G-coupled protein receptors and breast cancer progression: potential drug targets.

Breast cancer remains a leading cause of death despite early screening and advances in medicine. Bone marrow metastasis often complicates the clinical picture by requiring more aggressive treatment and worsening long-term prognoses. Recent therapeutic targeting of hormonal receptors such as human epidermal growth factor receptor 2 and estrogen receptor has shown limited success in treating localized disease for those patients whose cancer cells are responsive. Although traditional approaches such as chemotherapy have demonstrated many successes, these agents fail to target quiescent cancer stem cells, which might have entered the bone marrow where they might be responsible for the quiescence population. Following years of clinical remission, these dormant cells could lead to secondary cancer resurgence. To date, little progress has been made in the development of targeted treatments for receptor negative and metastatic disease. In this review, we discuss the role of G-protein coupled receptors, including neurokinin-1, neurokinin-2 and chemokine receptor 4, as novel targets in the treatment of breast cancer.