Comparison of thymocyte development and cytokine production in CD7-deficient, CD28-deficient and CD7/CD28 double-deficient mice

CD7 protein plays a crucial role in T cell infiltration in tumors

CD7 protein as a target is being used to treat CD7⁺ lymphoma; however, the role of CD7 in the hematopoietic system remains largely unknown. Therefore, we evaluated the effects of CD7 KO in mice. The differentiation of the hematopoietic system in the bone marrow and the number of various cell types in the thymus and spleen did not differ between CD7 KO and WT mice. After subcutaneous inoculation of B16-F10 melanoma cells, tumors from CD7 KO mice grew more rapidly, and the proportion of CD8⁺ T cells in the spleen and tumors decreased. In vitro, the infiltration and adhesion of CD8⁺ T cells from the spleen of CD7 KO mice were weakened. Blocking CD7 in normal T cells did not alter the migration and infiltration, but in Jurkat, CCRF-CEM, and KG-1a tumor cell lines, migration and invasion were significantly reduced after blocking CD7. Therefore, CD7 does not affect hematopoietic system development but plays a crucial role in T cell infiltration into tumors.

CD28-signaling can be partially compensated in CD28-knockout mice but is essential for virus elimination in a murine model of multiple sclerosis

The intracerebral infection of mice with Theiler’s murine encephalomyelitis virus (TMEV) represents a well-established animal model for multiple sclerosis (MS). Because CD28 is the main co-stimulatory molecule for the activation of T cells, we wanted to investigate its impact on the course of the virus infection as well as on a potential development of autoimmunity as seen in susceptible mouse strains for TMEV. In the present study, 5 weeks old mice on a C57BL/6 background with conventional or tamoxifen-induced, conditional CD28-knockout were infected intracerebrally with TMEV-BeAn. In the acute phase at 14 days post TMEV-infection (dpi), both CD28-knockout strains showed virus spread within the central nervous system (CNS) as an uncommon finding in C57BL/6 mice, accompanied by histopathological changes such as reduced microglial activation. In addition, the conditional, tamoxifen-induced CD28-knockout was associated with acute clinical deterioration and weight loss, which limited the observation period for this mouse strain to 14 dpi. In the chronic phase (42 and 147 dpi) of TMEV-infection, surprisingly only 33% of conventional CD28-knockout mice showed chronic TMEV-infection with loss of motor function concomitant with increased spinal cord inflammation, characterized by T- and B cell infiltration, microglial activation and astrogliosis at 33-42 dpi. Therefore, the clinical outcome largely depends on the time point of the CD28-knockout during development of the immune system. Whereas a fatal clinical outcome can already be observed in the early phase during TMEV-infection for conditional, tamoxifen-induced CD28-knockout mice, only one third of conventional CD28-knockout mice develop clinical symptoms later, accompanied by ongoing inflammation and an inability to clear the virus. However, the development of autoimmunity could not be observed in this C57BL/6 TMEV model irrespective of the time point of CD28 deletion.

Autologous nanobody-derived fratricide-resistant CD7-CAR T cell therapy for patients with relapsed and refractory T-cell acute lymphoblastic leukemia/lymphoma

