Engineered SIRPα variants as immunotherapeutic adjuvants to anticancer antibodies

Cell rigidity and shape override CD47's "self"-signaling in phagocytosis by hyperactivating myosin-II

A macrophage engulfs another cell or foreign particle in an adhesive process that often activates myosin-II, unless the macrophage also engages "marker of self" CD47 that inhibits myosin. For many cell types, adhesion-induced activation of myosin-II is maximized by adhesion to a rigid rather than a flexible substrate. Here we demonstrate that rigidity of a phagocytosed cell also hyperactivates myosin-II, which locally overwhelms self-signaling at a phagocytic synapse. Cell stiffness is one among many factors including shape that changes in erythropoiesis, in senescence and in diseases ranging from inherited anemias and malaria to cancer. Controlled stiffening of normal human red blood cells (RBCs) in different shapes does not compromise CD47's interaction with the macrophage self-recognition receptor signal regulatory protein alpha (SIRPA). Uptake of antibody-opsonized RBCs is always fastest with rigid RBC discocytes, which also show that maximal active myosin-II at the synapse can dominate self-signaling by CD47. Rigid but rounded RBC stomatocytes signal self better than rigid RBC discocytes, highlighting the effects of shape on CD47 inhibition. Physical properties of phagocytic targets thus regulate self signaling, as is relevant to erythropoiesis, to clearance of rigid RBCs after blood storage, clearance of rigid pathological cells such as thalassemic or sickle cells, and even to interactions of soft/stiff cancer cells with macrophages.

Prognostic influence of macrophages in patients with diffuse large B-cell lymphoma: a correlative study from a Nordic phase II trial

The prognostic impact of the tumor microenvironment in diffuse large B-cell lymphoma has not been systematically assessed. We analyzed mRNA and antigen expression of monocytes, macrophages, lymphocytes, dendritic and natural killer cells in pretreatment tumor samples of patients with high-risk diffuse large B-cell lymphoma using gene expression microarray and immunohistochemistry. The patients were treated in a Nordic phase II study with dose-dense chemoimmunotherapy and central nervous system prophylaxis. Of the studied markers for non-malignant inflammatory cells, CD68 expression and CD68(+) macrophage counts correlated with favorable outcome. Five-year progression-free survival rates were 83% and 43% for the patients with high and low CD68 mRNA levels, respectively (P=0.007), while overall survival rates were 83% and 64%, respectively (P=ns). The patients with high CD68(+) macrophage counts had better 5-year progression-free survival (74% versus 40%; P=0.003) and overall survival (90% versus 60%; P=0.009) than the patients with low macrophage counts. Low CD68(+) macrophage count retained its prognostic impact on overall survival with age-adjusted International Prognostic Index [RR=5.0 (95% CI 1.024-19.088); P=0.017]. The findings were validated in three independent cohorts of patients treated with chemoimmunotherapy. In contrast, in patients treated with chemotherapy, high CD68(+) macrophage count was associated with poor progression-free survival (40% versus 72%; P=0.021) and overall survival (39% versus 72%; P=0.015). Together, the data suggest that macrophages exhibit a dual, treatment-specific role in diffuse large B-cell lymphoma. For the patients treated with chemoimmunotherapy, high pretreatment CD68 mRNA levels and CD68(+) macrophage numbers predict a favorable outcome.

