The KDM5 subfamily (also known as JARID1 subfamily) consists of four members, KDM5A (JARID1A), KDM5B (JARID1B), KDM5C (JARID1C) and KDM5D (JARID1D) whose deregulation in various kinds of cancer has been widely documented to contribute significantly to tumor initiation and progression [12,13,14,15,16]. The gene discussed is KDM5D; the disease is cancer.