Purpose: Since CD7 may represent a potent target for T-lymphoblastic leukemia/lymphoma (T-ALL/LBL) immunotherapy, this study aimed to investigate safety and efficacy of autologous CD7-chimeric antigen receptor (CAR) T cells in relapsed and refractory (R/R) T-ALL/LBL patients, as well as its manufacturing feasibility. Experimental Design: Preclinical phase was conducted in NPG{trade mark, serif} mice injected with Luc+ GFP+CCRF-CEM cells. Open label phase I clinical trial (NCT04004637) enrolled patients with R/R CD7-positive T-ALL/LBL who received autologous CD7-CAR T cells infusion. Primary endpoint was safety, secondary endpoints included efficacy, pharmacokinetic and pharmacodynamic parameters. Results: CD7 blockade strategy was developed using tandem CD7 nanobody VHH6 coupled with an ER/Golgi-retention motif peptide to intracellularly fasten CD7 molecules. In preclinical phase CD7 blockade CAR T-cells prevented fratricide and exerted potent cytolytic activity, significantly relieving leukemia progression and prolonged the median survival of mice. In clinical phase, the complete remission (CR) rate was 87.5% (7/8) three months after CAR T cells infusion; one leukemia patient achieved minimal residual disease negative CR and one lymphoma patient achieved CR for more than 12 months. Majority of patients (87.5%) only had grade 1 or 2 cytokine release syndrome with no T-cell hypoplasia or any neurological toxicities observed. The median maximum concentration of CAR T cells was 857.2 cells/µL at approximately 12 days and remained detectable up to 270 days. Conclusions: Autologous nanobody-derived fratricide-resistant CD7-CAR T cells demonstrated a promising and durable antitumor response in R/R T-ALL/LBL with tolerable toxicity, warranting further studies in highly aggressive CD7-positive malignancies.

Surfaceome interrogation using an RNA-seq approach highlights leukemia initiating cell biomarkers in an LMO2 T cell transgenic model

The surfaceome is critical because surface proteins provide a gateway for internal signals and transfer of molecules into cells, and surfaceome differences can influence therapy response. We have used a surfaceome analysis method, based on comparing RNA-seq data between normal and abnormal cells (Surfaceome DataBase Mining or Surfaceome DBM), to identify sets of upregulated cell surface protein mRNAs in an LMO2-mediated T-ALL mouse model and corroborated by protein detection using antibodies. In this model the leukemia initiating cells (LICs) comprise pre-leukaemic, differentiation inhibited thymocytes allowing us to provide a profile of the LIC surfaceome in which GPR56, CD53 and CD59a are co-expressed with CD25. Implementation of cell surface interaction assays demonstrates fluid interaction of surface proteins and CD25 is only internalized when co-localized with other proteins. The Surfaceome DBM approach to analyse cancer cell surfaceomes is a way to find targetable surface biomarkers for clinical conditions where RNA-seq data from normal and abnormal cell are available.

Autocrine GM-CSF transcription in the leukemic progenitor cell line KG1a is mediated by the transcription factor ETS1 and is negatively regulated through SECTM1 mediated ligation of CD7

BACKGROUND

CD7 expression is found on ~30% of acute myeloblastic leukemias (AML). The leukemic progenitor cell line KG1a (CD7+) constitutively expresses GM-CSF while the parental KG1 (CD7-) cell line does not. This study focuses on the molecular basis of CD7 mediated GM-CSF regulation.

METHODS

KG1a cells were treated with recombinant SECTM1-Fc protein, the PI3K kinase inhibitors wortmannin, LY292004, or PI4K activator spermine. Stable KG1-CD7+, KG1a-shCD7, KG1a-shETS1 as well as KG1a-GFP, KG1a-PKCβII-GFP cell lines were generated and the levels of CD7, GM-CSF and ETS-1 mRNA and protein were compared by real-time-PCR, western blotting, flow cytometry and ELISA.

RESULTS

SECTM1 is expressed in Human Bone Marrow Endothelial Cells (HBMEC) and its expression can be upregulated by both IFN-γ. KG1a cells demonstrated high expression levels of CD7 and ETS-1 allowing a constitutative signaling through the PI3K/Atk pathway to promote GM-CSF expression, while KG1 cells with low expression of CD7 and ETS-1 showed low GM-CSF expression. On KG1a cells GM-CSF expression could be negatively regulated by PI3K inhibitors or by recombinant SECTM1-Fc. Overexpression of CD7 in KG1 cells was insufficient to promote GM-CSF expression, while silencing of CD7 or ETS-1 resulted in reduced GM-CSF expression levels. Differentiation capable KG1a cells overexpressing PKCβII illustrated complete loss of CD7, but maintained normal levels of both ETS-1 and GM-CSF expression.

CONCLUSION

These findings add an additional layer to the previously described autocrine/paracrine signaling between leukemic progenitor cells and the bone marrow microenvironment and highlight a role for SECTM1 in both normal and malignant hematopoiesis.

