Blockade of CD47 increases survival of mice exposed to lethal total body irradiation

CD47 in the tumor microenvironment limits cooperation between antitumor T-cell immunity and radiotherapy

Although significant advances in radiotherapy have increased its effectiveness in many cancer settings, general strategies to widen the therapeutic window between normal tissue toxicity and malignant tumor destruction would still offer great value. CD47 blockade has been found to confer radioprotection to normal tissues while enhancing tumor radiosensitivity. Here, we report that CD47 blockade directly enhances tumor immunosurveillance by CD8(+) T cells. Combining CD47 blockade with irradiation did not affect fibrosarcoma growth in T cell-deficient mice, whereas adoptive transfer of tumor-specific CD8(+) T cells restored combinatorial efficacy. Furthermore, ablation of CD8(+) T cells abolished radiotherapeutic response in immunocompetent syngeneic hosts. CD47 blockade in either target cells or effector cells was sufficient to enhance antigen-dependent CD8(+) CTL-mediated tumor cell killing in vitro. In CD47-deficient syngeneic hosts, engrafted B16 melanomas were 50% more sensitive to irradiation, establishing that CD47 expression in the microenvironment was sufficient to limit tumor radiosensitivity. Mechanistic investigations revealed increased tumor infiltration by cytotoxic CD8(+) T cells in a CD47-deficient microenvironment, with an associated increase in T cell-dependent intratumoral expression of granzyme B. Correspondingly, an inverse correlation between CD8(+) T-cell infiltration and CD47 expression was observed in human melanomas. Our findings establish that blocking CD47 in the context of radiotherapy enhances antitumor immunity by directly stimulating CD8(+) cytotoxic T cells, with the potential to increase curative responses.

Thrombospondin-1 and CD47 signaling regulate healing of thermal injury in mice

More than 2.5 million Americans suffer from burn injuries annually, and burn management is a major public health problem. Treatments have been developed to manage wound injuries employing skin grafts, various dressings and topical and systemic agents. However, these often achieve limited degrees of success. We previously reported that targeting the interaction of thrombospondin-1 with its signaling receptor CD47 or deletion of the genes encoding either of these proteins in mice improves recovery from soft tissue ischemic injuries as well as tissue injuries caused by ionizing radiation. We now demonstrate that the absence of CD47 improves the rate of wound closure for a focal dermal second-degree thermal injury, whereas lack of thrombospondin-1 initially delays wound closure compared to healing in wild type mice. Doppler analysis of the wounded area showed increased blood flow in both CD47 and thrombospondin-1 null mice. Accelerated wound closure in the CD47 null mice was associated with increased fibrosis as demonstrated by a 4-fold increase in collagen fraction. Wound tissue of CD47 null mice showed increased thrombospondin-1 mRNA and protein expression and TGF-β1 mRNA levels. Activation of latent TGF-β1 was increased in thermally injured CD47-null tissue as assessed by phosphorylation of the TGF-β1 receptor-regulated transcription factors SMAD-2 and -3. Overall these results indicate that targeting CD47 may improve the speed of healing thermal injuries, but some level of CD47 expression may be required to limit the long term TGF-β1-dependent fibrosis of these wounds.

Cardiac CD47 drives left ventricular heart failure through Ca2+-CaMKII-regulated induction of HDAC3

Background

Left ventricular heart failure (LVHF) remains progressive and fatal and is a formidable health problem because ever‐larger numbers of people are diagnosed with this disease. Therapeutics, while relieving symptoms and extending life in some cases, cannot resolve this process and transplant remains the option of last resort for many. Our team has described a widely expressed cell surface receptor (CD47) that is activated by its high‐affinity secreted ligand, thrombospondin 1 (TSP1), in acute injury and chronic disease; however, a role for activated CD47 in LVHF has not previously been proposed.

