Targeted therapies and checkpoint inhibitors in sarcoma.

Sarcomas are defined as a group of mesenchymal malignancies with over 100 heterogeneous subtypes. As a rare and difficult to diagnose entity, micrometastasis is already present at the time of diagnosis in many cases. Current treatment practice of sarcomas consists mainly of surgery, (neo)adjuvant chemo- and/or radiotherapy. Although the past decade has shown that particular genetic abnormalities can promote the development of sarcomas, such as translocations, gain-of-function mutations, amplifications or tumor suppressor gene losses, these insights have not led to established alternative treatment strategies so far. Novel therapeutic concepts with immunotherapy at its forefront have experienced some remarkable success in different solid tumors while their impact in sarcoma remains limited. In this review, the most common immunotherapy strategies in sarcomas, such as immune checkpoint inhibitors, targeted therapy and cytokine therapy are concisely discussed. The programmed cell death (PD)-1/PD-1L axis and apoptosis-inducing cytokines, such as TNF-related apoptosis-inducing ligand (TRAIL), have not yielded the same success like in other solid tumors. However, in certain sarcoma subtypes, e.g. liposarcoma or undifferentiated pleomorphic sarcoma, encouraging results in some cases when employing immune checkpoint inhibitors in combination with other treatment options were found. Moreover, newer strategies such as the targeted therapy against the ancient cytokine macrophage migration inhibitory factor (MIF) may represent an interesting approach worth investigation in the future.

[Regulation of bone metabolism by the Wnt signaling pathway]. / Regulation des Knochenstoffwechsels durch den Wnt-Signalweg.

The development and homeostasis of multicellular organisms depends on a complex cellular interaction between proliferation, migration, differentiation, adhesion, and cell death. Wnt signaling pathways coordinate these different cellular responses. Wnt signaling plays a role as a regulatory pathway in the osteogenic differentiation of mesenchymal stem cells. The Wnt signaling pathway is an attractive therapeutic target with the potential to directly modulate stem cells responsible for the regeneration of skeletal tissue. Recent studies indicate that Wnt ligands are capable of promoting bone growth, suggesting that Wnt factors could be used to stimulate bone healing in osteogenic disorders.

The mobilisation of mononuclear cells and endothelial progenitor cells after burn injury in a porcine model.

BACKGROUND: Mononuclear blood cells (MNCs) consist of heterogeneous cell populations, for example, CD34+ cells and endothelial progenitor cells (EPCs). EPCs are involved in vasculogenesis, but little is known about their role during burn trauma. AIM: This study investigates the role of MNCs and their subpopulations during and after burn injury in an experimental porcine setting. METHODS: Eighteen 8-week-old German land pigs were scalded by immersion in 70 degrees C hot water for 3 min, resulting in a 30% total body surface area (TBSA) full-thickness burn. Vascular endothelial growth factor (VEGF) serum concentrations and MNC, EPC and CD34+ cell counts were measured at eight different time points up to 48 h following trauma. RESULTS: The experimental porcine setting made it possible to determine the cell counts of MNCs, EPCs and CD34+ cells directly during burn trauma, which has not been described before. The data revealed a fulminant drop in MNC and EPC during burn trauma, whereas the CD34+ cell fraction rose. Besides significant changes in the VEGF serum concentration, a correlation between VEGF and EPC was also observed. CONCLUSION: The results show that MNCs and their subpopulations are significantly affected by burn trauma and underpin their potential diagnostic and therapeutic importance during and after burn injury.

Tissue substitutes with improved angiogenic capabilities: an in vitro investigation with endothelial cells and endothelial progenitor cells.

The use of implantable biomaterials, such as artificial skin substitutes used for dermal defects, remains limited by the low angiogenic potential of these products. The rapid in vivo degradation of growth factors contributes to the limiting of angiogenesis in biomaterials. Here, we report on collagen sponges in which vascular endothelial growth factor (VEGF) was immobilized through physical binding to heparin, covalently incorporated in the matrix via cross-linking with 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide (EDC) and N-hydroxysuccinimide. The in vitro release of VEGF over time and endothelial cell proliferation were investigated in matrices modified at varying heparin to EDC ratios either nonloaded or loaded with VEGF. ELISA demonstrated a significantly slower in vitro release of VEGF over a period of 5 days from heparinized matrices as compared to their unmodified and cross-linked counterparts. The effects of these modifications on the proliferation of endothelial cells and endothelial progenitor cells were evaluated after 1, 3 and 5 days either according to the bromodeoxyuridine assay or total cell counting with a Neubauer chamber. The endothelial and endothelial progenitor cells cultured in contact with heparinized matrices loaded with VEGF revealed both the highest rate of DNA synthesis and the highest total cell count. Furthermore, these results show that the cross-linking of collagen matrices - both in the presence and absence of heparin - leads to increases of the proliferative activities. We can assume that these changes lead to matrices with increased angiogenic capabilities.

Enhancing angiogenesis in collagen matrices by covalent incorporation of VEGF.

Since the survival of ingrowing cells in biomaterials for regenerative processes largely depends on the supply of nutrients and oxygen, angiogenesis plays an important role in the development of new materials for tissue engineering. In this study we investigated the possibility of enhancing the angiogenic properties of collagen matrices by covalent incorporation of the vascular endothelial growth factor (VEGF). In a previous paper we already reported the use of homo- and heterobifunctional cross-linking agents for modifying collagen matrices [1]. In the present work the angiogenic growth factor was linked to the collagen with the homobifunctional cross-linker disuccinimidyldisuccinatepolyethyleneglycol (SS-PEG-SS) in a two step procedure. The efficiency of the first reaction step-the reaction of SS-PEG-SS with VEGF--was evaluated by western blot analysis. After 10 minutes virtually all of the dimeric molecules VEGF were on average modified by conjugation with 1 cross-linking molecule. The biological activity of the conjugate was investigated by exposing endothelial cells to non-modified VEGF and to VEGF conjugated to the cross-linker. The conjugation only had a limited effect on the mitogenic activity of VEGF. We therefore applied the cross-linking reaction to the VEGF-collagen system. In a first approach the changes were evaluated by the in vitro exposure of HUVECs to non-modified matrices, to matrices in which the VEGF was simply admixed and to matrices in which the VEGF was covalently incorporated. The angiogenic properties were evaluated in vivo with the chorioallantois membrane model. In this assay the chorioallantois membrane of the chicken embryo was exposed to the same set of matrices. The covalent incorporation of VEGF has a small but significant effect both on the formation of microvessels in the chorioallantois membrane and the tissue ingrowth into the implant. The covalent incorporation of angiogenic growth factors may thus be considered as a promising approach for enhancing the angiogenic capabilities of collagen matrices. Also the cross-linking with the homobifunctional cross-linking agent has a positive effect on the angiogenic potential of the collagen matrices.