Signal-regulatory protein α from the NOD mouse binds human CD47 with an exceptionally high affinity-- implications for engraftment of human cells

One common way to study human leucocytes and cancer cells in an experimental in vivo situation is to use mice that have been genetically engineered to lack an immune system and prevent human cell rejection. These mice lack CD132 and either RAG2 or the catalytic subunit of the DNA-dependent protein kinase, to make the mice deficient in lymphocytes and natural killer cells. The NOD mouse strain provides a better background for engraftment than other strains due to stronger engagement of the signal-regulatory protein-α (SIRPα) inhibitory receptor with human CD47 (hCD47) resulting in a ‘don't-eat-me’ signal. To determine the molecular parameters that determine this major functional effect in the NOD mouse we measured the affinity of hCD47 for SIRPα from various mouse strains. Human CD47 bound SIRPα from the NOD mouse with an affinity 65 times greater than SIRPα from other mouse strains. This is due mainly to the NOD SIRPα lacking two amino acids in domain 1 compared with other mouse strains. Remarkably the SIRPα(NOD) binds hCD47 with 10 times the affinity of the syngeneic hCD47/hSIRPα interaction. This affinity is outside the normal range for affinities for leucocyte surface protein interactions and raises questions as to what is the optimal affinity of this interaction for engraftment and what other xenogeneic interactions involved in homeostasis may also not be optimal.

Network features suggest new hepatocellular carcinoma treatment strategies

Background

Resistance to therapy remains a major cause of the failure of cancer treatment. A major challenge in cancer therapy is to design treatment strategies that circumvent the higher-level homeostatic functions of the robust cellular network that occurs in resistant cells. There is a lack of understanding of mechanisms responsible for the development of cancer and the basis of therapy-resistance mechanisms. Cellular signaling networks have an underlying architecture guided by universal principles. A robust system, such as cancer, has the fundamental ability to survive toxic anticancer drug treatments or a stressful environment mainly due to its mechanisms of redundancy. Consequently, inhibition of a single component/pathway would probably not constitute a successful cancer therapy.

Results

We developed a computational method to study the mechanisms of redundancy and to predict communications among the various pathways based on network theory, using data from gene expression profiles of hepatocellular carcinoma (HCC) of patients with poor and better prognosis cancers. Our results clearly indicate that immune system pathways tightly regulate most cancer pathways, and when those pathways are targeted by drugs, the network connectivity is dramatically changed. We examined the main HCC targeted treatments that are currently being evaluated in clinical trials. One prediction of our study is that Sorafenib combined with immune system treatments will be a more effective combination strategy than Sorafenib combined with any other targeted drugs.

Conclusions

We developed a computational framework to analyze gene expression data from HCC tumors with varying degrees of responsiveness and non-tumor samples, based on both Gene and Pathway Co-expression Networks. Our hypothesis is that redundancy is one of the major causes of drug resistance, and can be described as a function of the network structure and its properties. From this perspective, we believe that integration of the redundant variables could lead to the development of promising new methodologies to selectively identify and target the most significant resistance mechanisms of HCC. We describe three mechanisms of redundancy based on their levels of generalization and study the possible impact of those redundancy mechanisms on HCC treatments.

Plasminogen activator inhibitor-1 regulates infiltration of macrophages into melanoma via phosphorylation of FAK-Tyr⁹²⁵

Tumor-infiltrating macrophages are potential candidates for cancer immunotherapy. However, the detailed molecular mechanism underlying macrophage infiltration into tumors is poorly understood. Based on our previous finding that plasminogen activator inhibitor-1 (PAI-1) enhances vitronectin-dependent migration of macrophages, we investigated the potential role of PAI-1 in macrophage invasion into melanoma. Experimental evidence obtained from spheroid confrontation assay clearly showed that PAI-1 overexpression significantly enhanced the invasion of RAW 264.7 cells into B16F10 melanoma. We further demonstrated that PAI-1 induces phosphorylation of focal adhesion kinase (FAK) at Tyr(925), which, in turn, mediated the invasion of macrophages into the melanoma. This work further illustrates that low-density lipoprotein receptor related-protein 1 (LRP1) is essential for PAI-1-mediated FAK phosphorylation and macrophage invasion into melanoma. In conclusion, our study demonstrates a novel role of PAI-1 in macrophage invasion into melanoma and provides insights into the underlying molecular mechanism.

