Publications by authors named "Ivan Maillard"

131 Publications

Inflammation rapidly recruits mammalian GMP and MDP from bone marrow into regional lymphatics.

Elife 2021 Apr 8;10. Epub 2021 Apr 8.

Hoxworth Blood Center, University of Cincinnati, Cincinnati, United States.

Innate immune cellular effectors are actively consumed during systemic inflammation but the systemic traffic and the mechanisms that support their replenishment remain unknown. Here we demonstrate that acute systemic inflammation induces the emergent activation of a previously unrecognized system of rapid migration of granulocyte-macrophage progenitors and committed macrophage-dendritic progenitors, but not other progenitors or stem cells, from bone marrow (BM) to regional lymphatic capillaries. The progenitor traffic to the systemic lymphatic circulation is mediated by Ccl19/Ccr7 and is NFkB independent, Traf6/IkB-kinase/SNAP23 activation dependent, and is responsible for the secretion of pre-stored Ccl19 by a subpopulation of CD205/CD172a conventional dendritic cells type 2 (cDC2) and upregulation of BM myeloid progenitor Ccr7 signaling. Mature myeloid Traf6 signaling is anti-inflammatory and necessary for lymph node (LN) myeloid cell development. This report unveils the existence and the mechanistic basis of a very early direct traffic of myeloid progenitors from BM to lymphatics during inflammation.
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http://dx.doi.org/10.7554/eLife.66190DOI Listing
April 2021

TPP1 mutagenesis screens unravel shelterin interfaces and functions in hematopoiesis.

JCI Insight 2021 Apr 6. Epub 2021 Apr 6.

Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, United States of America.

Telomerase catalyzes chromosome end replication in stem cells and other long-lived cells. Mutations in telomerase or telomere-related genes result in diseases known as telomeropathies. Telomerase is recruited to chromosome ends by the ACD/TPP1 protein (TPP1 hereafter), a component of the shelterin complex that protects chromosome ends from unwanted end-joining. TPP1 facilitates end-protection by binding shelterin proteins POT1 and TIN2. TPP1 variants have been associated with telomeropathies, but remain poorly characterized in vivo. Disease variants and mutagenesis scans provide efficient avenues to interrogate the distinct physiological roles of TPP1. Here, we conduct mutagenesis in the TIN2- and POT1-binding domains of TPP1 to discover mutations that dissect TPP1's functions. Our results extend upon current structural data to reveal that the TPP1-TIN2 interface is more extensive than previously thought, and highlight the robustness of the POT1-TPP1 interface. Introduction of separation-of-function mutants alongside known TPP1 telomeropathy mutations in mouse hematopoietic stem cells (mHSCs) lacking endogenous TPP1 demonstrated a clear phenotypic demarcation. TIN2- and POT1-binding mutants were unable to rescue mHSC failure resulting from end-deprotection. In contrast, TPP1 telomeropathy mutations sustained mHSC viability, consistent with them selectively impacting end-replication. These results highlight the power of scanning mutagenesis in revealing structural interfaces and dissecting multifunctional genes.
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http://dx.doi.org/10.1172/jci.insight.138059DOI Listing
April 2021

Lymphocyte egress signal sphingosine-1-phosphate promotes ERM-guided, bleb-based migration.

J Cell Biol 2021 Jun;220(6)

Department of Pathology and Laboratory Medicine, Children's Hospital of Philadelphia Research Institute, Philadelphia, PA.

Ezrin, radixin, and moesin (ERM) family proteins regulate cytoskeletal responses by tethering the plasma membrane to the underlying actin cortex. Mutations in ERM proteins lead to severe combined immunodeficiency, but the function of these proteins in T cells remains poorly defined. Using mice in which T cells lack all ERM proteins, we demonstrate a selective role for these proteins in facilitating S1P-dependent egress from lymphoid organs. ERM-deficient T cells display defective S1P-induced migration in vitro, despite normal responses to standard protein chemokines. Analysis of these defects revealed that S1P promotes a fundamentally different mode of migration than chemokines, characterized by intracellular pressurization and bleb-based motility. ERM proteins facilitate this process, controlling directional migration by limiting blebbing to the leading edge. We propose that the distinct modes of motility induced by S1P and chemokines are specialized to allow T cell migration across lymphatic barriers and through tissue stroma, respectively.
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http://dx.doi.org/10.1083/jcb.202007182DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8006814PMC
June 2021

CD8 T cells compensate for impaired humoral immunity in COVID-19 patients with hematologic cancer.

Res Sq 2021 Feb 2. Epub 2021 Feb 2.

Cancer patients have increased morbidity and mortality from Coronavirus Disease 2019 (COVID-19), but the underlying immune mechanisms are unknown. In a cohort of 100 cancer patients hospitalized for COVID-19 at the University of Pennsylvania Health System, we found that patients with hematologic cancers had a significantly higher mortality relative to patients with solid cancers after accounting for confounders including ECOG performance status and active cancer status. We performed flow cytometric and serologic analyses of 106 cancer patients and 113 non-cancer controls from two additional cohorts at Penn and Memorial Sloan Kettering Cancer Center. Patients with solid cancers exhibited an immune phenotype similar to non-cancer patients during acute COVID-19 whereas patients with hematologic cancers had significant impairment of B cells and SARS-CoV-2-specific antibody responses. High dimensional analysis of flow cytometric data revealed 5 distinct immune phenotypes. An immune phenotype characterized by CD8 T cell depletion was associated with a high viral load and the highest mortality of 71%, among all cancer patients. In contrast, despite impaired B cell responses, patients with hematologic cancers and preserved CD8 T cells had a lower viral load and mortality. These data highlight the importance of CD8 T cells in acute COVID-19, particularly in the setting of impaired humoral immunity. Further, depletion of B cells with anti-CD20 therapy resulted in almost complete abrogation of SARS-CoV-2-specific IgG and IgM antibodies, but was not associated with increased mortality compared to other hematologic cancers, when adequate CD8 T cells were present. Finally, higher CD8 T cell counts were associated with improved overall survival in patients with hematologic cancers. Thus, CD8 T cells likely compensate for deficient humoral immunity and influence clinical recovery of COVID-19. These observations have important implications for cancer and COVID-19-directed treatments, immunosuppressive therapies, and for understanding the role of B and T cells in acute COVID-19.
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http://dx.doi.org/10.21203/rs.3.rs-162289/v1DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7872363PMC
February 2021

Elucidating the Importance of DOT1L Recruitment in MLL-AF9 Leukemia and Hematopoiesis.