Methods and Results

In experimental LVHF TSP1‐CD47 signaling is increased concurrent with up‐regulation of cardiac histone deacetylase 3 (HDAC3). Mice mutated to lack CD47 displayed protection from transverse aortic constriction (TAC)‐driven LVHF with enhanced cardiac function, decreased cellular hypertrophy and fibrosis, decreased maladaptive autophagy, and decreased expression of HDAC3. In cell culture, treatment of cardiac myocyte CD47 with a TSP1‐derived peptide, which binds and activates CD47, increased HDAC3 expression and myocyte hypertrophy in a Ca²⁺/calmodulin protein kinase II (CaMKII)‐dependent manner. Conversely, antibody blocking of CD47 activation, or pharmacologic inhibition of CaMKII, suppressed HDAC3 expression, decreased myocyte hypertrophy, and mitigated established LVHF. Downstream gene suppression of HDAC3 mimicked the protective effects of CD47 blockade and decreased hypertrophy in myocytes and mitigated LVHF in animals.

Conclusions

These data identify a proximate role for the TSP1‐CD47 axis in promoting LVHF by CaKMII‐mediated up‐regulation of HDAC3 and suggest novel therapeutic opportunities.

Plasmonics in Dirac systems: from graphene to topological insulators

Recent developments in the emerging field of plasmonics in graphene and other Dirac systems are reviewed and a comprehensive introduction to the standard models and techniques is given. In particular, we discuss intrinsic plasmon excitation of single and bilayer graphene via hydrodynamic equations and the random phase approximation, but also comment on double and multilayer structures. Additionally, we address Dirac systems in the retardation limit and also with large spin–orbit coupling including topological insulators. Finally, we summarize basic properties of the charge, current and photon linear response functions in an appendix.

Thrombospondin-1 signaling through CD47 inhibits self-renewal by regulating c-Myc and other stem cell transcription factors

Signaling through the thrombospondin-1 receptor CD47 broadly limits cell and tissue survival of stress, but the molecular mechanisms are incompletely understood. We now show that loss of CD47 permits sustained proliferation of primary murine endothelial cells, increases asymmetric division, and enables these cells to spontaneously reprogram to form multipotent embryoid body-like clusters. c-Myc, Klf4, Oct4, and Sox2 expression is elevated in CD47-null endothelial cells, in several tissues of CD47- and thrombospondin-1-null mice, and in a human T cell line lacking CD47. CD47 knockdown acutely increases mRNA levels of c-Myc and other stem cell transcription factors in cells and in vivo, whereas CD47 ligation by thrombospondin-1 suppresses c-Myc expression. The inhibitory effects of increasing CD47 levels can be overcome by maintaining c-Myc expression and are absent in cells with dysregulated c-Myc. Thus, CD47 antagonists enable cell self-renewal and reprogramming by overcoming negative regulation of c-Myc and other stem cell transcription factors.

Thrombospondin-1 in urological cancer: pathological role, clinical significance, and therapeutic prospects

Angiogenesis is an important process for tumor growth and progression of various solid tumors including urological cancers. Thrombospondins (TSPs), especially TSP-1, are representative “anti”-angiogenic molecules and many studies have clarified their pathological role and clinical significance in vivo and in vitro. In fact, TSP-1 expression is associated with clinicopathological features and prognosis in many types of cancers. However, TSP-1 is a multi-functional protein and its biological activities vary according to the specific tumor environments. Consequently, there is no general agreement on its cancer-related function in urological cancers, and detailed information regarding regulative mechanisms is essential for a better understanding of its therapeutic effects and prognostic values. Various “suppressor genes” and “oncogenes” are known to be regulators and TSP-1-related factors under physiological and pathological conditions. In addition, various types of fragments derived from TSP-1 exist in a given tissue microenvironment and TSP-1 derived-peptides have specific activities. However, a detailed pathological function in human cancer tissues is not still understood. This review will focus on the pathological roles and clinical significance of TSP-1 in urological cancers, including prostate cancer, renal cell carcinoma, and urothelial cancer. In addition, special attention is paid to TSP-1-derived peptide and TSP-1-based therapy for malignancies.