Imaging and photodynamic therapy of prostate cancer using a theranostic PSMA-targeting ligand.

PURPOSE: Incomplete resection of prostate cancer (PCa) results in increased risk of disease recurrence. Combined fluorescence-guided surgery with tumor-targeted photodynamic therapy (tPDT) may help to achieve complete tumor eradication. We developed a prostate-specific membrane antigen (PSMA) ligand consisting of a DOTA chelator for 111In labeling and a fluorophore/photosensitizer IRDye700DX (PSMA-N064). We evaluated the efficacy of PSMA-tPDT using PSMA-N064 in cell viability assays, a mouse xenograft model and in an ex vivo incubation study on fresh human PCa tissue. METHODS: In vitro, therapeutic efficacy of PSMA-N064 was evaluated using PSMA-positive LS174T cells and LS174T wild-type cells. In vivo, PSMA-N064-mediated tPDT was tested in immunodeficient BALB/c mice-bearing PSMA-positive LS174T xenografts. Tumor growth and survival were compared to control mice that received either NIR light or ligand injection only. Ex vivo tPDT efficacy was evaluated in excised fresh human PCa tissue incubated with PSMA-N064. RESULTS: In vitro, tPDT led to a PSMA-specific light- and ligand dose-dependent loss in cell viability. In vivo, tPDT-induced tumor cell apoptosis, delayed tumor growth, and significantly improved survival (p = 0.004) of the treated PSMA-positive tumor-bearing mice compared with the controls. In fresh ex vivo human PCa tissue, apoptosis was significantly increased in PSMA-tPDT-treated samples compared to non-treated control samples (p = 0.037). CONCLUSION: This study showed the feasibility of PSMA-N064-mediated tPDT in cell assays, a xenograft model and excised fresh human PCa tissue. This paves the way to investigate the impact of in vivo PSMA-tPDT on surgical outcome in PCa patients.

Fibroblast Activation Protein-Targeted Photodynamic Therapy of Cancer-Associated Fibroblasts in Murine Models for Pancreatic Ductal Adenocarcinoma.

Patients with pancreatic ductal adenocarcinoma (PDAC) have a dismal 5 year survival of 9%. One important limiting factor for treatment efficacy is the dense tumor-supporting stroma. The cancer-associated fibroblasts in this stroma deposit excessive amounts of extracellular matrix components and anti-inflammatory mediators, which hampers the efficacy of chemo- and immunotherapies. Systemic depletion of all activated fibroblasts is, however, not feasible nor desirable and therefore a local approach should be pursued. Here, we provide a proof-of-principle of using fibroblast activation protein (FAP)-targeted photodynamic therapy (tPDT) to treat PDAC. FAP-targeting antibody 28H1 and irrelevant control antibody DP47GS were conjugated to the photosensitizer IRDye700DX (700DX) and the chelator diethylenetriaminepentaacetic acid. In vitro binding and cytotoxicity were evaluated using the fibroblast cell-line NIH-3T3 stably transfected with FAP. Biodistribution of 111In-labeled antibody-700DX constructs was determined in mice carrying syngeneic tumors of the murine PDAC cell line PDAC299, and in a genetically engineered PDAC mouse model (CKP). Then, tPDT was performed by exposing the subcutaneous or the spontaneous PDAC tumors to 690 nm light. Induction of apoptosis after treatment was assessed using automated analyses of immunohistochemistry for cleaved caspase-3. 28H1-700DX effectively bound to 3T3-FAP cells and induced cytotoxicity upon exposure to 690 nm light, whereas no binding or cytotoxic effects were observed for DP47GS-700DX. Although both 28H1-700DX and DP47GS-700DX accumulated in subcutaneous PDAC299 tumors, autoradiography demonstrated that only 28H1-700DX reached the tumor core. On the contrary, control antibody DP47GS-700DX was only present at the tumor rim. In CKP mice, both antibodies accumulated in the tumor, but tumor-to-blood ratios of 28H1-700DX were higher than that of the control. Notably, in vivo FAP-tPDT caused upregulation of cleaved caspase-3 staining in both subcutaneous and in spontaneous tumors. In conclusion, we have shown that tPDT is a feasible approach for local depletion of FAP-expressing stromal cells in murine models for PDAC.

