title: Unfolded Protein Response in Cancer: IRE1α Inhibition by Selective Kinase Ligands Does Not Impair Tumor Cell Viability.
abstract: The kinase/endonuclease inositol requiring enzyme 1 (IRE1α), 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 IRE1α 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 IRE1α endonuclease as well as cellular IRE1α. The first X-ray crystal structure of a kinase inhibitor (16) bound to hIRE1α was obtained. Screening of native tumor cell lines (>300) against selective IRE1α inhibitors failed to demonstrate any effect on cellular viability. These results suggest that IRE1α 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.
authors.affiliation: Departments of Medicinal Chemistry, Molecular Structure, and Oncology, Amgen, Inc. , One Amgen Center Drive, Thousand Oaks, California 93012, United States.
authors.forename: Paul E
authors.initials: PE
authors.lastname: Harrington
authors.affiliation: Departments of Medicinal Chemistry, Molecular Structure, and Oncology, Amgen, Inc. , One Amgen Center Drive, Thousand Oaks, California 93012, United States.
authors.forename: Kaustav
authors.initials: K
authors.lastname: Biswas
authors.affiliation: Departments of Medicinal Chemistry, Molecular Structure, and Oncology, Amgen, Inc. , One Amgen Center Drive, Thousand Oaks, California 93012, United States.
authors.forename: David
authors.initials: D
authors.lastname: Malwitz
authors.affiliation: Departments of Medicinal Chemistry, Molecular Structure, and Oncology, Amgen, Inc. , One Amgen Center Drive, Thousand Oaks, California 93012, United States.
authors.forename: Andrew S
authors.initials: AS
authors.lastname: Tasker
authors.affiliation: Departments of Medicinal Chemistry, Molecular Structure, and Oncology, Amgen, Inc. , One Amgen Center Drive, Thousand Oaks, California 93012, United States.
authors.forename: Christopher
authors.initials: C
authors.lastname: Mohr
authors.affiliation: Departments of Medicinal Chemistry, Molecular Structure, and Oncology, Amgen, Inc. , One Amgen Center Drive, Thousand Oaks, California 93012, United States.
authors.forename: Kristin L
authors.initials: KL
authors.lastname: Andrews
authors.affiliation: Departments of Medicinal Chemistry, Molecular Structure, and Oncology, Amgen, Inc. , One Amgen Center Drive, Thousand Oaks, California 93012, United States.
authors.forename: Ken
authors.initials: K
authors.lastname: Dellamaggiore
authors.affiliation: Departments of Medicinal Chemistry, Molecular Structure, and Oncology, Amgen, Inc. , One Amgen Center Drive, Thousand Oaks, California 93012, United States.
authors.forename: Richard
authors.initials: R
authors.lastname: Kendall
authors.affiliation: Department of Discovery Technologies, Amgen Research GmbH , Josef-Engert-Str. 11, 93050 Regensburg, Germany.
authors.forename: Holger
authors.initials: H
authors.lastname: Beckmann
authors.affiliation: Department of Discovery Technologies, Amgen Research GmbH , Josef-Engert-Str. 11, 93050 Regensburg, Germany.
authors.forename: Peter
authors.initials: P
authors.lastname: Jaeckel
authors.affiliation: Department of Discovery Technologies, Amgen Research GmbH , Josef-Engert-Str. 11, 93050 Regensburg, Germany.
authors.forename: Silvia
authors.initials: S
authors.lastname: Materna-Reichelt
authors.affiliation: Departments of Medicinal Chemistry, Molecular Structure, and Oncology, Amgen, Inc. , One Amgen Center Drive, Thousand Oaks, California 93012, United States.
authors.forename: Jennifer R
authors.initials: JR
authors.lastname: Allen
authors.affiliation: Departments of Medicinal Chemistry, Molecular Structure, and Oncology, Amgen, Inc. , One Amgen Center Drive, Thousand Oaks, California 93012, United States.
authors.forename: J Russell
authors.initials: JR
authors.lastname: Lipford
keywords: IRE1α; Unfolded protein response; inhibitor; kinase