was occurring. AZOX-induced cell death in HL-60RG was inhibited with the addition of uridine, which is used as a substrate for the salvage pathway of pyrimidine nucleotides. CONCLUSION: AZOX has p53-independent anticancer effects in leukemia cells, but the mechanisms underlying the damage differ between cell lines.

In vitro characterization of a small molecule PD-1 inhibitor that targets the PD-l/PD-L1 interaction.

Targeting the programmed cell death protein 1/programmed cell death ligand 1 (PD-1/PD-L1) axis with monoclonal antibodies (mAbs) represents a crucial breakthrough in anticancer therapy, but mAbs are limited by their poor oral bioavailability, adverse events in multiple organ systems, and primary, adaptive, and acquired resistance, amongst other issues. More recently, the advent of small molecule inhibitors that target the PD-1/PD-L1 axis have shown promising cellular inhibitory activity and the potential to counteract the disadvantages of mAbs. In this study, structure-based virtual screening identified small molecule inhibitors that effectively inhibited the PD-1/PD-L1 interaction. Six of those small molecule inhibitors were applied to cell-based experiments targeting PD-1: CH-1, CH-2, CH-3, CH-4, CH-5, and CH-6. Of all 6, CH-4 displayed the lowest cytotoxicity and strongest inhibitory activity towards the PD-1/PD-L1 interaction. The experiments revealed that CH-4 inhibited the interaction of soluble form PD-L1 (sPD-L1) with PD-1 surface protein expressed by KG-1 cells. Investigations into CH-4 analogs revealed that CH-4.7 effectively blocked the PD-1/sPD-L1 interaction, but sustained the secretion of interleukin-2 and interferon-γ by Jurkat cells. Our experiments revealed a novel small molecule inhibitor that blocks the interaction of PD-1/sPD-L1 and potentially offers an alternative PD-1 target for immune checkpoint therapy.

Whole-genome-scale identification of novel non-protein-coding RNAs controlling cell proliferation and survival through a functional forward genetics strategy.

Identification of cell fate-controlling lncRNAs is essential to our understanding of molecular cell biology. Here we present a human genome-scale forward-genetics approach for the identification of lncRNAs based on gene function. This approach can identify genes that play a causal role, and immediately distinguish them from those that are differentially expressed but do not affect cell function. Our genome-scale library plus next-generation-sequencing and bioinformatic approach, radically upscales the breadth and rate of functional ncRNA discovery. Human gDNA was digested to produce a lentiviral expression library containing inserts in both sense and anti-sense orientation. The library was used to transduce human Jurkat T-leukaemic cells. Cell populations were selected using continuous culture ± anti-FAS IgM, and sequencing used to identify sequences controlling cell proliferation. This strategy resulted in the identification of thousands of new sequences based solely on their function including many ncRNAs previously identified as being able to modulate cell survival or to act as key cancer regulators such as AC084816.1*, AC097103.2, AC087473.1, CASC15*, DLEU1*, ENTPD1-AS1*, HULC*, MIRLET7BHG*, PCAT-1, SChLAP1, and TP53TG1. Independent validation confirmed 4 out of 5 sequences that were identified by this strategy, conferred a striking resistance to anti-FAS IgM-induced apoptosis.

Recent advances in T-cell lymphoid neoplasms.

T Cells comprise many subtypes of specified lymphocytes, and their differentiation and function take place in different tissues. This cellular diversity is also observed in the multiple ways T-cell transformation gives rise to a variety of T-cell neoplasms. This review covers the main types of T-cell malignancies and their specific characteristics, emphasizing recent advances at the cellular and molecular levels as well as differences and commonalities among them.

TooManyPeaks identifies drug-resistant-specific regulatory elements from single-cell leukemic epigenomes.

Emerging single-cell epigenomic assays are used to investigate the heterogeneity of chromatin activity and its function. However, identifying cells with distinct regulatory elements and clearly visualizing their relationships remains challenging. To this end, we introduce TooManyPeaks to address the need for the simultaneous study of chromatin state heterogeneity in both rare and abundant subpopulations. Our analyses of existing data from three widely used single-cell assays for transposase-accessible chromatin using sequencing (scATAC-seq) show the superior performance of TooManyPeaks in delineating and visualizing pure clusters of rare and abundant subpopulations. Furthermore, the application of TooManyPeaks to new scATAC-seq data from drug-naive and drug-resistant leukemic T cells clearly visualizes relationships among these cells and stratifies a rare "resistant-like" drug-naive sub-clone with distinct cis-regulatory elements.

Methods to Study CARD11-BCL10-MALT1 Dependent Canonical NF-κB Activation in Jurkat T Cells.