Diet-induced obesity in mice diminishes hematopoietic stem and progenitor cells in the bone marrow.

Obesity is associated with chronic low-grade inflammation, characterized by leukocytosis and inflammation in the adipose tissue. Continuous activation of the immune system is a stressor for hematopoietic stem and progenitor cells (HSPCs) in the bone marrow (BM). Here we studied how diet-induced obesity (DIO) affects HSPC population dynamics in the BM. Eight groups of age-matched C57Bl/6 mice received a high-fat diet (45% kilocalories from fat) ranging from 1 d up to 18 wk. The obesogenic diet caused decreased proliferation of lineage(-)Sca-1(+)c-Kit(+) (LSK) cells in the BM and a general suppression of progenitor cell populations including common lymphoid progenitors and common myeloid progenitors. Within the LSK population, DIO induced a shift in stem cells that are capable of self-renewal toward maturing multipotent progenitor cells. The higher differentiation potential resulted in increased lymphoid and myeloid ex vivo colony-forming capacity. In a competitive BM transplantation, BM from obese animals showed impaired multilineage reconstitution when transplanted into chow-fed mice. Our data demonstrate that obesity stimulates the differentiation and reduces proliferation of HSPCs in the BM, leading to a decreased HSPC population. This implies that the effects of obesity on HSPCs hampers proper functioning of the immune system.-Van den Berg, S. M., Seijkens, T. T. P., Kusters, P. J. H., Beckers, L., den Toom, M., Smeets, E., Levels, J., de Winther, M. P. J., Lutgens, E. Diet-induced obesity in mice diminishes hematopoietic stem and progenitor cells in the bone marrow.

Constitutive GITR Activation Reduces Atherosclerosis by Promoting Regulatory CD4+ T-Cell Responses-Brief Report.

OBJECTIVE: Glucocorticoid-induced tumor necrosis factor receptor family-related protein (GITR) is expressed on CD4(+) effector memory T cells and regulatory T cells; however, its role on these functionally opposing cell types in atherosclerosis is not fully understood. APPROACH AND RESULTS: Low-density lipoprotein receptor-deficient mice (Ldlr(-/-)) were lethally irradiated and reconstituted with either bone marrow from B-cell-restricted Gitrl transgenic mice or from wild-type controls and fed a high-cholesterol diet for 11 weeks. Chimeric Ldlr(-/-) Gitrl(tg) mice showed a profound increase in both CD4(+) effector memory T cells and regulatory T cells in secondary lymphoid organs. Additionally, the number of regulatory T cells was significantly enhanced in the thymus and aorta of these mice along with increased Gitrl and Il-2 transcript levels. Atherosclerotic lesions of Ldlr(-/-) Gitrl(tg) chimeras contained more total CD3(+) T cells as well as Foxp3(+) regulatory T cells overall, leading to significantly less severe atherosclerosis. CONCLUSIONS: These data indicate that continuous GITR stimulation through B cell Gitrl acts protective in a mouse model of atherosclerosis by regulating the balance between regulatory and effector memory CD4(+) T cells.

Hypercholesterolemia-induced priming of hematopoietic stem and progenitor cells aggravates atherosclerosis.

