miRNAs in Cancer Invasion and Metastasis

The discovery of microRNAs (miRNAs), and their ability to regulate a plethora of biological processes, has opened up the possibility of the role of miRNAs in cancer invasion and the metastatic cascade. This chapter focuses on the role of miRNAs in cancer metastasis, particularly their involvement in each step of the metastatic cascade. Detachment and invasion of the primary tumor cells occurs early in the metastatic cascade. Some of the early characteristics of cell detachment and invasion are the activation of matrix metalloproteinases (MMPs), subsequent breakdown of the basement membrane, and epithelial-to-mesenchymal transition (EMT). The process of intravasation involves the movement of cancer cells through the basement membrane and into the blood stream. Prognostic markers of ependymomas, or tumors of the central nervous system, include let-7d, miR-596, and -367. Currently the research on miRNAs involved in the steps of metastasis is lacking in two areas: intravasation and extravasation.