Strong expression of interleukin-17 is associated with higher histologic grades in canine mammary carcinoma

Mammary tumours are considered as an important health problem in female dogs and because of its numerous common characteristics with human breast cancer, it can be used as a good model for breast cancer studies. Interleukin-17 is a pro-inflammatory cytokine which is mainly secreted by activated Th-17 cells. There are evidences suggesting that interleukin-17 can be produced by various types of tumour cells and tumour-associated inflammatory cells. It also plays important roles in carcinogenesis by having both anti-tumour and pro-tumour functions. This study investigates interleukin-17 expression in canine mammary tumours by immunohistochemistry and its relationships with histologic grades, tumour recurrence and survival after 2 years. Results showed that 23 samples (63.88%) showed strong immunoreactivity for interleukin-17 and 13 samples (36.11%) showed moderate immunoreactivity. Interleukin-17 expression is significantly increased in canine mammary tumours compared to normal canine mammary tissues (P < 0.05). Furthermore, our results showed that interleukin-17 increased expression is significantly associated with high histologic grade (P < 0.05). Interleukin-17 may be involved in pathogenesis of canine mammary tumours by promoting malignancy grades; however, more investigations are needed to clarify this idea.