title: Autophagy and cell death signaling following dietary sulforaphane act independently of each other and require oxidative stress in pancreatic cancer.
abstract: The broccoli isothiocyanate, sulforaphane (SFN), was recently identified as being capable of eliminating highly therapy-resistant pancreatic carcinoma (PC) cells without inducing toxic side effects. While SFN has been shown to stimulate autophagy or 'self-eating', it is unclear whether this catabolic process is a pro- or anti-tumorigenic response. To investigate the role of autophagy in SFN-induced cell death, established PC cell lines were treated with SFN, and the induction of autophagy was evaluated by detecting the abundance of autophagic vesicles by electron microscopy, the increase in converted LC3-II by Western blot analysis and the autophagosome puncta of GFP-LC3 by immunofluorescence. SFN-induced autophagy was suppressed by the autophagy inhibitor chloroquine, while the autophagy inducer rapamycin did not further enhance autophagy in PC cells. Importantly, neither modulator altered SFN cytotoxicity, suggesting that SFN-induced autophagy and cell death act independently of each other. In contrast, the antioxidant N-acetyl-cysteine sustained cell viability and prevented autophagy induction after SFN exposure, indicating that both signaling pathways depend on reactive oxygen species (ROS). Our studies provide a valuable new mechanistic insight into the SFN-induced elimination of PC cells and suggest that an SFN-enriched diet potentially enhances ROS-releasing chemotherapeutic agents.
authors.affiliation: Department of General, Visceral and Transplantation Surgery, University Clinic Heidelberg, Heidelberg, Germany.
authors.forename: Patrick
authors.initials: P
authors.lastname: Naumann
authors.forename: Franco
authors.initials: F
authors.lastname: Fortunato
authors.forename: Hanswalter
authors.initials: H
authors.lastname: Zentgraf
authors.forename: Markus W
authors.initials: MW
authors.lastname: Büchler
authors.forename: Ingrid
authors.initials: I
authors.lastname: Herr
authors.forename: Jens
authors.initials: J
authors.lastname: Werner
mesh_terms: D016588:Anticarcinogenic Agents / Q000378:metabolism / Q000494:pharmacology*; D001343:Autophagy / Q000187:drug effects*; D045744:Cell Line, Tumor; D006801:Humans; D017879:Isothiocyanates; D018384:Oxidative Stress / Q000502:physiology*; D010190:Pancreatic Neoplasms / Q000473:pathology* / Q000503:physiopathology; D017382:Reactive Oxygen Species / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects*; D013454:Sulfoxides; D013861:Thiocyanates / Q000378:metabolism / Q000494:pharmacology*
chemical_list: D016588:Anticarcinogenic Agents; D017879:Isothiocyanates; D017382:Reactive Oxygen Species; D013454:Sulfoxides; D013861:Thiocyanates; C016766:sulforaphane