Project description:CD47 is a ubiquitous cell surface receptor that limits cell clearance by phagocytes that express its counter-receptor signal-regulatory protein-α and directly regulates T cell immunity by interacting with its inhibitory ligand thrombospondin-1. Murine natural killer (NK) cells express higher levels of CD47 than other lymphocytes, but the role of CD47 in regulating NK cell homeostasis and immune function remains unclear. Cd47-/- mice exhibited depletion of NK precursors in bone marrow, but antisense Cd47 knockdown or gene disruption resulted in a dose dependent accumulation of immature and mature NK cells in spleen. Cd47-/- mice were impaired in controlling chronic Clone-13 lymphocytic choriomeningitis virus (LCMV) infection, which was associated with depletion of splenic NK cells and loss of effector cytokine and interferon response gene expression in Cd47-/- NK cells. These data identify CD47 as a cell-intrinsic and systemic regulator of NK cell homeostasis and NK cell responses to viral infection.
Project description:CD47 is a transmembrane glycoprotein that is ubiquitously expressed in different organs and tissues (Barclay and Van den Berg 2014; Liu, et al. 2017). In the human immune system, CD47 interacts with some integrins, two counter-receptor signal regulator protein (SIRP) family members, and the secreted thrombospondin-1 (TSP1) (Barclay and Van den Berg 2014; Gao, et al. 2016; Kaur, et al. 2013; Oldenborg, et al. 2000). CD47 has two established roles in the immune system. The CD47-SIRPα interaction was identified as a critical innate immune checkpoint, which delivers an antiphagocytic signal to macrophages and inhibits neutrophil cytotoxicity (Martínez- Sanz, et al. 2021). Its interaction with inhibitory SIRPα is a physiological anti-phagocytic “don’t eat me” signal on circulating red blood cells that is co-opted by cancer cells (Matlung, et al. 2017). Many malignant cells overexpress CD47 (Betancur, et al. 2017; Chao, et al. 2011; Jaiswal, et al. 2009; Majeti, et al. 2009; Oronsky, et al. 2020; Petrova, et al. 2017). CD47/SIRPα-targeted therapeutics have been developed to overcome this immune checkpoint for cancer treatment (Kaur, et al. 2020; Matlung, et al. 2017). Secondly, engagement of CD47 on T cells by TSP1 regulates their differentiation and survival (Grimbert, et al. 2006; Lamy, et al. 2007) and inhibits T cell receptor signaling and antigen presentation by dendritic cells (DCs) (Kaur, et al. 2014; Li, et al. 2002; Liu, et al. 2015; Miller, et al. 2013; Soto-Pantoja, et al. 2014; Weng, et al. 2014). TSP1/CD47 signaling has similar inhibitory functions to limit NK cell activation (Kim, et al. 2008; Nath, et al. 2018; Nath, et al. 2019; Schwartz, et al. 2019) and IL1β production by macrophages (Stein, et al. 2016). CD47 is therefore a checkpoint that regulates both innate and adaptive immunity. The recent understanding of CD47 antagonism associated with increased antigen presentation by DCs (Liu, et al. 2016) and natural killer cell cytotoxicity (Nath, et al. 2019) contributes to the heightened interest in CD47 as a therapeutic target (Kaur, et al. 2020).
Project description:Elevated CD47 expression in some cancers is associated with decreased survival and limits phagocytic clearance by engaging its counter-receptor SIRPα, but elevated CD47 mRNA expression in human melanomas is associated with improved survival. Gene expression data suggested that recruitment of natural killer (NK) cells, which highly express CD47, into the tumor microenvironment contribute to this correlation. The CD47 ligand thrombospondin-1 inhibited wildtype but not Cd47-/- murine NK cell proliferation and granzyme B and interferon-γ expression in vitro. Cd47-/- NK cells correspondingly showed augmented effector phenotypes. Although, wildtype and Cd47-/- NK cells were equally effective for killing B16 melanoma cells in vitro, Cd47-/- mice exhibited enhanced B16 tumor growth in vivo. Consistent with the human data, tumor-bearing Cd47-/- mice had decreased splenic NK numbers with impaired effector protein expression and elevated exhaustion markers. A pro-apoptotic signature in Cd47-/- NK cells was associated with stress-mediated elevation of mitochondrial proton leak, increased reactive oxygen species and apoptosis. Gene expression profiling identified CD47-dependent transcriptional responses in in NK cells from tumor-bearing mice that regulate systemic NK activation and exhaustion. Treating wildtype mice with a CD47 antibody that blocks thrombospondin-1 binding delayed tumor growth and was associated with increased NK recruitment and increased granzyme B- and interferon-γ levels in intratumoral NK but not CD8+ T cells. Therefore, CD47 in the tumor microenvironment regulates NK-mediated tumor immunity, and therapeutic blockade enhances NK immune function.