Cancers (Basel) 2021 Feb 5;13(4). Epub 2021 Feb 5.

Molecular and Celular Graduate Program, Department of Pathology, University of Michigan Medical School, Ann Arbor, MI 48104, USA.

gene rearrangements underlie the pathogenesis of aggressive MLL-driven acute leukemia. AF9, one of the most common MLL-fusion partners, recruits the histone H3K79 methyltransferase DOT1L to MLL target genes, constitutively activating transcription of pro-leukemic targets. DOT1L has emerged as a therapeutic target in patients with MLL-driven leukemia. However, global DOT1L enzymatic inhibition may lead to off-target toxicities in non-leukemic cells that could decrease the therapeutic index of DOT1L inhibitors. To bypass this problem, we developed a novel approach targeting specific protein-protein interactions (PPIs) that mediate DOT1L recruitment to MLL target genes, and compared the effects of enzymatic and PPIs inhibition on leukemic and non-leukemic hematopoiesis. MLL-AF9 cell lines were engineered to carry mutant constructs with a defective AF9 interaction site or lacking enzymatic activity. In cell lines expressing a mutant with defective AF9 binding, we observed complete disruption of DOT1L recruitment to critical target genes and inhibition of leukemic cell growth. To evaluate the overall impact of DOT1L loss in non-leukemic hematopoiesis, we first assessed the impact of acute inactivation in adult mouse bone marrow. We observed a rapid reduction in myeloid progenitor cell numbers within 7 days, followed by a loss of long-term hematopoietic stem cells. Furthermore, WT and PPI-deficient DOT1L mutants but not an enzymatically inactive DOT1L mutant were able to rescue sustained hematopoiesis. These data show that the AF9-DOT1L interaction is dispensable in non-leukemic hematopoiesis. Our findings support targeting of the MLL-AF9-DOT1L interaction as a promising therapeutic strategy that is selectively toxic to MLL-driven leukemic cells.
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http://dx.doi.org/10.3390/cancers13040642DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7914713PMC
February 2021

Rates of COVID-19-Related Outcomes in Cancer Compared With Noncancer Patients.

JNCI Cancer Spectr 2021 Feb 21;5(1):pkaa120. Epub 2021 Jan 21.

Division of Hematology/Oncology, Department of Medicine, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA.

Cancer patients are a vulnerable population postulated to be at higher risk for severe coronavirus disease 2019 (COVID-19) infection. Increased COVID-19 morbidity and mortality in cancer patients may be attributable to age, comorbidities, smoking, health care exposure, and cancer treatments, and partially to the cancer itself. Most studies to date have focused on hospitalized patients with severe COVID-19, thereby limiting the generalizability and interpretability of the association between cancer and COVID-19 severity. We compared outcomes of SARS-CoV-2 infection in 323 patients enrolled in a population-based study before the pandemic (n = 67 cancer patients; n = 256 noncancer patients). After adjusting for demographics, smoking status, and comorbidities, a diagnosis of cancer was independently associated with higher odds of hospitalization (odds ratio = 2.16, 95% confidence interval = 1.12 to 4.18) and 30-day mortality (odds ratio = 5.67, 95% confidence interval = 1.49 to 21.59). These associations were primarily driven by patients with active cancer. These results emphasize the critical importance of preventing SARS-CoV-2 exposure and mitigating infection in cancer patients.
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http://dx.doi.org/10.1093/jncics/pkaa120DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7853171PMC
February 2021

BAFF Promotes Heightened BCR Responsiveness and Manifestations of Chronic GVHD after Allogeneic Stem Cell Transplantation.

Blood 2021 Feb 3. Epub 2021 Feb 3.

Duke University, Durham, North Carolina, United States.

Chronic graft versus host disease (cGVHD) patients have increased B cell-activating factor (BAFF) levels, but whether BAFF promotes disease after allogeneic bone marrow transplantation (allo-BMT) remains unknown. In a major MHC-mismatched model with cGVHD-like manifestations we first examined B-lymphopenic mMT allo-BMT recipients and found that increased BAFF levels in cGVHD mice were not merely a reflection of B cell number. Mice that later developed cGVHD, had significantly increased numbers of recipient fibroblastic reticular cells (FRCs) with higher BAFF transcript levels. Increased BAFF production by donor cells also likely contributed to cGVHD since BAFF transcript in CD4+ T cells from diseased mice and patients was increased. Chronic GVHD manifestations in mice associated with high BAFF/B cell ratios and persistence of B Cell Receptor (BCR)-activated B cells in peripheral blood and lesional tissue. By employing BAFF transgenic (Tg) mice donor cells, we addressed whether high BAFF contributed to BCR activation in cGVHD. BAFF increased NOTCH2 expression on B cells, augmenting BCR-responsiveness to surrogate antigen and NOTCH ligand. BAFF-Tg B cells had significantly increased protein levels of the proximal BCR signaling molecule SYK, and high SYK protein was maintained by BAFF after in vitro BCR-activation or when alloantigen was present in vivo. Using T-cell depleted (BM only) BAFF-Tg donors, we found that BAFF promoted cGVHD manifestations, circulating GL7+ B cells and alloantibody production. We demonstrate that pathological production of BAFF promotes an altered B-cell compartment and augments BCR-responsiveness. Our findings compel studies of therapeutic targeting of BAFF and BCR pathways in cGVHD patients.
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http://dx.doi.org/10.1182/blood.2020008040DOI Listing
February 2021

SARS-CoV-2 seropositivity and seroconversion in patients undergoing active cancer-directed therapy.

medRxiv 2021 Jan 16. Epub 2021 Jan 16.

