The noncoding RNA XIST becomes activated in a portion of cancers affecting men, a new study had found. Typically, XIST is inactive in somatic male cells, but is active in somatic female cells where it mediates X chromosome inactivation. But as they report in Cell Systems, researchers from Dana-Farber Cancer Institute found by scouring though publicly available datasets of human cancers that XIST becomes active in some tumors isolated from men, including in liver, brain, heart, and other cancers. Similar to non-cancerous female somatic cells, this XIST activation led to decreased gene expression and chromatin accessibility but increased DNA methylation along the X chromosomes. According to the researchers, this X inactivation in tumor cells from men could stem from their genetic instability and the presence of multiple copies of the same chromosome — including the X chromosome. "Another possibility is there are some important genes on the X chromosome that, when silenced, enable the cancer to grow. We will investigate this in future studies," senior author Srinivas Viswanatha from Dana-Farber says in a statement.