It has been shown that, preferentially inside the brain, XIST (X-inactive-specific transcript) works as a metastatic suppressor gene, as demonstrated by XIST downregulation promoting epithelial-mesenchymal transition (EMT), MSN/c-Met, and small EV miR-503 release, all of which leads to the development of metastatic traits in tumor stem cells and microenvironment reprogramming via small EV-mediated communication. Here, XIST is linked to neoplasm.