GENERAL SIGNIFICANCE

This work shows that SECTM1 secreted from bone marrow stromal cells may interact with CD7 to influence GM-CSF expression in leukemic cells.

K12/SECTM1, an interferon-γ regulated molecule, synergizes with CD28 to costimulate human T cell proliferation

CD7 is a cell-surface molecule, expressed on T lymphocytes and NK cells, which functions as a costimulatory receptor for T cell proliferation. SECTM1 has been proposed as a ligand for CD7. However, the expression pattern of this molecule in human immune cells and role in human T cell function remain unclear. In the present study, using human rSECTM1, we demonstrate that SECTM1 strongly costimulates CD4 and CD8 T cell proliferation and induces IFN-γ production, likely via a CD7-dependent mechanism. In addition, SECTM1 synergizes with suboptimal anti-CD28 to strongly augment T cell functions. We found a robust induction of IL-2 production when SECTM1 and anti-CD28 signals were present with TCR ligation. Furthermore, addition of SECTM1 into a MLR significantly enhanced proliferation of alloantigen-activated T cells, whereas blockade of SECTM1 inhibited T cell proliferation in a two-way MLR assay. Simultaneously blocking the effect of SECTM1, along with CTLA-4/Fc, diminishes two-way MLR. Finally, we demonstrated that expression of SECTM1 is not detected in monocytes and imMoDCs at the protein level. However, it is strongly induced by IFN-γ in monocytes and imMoDCs, and this induction is STAT1-dependent. These results indicate that SECTM1 is a broadly expressed, IFN-γ-inducible molecule, which functions as a potent costimulatory ligand for T cell activation and is synergistic with anti-CD28.

Regulation of insulin gene expression by cytokines and cell-cell interactions in mouse medullary thymic epithelial cells

AIMS/HYPOTHESIS

The expression of tissue-specific self-antigens in the thymus is essential for self-tolerance. Genetic susceptibility to type 1 diabetes correlates inversely with thymic insulin expression and, in mice, lowered levels of this expression result in T cell responses against insulin. This study was undertaken to examine whether thymic insulin expression is regulated by the same metabolic stimuli as in beta cells or by different inputs, possibly of an immune nature.

METHODS

Ins2 mRNA changes in mouse thymus were evaluated in vivo, following intraperitoneal glucose injection. We also examined the effect of a high glucose concentration on Ins2 mRNA in clones of insulin-expressing medullary thymus epithelial cell lines (mTECs). The same in vitro system was used to evaluate the effect of IFN-gamma and cell-to-cell contact with thymocytes in co-culture.

RESULTS

Ins2 mRNA was significantly increased in the pancreas following a glucose load, but remained unchanged in the thymus. Furthermore, stimulation of insulin-expressing mTECs in vitro with IFN-gamma, a cytokine involved in T cell negative selection, decreased levels of insulin expression even though expression of Aire was increased. Last, co-culture of mTECs with thymocytes resulted in an upregulation of both Aire and insulin expression.

CONCLUSIONS/INTERPRETATION

We conclude that regulation of insulin transcription in the thymus is not dependent on metabolic stimuli but it may, instead, be under the control of cytokines and cell-to-cell interactions with lymphoid cells. That this regulation is not always coordinated with that of Aire, a non-specific master switch, suggests insulin-specific mechanisms.

CD7 expression and galectin-1-induced apoptosis of immature thymocytes are directly regulated by NF-kappaB upon T-cell activation

CD7, one of the galectin-1 receptors, has crucial roles in galectin-1-mediated apoptosis of activated T-cells and T-lymphoma progression in peripheral tissues. In this study, we showed that CD7 promoter activity was increased by NF-kappaB and that this activity was synergistic when Sp1 was co-expressed in the immature T-cell line L7. Site-directed mutagenesis analysis of the CD7 promoter indicated that NF-kappaB specifically bound to the NF-kappaE2 site in cooperation with Sp1. Overexpression of E12 or Twist2 proteins negatively regulated NF-kappaB-mediated activity of the CD7 proximal promoter. In addition, CD7 expression was down-regulated by treatment with the p38 MAPK inhibitor SB20358, or the MSK1 inhibitor H-89. These signaling pathway inhibitors prevented galectin-1-mediated apoptosis of immature T-cells. From these results, we concluded that the regulation of CD7 gene expression through NF-kappaB activation induced by TCR/CD28 might have significant implications for T-cell homeostasis.

