In the breast cancer cell lines, MDA-MB-231 and MCF7, the inhibition of the KDM6B demethylase activity, using the specific inhibitor GSKJ4, led to a repression of the expression of the multipotent SOX2, NANOG, and OCT4 genes, a decrease of which was linked to an increase of the H3K27me3 mark on their promoters. The gene discussed is KDM6B; the disease is breast cancer.