title: ViscumTT induces apoptosis and alters IAP expression in osteosarcoma in vitro and has synergistic action when combined with different chemotherapeutic drugs.
abstract: BACKGROUND
  Osteosarcoma is the most common bone tumor and is associated with a poor prognosis. Conventional therapies, surgery and chemotherapy, are still the standard but soon reach their limits. New therapeutic approaches are therefore needed. Conventional aqueous mistletoe extracts from the European mistletoe (Viscum album L.) are used in complementary cancer treatment. These commercial extracts are water-based and do not include water-insoluble compounds such as triterpenic acids. However, both hydrophilic and hydrophobic triterpenic acids possess anti-cancer properties. In this study, a whole mistletoe extract viscumTT re-created by combining an aqueous extract (viscum) and a triterpene extract (TT) was tested for its anti-cancer potential in osteosarcoma.
  
  
  METHODS
  Two osteosarcoma cell lines were treated with three different mistletoe extracts viscum, TT and viscumTT to compare their apoptotic potential. For this purpose, annexin/PI staining and caspase-3, -8 and -9 activity were investigated by flow cytometry. To determine the mechanism of action, alterations in expression of inhibitors of apoptosis (IAPs) were detected by western blot. Apoptosis induction by co-treatment of viscum, TT and viscumTT with doxorubicin, etoposide and ifosfamide was examined by flow cytometry.
  
  
  RESULTS
  In vitro as well as ex vivo, the whole mistletoe extract viscumTT led to strong inhibition of proliferation and synergistic apoptosis induction in osteosarcoma cells. In the investigations of mechanism of action, inhibitors of apoptosis such as XIAP, BIRC5 and CLSPN showed a clear down-regulation after viscumTT treatment. In addition, co-treatment with doxorubicin, etoposide and ifosfamide further enhanced apoptosis induction, also synergistically.
  
  
  CONCLUSIONS
  ViscumTT treatment results in synergistic apoptosis induction in osteosarcoma cells in vitro and ex vivo. Additionally, conventional standard chemotherapeutic drugs such as doxorubicin, etoposide and ifosfamide were able to dramatically enhance apoptosis induction. These results promise a high potential of viscumTT as an additional adjuvant therapy approach for osteosarcoma.
authors.affiliation: Department of Pediatric Oncology/Hematology, Otto-Heubner-Centre for Pediatric and Adolescent Medicine (OHC), Charitém, Universitätsmedizin, Augustenburger Platz 1, 13353, Berlin, Germany.
authors.forename: Susann
authors.initials: S
authors.lastname: Kleinsimon
authors.affiliation: Department of Pediatric Oncology/Hematology, Otto-Heubner-Centre for Pediatric and Adolescent Medicine (OHC), Charitém, Universitätsmedizin, Augustenburger Platz 1, 13353, Berlin, Germany.
authors.forename: Gwenda
authors.initials: G
authors.lastname: Kauczor
authors.affiliation: Birken AG, Streiflingsweg 11, 75223, Niefern-Öschelbronn, Germany.
authors.forename: Sebastian
authors.initials: S
authors.lastname: Jaeger
authors.affiliation: Department of Pediatric Oncology/Hematology, Otto-Heubner-Centre for Pediatric and Adolescent Medicine (OHC), Charitém, Universitätsmedizin, Augustenburger Platz 1, 13353, Berlin, Germany.
authors.forename: Angelika
authors.initials: A
authors.lastname: Eggert
authors.affiliation: Department of Pediatric Oncology/Hematology, Otto-Heubner-Centre for Pediatric and Adolescent Medicine (OHC), Charitém, Universitätsmedizin, Augustenburger Platz 1, 13353, Berlin, Germany. georg.seifert@charite.de.
authors.forename: Georg
authors.initials: G
authors.lastname: Seifert
authors.affiliation: Department of Pediatric Oncology/Hematology, Otto-Heubner-Centre for Pediatric and Adolescent Medicine (OHC), Charitém, Universitätsmedizin, Augustenburger Platz 1, 13353, Berlin, Germany.
authors.forename: Catharina
authors.initials: C
authors.lastname: Delebinski
mesh_terms: D000970:Antineoplastic Agents / Q000008:administration & dosage*; D017209:Apoptosis / Q000187:drug effects*; D049109:Cell Proliferation / Q000187:drug effects; D002648:Child; D004317:Doxorubicin / Q000008:administration & dosage; D004357:Drug Synergism; D004359:Drug Therapy, Combination; D005047:Etoposide / Q000008:administration & dosage; D006801:Humans; D051034:Inhibitor of Apoptosis Proteins / Q000235:genetics* / Q000378:metabolism; D008297:Male; D012516:Osteosarcoma / Q000188:drug therapy* / Q000235:genetics / Q000378:metabolism / Q000503:physiopathology; D010936:Plant Extracts / Q000008:administration & dosage*; D000077022:Survivin; D014315:Triterpenes / Q000008:administration & dosage*; D014407:Tumor Cells, Cultured; D028182:Viscum album / Q000737:chemistry*; D051636:X-Linked Inhibitor of Apoptosis Protein / Q000235:genetics / Q000378:metabolism
chemical_list: D000970:Antineoplastic Agents; C107489:BIRC5 protein, human; D051034:Inhibitor of Apoptosis Proteins; D010936:Plant Extracts; D000077022:Survivin; D014315:Triterpenes; D051636:X-Linked Inhibitor of Apoptosis Protein; C496866:XIAP protein, human; D005047:Etoposide; D004317:Doxorubicin
keywords: Apoptosis; Chemotherapeutic drugs; Mistletoe; Osteosarcoma; Triterpenic acids; Viscum album L