title: Effects of standard chemotherapy on tumor growth and regulation of multidrug resistance genes and proteins in childhood rhabdomyosarcoma.
abstract: The prognosis of rhabdomyosarcoma (RMS) in advanced stages is still sobering. Therapy is limited due to local tumor recurrence, development of metastases and multidrug resistance. The aim of this study was to investigate the development of multidrug resistance in cell lines and in xenografts of alveolar and embryonal RMS treated according to the German Soft Tissue Sarcoma Study (CWS). Alveolar and embryonal RMS cell lines were treated with Vincristine, Topotecan, Carboplatin, Actinomycin D, or Ifosfamide. Expression levels of resistance-associated genes were assessed using Real time-PCR. Nude mice (NMRI nu/nu, n = 10 per group) underwent xenotransplantation of human embryonal or alveolar RMS. Animals were treated with standard chemotherapeutic drugs Vincristine, Topotecan, Carboplatin, Actinomycin D, or Ifosfamide according to treatment schedules of the CWS-study. Tumor sizes were measured and relative tumor volumes were calculated. Animals were sacrificed after 20 days and standard histology, Real-time-PCR for MDR1-, MRP-, LRP- and MDM2-gene as well as immunohistochemistry for MDR1-, LRP-, and MRP-protein were performed. In the cell lines, an up-regulation of MDR-1 gene was found in alveolar rhabdomyosarcoma. In embryonal rhabdomyosarcoma, an up-regulation of LRP and MRP was found. Standard chemotherapy of alveolar rhabdomyosarcoma resulted in a significant reduction of tumor growth (P < 0.05) in all groups. In embryonal rhabdomyosarcoma strongest effects were found after treatment with Ifosfamide, Vincristine and Carboplatin (P < 0.05). RT-PCR revealed a MDR1-dependent mechanism in alveolar rhabdomyosarcoma. In embryonal rhabdomyosarcoma, MDR1 occurred to a lower degree. Immunohistochemistry revealed correlating expression levels of multidrug resistance-associated proteins. The use of established chemotherapy on human RMS in vivo had strong effects on xenografts compared to their controls. In all cases, there was only a reduction of tumor growth, but not a complete eradication of the tumors. Chemotherapy seemed to upregulate the expression of resistance-associated genes in vitro and in vivo. The mechanism of multidrug resistance depends on the tumor subtype. Therefore, further investigations will be required to evaluate multidrug resistance in patients and to investigate new modalities for a reversal of multidrug resistance.
authors.affiliation: Department of Pediatric Surgery, University Children's Hospital, Hoppe-Seyler-Strasse 1, 72076 Tuebingen, Germany. guido.seitz@med.uni-tuebingen.de
authors.forename: Guido
authors.initials: G
authors.lastname: Seitz
authors.forename: Steven W
authors.initials: SW
authors.lastname: Warmann
authors.forename: Christian O
authors.initials: CO
authors.lastname: Vokuhl
authors.forename: Heike
authors.initials: H
authors.lastname: Heitmann
authors.forename: Claudia
authors.initials: C
authors.lastname: Treuner
authors.forename: Ivo
authors.initials: I
authors.lastname: Leuschner
authors.forename: Jörg
authors.initials: J
authors.lastname: Fuchs
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D000970:Antineoplastic Agents / Q000008:administration & dosage / Q000627:therapeutic use; D004195:Disease Models, Animal; D004334:Drug Administration Schedule; D019008:Drug Resistance, Neoplasm / Q000187:drug effects* / Q000235:genetics; D005260:Female; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects* / Q000235:genetics; D019450:Genes, MDR / Q000235:genetics*; D006801:Humans; D007150:Immunohistochemistry / Q000379:methods; D051379:Mice; D008819:Mice, Nude; D027425:ATP-Binding Cassette, Sub-Family C Proteins / Q000187:drug effects* / Q000378:metabolism; D009363:Neoplasm Proteins / Q000187:drug effects; D016133:Polymerase Chain Reaction / Q000379:methods; D018232:Rhabdomyosarcoma, Alveolar / Q000188:drug therapy* / Q000235:genetics / Q000473:pathology; D018233:Rhabdomyosarcoma, Embryonal / Q000188:drug therapy* / Q000235:genetics / Q000473:pathology; D012983:Soft Tissue Neoplasms / Q000188:drug therapy* / Q000235:genetics / Q000473:pathology; D023041:Xenograft Model Antitumor Assays
chemical_list: D000970:Antineoplastic Agents; D027425:ATP-Binding Cassette, Sub-Family C Proteins; D009363:Neoplasm Proteins