Recently, Xing et al. (2018) demonstrated that breast cancer cells with X-inactive-specific transcript (XIST) deficiency, MCF7-shXIST, release EVs containing miR-503, which promote M1-M2 conversion of microglia via the STAT3 and NF-κB pathways in recipient macrophages, inducing inhibition of T-cell proliferation. Here, XIST is linked to breast cancer.