title: Negative control of TRAIL-R1 signaling by transforming growth factor β1 in pancreatic tumor cells involves Smad-dependent down regulation of TRAIL-R1.
abstract: Pancreatic ductal adenocarcinoma (PDAC) is characterized by both, overexpression of transforming growth factor (TGF)β and resistance of the tumor cells to many apoptosis-inducing stimuli. The latter negatively impacts the outcome of therapeutic efforts and represents one important mechanism which tumor cells utilize to escape the immune surveillance. Since TGFβ acts as a tumor promoter in advanced tumor stages and suppression of apoptosis is a known driver of tumor progression, it is possible that TGFβ functions as a crucial determinant of tumor cell sensitivity to apoptosis in PDAC. Here, we have studied the impact of TGFβ on TNF-related apoptosis inducing ligand (TRAIL)-induced signaling in PDAC cells. In TGFβ-responsive Panc1 and Colo357 cells, TGFβ1 reduced total and plasma membrane-associated levels of TRAIL-R1 but not those of TRAIL-R2. Consistent with the known predominant role of TRAIL-R1 in TRAIL-mediated signaling in PDAC, TGFβ1 inhibited TRAIL-induced DISC formation and apoptosis as well as phosphorylation of MAPKs and IκBα. Similarly, it also reduced signaling of TRAIL-R1 following its specific activation with an agonistic antibody. In contrast, specific TRAIL-R2 signaling remained unchanged. The TGFβ1 effect on TRAIL-R1 expression was mimicked by ectopic expression of a kinase-active version of the TGFβ type I receptor ALK5 (ALK5-T204D) but not by ALK5 double mutant lacking the ability to phosphorylate Smad proteins (RImL45-T204D). Moreover, TGFβ regulation of TRAIL-R1 was absent in two PDAC cell lines lacking the Smad4 gene DPC4 and siRNA-mediated silencing of Smad4 in Smad4-positive Panc1 cells abolished the TGFβ-mediated decrease in TRAIL-R1 expression, together showing that ALK5/Smad4 signaling is crucial for TGFβ regulation of TRAIL-R1 expression. Our results suggest a novel tumor-promoting function of TGFβ1. By downregulating TRAIL-R1, TGFβ1 may not only promote tumor escape from immune surveillance but also negatively impact on TRAIL- or TRAIL-R1-based therapy regimens for treatment of PDAC.
authors: Institute for Experimental Cancer Research, University of Kiel, D-24105 Kiel, Germany.
authors: David I
authors: DI
authors: Radke
authors: First Department of Medicine, UKSH and University of Lübeck, D-23538 Lübeck, Germany.
authors: Hendrik
authors: H
authors: Ungefroren
authors: Institute for Experimental Cancer Research, University of Kiel, D-24105 Kiel, Germany.
authors: Ole
authors: O
authors: Helm
authors: Institute of Immunology, University of Kiel, D-24105 Kiel, Germany.
authors: Susann
authors: S
authors: Voigt
authors: Institute for Experimental Cancer Research, University of Kiel, D-24105 Kiel, Germany.
authors: Gökhan
authors: G
authors: Alp
authors: Institute for Experimental Cancer Research, University of Kiel, D-24105 Kiel, Germany.
authors: Hendrik
authors: H
authors: Braun
authors: Institute for Experimental Cancer Research, University of Kiel, D-24105 Kiel, Germany.
authors: Sebastian
authors: S
authors: Hübner
authors: Institute for Experimental Cancer Research, University of Kiel, D-24105 Kiel, Germany.
authors: Janine
authors: J
authors: Dilchert
authors: Institute for Experimental Cancer Research, University of Kiel, D-24105 Kiel, Germany.
authors: Susanne
authors: S
authors: Sebens
authors: Institute of Immunology, University of Kiel, D-24105 Kiel, Germany.
authors: Dieter
authors: D
authors: Adam
authors: Institute for Experimental Cancer Research, University of Kiel, D-24105 Kiel, Germany.
authors: Holger
authors: H
authors: Kalthoff
authors: Institute for Experimental Cancer Research, University of Kiel, D-24105 Kiel, Germany; Clinic for General Surgery, Visceral, Thoracic, Transplantation and Pediatric Surgery, University Hospital Schleswig-Holstein, Campus Kiel, D-24105 Kiel, Germany. Electronic address: atrauzold@email.uni-kiel.de.
authors: Anna
authors: A
authors: Trauzold
mesh_terms: D000230:Adenocarcinoma / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D000918:Antibody Specificity / Q000187:drug effects; D017209:Apoptosis / Q000187:drug effects / Q000235:genetics; D021441:Carcinoma, Pancreatic Ductal / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D045744:Cell Line, Tumor; D015536:Down-Regulation / Q000187:drug effects* / Q000235:genetics; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D006801:Humans; D009154:Mutation / Q000235:genetics; D010190:Pancreatic Neoplasms / Q000378:metabolism* / Q000473:pathology*; D011485:Protein Binding / Q000187:drug effects / Q000235:genetics; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D000077293:Receptor, Transforming Growth Factor-beta Type I; D053220:Receptors, TNF-Related Apoptosis-Inducing Ligand / Q000235:genetics / Q000378:metabolism*; D018125:Receptors, Transforming Growth Factor beta / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects* / Q000235:genetics; D051901:Smad4 Protein / Q000378:metabolism*; D053773:Transforming Growth Factor beta1 / Q000494:pharmacology*
chemical_list: D053220:Receptors, TNF-Related Apoptosis-Inducing Ligand; D018125:Receptors, Transforming Growth Factor beta; C497796:SMAD4 protein, human; D051901:Smad4 Protein; D053773:Transforming Growth Factor beta1; D017346:Protein Serine-Threonine Kinases; D000077293:Receptor, Transforming Growth Factor-beta Type I; C000625841:TGFBR1 protein, human
keywords: Apoptosis; Non-canonical TRAIL receptor signaling; Smad4; TGFβ; TRAIL-R1