Jurkat T cells have been of central importance for the discovery of signalling mediators driving NF-κB activation in response to T cell antigen receptor (TCR)/CD28 co-stimulation. The critical function of the key regulators identified in Jurkat T cells has subsequently been verified in primary murine and human T cells. CRISPR/Cas9-mediated genomic editing techniques in combination with viral reconstitution are powerful tools that now enable the investigation of the exact molecular mechanisms that govern T cell signalling, especially the impact of protein-protein interactions, protein modifications, or cancer-associated gain- or loss-of-function mutations. As exemplified by the CARD11 gene encoding a key regulator of NF-κB signalling in T cells, we describe here the detailed workflow for the generation of CRISPR/Cas9 knockout (KO) Jurkat T cells and the subsequent reconstitution using a lentiviral transduction protocol. In addition, we explain the use of a stable NF-κB-dependent EGFP reporter system that enables a reliable quantification of NF-κB transcriptional activation in the reconstituted KO Jurkat T cells.

Competitive SPR using an intracellular anti-LMO2 antibody identifies novel LMO2-interacting compounds.

The use of intracellular antibodies as templates to derive surrogate compounds is an important objective because intracellular antibodies can be employed initially for target validation in pre-clinical assays and subsequently employed in compound library screens. LMO2 is a T cell oncogenic protein activated in the majority of T cell acute leukaemias. We have used an inhibitory intracellular antibody fragment as a competitor in a small molecule library screen using competitive surface plasmon resonance (cSPR) to identify compounds that bind to LMO2. We selected four compounds that bind to LMO2 but not when the anti-LMO2 intracellular antibody fragment is bound to it. These findings further illustrate the value of intracellular antibodies in the initial stages of drug discovery campaigns and more generally antibodies, or antibody fragments, can be the starting point for chemical compound development as surrogates of the antibody combining site.

State-of-Art of Cellular Therapy for Acute Leukemia.

With recent clinical breakthroughs, immunotherapy has become the fourth pillar of cancer treatment. Particularly, immune cell-based therapies have been envisioned as a promising treatment option with curative potential for leukemia patients. Hence, an increasing number of preclinical and clinical studies focus on various approaches of immune cell-based therapy for treatment of acute leukemia (AL). However, the use of different immune cell lineages and subsets against different types of leukemia and patient disease statuses challenge the interpretation of the clinical applicability and outcome of immune cell-based therapies. This review aims to provide an overview on recent approaches using various immune cell-based therapies against acute B-, T-, and myeloid leukemias. Further, the apparent limitations observed and potential approaches to overcome these limitations are discussed.

Pre-depletion of TRBC1+ T cells promotes the therapeutic efficacy of anti-TRBC1 CAR-T for T-cell malignancies.

Targeting T cell receptor ß-chain constant region 1 (TRBC1) CAR-T could specifically kill TRBC1+ T-cell malignancies. However, over-expressed CARs on anti-TRBC1 CAR transduced TRBC1+ T cells (CAR-C1) bound to autologous TRBC1, masking TRBC1 from identification by other anti-TRBC1 CAR-T, and moreover only the remaining unoccupied CARs recognized TRBC1+ cells, considerably reducing therapeutic potency of CAR-C1. In addition, co-culture of anti-TRBC1 CAR-T and TRBC1+ cells could promote exhaustion and terminal differentiation of CAR-T. These findings provide a rationale for pre-depleting TRBC1+ T cells before anti-TRBC1 CAR-T manufacturing.

Crosstalk between Noxa, Bcl-2, and ceramide in mediating p53-dependent apoptosis in Molt-4 human T-cell leukemia.

Ionizing radiation induces apoptosis in human Molt-4 leukemia cells in a p53-dependent manner. The tumor suppressor p53 stimulates various downstream targets that presumably trigger, individually or in concert, de novo ceramide synthesis and intrinsic apoptosis via mitochondrial outer membrane permeabilization (MOMP). Among these targets, BH3-only protein Noxa was found to be promptly activated by p53 prior to ceramide accumulation and apoptosis in response to irradiation. To evaluate the relation between Noxa and ceramide in irradiation-induced apoptosis, Noxa was silenced in Molt-4 cells and apoptosis, p53 expression, and ceramide accumulation were assessed in response to irradiation. In the absence of Noxa, irradiation of Molt-4 cells still induced apoptosis in a p53-dependent manner however ceramide levels decreased significantly although they remained higher than untreated control. Upon irradiation, Noxa was found to translocate to the mitochondria where endogenous ceramide accumulation was observed. In contrast, overexpression of Bcl-2, another mitochondrial protein, in Molt-4 cells abolished the endogenous ceramide accumulation and apoptosis. In irradiation-induced, p53-dependent pathways of apoptosis, the pro-apoptotic Noxa represents one of several, yet to be identified, pathways simultaneously triggered by p53 to produce mitochondrial ceramide accumulation and apoptosis. In contrast, Bcl-2 functions as a broader inhibitor of both ceramide accumulation and apoptosis. Altogether, these results indicate that members of the Bcl-2 family differentially regulate ceramide accumulation and reveal the existence of crosstalk between Bcl-2 family members and ceramide in mediating p53-dependent apoptosis in Molt-4 human T-cell leukemia.

