Immunohistochemical Staining of ELOVL2, LIPG, RPL4, and RPSA Proteins Encoded by Differentially Expressed Genes in Canine Osteosarcoma

Osteosarcoma (OSA) is a metastatic bone tumour. In dogs, it predominantly affects older animals and large and giant breeds. The cancer has poor survival rates due to most patients developing dissemination to secondary sites prior to an initial diagnosis. Therefore, novel therapeutic approaches are required to help overcome the growth and metastatic progression of the disease and increase survival rates. Immunohistochemical staining and histological scoring (H-scoring) are often used for diagnostic and prognostic purposes in human medicine. Unfortunately, these techniques have not yet been fully established and implemented within the veterinary field, but ongoing investigations and developments of potential biomarkers are expanding. Four proteins (ELOVL2, LIPG, RPL4, and RPSA) whose genes showed higher expression in canine OSA underwent immunohistochemical investigations. Immunohistochemistry (IHC) and consequent H-score analysis were performed to investigate nuclear and/or cytoplasmic protein expression encoded by the four canine overexpressed genes (ELOVL2 (n = 22), LIPG (n = 18), RPL4 (n = 18), and RPSA (n = 19)). Statistical analyses of the nuclear/cytoplasmic staining scores of the whole cohort, as well as sex (male versus female) and anatomical location (axial and soft tissue versus appendicular) differences, were conducted. This study revealed novel findings regarding the subcellular expression of the proteins corresponding to the overexpressed genes of interest (ELOVL2, LIPG, RPL4, and RPSA) in Rottweiler OSA, including the identification of significant sex-associated differences for LIPG nuclear staining. These candidate biomarkers could be utilised in future investigations to validate their potential as diagnostic, prognostic, and treatment avenues for canine OSA.