PPAR? Activation By Fenofibrate Enhances The Radiosensitivity Of Human Pancreatic Cancer Cells In Vitro And In Vivo

Objective: Radiotherapy plays a significant role in the management of pancreatic cancer.Enhancing the radiation sensitivity of pancreatic cells will be beneficial for the treatment of pancreatic cancer patients.Fenofibrate is a specific ligand for nuclear receptor peroxisome proliferator-activated receptor alpha(PPAR?),which is involved in multiple pathophysiological processes.This study aims to investigate the expression level of PPAR? in pancreatic cancer and the radiosensitivity effect of PPAR? activation fenofibrate on human pancreatic cancer cells and its underlying mechanisms.Methods: 80 pancreatic cancer tissue samples were collected.The expression of PPAR? in pancreatic cancer tissues were performed by immunohistochemistry.Pancreatic cancer cells PANC1 and Patu8988 were treated with fenofibrate and/or IR(radiation),and the cell viability was detected by MTT assay.Radiosensitivity of cells was determined using colony formation assay.The migration ability was detected by scratch migration assay.The invasion ability was detected by transwell assay.The nude mice were subcutaneous implantated with human pancreatic cancer PANC1 cells.Then,the nude mice were treated with fenofibrate and/or IR.The tumor growth was measured every three days.After PANC1 cells were treated with fenofibrate,immunofluorescence staining were performed to detect thedistribution of PPAR?.mRNA microarray was used to explore the involved genes.The intracellular Zn2+ accumulation was detected by Zn2+ fluorescent probe.Results: The expression of PPAR? was significantly higher in pancreatic cancer tissues,compared with the para-tissues tissues(P < 0.01).The expression of PPAR? was correlated with the TNM stage(P < 0.01).PPAR? agonist fenofibrate inhibited the proliferation of human pancreatic cell lines(PANC1 and Patu8988)in a dose-dependent manner.Pretreatment of 50 ?M fenofibrate in PANC1 and Patu8988 cells potentiated the anticancer effect of radiation.In addition,pretreatment of fenofibrate combined with radiation significantly suppressed cell migration and invasion abilities in pancreatic cancer cell lines.Moreover,fenofibrate sensitized PANC1 xenografts to irradiation with an enhancement factor 2.10(P < 0.05).Microarray analysis revealed that fenofibrate plus radiation affected 2669 genes(Fold-change > 2.0),including TAOK2,JAK3,SLC39A7(ZIP7)and TRPV1.Pathway analysis demonstrated that fenofibrate affected multiple pathways,including cytokine-cytokine receptor interaction,RIG-I-like receptor signaling pathway and transcriptional misregulation in cancer.Taken together,these results suggest that fenofibrate enhances the radiosensitivity of human pancreatic cancer cells in vitro and in vivo.Specifically,we focused on ZIP7,which was decreased by fenofibrate.Knock-down of ZIP7 decreased Zn2+ accumulation in pancreatic cancer cells.Consistently,pretreatment of fenofibrate combined with radiation significantly suppressed zinc aggregation in PANC1 cell,which is likely to induce cell death due to lack of zinc.Finally,we found that the expression of ZIP7 was significantly increased in pancreatic cancer tissues,compared with the para-tissues tissues.Conclusions: The expression level of PPAR? is increased in pancreatic cancer.PPAR? agonist fenofibrate increases the radiosensitivity of human pancreatic cancer cells.Fenofibrate plus radiation affected multiple genes that implicated in multiple pathways.Fenofibrate can inhibit the expression of ZIP7,decreasing zinc aggregation in cytoplasm.