Downregulation of transforming growth factor β (TGFβ) and latent TGFβ binding protein (LTBP)-4 expression in late stage canine mammary tumours

Although canine mammary tumours (CMT) are the most common malignant tumours in bitches the pathogenesis is far from understood. To analyse the role of the transforming growth factor β (TGFβ) family in the carcinogenesis of CMT, relative mRNA and protein expression of TGFβ-1, -2 and -3, TGFβ receptor (TGFβR)-1 and -3, latent TGFβ-binding protein (LTBP)-1, -3 and -4, and oestrogen receptor α in CMT were quantified. mRNA expression concentrations were measured in laser-microdissected tissue samples of mammary adenomas, carcinomas and their lymph node metastases and normalised to the non-neoplastic mammary gland of the same dog.Carcinomas and metastases had significantly decreased expression levels of TGFβ-3, TGFβR-3 and LTBP-4, but increased LTBP-1 expression when compared to non-neoplastic glands or adenomas. Decreased TGFβ and LTBP-4 expression were confirmed immunohistochemically. The data suggested that loss of TGFβ-3 and LTBP-4 may have growth-stimulatory effects in late-stage tumours, and loss of their expression, together with reduced TGFβR-3 expression, may be associated with increased proliferative activity of CMT similar to findings in human breast cancer.