Modulation of hematopoietic stem and progenitor cells (HSPCs) determines immune cell function. In this study, we investigated how hypercholesterolemia affects HSPC biology and atherosclerosis. Hypercholesterolemia induced loss of HSPC quiescence, characterized by increased proliferation and expression of cyclin B1, C1, and D1, and a decreased expression of Rb, resulting in a 3.6- fold increase in the number of HSPCs in hypercholesterolemic Ldlr(-/-) mice. Competitive bone marrow (BM) transplantations showed that a hypercholesterolemic BM microenvironment activates HSPCs and skews their development toward myeloid lineages. Conversely, hypercholesterolemia-primed HSPCs acquired an enhanced propensity to generate myeloid cells, especially granulocytes and Ly6C(high) monocytes, even in a normocholesterolemic BM microenvironment. In conformity, macrophages differentiated from hypercholesterolemia-primed HSPCs produced 17.0% more TNF-α, 21.3% more IL-6, and 10.5% more MCP1 than did their normocholesterolemic counterparts. Hypercholesterolemia-induced priming of HSPCs generated leukocytes that more readily migrated into the artery, which resulted in a 2.1-fold increase in atherosclerotic plaque size. In addition, these plaques had a more advanced phenotype and exhibited a 1.2-fold increase in macrophages and 1.8-fold increase in granulocytes. These results identify hypercholesterolemia-induced activation and priming of HSPCs as a novel pathway in the development of atherosclerosis. Inhibition of this proinflammatory differentiation pathway on the HSPC level has the potential to reduce atherosclerosis.

Lymphocytic tumor necrosis factor receptor superfamily co-stimulatory molecules in the pathogenesis of atherosclerosis.

PURPOSE OF REVIEW: The role of lymphocytes in the chronic inflammatory disease atherosclerosis has emerged over the past decade. Co-stimulatory molecules of the heterogeneous tumor necrosis factor receptor superfamily play a pivotal role in lymphocyte activation, proliferation and differentiation. Here we describe the immune modulatory properties and mechanisms of four tumor necrosis factor receptor superfamily members in atherosclerosis. RECENT FINDINGS: CD40/CD40L, OX40L/OX40, CD70/CD27 and CD137/CD137L are present in human atherosclerotic plaques and have shown strong immune modulatory functions in atherosclerosis, resulting in either atherogenic or atheroprotective effects in mouse models of atherosclerosis. SUMMARY: Insight into the immune modulatory mechanisms of co-stimulatory interactions in atherosclerosis can contribute to clinical exploitation of these interactions in the treatment of cardiovascular disease.

Automatic quantification of tumor-stroma ratio as a prognostic marker for pancreatic cancer.

PURPOSE: This study aims to introduce an innovative multi-step pipeline for automatic tumor-stroma ratio (TSR) quantification as a potential prognostic marker for pancreatic cancer, addressing the limitations of existing staging systems and the lack of commonly used prognostic biomarkers. METHODS: The proposed approach involves a deep-learning-based method for the automatic segmentation of tumor epithelial cells, tumor bulk, and stroma from whole-slide images (WSIs). Models were trained using five-fold cross-validation and evaluated on an independent external test set. TSR was computed based on the segmented components. Additionally, TSR's predictive value for six-month survival on the independent external dataset was assessed. RESULTS: Median Dice (inter-quartile range (IQR)) of 0.751(0.15) and 0.726(0.25) for tumor epithelium segmentation on internal and external test sets, respectively. Median Dice of 0.76(0.11) and 0.863(0.17) for tumor bulk segmentation on internal and external test sets, respectively. TSR was evaluated as an independent prognostic marker, demonstrating a cross-validation AUC of 0.61±0.12 for predicting six-month survival on the external dataset. CONCLUSION: Our pipeline for automatic TSR quantification offers promising potential as a prognostic marker for pancreatic cancer. The results underscore the feasibility of computational biomarker discovery in enhancing patient outcome prediction, thus contributing to personalized patient management.

Histology-Based Radiomics for [18F]FDG PET Identifies Tissue Heterogeneity in Pancreatic Cancer.

