14-3-3σ, the double-edged sword of human cancers

14-3-3σ is a member of a highly conserved family of 14-3-3 proteins that are present in all eukaryotic organisms. 14-3-3σ has been considered as a tumor suppressor with reduced expression in some human cancers while its increased expression causes resistance to anticancer agents and radiation that cause DNA damages. The increased expression of 14-3-3σ may also predict poor prognosis in some human cancers. Thus, 14-3-3σ may play an important role as a double-edged sword in human cancers, which may attribute to its property as a molecular chaperone by binding to various protein ligands important to many cellular processes such as cell cycle checkpoint regulation and apoptosis in response to DNA damages. In this article, we will review recent studies and progresses in understanding 14-3-3σ as a double-edged sword in human cancers.