We report that lncRNA XIST (X-inactive-specific transcript), which is involved in genomic imprinting and the transcriptional silencing of genes on the X chromosome and is highly expressed in tumor tissues [11–15], is an epigenetic regulator targeted by miR-7 that directly bound and inhibited XIST expression in breast cancer by using the RNA in vivo precipitation (RIP) method, which underlies the attenuation of properties of BCSCs and the decrease of the BCSC subset. Here, XIST is linked to breast carcinoma.