Identification and Characterisation of Canine Osteosarcoma Biomarkers and Therapeutic Targets

<b>Background:</b> Osteosarcoma (OSA) is the most common type of bone cancer in canines. Novel therapies are required to prevent the growth, survival, and metastatic progression of this cancer, to increase life expectancy of patients. Immunohistochemical (IHC) studies and RNA sequencing help us gain a deeper understanding into the molecular mechanisms of the disease. <b>Methods:</b> We previously compared canine OSA tissues with patient matched non-tumour tissues, revealing 442 overexpressed genes within the samples. The present research used IHC staining for four of these genes in OSA tissues: G protein-coupled receptor 64 (<i>GPR64</i>), TOX High Mobility Group Box Family Member 3 (<i>TOX3</i>), Matrix Metallopeptidase 12 (<i>MMP-12</i>), and Forkhead Box F1 (<i>FOXF1</i>). H-scoring was performed to quantitatively assess protein expression and qualitatively contextualise staining locations. Additional analyses addressed whether gender or anatomical location of lesions (axial or appendicular tumours) affected protein expression. cBioPortal was employed to analyse expression and genetic alterations in patients. <b>Results:</b><i>GPR64</i>, <i>TOX3</i>, <i>MMP-12</i>, and <i>FOXF1</i> showed high mRNA expression and genetic alterations in people with OSA. GPR64, TOX3, MMP-12, and FOXF1 were all expressed in canine OSA with novel findings regarding cellular expression. Additionally, differential sex expression was revealed for GPR64 and TOX3. Potential biomarkers or therapeutic targets were identified. <b>Conclusions:</b> These studies, and subsequent analysis, have provided insights into the molecular mechanisms associated with OSA progression and revealed potential biomarkers for diagnostic and prognostic purposes. A deeper understanding of genetic and protein interactions will support and progress novel pathways towards diagnostic, prognostic, and treatment interventions for OSA in both veterinary and human medicine.