Multiple studies have demonstrated the negative impact of cancer care delays during the COVID-19 pandemic, and transmission mitigation techniques are imperative for continued cancer care delivery. To gauge the effectiveness of these measures at the University of Pennsylvania, we conducted a longitudinal study of SARS-CoV-2 antibody seropositivity and seroconversion in patients presenting to infusion centers for cancer-directed therapy between 5/21/2020 and 10/8/2020. Participants completed questionnaires and had up to five serial blood collections. Of 124 enrolled patients, only two (1.6%) had detectable SARS-CoV-2 antibodies on initial blood draw, and no initially seronegative patients developed newly detectable antibodies on subsequent blood draw(s), corresponding to a seroconversion rate of 0% (95%CI 0.0-4.1%) over 14.8 person-years of follow up, with a median of 13 healthcare visits per patient. These results suggest that cancer patients receiving in-person care at a facility with aggressive mitigation efforts have an extremely low likelihood of COVID-19 infection.
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http://dx.doi.org/10.1101/2021.01.15.21249810DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7814843PMC
January 2021

Notch-Regulated Dendritic Cells Restrain Inflammation-Associated Colorectal Carcinogenesis.

Cancer Immunol Res 2021 Mar 13;9(3):348-361. Epub 2021 Jan 13.

Department of Pathology, Case Western Reserve University, Cleveland, Ohio.

Conventional dendritic cells (cDC) play a central role in T-cell antitumor responses. We studied the significance of Notch-regulated DC immune responses in a mouse model of colitis-associated colorectal cancer in which there is epithelial downregulation of Notch/Hes1 signaling. This defect phenocopies that caused by (GDP-mannose 4,6-dehydratase) mutation in human colorectal cancers. We found that, although wild-type immune cells restrained dysplasia progression and decreased the incidence of adenocarcinoma in chimeric mice, the immune system with Notch2 deleted in all blood lineages or in only DCs promoted inflammation-associated transformation. Notch2 signaling deficiency not only impaired cDC terminal differentiation, but also downregulated CCR7 expression, reduced DC migration, and suppressed antigen cross-presentation to CD8 T cells. Transfer of Notch-primed DCs restrained inflammation-associated dysplasia progression. Consistent with the mouse data, we observed a correlation between infiltrating cDC1 and Notch2 signaling in human colorectal cancers and found that -mutant colorectal cancers showed decreased CCR7 expression and suppressed cDC1 signature gene expression. Suppressed cDC1 gene signature expression in human colorectal cancer was associated with a poor prognosis. In summary, our study supports an important role for Notch2 signaling in cDC1-mediated antitumor immunity and indicates that Notch2-controlled DCs restrain inflammation-associated colon cancer development in mice.
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http://dx.doi.org/10.1158/2326-6066.CIR-20-0428DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7925430PMC
March 2021

SARS-CoV-2 mRNA Vaccines Foster Potent Antigen-Specific Germinal Center Responses Associated with Neutralizing Antibody Generation.

Immunity 2020 12 21;53(6):1281-1295.e5. Epub 2020 Nov 21.

Department of Microbiology, Center for Research on Coronavirus and Other Emerging Pathogens, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA. Electronic address:

The deployment of effective vaccines against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is critical to eradicate the coronavirus disease 2019 (COVID-19) pandemic. Many licensed vaccines confer protection by inducing long-lived plasma cells (LLPCs) and memory B cells (MBCs), cell types canonically generated during germinal center (GC) reactions. Here, we directly compared two vaccine platforms-mRNA vaccines and a recombinant protein formulated with an MF59-like adjuvant-looking for their abilities to quantitatively and qualitatively shape SARS-CoV-2-specific primary GC responses over time. We demonstrated that a single immunization with SARS-CoV-2 mRNA, but not with the recombinant protein vaccine, elicited potent SARS-CoV-2-specific GC B and T follicular helper (Tfh) cell responses as well as LLPCs and MBCs. Importantly, GC responses strongly correlated with neutralizing antibody production. mRNA vaccines more efficiently induced key regulators of the Tfh cell program and influenced the functional properties of Tfh cells. Overall, this study identifies SARS-CoV-2 mRNA vaccines as strong candidates for promoting robust GC-derived immune responses.
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http://dx.doi.org/10.1016/j.immuni.2020.11.009DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7680029PMC
December 2020

International evidence-based consensus diagnostic and treatment guidelines for unicentric Castleman disease.

Blood Adv 2020 12;4(23):6039-6050

Division of Translational Medicine and Human Genetics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA.

Castleman disease (CD) includes a group of rare and heterogeneous disorders with characteristic lymph node histopathological abnormalities. CD can occur in a single lymph node station, which is referred to as unicentric CD (UCD). CD can also involve multicentric lymphadenopathy and inflammatory symptoms (multicentric CD [MCD]). MCD includes human herpesvirus-8 (HHV-8)-associated MCD, POEMS-associated MCD, and HHV-8-/idiopathic MCD (iMCD). The first-ever diagnostic and treatment guidelines were recently developed for iMCD by an international expert consortium convened by the Castleman Disease Collaborative Network (CDCN). The focus of this report is to establish similar guidelines for the management of UCD. To this purpose, an international working group of 42 experts from 10 countries was convened to establish consensus recommendations based on review of treatment in published cases of UCD, the CDCN ACCELERATE registry, and expert opinion. Complete surgical resection is often curative and is therefore the preferred first-line therapy, if possible. The management of unresectable UCD is more challenging. Existing evidence supports that asymptomatic unresectable UCD may be observed. The anti-interleukin-6 monoclonal antibody siltuximab should be considered for unresectable UCD patients with an inflammatory syndrome. Unresectable UCD that is symptomatic as a result of compression of vital neighboring structures may be rendered amenable to resection by medical therapy (eg, rituximab, steroids), radiotherapy, or embolization. Further research is needed in UCD patients with persisting constitutional symptoms despite complete excision and normal laboratory markers. We hope that these guidelines will improve outcomes in UCD and help treating physicians decide the best therapeutic approach for their patients.
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http://dx.doi.org/10.1182/bloodadvances.2020003334DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7724917PMC
December 2020

Efficacy and Safety of Hydroxychloroquine vs Placebo for Pre-exposure SARS-CoV-2 Prophylaxis Among Health Care Workers: A Randomized Clinical Trial.

JAMA Intern Med 2021 02;181(2):195-202

Abramson Cancer Center and Division of Hematology-Oncology, Department of Medicine, University of Pennsylvania, Philadelphia.

