We found that JMJD2A correlates with breast cancer progression and promotes breast cancer progression through transcriptional silencing of ARHI. The repression of ARHI expression by JMJD2A required the involvements of E2Fs and HDACs, and the aggressive behavior of JMJD2A could be reversed by re-expression of ARHI both in vitro and in vivo. The gene discussed is KDM4A; the disease is breast cancer.