Given that JARID1b/PLU1/KDM5B has been shown to be expressed in 90% of invasive ductal carcinomas and that KDM5B represses transcription by demethylating H3K4 (Barrett et al., 2002, 2007; Lu et al., 1999; Yamane et al., 2007), we examined whether KDM5B associates with EMSY. This evidence concerns the gene KDM5B and invasive ductal breast carcinoma.