ZEB1 and cancer: ZEB1 is an essential EMT transcriptional activator and mediator of tumor radioresistance and chemoresistance.9, 10, 11, 12 Aberrant expression of ZEB1 has been documented in multiple cancers.13 Recently, the regulation of ZEB1 protein turnover has come into focus with the discovery of SIAH1/2 E3 ligases and Skp1-Pam-FBXO45 atypical ubiquitin E3 ligase complex as regulators of ZEB1 ubiquitination and degradation.14, 15