Considerations for combined immune checkpoint modulation and radiation treatment

Recent advances indicate that new therapeutic strategies for the treatment of malignancies will be realized from combined radiation treatment and immune checkpoint modulation. Numerous biophysical properties must be considered for effective biologic development, including affinity, selectivity, oligomeric state and valency. High-resolution structural characterization contributes to our understanding of these properties and can lead to the realization of proteins with unique in vitro activities and novel in vivo therapeutic functions. In this article we focus on the importance of these factors for new potential biologics and consider these in the context of combination therapies with physical modalities, including radiation therapy. In particular, we examine the consequences of altered avidities and subset-specific ligand density on the rational modification of biological function in the immunoglobulin and tumor necrosis factor superfamilies and for new optimized combination therapies.

Fibrogenesis and Carcinogenesis in Nonalcoholic Steatohepatitis (NASH): Involvement of Matrix Metalloproteinases (MMPs) and Tissue Inhibitors of Metalloproteinase (TIMPs)

Nonalcoholic steatohepatitis (NASH) is emerging worldwide because life-styles have changed to include much over-eating and less physical activity. The clinical and pathophysiological features of NASH are very different from those of HBV- and HCV-chronic liver diseases. The prognosis of NASH is worse among those with nonalcoholic fatty liver diseases (NAFLD), and some NASH patients show HCC with or without cirrhosis. In the present review we discuss fibrogenesis and the relationship between fibrosis and HCC occurrence in NASH to clarify the role of MMPs and TIMPs in both mechanisms. Previously we proposed MMP and TIMP expression in the multi-step occurrence of HCC from the literature based on viral-derived HCC. We introduce again these expressions during hepatocarcinogenesis and compare them to those in NASH-derived HCC, although the relationship with hepatic stem/progenitor cells (HPCs) invasion remains unknown. Signal transduction of MMPs and TIMPs is also discussed because it is valuable for the prevention and treatment of NASH and NASH-derived HCC.

Targeting tumor-associated macrophages with anti-CSF-1R antibody reveals a strategy for cancer therapy

Macrophage infiltration has been identified as an independent poor prognostic factor in several cancer types. The major survival factor for these macrophages is macrophage colony-stimulating factor 1 (CSF-1). We generated a monoclonal antibody (RG7155) that inhibits CSF-1 receptor (CSF-1R) activation. In vitro RG7155 treatment results in cell death of CSF-1-differentiated macrophages. In animal models, CSF-1R inhibition strongly reduces F4/80(+) tumor-associated macrophages accompanied by an increase of the CD8(+)/CD4(+) T cell ratio. Administration of RG7155 to patients led to striking reductions of CSF-1R(+)CD163(+) macrophages in tumor tissues, which translated into clinical objective responses in diffuse-type giant cell tumor (Dt-GCT) patients.

Extracellular architecture of the SYG-1/SYG-2 adhesion complex instructs synaptogenesis

SYG-1 and SYG-2 are multipurpose cell adhesion molecules (CAMs) that have evolved across all major animal taxa to participate in diverse physiological functions, ranging from synapse formation to formation of the kidney filtration barrier. In the crystal structures of several SYG-1 and SYG-2 orthologs and their complexes, we find that SYG-1 orthologs homodimerize through a common, bispecific interface that similarly mediates an unusual orthogonal docking geometry in the heterophilic SYG-1/SYG-2 complex. C. elegans SYG-1's specification of proper synapse formation in vivo closely correlates with the heterophilic complex affinity, which appears to be tuned for optimal function. Furthermore, replacement of the interacting domains of SYG-1 and SYG-2 with those from CAM complexes that assume alternative docking geometries or the introduction of segmental flexibility compromised synaptic function. These results suggest that SYG extracellular complexes do not simply act as "molecular velcro" and that their distinct structural features are important in instructing synaptogenesis. PAPERFLICK:

New insights into cancer immunoediting and its three component phases--elimination, equilibrium and escape

