title: Electric pulses used in electrochemotherapy and electrogene therapy do not significantly change the expression profile of genes involved in the development of cancer in malignant melanoma cells.
abstract: BACKGROUND
  Electroporation is a versatile method for in vitro or in vivo delivery of different molecules into cells. However, no study so far has analysed the effects of electric pulses used in electrochemotherapy (ECT pulses) or electric pulses used in electrogene therapy (EGT pulses) on malignant cells. We studied the effect of ECT and EGT pulses on human malignant melanoma cells in vitro in order to understand and predict the possible effect of electric pulses on gene expression and their possible effect on cell behaviour.
  
  
  METHODS
  We used microarrays with 2698 different oligonucleotides to obtain the expression profile of genes involved in apoptosis and cancer development in a malignant melanoma cell line (SK-MEL28) exposed to ECT pulses and EGT pulses.
  
  
  RESULTS
  Cells exposed to ECT pulses showed a 68.8% average survival rate, while cells exposed to EGT pulses showed a 31.4% average survival rate. Only seven common genes were found differentially expressed in cells 16 h after exposure to ECT and EGT pulses. We found that ECT and EGT pulses induce an HSP70 stress response mechanism, repress histone protein H4, a major protein involved in chromatin assembly, and down-regulate components involved in protein synthesis.
  
  
  CONCLUSIONS
  Our results show that electroporation does not significantly change the expression profile of major tumour suppressor genes or oncogenes of the cell cycle. Moreover, electroporation also does not changes the expression of genes involved in the stability of DNA, supporting current evidence that electroporation is a safe method that does not promote tumorigenesis. However, in spite of being considered an isothermal method, it does to some extent induce stress, which resulted in the expression of the environmental stress response mechanism, HSP70.
authors.affiliation: Department of Experimental Oncology, Institute of Oncology Ljubljana, Zaloska cesta 2, Ljubljana, Slovenia. vid.mlakar@mf.uni-lj.si
authors.forename: Vid
authors.initials: V
authors.lastname: Mlakar
authors.forename: Vesna
authors.initials: V
authors.lastname: Todorovic
authors.forename: Maja
authors.initials: M
authors.lastname: Cemazar
authors.forename: Damjan
authors.initials: D
authors.lastname: Glavac
authors.forename: Gregor
authors.initials: G
authors.lastname: Sersa
mesh_terms: D045744:Cell Line, Tumor; D002470:Cell Survival; D003131:Combined Modality Therapy; D053672:Electrochemotherapy / Q000295:instrumentation; D018274:Electroporation / Q000295:instrumentation; D015972:Gene Expression Regulation, Neoplastic; D015316:Genetic Therapy; D018840:HSP70 Heat-Shock Proteins / Q000235:genetics / Q000378:metabolism; D006657:Histones / Q000235:genetics / Q000378:metabolism; D006801:Humans; D008545:Melanoma / Q000235:genetics* / Q000378:metabolism / Q000503:physiopathology / Q000628:therapy*
chemical_list: D018840:HSP70 Heat-Shock Proteins; D006657:Histones