SUMMARY Inducing graft acceptance without chronic immunosuppression remains an elusive goal in organ transplantation. Using an experimental transplantation mouse model, we demonstrate that local macrophage activation through dectin-1 and toll-like receptor 4 (TLR4) drives trained immunity-associated cytokine production during allograft rejection. We conducted nanoimmunotherapeutic studies and found that a short- term mTOR-specific high-density lipoprotein (HDL) nanobiologic treatment (mTORi-HDL) averted macrophage aerobic glycolysis and the epigenetic modifications underlying inflammatory cytokine production. The resulting regulatory macrophages prevented alloreactive CD8+ T cell-mediated immunity and promoted tolerogenic CD4+ regulatory T cell (Treg) expansion. To enhance therapeutic efficacy, we complemented the mTORi-HDL treatment with a CD40-TRAF6 specific nanobiologic (TRAF6i-HDL) that inhibits co-stimulation. This synergistic nanoimunnotherapy resulted in indefinite allograft survival. Together, we show that HDL- based nanoimmunotherapy can be employed to control macrophage function in vivo. Our strategy, focused on preventing inflammatory innate immune responses, provides a framework for developing targeted therapies that promote immunological tolerance.

IntroductionTumor cells can effectively be killed by heat, e.g. by using magnetic hyperthermia. The main challenge in the field, however, is the generation of therapeutic temperatures selectively in the whole tumor region. We aimed to improve magnetic hyperthermia of breast cancer by using innovative nanoparticles which display a high heating potential and are functionalized with a cell internalization and a chemotherapeutic agent to increase cell death.MethodsThe superparamagnetic iron oxide nanoparticles (MF66) were electrostatically functionalized with either Nucant multivalent pseudopeptide (N6L; MF66-N6L), doxorubicin (DOX; MF66-DOX) or both (MF66-N6LDOX). Their cytotoxic potential was assessed in a breast adenocarcinoma cell line MDA-MB-231. Therapeutic efficacy was analyzed on subcutaneous MDA-MB-231 tumor bearing female athymic nude mice.ResultsAll nanoparticle variants showed an excellent heating potential around 500 W/g Fe in the alternating magnetic field (AMF, conditions: H = 15.4 kA/m, f = 435 kHz). We could show a gradual inter- and intracellular release of the ligands, and nanoparticle uptake in cells was increased by the N6L functionalization. MF66-DOX and MF66-N6LDOX in combination with hyperthermia were more cytotoxic to breast cancer cells than the respective free ligands. We observed a substantial tumor growth inhibition (to 40% of the initial tumor volume, complete tumor regression in many cases) after intratumoral injection of the nanoparticles in vivo. The proliferative activity of the remaining tumor tissue was distinctly reduced.ConclusionThe therapeutic effects of breast cancer magnetic hyperthermia could be strongly enhanced by the combination of MF66 functionalized with N6L and DOX and magnetic hyperthermia. Our approach combines two ways of tumor cell killing (magnetic hyperthermia and chemotherapy) and represents a straightforward strategy for translation into the clinical practice when injecting nanoparticles intratumorally.Electronic supplementary materialThe online version of this article (doi:10.1186/s13058-015-0576-1) contains supplementary material, which is available to authorized users.

