Pancreatic cancer is the fourth leading cause of cancer‐related death in the United States. Reactive oxygen species (ROS) are generally increased in pancreatic cancer cells compared with normal cells. ROS plays a vital role in various cellular biological activities including proliferation, growth, apoptosis, and invasion. Besides, ROS participates in tumor microenvironment orchestration. The role of ROS is a doubled‐edged sword in pancreatic cancer. The dual roles of ROS depend on the concentration. ROS facilitates carcinogenesis and cancer progression with mild‐to‐moderate elevated levels, while excessive ROS damages cancer cells dramatically and leads to cell death. Based on the recent knowledge, either promoting ROS generation to increase the concentration of ROS with extremely high levels or enhancing ROS scavenging ability to decrease ROS levels may benefit the treatment of pancreatic cancer. However, when faced with oxidative stress, the antioxidant programs of cancer cells have been activated to help cancer cells to survive in the adverse condition. Furthermore, ROS signaling and antioxidant programs play the vital roles in the progression of pancreatic cancer and in the response to cancer treatment. Eventually, it may be the novel target for various strategies and drugs to modulate ROS levels in pancreatic cancer therapy.

Diabetes mellitus (DM) and pancreatic cancer are intimately related, as approximately 85% of patients diagnosed with pancreatic cancer have impaired glucose tolerance or even DM. Our previous studies have indicated that high glucose could promote the invasive and migratory abilities of pancreatic cancer cells. We therefore explored the underlying mechanism that hyperglycemia modulates the metastatic potential of pancreatic cancer. Our data showed that streptozotocin‐ (STZ‐) treated diabetic nude mice exhibit larger tumor size than that of the euglycemic mice. The number of nude mice that develop liver metastasis or ascites is much more in the STZ‐treated group than that in the euglycemic group. Hyperglycemic mice contain a higher plasma H₂O₂‐level than that from euglycemic mice. The injection of polyethylene glycol‐conjugated catalase (PEG‐CAT), an H₂O₂ scavenger, may reverse hyperglycemia‐induced tumor metastasis. In addition, hyperglycemia could also modulate the expression of epithelial‐mesenchymal transition‐ (EMT‐) related factors in pancreatic tumor tissues, as the E‐cadherin level is decreased and the expression of mesenchymal markers N‐cadherin and vimentin as well as transcription factor snail is strongly increased. The injection of PEG‐CAT could also reverse hyperglycemia‐induced EMT. These results suggest that the association between hyperglycemia and poor prognosis of pancreatic cancer can be attributed to the alterations of EMT through the production of hydrogen peroxide.

Nrf2 (NF‐E2‐related factor 2) pathway and autophagy both can respond to oxidative stress to promote cancer cells to survive in the tumor microenvironment. We, therefore, explored the relevance between Nrf2 pathway and autophagy in pancreatic cancer cells upon stimulation of reactive oxygen species (ROS). Pancreatic cancer cells were cultured under controlled ROS stressing condition or basal condition. Different inhibitors were used to prevent autophagy at particular stages. Nrf2 siRNA was used to inhibit Nrf2 pathway activation. Ad‐mRFP‐GFP‐LC3 infection was used to monitor autophagic flux. The result shows that a small amount of exogenous hydrogen peroxide (H₂O₂) can significantly improve the level of intracellular ROS. Moreover, our findings indicate that ROS promotes the activation of both Nrf2 pathway and autophagy in pancreatic cancer cells. Moreover, our data demonstrate that suppression of autophagic activity at particular stages results in an increased promotion of Nrf2 pathway activation upon ROS stimulation. Furthermore, we found that silencing of Nrf2 promotes autophagy upon ROS stimulation. In addition, Nrf2 interference effectively promotes autophagic flux upon ROS stimulation. In summary, our findings suggest that Nrf2 pathway and autophagy have a negative interaction with each other upon ROS stimulation.