The c-Rel-c-Myc axis controls metabolism and proliferation of human T leukemia cells.

Genome-wide association studies have established that human REL is a susceptibility gene for lymphoid cancers and inflammatory diseases. REL is the hematopoietic member of the nuclear factor-κB (NF-κB) family and is frequently amplified in human lymphomas. However, the mechanism through which REL and its encoded protein c-Rel affect human lymphoma is largely unknown. Using both loss-of-function and gain-of-function approaches, we studied the roles of REL gene in human Jurkat leukemia cells. Compared with control Jurkat cells, REL knockout cells exhibited significant defects in cell growth and mitochondrial respiration. Genome-wide transcriptome analyses revealed that T cells lacking c-Rel had selective defects in the expression of inflammatory and metabolic genes including c-Myc. We found that c-Rel controlled the expression of c-Myc through its promotor, and expressing c-Myc in c-Rel-deficient lymphoma cells rescued their proliferative and metabolic defects. Thus, the human c-Rel-c-Myc axis controls lymphoma growth and metabolism and could be a therapeutic target for lymphomas.

Tetrandrine enhances glucocorticoid receptor translocation possibly via inhibition of P-glycoprotein in daunorubicin-resistant human T lymphoblastoid leukemia cells.

Glucocorticoids are used as anticancer and immunosuppressive agents, whereas glucocorticoid resistance has been observed in a significant fraction of patients due to overexpression of P-glycoprotein encoded by multi-drug resistance-1 gene. Tetrandrine is a bisbenzylisoquinoline alkaloid isolated from traditional herb Fangji. According to our previous report, tetrandrine potentiated glucocorticoid pharmacodynamics partially via inhibiting P-glycoprotein function. In the present study, we investigated whether glucocorticoid receptor translocation was influenced indirectly by tetrandrine via P-glycoprotein inhibition, using human T lymphoblastoid leukemia MOLT-4 cell line with little P-glycoprotein expression and its multidrug resistant sub-line MOLT-4/DNR exhibiting a large amount of P-glycoprotein. Molecular mechanism investigation suggested that overexpressed P-glycoprotein weakened the glucocorticoid receptor translocation in MOLT-4/DNR cells comparing with the parent MOLT-4 cells. Our data also suggested that tetrandrine enhanced nuclear glucocorticoid receptor translocation in MOLT-4/DNR cells indirectly by dual influences on P-glycoprotein, inhibiting the efflux function and downregulating the protein expression. Therefore, tetrandrine potentiated the cytotoxic effect of methylprednisolone against MOLT-4/DNR cells with less effects on MOLT-4 cells. These effects of tetrandrine were suggested to be beneficial for the treatment of glucocorticoid resistant diseases induced by the overexpression of P-glycoprotein.

Targeting Glycosylated PD-1 Induces Potent Antitumor Immunity.

Immunotherapies targeting programmed cell death protein 1 (PD-1) and programmed cell death 1 ligand 1 (PD-L1) immune checkpoints represent a major breakthrough in cancer treatment. PD-1 is an inhibitory receptor expressed on the surface of activated T cells that dampens T-cell receptor (TCR)/CD28 signaling by engaging with its ligand PD-L1 expressed on cancer cells. Despite the clinical success of PD-1 blockade using mAbs, most patients do not respond to the treatment, and the underlying regulatory mechanisms of PD-1 remain incompletely defined. Here we show that PD-1 is extensively N-glycosylated in T cells and the intensities of its specific glycoforms are altered upon TCR activation. Glycosylation was critical for maintaining PD-1 protein stability and cell surface localization. Glycosylation of PD-1, especially at the N58 site, was essential for mediating its interaction with PD-L1. The mAb STM418 specifically targeted glycosylated PD-1, exhibiting higher binding affinity to PD-1 than FDA-approved PD-1 antibodies, potently inhibiting PD-L1/PD-1 binding, and enhancing antitumor immunity. Together, these findings provide novel insights into the functional significance of PD-1 glycosylation and offer a rationale for targeting glycosylated PD-1 as a potential strategy for immunotherapy. SIGNIFICANCE: These findings demonstrate that glycosylation of PD-1 is functionally significant and targeting glycosylated PD-1 may serve as a means to improve immunotherapy response.

