Immunohistochemical expression of selected phosphoproteins of the mTOR signalling pathway in canine cutaneous squamous cell carcinoma.

Cutaneous squamous cell carcinoma (cSCC) represents one of the most common malignant skin tumors in dogs. Research aimed at clarifying how the deregulated activity of signalling pathways contributes to cSCC progression can help to identify molecular suitable targets for the development of novel therapies. The present study describes the immunohistochemical expression pattern of two proteins (pAktSer473 and pS6Ser235/236, the latter combined with Ki-67) involved in the phosphatidylinositol 3-kinase/Akt/mammalian target of rapamycin (PI3K/Akt/mTOR) signalling pathway in canine specimens of normal epidermis, pre-neoplastic epidermis, and cSCC using tissue microarrays. The results suggest that the PI3K/Akt/mTOR signalling pathway has a low expression in the normal canine epidermis, and that selected molecules involved in this signalling pathway are dysregulated during the canine epidermal carcinogenesis process. These findings provide important evidence that the persistent activation of the PI3K/Akt/mTOR signalling pathway represents one of the key events during cSCC progression in canine patients, pointing to the PI3K/Akt/mTOR pathway as a potential therapeutic target.