Project description:Elevated expression of CD47 in some cancers is associated with poor survival, related to its function as an innate immune checkpoint when expressed on tumors cells. In contrast, elevated CD47 ex-pression in cutaneous melanomas is associated with improved survival. Previous studies impli-cated protective functions of CD47 expressed by immune cells in the melanoma tumor microen-vironment. RNA sequencing analysis of responses induced by CD3 and CD28 engagement on wild type and CD47-deficient Jurkat T lymphoblast cells identified additional regulators of T cell func-tion that were also CD47-dependent in mouse CD8 T cells. MYCN mRNA expression was up-regulated in CD47-deficient cells but down-regulated in CD47-deficient cells following activa-tion. CD47 also regulated alternative splicing that produces two N-MYC isoforms. The CD47 ligand thrombospondin-1 inhibited expression of these MYCN mRNA isoforms as well as induction of the oncogenic decoy MYCN opposite strand (MYCNOS) noncoding RNA during T cell activation. Analysis of mRNA expression data for melanomas in The Cancer Genome Atlas identified signif-icant coexpression of MYCN with CD47 and known regulators of CD8 T cell function. Throm-bospondin-1 inhibited the induction of TIGIT, CD40LG and MCL1 mRNAs following T cell acti-vation in vitro. Increased mRNA expression of these T cell transcripts and of MYCN in melanomas was associated with improved overall survival.
Project description:High levels of ecto-5'-nucleotidase (CD73) have been implicated in immune suppression and tumor progression. Elevated levels of CD73 has also been observed in patients who progress on anti–PD-1 immunotherapy. While regulatory T cells can express CD73 and inhibit T cell responses via the production of adenosine, less is known if conventional T cells and natural killer (NK) cells can express CD73. We found that the expression of CD73 is restricted to tumor-infiltrating NK cells and the frequency of these cells correlate with larger tumor size in patients with breast cancer. In addition, the expression of other immune checkpoint receptors including LAG-3 and VISTA was significantly higher in CD73 positive NK cells than on CD73 negative NK cells. Furthermore, the prognostic value of CD73 gene expression was influenced by NK cell signature expressed in patients with breast cancer and sarcoma. Mechanistically, upon engagement of 4-1BBL on tumor cells, NK cells transport CD73 in intracellular vesicles to the cell surface and extracellular space via actin polymerization-dependent exocytosis. These CD73 positive NK cells undergo transcriptional reprogramming and upregulate IL10 production via STAT3 transcriptional activity and suppress CD4 T cell activity. Altogether, our results support that tumors can hijack NK cells as a means to escape immunity and that CD73 expression defines an inducible population of NK cells with immune regulatory properties within the tumor microenvironment.
Project description:A novel affinity-tuned dual-checkpoint bispecific antibody with potent PD-L1 and moderate CD47 affinity was designed to improve the selectivity to TME and thus enhance antitumor immunity and efficacy. The scRNAseq analysis was performed to examine the immune cell modulation in TME following the CD47/PD-L1 bispecific treatment.
Project description:A novel affinity-tuned dual-checkpoint bispecific antibody with potent PD-L1 and moderate CD47 affinity was designed to improve the selectivity to TME and thus enhance antitumor immunity and efficacy. The gene expression analysis using Nanostring platform was performed to examine the immune cell modulation in TME following the CD47/PD-L1 bispecific treatment.