Biodistribution PET/CT Study of Hemoglobin-DFO-89Zr Complex in Healthy and Lung Tumor-Bearing Mice

Proteins, as a major component of organisms, are considered the preferred biomaterials for drug delivery vehicles. Hemoglobin (Hb) has been recently rediscovered as a potential drug carrier, but its use for biomedical applications still lacks extensive investigation. To further explore the possibility of utilizing Hb as a potential tumor targeting drug carrier, we examined and compared the biodistribution of Hb in healthy and lung tumor-bearing mice, using for the first time ⁸⁹Zr labelled Hb in a positron emission tomography (PET) measurement. Hb displays a very high conjugation yield in its fast and selective reaction with the maleimide-deferoxamine (DFO) bifunctional chelator. The high-resolution X-ray structure of the Hb-DFO complex demonstrated that cysteine β93 is the sole attachment moiety to the αβ-protomer of Hb. The Hb-DFO complex shows quantitative uptake of ⁸⁹Zr in solution as determined by radiochromatography. Injection of 0.03 mg of Hb-DFO-⁸⁹Zr complex in healthy mice indicates very high radioactivity in liver, followed by spleen and lungs, whereas a threefold increased dosage results in intensification of PET signal in kidneys and decreased signal in liver and spleen. No difference in biodistribution pattern is observed between naïve and tumor-bearing mice. Interestingly, the liver Hb uptake did not decrease upon clodronate-mediated macrophage depletion, indicating that other immune cells contribute to Hb clearance. This finding is of particular interest for rapidly developing clinical immunology and projects aiming to target, label or specifically deliver agents to immune cells.

Inhibition of IDO leads to IL-6-dependent systemic inflammation in mice when combined with photodynamic therapy

It was previously reported that the activation of antitumor immune response by photodynamic therapy (PDT) is crucial for its therapeutic outcome. Excessive PDT-mediated inflammation is accompanied by immunosuppressive mechanisms that protect tissues from destruction. Thus, the final effect of PDT strongly depends on the balance between the activation of an adoptive arm of immune response and a range of activated immunosuppressive mechanisms. Here, with flow cytometry and functional tests, we evaluate the immunosuppressive activity of tumor-associated myeloid cells after PDT. We investigate the antitumor potential of PDT combined with indoleamine 2,3-dioxygenase 1 (IDO) inhibitor in the murine 4T1 and E0771 orthotopic breast cancer models. We found that the expression of IDO, elevated after PDT, affects the polarization of T regulatory cells and influences the innate immune response. Our results indicate that, depending on a therapeutic scheme, overcoming IDO-induced immunosuppressive mechanisms after PDT can be beneficial or can lead to a systemic toxic reaction. The inhibition of IDO, shortly after PDT, activates IL-6-dependent toxic reactions that can be diminished by the use of anti-IL-6 antibodies. Our results emphasize that deeper investigation of the physiological role of IDO, an attractive target for immunotherapies of cancer, is of great importance.

Exploiting iron-binding proteins for drug delivery

Currently, many therapies fail due to an insufficient drug dose reaching the target site and high systemic toxicity. Protein-based drug delivery systems that allow an increase in drug concentration at a specific location in the body or predominantly target malignant cells are promising technologies. Due to the high need for iron in many disorders including various types of cancer, iron-binding proteins: transferrin, ferritin and hemoglobin, are a promising tool as drug carriers. In this review we summarize the characteristics of human iron-binding proteins and present their use in targeted drug delivery strategies.

Fluctuations in circulating endothelial progenitor cell levels and acute cardiac graft rejection

INTRODUCTION

Endothelial progenitor cells (EPCs) in nontransplant settings have reparative properties. However, their role in heart transplantation (HT) is not well defined.

OBJECTIVES

The aim of this study was to prospectively evaluate changes in EPC levels in relation to post‑HT rejection.

PATIENTS AND METHODS

EPC levels were measured in 27 HT recipients for 6 months after HT. Acute cellular rejection (ACR) or antibody‑mediated rejection (AMR) were assessed by right ventricular endomyocardial biopsy.