Importance: Health care workers (HCWs) caring for patients with coronavirus disease 2019 (COVID-19) are at risk of exposure to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Currently, to our knowledge, there is no effective pharmacologic prophylaxis for individuals at risk.

Objective: To evaluate the efficacy of hydroxychloroquine to prevent transmission of SARS-CoV-2 in hospital-based HCWs with exposure to patients with COVID-19 using a pre-exposure prophylaxis strategy.

Design, Setting, And Participants: This randomized, double-blind, placebo-controlled clinical trial (the Prevention and Treatment of COVID-19 With Hydroxychloroquine Study) was conducted at 2 tertiary urban hospitals, with enrollment from April 9, 2020, to July 14, 2020; follow-up ended August 4, 2020. The trial randomized 132 full-time, hospital-based HCWs (physicians, nurses, certified nursing assistants, emergency technicians, and respiratory therapists), of whom 125 were initially asymptomatic and had negative results for SARS-CoV-2 by nasopharyngeal swab. The trial was terminated early for futility before reaching a planned enrollment of 200 participants.

Interventions: Hydroxychloroquine, 600 mg, daily, or size-matched placebo taken orally for 8 weeks.

Main Outcomes And Measures: The primary outcome was the incidence of SARS-CoV-2 infection as determined by a nasopharyngeal swab during the 8 weeks of treatment. Secondary outcomes included adverse effects, treatment discontinuation, presence of SARS-CoV-2 antibodies, frequency of QTc prolongation, and clinical outcomes for SARS-CoV-2-positive participants.

Results: Of the 132 randomized participants (median age, 33 years [range, 20-66 years]; 91 women [69%]), 125 (94.7%) were evaluable for the primary outcome. There was no significant difference in infection rates in participants randomized to receive hydroxychloroquine compared with placebo (4 of 64 [6.3%] vs 4 of 61 [6.6%]; P > .99). Mild adverse events were more common in participants taking hydroxychloroquine compared with placebo (45% vs 26%; P = .04); rates of treatment discontinuation were similar in both arms (19% vs 16%; P = .81). The median change in QTc (baseline to 4-week evaluation) did not differ between arms (hydroxychloroquine: 4 milliseconds; 95% CI, -9 to 17; vs placebo: 3 milliseconds; 95% CI, -5 to 11; P = .98). Of the 8 participants with positive results for SARS-CoV-2 (6.4%), 6 developed viral symptoms; none required hospitalization, and all clinically recovered.

Conclusions And Relevance: In this randomized clinical trial, although limited by early termination, there was no clinical benefit of hydroxychloroquine administered daily for 8 weeks as pre-exposure prophylaxis in hospital-based HCWs exposed to patients with COVID-19.

Trial Registration: ClinicalTrials.gov Identifier: NCT04329923.
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http://dx.doi.org/10.1001/jamainternmed.2020.6319DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7527945PMC
February 2021

Repurposing a novel anti-cancer RXR agonist to attenuate murine acute GVHD and maintain graft-versus-leukemia responses.

Blood 2021 Feb;137(8):1090-1103

Division of Blood and Marrow Transplantation, Department of Pediatrics, Masonic Cancer Center, University of Minnesota, Minneapolis, MN.

The nuclear receptor (NR) subclass, retinoid X receptors (RXRs), exert immunomodulatory functions that control inflammation and metabolism via homodimers and heterodimers, with several other NRs, including retinoic acid receptors. IRX4204 is a novel, highly specific RXR agonist in clinical trials that potently and selectively activates RXR homodimers, but not heterodimers. In this study, in vivo IRX4204 compared favorably with FK506 in abrogating acute graft-versus-host disease (GVHD), which was associated with inhibiting allogeneic donor T-cell proliferation, reducing T-helper 1 differentiation, and promoting regulatory T-cell (Treg) generation. Recipient IRX4204 treatment reduced intestinal injury and decreased IFN-γ and TNF-α serum levels. Transcriptional analysis of donor T cells isolated from intestines of GVHD mice treated with IRX4204 revealed significant decreases in transcripts regulating proinflammatory pathways. In vitro, inducible Treg differentiation from naive CD4+ T cells was enhanced by IRX4204. In vivo, IRX4204 increased the conversion of donor Foxp3- T cells into peripheral Foxp3+ Tregs in GVHD mice. Using Foxp3 lineage-tracer mice in which both the origin and current FoxP3 expression of Tregs can be tracked, we demonstrated that IRX4204 supports Treg stability. Despite favoring Tregs and reducing Th1 differentiation, IRX4204-treated recipients maintained graft-versus-leukemia responses against both leukemia and lymphoma cells. Notably, IRX4204 reduced in vitro human T-cell proliferation and enhanced Treg generation in mixed lymphocyte reaction cultures. Collectively, these beneficial effects indicate that targeting RXRs with IRX4204 could be a novel approach to preventing acute GVHD in the clinic.
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http://dx.doi.org/10.1182/blood.2020005628DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7907720PMC
February 2021

Single-Cell Analyses Identify Brain Mural Cells Expressing CD19 as Potential Off-Tumor Targets for CAR-T Immunotherapies.

Cell 2020 Oct 21;183(1):126-142.e17. Epub 2020 Sep 21.

Parker Institute for Cancer Immunotherapy, Stanford University School of Medicine, Stanford, CA, USA; Department of Pathology, Stanford University School of Medicine, Stanford, CA, USA. Electronic address:

CD19-directed immunotherapies are clinically effective for treating B cell malignancies but also cause a high incidence of neurotoxicity. A subset of patients treated with chimeric antigen receptor (CAR) T cells or bispecific T cell engager (BiTE) antibodies display severe neurotoxicity, including fatal cerebral edema associated with T cell infiltration into the brain. Here, we report that mural cells, which surround the endothelium and are critical for blood-brain-barrier integrity, express CD19. We identify CD19 expression in brain mural cells using single-cell RNA sequencing data and confirm perivascular staining at the protein level. CD19 expression in the brain begins early in development alongside the emergence of mural cell lineages and persists throughout adulthood across brain regions. Mouse mural cells demonstrate lower levels of Cd19 expression, suggesting limitations in preclinical animal models of neurotoxicity. These data suggest an on-target mechanism for neurotoxicity in CD19-directed therapies and highlight the utility of human single-cell atlases for designing immunotherapies.
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http://dx.doi.org/10.1016/j.cell.2020.08.022DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7640763PMC
October 2020

Rates of COVID-19-related Outcomes in Cancer compared to non-Cancer Patients.

medRxiv 2020 Aug 15. Epub 2020 Aug 15.

