Abstract 380: Co-downregulation of GRP78 and ATR enhances apoptosis in pancreatic ductal adenocarcinoma

Abstract Background: Targeting endoplasmic reticulum (ER) stress is a potential therapeutic strategy in preclinical models of pancreatic duct adenocarcinoma (PDAC). GRP78 is known as the master regulator of the unfolded protein response (UPR) pathway, regulating ER stress by activating the UPR pathway to avoid cell apoptosis and regulates the activation of UPR pathway signals by binding PERK. Overexpression of GRP78 in PDAC results in the retention of misfolded and unassembled proteins, as well as the accumulation of ROS, leading to the promotion of genomic instability. However, there has been limited research on targeting GRP78 as a therapeutic strategy in PDAC. In this study, we aimed to investigate the anticancer effects of BOLD-100, an inhibitor of GRP78, in PDAC. Methods: We used 9 PDAC cell lines (Capan-1, AsPC-1, HPAFII, MIA-PaCa2, Panc-1, Capan-2, SNU-213, SNU-324, SNU-2918). The mouse xenograft model of Capan-1 was established for in vivo study. BOLD-100 (GRP78 inhibitor), AZD6738 (ATR inhibitor), NAC (N-Acetylcysteine; ROS scavenger) and TUDCA (Tauroursodeoxycholic acid; ER stress inhibitor) were used. MTT assay, CFA assay, cell cycle analysis, RT-PCR, western blot, immunoprecipitation, DCF-DA staining and Annexin V assay were used to elucidate the action of BOLD-100. The combination of BOLD-100 with AZD6738 has been evaluated in both in vitro and in vivo model. Results: BOLD-100 suppressed the proliferation of PDAC cells and decreased the mRNA level of GRP78, which in turn disrupted the interaction between GRP78 and PERK. BOLD-100 increased ER stress and ROS, leading to activation of PERK, eIF2a, and CHOP. Activation of UPR pathway induced CHOP-dependent apoptosis and inhibited PDAC cell growth. Moreover, TUDCA reversed the ROS accumulation induced by BOLD-100, confirming that ER stress regulates ROS levels. The accumulation of ROS upregulated the active forms of ATR and CHK1, suggesting the activation of the DNA damage repair pathway. Notably, the treatment of NAC abrogated the activation of ATR-CHK1 axis by BOLD-100-induced ROS accumulation. AZD6738 synergized with BOLD-100 in in vitro and in vivo, by suppressing BOLD-100-induced ATR phosphorylation. Conclusion: GRP78 could serve as one of the potential therapeutic targets in PDAC. The combination of BOLD-100 and AZD6738 demonstrates a synergistic effect suggesting GRP78/ATR dual targeting as a promising therapeutic option for patients with PDAC. Citation Format: Su In Lee, Ah-Rong Nam, Kyoung-Seok Oh, Jae-Min Kim, Ju-Hee Bang, Yoojin Jeong, Sea Young Choo, Hyo Jung Kim, Jeesun Yoon, Tae-Yong Kim, Do-Youn Oh. Co-downregulation of GRP78 and ATR enhances apoptosis in pancreatic ductal adenocarcinoma abstract. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts) ; 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84 (6Suppl): Abstract nr 380.