14-3-3 sigma is a member of a highly conserved family of 14-3-3 proteins that are present in all eukaryotic organisms. There are 7 known human 14-3-3 isotypes and they play important roles in many biological activities by binding to and altering the subcellular localization and/or stability of key molecules in various signaling cascades. 14-3-3 sigma was originally characterized as a human mammary epithelium marker 1 and later rediscovered as an important molecule for cell cycle checkpoint regulation. Recently it has been reported that 14-3-3 sigma may serve as a prognosis marker predicting survival of pancreatic cancer patient treatment. 14-3-3 is the only 14-3-3 isoform induced by the tumor suppressor protein p53, in response to -irradiation and other DNA-damaging agents. 14-3-3 is a p53-regulated inhibitor of G2/M progression and acts as a tumor suppressor gene that is inactivated by methylation of its 5' CpG islands in epithelial tumor cells. Two isoforms of the human proteins are produced by alternative splicing.