Cancer starts with one rogue cell. Through mutations and genomic alterations, the cell acquires specific and stem cell-like characteristics necessary for invasion of a distant organ and ultimately metastasis. Metastatic brain cancer is a particularly formidable disease because of its poor prognosis and the highly resistant nature of the tumor to chemotherapy. Although several types of primary tumors have a tendency to metastasize to the brain, the incidence of brain metastases has increased dramatically in some subsets of breast cancer patients. Several conventional treatments are available, but success is limited and often short-lived. Given that no standard treatment options exist, there is a significant need to investigate the biology of these clinically recalcitrant tumors.
Keywords: blood–brain barrier; breast cancer; epithelial–mesenchymal transition; mesenchymal–epithelial transition; metastasis.