Expression of prolactin receptors in normal canine mammary tissue, canine mammary adenomas and mammary adenocarcinomas

Abstract

BackgroundMammary tumors represent the most common neoplastic disease in female dogs. Recently, the promoting role of prolactin (PRL) in the development of human breast carcinoma has been shown. Possible proliferative, anti-apoptotic, migratory and angiogenic effects of PRL on human mammary cancer cells in vitro and in vivo were suggested. The effects of PRL are mediated by its receptor, and alterations in receptor expression are likely to play a role in tumor development. Currently, not much data is available about prolactin receptor (PRLR) expression in canine mammary tumors. To set the basis for investigations on the role of PRL in mammary tumorigenesis in this species, prolactin receptor expression was evaluated by semi-quantitative real time PCR and immunohistochemistry on 10 formalin-fixed, paraffin-embedded samples each of canine non-neoplastic mammary tissue, mammary adenomas and adenocarcinomas.ResultsThe highest PRLR expression levels were found in normal mammary tissue, while adenomas, and to an even higher degree adenocarcinomas, showed a significant decrease in prolactin receptor expression. Compared to normal tissue, PRLR mRNA was reduced 2.4 fold (p = 0.0261) in adenomas and 4.8 fold (p = 0.008) in adenocarcinomas. PRLR mRNA expression was significantly lower in malignant than in benign lesions (p = 0.0165). Immunohistochemistry demonstrated PRLR expression in all three tissue types with signals mostly limited to epithelial cells.ConclusionsMalignant transformation of mammary tissue was associated with a decline in prolactin receptor expression. Further studies are warranted to address the functional significance of this finding.

Assessment of Prolactin, Steroid Hormone Levels in Tissue Homogenate, Serum and Receptor Distributions in Canine Mammary Tumours

“…Normal canine mammary tissues and benign lesions of the mammary gland were found to express high levels of PRL-Rs. Malignancy is controversially correlated with the expression of this receptor, which was compatible with our findings [19] . The lack of immunoreactivity for AR in most of the cases was associated with the shortfall of the selected clone of the receptor marker applied in this study.…”

Canine Mammary Tumors: Risk Factors, Prognosis and Treatments

“…A study showed that bitches with mammary tumors have higher serum PRL levels than healthy ones, and PRL levels in mammary tissue are greater in MMT than in BMT or normal glands, suggesting that neoplastic mammary tissue could be a source of PRL (Queiroga et al, 2005). Moreover, Michel et al, (2012) observed that PRL receptor expression is lower in MMT than BMT, suggesting that the loss of this receptor may be a characteristic of tumor dedifferentiation.…”

Clinical and prognostic implications of serum and tissue prolactin levels in canine mammary tumours

“…Recently, the occurrence of prolactin receptor was also described in normal mammary glands and in benign and malignant mammary tumours (Michel and others 2012). …”