title: Low-power photodynamic therapy induces survival signaling in perihilar cholangiocarcinoma cells.
abstract: BACKGROUND
  Photodynamic therapy (PDT) of solid cancers comprises the administration of a photosensitizer followed by illumination of the photosensitizer-replete tumor with laser light. This induces a state of local oxidative stress, culminating in the destruction of tumor tissue and microvasculature and induction of an anti-tumor immune response. However, some tumor types, including perihilar cholangiocarcinoma, are relatively refractory to PDT, which may be attributable to the activation of survival pathways in tumor cells following PDT (i.e., activator protein 1 (AP-1)-, nuclear factor of kappa light polypeptide gene enhancer in B-cells (NF-κB)-, hypoxia-inducible factor 1-alpha (HIF-1α)-, nuclear factor (erythroid-derived 2)-like 2 (NFE2L2)-, and unfolded protein response-mediated pathways).
  
  
  METHODS
  To assess the activation of survival pathways after PDT, human perihilar cholangiocarcinoma (SK-ChA-1) cells were subjected to PDT with zinc phthalocyanine (ZnPC)-encapsulating liposomes. Following 30-minute incubation with liposomes, the cells were either left untreated or treated at low (50 mW) or high (500 mW) laser power (cumulative light dose of 15 J/cm(2)). Cells were harvested 90 min post-PDT and whole genome expression analysis was performed using Illumina HumanHT-12 v4 expression beadchips. The data were interpreted in the context of the survival pathways. In addition, the safety of ZnPC-encapsulating liposomes was tested both in vitro and in vivo.
  
  
  RESULTS
  PDT-treated SK-ChA-1 cells exhibited activation of the hypoxia-induced stress response via HIF-1α and initiation of the pro-inflammatory response via NF-кB. PDT at low laser power in particular caused extensive survival signaling, as evidenced by the significant upregulation of HIF-1- (P < 0.001) and NF-кB-related (P < 0.001) genes. Low-power PDT was less lethal to SK-ChA-1 cells 90 min post-PDT, confirmed by annexin V/propidium iodide staining. In vitro toxicogenomics and toxicological testing in chicken embryos and mice revealed that the ZnPC-encapsulating liposomes are non-toxic.
  
  
  CONCLUSIONS
  PDT-treated perihilar cholangiocarcinoma cells exhibit extensive survival signaling that may translate to a suboptimal therapeutic response and possibly tumor recurrence. These findings encourage the development of photosensitizer delivery systems with co-encapsulated inhibitors of survival pathways.
authors.affiliation: Department of Experimental Surgery, Academic Medical Center, University of Amsterdam, Meibergdreef 9, 1105, AZ, Amsterdam, The Netherlands. r.weijer@amc.uva.nl.
authors.forename: Ruud
authors.initials: R
authors.lastname: Weijer
authors.affiliation: Department of Experimental Surgery, Academic Medical Center, University of Amsterdam, Meibergdreef 9, 1105, AZ, Amsterdam, The Netherlands. mbroekgaarden@mgh.harvard.edu.
authors.forename: Mans
authors.initials: M
authors.lastname: Broekgaarden
authors.affiliation: Department of Experimental Surgery, Academic Medical Center, University of Amsterdam, Meibergdreef 9, 1105, AZ, Amsterdam, The Netherlands. r.f.vangolen@amc.uva.nl.
authors.forename: Rowan F
authors.initials: RF
authors.lastname: van Golen
authors.affiliation: Department of Experimental Surgery, Academic Medical Center, University of Amsterdam, Meibergdreef 9, 1105, AZ, Amsterdam, The Netherlands. e.b.bulle@amc.uva.nl.
authors.forename: Esther
authors.initials: E
authors.lastname: Bulle
authors.affiliation: Department of Experimental Surgery, Academic Medical Center, University of Amsterdam, Meibergdreef 9, 1105, AZ, Amsterdam, The Netherlands. e.a.nieuwenhuis@amc.uva.nl.
authors.forename: Esther
authors.initials: E
authors.lastname: Nieuwenhuis
authors.affiliation: Bioinformatics Laboratory, Academic Medical Center, University of Amsterdam, Meibergdreef 9, 1105, AZ, Amsterdam, The Netherlands. a.jongejan@amc.uva.nl.
authors.forename: Aldo
authors.initials: A
authors.lastname: Jongejan
authors.affiliation: Bioinformatics Laboratory, Academic Medical Center, University of Amsterdam, Meibergdreef 9, 1105, AZ, Amsterdam, The Netherlands. p.d.moerland@amc.uva.nl.
authors.forename: Perry D
authors.initials: PD
authors.lastname: Moerland
authors.affiliation: Bioinformatics Laboratory, Academic Medical Center, University of Amsterdam, Meibergdreef 9, 1105, AZ, Amsterdam, The Netherlands. a.h.vankampen@amc.uva.nl.
authors.forename: Antoine H C
authors.initials: AH
authors.lastname: van Kampen
authors.affiliation: Department of Experimental Surgery, Academic Medical Center, University of Amsterdam, Meibergdreef 9, 1105, AZ, Amsterdam, The Netherlands. t.m.vangulik@amc.uva.nl.
authors.forename: Thomas M
authors.initials: TM
authors.lastname: van Gulik
authors.affiliation: Department of Experimental Surgery, Academic Medical Center, University of Amsterdam, Meibergdreef 9, 1105, AZ, Amsterdam, The Netherlands. m.heger@amc.uva.nl.
authors.forename: Michal
authors.initials: M
authors.lastname: Heger
mesh_terms: D000818:Animals; D001650:Bile Duct Neoplasms / Q000378:metabolism / Q000503:physiopathology / Q000628:therapy*; D002470:Cell Survival; D020869:Gene Expression Profiling; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000235:genetics; D007211:Indoles / Q000494:pharmacology; D054833:Isoindoles; D018285:Klatskin Tumor / Q000378:metabolism / Q000503:physiopathology / Q000628:therapy*; D008081:Liposomes; D008297:Male; D051379:Mice; D009942:Organometallic Compounds / Q000494:pharmacology; D010778:Photochemotherapy; D017319:Photosensitizing Agents / Q000494:pharmacology; D015398:Signal Transduction; D015854:Up-Regulation; D017967:Zinc Compounds
chemical_list: D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D007211:Indoles; D054833:Isoindoles; D008081:Liposomes; D009942:Organometallic Compounds; D017319:Photosensitizing Agents; D017967:Zinc Compounds; C052159:Zn(II)-phthalocyanine