The role of cancer stem cells and miRNAs in defining the complexities of brain metastasis.

Researchers and clinicians have been challenged with the development of therapies for the treatment of cancer patients whose tumors metastasized to the brain. Among the most lethal weapons known today, current management of brain metastases involves multiple therapeutic modalities that provide little, if any, for improving the quality of life and overall survival. Recently the role of cancer stem cells (CSCs) in the development of cancer has been studied extensively, and thus its role in the prognosis, diagnosis, and treatment is now being investigated even in the realm of brain metastasis (BM). Recognizing the molecular make-up of CSCs as well as understanding the role of these cells in resistance to treatment modalities is expected to benefit cancer patients. Additionally, past decade has witnessed an increase in awareness and understanding of the role of microRNAs (miRNAs) in various cancer types, and the deregulation miRNAs are critically important for the regulation of genes during the development and progression of human malignancies. The role miRNAs in BM is being investigated, and has also shown tremendous promise for future research. In this review, we discuss the problem and lethality of brain metastases and the current state of management, and further provide insight into novel avenues that are worth considering including the biological complexities of CSCs and miRNAs for designing novel therapies.