The Anti-Metastatic Properties of Glutathione-Stabilized Gold Nanoparticles-A Preliminary Study on Canine Osteosarcoma Cell Lines.

Osteosarcoma (OSA) is the most common primary bone malignancy in dogs, characterized by aggressive growth and high metastatic potential. Despite advances in treatment, the prognosis for affected animals remains poor, mainly due to metastatic disease. Metastasis is a complex process that involves forming new blood vessels in the primary tumor (angiogenesis), intravasation, the transport of cancer cells to other locations, extravasation, and the growth of cancer cells in the secondary site. Gold nanoparticles (AuNPs), due to their unique physicochemical properties, are considered promising tools in cancer therapy, both as drug delivery systems and potential anti-metastatic agents. Previously, it has been demonstrated that 500 µg/mL glutathione-stabilized gold nanoparticles (Au-GSH NPs) inhibit cancer cell extravasation-one of the steps of the metastatic cascade. This study aimed to evaluate the anti-metastatic properties of Au-GSH NPs through their influence on OSA cell migration, proliferation, and colony formation in vitro, as well as their antiangiogenic properties on the chick embryo chorioallantoic (CAM) model. Additionally, we investigated whether these effects are associated with changes in alpha-2-macroglobulin (A2M) expression, as it was previously demonstrated to play an essential role in the metastatic cascade. Au-GSH NPs significantly inhibited migration and colony formation in canine osteosarcoma cells (from OSCA-8, OSCA-32, and D-17 cell lines) at 200 µg/mL concentrations. Interestingly, at 500 µg/mL, Au-GSH NPs inhibited angiogenesis on the CAM model and cancer cell migration, but fewer colonies were formed. These results may be directly related to the higher efficiency of Au-GSH NPs uptake by OSA cells at the dose of 200 μg/mL than at the dose of 500 μg/mL, as demonstrated using Microwave Plasma Atomic Emission Spectroscopy (MP-AES). Moreover, this is the first study that demonstrates a significant increase in A2M expression in cancer cells after Au-GSH NPs treatment. This study provides new insight into the potential use of Au-GSH NPs as anti-metastatic agents in canine osteosarcoma, indicating that their anti-metastatic properties may be related to A2M. However, further in vitro and in vivo studies are needed to explore the molecular mechanism underlying these effects and to evaluate the clinical relevance of AuNPs in veterinary oncology.