RESULTS

ACR and AMR were observed in 7 (25.9%) and 6 (22.2%) patients, respectively. The ACR status at 1 month post‑HT did not differ with respect to EPC immediately post‑HT. At 1 month post‑HT in patients without ACR or AMR, EPC levels were significantly reduced compared with the measurements immediately post‑HT (P <0.001). On further follow‑up, EPC levels were similar regardless of the rejection events. Nonetheless, greater changes (coefficient of variation) in EPClog (logarithmic transformation) were associated with the risk of AMR or ACR compared with those without any rejection event (median [lower-upper quartile], 15 [13-18] vs 8 [5-13]; P = 0.02 and 22 [14-26] vs 8 [5-13]; P = 0.01, respectively). The receiver operating characteristic curve showed that the coefficient of variation of EPClog of 12 was the optimal cutoff value for the prediction of rejection (area under the curve = 0.85). Higher levels were associated with greater risk of ACR or AMR (P <0.005).

CONCLUSIONS

Early reduction of EPC levels was related to a lower risk of ACR or AMR. Greater changes of EPC‑levels during follow‑up were associated with a significantly higher risk of rejection.

P750Role of circulating endothelial cells post-heart transplantation

Background

The role of endothelial progenitor cells (EPC) in heart transplantation (HT) is not well defined. Thus, the aim of this study was to evaluate prospectively the dynamic changes of circulating EPC levels in relation to post-HT rejection risk.

Methods

There were 27 HT recipients who had EPC from peripheral blood quantified during 6 months follow-up after HT. Patients were monitored regularly, by right ventricular endomyocardial biopsy assessment, for cellular rejection (ACR) defined as grade ≥2 or an antibody-mediated rejection (AMR) characterized by histopathological changes recorded as AMR1H. The primary end-point was acute rejection, either AMR or ACR.

Results

ACR and AMR were observed in 7 (25.9%) and 6 (22.2%) subjects respectively. EPC levels, after logarithmic transformation, immediately post-HT were alike regardless of ACR status, however patients with lower EPC were at risk of AMR at 1 month (Table 1). On the other hand patients with a significant reduction of EPC at 1 month post-HT compared with HT were less likely to have either ACR or AMR (p=0.0003). During longer post-HT observation (12 months) patients had similar EPC levels regardless of the rejection events. Dynamic changes in EPC levels are presented in figure. Nonetheless, greater changes in EPC expressed by coefficient of variation were associated with the risk of either AMR or ACR compared to the participants without rejection (mean [lower–upper quartile]) 15 [13–18] vs 8 [5–13]; p=0.02) and (22 [14–26] vs 8 [5–13]; p=0.01) respectively.

EPC by rejection – 1st month following HT ACR (+) AMR (+) ACR (−) and AMR (−) p^ p p N=3 (mean± SD) N=4 (mean± SD) N=20 (mean± SD) ACR (+) vs ACR (−) and AMR (−) AMR (+) vs ACR (−) and AMR (−) EPC log HT 5.14±1.55 3.81±1.01 5.30±0.88 0.0325 0.97 0.025 EPC log M1 4.97±0.59 3.69±1.33 4.15±1.29 0.4160 0.55 0.78 Delta EPC log M1-HT -0.17±1.98* −0.12±1.30* −1.15±1.18# 0.2195 0.44 0.32 ACR – acute cellular rejection; AMR or – acute antibody-mediated rejection; EPC log – endothelial progenitor cells after logarithmic transformation; HT – within 24 hours post-transplantation; M1 – at 1-month post-transplantation; Delta EPC log M1-HT – difference in EPC log between M1 and HT. #p=0.0003 for the difference between M1 vs HT; *p=ns for the difference between M1 vs HT; ^pP – for the difference among the groups.

Changes in EPC level post-HT

Conclusions

Early reduction of EPC levels was predictive of a lower risk of ACR or AMR. Greater dynamic changes of EPC during 6 months of observation were associated with a higher risk of rejection suggesting an important role of EPC in the pathological processes post-HT. Thus our findings suggest significant role of EPC post-HT with respect to rejection status.