Division of Hematology/Oncology, Department of Medicine, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA, 19104.

Cancer patients are a vulnerable population postulated to be at higher risk for severe COVID-19 infection. Increased COVID-19 morbidity and mortality in cancer patients may be attributable to age, comorbidities, smoking, healthcare exposure, and cancer treatments, and partially to the cancer itself. Most studies to date have focused on hospitalized patients with severe COVID-19, thereby limiting the generalizability and interpretability of the association between cancer and COVID-19 severity. We compared outcomes of SARS-CoV-2 infection in 323 patients enrolled prior to the pandemic in a large academic biobank (n=67 cancer patients and n=256 non-cancer patients). After adjusting for demographics, smoking status, and comorbidities, a diagnosis of cancer was independently associated with higher odds of hospitalization (OR 2.16, 95% CI 1.12-4.18) and 30-day mortality (OR 5.67, CI 1.49-21.59). These associations were primarily driven by patients with active cancer. These results emphasize the critical importance of preventing SARS-CoV-2 exposure and mitigating infection in cancer patients.
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http://dx.doi.org/10.1101/2020.08.14.20174961DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7430598PMC
August 2020

Notch signaling at the crossroads of innate and adaptive immunity.

J Leukoc Biol 2021 03 18;109(3):535-548. Epub 2020 Jun 18.

Immunology Graduate Group, University of Pennsylvania, Philadelphia, Pennsylvania, USA.

Notch signaling is an evolutionarily conserved cell-to-cell signaling pathway that regulates cellular differentiation and function across multiple tissue types and developmental stages. In this review, we discuss our current understanding of Notch signaling in mammalian innate and adaptive immunity. The importance of Notch signaling is pervasive throughout the immune system, as it elicits lineage and context-dependent effects in a wide repertoire of cells. Although regulation of binary cell fate decisions encompasses many of the functions first ascribed to Notch in the immune system, recent advances in the field have refined and expanded our view of the Notch pathway beyond this initial concept. From establishing T cell identity in the thymus to regulating mature T cell function in the periphery, the Notch pathway is an essential, recurring signal for the T cell lineage. Among B cells, Notch signaling is required for the development and maintenance of marginal zone B cells in the spleen. Emerging roles for Notch signaling in innate and innate-like lineages such as classical dendritic cells and innate lymphoid cells are likewise coming into view. Lastly, we speculate on the molecular underpinnings that shape the activity and versatility of the Notch pathway.
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http://dx.doi.org/10.1002/JLB.1RI0520-138RDOI Listing
March 2021

One-two punch injury to tolerance mechanisms in graft-versus-host disease.

J Clin Invest 2020 04;130(4):1625-1628

Division of Hematology-Oncology, Department of Medicine, and.

Chronic graft-versus-host disease (GVHD) is a major complication of allogeneic hematopoietic cell transplantation that resembles autoimmunity, with unclear pathogenesis and few effective therapeutic options. In this issue of the JCI, Dertschnig et al. used mouse models to investigate the basis of T cell autoreactivity following GVHD. Notably, GVHD caused irreversible damage to a population of tolerogenic stromal cells that display peripheral tissue-restricted antigens in lymph nodes, which impaired their capacity to purge and suppress autoreactive T cells. Together with damage to central tolerance mechanisms in the thymus, these findings outline a critical one-two punch injury that profoundly disrupts immune tolerance in this devastating disease.
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http://dx.doi.org/10.1172/JCI136139DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7108886PMC
April 2020

GCNT1-Mediated -Glycosylation of the Sialomucin CD43 Is a Sensitive Indicator of Notch Signaling in Activated T Cells.

J Immunol 2020 03 14;204(6):1674-1688. Epub 2020 Feb 14.

Division of Hematology-Oncology, Department of Medicine, University of Pennsylvania Perelman School of Medicine, Philadelphia, PA 19104;

Notch signaling is emerging as a critical regulator of T cell activation and function. However, there is no reliable cell surface indicator of Notch signaling across activated T cell subsets. In this study, we show that Notch signals induce upregulated expression of the glycosyltransferase gene in T cells mediating graft-versus-host disease after allogeneic bone marrow transplantation in mice. To determine if mediated -glycosylation could be used as a Notch signaling reporter, we quantified the core-2 -glycoform of CD43 in multiple T cell subsets during graft-versus-host disease. Pharmacological blockade of Delta-like Notch ligands abrogated core-2 -glycosylation in a dose-dependent manner after allogeneic bone marrow transplantation, both in donor-derived CD4 and CD8 effector T cells and in Foxp3 regulatory T cells. CD43 core-2 -glycosylation depended on cell-intrinsic canonical Notch signals and identified CD4 and CD8 T cells with high cytokine-producing ability. -deficient T cells still drove lethal alloreactivity, showing that core-2 -glycosylation predicted, but did not cause, Notch-dependent T cell pathogenicity. Using core-2 -glycosylation as a marker of Notch signaling, we identified Ccl19-Cre fibroblastic stromal cells as critical sources of Delta-like ligands in graft-versus-host responses irrespective of conditioning intensity. Core-2 -glycosylation also reported Notch signaling in CD8 T cell responses to dendritic cell immunization, infection, and viral infection. Thus, we uncovered a role for Notch in controlling core-2 -glycosylation and identified a cell surface marker to quantify Notch signals in multiple immunological contexts. Our findings will help refine our understanding of the regulation, cellular source, and timing of Notch signals in T cell immunity.
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http://dx.doi.org/10.4049/jimmunol.1901194DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7306398PMC
March 2020

Menin inhibitor MI-3454 induces remission in MLL1-rearranged and NPM1-mutated models of leukemia.

J Clin Invest 2020 02;130(2):981-997

Department of Pathology, University of Michigan, Ann Arbor, Michigan, USA.

