Unfolded Protein Response in Cancer: IRE1α Inhibition by Selective Kinase Ligands Does Not Impair Tumor Cell...

Area of Science:

• Biochemistry
• Molecular Biology
• Oncology

Background:

• The unfolded protein response (UPR) is triggered by endoplasmic reticulum stress.
• Inositol requiring enzyme 1-alpha (IRE1α) is a key sensor in the UPR pathway.
• IRE1α has been explored as a potential anticancer target due to its role in cell survival.

Purpose of the Study:

• To identify and characterize novel allosteric inhibitors of IRE1α endonuclease activity.
• To evaluate the efficacy of IRE1α inhibition in cancer cell viability.
• To assess the therapeutic potential of targeting IRE1α in cancer treatment.

Main Methods:

• Structure-activity relationship (SAR) studies were conducted to optimize IRE1α inhibitors.
• Inhibitor potency was assessed against recombinant and cellular IRE1α.
• X-ray crystallography was used to determine the structure of an inhibitor bound to IRE1α.
• High-throughput screening of over 300 native tumor cell lines was performed.

Main Results:

• Potent allosteric inhibitors (compounds 16 and 18) targeting IRE1α were identified.
• Inhibitors demonstrated selectivity in kinase screens and potent activity against IRE1α.
• The first X-ray crystal structure of an IRE1α kinase inhibitor complex was obtained.
• No significant effect on the viability of tested tumor cell lines was observed with selective IRE1α inhibitors.

Conclusions:

• IRE1α activity is not essential for the in vitro viability of most tumor cell lines.
• Targeting IRE1α and its survival functions within the UPR may not be a viable strategy for blocking tumorigenesis.
• Further research is needed to explore alternative therapeutic targets for cancer treatment.