Acknowledgement/Funding

Intramural research grant from the Institute of Cardiology

Antitumor Activity of TLR7 Is Potentiated by CD200R Antibody Leading to Changes in the Tumor Microenvironment

Stimulation of Toll-like receptor 7 (TLR7) activates myeloid cells and boosts the immune response. Previously, we have shown that stimulation of the inhibitory CD200 receptor (CD200R) suppresses TLR7 signaling and that the absence of CD200R signaling leads to a decreased number of papillomas in mice. Here, we investigated the effects of agonistic anti-CD200R on the antitumor activity of a TLR7 agonist (R848) in a syngeneic mouse tumor model. Intratumoral administration of R848 inhibited the growth of the CT26 colon carcinoma and simultaneously decreased CD200R expression in tumor-infiltrating immune cells. The antitumor effects of R848 were potentiated by anti-CD200R. Successfully treated mice were resistant to rechallenge with the same tumor cells. However, the immediate antitumor effects were independent of lymphocytes, because treatment efficacy was similar in wild-type and Rag1^tm1Mom mice. Administration of R848, particularly in combination with anti-CD200R, changed the phenotype of intratumoral myeloid cells. The infiltration with immature MHC-II⁺ macrophages decreased and in parallel monocytes and immature MHC-II^- macrophages increased. Combined treatment decreased the expression of the macrophage markers F4/80, CD206, CD86, CD115, and the ability to produce IL1β, suggesting a shift in the composition of intratumor myeloid cells. Adoptively transferred CD11b⁺ myeloid cells, isolated from the tumors of mice treated with R848 and anti-CD200R, inhibited tumor outgrowth in recipient mice. We conclude that administration of agonistic anti-CD200R improves the antitumor effects of TLR7 signaling and changes the local tumor microenvironment, which becomes less supportive of tumor progression. Cancer Immunol Res; 6(8); 930-40. ©2018 AACR.

Evaluation of phenotypic and functional stability of RAW 264.7 cell line through serial passages

Established cell lines are widely used in research, however an appealing question is the comparability of the cells between various laboratories, their characteristics and stability in time. Problematic is also the cell line misidentification, genetic and phenotypic shift or Mycoplasma contamination which are often forgotten in research papers. The monocyte/macrophage-like cell line RAW 264.7 has been one of the most commonly used myeloid cell line for more than 40 years. Despite its phenotypic and functional stability is often discussed in literature or at various scientific discussion panels, their stability during the consecutive passages has not been confirmed in any solid study. So far, only a few functional features of these cells have been studied, for example their ability to differentiate into osteoclasts. Therefore, in the present paper we have investigated the phenotype and functional stability of the RAW 264.7 cell line from passage no. 5 till passage no. 50. We found out that the phenotype (expression of particular macrophage-characteristic genes and surface markers) and functional characteristics (phagocytosis and NO production) of RAW 264.7 cell line remains stable through passages: from passage no. 10 up to passage no. 30. Overall, our results indicated that the RAW 264.7 cell line should not be used after the passage no. 30 otherwise it may influence the data reliability.

MicroRNA in cardiovascular biology and disease

MicroRNAs (miRNAs) are members of a non-coding RNA family. They act as negative regulators of protein translation by affecting messenger RNA (mRNA) stability; they modulate numerous signaling pathways and cellular processes, and are involved in cell-to-cell communication. Thus, studies on miRNAs offer an opportunity to improve our understanding of complex biological mechanisms. In the cardiovascular system, miRNAs control functions of various cells, such as cardiomyocytes, endothelial cells, smooth muscle cells and fibroblasts. The pivotal role of miRNAs in the cardiovascular system provides a new perspective on the pathophysiology of disorders like myocardial infarction, hypertrophy, fibrosis, heart failure, arrhythmia, inflammation and atherosclerosis. MiRNAs are differentially expressed in diseased tissue and can be released into circulation. Manipulation of miRNA activity may influence the course of a disease. Therefore, miRNAs have become an active field of research for developing new diagnostic and therapeutic tools. This review discusses emerging functions of miRNAs in cardiogenesis, heart regeneration and the pathophysiology of cardiovascular diseases.