title: Effects of P-glycoprotein modulation on the chemotherapy of xenotransplanted human hepatoblastoma.
abstract: Multidrug resistance (MDR) contributes to limited treatment results in human hepatoblastoma (HB). The MDR1 gene and its product P-glycoprotein (P-gP) has been identified as important factor in this development. In other tumors, P-gP modulation leads to a restored chemosensitivity of the cells. The aim of this study was to analyze the P-gP-modulating effects of PSC 833, a cyclosporine derivate, and verapamil on the chemotherapy of HB in vivo. HB from 2 patients were transplanted subcutaneously into nude mice NMRI (nu/nu). Animals were divided into 7 groups: Group 1 (Control); Group 2 (CDDP); Group 3 (DOXO); Group 4 (DOXO + verapamil); Group 5 (DOXO + PSC 833); Group 6 (CDDP + verapamil); and Group 7 (CDDP + PSC 833). If DOXO was administered (regardless of the combination), the dose was two times 60 mg/m2. If CDDP was administered, the dose was two times 27 mg/m2. When the chemosensitizers were administered, the doses for PSC 833 and for verapamil were four times 5 mg/kg body-weight. In the combined treatment groups the chemosensitizers were given ten minutes prior to CDDP and DOXO. Tumor volume developments and a-fetoprotein (AFP) alterations were assessed. Relative expression levels of the MDR1 gene after treatment were determined using a semiquantitative rT-PCR approach. In a mixed HB, both chemosensitizers combined with DOXO or CDDP produced a significant reduction of tumor growth (p = .0001-.00063) and AFP levels (p = .0006-.0128) compared to tumors treated with DOXO or CDDP only. Treatment results were identical to those in a less differentiated pure embryonal HB, but only in one case (DOXO + PSC 833, p = .031) significant. The chemosensitizers had no influence on the MDR1 gene expression. MDR1 modulators improve the efficiency of DOXO and CDDP treatment in xenotransplanted HB. They do not induce a further increase of drug resistance in the tumors. The data provide evidence that chemosensitizers might improve treatment results in patients with advanced or relapsed HB.
authors: Department of Pediatric Surgery, University of Tübingen, Tübingen, Germany. Steven.Warman@med.uni-tuebingen.de
authors: Steven W
authors: SW
authors: Warmann
authors: Heike
authors: H
authors: Heitmann
authors: Birgit
authors: B
authors: Teichmann
authors: Klaus Friedrich
authors: KF
authors: Gratz
authors: Peter
authors: P
authors: Ruck
authors: Mona
authors: M
authors: Hunger
authors: Jörg
authors: J
authors: Fuchs
mesh_terms: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000187:drug effects / Q000378:metabolism*; D000818:Animals; D000971:Antineoplastic Combined Chemotherapy Protocols / Q000494:pharmacology / Q000627:therapeutic use*; D001835:Body Weight / Q000187:drug effects; D045744:Cell Line, Tumor; D002648:Child; D002675:Child, Preschool; D004195:Disease Models, Animal; D018432:Drug Resistance, Multiple; D019008:Drug Resistance, Neoplasm; D015972:Gene Expression Regulation, Neoplastic; D019450:Genes, MDR / Q000187:drug effects / Q000235:genetics; D018197:Hepatoblastoma / Q000188:drug therapy* / Q000648:ultrastructure; D006801:Humans; D008113:Liver Neoplasms / Q000188:drug therapy* / Q000648:ultrastructure; D051379:Mice; D008819:Mice, Nude; D009368:Neoplasm Transplantation; D023041:Xenograft Model Antitumor Assays
chemical_list: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1