Gambogenic Acid Inhibits Tumor Angiogenesis and Growth in Canine Osteosarcoma via Fibronectin Type III and SPRY Domain Containing 1 (FSD 1) Modulation

Osteosarcoma (OS) represents the most prevalent primary bone malignancy in dogs, and its growth and metastasis are highly dependent on angiogenesis.Gambogenic acid (GNA), a principal active component of the traditional Chinese medicine Garcinia hanburyi, has been demonstrated to possess broad-spectrum anti-tumor activity with low toxicity.Nevertheless, its effect on tumor angiogenesis in the canine OS has not yet been elucidated.This study aimed to investigate the effect of GNA on angiogenesis in the canine OS.The McKinley and Gracie canine OS cell lines were selected, and canine vascular endothelial cells (VECs) were isolated to establish an OS-VECs co-culture system.This system was used to evaluate the effects of GNA on the malignant behavior of OS cells and angiogenesis.Fibronectin Type III and SPRY Domain Containing 1 (FSD1) were overexpressed to investigate its role in canine OS cells and to determine whether it mediated the anti-tumor mechanisms of GNA.A subcutaneous xenograft tumor model was constructed in nude mice to validate the effects of GNA on tumor growth and angiogenesis.The results showed that GNA, with IC₅₀ values of 0.28μM (McKinley) and 0.22μM (Gracie), inhibited the malignant behaviors and vasculogenic mimicry capacity of canine OS cells, and reduced the expression of several angiogenic factors.The microenvironment of GNA-treated canine OS cells suppressed the angiogenic capacity of VECs.Overexpression of FSD1 reversed the aforementioned anti-tumor effects of GNA.Gambogenic acid inhibited transplanted tumor growth, decreased microvessel density, and suppressed the expression of FSD1.In conclusion, this study found that GNA effectively inhibited the canine OS growth and angiogenesis by down-regulating FSD1, which supplemented the pharmacological mechanism of GNA anti-tumor activity.