title: Combined enzyme/prodrug treatment by genetically engineered AT-MSC exerts synergy and inhibits growth of MDA-MB-231 induced lung metastases.
abstract: BACKGROUND
  Metastatic spread of tumor cells remains a serious problem in cancer treatment. Gene-directed enzyme/prodrug therapy mediated by tumor-homing genetically engineered mesenchymal stromal cells (MSC) represents a promising therapeutic modality for elimination of disseminated cells. Efficacy of gene-directed enzyme/prodrug therapy can be improved by combination of individual systems. We aimed to define the combination effect of two systems of gene therapy mediated by MSC, and evaluate the ability of systemically administered genetically engineered mesenchymal stromal cells to inhibit the growth of experimental metastases derived from human breast adenocarcinoma cells MDA-MB-231/EGFP.
  
  
  METHODS
  Human adipose tissue-derived mesenchymal stromal cells (AT-MSC) were retrovirally transduced with fusion yeast cytosine deaminase::uracil phosphoribosyltransferase (CD::UPRT) or with Herpes simplex virus thymidine kinase (HSVtk). Engineered MSC were cocultured with tumor cells in the presence of prodrugs 5-fluorocytosin (5-FC) and ganciclovir (GCV). Combination effect of these enzyme/prodrug approaches was calculated. SCID/bg mice bearing experimental lung metastases were treated with CD::UPRT-MSC, HSVtk-MSC or both in combination in the presence of respective prodrug(s). Treatment efficiency was evaluated by EGFP-positive cell detection by flow cytometry combined with real-time PCR quantification of human cells in mouse organs. Results were confirmed by histological and immunohistochemical examination.
  
  
  RESULTS
  We demonstrated various extent of synergy depending on tested cell line and experimental setup. The strongest synergism was observed on breast cancer-derived cell line MDA-MB-231/EGFP. Systemic administration of CD::UPRT-MSC and HSVtk-MSC in combination with 5-FC and GCV inhibited growth of MDA-MB-231 induced lung metastases.
  
  
  CONCLUSIONS
  Combined gene-directed enzyme/prodrug therapy mediated by MSC exerted synergic cytotoxic effect and resulted in high therapeutic efficacy in vivo.
authors.affiliation: Laboratory of Molecular Oncology, Cancer Research Institute of Slovak Academy of Sciences, Vlarska 7, Bratislava, 833 91, Slovakia. miroslava.matuskova@savba.sk.
authors.forename: Miroslava
authors.initials: M
authors.lastname: Matuskova
authors.affiliation: Laboratory of Molecular Oncology, Cancer Research Institute of Slovak Academy of Sciences, Vlarska 7, Bratislava, 833 91, Slovakia. zuzana.kozovska@savba.sk.
authors.forename: Zuzana
authors.initials: Z
authors.lastname: Kozovska
authors.affiliation: Laboratory of Molecular Oncology, Cancer Research Institute of Slovak Academy of Sciences, Vlarska 7, Bratislava, 833 91, Slovakia. lenka.baranovicova@savba.sk.
authors.forename: Lenka
authors.initials: L
authors.lastname: Toro
authors.affiliation: Laboratory of Molecular Oncology, Cancer Research Institute of Slovak Academy of Sciences, Vlarska 7, Bratislava, 833 91, Slovakia. erika.durinikova@savba.sk.
authors.forename: Erika
authors.initials: E
authors.lastname: Durinikova
authors.affiliation: Laboratory of Molecular Oncology, Cancer Research Institute of Slovak Academy of Sciences, Vlarska 7, Bratislava, 833 91, Slovakia. silvia.tyciakova@savba.sk.
authors.forename: Silvia
authors.initials: S
authors.lastname: Tyciakova
authors.affiliation: Institute of Pathological Anatomy, Faculty of Medicine, Comenius University, Sasinkova 4, Bratislava, 813 72, Slovakia. ciernaz@gmail.com.
authors.forename: Zuzana
authors.initials: Z
authors.lastname: Cierna
authors.affiliation: Laboratory of Molecular Oncology, Cancer Research Institute of Slovak Academy of Sciences, Vlarska 7, Bratislava, 833 91, Slovakia. roman.bohovic@savba.sk.
authors.forename: Roman
authors.initials: R
authors.lastname: Bohovic
authors.affiliation: Laboratory of Molecular Oncology, Cancer Research Institute of Slovak Academy of Sciences, Vlarska 7, Bratislava, 833 91, Slovakia. lucia.kucerova@savba.sk.
authors.forename: Lucia
authors.initials: L
authors.lastname: Kucerova
mesh_terms: D000818:Animals; D045744:Cell Line, Tumor; D004195:Disease Models, Animal; D015774:Ganciclovir / Q000494:pharmacology*; D015316:Genetic Therapy; D006801:Humans; D008175:Lung Neoplasms / Q000473:pathology* / Q000556:secondary / Q000628:therapy; D045164:Mesenchymal Stem Cell Transplantation; D059630:Mesenchymal Stem Cells / Q000378:metabolism*; D051379:Mice; D008979:Moloney murine leukemia virus / Q000235:genetics; D013937:Thymidine Kinase / Q000235:genetics*; D014161:Transduction, Genetic; D023041:Xenograft Model Antitumor Assays
chemical_list: D013937:Thymidine Kinase; D015774:Ganciclovir