14-3-3 sigma was identified as an epithelial cell marker. It is part of the 14-3-3 family of proteins in which seven isoforms have been identified: beta, zeta, gamma, eta, epsilon, tau, and sigma. 14-3-3 proteins function as adaptors that bind with a number of partners to mediate various signaling pathways. 14-3-3 sigma is also called stratifin or HME1 and appears to function as a tumor suppressor whose expression can be downregulated via methylation. Loss of 14-3-3 sigma expression results in a defective G2/M phase checkpoint and appears to contribute to both epithelial and non-epithelial tumorigenesis.