title: Hypoxia and Transforming Growth Factor β Cooperate to Induce Fibulin-5 Expression in Pancreatic Cancer.
abstract: The deposition of extracellular matrix (ECM) is a defining feature of pancreatic ductal adenocarcinoma (PDA), where ECM signaling can promote cancer cell survival and epithelial plasticity programs. However, ECM signaling can also limit PDA tumor growth by producing cytotoxic levels of reactive oxygen species. For example, excess fibronectin stimulation of α5β1 integrin on stromal cells in PDA results in reduced angiogenesis and increased tumor cell apoptosis because of oxidative stress. Fibulin-5 (Fbln5) is a matricellular protein that blocks fibronectin-integrin interaction and thus directly limits ECM-driven reactive oxygen species production and supports PDA progression. Compared with normal pancreatic tissue, Fbln5 is expressed abundantly in the stroma of PDA; however, the mechanisms underlying the stimulation of Fbln5 expression in PDA are undefined. Using in vitro and in vivo approaches, we report that hypoxia triggers Fbln5 expression in a TGF-β- and PI3K-dependent manner. Pharmacologic inhibition of TGF-β receptor, PI3K, or protein kinase B (AKT) was found to block hypoxia-induced Fbln5 expression in mouse embryonic fibroblasts and 3T3 fibroblasts. Moreover, tumor-associated fibroblasts from mouse PDA were also responsive to TGF-β receptor and PI3K/AKT inhibition with regard to suppression of Fbln5. In genetically engineered mouse models of PDA, therapy-induced hypoxia elevated Fbln5 expression, whereas pharmacologic inhibition of TGF-β signaling reduced Fbln5 expression. These findings offer insight into the signaling axis that induces Fbln5 expression in PDA and a potential strategy to block its production.
authors.affiliation: From the Hamon Center for Therapeutic Oncology Research, Cancer Biology Graduate Program.
authors.forename: Mary
authors.initials: M
authors.lastname: Topalovski
authors.affiliation: Division of Surgical Oncology, Department of Surgery, and.
authors.forename: Michelle
authors.initials: M
authors.lastname: Hagopian
authors.affiliation: From the Hamon Center for Therapeutic Oncology Research.
authors.forename: Miao
authors.initials: M
authors.lastname: Wang
authors.affiliation: From the Hamon Center for Therapeutic Oncology Research, Cancer Biology Graduate Program, Division of Surgical Oncology, Department of Surgery, and Department of Pharmacology, University of Texas Southwestern Medical Center, Dallas, Texas 75390-8593 rolf.brekken@utsouthwestern.edu.
authors.forename: Rolf A
authors.initials: RA
authors.lastname: Brekken
mesh_terms: D000818:Animals; D021441:Carcinoma, Pancreatic Ductal / Q000378:metabolism* / Q000473:pathology / Q000628:therapy; D015687:Cell Hypoxia; D005109:Extracellular Matrix / Q000378:metabolism / Q000473:pathology; D016326:Extracellular Matrix Proteins / Q000096:biosynthesis*; D015972:Gene Expression Regulation, Neoplastic; D039081:Integrin alpha5beta1 / Q000378:metabolism; D051379:Mice; D008817:Mice, Mutant Strains; D041681:NIH 3T3 Cells; D009374:Neoplasms, Experimental / Q000378:metabolism* / Q000473:pathology / Q000628:therapy; D010190:Pancreatic Neoplasms / Q000378:metabolism* / Q000473:pathology / Q000628:therapy; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D011994:Recombinant Proteins / Q000096:biosynthesis*; D015398:Signal Transduction; D016212:Transforming Growth Factor beta / Q000378:metabolism*
chemical_list: D016326:Extracellular Matrix Proteins; C120769:Fbln5 protein, mouse; D039081:Integrin alpha5beta1; D011994:Recombinant Proteins; D016212:Transforming Growth Factor beta; D019869:Phosphatidylinositol 3-Kinases; D051057:Proto-Oncogene Proteins c-akt
keywords: Akt PKB; TGF-β; extracellular matrix; fibulin-5; hypoxia; pancreatic cancer