Radiomics features can reveal hidden patterns in a tumor but usually lack an underlying biologic rationale. In this work, we aimed to investigate whether there is a correlation between radiomics features extracted from [18F]FDG PET images and histologic expression patterns of a glycolytic marker, monocarboxylate transporter-4 (MCT4), in pancreatic cancer. Methods: A cohort of pancreatic ductal adenocarcinoma patients (n = 29) for whom both tumor cross sections and [18F]FDG PET/CT scans were available was used to develop an [18F]FDG PET radiomics signature. By using immunohistochemistry for MCT4, we computed density maps of MCT4 expression and extracted pathomics features. Cluster analysis identified 2 subgroups with distinct MCT4 expression patterns. From corresponding [18F]FDG PET scans, radiomics features that associate with the predefined MCT4 subgroups were identified. Results: Complex heat map visualization showed that the MCT4-high/heterogeneous subgroup was correlating with a higher MCT4 expression level and local variation. This pattern linked to a specific [18F]FDG PET signature, characterized by a higher SUVmean and SUVmax and second-order radiomics features, correlating with local variation. This MCT4-based [18F]FDG PET signature of 7 radiomics features demonstrated prognostic value in an independent cohort of pancreatic cancer patients (n = 71) and identified patients with worse survival. Conclusion: Our cross-modal pipeline allows the development of PET scan signatures based on immunohistochemical analysis of markers of a particular biologic feature, here demonstrated on pancreatic cancer using intratumoral MCT4 expression levels to select [18F]FDG PET radiomics features. This study demonstrated the potential of radiomics scores to noninvasively capture intratumoral marker heterogeneity and identify a subset of pancreatic ductal adenocarcinoma patients with a poor prognosis.

Fibroblast Activation Protein-Targeting Minibody-IRDye700DX for Ablation of the Cancer-Associated Fibroblast with Photodynamic Therapy.

Fibroblast activation protein (FAP), expressed on cancer-associated fibroblasts, is a target for diagnosis and therapy in multiple tumour types. Strategies to systemically deplete FAP-expressing cells show efficacy; however, these induce toxicities, as FAP-expressing cells are found in normal tissues. FAP-targeted photodynamic therapy offers a solution, as it acts only locally and upon activation. Here, a FAP-binding minibody was conjugated to the chelator diethylenetriaminepentaacetic acid (DTPA) and the photosensitizer IRDye700DX (DTPA-700DX-MB). DTPA-700DX-MB showed efficient binding to FAP-overexpressing 3T3 murine fibroblasts (3T3-FAP) and induced the protein's dose-dependent cytotoxicity upon light exposure. Biodistribution of DTPA-700DX-MB in mice carrying either subcutaneous or orthotopic tumours of murine pancreatic ductal adenocarcinoma cells (PDAC299) showed maximal tumour uptake of 111In-labelled DTPA-700DX-MB at 24 h post injection. Co-injection with an excess DTPA-700DX-MB reduced uptake, and autoradiography correlated with FAP expression in the stromal tumour region. Finally, in vivo therapeutic efficacy was determined in two simultaneous subcutaneous PDAC299 tumours; only one was treated with 690 nm light. Upregulation of an apoptosis marker was only observed in the treated tumours. In conclusion, DTPA-700DX-MB binds to FAP-expressing cells and targets PDAC299 tumours in mice with good signal-to-background ratios. Furthermore, the induced apoptosis indicates the feasibility of targeted depletion of FAP-expressing cells with photodynamic therapy.

Progranulin mediates immune evasion of pancreatic ductal adenocarcinoma through regulation of MHCI expression.