PurposeTumor cells can be effectively inactivated by heating mediated by magnetic nanoparticles. However, optimized nanomaterials to supply thermal stress inside the tumor remain to be identified. The present study investigates the therapeutic effects of magnetic hyperthermia induced by superparamagnetic iron oxide nanoparticles on breast (MDA-MB-231) and pancreatic cancer (BxPC-3) xenografts in mice in vivo.MethodsSuperparamagnetic iron oxide nanoparticles, synthesized either via an aqueous (MF66; average core size 12 nm) or an organic route (OD15; average core size 15 nm) are analyzed in terms of their specific absorption rate (SAR), cell uptake and their effectivity in in vivo hyperthermia treatment.ResultsExceptionally high SAR values ranging from 658 ± 53 W*gFe−1 for OD15 up to 900 ± 22 W*gFe−1 for MF66 were determined in an alternating magnetic field (AMF, H = 15.4 kA*m−1 (19 mT), f = 435 kHz). Conversion of SAR values into system-independent intrinsic loss power (ILP, 6.4 ± 0.5 nH*m2*kg−1 (OD15) and 8.7 ± 0.2 nH*m2*kg−1 (MF66)) confirmed the markedly high heating potential compared to recently published data. Magnetic hyperthermia after intratumoral nanoparticle injection results in dramatically reduced tumor volume in both cancer models, although the applied temperature dosages measured as CEM43T90 (cumulative equivalent minutes at 43°C) are only between 1 and 24 min. Histological analysis of magnetic hyperthermia treated tumor tissue exhibit alterations in cell viability (apoptosis and necrosis) and show a decreased cell proliferation.ConclusionsConcluding, the studied magnetic nanoparticles lead to extensive cell death in human tumor xenografts and are considered suitable platforms for future hyperthermic studies.Electronic supplementary materialThe online version of this article (doi:10.1007/s11095-014-1417-0) contains supplementary material, which is available to authorized users.

Purpose The current study presents [18F]PARPi as imaging agent for PARP1 expression. Procedures [18F]PARPi was generated by conjugating a 2H-phthalazin-1-one scaffold to 4-[18F]fluorobenzoic acid. Biochemical assays, optical in vivo competition, biodistribution analysis, positron emission tomography (PET)/X-ray computed tomography, and PET/ magnetic resonance imaging studies were performed in subcutaneous and orthotopic mouse models of glioblastoma. Results [18F]PARPi shows suitable pharmacokinetic properties for brain tumor imaging (IC50=2.8±1.1 nM; logPCHI=2.15±0.41; plasma-free fraction=63.9±12.6 %) and accumulates selectively in orthotopic brain tumor tissue. Tracer accumulation in subcutaneous brain tumors was 1.82±0.21 %ID/g, whereas in healthy brain, the uptake was only 0.04±0.01 %ID/g. Conclusions [18F]PARPi is a selective PARP1 imaging agent that can be used to visualize glioblastoma in xenograft and orthotopic mouse models with high precision and good signal/noise ratios. It offers new opportunities to non-invasively image tumor growth and monitor interventions.

Insufficient chemotherapy response and rapid disease progression remain concerns for small-cell lung cancer (SCLC). Oncologists rely on serial CT scanning to guide treatment decisions, but this cannot assess in vivo target engagement of therapeutic agents. Biomarker assessments in biopsy material do not assess contemporaneous target expression, intratumoral drug exposure, or drug-target engagement. Here, we report the use of PARP1/2-targeted imaging to measure target engagement of PARP inhibitors in vivo. Using a panel of clinical PARP inhibitors, we show that PARP imaging can quantify target engagement of chemically diverse small molecule inhibitors in vitro and in vivo. We measure PARP1/2 inhibition over time to calculate effective doses for individual drugs. Using patient-derived xenografts, we demonstrate that different therapeutics achieve similar integrated inhibition efficiencies under different dosing regimens. This imaging approach to non-invasive, quantitative assessment of dynamic intratumoral target inhibition may improve patient care through real-time monitoring of drug delivery.

