Breast cancer is a complex and devastating disease with a very significant impact on health throughout the world. In Argentina, breast cancer is the leading cause of death from malignant disease in women.

Steroid hormone receptors (such as the estrogen and progesterone receptors), and growth factor receptors such as the receptor tyrosine kinases of the ErbB/HER family are key players in breast cancer. Approximately 15–20% of breast cancers (BC) show either membrane overexpression of ErbB-2, or its gene amplification. ErbB-2 constitutes the target of several breast cancer therapies. Our studies focus on finding the proteins that constitute the points of convergence between steroid hormones and growth factors to design useful therapeutic alternatives for breast cancer resistant to hormone therapy and ErbB-2-targeted therapies. While ErbB-2 is usually a plasma membrane-bound receptor, it also migrates to the nucleus (NErbB-2) where it acts as a transcriptional regulator involved in tumor growth and resistance to current treatments. We recently identified that ErbB-2 is also found in the nucleus in patients with triple-negative breast cancer, the most aggressive breast cancer subtype, and that nuclear ErbB-2 is a biomarker of poor prognosis in these patients. A deeper understanding of nuclear ErbB-2 actions would be crucial to the disclosure of its role as a biomarker and a target of therapy in BC.