Immune evasion is indispensable for cancer initiation and progression, although its underlying mechanisms in pancreatic ductal adenocarcinoma (PDAC) are not fully known. Here, we characterize the function of tumor-derived PGRN in promoting immune evasion in primary PDAC. Tumor- but not macrophage-derived PGRN is associated with poor overall survival in PDAC. Multiplex immunohistochemistry shows low MHC class I (MHCI) expression and lack of CD8+ T cell infiltration in PGRN-high tumors. Inhibition of PGRN abrogates autophagy-dependent MHCI degradation and restores MHCI expression on PDAC cells. Antibody-based blockade of PGRN in a PDAC mouse model remarkably decelerates tumor initiation and progression. Notably, tumors expressing LCMV-gp33 as a model antigen are sensitized to gp33-TCR transgenic T cell-mediated cytotoxicity upon PGRN blockade. Overall, our study shows a crucial function of tumor-derived PGRN in regulating immunogenicity of primary PDAC.

Functional noninvasive detection of glycolytic pancreatic ductal adenocarcinoma.

BACKGROUND: Pancreatic ductal adenocarcinoma (PDAC) lacks effective treatment options beyond chemotherapy. Although molecular subtypes such as classical and QM (quasi-mesenchymal)/basal-like with transcriptome-based distinct signatures have been identified, deduced therapeutic strategies and targets remain elusive. Gene expression data show enrichment of glycolytic genes in the more aggressive and therapy-resistant QM subtype. However, whether the glycolytic transcripts are translated into functional glycolysis that could further be explored for metabolic targeting in QM subtype is still not known. METHODS: We used different patient-derived PDAC model systems (conventional and primary patient-derived cells, patient-derived xenografts (PDX), and patient samples) and performed transcriptional and functional metabolic analysis. These included RNAseq and Illumina HT12 bead array, in vitro Seahorse metabolic flux assays and metabolic drug targeting, and in vivo hyperpolarized [1-13C]pyruvate and [1-13C]lactate magnetic resonance spectroscopy (HP-MRS) in PDAC xenografts. RESULTS: We found that glycolytic metabolic dependencies are not unambiguously functionally exposed in all QM PDACs. Metabolic analysis demonstrated functional metabolic heterogeneity in patient-derived primary cells and less so in conventional cell lines independent of molecular subtype. Importantly, we observed that the glycolytic product lactate is actively imported into the PDAC cells and used in mitochondrial oxidation in both classical and QM PDAC cells, although more actively in the QM cell lines. By using HP-MRS, we were able to noninvasively identify highly glycolytic PDAC xenografts by detecting the last glycolytic enzymatic step and prominent intra-tumoral [1-13C]pyruvate and [1-13C]lactate interconversion in vivo. CONCLUSION: Our study adds functional metabolic phenotyping to transcriptome-based analysis and proposes a functional approach to identify highly glycolytic PDACs as candidates for antimetabolic therapeutic avenues.

An Explorative Study on Monocyte Reprogramming in the Context of Periodontitis In Vitro and In Vivo.

Aims: Periodontitis is an independent risk factor for cardiovascular disease, but the mechanistic link is not fully understood. In atherosclerotic cardiovascular disease, monocytes can adopt a persistent hyperresponsive phenotype, termed trained immunity. We hypothesized that periodontitis-associated bacteria can induce trained immunity in monocytes, which subsequently accelerate atherosclerosis development. Materials and Methods: We combined in vitro experiments on human primary monocytes and in vivo techniques in patients with periodontitis to test this hypothesis. Adherent peripheral blood mononuclear cells (PBMCs) were transiently exposed in vitro to Porphyromonas gingivalis for 24 hours, and restimulated with lipopolysaccharide (LPS) or Pam3CysK4 (P3C) six days later, to measure interleukin-6 (IL-6) and tumor necrosis factor α (TNFα) production. In an exploratory observational study, patients with severe periodontitis (63 ± 6 years, n=14) and control subjects with no-to-mild periodontitis (54 ± 10 years, n=14) underwent venipuncture and 2'-deoxy-2'-[18F]fluoro-D-glucose positron-emission-tomography ([18F]FDG PET/CT) scanning. Results: When adherent peripheral blood mononuclear cells (PBMCs) were transiently exposed in vitro to Porphyromonas gingivalis for 24 hours, and restimulated with LPS or P3C six days later, IL-6 and TNFα production was significantly increased (TNFα/P3C, p<0.01). Circulating leukocytes, IL-6 and interleukin-1 receptor antagonist (IL-1Ra) concentrations were generally higher in patients compared to controls (leukocytes: p<0.01; IL-6: p=0.08; IL-1Ra: p=0.10). Cytokine production capacity in PBMCs after 24h stimulation revealed no differences between groups. [18F]FDG PET/CT imaging showed a trend for increased [18F]FDG-uptake in the periodontium [mean standard uptake value (SUVmean), p=0.11] and in femur bone marrow (SUVmean, p=0.06), but no differences were observed for vascular inflammation. Positive correlations between severity of periodontitis, measured by The Dutch Periodontal Screening Index and pocket depth, with circulating inflammatory markers and tissue inflammation were found. Conclusions: P. gingivalis induces long-term activation of human monocytes in vitro (trained immunity). Patients with severe periodontitis did have signs of increased systemic inflammation and hematopoietic tissue activation. However, their circulating monocytes did not show a hyperresponsive phenotype. Together we suggest that trained immunity might contribute to local periodontal inflammation which warrants further investigation.