Neurofibromin-deficient Schwann cells have increased lysophosphatidic acid dependent survival and migration-implications for increased neurofibroma formation during pregnancy

Neurofibromas are the clinical hallmark of neurofibromatosis Type 1 (NF1), a genetic disorder caused by mutations of the NF1 tumor suppressor gene, which encodes neurofibromin that functions as a GTPase activating protein (GAP) for Ras. During pregnancy, up to 50% of existing neurofibromas enlarge and as many as 60% of new neurofibromas appear for the first time. Lysophosphatidic acid (LPA) is a prototypic lysophospholipid that modulates cell migration and survival of Schwann cells (SCs) and is made in increasing concentrations throughout pregnancy. We addressed the influence of LPA on the biochemical and cellular functions of SCs with a homozygous mutation of the murine homologue of the NF1 gene (Nf1-/-). LPA promoted F-actin polymerization and increased migration and survival of Nf1-/- SCs as compared to wild type (WT) SCs. Furthermore, LPA induced a higher level of Ras-GTP and Akt phosphorylation in Nf1-/- SCs as compared to WT cells. Pharmacologic inhibition or siRNA for the p85beta regulatory subunit of Class I A PI3-K significantly reduced LPA-induced Schwann cell survival and migration. Introduction of NF1-GRD reconstitution was sufficient to normalize the LPA-mediated motility of Nf1-/- SCs. As LPA modulates excessive cell survival and motility of Nf1-/- SCs, which are the tumorigenic cells in NF1, targeting PI3-K may be a potential therapeutic approach in diminishing the development and progression of neurofibromas in pregnant women with NF1.

Expression of the CD7 ligand K-12 in human thymic epithelial cells: regulation by IFN-gamma

CD7 is an immunoglobulin superfamily molecule expressed on T, NK, and pre-B lymphocytes. Previous studies have demonstrated a role for CD7 in T- and NK-cell activation and cytokine production. Recently, an epithelial cell secreted protein, K12, was identified as a CD7 ligand. Although CD7 is expressed intrathymically, it is not known if K12 is produced in human thymus. To determine roles that K12 might play in the human thymus, we analyzed expression of K12 in human thymocytes, thymic epithelial cells (TE), and thymic fibroblasts. We found that recombinant human K12 bound strongly to soluble hCD7, with a Keq of 37.6x10(-9) M, and this interaction was inhibited by a novel antihuman K12 monoclonal antibody (K12-A1). K12 mRNA was detected by RT-PCR and northern analysis in human TE and thymic fibroblasts, but not in human thymocytes. Expression of K12 in TE cells was upregulated by IFN-gamma. Taken together, these data demonstrated that K12 is produced by human TE cells and thymic fibroblasts, and is regulated in thymus by IFN-gamma. These data suggest a role for thymic microenvironment-produced K12 in regulation of thymocyte signaling and cytokine release, particularly in the setting of thymus pathology where IFN-gamma is upregulated such as myasthenia gravis.

Different thresholds of Notch signaling bias human precursor cells toward B-, NK-, monocytic/dendritic-, or T-cell lineage in thymus microenvironment