The principles of cancer immunoediting have set the foundations for understanding the dual host-protective and tumour sculpting actions of immunity on cancer and establishing the basis for novel individualized cancer immunotherapies. During cancer immunoediting, the host immune system shapes tumour fate in three phases through the activation of innate and adaptive immune mechanisms. In the first phase, Elimination, transformed cells are destroyed by a competent immune system. Sporadic tumour cells that manage to survive immune destruction may then enter an Equilibrium phase where editing occurs. The Escape phase represents the third and final phase of the process, where immunologically sculpted tumours begin to grow progressively, become clinically apparent and establish an immunosuppressive tumour microenvironment. This review focuses on important recent developments that have enhanced our understanding of each phase of the cancer immunoediting process, summarizes the discovery of new predictive and prognostic biomarkers and discusses development of novel and objectively effective cancer immunotherapies.

The CD47-SIRPα signalling system: its physiological roles and therapeutic application

Signal regulatory protein α (SIRPα), also known as SHPS-1/BIT/ CD172a, is an immunoglobulin superfamily protein that binds to the protein tyrosine phosphatases SHP-1 and SHP-2 through its cytoplasmic region. CD47, another immunoglobulin superfamily protein, is a ligand for SIRPα, with the two proteins constituting a cell-cell communication system (the CD47-SIRPα signalling system). SIRPα is particularly abundant in the myeloid-lineage hematopoietic cells such as macrophages or dendritic cells (DCs), whereas CD47 is expressed ubiquitously. Interaction of CD47 (on red blood cells) with SIRPα (on macrophages) is thought to prevent the phagocytosis by the latter cells of the former cells, determining the lifespan of red blood cells. Recent studies further indicate that this signalling system plays important roles in engraftment of hematopoietic stem cells as well as in tumour immune surveillance through regulation of the phagocytic activity of macrophages. In the immune system, the CD47-SIRPα interaction is also important for the development of a subset of CD11c(+)DCs as well as organization of secondary lymphoid organs. Finally, the CD47-SIRPα signalling system likely regulates bone homeostasis by osteoclast development. Newly emerged functions of the CD47-SIRPα signalling system thus provide multiple therapeutic strategies for cancer, autoimmune diseases and bone disorders.

Cyclin-dependent kinase inhibitor 2B regulates efferocytosis and atherosclerosis

Genetic variation at the chromosome 9p21 risk locus promotes cardiovascular disease; however, it is unclear how or which proteins encoded at this locus contribute to disease. We have previously demonstrated that loss of one candidate gene at this locus, cyclin-dependent kinase inhibitor 2B (Cdkn2b), in mice promotes vascular SMC apoptosis and aneurysm progression. Here, we investigated the role of Cdnk2b in atherogenesis and found that in a mouse model of atherosclerosis, deletion of Cdnk2b promoted advanced development of atherosclerotic plaques composed of large necrotic cores. Furthermore, human carriers of the 9p21 risk allele had reduced expression of CDKN2B in atherosclerotic plaques, which was associated with impaired expression of calreticulin, a ligand required for activation of engulfment receptors on phagocytic cells. As a result of decreased calreticulin, CDKN2B-deficient apoptotic bodies were resistant to efferocytosis and not efficiently cleared by neighboring macrophages. These uncleared SMCs elicited a series of proatherogenic juxtacrine responses associated with increased foam cell formation and inflammatory cytokine elaboration. The addition of exogenous calreticulin reversed defects associated with loss of Cdkn2b and normalized engulfment of Cdkn2b-deficient cells. Together, these data suggest that loss of CDKN2B promotes atherosclerosis by increasing the size and complexity of the lipid-laden necrotic core through impaired efferocytosis.

