Inhibitors of ERp44, PDIA1, and AGR2 induce disulfide-mediated oligomerization of Death Receptors 4 and 5 and cancer cell death

Breast cancer mortality remains unacceptably high, indicating a need for safer and more effective therapeutic agents. Disulfide bond Disrupting Agents (DDAs) were previously identified as a novel class of anticancer compounds that selectively kill cancers that overexpress the Epidermal Growth Factor Receptor (EGFR) or its family member HER2. DDAs kill EGFR+ and HER2+ cancer cells via the parallel downregulation of EGFR, HER2, and HER3 and activation/oligomerization of Death Receptors 4 and 5 (DR4/5). However, the mechanisms by which DDAs mediate these effects are unknown. Affinity purification analyses employing biotinylated-DDAs reveal that the Protein Disulfide Isomerase (PDI) family members AGR2, PDIA1, and ERp44 are DDA target proteins. Further analyses demonstrate that shRNA-mediated knockdown of AGR2 and ERp44, or expression of ERp44 mutants, enhance basal DR5 oligomerization. DDA treatment of breast cancer cells disrupts PDIA1 and ERp44 mixed disulfide bonds with their client proteins. Together, the results herein reveal DDAs as the first small molecule, active site inhibitors of AGR2 and ERp44, and demonstrate roles for AGR2 and ERp44 in regulating the activity, stability, and localization of DR4 and DR5, and activation of Caspase 8.

Automated summary

Breast cancer mortality remains high, and there is a need for safer and more effective treatments. Disulfide bond Disrupting Agents (DDAs) have been identified as a potential class of anticancer compounds that specifically target EGFR and HER2 overexpressing cancer cells. The study found that DDAs act by downregulating EGFR, HER2, and HER3 and activating Death Receptors 4 and 5 (DR4/5). Further analysis revealed that AGR2, PDIA1, and ERp44 are the target proteins of DDAs. DDAs disrupt the mixed disulfide bonds between PDIA1, ERp44, and their client proteins, and enhance basal DR5 oligomerization by targeting AGR2 and ERp44.