Notch receptors are involved in lineage decisions in multiple developmental scenarios, including hematopoiesis. Here, we treated hybrid human-mouse fetal thymus organ culture with the gamma-secretase inhibitor 7 (N-[N-(3,5-difluorophenyl)-l-alanyl]-S-phenyl-glycine t-butyl ester) (DAPT) to establish the role of Notch signaling in human hematopoietic lineage decisions. The effect of inhibition of Notch signaling was studied starting from cord blood CD34(+) or thymic CD34(+)CD1(-), CD34(+)CD1(+), or CD4ISP progenitors. Treatment of cord blood CD34(+) cells with low DAPT concentrations results in aberrant CD4ISP and CD4/CD8 double-positive (DP) thymocytes, which are negative for intracellular T-cell receptor beta (TCRbeta). On culture with intermediate and high DAPT concentrations, thymic CD34(+)CD1(-) cells still generate aberrant intracellular TCRbeta(-) DP cells that have undergone DJ but not VDJ recombination. Inhibition of Notch signaling shifts differentiation into non-T cells in a thymic microenvironment, depending on the starting progenitor cells: thymic CD34(+)CD1(+) cells do not generate non-T cells, thymic CD34(+)CD1(-) cells generate NK cells and monocytic/dendritic cells, and cord blood CD34(+)Lin(-) cells generate B, NK, and monocytic/dendritic cells in the presence of DAPT. Our data indicate that Notch signaling is crucial to direct human progenitor cells into the T-cell lineage, whereas it has a negative impact on B, NK, and monocytic/dendritic cell generation in a dose-dependent fashion.

CD7 and CD28 Are Required for Murine CD4+CD25+ Regulatory T Cell Homeostasis and Prevention of Thyroiditis

CD7 and CD28 are T cell Ig superfamily molecules that share common signaling mechanisms. To determine roles CD7 and CD28 might play in peripheral lymphocyte development and function, we have generated CD7/CD28-double-deficient mice. CD7- and CD28-single-deficient and CD7/CD28-double-deficient mice had normal levels of CD4 and CD8-single-positive T cells in thymus and spleen. However, CD28-deficient mice had decreased CD4+CD25+ T cells in spleen compared with wild-type mice, and CD7/CD28-double-deficient mice had decreased numbers of CD4+CD25+ T cells in both thymus and spleen compared with both wild-type and CD28-deficient mice. Functional studies demonstrated that CD4+CD25+ T cells from CD28-deficient and CD7/CD28-double-deficient mice could mediate suppression of CD3 mAb activation of CD4+CD25- wild-type T cells, but were less potent than wild-type CD4+CD25+ T regulatory cells. Thyroiditis developed in aged CD7/CD28-double-deficient mice (>1 year) that was not seen in age-matched control mice or single CD7- or CD28-deficient mice, thus suggesting in vivo loss of T regulatory cells allowed for the development of spontaneous thyroiditis. Taken together, these data demonstrated collaborative roles for both CD7 and CD28 in determination of number and function of CD4+CD25+ T regulatory cells in the thymus and peripheral immune sites and in the development of spontaneous thyroiditis.

Con A activates an Akt/PKB dependent survival mechanism to modulate TCR induced cell death in double positive thymocytes

While low avidity ligation of the T cell receptor (TCR) leads to positive selection and further maturation of developing thymocytes providing the immune system with mature CD4(+) and CD8(+) (single positive) T cells, high avidity ligation triggers negative selection by apoptotic cell death and therefore the TCR repertoire is purged of autoreactive T cells. On peripheral T cells, however, high avidity ligation of the TCR triggers activation and survival not death. In the present study we used concanavalin A (Con A) and alpha-CD3 epsilon antibody to investigate a possible survival mechanism in connection with TCR ligation. Con A and alpha-CD3 epsilon were used in the study for the following reasons: (1) they both mimic the effects of high avidity TCR ligation by activating peripheral T cells, and (2) they trigger distinctively different physiological changes in developing thymocytes. While Con A supports events associated with cellular survival, alpha-CD3 epsilon induces apoptotic cell death. In our experimental system the TCR was cross-linked by Con A and alpha-CD3 epsilon in thymocytes of major histocompatibility complex (MHC) deficient thymus organ cultures, where signals from the TCR can be triggered on zero background signal level. We have found that TCR cross-linking by Con A and not by alpha-CD3 epsilon decreases the gene and protein expression of the pro-apoptotic molecule, Bad; and that Con A is capable of the activation of the survival signalling pathway including protein kinase B (Akt/PKB) independently of phosphatidyl inositol kinase (PI3K).