Ferroptosis is a new type of programmed cell death, which has been involved in the progression of tumours. However, the regulatory network of ferroptosis in pancreatic cancer is still largely unknown. Here, using datasets from GEO and TCGA, we screened HSPB1, related to the P450 monooxygenase signalling, a fuel of ferroptosis, to be a candidate gene for regulating pancreatic cancer cell ferroptosis. We found that HSPB1 was enriched in the exosomes derived from human pancreatic cancer cell lines SW1990 and Panc‐1. Then, hypoxic SW1990 cells were incubated with exosomes alone or together with HSPB1 siRNA (si‐HSPB1), and we observed that exosomes promoted cell proliferation and invasion and suppressed ferroptosis, which was reversed by si‐HSPB1. Moreover, we found a potential binding affinity between HSPB1 and FUS, verified their protein interaction by using dual‐colour fluorescence colocalization and co‐IP assays, and demonstrated the promoting effect of FUS on oxidative stress and ferroptosis in hypoxic SW1990 cells. Subsequently, FUS was demonstrated to bind with and stabilize the mRNA of Nrf2, a famous anti‐ferroptosis gene that negatively regulates the level of P450. Furthermore, overexpressing FUS and activating the Nrf2/HO‐1 pathway (using NK‐252) both reversed the inhibitory effect of si‐HSPB1 on exosome functions. Finally, our in vivo studies showed that exosome administration promote tumour growth in nude mice of xenotransplantation, which was able to be eliminated by knockdown of HSPB1. In conclusion, exosomal HSPB1 interacts with the RNA binding protein FUS and decreases FUS‐mediated stability of Nrf2 mRNA, thus suppressing hypoxia‐induced ferroptosis in pancreatic cancer.

Ferroptosis plays a crucial role in inhibiting tumor progression. La Ribonucleoprotein 4B (LARP4B) is known to function as a pro-oncogenic factor in digestive tumors, but its specific role and potential mechanisms remain unclear in pancreatic cancer (PC). In this study, we found that LARP4B was upregulated in PC tissues and cells. Overexpression of LARP4B promoted PC cell proliferation and invasion, while knockdown of LARP4B inhibited PC cell proliferation and invasion. Furthermore, knockdown of LARP4B was associated with intracellular iron overload, increased levels of reactive oxygen species (ROS) and malondialdehyde (MDA), and decreased glutathione (GSH) content and superoxide dismutase (SOD) activity in PC cells. Mechanistically, LARP4B binds to mRNA of with-no-lysine kinase 1 (WNK1) and promotes its stability, and WNK1 competitively binds to the partial Kelch domain of Kelch-like ECH-associated protein 1 (Keap1) to promote the nuclear translocation of nuclear factor erythroid-2-related factor 2 (NRF2), thereby activating the NRF2/GCH1/BH4 pathway and inhibiting ferroptosis in PC cells. ML385, a NRF2 nuclear translocation inhibitor, partially rescued the inhibitory effect of WNK1 on ferroptosis in PC cells. Finally, in vivo experiments showed that knockdown of LARP4B suppressed tumor growth in PC xenograft mice. In conclusion, our study demonstrated that LARP4B inhibited ferroptosis by activating the WNK1-mediated NRF2/GCH1/BH4 pathway, thereby promoting PC progression. Insight Box This work provides evidence for LARP4B as a pro-oncogenic factor in pancreatic cancer, while also offers new insights into the further understanding of the biological functions of LARP4B and the oncological mechanisms of pancreatic cancer. We found that LARP4B is upregulated in PC tissues and cells, and its overexpression promotes the proliferation and invasion of PC cells. Additionally, we discovered that LARP4B binds to WNK1 mRNA and enhances its stability. WNK1 competitively binds to Keap1 to facilitate NRF2 nuclear translocation, thereby activating the NRF2/GCH1/BH4 pathway and inhibiting ferroptosis in PC cells. These findings provide significant insights for further research on PC and the development of therapeutic strategies.