KDM5B and breast cancer: In luminal breast cancer, Jarid1b is a luminal lineage‐driving oncogene.14 Leukaemia stem cell (LSC) differentiation is associated with downregulation of H3K4me3 profiles, and overexpression (O/E) of Jarid1b leads to LSC differentiation, reducing leukaemia stem cell oncogenic potential.15 While these studies provide insight into the role of H3K4me3 in cell fate decisions and that of Jarid1b in regulating the differentiation of a variety of cell types, it is unclear how Jarid1b contributes to stratified epithelium differentiation.