Arterial Wall Inflammation and Increased Hematopoietic Activity in Patients With Primary Aldosteronism.

CONTEXT: Primary aldosteronism (PA) confers an increased risk of cardiovascular disease (CVD), independent of blood pressure. Animal models have shown that aldosterone accelerates atherosclerosis through proinflammatory changes in innate immune cells; human data are scarce. OBJECTIVE: The objective of this article is to explore whether patients with PA have increased arterial wall inflammation, systemic inflammation, and reprogramming of monocytes. DESIGN: A cross-sectional cohort study compared vascular inflammation on 2'-deoxy-2'-(18F)fluoro-D-glucose; (18F-FDG) positron emission tomography-computed tomography, systemic inflammation, and monocyte phenotypes and transcriptome between PA patients and controls. SETTING: This study took place at Radboudumc and Rijnstate Hospital, the Netherlands. PATIENTS: Fifteen patients with PA and 15 age-, sex-, and blood pressure-matched controls with essential hypertension (EHT) participated. MAIN OUTCOME MEASURES AND RESULTS: PA patients displayed a higher arterial 18F-FDG uptake in the descending and abdominal aorta (P < .01, P < .05) and carotid and iliac arteries (both P < .01). In addition, bone marrow uptake was higher in PA patients (P < .05). Although PA patients had a higher monocyte-to-lymphocyte ratio (P < .05), systemic inflammatory markers, cytokine production capacity, and transcriptome of circulating monocytes did not differ. Monocyte-derived macrophages from PA patients expressed more TNFA; monocyte-derived macrophages of healthy donors cultured in PA serum displayed increased interleukin-6 and tumor necrosis factor-α production. CONCLUSIONS: Because increased arterial wall inflammation is associated with accelerated atherogenesis and unstable plaques, this might importantly contribute to the increased CVD risk in PA patients. We did not observe inflammatory reprogramming of circulating monocytes. However, subtle inflammatory changes are present in the peripheral blood cell composition and monocyte transcriptome of PA patients, and in their monocyte-derived macrophages. Most likely, arterial inflammation in PA requires interaction between various cell types.

Reprogramming of bone marrow myeloid progenitor cells in patients with severe coronary artery disease.

Atherosclerosis is the major cause of cardiovascular disease (CVD). Monocyte-derived macrophages are the most abundant immune cells in atherosclerotic plaques. In patients with atherosclerotic CVD, leukocytes have a hyperinflammatory phenotype. We hypothesize that immune cell reprogramming in these patients occurs at the level of myeloid progenitors. We included 13 patients with coronary artery disease due to severe atherosclerosis and 13 subjects without atherosclerosis in an exploratory study. Cytokine production capacity after ex vivo stimulation of peripheral blood mononuclear cells (MNCs) and bone marrow MNCs was higher in patients with atherosclerosis. In BM-MNCs this was associated with increased glycolysis and oxidative phosphorylation. The BM composition was skewed towards myelopoiesis and transcriptome analysis of HSC/GMP cell populations revealed enrichment of neutrophil- and monocyte-related pathways. These results show that in patients with atherosclerosis, activation of innate immune cells occurs at the level of myeloid progenitors, which adds exciting opportunities for novel treatment strategies.