The protein-protein interaction between menin and mixed lineage leukemia 1 (MLL1) plays a critical role in acute leukemias with translocations of the MLL1 gene or with mutations in the nucleophosmin 1 (NPM1) gene. As a step toward clinical translation of menin-MLL1 inhibitors, we report development of MI-3454, a highly potent and orally bioavailable inhibitor of the menin-MLL1 interaction. MI-3454 profoundly inhibited proliferation and induced differentiation in acute leukemia cells and primary patient samples with MLL1 translocations or NPM1 mutations. When applied as a single agent, MI-3454 induced complete remission or regression of leukemia in mouse models of MLL1-rearranged or NPM1-mutated leukemia, including patient-derived xenograft models, through downregulation of key genes involved in leukemogenesis. We also identified MEIS1 as a potential pharmacodynamic biomarker of treatment response with MI-3454 in leukemia, and demonstrated that this compound is well tolerated and did not impair normal hematopoiesis in mice. Overall, this study demonstrates, for the first time to our knowledge, profound activity of the menin-MLL1 inhibitor as a single agent in clinically relevant PDX models of leukemia. These data provide a strong rationale for clinical translation of MI-3454 or its analogs for leukemia patients with MLL1 rearrangements or NPM1 mutations.
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http://dx.doi.org/10.1172/JCI129126DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6994154PMC
February 2020

Inhibition of inositol kinase B controls acute and chronic graft-versus-host disease.

Blood 2020 01;135(1):28-40

Division of Blood and Marrow Transplantation, Department of Pediatrics, Masonic Cancer Center, University of Minnesota, Minneapolis, MN.

T-cell activation releases inositol 1,4,5-trisphosphate (IP3), inducing cytoplasmic calcium (Ca2+) influx. In turn, inositol 1,4,5-trisphosphate 3-kinase B (Itpkb) phosphorylates IP3 to negatively regulate and thereby tightly control Ca2+ fluxes that are essential for mature T-cell activation and differentiation and protection from cell death. Itpkb pathway inhibition increases intracellular Ca2+, induces apoptosis of activated T cells, and can control T-cell-mediated autoimmunity. In this study, we employed genetic and pharmacological approaches to inhibit Itpkb signaling as a means of controlling graft-versus-host disease (GVHD). Murine-induced, Itpkb-deleted (Itpkb-/-) T cells attenuated acute GVHD in 2 models without eliminating A20-luciferase B-cell lymphoma graft-versus-leukemia (GVL). A highly potent, selective inhibitor, GNF362, ameliorated acute GVHD without impairing GVL against 2 acute myeloid leukemia lines (MLL-AF9-eGFP and C1498-luciferase). Compared with FK506, GNF362 more selectively deleted donor alloreactive vs nominal antigen-responsive T cells. Consistent with these data and as compared with FK506, GNF362 had favorable acute GVHD and GVL properties against MLL-AF9-eGFP cells. In chronic GVHD preclinical models that have a pathophysiology distinct from acute GVHD, Itpkb-/- donor T cells reduced active chronic GVHD in a multiorgan system model of bronchiolitis obliterans (BO), driven by germinal center reactions and resulting in target organ fibrosis. GNF362 treatment reduced active chronic GVHD in both BO and scleroderma models. Thus, intact Itpkb signaling is essential to drive acute GVHD pathogenesis and sustain active chronic GVHD, pointing toward a novel clinical application to prevent acute or treat chronic GVHD.
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http://dx.doi.org/10.1182/blood.2019000032DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6940197PMC
January 2020

Notch signalling in T cell homeostasis and differentiation.

Open Biol 2019 11 6;9(11):190187. Epub 2019 Nov 6.

Division of Hematology-Oncology, Department of Medicine, Abramson Family Cancer Research Institute, University of Pennsylvania Perelman School of Medicine, Philadelphia, PA 19104, USA.

The evolutionarily conserved Notch signalling pathway regulates the differentiation and function of mature T lymphocytes with major context-dependent consequences in host defence, autoimmunity and alloimmunity. The emerging effects of Notch signalling in T cell responses build upon a more established role for Notch in T cell development. Here, we provide a critical review of this burgeoning literature to make sense of what has been learned so far and highlight the experimental strategies that have been most useful in gleaning physiologically relevant information. We outline the functional consequences of Notch signalling in mature T cells in addition to key specific Notch ligand-receptor interactions and downstream molecular signalling pathways. Our goal is to help clarify future directions for this expanding body of work and the best approaches to answer important open questions.
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http://dx.doi.org/10.1098/rsob.190187DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6893402PMC
November 2019

Donor and host B7-H4 expression negatively regulates acute graft-versus-host disease lethality.

JCI Insight 2019 10 3;4(19). Epub 2019 Oct 3.

Masonic Cancer Center and Department of Pediatrics, Division of Blood and Marrow Transplantation, University of Minnesota, Minneapolis, Minnesota, USA.

B7-H4 is a negative regulatory B7 family member. We investigated the role of host and donor B7-H4 in regulating acute graft-versus-host disease (GVHD). Allogeneic donor T cells infused into B7-H4-/- versus WT recipients markedly accelerated GVHD-induced lethality. Chimera studies pointed toward B7-H4 expression on host hematopoietic cells as more critical than parenchymal cells in controlling GVHD. Rapid mortality in B7-H4-/- recipients was associated with increased donor T cell expansion, gut T cell homing and loss of intestinal epithelial integrity, increased T effector function (proliferation, proinflammatory cytokines, cytolytic molecules), and reduced apoptosis. Higher metabolic demands of rapidly proliferating donor T cells in B7-H4-/- versus WT recipients required multiple metabolic pathways, increased extracellular acidification rates (ECARs) and oxygen consumption rates (OCRs), and increased expression of fuel substrate transporters. During GVHD, B7-H4 expression was upregulated on allogeneic WT donor T cells. B7-H4-/- donor T cells given to WT recipients increased GVHD mortality and had function and biological properties similar to WT T cells from allogeneic B7-H4-/- recipients. Graft-versus-leukemia responses were intact regardless as to whether B7-H4-/- mice were used as hosts or donors. Taken together, these data provide new insights into the negative regulatory processes that control GVHD and provide support for developing therapeutic strategies directed toward the B7-H4 pathway.
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http://dx.doi.org/10.1172/jci.insight.127716DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6795410PMC
October 2019

Compartmentalized effects of aging on group 2 innate lymphoid cell development and function.

