ABSTRACT
High-mobility group box 1 (HMGB1) is a non-histone nuclear protein in most eukaryocytes. Inside the nucleus, HMGB1 plays an important role in several DNA events such as DNA repair, transcription, telomere maintenance, and genome stability. While outside the nucleus, it fulfils more complicated functions, including promoting cell proliferation, inflammation, angiogenesis, immune tolerance and immune escape, which may play a pro-tumoral role.Meanwhile, HMGB1 acts as an anti-tumoral protein by regulating immune cell recruitment and inducing immunogenic cell death (ICD) during the carcinogenesis process. Therefore, abnormal expression of HMGB1 is associated with oncogenesis, development, and metastasis of cancer, which may play a dual role of pro-tumor and anti-tumor.
Subject(s)
Humans , Carcinogenesis , Cell Proliferation , HMGB1 Protein/metabolism , Neoplasms/pathology , Neovascularization, PathologicABSTRACT
Objective: Pancreatic ductal adenocarcinoma (PDAC) is one of the most malignant digestive tract tumors with a poor prognosis and high recurrence rate. Recently, ferroptosis resistance has been found in PDAC. However, the underlying mechanism of ferroptosis resistance has not been fully elucidated. Cytochrome P4502J2 (CYP2J2) is the main enzyme which mediates arachidonic acid to produce epoxyeicosatrienoic acids (EETs) in human tissues. It has been reported that EETs involve in the development of cancer, while the roles of EETs in PDAC and ferroptosis remain unclear. This study aims to explore the effect of CYP2J2/EETs on ferroptosis of human pancreatic ductal adenocarcinoma cells PANC-1 cells and the underlying mechanisms.Methods: The tumor tissues and para-carcinoma tissues of 9 patients with PDAC were collected and the expression of CYP2J2 was detected with real-time PCR and Western blotting. Enzyme-linked immunosorbent assay (ELISA) was used to detect the level of 8,9-dihydroxyeicosatrienoic acid (8,9-DHET), and the degradation product of 8,9-epoxyeicosa-trienoic acid (8, 9-EET). PANC-1 cells were used in this study. The ferroptosis inducer erastin was used to induce ferroptosis. The intracellular long-chain acyl-CoA synthetase 4 (ACSL4) protein level, lactate dehydrogenase (LDH) activity, malondialdehyde (MDA) content, Fe2+concentration, and cell survival were detected. The 8, 9-EET was pretreated to observe its effect on erastin-induced ferroptosis in PANC-1 cells. Lentivirus was used to construct a CYP2J2 knockdown cell line to observe its effect on the ferroptosis of PANC-1 cells induced by erastin. A peroxisome proliferation-activated receptor γ (PPARγ) blocker was used to observe the effect of 8, 9-EET on erastin-induced glutathione peroxidase 4 (GPX4) and MDA content in PANC-1 cells.Results: High expression of CYP2J2 was found in PDAC, accompanied by an increased level of 8, 9-DHET. The 8, 9-EET pretreatment significantly attenuated the PANC-1 cell death induced by erastin. The 8, 9-EET reduced the Fe2+ concentration, LDH activity and MDA content, and ACSL4 protein expression in erastin-treated PANC-1 cells. The 8,9-EET also restored the ferroportin (FPN) and ferroptosis suppressor protein 1 (FSP1) mRNA expressions in erastin-treated PANC-1 cells. But CYP2J2 knockdown exacerbated the erastin-induced ferroptosis in PANC-1 cells. Besides, CYP2J2 knockdown furtherly down-regulated the gene expression of FPN and FSP1. The 8, 9-EET increased the expression of GPX4 in the erastin-treated PANC-1 cells, which was eliminated by a PPARγ blocker GW9662. And GW9662 abolished the anti-ferroptosis effects of 8,9-EET. Conclusion: CYP2J2/EETs are highly expressed in PDAC tissues. EETs inhibit the ferroptosis via up-regulation of GPX4 in a PPARγ-dependent manner, which contributes to the ferroptosis resistance of PDAC.