title: Liposome-based DNA carriers may induce cellular stress response and change gene expression pattern in transfected cells.
abstract: BACKGROUND
  During functional studies on the rat stress-inducible Hspa1b (hsp70.1) gene we noticed that some liposome-based DNA carriers, which are used for transfection, induce its promoter activity. This observation concerned commercial liposome formulations (LA), Lipofectin and Lipofectamine 2000. This work was aimed to understand better the mechanism of this phenomenon and its potential biological and practical consequences.
  
  
  RESULTS
  We found that a reporter gene driven by Hspa1b promoter is activated both in the case of transient transfections and in the stably transfected cells treated with LA. Using several deletion clones containing different fragments of Hspa1b promoter, we found that the regulatory elements responsible for most efficient LA-driven inducibility were located between nucleotides -269 and +85, relative to the transcription start site. Further studies showed that the induction mechanism was independent of the classical HSE-HSF interaction that is responsible for gene activation during heat stress. Using DNA microarrays we also detected significant activation of the endogenous Hspa1b gene in cells treated with Lipofectamine 2000. Several other stress genes were also induced, along with numerous genes involved in cellular metabolism, cell cycle control and pro-apoptotic pathways.
  
  
  CONCLUSIONS
  Our observations suggest that i) some cationic liposomes may not be suitable for functional studies on hsp promoters, ii) lipofection may cause unintended changes in global gene expression in the transfected cells.
authors.affiliation: Center for Translational Research and Molecular Biology of Cancer, Maria Skłodowska-Curie Memorial Center and Institute of Oncology, Gliwice Branch, ul, Wybrzeże Armii Krajowej 15, 44-101 Gliwice, Poland.
authors.forename: Anna
authors.initials: A
authors.lastname: Fiszer-Kierzkowska
authors.forename: Natalia
authors.initials: N
authors.lastname: Vydra
authors.forename: Aleksandra
authors.initials: A
authors.lastname: Wysocka-Wycisk
authors.forename: Zuzana
authors.initials: Z
authors.lastname: Kronekova
authors.forename: Michał
authors.initials: M
authors.lastname: Jarząb
authors.forename: Katarzyna Marta
authors.initials: KM
authors.lastname: Lisowska
authors.forename: Zdzisław
authors.initials: Z
authors.lastname: Krawczyk
mesh_terms: D000818:Animals; D045744:Cell Line, Tumor; D004247:DNA / Q000008:administration & dosage*; D015870:Gene Expression; D018840:HSP70 Heat-Shock Proteins / Q000235:genetics*; D008055:Lipids / Q000494:pharmacology*; D008081:Liposomes / Q000378:metabolism*; D051379:Mice; D010714:Phosphatidylethanolamines / Q000378:metabolism*; D014158:Transcription, Genetic / Q000187:drug effects; D014162:Transfection
chemical_list: D018840:HSP70 Heat-Shock Proteins; C490435:Hspa2 protein, rat; D008055:Lipids; C086724:Lipofectamine; D008081:Liposomes; D010714:Phosphatidylethanolamines; C020888:1,2-dielaidoylphosphatidylethanolamine; D004247:DNA