Aging Cell 2019 12 20;18(6):e13019. Epub 2019 Aug 20.

Department of Immunology and Microbial Disease, Albany Medical College, Albany, New York, USA.

The effects of aging on innate immunity and the resulting impacts on immunosenescence remain poorly understood. Here, we report that aging induces compartmentalized changes to the development and function of group 2 innate lymphoid cells (ILC2), an ILC subset implicated in pulmonary homeostasis and tissue repair. Aging enhances bone marrow early ILC2 development through Notch signaling, but the newly generated circulating ILC2 are unable to settle in the lungs to replenish the concomitantly declining mature lung ILC2 pool in aged mice. Aged lung ILC2 are transcriptomically heterogeneous and functionally compromised, failing to produce cytokines at homeostasis and during influenza infection. They have reduced expression of Cyp2e1, a cytochrome P450 oxidase required for optimal ILC2 function. Transfer of lung ILC2 from young mice enhances resistance to influenza infection in old mice. These data highlight compartmentalized effects of aging on ILC and indicate that targeting tissue-resident ILCs might unlock therapies to enhance resistance to infections and diseases in the elderly.
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http://dx.doi.org/10.1111/acel.13019DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6826140PMC
December 2019

Early Notch Signals Induce a Pathogenic Molecular Signature during Priming of Alloantigen-Specific Conventional CD4 T Cells in Graft-versus-Host Disease.

J Immunol 2019 07 10;203(2):557-568. Epub 2019 Jun 10.

Life Sciences Institute, University of Michigan, Ann Arbor, MI 48109;

Graft-versus-host disease (GVHD) is the most serious complication of allogeneic hematopoietic cell transplantation. Notch signals delivered during the first 48 h after transplantation drive proinflammatory cytokine production in conventional T cells (Tconv) and inhibit the expansion of regulatory T cells (Tregs). Short-term Notch inhibition induces long-term GVHD protection. However, it remains unknown whether Notch blockade blunts GVHD through its effects on Tconv, Tregs, or both and what early Notch-regulated molecular events occur in alloantigen-specific T cells. To address these questions, we engineered T cell grafts to achieve selective Notch blockade in Tconv versus Tregs and evaluated their capacity to trigger GVHD in mice. Notch blockade in Tconv was essential for GVHD protection as GVHD severity was similar in the recipients of wild-type Tconv combined with Notch-deprived versus wild-type Tregs. To identify the impact of Notch signaling on the earliest steps of T cell activation in vivo, we established a new acute GVHD model mediated by clonal alloantigen-specific 4C CD4 Tconv. Notch-deprived 4C T cells had preserved early steps of activation, IL-2 production, proliferation, and Th cell polarization. In contrast, Notch inhibition dampened IFN-γ and IL-17 production, diminished mTORC1 and ERK1/2 activation, and impaired transcription of a subset of Myc-regulated genes. The distinct Notch-regulated signature had minimal overlap with known Notch targets in T cell leukemia and developing T cells, highlighting the specific impact of Notch signaling in mature T cells. Our findings uncover a unique molecular program associated with the pathogenic effects of Notch in T cells at the earliest stages of GVHD.
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http://dx.doi.org/10.4049/jimmunol.1900192DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6615974PMC
July 2019

The PAF1c Subunit CDC73 Is Required for Mouse Hematopoietic Stem Cell Maintenance but Displays Leukemia-Specific Gene Regulation.

Stem Cell Reports 2019 05 25;12(5):1069-1083. Epub 2019 Apr 25.

Department of Pathology, University of Michigan Medical School, 7520B Medical Science Research Building I, 1150 W. Medical Center Dr., Ann Arbor, MI 48109-5602, USA. Electronic address:

The Polymerase Associated Factor 1 complex (PAF1c) functions at the interface of epigenetics and gene transcription. The PAF1c is required for MLL fusion-driven acute myeloid leukemia (AML) through direct regulation of pro-leukemic target genes such as Hoxa9 and Meis1. However, the role of the PAF1c in normal hematopoiesis is unknown. Here, we discovered that the PAF1c subunit, CDC73, is required for both fetal and adult hematopoiesis. Loss of Cdc73 in hematopoietic cells is lethal because of extensive bone marrow failure. Cdc73 has an essential cell-autonomous role for adult hematopoietic stem cell function in vivo, and deletion of Cdc73 results in cell-cycle defects in hematopoietic progenitors. Gene expression profiling indicated a differential regulation of Hoxa9/Meis1 gene programs by CDC73 in progenitors compared with AML cells, suggesting disease-specific functions. Thus, the PAF1c subunit, CDC73 is essential for hematopoietic stem cell function but exhibits leukemia-specific regulation of self-renewal gene programs in AML cells.
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http://dx.doi.org/10.1016/j.stemcr.2019.03.010DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6524170PMC
May 2019

Targeting PI3Kδ function for amelioration of murine chronic graft-versus-host disease.

Am J Transplant 2019 06 19;19(6):1820-1830. Epub 2019 Mar 19.

Division of Blood and Marrow Transplantation, Department of Pediatrics, University of Minnesota, Minneapolis, Minnesota.

Chronic graft-versus-host disease (cGVHD) is a leading cause of morbidity and mortality following allotransplant. Activated donor effector T cells can differentiate into pathogenic T helper (Th)-17 cells and germinal center (GC)-promoting T follicular helper (Tfh) cells, resulting in cGVHD. Phosphoinositide-3-kinase-δ (PI3Kδ), a lipid kinase, is critical for activated T cell survival, proliferation, differentiation, and metabolism. We demonstrate PI3Kδ activity in donor T cells that become Tfh cells is required for cGVHD in a nonsclerodermatous multiorgan system disease model that includes bronchiolitis obliterans (BO), dependent upon GC B cells, Tfhs, and counterbalanced by T follicular regulatory cells, each requiring PI3Kδ signaling for function and survival. Although B cells rely on PI3Kδ pathway signaling and GC formation is disrupted resulting in a substantial decrease in Ig production, PI3Kδ kinase-dead mutant donor bone marrow-derived GC B cells still supported BO cGVHD generation. A PI3Kδ-specific inhibitor, compound GS-649443, that has superior potency to idelalisib while maintaining selectivity, reduced cGVHD in mice with active disease. In a Th1-dependent and Th17-associated scleroderma model, GS-649443 effectively treated mice with active cGVHD. These data provide a foundation for clinical trials of US Food and Drug Administration (FDA)-approved PI3Kδ inhibitors for cGVHD therapy in patients.
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http://dx.doi.org/10.1111/ajt.15305DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6538456PMC
June 2019

Small-molecule BCL6 inhibitor effectively treats mice with nonsclerodermatous chronic graft-versus-host disease.

