Unfolded Protein Response in Cancer: IRE1? Inhibition by Selective Kinase Ligands Does Not Impair Tumor Cell Viability.

ABSTRACT: The kinase/endonuclease inositol requiring enzyme 1 (IRE1?), one of the sensors of unfolded protein accumulation in the endoplasmic reticulum that triggers the unfolded protein response (UPR), has been investigated as an anticancer target. We identified potent allosteric inhibitors of IRE1? endonuclease activity that bound to the kinase site on the enzyme. Structure-activity relationship (SAR) studies led to 16 and 18, which were selective in kinase screens and were potent against recombinant IRE1? endonuclease as well as cellular IRE1?. The first X-ray crystal structure of a kinase inhibitor (16) bound to hIRE1? was obtained. Screening of native tumor cell lines (>300) against selective IRE1? inhibitors failed to demonstrate any effect on cellular viability. These results suggest that IRE1? activity is not essential for viability in most tumor cell lines, in vitro, and that interfering with the survival functions of the UPR may not be an effective strategy to block tumorigenesis.

SUBMITTER: Harrington PE 

PROVIDER: S-EPMC4291719 | biostudies-literature | 2015 Jan

REPOSITORIES: biostudies-literature