Heat shock protein expression in canine peripheral nerve sheath tumours

Introduction: Abnormal levels of Heat Shock Proteins (HSPs) have been observed in many human neoplasms, demonstrating both prognostic and therapeutic implications. Since information concerning HSP expression in peripheral nerve sheath tumours (PNST) are limited, the aim of this study was to evaluate their expression in canine PNST, in order to investigate their potential prognostic and/or therapeutic value. Materials and Methods: Immunohistochemical expression and localization of Hsp27, Hsp32 and Hsp90 were evaluated in 4 benign PNST, 15 malignant PNST and normal peripheral nerves of canine species. A semi-quantitative method was used for the analysis of the results. Results: In normal tissue, expression of all investigated HSPs was detected in axons, epineurial fibroblasts and scattered Schwann cells. In benign PNST, all HSPs showed a diffuse, moderate to intense cytoplasmic and nuclear immmunoreactivity, with prevalence of nuclear signal for Hsp32. In malignant PNST, Hsp27 immunolabelling was reduced in both intensity and percentage of positive cells; Hsp32 exhibited high percentage of positivity in the most of tumour samples, characterized by predominant cytoplasmic localization and presence of scattered more intensely labelled tumour cells; Hsp90 showed an intense and diffuse immunosignal in all cases. Conclusion: These results demonstrate different expression patterns of Hsp27 and Hsp32 in benign and malignant PNST. In addition, high immunoreactivity of Hsp90 detected in all tumour cases suggest that this protein can represent a potential molecular target for therapy of this kind of tumours, as also recently hypothesized for the human counterpart.