Heat shock protein expression in canine osteosarcoma

Introduction: Abnormal levels of Heat Shock Proteins (HSPs) have been observed in many human neoplasms, demonstrating both prognostic and therapeutic implications. Since human and canine osteosarcoma (OSA) share several biological and molecular features, the aim of this study was to evaluate HSP expression in canine OSA model, in relation to histological grade and overall survival (OS), in order to investigate their potential prognostic and/or therapeutic value. Materials and Methods: Immunohistochemical expression of Hsp27, Hsp72, Hsp73, Hsp90 was evaluated in canine OSA samples of different histological grades. A semi-quantitative method was used to analyse results. Results: Hsp27, Hsp73 and Hsp90 showed a variably intense, cytoplasmic/nuclear immmunoreactivity, not associated with histological type or grade. For Hsp72, immunosignal intensity and percentage of positive cells was highest (≥75%) in grade III, whereas absent immunolabelling was associated with prolonged OS. Neoplastic emboli were inconstantly positive for Hsp27, faintly immmunoreactive for Hsp72 and intensely immunolabelled by Hsp73 and Hsp90. Conclusion: Results demonstrate expression of several HSPs in canine OSA. Absence of Hsp72 immunosignal appears to be associated with favourable prognosis, whereas widespread Hsp90 immunoreactivity detected in tumour cases and neoplastic emboli suggest that this protein can represent a potential molecular target for therapy of human and canine OSA. [...]