Death-associated protein kinase-1 expression and autophagy in chronic lymphocytic leukemia are dependent on activating transcription factor-6 and CCAAT/Enhancer-binding protein-β

Abstract

Expression of DAPK1, a critical regulator of autophagy and apoptosis, is lost in a wide variety of tumors, although the mechanisms are unclear. Atranscription factor complex consisting of ATF6 (an endoplasmic reticulum-resident factor) and C/EBP-β is required for the IFN-γ-induced expression of DAPK1. IFN-γ- induced proteolytic processing of ATF6 and phosphorylation of C/EBP-β are obligatory for the formation of this transcriptional complex. We report that defects in this pathway fail to control growth of chronic lymphocytic leukemia (CLL). Consistent with these observations, IFN-γ and chemotherapeutics failed to activate autophagy in CLL patient samples lacking ATF6 and/or C/EBP-β. Together, these results identify a molecular basis for the loss of DAPK1 expression in CLL.