Integrins have been extensively investigated as therapeutic targets over the last decades, which has been inspired by their multiple functions in cancer progression, metastasis, and angiogenesis as well as a continuously expanding number of other diseases, e.g., sepsis, fibrosis, and viral infections, possibly also Severe Acute Respiratory Syndrome Coronavirus (SARS-CoV-2). Although integrin-targeted (cancer) therapy trials did not meet the high expectations yet, integrins are still valid and promising targets due to their elevated expression and surface accessibility on diseased cells. Thus, for the future successful clinical translation of integrin-targeted compounds, revisited and innovative treatment strategies have to be explored based on accumulated knowledge of integrin biology. For this, refined approaches are demanded aiming at alternative and improved preclinical models, optimized selectivity and pharmacological properties of integrin ligands, as well as more sophisticated treatment protocols considering dose fine-tuning of compounds. Moreover, integrin ligands exert high accuracy in disease monitoring as diagnostic molecular imaging tools, enabling patient selection for individualized integrin-targeted therapy. The present review comprehensively analyzes the state-of-the-art knowledge on the roles of RGD-binding integrin subtypes in cancer and non-cancerous diseases and outlines the latest achievements in the design and development of synthetic ligands and their application in biomedical, translational, and molecular imaging approaches. Indeed, substantial progress has already been made, including advanced ligand designs, numerous elaborated pre-clinical and first-in-human studies, while the discovery of novel applications for integrin ligands remains to be explored.

BackgroundAlthough the understanding of the genetic and molecular basis of cancer has advanced significantly over the past several decades, imaging and treatment options for glioblastoma patients have been more limited (N Engl J Med 359:492-507, 2008). This is in part due to difficulties in diagnosing this disease early, combined with its diffuse, infiltrative growth. This study was aimed at the development of a novel diagnostic tool for glioblastoma through the synthesis of a small molecule based on radioiodinated poly(ADP-ribose)polymerase 1 (PARP1) targeted tracers. This PARP1 is a biomarker that is overexpressed in glioblastoma tissue, but has only low expression levels in the healthy brain (Neoplasia 16:432-40, 2014).MethodsA library of PARP1 inhibitors (iodo-PARPis) was synthesized. Based on their pharmacokinetic properties and nuclear PARP1 binding, the most successful inhibitor was radiolabeled with 131I and 124I. Biodistribution as well as imaging experiments were performed in orthotopic and subcutaneous mouse models of glioblastoma.ResultsOne member of our iodo-poly(ADP-ribose)polymerase 1 (PARP1) inhibitor library, I2-PARPi, shows promising biophysical properties for in vivo application. All synthesized tracers have IC50 values in the nanomolar range (9 ± 2–107 ± 4 nM) and were able to inhibit the uptake of a fluorescent PARP1 inhibitor analog (PARPi-FL). I2-PARPi was able to reduce the uptake of PARPi-FL by 78 ± 4 % in vivo. In mouse models of glioblastoma, we show that the radioiodinated inhibitor analog has high uptake in tumor tissue (U251 MG xenograft, tumor, 0.43 ± 0.06 %ID/g; brain, 0.01 ± 0.00 %ID/g; muscle, 0.03 ± 0.01 %ID/g; liver, 2.35 ± 0.57 %ID/g; thyroid, 0.24 ± 0.06 %ID/g). PET and SPECT imaging performed in orthotopic glioblastoma models with [124I]- and [131I]-I2-PARPi showed selective accumulation in the tumor tissue. These results were also verified using autoradiography of tumor sections, which displayed focal selective uptake of the tracer in the tumor regions as confirmed by histology. The uptake could be blocked through pre-injection of excess unlabeled PARP1 inhibitor (Olaparib).ConclusionsWe have successfully synthesized and radioiodinated the PARP1 selective tracer I2-PARPi. The novel tracer shows selective binding to tumor tissue, both in vitro and in models of glioblastoma, and has the potential to serve as a selective PET imaging agent for brain tumors.Electronic supplementary materialThe online version of this article (doi:10.1186/s13550-015-0123-1) contains supplementary material, which is available to authorized users.

The poly(adenosine diphosphate-ribose)polymerase (PARP) family of enzymes is an important factor in the cellular DNA damage response and has gained much attention for its role in many diseases, particularly cancer. Targeted molecular imaging of PARP using fluorescent or radiolabeled tags has followed on the success of therapeutic inhibitors and gained momentum over the past few years. This review covers PARP imaging from the very first imaging agents up to the current state of the technology, with a focus on the clinical applications made possible by these agents.