Pax-5 is a potent regulator of E-cadherin and breast cancer malignant processes.

Pax-5, an essential transcription factor for B lymphocyte development, has been linked with the development and progression of lymphoid cancers and carcinoma. In contrast to B-cell cancer lesions, the specific expression signatures and roles of Pax-5 in breast cancer progression are relatively unknown. In the present study, we set out to profile Pax-5 expression in mammary tissues and elucidate the cellular and molecular roles of Pax-5 in breast cancer processes. Using immunohistology on mammary tissue arrays, Pax-5 was detected in a total of 298/306 (97.6%) samples tested. Interestingly, our studies reveal that Pax-5 inhibits aggressive features and confers anti-proliferative effects in breast carcinoma cells in contrast to its oncogenic properties in B cell cancers. More precisely, Pax-5 suppressed breast cancer cell migration, invasion and tumor spheroid formation while concomitantly promoting cell adhesion properties. We also observed that Pax-5 inhibited and reversed breast cancer epithelial to mesenchymal phenotypic transitioning. Mechanistically, we found that the Pax-5 transcription factor binds and induces gene expression of E-cadherin, a pivotal regulator of epithelialisation. Globally, we demonstrate that Pax-5 is predominant expressed factor in mammary epithelial cells. We also present an important role for Pax-5 in the phenotypic transitioning processes and aggressive features associated with breast cancer malignancy and disease progression.