Bone Marrow Immunohistochemistry and Flow Cytometry in the Diagnosis of Malignant Hematologic Diseases With Emphasis on Lymphomas: A Comparative Retrospective Study.

We aim to evaluate the degree of agreement between immunohistochemistry (IHC) and flow cytometry (FC) in the diagnosis of malignant hematologic diseases, mainly lymphomas. A total of 260 bone marrow biopsies, 255 bone marrow aspirates, and 5 other suspensions of 260 patients used for diagnosis of a hematologic malignancy between 2009 and 2012 with both, IHC and FC, were retrospectively analyzed. Overall there is a substantial degree of agreement (κ=0.69) between IHC and FC. Chronic lymphocytic leukemia/small lymphocytic lymphoma, mature T-cell neoplasms, acute leukemias, and myelodysplastic syndromes had the highest concurrence rates (>80%). In nonconcordant cases, an IHC provided diagnosis in 25.4%, and an FC in 4.6%. Lymphomas were diagnosed by an IHC only in 51% of the cases. Both methods have good concurrence rates and are complementary. An IHC has the advantage of combining markers, morphology, and tissue immunoarchitecture, which is beneficial in the diagnosis of lymphomas. An FC is required in leukemias as it is faster and plays an important role in minimal residual disease.

Fli-1 promotes proliferation and upregulates NANOGP8 expression in T-lymphocyte leukemia cells.

Friend leukemia integration 1 (Fli-1) is a member of the E26 transformation-specific (ETS) transcription factor family. Fli-1 regulates normal hematopoiesis and vasculogenesis, and its aberrant expression underlies virus-induced leukemias and various types of human cancers. NANOGP8, a retro-pseudogene of stem cell mediator NANOG, is expressed predominantly in cancer cells and plays a role in tumorigenesis. In this study, we demonstrate that Fli-1 expression enhances human acute T-cell leukemia Jurkat cell proliferation and that Fli-1 acts as a transcriptional activator of NANOGP8 expression in these cells. NANOGP8 and Fli-1 are highly expressed in Jurkat cells, whereas NANOG was undetectable at both the RNA and protein levels. Moreover, the expression of endogenous NANOGP8 was significantly influenced by gain of function and loss of function of Fli-1. Promoter-reporter assays showed that NANOGP8 transcription was significantly upregulated by dose-dependent Fli-1 overexpression. A series of deletion mutagenesis of NANOGP8 promoter sequence revealed that NANOGP8 promoter activity was tightly regulated and found the minimal promoter region sufficient to activate NANOGP8 transcription mediated by Fli-1. Moreover, site-directed mutagenesis of the putative binding site abolished both NANOGP8 full-length and minimal promoter activities. Binding assays revealed that Fli-1 directly interacts with the potent binding site in NANOG promoter region. Taken together, our data demonstrate that Fli-1 is a novel upstream transcriptional activator of NANOGP8 and provide the molecular details of Fli-1-mediated NANOGP8 gene expression. Ultimately, these findings may contribute to understanding the expanded regulatory mechanisms of oncogenic NANOGP8 and ETS family transcription factors in leukemogenesis.

Inducible histone K-to-M mutations are dynamic tools to probe the physiological role of site-specific histone methylation in vitro and in vivo.

Development and differentiation are associated with profound changes to histone modifications, yet their in vivo function remains incompletely understood. Here, we generated mouse models expressing inducible histone H3 lysine-to-methionine (K-to-M) mutants, which globally inhibit methylation at specific sites. Mice expressing H3K36M developed severe anaemia with arrested erythropoiesis, a marked haematopoietic stem cell defect, and rapid lethality. By contrast, mice expressing H3K9M survived up to a year and showed expansion of multipotent progenitors, aberrant lymphopoiesis and thrombocytosis. Additionally, some H3K9M mice succumbed to aggressive T cell leukaemia/lymphoma, while H3K36M mice exhibited differentiation defects in testis and intestine. Mechanistically, induction of either mutant reduced corresponding histone trimethylation patterns genome-wide and altered chromatin accessibility as well as gene expression landscapes. Strikingly, discontinuation of transgene expression largely restored differentiation programmes. Our work shows that individual chromatin modifications are required at several specific stages of differentiation and introduces powerful tools to interrogate their roles in vivo.