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Background Triptolide (TPL) can enhance the sensitivity of pancreatic cancer cells to tumor necrosis factor-related apoptosis-inducing ligand (TRAIL), but available research is limited to whether TPL can affect the relevant downstream signaling pathways of TRAIL. Current knowledge is far from adequate to fully understand the mechanisms by which TPL increases TRAIL sensitivity of pancreatic cancer. Purpose We aimed to find TPL-regulated upstream components of the signaling pathways of TRAIL to further understand the regulatory mechanism by which TPL increases the sensitivity to TRAIL. Methods Microarray analysis and the adherent cell cytometry system Celigo were used to identify the TRAIL-related genes. Western blot analysis, cell proliferation assays, tumorigenicity assays in nude mice, flow cytometry, and transmission electron microscopy were performed to analyze the function of Pumilio RNA-binding family member 1 (PUM1) in TPL-mediated enhancement of sensitivity to TRAIL. The effect of PUM1 silencing on the p27–CDK2 complex was examined by immunoprecipitation. Results PUM1 expression was decreased by TPL and TPL + TRAIL but was not decreased by TRAIL alone. PUM1 silencing enhanced low-concentration-TRAIL-induced suppression of proliferation and promotion of apoptosis and increased p27 expression and the amount of the p27–CDK2 complex in pancreatic cancer cells. PUM1 overexpression attenuated the effects of TPL treatment (TRAIL-induced cell proliferation suppression and apoptosis promotion), while PUM1 silencing and TPL enhanced low-concentration-TRAIL-induced autophagy activation in pancreatic cancer cells. Moreover, PUM1 overexpression attenuated the effect of TPL treatment on TRAIL-induced autophagy activation in pancreatic cancer cells. Conclusion PUM1 silencing increased the sensitivity of pancreatic cancer cells to TRAIL in vivo and in vitro, indicating that PUM1 may be a new target for increasing the sensitivity of cancer cells to TRAIL. In addition, our results indicate that TPL enhances TRAIL sensitivity of pancreatic cancer cells by activating autophagy via downregulation of PUM1. This novel concept may have significant implications for the development of new strategies to enhance TRAIL sensitivity of tumors.

ObjectiveHyperbaric oxygen (HBO) preconditioning (HBO-PC) has been testified to have protective effects on spinal cord injury (SCI). However, the mechanisms remain enigmatic. The present study aimed to explore the effects of HBO-PC on primary rat spinal neurons against oxidative injury and oxygen-glucose deprivation (OGD) and the relationship with heat shock proteins (HSPs).MethodsPrimary rat spinal neurons after 7 days of culture were used in this study. HSPs were detected in rat spinal neurons following a single exposure to HBO at different time points by Western blot. Using lactate dehydrogenase release assay and cell counting kit-8 assay, the injuries induced by hydrogen peroxide (H2O2) insult or OGD were determined and compared among neurons treated with HBO-PC with or without HSP inhibitors.ResultsThe results of Western blot showed that HSP27, HSP70 and HSP90 have a slight but not significant increase in primary neurons following HBO exposure. However, HSP32 expression significantly increased and reached highest at 12 h following HBO exposure. HBO-PC significantly increased the cell viability and decreased the medium lactate dehydrogenase content in cultures treated with H2O2 or OGD. Pretreatment with zinc protoporphyrin IX, a specific inhibitor of HSP32, significantly blocked the protective effects of HBO-PC.ConclusionsThese results suggest that HBO-PC could protect rat spinal neurons in vitro against oxidative injury and OGD mostly by up-regulating of HSP32 expression.