The role of dendritic cells in graft-versus-tumor effect

Dendritic cells (DCs) are the most potent antigen presenting cells. DCs play a pivotal role in determining the character and magnitude of immune responses to tumors. Host and donor hematopoietic-derived DCs play a critical role in the development of graft-versus-host disease (GVHD) following allogeneic hematopoietic cell transplantation. GVHD is tightly linked with the graft-versus-tumor (GVT) effect. Although both host and donor DCs are important regulators of GVHD, the role of DCs in GVT is poorly understood. GVT is caused by donor T cells that attack recipient tumor cells. The donor T cells recognize alloantigens, and tumor specific antigens (TSAs) are mediating GVHD. The process of presentation of these antigens, especially TSAs remains unknown. Recent data suggested that DC may be essential role for inducing GVT. The mechanisms that DCs possess may include direct presentation, cross-presentation, cross-dressing. The role they play in GVT will be reviewed.

New insights into cancer immunoediting and its three component phases--elimination, equilibrium and escape

The principles of cancer immunoediting have set the foundations for understanding the dual host-protective and tumour sculpting actions of immunity on cancer and establishing the basis for novel individualized cancer immunotherapies. During cancer immunoediting, the host immune system shapes tumour fate in three phases through the activation of innate and adaptive immune mechanisms. In the first phase, Elimination, transformed cells are destroyed by a competent immune system. Sporadic tumour cells that manage to survive immune destruction may then enter an Equilibrium phase where editing occurs. The Escape phase represents the third and final phase of the process, where immunologically sculpted tumours begin to grow progressively, become clinically apparent and establish an immunosuppressive tumour microenvironment. This review focuses on important recent developments that have enhanced our understanding of each phase of the cancer immunoediting process, summarizes the discovery of new predictive and prognostic biomarkers and discusses development of novel and objectively effective cancer immunotherapies.

Cyclin-dependent kinase inhibitor 2B regulates efferocytosis and atherosclerosis

Genetic variation at the chromosome 9p21 risk locus promotes cardiovascular disease; however, it is unclear how or which proteins encoded at this locus contribute to disease. We have previously demonstrated that loss of one candidate gene at this locus, cyclin-dependent kinase inhibitor 2B (Cdkn2b), in mice promotes vascular SMC apoptosis and aneurysm progression. Here, we investigated the role of Cdnk2b in atherogenesis and found that in a mouse model of atherosclerosis, deletion of Cdnk2b promoted advanced development of atherosclerotic plaques composed of large necrotic cores. Furthermore, human carriers of the 9p21 risk allele had reduced expression of CDKN2B in atherosclerotic plaques, which was associated with impaired expression of calreticulin, a ligand required for activation of engulfment receptors on phagocytic cells. As a result of decreased calreticulin, CDKN2B-deficient apoptotic bodies were resistant to efferocytosis and not efficiently cleared by neighboring macrophages. These uncleared SMCs elicited a series of proatherogenic juxtacrine responses associated with increased foam cell formation and inflammatory cytokine elaboration. The addition of exogenous calreticulin reversed defects associated with loss of Cdkn2b and normalized engulfment of Cdkn2b-deficient cells. Together, these data suggest that loss of CDKN2B promotes atherosclerosis by increasing the size and complexity of the lipid-laden necrotic core through impaired efferocytosis.

Hypericin-based Photodynamic Therapy Induces a Tumor-Specific Immune Response and an Effective DC-based cancer Immunotherapy

In our study, we find that photodynamic therapy (PDT), which generates reactive oxygen species (ROS) -mediated endoplasmic reticulum (ER) stress to inflict trauma in the targeted lesion, can break the balance between membrane damage-associated molecular patterns (DAMPs) and integrin-associated protein (CD47). The imbalance undermines the ability of lewis lung carcinoma (LLC) cells to escape immune attack by increasing the uptake of hypericin-mediated PDT(hyp-PDT) killed lewis lung carcinoma (LLC) cells by homologous dendritic cells (DCs), accompanied by phenotypic maturation (CD80high, CD86high, and CD40high) and functional stimulation (NOhigh, IL-10absent) of dendritic cells as well as subsequent T-cell response. Besides, C57BL/6 mice vaccinated with dendritic cells (DCs) pulsed with PDT-treated LLCs (PDT-DCs) or PDT-treated LLCs alone (PDT-LLCs) show potent immunity against LLC tumor. These data identify hypericin-induced PDT as a strong inducer of immunogenic apoptosis, providing an antitumor vaccination strategy for personalized cancer Immunotherapy.

