title: Prostaglandin E2 promotes the cell growth and invasive ability of hepatocellular carcinoma cells by upregulating c-Myc expression via EP4 receptor and the PKA signaling pathway.
abstract: Hepatocellular carcinoma (HCC) represents a major health problem worldwide. Prostaglandin E2 (PGE2), the predominant product of cyclooxygenase-2, has been implicated in hepatocarcinogenesis. However, the underlying molecular mechanisms remain to be further elucidated. c-myc, a cellular proto-oncogene, is activated or overexpressed in many types of human cancer, including HCC. The present study was designed to investigate the internal relationship and molecular mechanisms between PGE2 and c-Myc in HCC, and to define its role in HCC cell growth and invasion. Our results showed that PGE2 significantly upregulated c-Myc expression at both the mRNA and protein levels, and knockdown of c-Myc blocked PGE2-induced HCC cell growth and invasive ability in human HCC Huh-7 cells. The effect of PGE2 on c-Myc expression was mainly through the EP4 receptor, and EP4 receptor-mediated c-Myc protein upregulation largely depended on de novo biosynthesis of c-Myc mRNA and its protein. EP4 receptor signaling activated GS/AC and increased the intracellular cAMP level in Huh-7 cells. The adenylate cyclase (AC) activator forskolin mimicked the effects of the EP4 receptor agonist on c-Myc expression, while the AC inhibitor SQ22536 reduced EP4 receptor-mediated c-Myc upregulation. These data confirm the involvement of the GS/AC/cAMP pathway in EP4 receptor-mediated c-Myc upregulation. Moreover, the phosphorylation levels of CREB protein were markedly elevated by EP4 receptor signaling, and by using specific inhibitor and siRNA interference, we demonstrated that PKA/CREB was also involved in the EP4 receptor-mediated c-Myc upregulation. In summary, the present study revealed that PGE2 significantly upregulates c-Myc expression at both mRNA and protein levels through the EP4R/GS/AC/cAMP/PKA/CREB signaling pathway, thus promoting cell growth and invasion in HCC cells. Targeting of the PGE2/EP4R/c-Myc pathway may be a new therapeutic strategy to prevent and cure human HCC.
authors.affiliation: Cancer Center, Department of Pathology, Nanjing Medical University, Nanjing, Jiangsu 210029, P.R. China.
authors.forename: Shukai
authors.initials: S
authors.lastname: Xia
authors.affiliation: Cancer Center, Department of Pathology, Nanjing Medical University, Nanjing, Jiangsu 210029, P.R. China.
authors.forename: Juan
authors.initials: J
authors.lastname: Ma
authors.affiliation: Cancer Center, Department of Pathology, Nanjing Medical University, Nanjing, Jiangsu 210029, P.R. China.
authors.forename: Xiaoming
authors.initials: X
authors.lastname: Bai
authors.affiliation: Cancer Center, Department of Pathology, Nanjing Medical University, Nanjing, Jiangsu 210029, P.R. China.
authors.forename: Hai
authors.initials: H
authors.lastname: Zhang
authors.affiliation: Cancer Center, Department of Pathology, Nanjing Medical University, Nanjing, Jiangsu 210029, P.R. China.
authors.forename: Shanyu
authors.initials: S
authors.lastname: Cheng
authors.affiliation: Cancer Center, Department of Pathology, Nanjing Medical University, Nanjing, Jiangsu 210029, P.R. China.
authors.forename: Min
authors.initials: M
authors.lastname: Zhang
authors.affiliation: Cancer Center, Department of Pathology, Nanjing Medical University, Nanjing, Jiangsu 210029, P.R. China.
authors.forename: Li
authors.initials: L
authors.lastname: Zhang
authors.affiliation: Cancer Center, Department of Pathology, Nanjing Medical University, Nanjing, Jiangsu 210029, P.R. China.
authors.forename: Mingzhan
authors.initials: M
authors.lastname: Du
authors.affiliation: Cancer Center, Department of Pathology, Nanjing Medical University, Nanjing, Jiangsu 210029, P.R. China.
authors.forename: Yipin
authors.initials: Y
authors.lastname: Wang
authors.affiliation: Cancer Center, Department of Pathology, Nanjing Medical University, Nanjing, Jiangsu 210029, P.R. China.
authors.forename: Hai
authors.initials: H
authors.lastname: Li
authors.affiliation: Cancer Center, Department of Pathology, Nanjing Medical University, Nanjing, Jiangsu 210029, P.R. China.
authors.forename: Rong
authors.initials: R
authors.lastname: Rong
authors.affiliation: Cancer Center, Department of Pathology, Nanjing Medical University, Nanjing, Jiangsu 210029, P.R. China.
authors.forename: Feng
authors.initials: F
authors.lastname: Shi
authors.affiliation: Cancer Center, Department of Pathology, Nanjing Medical University, Nanjing, Jiangsu 210029, P.R. China.
authors.forename: Qinyi
authors.initials: Q
authors.lastname: Yang
authors.affiliation: Cancer Center, Department of Pathology, Nanjing Medical University, Nanjing, Jiangsu 210029, P.R. China.
authors.forename: Jing
authors.initials: J
authors.lastname: Leng
mesh_terms: D000262:Adenylyl Cyclases / Q000378:metabolism; D006528:Carcinoma, Hepatocellular / Q000235:genetics* / Q000378:metabolism; D045744:Cell Line, Tumor; D049109:Cell Proliferation; D000242:Cyclic AMP / Q000378:metabolism; D017362:Cyclic AMP Response Element-Binding Protein / Q000378:metabolism; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism; D015232:Dinoprostone / Q000378:metabolism*; D015972:Gene Expression Regulation, Neoplastic; D016259:Genes, myc / Q000235:genetics*; D006801:Humans; D008113:Liver Neoplasms / Q000235:genetics* / Q000378:metabolism; D009361:Neoplasm Invasiveness / Q000235:genetics; D010766:Phosphorylation; D000090063:Proto-Oncogene Mas; D016271:Proto-Oncogene Proteins c-myc / Q000378:metabolism*; D012333:RNA, Messenger / Q000235:genetics*; D058309:Receptors, Prostaglandin E, EP4 Subtype / Q000378:metabolism*; D015398:Signal Transduction; D015854:Up-Regulation
chemical_list: C115163:CREB1 protein, human; D017362:Cyclic AMP Response Element-Binding Protein; C000715470:MAS1 protein, human; D000090063:Proto-Oncogene Mas; D016271:Proto-Oncogene Proteins c-myc; D012333:RNA, Messenger; D058309:Receptors, Prostaglandin E, EP4 Subtype; D000242:Cyclic AMP; D017868:Cyclic AMP-Dependent Protein Kinases; D000262:Adenylyl Cyclases; D015232:Dinoprostone