Heat shock proteins expression in canine intracutaneous cornifying epithelioma and squamous cell carcinoma

Heat shock proteins (HSPs) are strongly implicated in the control of cell growth, differentiation and biological behaviour of many human cutaneous neoplasms. To our knowledge, no data have been published in the veterinary literature concerning either normal or neoplastic skin. In this study, the immunohistochemical expression of Hsp27, Hsp72 and Hsp73 was evaluated in normal canine skin, 14 intracutaneous cornifying epitheliomas (ICE), 10 well-differentiated and 5 moderately differentiated squamous cell carcinomas (SCC). Expression was correlated with the histological degree of keratinocyte differentiation and proliferation, and investigated as to its usefulness in the differential diagnosis of these canine tumours. In normal epidermis, Hsp27 exhibited cytoplasmic labelling in the spinous and granular layers, whereas in neoplastic tissues it was detected particularly in those areas showing squamous differentiation. Hsp72 immunoreactivity was more intense in ICE and welldifferentiated SCC than in normal skin; however, reduced immunolabelling was observed in moderately differentiated SCC. Unlike Hsp72, Hsp73 showed less intense labelling in ICE and well-differentiated SCC than in normal epithelium and an increased positivity in moderately differentiated SCC. These results indicate that HSP immunoreactivity differs between normal and neoplastic canine skin. Hsp27 expression seems to correlate directly with cellular differentiation; by contrast, the involvement of Hsp72/73 in proliferation and differentiation of tumour cells remains controversial. The pattern and intensity of immunolabelling of each investigated HSP did not show, however, significant differences between ICE and SCC; therefore, they do not seem to be useful in the differential diagnosis of these two canine tumours.