Apoptotic cell clearance: basic biology and therapeutic potential

The prompt removal of apoptotic cells by phagocytes is important for maintaining tissue homeostasis. The molecular and cellular events that underpin apoptotic cell recognition and uptake, and the subsequent biological responses, are increasingly better defined. The detection and disposal of apoptotic cells generally promote an anti-inflammatory response at the tissue level, as well as immunological tolerance. Consequently, defects in apoptotic cell clearance have been linked with various inflammatory diseases and autoimmunity. Conversely, under certain conditions, such as the killing of tumour cells by specific cell-death inducers, the recognition of apoptotic tumour cells can promote an immunogenic response and antitumour immunity. Here, we review the current understanding of the complex process of apoptotic cell clearance in physiology and pathology, and discuss how this knowledge could be harnessed for new therapeutic strategies.

Tumor metastasis: moving new biological insights into the clinic

As the culprit behind most cancer-related deaths, metastasis is the ultimate challenge in our effort to fight cancer as a life-threatening disease. The explosive growth of metastasis research in the past decade has yielded an unprecedented wealth of information about the tumor-intrinsic and tumor-extrinsic mechanisms that dictate metastatic behaviors, the molecular and cellular basis underlying the distinct courses of metastatic progression in different cancers and what renders metastatic cancer refractory to available therapies. However, integration of such new knowledge into an improved, metastasis-oriented oncological drug development strategy is needed to thwart the development of metastatic disease at every stage of progression.

Polymeric nanotherapeutics: clinical development and advances in stealth functionalization strategies

Long-circulating polymeric nanotherapeutics have garnered increasing interest in research and in the clinic owing to their ability to improve the solubility and pharmacokinetics of therapeutic cargoes. Modulation of carrier properties promises more effective drug localization at the disease sites and can lead to enhanced drug safety and efficacy. In the present review, we highlight the current development of polymeric nanotherapeutics in the clinic. In light of the importance of stealth properties in therapeutic nanoparticles, we also review the advances in stealth functionalization strategies and examine the performance of different stealth polymers in the literature. In addition, we discuss the recent development of biologically inspired "self" nanoparticles, which present a differing stealth concept from conventional approaches.

Harnessing the antitumor potential of macrophages for cancer immunotherapy

Macrophages constitute a dominant fraction of the population of immune cells that infiltrate developing tumors. Recruited by tumor-derived signals, tumor-infiltrating macrophages are key orchestrators of a microenvironment that supports tumor progression. However, the phenotype of macrophages is pliable and, if instructed properly, macrophages can mediate robust antitumor functions through their ability to eliminate malignant cells, inhibit angiogenesis, and deplete fibrosis. While much effort has focused on strategies to block the tumor-supporting activity of macrophages, emerging approaches designed to instruct macrophages with antitumor properties are demonstrating promise and may offer a novel strategy for cancer immunotherapy.

Improving macrophage responses to therapeutic antibodies by molecular engineering of SIRPα variants

CD47 transduces inhibitory signals through signal-regulatory protein α (SIRPα), a plasma membrane receptor expressed by macrophages. Many cancers upregulate CD47 to evade immunosurveillance. We have recently engineered SIRPα variants that potently antagonize CD47 for use as anticancer immunotherapeutics. These high-affinity SIRPα variants synergize with antineoplastic antibodies by lowering the threshold for macrophage-mediated destruction of malignant cells.