Abstract 4319: HSF1 inhibition induces pancreatic ductal adenocarcinoma autophagy through JNK

Abstract Background: Pancreatic ductal adenocarcinoma (PDAC) is the third leading cause of cancer-related mortality, with a 5-year survival rate of 12%. Chemoresistance due to autophagy, a natural process of proteotoxic stress response, is the most common chemotherapy challenge for pancreatic cancer. Autophagy, which maintains cellular homeostasis by removing damaged or unnecessary proteins and organelles, is a self-degradation process regulated by the mammalian target of rapamycin complex (mTORC1). Excessive levels of autophagy can be detrimental and lead to cell death. Nevertheless, this dual function of autophagy in regulating pancreatic cancer remains poorly understood. It has been reported that heat shock factor 1 (HSF1), a critical pro-oncogenic transcription factor in the proteotoxic stress response, inhibits c-Jun N-terminal kinase 1/2 (JNK1/2) signaling pathway to maintain mTORC1 activity and control cell size. HSF1 is highly expressed in pancreatic tumors, and inhibition of HSF1 via small molecules enhances the chemotherapy drug effect on PDAC programmed cell death. However, the PDAC autophagy response in HSF1 inhibition is currently not fully understood. Objective: The objective of this study is to investigate the molecular mechanism of HSF1 inhibition in PDAC autophagy. Methods and Results: In human PDAC cells, Western blotting analysis revealed that HSF1 inhibition via small molecular including CCT361814/NXP800, an HSF1 inhibitor in phase I clinical trials, increased autophagy marker microtubule-associated protein 1A/1B-light chain 3 (LC3) lipidation and decreased expression of phosphorylation of HSF1 at Ser326 and total HSF1 protein, conversely using HSF1 overexpression model reversed this effect. Inhibition of autophagy via 3-methyladenine reversed HSF1 inhibition-induced autophagy. Results from transmission electron microscopy and GFP-LC3 reporter revealed that HSF1 inhibition induced autophagosome formation and accumulation. Furthermore, HSF1 inhibition induced phosphorylation of JNK1/2 at Thr183/Tyr185 and decreased mTORC1 activity, while knockdown JNK1/2 diminished HSF1 inhibition-induced LC3 lipidation. The combination of chemotherapy drugs with HSF1 inhibitors decreased PDAC cell viability. Additionally, blocking autophagy increased HSF1 inhibition-induced apoptosis. Conclusions: In conclusion, JNK1/2 is involved in HSF1 inhibition-induced PDAC autophagy, targeting autophagy could unveil a novel treatment strategy for pancreatic cancer through targeted HSF1 inhibition. Citation Format: Shruti Ghai, Alex Young, Kuo-Hui Su. HSF1 inhibition induces pancreatic ductal adenocarcinoma autophagy through JNK 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 4319.