Solid phase synthesis and biological evaluation of probestin as an angiogenesis inhibitor

The 3D in vivo chorioallantoic membrane model and its role in breast cancer research

PURPOSE

We aimed to evaluate the role of the chorioallantoic membrane model (CAM) in breast cancer research.

METHODS

The following is an overview of the use of the CAM in the field of breast cancer research based on a PubMed literature query.

RESULTS

The CAM is a 3D in vivo model that can be used for the analysis of tumor growth, biology and angiogenesis of primary tumor tissue or tumor cell lines. The CAM model has been used in breast cancer research for drug testing, migration assays and the evaluation of vascularization, amongst others. The CAM model is a valuable method that offers a better imitation of the physiological phenomena compared to 2D or 3D in vitro models.

CONCLUSION

The CAM model has primarily and successfully been utilized for the assessment of the tumor biology of established breast cancer cell lines. Further, the CAM model is a promising method to analyze patient derived primary tumor material and could be used as a "patient-specific 3D-tumor-therapy-model" for the cost-efficient evaluation of anti-cancer drugs to find the optimal treatment for breast cancer patients.

Assessment of breast cancer primary tumor material in a 3D in vivo model

BACKGROUND

Breast cancer is the most common malignant tumor in women and highly heterogeneous with a variety of different molecular subtypes. The analysis of the individual tumor biology is necessary to develop a specific and individualized treatment plan for every patient. The chick chorioallantoic membrane (CAM) model, a 3D-in-vivo-tumor-model, could potentially provide a methodology that facilitates the gain of additional information regarding the tumor biology as well as the testing of the tumor's individual sensitivity to different therapies.

OBJECTIVE

The objective was to establish the grafting of different breast cancer primaries onto the CAM for tumor profiling and the investigation of different parameters.

METHODS

Breast cancer primary tissue of different patients was grafted onto the CAM. Subsequently, 3D volume and perfusion measurements were performed during the engraftment period. Histological analyses of the tumors were carried out after the engraftment period.

RESULTS

The grafting of the breast cancer primaries onto the CAM was successful. The tumors remained partially vital and displayed angiogenic development on the CAM.

CONCLUSIONS

Breast cancer primary material can be grafted onto the CAM and we observed visible and measurable changes of perfusion over time.

The chorioallantoic membrane as a bio-barrier model for the evaluation of nanoscale drug delivery systems for tumour therapy

In 2010, the European Parliament and the European Union adopted a directive on the protection of animals used for scientific purposes. The directive aims to protect animals in scientific research, with the final goal of complete replacement of procedures on live animals for scientific and educational purposes as soon as it is scientifically viable. Furthermore, the directive announces the implementation of the 3Rs principle: "When choosing methods, the principles of replacement, reduction and refinement should be implemented through a strict hierarchy of the requirement to use alternative methods." The visibility, accessibility, and the rapid growth of the chorioallantoic membrane (CAM) offers a clear advantage for various manipulations and for the simulation of different Bio-Barriers according to the 3R principle. The extensive vascularisation on the CAM provides an excellent substrate for the cultivation of tumour cells or tumour xenografts which could be used for the therapeutic evaluation of nanoscale drug delivery systems. The tumour can be targeted either by topical application, intratumoural injection or i.v. injection. Different application sites and biological barriers can be examined within a single model.

Effect of the hairpin structure of peptide inhibitors on the blockade of PD-1/PD-L1 axis

Blockade of the PD-1/PD-L1 axis using antibody drugs has been a clinically efficacious immunotherapy in cancer treatment. However, studies on peptide inhibitors blocking the interaction between PD-1/PD-L1 in cancer treatment in clinical practice have not yet been reported. In this study, a series of peptide inhibitors were synthesized based on a continuous sequence of 14 amino acids from PD-L1 and suitable modifications to form a hairpin structure. The effect of inhibitors on the blockage of PD-1/PD-L1 by increasing the stability of the hairpin structure was determined using BLI and co-culture models. The results showed that increasing the stability of the hairpin improved the affinity of inhibitors to PD-1 and increased IL-2 secretion. Therefore, modifying the hairpin structure of peptide inhibitors may be a useful approach to block the interaction between PD-1 and PD-L1.

Molecular Imaging of Aminopeptidase N in Cancer and Angiogenesis

This review focuses on recent advances in the molecular imaging of aminopeptidase N (APN, also known as CD13), a zinc metalloenzyme that cleaves N-terminal neutral amino acids. It is overexpressed in multiple cancer types and also on the surface of vasculature undergoing angiogenesis, making it a promising target for molecular imaging and targeted therapy. Molecular imaging probes for APN are divided into two large subgroups: reactive and nonreactive. The structures of the reactive probes (substrates) contain a reporter group that is cleaved and released by the APN enzyme. The nonreactive probes are not cleaved by the enzyme and contain an antibody, peptide, or nonpeptide for targeting the enzyme exterior or active site. Multivalent homotopic probes utilize multiple copies of the same targeting unit, whereas multivalent heterotopic molecular probes are equipped with different targeting units for different receptors. Several recent preclinical cancer imaging studies have shown that multivalent APN probes exhibit enhanced tumor specificity and accumulation compared to monovalent analogues. The few studies that have evaluated APN-specific probes for imaging angiogenesis have focused on cardiac regeneration. These promising results suggest that APN imaging can be expanded to detect and monitor other diseases that are associated with angiogenesis.

Evaluation of 99mTc-probestin for imaging APN expressing tumors by SPECT

Aminopeptidase N (APN) is known to play important roles in tumor angiogenesis, tumor cell invasion, and metastasis. Thus, APN is an attractive biomarker for imaging tumor angiogenesis. Here we report results obtained from biodistribution and single photon emission computed tomography (SPECT) imaging studies of a technetium-99m labeled probestin (a potent APN inhibitor) conjugate containing a tripeptide, Asp-DAP-Cys (DAP=2,3-diaminopropionic acid), chelator and a 8-amino-3,6-dioxaoctanoic acid (PEG2) linker conducted in nude mice xenografted with HT-1080 human fibrosarcoma tumors (APN-positive tumors). These results collectively demonstrate that (99m)Tc-probestin uptake by tumors and other APN expressing tissues in vivo is specific and validate the use of probestin as a vector for targeting APN in vivo.