Optimal respiratory-gated [18F]FDG PET/CT significantly impacts the quantification of metabolic parameters and their correlation with overall survival in patients with pancreatic ductal adenocarcinoma.

PURPOSE: Metabolic parameters are increasingly being used to characterize tumors. Motion artifacts due to patient respiration introduce uncertainties in quantification of metabolic parameters during positron emission tomography (PET) image acquisition. The present study investigates the impact of amplitude-based optimal respiratory gating (ORG) on quantification of PET-derived image features in patients with pancreatic ductal adenocarcinoma (PDAC), in correlation with overall survival (OS). METHODS: Sixty-nine patients with histologically proven primary PDAC underwent 2'-deoxy-2'-[18F]fluoroglucose ([18F]FDG) PET/CT imaging during diagnostic work-up. Standard image acquisition and reconstruction was performed in accordance with the EANM guidelines and ORG images were reconstructed with a duty cycle of 35%. PET-derived image features, including standard parameters, first- and second-order texture features, were calculated from the standard and corresponding ORG images, and correlation with OS was assessed. RESULTS: ORG significantly impacts the quantification of nearly all features; values of single-voxel parameters (e.g., SUVmax) showed a wider range, volume-based parameters (e.g., SUVmean) were reduced, and texture features were significantly changed. After correction for motion artifacts using ORG, some features that describe intra-tumoral heterogeneity were more strongly correlated to OS. CONCLUSIONS: Correction for respiratory motion artifacts using ORG impacts the quantification of metabolic parameters in PDAC lesions. The correlation of metabolic parameters with OS was significantly affected, in particular parameters that describe intra-tumor heterogeneity. Therefore, interpretation of single-voxel or average metabolic parameters in relation to clinical outcome should be done cautiously. Furthermore, ORG is a valuable tool to improve quantification of intra-tumoral heterogeneity in PDAC.

CD70 limits atherosclerosis and promotes macrophage function.

The co-stimulatory molecule CD70 is expressed on activated immune cells and is known to modulate responses of T, B, and NK cells via its receptor CD27. Until now, there is only limited data describing the role of CD70 in atherosclerosis. We observed that ruptured human carotid atherosclerotic plaques displayed higher CD70 expression than stable carotid atherosclerotic plaques, and that CD70 expression in murine atheroma localized to macrophages. Lack of CD70 impaired the inflammatory capacity (e. g. reactive oxygen species and nitric oxide production) of bone marrow-derived macrophages, increased both M1-like and M2-like macrophage markers, and rendered macrophages metabolically inactive and prone to apoptosis. Moreover, CD70-deficient macrophages expressed diminished levels of scavenger receptors and ABC-transporters, impairing uptake of oxidised low-density lipoprotein (oxLDL) and cholesterol efflux, respectively. Hyperlipidaemic Apoe-/- mice reconstituted with CD70-deficient bone marrow displayed a profound increase in necrotic core size, plaque area, and number of lesional macrophages as compared to mice receiving control bone marrow. Accordingly, 18 week-old, chow diet-fed CD70-deficient Apoe-/- mice displayed larger atheroma characterised by lower cellularity and more advanced plaque phenotype than Apoe-/- mice. In conclusion, CD70 promotes macrophage function and viability and is crucial for effective phagocytosis and efflux of oxLDL. Deficiency in CD70 results in more advanced atheroma. Our data suggest that CD70 mitigates atherosclerosis at least in part by modulating macrophage function.