FOS and neoplasm: Many activities of important tumor suppressors and oncoproteins are regulated by sumo including PML, WRN, BLM, c-JUN, c-FOS, TP53 and MDM259, 60, 61, 62, 63 and of several nuclear hormone receptors including estrogen receptor alpha (ERa), progesterone receptor (PR) and AR64, which play a central role in the development of hormone drive breast tumors65, are modified by SUMO in a ligand-dependent manner.