Blood 2019 01 2;133(1):94-99. Epub 2018 Oct 2.

Division of Blood and Marrow Transplantation, University of Minnesota, Minneapolis, MN.

Patient outcomes for steroid-dependent or -refractory chronic graft-versus-host diesease (cGVHD) are poor, and only ibrutinib has been US Food and Drug Administration (FDA) approved for this indication. cGVHD is often driven by the germinal center (GC) reaction, in which T follicular helper cells interact with GC B cells to produce antibodies that are associated with disease pathogenesis. The transcriptional corepressor B-cell lymphoma 6 (BCL6) is a member of the Broad-complex, Tramtrack, and Bric-abrac/poxvirus and zinc finger (BTB/POZ) transcription factor family and master regulator of the immune cells in the GC reaction. We demonstrate that BCL6 expression in both donor T cells and B cells is necessary for cGVHD development, pointing to BCL6 as a therapeutic cGVHD target. A small-molecule BCL6 inhibitor reversed active cGVHD in a mouse model of multiorgan system injury with bronchiolitis obliterans associated with a robust GC reaction, but not in cGVHD mice with scleroderma as the prominent manifestation. For cGVHD patients with antibody-driven cGVHD, targeting of BCL6 represents a new approach with specificity for a master GC regulator that would extend the currently available second-line agents.
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http://dx.doi.org/10.1182/blood-2018-03-839993DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6318432PMC
January 2019

Notch signaling mediated by Delta-like ligands 1 and 4 controls the pathogenesis of chronic GVHD in mice.

Blood 2018 11 4;132(20):2188-2200. Epub 2018 Sep 4.

Division of Hematology/Oncology, Department of Internal Medicine, University of Michigan, Ann Arbor, MI.

Chronic graft-versus-host disease (cGVHD) is a major complication of allogeneic hematopoietic cell transplantation (allo-HCT) and remains an area of unmet clinical need with few treatment options available. Notch blockade prevents acute GVHD in multiple mouse models, but the impact of Notch signaling on cGVHD remains unknown. Using genetic and antibody-mediated strategies of Notch inhibition, we investigated the role of Notch signaling in complementary mouse cGVHD models that mimic several aspects of human cGVHD in search of candidate therapeutics. In the B10.D2→BALB/c model of sclerodermatous cGVHD, Delta-like ligand 4 (Dll4)-driven Notch signaling was essential for disease development. Antibody-mediated Dll4 inhibition conferred maximum benefits when pursued early in a preventative fashion, with anti-Dll1 enhancing early protection. Notch-deficient alloantigen-specific T cells showed no early defects in proliferation or helper polarization in vivo but subsequently exhibited markedly decreased cytokine secretion and enhanced accumulation of FoxP3 regulatory T cells. In the B6→B10.BR major histocompatibility complex-mismatched model with multi-organ system cGVHD and prominent bronchiolitis obliterans (BO), but not skin manifestations, absence of Notch signaling in T cells provided long-lasting disease protection that was replicated by systemic targeting of Dll1, Dll4, or both Notch ligands, even during established disease. Notch inhibition decreased target organ damage and germinal center formation. Moreover, decreased BO-cGVHD was observed upon inactivation of and/or in T cells. Systemic targeting of Notch2 alone was safe and conferred therapeutic benefits. Altogether, Notch ligands and receptors regulate key pathogenic steps in cGVHD and emerge as novel druggable targets to prevent or treat different forms of cGVHD.
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http://dx.doi.org/10.1182/blood-2018-03-841155DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6238189PMC
November 2018

Stage-specific roles for Zmiz1 in Notch-dependent steps of early T-cell development.

Blood 2018 09 3;132(12):1279-1292. Epub 2018 Aug 3.

Division of Hematology-Oncology, Department of Internal Medicine, Medical School, University of Michigan, Ann Arbor, MI.

Notch1 signaling must elevate to high levels in order to drive the proliferation of CD4CD8 double-negative (DN) thymocytes and progression to the CD4CD8 double-positive (DP) stage through β-selection. During this critical phase of pre-T-cell development, which is also known as the DN-DP transition, it is unclear whether the Notch1 transcriptional complex strengthens its signal output as a discrete unit or through cofactors. We previously showed that the protein inhibitor of activated STAT-like coactivator Zmiz1 is a context-dependent cofactor of Notch1 in T-cell leukemia. We also showed that withdrawal of Zmiz1 generated an early T-lineage progenitor (ETP) defect. Here, we show that this early defect seems inconsistent with loss-of-Notch1 function. In contrast, at the later pre-T-cell stage, withdrawal of Zmiz1 impaired the DN-DP transition by inhibiting proliferation, like withdrawal of Notch. In pre-T cells, but not ETPs, Zmiz1 cooperatively regulated Notch1 target genes , , and Enforced expression of either activated Notch1 or Myc partially rescued the Zmiz1-deficient DN-DP defect. We identified residues in the tetratricopeptide repeat (TPR) domain of Zmiz1 that bind Notch1. Mutating only a single residue impaired the Zmiz1-Notch1 interaction, Myc induction, the DN-DP transition, and leukemic proliferation. Similar effects were seen using a dominant-negative TPR protein. Our studies identify stage-specific roles of Zmiz1. Zmiz1 is a context-specific cofactor for Notch1 during Notch/Myc-dependent thymocyte proliferation, whether normal or malignant. Finally, we highlight a vulnerability in leukemic cells that originated from a developmentally important Zmiz1-Notch1 interaction that is hijacked during transformation from normal pre-T cells.
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http://dx.doi.org/10.1182/blood-2018-02-835850DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6148450PMC
September 2018